WO2010113169A1 - A process for the preparation and use of pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas - Google Patents

A process for the preparation and use of pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas Download PDF

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WO2010113169A1
WO2010113169A1 PCT/IN2009/000753 IN2009000753W WO2010113169A1 WO 2010113169 A1 WO2010113169 A1 WO 2010113169A1 IN 2009000753 W IN2009000753 W IN 2009000753W WO 2010113169 A1 WO2010113169 A1 WO 2010113169A1
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carbon dioxide
adsorbent
adsorption
zsm
range
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PCT/IN2009/000753
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French (fr)
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Raksh Vir Jasra
Rajesh Shantilal Somani
Beena Tyagi
Sunil Adavanal Peter
Renjith Sasimohanan Pillai
Ulka Sharma
Prakash Dulhadinomal Hirani
Rabishankar Mukhopadhyay
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Council Of Scientific & Industrial Research
Ntpc Limited
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    • B01J20/16—Alumino-silicates
    • B01J20/18—Synthetic zeolitic molecular sieves
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    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
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    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
    • B01J20/3483—Regenerating or reactivating by thermal treatment not covered by groups B01J20/3441 - B01J20/3475, e.g. by heating or cooling
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    • B01J20/34—Regenerating or reactivating
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B01D2253/108—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2257/50—Carbon oxides
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/0462—Temperature swing adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/047—Pressure swing adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/047—Pressure swing adsorption
    • B01D53/0476—Vacuum pressure swing adsorption
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

  • the present invention relates to a process for the preparation and use of Pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas by selective adsorption of carbon dioxide from a gaseous mixture containing carbon dioxide in the range of 3 to 20 % by volume as in the case of power plant flue gas.
  • the present invention relates to the use of pentasil type zeolites, especially ZSM-5 having SiO 2 / Al 2 O 3 ratio in the range of 25- 900, as a carbon dioxide selective adsorbent for the separation of carbon dioxide from the flue gas of thermal power plants.
  • CO 2 emissions due to human activity come from the fossil fuels used for generating electricity, with each power plant capable of emitting several million tones of CO 2 annually. These fossil fuels provides >80 % energy needs all over the world and will continue to do so for the foreseeable future.
  • Typical CO 2 emission from coal fired power plant is 800 kg CO 2 /MWh of electricity produced (IEA Greenhouse Gas R&D Programme, 2003, "Greenhouse gas emissions from power stations", Available on web at http://www.ieagreen.org.uk/emis4.htm).
  • a variety of other industrial processes also emit large amounts of CO 2 from each plant, for example oil refineries, cement works, and iron and steel production.
  • flue gas from a coal fired thermal power plant contains around 15% CO 2 , 81 % N 2 and the rest contains other gases such as oxygen, SO x , NO x etc. on dry basis.
  • the flue gas from a natural gas fired thermal power plant contains around 4% CO 2 , 81% N 2 and around 15% O 2 and some minor quantities of SO x , NO x etc. on dry basis.
  • the ultimate objective of the CO 2 capture is the stabilization of greenhouse gas concentrations in the atmosphere at a level that prevents dangerous anthropogenic interference with the climate system.
  • Carbon dioxide present in any gas stream can be removed either by chemically absorbing in a solution of an alkali or amine, or by physically adsorbing on an adsorbent such as activated carbon or zeolite.
  • the methods of physical adsorption of carbon dioxide using a zeolite adsorbent include a pressure swing adsorption (PSA) process, pressure temperature swing (PTSA) process, or vacuum swing adsorption (VSA) process.
  • PSA pressure swing adsorption
  • PTSA pressure temperature swing
  • VSA vacuum swing adsorption
  • adsorption of carbon dioxide by a zeolite adsorbent is effected at high pressure and low temperature and desorption thereof from the zeolite is effected at lower pressure and/or at a higher temperature than the adsorption conditions.
  • the zeolite may be purged with a gas which is less adsorbed than carbon dioxide.
  • the use of a treatment cycle involve the steps of a) passing the contaminated gas flow into ari adsorption region comprising the adsorbent bed, the adsorbent bed providing for the separation of the contaminant or contaminants by adsorption, b) desorbing the adsorbed CO 2 by establishing a pressure gradient and gradually reducing the pressure in the adsorption region to recover the CO 2 via the inlet into the adsorption region, c) increasing the pressure in the adsorption region by introducing a pure gas stream via the outlet of the adsorption region.
  • the adsorption is carried out at pressures of between 1 and 10 bar and desorption is carried out at pressures of between 0.1 and 2 bar. It does not disclose the adsorption selectivity between carbon dioxide and nitrogen and also does not provide the breakthrough data of carbon dioxide and nitrogen ad/desorption.
  • the adsorbent is a combination of sodium form of a low-silica faujasite, having a residual content of potassium ions less than about 8.0 percent (equiv.), a low content of crystalline and amorphous admixtures and, crystal sizes generally within the range of 1- 4 ⁇ m, and a binder.
  • the process for the adsorbent preparation comprises specific parameters of low silica faujasite synthesis, sodium- potassium ion exchange, blending and granulation.
  • the zeolite adsorbent is ion-exchanged with lithium and/or sodium, and is prepared by a process including a step of contacting with a caustic solution a calcined product of a mixture of a low-silica type X zeolite and kaolin clay whereby the kaolin clay is converted to a low- silica type X zeolite.
  • the method of the present invention is claimed to be employed for purification of air when cryogenic separation of air is conducted, or for purification of natural gas. It does not disclose adsorption data for adsorptive separation of carbon dioxide from a gaseous mixture wherein carbon dioxide content is higher; about 10 -15%, as in flue gas from power plant.
  • 5,917,136 (Gaffeney et al., 1999) wherein they claim a pressure swing process for absorbing CO 2 from a gaseous mixture containing CO 2 by introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100 0 C and 500 0 C to adsorb CO 2 to provide a CO 2 laden alumina adsorbent and a CO 2 depleted gaseous mixture and the CO 2 laden alumina adsorbent is regenerated by purging with a weakly adsorbing gas at lower pressure.
  • this process needs very high temperature for the CO 2 adsorption.
  • the novelty of the present invention lies in finding out a suitable pentasil type zeolite for selective adsorption of CO 2 from flue gas and the adsorbent have (l) high selectivity and adsorption capacity for carbon dioxide at high temperature; (2) adequate adsorption/desorption kinetics for carbon dioxide at operating conditions; (3) stable adsorption capacity of carbon dioxide after repeated adsorption/desorption cycles; (4) adequate mechanical strength of adsorbent particles after cyclic exposure to high pressure streams.
  • the main object of the present invention is to provide a molecular sieve adsorbent for the selective adsorption and recovery of carbon dioxide from gas streams at ambient to elevated temperatures, especially from the flue gases which contains 3 - 15 % of carbon dioxide on dry volume basis.
  • Another object of the present invention is to provide a molecular sieve adsorbent of pentasil type zeolite, especially ZSM-5 zeolite with different SiO 2 /Al 2 O 3 ratio in the range of 25-900 and forming the adsorbent in shaped product for the selective adsorption of carbon dioxide from its gaseous mixture and the recovery of carbon dioxide thereof.
