CN113070094A - Catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation and preparation method and application thereof - Google Patents

Catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation and preparation method and application thereof Download PDF

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CN113070094A
CN113070094A CN202110350558.2A CN202110350558A CN113070094A CN 113070094 A CN113070094 A CN 113070094A CN 202110350558 A CN202110350558 A CN 202110350558A CN 113070094 A CN113070094 A CN 113070094A
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catalyst
toluene
carbon dioxide
aromatic ring
hzsm
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肖志楷
杨子旭
徐晶
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East China University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
    • B01J29/46—Iron group metals or copper
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
    • C07C2/862—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms
    • C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
    • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
    • C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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Abstract

The invention relates to a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation, a preparation method and application thereof, wherein the catalyst is formed by mixing a Cu-based catalyst and an HZSM-5 molecular sieve; the Cu-based catalyst is a mixed oxide composed of a Cu main body and a modified metal, and the mass ratio of the Cu-based catalyst to the surface HZSM-5 molecular sieve is 1: 3-3: 1; the modified metal is one of Zr, Zn, Ce and Ti, wherein the content of Cu oxide is 50-95 wt%, and the content of the modified metal is 5-50 wt%. Compared with the prior art, the method can reduce the side reaction of preparing olefin from methanol caused by improper feed ratio of methanol to toluene and improve the production efficiency of dimethylbenzene; meanwhile, the isomerization reaction of the dimethylbenzene can be inhibited, and the selectivity of the p-dimethylbenzene in the product is improved; the catalyst has good stability at high temperature, provides a new idea for carbon dioxide hydrogenation and toluene aromatic ring alkylation, and has good industrialization prospect.

Description

Catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation and preparation method and application thereof
Technical Field
The invention relates to a catalyst for preparing paraxylene by carbon dioxide hydrogenation and toluene alkylation, in particular to a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation and a preparation method and application thereof.
Background
CO2Is part of the atmospheric composition and is also an indispensable gas in the carbon cycle of the earth. Since the beginning of the industrial revolution, the explosive productivity of mankind has been accompanied by an ever-increasing energy demand, and therefore CO emitted by the combustion of fossil fuels2Gradually become CO in the atmosphere2Is the main source of (1).
During the period of 1970-2003, the global carbon dioxide emission increases by an average of 1.7% annually, and the CO emitted to the atmosphere by the combustion of fossil fuels is annually emitted2From 150 hundred million tons in 1970 to about 250 million tons in 2003; from 2003 to 2011, with the rapid development of industrial levels in countries around the world, CO is generated2The discharge speed is increased to 3.2%; global CO from 2012 to 20142The growth rate was slightly slowed to 1.4%. 2016 to 2017 global CO2The rate of increase in emissions was 1.2%.
In order to reduce CO in the atmosphere2Content, improving the greenhouse effect, the CCUS (Carbon Capture, inactivation and Storage) strategy, i.e. Carbon Capture Utilization and sequestration, has been proposed. The core idea of the strategy is to discharge CO in the production process2Is utilized to reduce newly added CO in the carbon cycle2And (5) discharging. This strategy is not to simply sequester CO2Instead, CO is introduced2Resource utilization and energy regeneration can be realized, and economic benefits can be generated.
CCUS is a necessary choice for realizing low-carbon transformation of an energy system taking fossil fuels as the leading factor in China. The energy structure of China is mainly coal, and although the country has adopted extremely strict coal control measures and achieved remarkable results in recent years, the total coal consumption is expected to maintain a considerable scale for a considerable time in the future. In 2016, 10 months, the State department released a working scheme for controlling greenhouse gas emission, and proposed development strategies such as 'large-scale industrial demonstration of carbon capture, utilization and sequestration in the coal-based industry and oil and gas exploitation industry', 'promotion of carbon capture, utilization and sequestration pilot-plant demonstration in the industrial field', and the like.
China has a deep coal chemical industry foundation, and CCUS has good performance with the coal chemical industry of ChinaAnd (4) coupling property. If can remove CO generated in the chemical process2The raw material is further processed into high value-added chemicals or other important chemical intermediates, such as methanol, CO and the like, which is beneficial to realizing CO in China as early as possible2The goal of resource utilization and energy regeneration.
As a chemical raw material with an important added value, para-xylene (PX) has a large demand with the rapid development of downstream polyester industry. Toluene methylation, an atomic economic process for the synthesis of PX, has attracted continuing interest over the past few decades, and it has been widely investigated how methanol can methylate toluene over zeolite catalysts in an economically efficient manner.
In order to suppress the side effects of the alkylation reaction, researchers have modified zeolites with oxides of Mg, P, Si, etc. or have reacted at toluene/methanol molar ratios as high as 4:6, which results in low conversion of toluene. In addition, researchers often add appropriate amounts of water to the reactants to retard reaction catalyst deactivation. However, this further inhibits the methylation reaction of toluene, and is difficult to apply in industrial production. Therefore, it is very necessary to design a catalyst that suppresses the influence of these side reactions as much as possible. The novel reaction of the synthesis gas alkylated toluene is changed, the methanol generated in situ in the reaction can avoid the deposition of carbon at an active site, the dosage of the toluene is greatly reduced, and the conversion rate of the toluene is improved.
CN 110743609A reports that by using Zr-Zn composite oxide and HZSM-5 coupled catalyst, the selectivity of xylene can reach 92.4 percent by utilizing the high-temperature stability of ZZO, but the same is true for CO2The conversion rate and the toluene conversion rate are low, so that the yield of the p-xylene is low.
The challenge of the reaction lies in finding suitable reaction parameters, and because the optimal reaction temperature range of the alkylation of the toluene is 400-500 ℃ at high temperature due to the low temperature and high pressure which are favorable for the methanolization of the carbon dioxide, the main research and development direction is how