  • Yet another object of the present invention is the use of a carbon dioxide selective adsorbent in pressure swing adsorption (PSA) process, vacuum pressure swing adsorption (VPSA) process, or pressure temperature swing adsorption (PTSA) process, for the removal of carbon dioxide from its gaseous mixture, especially from flue gases.
  • PSA pressure swing adsorption
  • VPSA vacuum pressure swing adsorption
  • PTSA pressure temperature swing adsorption
  • the present invention relates to a process for the preparation and use of Pentasil type zeolite molecular sieves for the selective adsorption of carbon dioxide from flue gas generated from thermal power plant, at ambient to elevated temperatures; wherein the said process comprising the steps of- a. preparing a mixture of Pentasil type zeolite powder ZSM-5 with a silica/alumina ratio ranging between 25-900 and clay at a ratio of 4:1 with water, followed by kneading of the mixture for 1-3 hrs; b. shaping the kneaded product as obtained in step (a) by using a hand operated extruder in the form of extrudates having a diameter in the range of 1.5-4.5mm; c.
  • step (b) drying said extrudates as obtained in step (b) at a temperature between 333 - 373 K for 6 to 12 hrs to obtain the adsorbent bodies; d. breaking the dried extrudates in to pieces of about 3-6 mm length, e. subjecting the adsorbent bodies as obtained in step (d) to calcination at a temperature in the range of 723 - 873 K for a period in the range of 2 to 5 hrs;
  • step (e) activating the adsorbent bodies as obtained in step (e) in the adsorbent column at a temperature between 523 - 623 K for 5-10hrs followed by adsorption by passing the feed gas mixture Cl 5% by volume CO 2 + ⁇ 85% by volume N 2 ) through the activated adsorbent column at a flow rate in the range of 100-120ml/min and pressure in the range of 1-1.1 atmosphere.
  • the said molecular sieve adsorbent is of pentasil type zeolite comprising mordenite, ZSM-5 and zeolite beta.
  • the said clay used is bentonite clay.
  • the said clay is present in an amount of 5 to 20% by weight.
  • the adsorbent bodies are activated at a temperature in the range of 823 to 873K for a time period in the range of 6-7hrs .
  • the said zeolite having higher linearity for carbon dioxide adsorption isotherms is ZSM-5 with a silica/ alumina ratio above 100.
  • the column pressure during adsorption and desorption is 1 atm.
  • the said zeolite having favorable carbon dioxide desorption kinetics is ZSM-5 with a silica/alumina ratio above 100.
  • the adsorption temperatures are in the range of 293-423 K.
  • the adsorbent is having linearity for the carbon dioxide adsorption isotherms and favorable carbon dioxide desorption kinetics for easy desorption of adsorbed carbon dioxide from the adsorbent.
  • the processes for the commercial utilization of the said carbon dioxide selective molecular sieve adsorbent are vacuum swing adsorption process; pressure swing adsorption process; vacuum pressure swing adsorption process; or pressure temperature swing adsorption process.
  • FIG. 1 is a diagram of equilibrium adsorption isotherms of CO 2 and N 2 in ZSM ⁇ 5(25) at 303 K.
  • FIG. 2 is a diagram of equilibrium adsorption isotherms of CO 2 and N 2 in ZSM-5(40) at 303 K.
  • FIG. 3 is a diagram of equilibrium adsorption isotherms of CO 2 and N 2 in ZSM ⁇ 5(l00) at 303 K.
  • FIG. 4 is a diagram of equilibrium adsorption isotherms of CO 2 and N 2 in ZSM-5(400) at 303 K.
  • FIG. 5 is a diagram of equilibrium adsorption isotherms of CO 2 and N 2 in ZSM ⁇ 5(900) at 303 K.
  • FIG. 6 is a diagram of breakthrough curve of CO 2 in ZSM ⁇ 5(25) adsorbent pellets at 303 K as described in Example- 9.
  • FIG. 7 is a diagram of breakthrough curve of CO 2 in ZSM ⁇ 5(40) adsorbent pellets at 303 K as described in Example- 10.
  • FIG. 8 is a diagram of breakthrough curve of CO 2 in ZSM ⁇ 5(100) adsorbent pellets at 303 K as described in Example- 11.
  • FIG. 9 is a diagram of breakthrough curve of CO 2 in ZSM ⁇ 5(400) adsorbent pellets at 303 K as described in Example 12.
  • FIG. 10 is a diagram of breakthrough curve of CO 2 in ZSM-5(900) adsorbent pellets at 303 K as described in Example- 13.
  • the present invention provides a process for the preparation of a molecular sieve adsorbent for the selective adsorption of carbon dioxide from its gaseous mixture with nitrogen.
  • Zeolites which are microporous crystalline aluminosilicates, are finding increased applications for the separation of mixtures of compounds having closely related molecular properties.
  • SiO 2 and AlO 2 tetrahedra are connected by sharing oxygen atoms.
  • Al 3+ and Si 4+ ions are buried in the tetrahedra of oxygen atoms and are not directly exposed to adsorbate molecules.
  • the main interactions of the adsorbate molecules in a zeolite structure are through lattice oxygen atoms and extra framework cations.
  • the molecular sieve adsorbent of interest in the present invention was of pentasil type zeolite, especially ZSM-5 with a silica/alumina ratio in the range of 25 - 900.
  • the exchangeable extra-framework cations in the ZSM-5 zeolite were sodium ions.
  • Zeolite ZSM-5 in powder form with different silica/ alumina ratios of 25, 40, 100, 400, and 900, hereafter named as ZSM-5(25), ZSM-5(40), ZSM-5(100), ZSM-5(400) and ZSM- 5(900) respectively, were procured from Zeochem AG, Switzerland and used as such for the equilibrium adsorption measurements of carbon dioxide and nitrogen.
  • the ZSM-5 zeolite was shaped into 3 mm extrudate pellets.
  • To make 100 parts by weight of ZSM-5 adsorbent pellets 80 parts by weight of ZSM-5 powder and 20 parts by weight of bentonite clay were incorporated and mixed together for 15 minutes and then 15 - 25 % by weight of water was added, followed by kneading for 1.5 hours.
  • the kneaded product was extruded by using a hand-operated, extrusion machine to give a shaped product in the form of extrudates having an average diameter of 3 mm.
  • Extrudates were dried at 353 K overnight and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM-5.
  • Carbon dioxide and nitrogen adsorption at 303 K and 333 K were studied in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010), after activating the sample at 623 K under vacuum for about 4 - 8 hrs as described in the examples herein.
  • the samples were evacuated completely and requisite amount of the adsorbate gas was injected into the volumetric set up at volumes required to achieve a targeted set of pressures ranging from 0.1 to 850 mmHg.
  • a minimum equilibrium interval of 5 seconds with a relative target tolerance of 5.0% of the targeted pressure and an absolute target tolerance of 5.000 mmHg were used to determine equilibrium for each measurement point.
  • Adsorption temperature was maintained ( ⁇ O.IK) by circulating water from a constant temperature bath (Julabo F25, Germany).
  • the pure component selectivity of two gases A and B was calculated by using the equation,
  • V A and V B are the volumes of gas A and B respectively adsorbed at any given pressure P and temperature T.
  • Isosteric heats of adsorption were calculated from the adsorption data collected at 288 K and 303 K using Clausius-Clapeyron equation.
  • R is the universal gas constant
  • ⁇ is the fraction of the adsorbed sites at a pressure P and temperature T.
  • Another important embodiment of present invention is the dynamic adsorption data of carbon dioxide from its gaseous mixture with nitrogen in the carbon dioxide selective adsorbent.
  • the ZSM-5 pellets prepared as per the above mentioned procedure were filled in an adsorbent column having a dimension of 35 cm length and 1.9 cm diameter and activated in situ in the adsorbent column at heating rate of 2 K/min to 623 K and the temperature was maintained for 12- 24 hrs under N 2 flow for 8 - 24 hrs and then cooled to the breakthrough measurement temperatures, 303 K and 348 K respectively.
  • the feed gas consist of around 15% CO 2 and 85% N 2 , in which N 2 acts as a carrier gas for the dynamic adsorption measurements, is passed through the adsorbent column at a flow rate of around 120 ral/min.
  • the feed concentration and the product concentration at the other end of adsorbent column are measured in a GC instrument (GC-7610, Chemito Technologies FVt. Ltd., Nasik, India) equipped with a TCD detector (TCD 866) using a Porapaq packed column with H 2 gas as a carrier gas at a flow rate of 40 ml/min.
  • GC-7610 Chemito Technologies FVt. Ltd., Nasik, India
  • TCD 866 TCD detector
  • Around 1.5 ml of the gas samples were taken in a gas tight syringe and analyzed in the GC.
  • the concentration profile of carbon dioxide at the outlet of the adsorbent column is plotted against time and it is defined hereafter as the breakthrough curve of carbon dioxide in the particular
  • zeolite ZSM ⁇ 5(40) 0.5 g was activated at 623 K under vacuum (5xlO ⁇ 3 mm Hg) for 12 hrs and then cooled to room temperature.
  • Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption ⁇ system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K.
  • the equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM ⁇ 5(40) powder at 303 K and 333 K are given in FIG. 2.
  • the heat of adsorption, adsorption capacity and selectivity Of CO 2 and N 2 in ZSM-5(40) are given in Table 1.
  • zeolite ZSM ⁇ 5(100) 0.5 g was activated at 623 K under vacuum (5xlO "3 mm Hg) for 12 hrs and then cooled to room temperature.
  • Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K.
  • the equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM-5(100) powder at 303 K and 333 K are given in FIG. 3.
  • the heat of adsorption, adsorption capacity and selectivity of CO 2 and N 2 in ZSM ⁇ 5(100) are given in Table 1.
  • zeolite ZSM-5(400) 0.5 g was activated at 623 K under vacuum (5 ⁇ lO ⁇ 3 mm Hg) for 12 hrs and then cooled to room temperature.
  • Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K.
  • the equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM ⁇ 5(400) powder at 303 K and 333 K are given in FIG. 4.
  • the heat of adsorption, adsorption •capacity and selectivity of CO 2 and N 2 in ZSM-5(400) are given in Table 1.
  • zeolite ZSM-5(900) 0.5 g was activated at 623 K under vacuum (5xlO ⁇ 3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333
  • zeolite mordenite ZM-060 (procured from Zeocat, France) was activated at 623 K under vacuum (5 ⁇ lCT 3 mm Hg) for 12 hrs and then cooled to room temperature.
  • Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K.
  • the equilibrium capacity for CO 2 and N 2 in ZM-060 were 70 cc /gram and 16 cc /gram respectively at 303 K.
  • zeolite mordenite ZM-510 (procured from Zeocat, France), was activated at 623 K under vacuum (5xl0 ⁇ 3 mm Hg) for 12 hrs and then cooled to room temperature.
  • zeolite beta, Na j3 ⁇ 25 was activated at 623 K under vacuum (5xlO ⁇ 3 mm Hg) for 12 hrs and then cooled to room temperature.
  • Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K.
  • the equilibrium capacity for CO 2 and N 2 in Na )3 -25 were 49.6 cc /gram and 4.7 cc /gram respectively at 303 K.
  • Example 1 80 g of the adsorbent mentioned in Example 1 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours.
  • the kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm.
  • Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM ⁇ 5(25).
  • the column pressure was 1 atm (absolute) during adsorption and desorption.
  • the breakthrough capacity of CO 2 in ZSM ⁇ 5(25) adsorbent pellets were found to be 25.6 cc /gram and 17.2 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
  • Example 2 80 g of the adsorbent mentioned in Example 2 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours.
  • the kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm.
  • Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM ⁇ 5(40).
  • the column pressure was 1 atm (absolute) during adsorption and desorption.
  • the breakthrough capacity of CO 2 in ZSM-5(40) adsorbent pellets were found to be 23.5 cc /gram and 14.8 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
  • Example 3 80 g of the adsorbent mentioned in Example 3 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours.
  • the kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm.
  • Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM ⁇ 5(100).
  • the column pressure was 1 atm (absolute) during adsorption and desorption.
  • the breakthrough capacity of CO 2 in ZSM-5(100) adsorbent pellets were found to be 12.1 cc /gram and 6.3 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
  • Example 4 80 g of the adsorbent mentioned in Example 4 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours.
  • the kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm.
  • Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM ⁇ 5(400).
  • the column pressure was 1 atm (absolute) during adsorption and desorption.
  • the breakthrough capacity of CO 2 in ZSM-5(400) adsorbent pellets were found to be 8.1 cc /gram and 4 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
  • Example 5 80 g of the adsorbent mentioned in Example 5 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM ⁇ 5(900).
  • the column pressure was 1 atm (absolute) during adsorption and desorption.
  • the breakthrough capacity of CO 2 in ZSM ⁇ 5(900) adsorbent pellets were found to be 7.6 cc /gram and 4 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
  • the adsorbent which is having good adsorption capacity as well as desorption kinetics for CO 2 , is good for the removal of CO 2 from the power plant flue gas.

Abstract

The present invention relates to a process for the preparation and use of Pentasil type zeolite molecular sieves for the selective adsorption of carbon dioxide from a gaseous mixture containing carbon dioxide in the range of 3 to 20 % by volume as in the case of power plant flue gas. Particularly, the present invention relates to the use of pentasil type zeolites comprising of mordenite, zeolite beta and ZSM-5, with SiO2/Al2O3 ratio 25-900 at temperature in the range of 293-423K and ambient pressures. The highest equilibrium adsorption capacity for CO2 was 51.5 cc/g and highest breakthrough capacity for CO2 was 25.6 cc/g at 303K at a total feed gas flow of around 120 ml/min in ZSM-5(25) adsorbent pellets.

Description

A process for the preparation and use of Pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas
FIELD OF INVENTION The present invention relates to a process for the preparation and use of Pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas by selective adsorption of carbon dioxide from a gaseous mixture containing carbon dioxide in the range of 3 to 20 % by volume as in the case of power plant flue gas. Particularly, the present invention relates to the use of pentasil type zeolites, especially ZSM-5 having SiO2/ Al2O3 ratio in the range of 25- 900, as a carbon dioxide selective adsorbent for the separation of carbon dioxide from the flue gas of thermal power plants.
BACKGROUND OF THE INVENTION
The contribution of CO2 towards global warming is one of the most important contemporary environmental issues and it is necessary to have available technology which minimizes the discharge of CO2 into the atmosphere. Increasing concentrations of carbon dioxide and other gases like methane, nitrous oxide etc., in the earth' s atmosphere are aggravating the natural greenhouse gas effect and leading to unwanted climate change, with consequent risks of extreme weather, rising sea level and adverse effects on agriculture and biodiversity. An agreement on global warming was reached by the United Nations Conference on Climate Change in Kyoto, Japan in 1997, which is known as Kyoto Protocol. Under this protocol, industrialized countries and those in transition to a market economy have agreed to limit or reduce their emissions of these greenhouse gases by at least 5% below 1990 levels during the period 2008 to 2012 (Kyoto Protocol To The United Nations Framework Convention On Climate Change, 1997, Available on web at: http://unfccc.int/resource/docs/convkp/kpeng.html). The global warming potential (GWP) of methane and nitrous oxide are much higher than that of CO2, but CO2 makes greatest contribution to greenhouse gas effect due to large amount of CO2 emitted to the atmosphere by human activity (IEA Greenhouse Gas R&D Programme, 1999."Greenhouse Gases", Available on web at: http://www.ieagreen.org.uk/ climate.html). Approximately one third of all CO2 emissions due to human activity come from the fossil fuels used for generating electricity, with each power plant capable of emitting several million tones of CO2 annually. These fossil fuels provides >80 % energy needs all over the world and will continue to do so for the foreseeable future. Typical CO2 emission from coal fired power plant is 800 kg CO2/MWh of electricity produced (IEA Greenhouse Gas R&D Programme, 2003, "Greenhouse gas emissions from power stations", Available on web at http://www.ieagreen.org.uk/emis4.htm). A variety of other industrial processes also emit large amounts of CO2 from each plant, for example oil refineries, cement works, and iron and steel production. These emissions could be reduced substantially, without major changes to the basic process, by capturing and storing the emitted CO2. Typically, flue gas from a coal fired thermal power plant contains around 15% CO2, 81 % N2 and the rest contains other gases such as oxygen, SOx, NOx etc. on dry basis. The flue gas from a natural gas fired thermal power plant contains around 4% CO2, 81% N2 and around 15% O2 and some minor quantities of SOx, NOx etc. on dry basis. The ultimate objective of the CO2 capture is the stabilization of greenhouse gas concentrations in the atmosphere at a level that prevents dangerous anthropogenic interference with the climate system.
Carbon dioxide present in any gas stream can be removed either by chemically absorbing in a solution of an alkali or amine, or by physically adsorbing on an adsorbent such as activated carbon or zeolite. The methods of physical adsorption of carbon dioxide using a zeolite adsorbent include a pressure swing adsorption (PSA) process, pressure temperature swing (PTSA) process, or vacuum swing adsorption (VSA) process. In these methods, adsorption of carbon dioxide by a zeolite adsorbent is effected at high pressure and low temperature and desorption thereof from the zeolite is effected at lower pressure and/or at a higher temperature than the adsorption conditions. Upon desorption, the zeolite may be purged with a gas which is less adsorbed than carbon dioxide.
Reference may be made to U. S. Pat. No. 2,882,244, (Milton et al., 1959) wherein they claim a variety of crystalline aluminosilicates useful for CO2 adsorption.
Reference may be made to U. S. Pat. No. 3,078,639, (Milton et al., 1963) wherein they claim a zeolite-X useful for the adsorption of carbon dioxide from a gas stream.
Reference may be made to British Patent Nos. 1,508,928, Mobil Oil, and 1,051,621, (Furtig et al., 1913) where they have disclosed faujasite-type zeolites having silica to alumina ratio from 1.8 to 2.2. However, the adsorption capacity for carbon dioxide of these adsorbents is quite interesting but there should be a limitation because these molecular sieves are hydrophilic in nature. To increase carbon dioxide adsorption capacity, several adsorbents have been proposed based on various cation exchanged forms of zeolite molecular sieves.
Reference may be made to U. S. Pat. No. 3,885,927 (Sherman et al., 1975) wherein they claim a barium cation form of zeolite X in which 90-95% of the Na+ ions are replaced by Ba2+ ions.
Reference may be made to, U.S. Pat. No. 4,775,396, (Rastelli et al., 1988) wherein they claim carbon dioxide removal by the use of zinc, rare earth metals, a proton and ammonium cation exchanged forms of synthetic faujasite having silica to alumina ratio in broad range of 2-100 for carbon dioxide removal.
Reference may be made to U. S. Pat. No. 3,981,698 (Leppard et al., 1976), U. S. Pat. No.4,039,620 (Netteland, et al. 1977), U. S. Pat. No. 4,711,645 (Kumar, 1987), U. S. Pat. No.4,986,835 (Uno et al., 1991) and U. S. Pat. No. 5,156,657 Gain et al. 1992) wherein they claim the use of standard molecular sieves 5A, 1OA and 13X as adsorbents for CO2 separation. These molecular sieves can be used in PSA process at ambient temperature due to the physical adsorption. However, they possess sufficient adsorption capacity for carbon dioxide but the moisture in gas stream would reduce the adsorbent capacity.
Reference may be made to U. S. Pat. No. 5,531,808 (Ojo et. al., 1996) which discloses a method of removing carbon dioxide from a gas stream by using a zeolite adsorbent, wherein the gas stream is contacted with a type X zeolite having a silicon/aluminum atomic-ratio of about 1.0 to 1.15 and having been ion-exchanged with a cation selected from the ions of groups IA, 2A, 3A, 3B1 the lanthanide series of the periodic table and mixtures thereof at a temperature of about -50° C to about +80° C. It is noted that the change of the uptake of carbon dioxide depending upon the pressure of carbon dioxide is examined, but, the selective adsorption of carbon dioxide in a gaseous mixture containing carbon dioxide and nitrogen is not examined therein. Further, as preferable exchangeable cations, sodium and lithium are mentioned in U. S. Pat. No. 5,531,808. It is shown that Li-LSX, Ca-LSX is superior to Na-LSX in the uptake of carbon dioxide, but, the adsorption selectivity between carbon dioxide and nitrogen is not examined. A method of removing water vapor and carbon dioxide from a gas wherein water vapor is first removed and then carbon dioxide is removed by using sodium LSX zeolite as adsorbent has been proposed in U.S. Pat. No. 5,914,455 Gain et al., 1999). However, this patent is silent on the removal of carbon dioxide from a gaseous mixture containing carbon dioxide and nitrogen.
Reference may be made to U. S. Pat. No. 6,616,732 (Grandmougin et al., 2003) which discloses a novel family of zeolite adsorbents, suited to the decarbonation of gas flows contaminated by CO2, comprising a mixture of zeolite X and zeolite LSX, these adsorbents being predominantly exchanged with sodium or with strontium. The process for producing an agglomerated adsorbent as per this patent comprises many steps. Further, the use of a treatment cycle involve the steps of a) passing the contaminated gas flow into ari adsorption region comprising the adsorbent bed, the adsorbent bed providing for the separation of the contaminant or contaminants by adsorption, b) desorbing the adsorbed CO2 by establishing a pressure gradient and gradually reducing the pressure in the adsorption region to recover the CO2 via the inlet into the adsorption region, c) increasing the pressure in the adsorption region by introducing a pure gas stream via the outlet of the adsorption region. Moreover, the adsorption is carried out at pressures of between 1 and 10 bar and desorption is carried out at pressures of between 0.1 and 2 bar. It does not disclose the adsorption selectivity between carbon dioxide and nitrogen and also does not provide the breakthrough data of carbon dioxide and nitrogen ad/desorption.
Reference may be made to U. S. Pat. No. 6,530,975 (Rode et al., 2003) wherein they claim preparation of a molecular sieve adsorbent for the purification of gas streams containing water vapor and carbon dioxide. The adsorbent is a combination of sodium form of a low-silica faujasite, having a residual content of potassium ions less than about 8.0 percent (equiv.), a low content of crystalline and amorphous admixtures and, crystal sizes generally within the range of 1- 4 μm, and a binder. The process for the adsorbent preparation comprises specific parameters of low silica faujasite synthesis, sodium- potassium ion exchange, blending and granulation. It provides the carbon dioxide adsorption isotherms for low-silica faujasite having differing percentages of residual potassium cations and compares the carbon dioxide adsorption of various adsorbents including the molecular sieve 5A (CaA-94.5 % Ca2f), molecular sieve 1OA (CaX), molecular sieve 13X (NaX) and calcium low-silica faujasite with a potassium ion content of 0.16 percent. However, it does not disclose adsorption data for nitrogen.
Reference may be made to U. S. Pat. No. 6,537,348 (Hirano et al., 2003) wherein they claim a method of adsorptive separation of carbon dioxide from a gaseous mixture comprising carbon dioxide and gases less polar than carbon dioxide comprising contacting the gaseous mixture with a zeolite adsorbent is effected wherein carbon dioxide present in the gaseous mixture as contacted with the zeolite has a partial pressure of 0.1 to 50 mmHg, and the zeolite adsorbent is a shaped product comprised of at least 95%, as determined in the basis of the moisture equilibrium adsorption value, of a low-silica type X zeolite having an SiO2 /Al2O3 molar ratio of 1.9 to 2.1. Preferably, the zeolite adsorbent is ion-exchanged with lithium and/or sodium, and is prepared by a process including a step of contacting with a caustic solution a calcined product of a mixture of a low-silica type X zeolite and kaolin clay whereby the kaolin clay is converted to a low- silica type X zeolite. The method of the present invention is claimed to be employed for purification of air when cryogenic separation of air is conducted, or for purification of natural gas. It does not disclose adsorption data for adsorptive separation of carbon dioxide from a gaseous mixture wherein carbon dioxide content is higher; about 10 -15%, as in flue gas from power plant.
Reference may be made to U. S. Pat. No. 7,011,695 (Moreau et al., 2006) wherein they claim zeolite adsorbent, and method of production, exchanged with calcium and barium cations, for purifying or separating a gas or gas mixture, in particular air, so as to remove there from the impurities found therein, such as hydrocarbons and nitrogen oxides. The adsorbent is preferably an X or LSX zeolite and the gas purification process is of the temperature swing adsorption type. It does not disclose sorption data for carbon dioxide and nitrogen.
All of these molecular sieve adsorbents are characterized by carbon dioxide adsorption capacity extended at moderate and high partial pressures of the admixture to be adsorbed. However, their capacity to adsorb at low partial pressure of CO2 (< 5 Torr) and at ambient temperatures is not sufficient to provide the purity of the gas required. In addition, due to the relatively short time before CO2 breakthrough, the water adsorption capacity of these adsorbents appears to be only 10-15 percent of their potential. This decreases adsorbent performance in such applications as TSA and PSA air pre- purification units where carbon dioxide inlet adsorption is very low. Reference may be made to U. S. Pat. No. 5,917,136 (Gaffeney et al., 1999) wherein they claim a pressure swing process for absorbing CO2 from a gaseous mixture containing CO2 by introducing the gaseous mixture at a first pressure into a reactor containing a modified alumina adsorbent maintained at a temperature ranging from 100 0C and 500 0C to adsorb CO2 to provide a CO2 laden alumina adsorbent and a CO2 depleted gaseous mixture and the CO2 laden alumina adsorbent is regenerated by purging with a weakly adsorbing gas at lower pressure. However, this process needs very high temperature for the CO2 adsorption.
Reference may be made to U. S. Pat. No. 7,314,847 (Siriwardane, 2008) which discloses a process for making granular sorbent to capture carbon dioxide from gas streams comprising homogeneously mixed metal oxides and a binder comprising of sodium orthosilicate, calcium sulfate dehydrate, alkali silicates, calcium aluminate, bentonite, inorganic clays and organic clays. However, it does not disclose equilibrium sorption data for carbon dioxide and nitrogen.
There are other prior art related to the removal of CO2 from different gas streams available in the literature. For example, Katoh et al. studied the adsorption and its IR characteristics of alkali metal exchanged ZSM-5 zeolite in CO2/N2 mixture of gases (Journal of Colloid and Interface Science 2000, 226, 145-150). Inui et al (Ind. Eng. Chem. Res.; 1988; 27(7); 1103-1109) studied on CO2 separation from mixtures of CO2/He by pressure swing adsorption using H-ZSM-5. Li et al. (Miproporous and Mesoporous Materials 2007, 98, 94-101) investigated the adsorption equilibrium and kinetic separation potential of zeolite- /3 for N2, O2, CO2 and CH4 gases by using concentration pulse chromatography. Yong et al. (Ind. Eng. Chem. Res., 2001, 40, 204-209) have studied the equilibrium adsorption isotherms of CO2 in different hydrotalcites at higher temperatures and shown that the adsorption capacity for CO2 first decreases with temperature and then increases as temperature increases. The novelty of the present invention lies in finding out a suitable pentasil type zeolite for selective adsorption of CO2 from flue gas and the adsorbent have (l) high selectivity and adsorption capacity for carbon dioxide at high temperature; (2) adequate adsorption/desorption kinetics for carbon dioxide at operating conditions; (3) stable adsorption capacity of carbon dioxide after repeated adsorption/desorption cycles; (4) adequate mechanical strength of adsorbent particles after cyclic exposure to high pressure streams.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a molecular sieve adsorbent for the selective adsorption and recovery of carbon dioxide from gas streams at ambient to elevated temperatures, especially from the flue gases which contains 3 - 15 % of carbon dioxide on dry volume basis.
Another object of the present invention is to provide a molecular sieve adsorbent of pentasil type zeolite, especially ZSM-5 zeolite with different SiO2/Al2O3 ratio in the range of 25-900 and forming the adsorbent in shaped product for the selective adsorption of carbon dioxide from its gaseous mixture and the recovery of carbon dioxide thereof.
Yet another object of the present invention is the use of a carbon dioxide selective adsorbent in pressure swing adsorption (PSA) process, vacuum pressure swing adsorption (VPSA) process, or pressure temperature swing adsorption (PTSA) process, for the removal of carbon dioxide from its gaseous mixture, especially from flue gases.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a process for the preparation and use of Pentasil type zeolite molecular sieves for the selective adsorption of carbon dioxide from flue gas generated from thermal power plant, at ambient to elevated temperatures; wherein the said process comprising the steps of- a. preparing a mixture of Pentasil type zeolite powder ZSM-5 with a silica/alumina ratio ranging between 25-900 and clay at a ratio of 4:1 with water, followed by kneading of the mixture for 1-3 hrs; b. shaping the kneaded product as obtained in step (a) by using a hand operated extruder in the form of extrudates having a diameter in the range of 1.5-4.5mm; c. drying said extrudates as obtained in step (b) at a temperature between 333 - 373 K for 6 to 12 hrs to obtain the adsorbent bodies; d. breaking the dried extrudates in to pieces of about 3-6 mm length, e. subjecting the adsorbent bodies as obtained in step (d) to calcination at a temperature in the range of 723 - 873 K for a period in the range of 2 to 5 hrs;
f. activating the adsorbent bodies as obtained in step (e) in the adsorbent column at a temperature between 523 - 623 K for 5-10hrs followed by adsorption by passing the feed gas mixture Cl 5% by volume CO2 + ~85% by volume N2) through the activated adsorbent column at a flow rate in the range of 100-120ml/min and pressure in the range of 1-1.1 atmosphere.
g.ultimately, de^orbing the carbon dioxide by passing nitrogen gas at a flow rate in the range of 98-102ml/min, counter-currently to feed flow.
In an embodiment of the present invention the said molecular sieve adsorbent is of pentasil type zeolite comprising mordenite, ZSM-5 and zeolite beta.
In another embodiment of the present invention the said clay used is bentonite clay.
In yet another embodiment of the present invention the said clay is present in an amount of 5 to 20% by weight.
In still another embodiment of the present invention, the adsorbent bodies are activated at a temperature in the range of 823 to 873K for a time period in the range of 6-7hrs .
In another embodiment of the present invention, the said zeolite having higher linearity for carbon dioxide adsorption isotherms is ZSM-5 with a silica/ alumina ratio above 100.
In further another embodiment of the present invention, the column pressure during adsorption and desorption is 1 atm.
In yet another embodiment of the present invention, the said zeolite having favorable carbon dioxide desorption kinetics is ZSM-5 with a silica/alumina ratio above 100.
In another embodiment of the present invention, the adsorption temperatures are in the range of 293-423 K.
In another embodiment of the present invention, the adsorbent is having linearity for the carbon dioxide adsorption isotherms and favorable carbon dioxide desorption kinetics for easy desorption of adsorbed carbon dioxide from the adsorbent.
In yet another embodiment of the present invention, the processes for the commercial utilization of the said carbon dioxide selective molecular sieve adsorbent are vacuum swing adsorption process; pressure swing adsorption process; vacuum pressure swing adsorption process; or pressure temperature swing adsorption process.
BRIEF DESCRIPTION OF THE DRAWINGS
For the further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a diagram of equilibrium adsorption isotherms of CO2 and N2 in ZSM~5(25) at 303 K.
FIG. 2 is a diagram of equilibrium adsorption isotherms of CO2 and N2 in ZSM-5(40) at 303 K.
FIG. 3 is a diagram of equilibrium adsorption isotherms of CO2 and N2 in ZSM~5(l00) at 303 K.
FIG. 4 is a diagram of equilibrium adsorption isotherms of CO2 and N2 in ZSM-5(400) at 303 K.
FIG. 5 is a diagram of equilibrium adsorption isotherms of CO2 and N2 in ZSM~5(900) at 303 K.
FIG. 6 is a diagram of breakthrough curve of CO2 in ZSM~5(25) adsorbent pellets at 303 K as described in Example- 9.
FIG. 7 is a diagram of breakthrough curve of CO2 in ZSM~5(40) adsorbent pellets at 303 K as described in Example- 10.
FIG. 8 is a diagram of breakthrough curve of CO2 in ZSM~5(100) adsorbent pellets at 303 K as described in Example- 11.
FIG. 9 is a diagram of breakthrough curve of CO2 in ZSM~5(400) adsorbent pellets at 303 K as described in Example 12.
FIG. 10 is a diagram of breakthrough curve of CO2 in ZSM-5(900) adsorbent pellets at 303 K as described in Example- 13.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for the preparation of a molecular sieve adsorbent for the selective adsorption of carbon dioxide from its gaseous mixture with nitrogen. Zeolites, which are microporous crystalline aluminosilicates, are finding increased applications for the separation of mixtures of compounds having closely related molecular properties. In a zeolite framework, SiO2 and AlO2 tetrahedra are connected by sharing oxygen atoms. Al3+ and Si4+ ions are buried in the tetrahedra of oxygen atoms and are not directly exposed to adsorbate molecules. Thus, the main interactions of the adsorbate molecules in a zeolite structure are through lattice oxygen atoms and extra framework cations. The molecular sieve adsorbent of interest in the present invention was of pentasil type zeolite, especially ZSM-5 with a silica/alumina ratio in the range of 25 - 900. The exchangeable extra-framework cations in the ZSM-5 zeolite were sodium ions. Zeolite ZSM-5 in powder form with different silica/ alumina ratios of 25, 40, 100, 400, and 900, hereafter named as ZSM-5(25), ZSM-5(40), ZSM-5(100), ZSM-5(400) and ZSM- 5(900) respectively, were procured from Zeochem AG, Switzerland and used as such for the equilibrium adsorption measurements of carbon dioxide and nitrogen. For the dynamic adsorption measurements, the ZSM-5 zeolite was shaped into 3 mm extrudate pellets. To make 100 parts by weight of ZSM-5 adsorbent pellets, 80 parts by weight of ZSM-5 powder and 20 parts by weight of bentonite clay were incorporated and mixed together for 15 minutes and then 15 - 25 % by weight of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extrusion machine to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K overnight and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM-5.
Carbon dioxide and nitrogen adsorption at 303 K and 333 K were studied in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010), after activating the sample at 623 K under vacuum for about 4 - 8 hrs as described in the examples herein. During analysis, the samples were evacuated completely and requisite amount of the adsorbate gas was injected into the volumetric set up at volumes required to achieve a targeted set of pressures ranging from 0.1 to 850 mmHg. A minimum equilibrium interval of 5 seconds with a relative target tolerance of 5.0% of the targeted pressure and an absolute target tolerance of 5.000 mmHg were used to determine equilibrium for each measurement point. Adsorption temperature was maintained (±O.IK) by circulating water from a constant temperature bath (Julabo F25, Germany). The pure component selectivity of two gases A and B was calculated by using the equation,
Figure imgf000014_0001
Where, VA and VB are the volumes of gas A and B respectively adsorbed at any given pressure P and temperature T.
Isosteric heats of adsorption were calculated from the adsorption data collected at 288 K and 303 K using Clausius-Clapeyron equation.
Figure imgf000014_0002
Where, R is the universal gas constant, θ is the fraction of the adsorbed sites at a pressure P and temperature T.
Another important embodiment of present invention is the dynamic adsorption data of carbon dioxide from its gaseous mixture with nitrogen in the carbon dioxide selective adsorbent. The ZSM-5 pellets prepared as per the above mentioned procedure were filled in an adsorbent column having a dimension of 35 cm length and 1.9 cm diameter and activated in situ in the adsorbent column at heating rate of 2 K/min to 623 K and the temperature was maintained for 12- 24 hrs under N2 flow for 8 - 24 hrs and then cooled to the breakthrough measurement temperatures, 303 K and 348 K respectively. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the dynamic adsorption measurements, is passed through the adsorbent column at a flow rate of around 120 ral/min. The feed concentration and the product concentration at the other end of adsorbent column, are measured in a GC instrument (GC-7610, Chemito Technologies FVt. Ltd., Nasik, India) equipped with a TCD detector (TCD 866) using a Porapaq packed column with H2 gas as a carrier gas at a flow rate of 40 ml/min. Around 1.5 ml of the gas samples were taken in a gas tight syringe and analyzed in the GC. The concentration profile of carbon dioxide at the outlet of the adsorbent column is plotted against time and it is defined hereafter as the breakthrough curve of carbon dioxide in the particular adsorbent.
The following examples are given by way of illustration and therefore should not construed to limit the scope of the present invention.
Example 1
0.5 g of zeolite ZSM~5(25) was activated at 623 K under vacuum (5χlO~3 mm Hg) for 12
-hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333
K. The equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM~5(25) powder at 303 K and 333 K are given in FIG. 1. The heat of adsorption, adsorption capacity and selectivity of CO2 and N2 in ZSM~5(25) are given in Table-1.
Example 2
0.5 g of zeolite ZSM~5(40) was activated at 623 K under vacuum (5xlO~3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption < system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM~5(40) powder at 303 K and 333 K are given in FIG. 2. The heat of adsorption, adsorption capacity and selectivity Of CO2 and N2 in ZSM-5(40) are given in Table 1.
Example 3
0.5 g of zeolite ZSM~5(100) was activated at 623 K under vacuum (5xlO"3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM-5(100) powder at 303 K and 333 K are given in FIG. 3. The heat of adsorption, adsorption capacity and selectivity of CO2 and N2 in ZSM~5(100) are given in Table 1.
Example 4
0.5 g of zeolite ZSM-5(400) was activated at 623 K under vacuum (5χlO~3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM~5(400) powder at 303 K and 333 K are given in FIG. 4. The heat of adsorption, adsorption •capacity and selectivity of CO2 and N2 in ZSM-5(400) are given in Table 1.
Example 5
0.5 g of zeolite ZSM-5(900) was activated at 623 K under vacuum (5xlO~3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333
K. The equilibrium adsorption isotherms of carbon dioxide and nitrogen in ZSM~5(900) powder at 303 K and 333 K are given in FIG. 5. The heat of adsorption, adsorption capacity and selectivity Of CO2 and N2 in ZSM-5(900) are given in Table 1. Example 6
0.5 g of zeolite mordenite, ZM-060 (procured from Zeocat, France), was activated at 623 K under vacuum (5χlCT3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium capacity for CO2 and N2 in ZM-060 were 70 cc /gram and 16 cc /gram respectively at 303 K.
Example 7
0.5 g of zeolite mordenite, ZM-510 (procured from Zeocat, France), was activated at 623 K under vacuum (5xl0~3 mm Hg) for 12 hrs and then cooled to room temperature.
Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system(Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium capacity for CO2 and N2 in ZM-510 were 54.5 cc /gram and 4.3 cc /gram respectively at 303 K.
Example 8
0.5 g of zeolite beta, Na j3 ~25 (procured from Zeocat, France), was activated at 623 K under vacuum (5xlO~3 mm Hg) for 12 hrs and then cooled to room temperature. Equilibrium adsorption measurements of pure carbon dioxide and nitrogen gases in this activated adsorbent were carried out in a static volumetric adsorption system (Micromeritics, USA, Model ASAP 2010) at 303 K and 333 K. The equilibrium capacity for CO2 and N2 in Na )3 -25 were 49.6 cc /gram and 4.7 cc /gram respectively at 303 K.
Example 9
80 g of the adsorbent mentioned in Example 1 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM~5(25). Around 100ml of the adsorbent pellets prepared as described above in this example was activated in situ in the adsorbent column at a temperature of around 623K under N2 flow overnight and then cooled to the temperatures of CO2 breakthrough measurements. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the breakthrough measurements, is passed through the adsorbent column at a flow rate of around 120 ml/min. The CO2 breakthrough in ZSM-5(25) pellets at 303 K is shown in FIG. 6. Desorption of CO2 was carried out by passing N2 at a flow rate of 102 ml/min, counter- currently to the feed flow. The column pressure was 1 atm (absolute) during adsorption and desorption. The breakthrough capacity of CO2 in ZSM~5(25) adsorbent pellets were found to be 25.6 cc /gram and 17.2 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
Example 10
80 g of the adsorbent mentioned in Example 2 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM~5(40). Around 100ml of the adsorbent pellets prepared as described above in this example was activated in situ in the adsorbent column at a temperature of around 623K under N2 flow overnight and then cooled to the temperatures of CO2 breakthrough measurements. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the breakthrough measurements, is passed through the adsorbent column at a flow rate of around 120 ml/min. The CO2 breakthrough in ZSM-5(40) pellets at 303 K is shown in FIG. 7. Desorption of CO2 was carried out by passing N2 at a flow rate of 102 ml/min, counter- currently to the feed flow. The column pressure was 1 atm (absolute) during adsorption and desorption. The breakthrough capacity of CO2 in ZSM-5(40) adsorbent pellets were found to be 23.5 cc /gram and 14.8 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
Example 11
80 g of the adsorbent mentioned in Example 3 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM~5(100). Around 100ml of the adsorbent pellets prepared as described above in this example was activated in situ in the adsorbent column at a temperature of around 623K under N2 flow overnight and then cooled to the temperatures of CO2 breakthrough measurements. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the breakthrough measurements, is passed through the adsorbent column at a flow rate of around 120 ml/min. The CO2 breakthrough in ZSM-5(100) pellets at 303 K is shown in FIG. 8. Desorption of CO2 was carried out by passing N2 at a flow rate of 102 ml/min, counter- currently to the feed flow. The column pressure was 1 atm (absolute) during adsorption and desorption. The breakthrough capacity of CO2 in ZSM-5(100) adsorbent pellets were found to be 12.1 cc /gram and 6.3 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
Example 12
80 g of the adsorbent mentioned in Example 4 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM~5(400). Around 100ml of the adsorbent pellets prepared as described above in this example was activated in situ in the adsorbent column at a temperature of around 623K under N2 flow overnight and then cooled to the temperatures of CO2 breakthrough measurements. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the breakthrough measurements, is passed through the adsorbent column at a flow rate of around 120 ml/min. The CO2 breakthrough in ZSM~5(400) pellets at 303 K is shown in FIG. 9. Desorption of CO2 was carried out by passing N2 at a flow rate of 102 ml/min, counter- currently to the feed flow. The column pressure was 1 atm (absolute) during adsorption and desorption. The breakthrough capacity of CO2 in ZSM-5(400) adsorbent pellets were found to be 8.1 cc /gram and 4 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
Example 13
80 g of the adsorbent mentioned in Example 5 was mixed thoroughly with 20 g of bentonite clay for 15 minutes and then a required amount of water was added, followed by kneading for 1.5 hours. The kneaded product was extruded by using a hand-operated, extruder to give a shaped product in the form of extrudates having an average diameter of 3 mm. Extrudates were dried at 353 K for 16 hours and broken in to pieces of about 3 mm length manually. The dried extrudates were calcined at 873 K for 3 hours under air a muffle furnace to give a shaped product containing zeolite ZSM~5(900). Around 100ml of the adsorbent pellets prepared as described above in this example was activated in situ in the adsorbent column at a temperature of around 623K under N2 flow overnight and then cooled to the temperatures of CO2 breakthrough measurements. The feed gas consist of around 15% CO2 and 85% N2, in which N2 acts as a carrier gas for the breakthrough measurements, is passed through the adsorbent column at a flow rate of around 120 ml/min. The CO2 breakthrough in ZSM~5(900) pellets at 303 K is shown in FIG. 10. Desorption of CO2 was carried out by passing N2 at a flow rate of 102 ml/min, counter- currently to the feed flow. The column pressure was 1 atm (absolute) during adsorption and desorption. The breakthrough capacity of CO2 in ZSM~5(900) adsorbent pellets were found to be 7.6 cc /gram and 4 cc /gram at temperatures 303 K and 348K respectively and at a total feed gas flow of around 120 ml/min.
The advantages of present invention are:
i.The adsorption isotherms of carbon dioxide are more linear and highly reversible as the silica/alumina ratio increases, so that the desorption of the adsorbed carbon dioxide from the said adsorbent is much easier and can be achieved by simple evacuation without the use of higher temperature as in the case of VSA process.
ii. Higher carbon dioxide selectivity over nitrogen at 760 mm Hg as the silica/alumina ratio in ZSM-5 adsorbent increases.
iii.The adsorbent which is having good adsorption capacity as well as desorption kinetics for CO2, is good for the removal of CO2 from the power plant flue gas.

Claims

We claim:
1. A process for the preparation and use of pentasil type zeolite molecular sieves for the selective adsorption of carbon dioxide from flue gas generated from thermal power plant, at ambient to elevated temperatures; wherein the said process comprising the steps of- a)preparing a mixture of Pentasil type zeolite powder ZSM-5 with a silica/alumina ratio ranging between 25-900 and clay at a ratio of 4:1 with water, followed by kneading of the mixture for 1-3 hrs; b)shaping the kneaded product as obtained in step (a) by using a hand operated extruder in the form of extrudates having a diameter in the range of 1.5-4.5mm; c) drying said extrudates as obtained in step (b) at a temperature between 333 -
373 K for 6 to 12 hrs to obtain the adsorbent bodies; d)breaking the dried extrudates in to pieces of about 3-6 mm length,
e)subjecting the adsorbent bodies as obtained in step (d) to calcination at a temperature in the range of 723 - 873 K for a period in the range of 2 to 5 hrs;
^activating the adsorbent bodies as obtained in step (e) in the adsorbent column at a temperature between 523 - 623 K for 5-10hrs followed by adsorption by passing the feed gas mixture having about 15% by volume CO2 and about 85% by volume N2 through the activated adsorbent column at a flow rate in the1 range of 100-120ml/min and pressure in the range of 1-1.1 atmosphere.
g) desorbing the carbon dioxide by passing nitrogen gas at a flow rate in the range of 98-102ml/min, counter-currently to feed flow.
2. The process as claimed in claim 1, wherein the molecular sieve adsorbent is of pentasil type zeolite comprising mordenite, ZSM-5 and zeolite beta.
3. The processes claimed in claim 1, wherein the clay used is bentonite clay.
4. The process as claimed in claim 1, wherein the clay is present in an amount of 5 to 20% by weight.
5. The process as claimed in claim 1, wherein the adsorbent bodies are activated at a temperature in the range of 823 to 873 K for a time period in the range of 6-7 hrs .
6. The process as claimed in claim 1, wherein said zeolite having higher linearity for carbon dioxide adsorption isotherms is ZSM-5 with a silica/ alumina ratio above 100.
7. The process as claimed in claim 1, wherein the column pressure during adsorption and desorption is latm.
8. The process as claimed in claim 1, wherein said zeolite having favorable carbon dioxide desorption kinetics is ZSM-5 with a silica/alumina ratio above 100.
9. The process as claimed in claim 1, wherein the adsorption temperature is in the range of 293-423 K.
10. The process as claimed in claim 1, wherein such an adsorbent is having linearity for the carbon dioxide adsorption isotherms and favorable carbon dioxide desorption kinetics for easy desorption of adsorbed carbon dioxide from the adsorbent.
11. The process as claimed in claim 1, wherein the processes for the commercial utilization of the said carbon dioxide selective molecular sieve adsorbent are vacuum swing adsorption process; pressure swing adsorption process; vacuum pressure swing adsorption process; or pressure temperature swing adsorption process.
PCT/IN2009/000753 2009-03-31 2009-12-30 A process for the preparation and use of pentasil type zeolite for the selective adsorption of carbon dioxide from flue gas WO2010113169A1 (en)

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CN114455585A (en) * 2022-02-16 2022-05-10 青海师范大学 Method for adsorbing carbon dioxide in air
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CN113385141A (en) * 2021-06-23 2021-09-14 浙江大学 Facility CO for improving plant cultivation by applying ZSM-5 molecular sieve2Concentration and method of crop growth
CN113385141B (en) * 2021-06-23 2022-05-31 浙江大学 Facility CO for improving plant cultivation by applying ZSM-5 molecular sieve2Concentration and method of crop growth
CN114455585A (en) * 2022-02-16 2022-05-10 青海师范大学 Method for adsorbing carbon dioxide in air
CN114455585B (en) * 2022-02-16 2024-01-16 青海师范大学 Method for adsorbing carbon dioxide in air
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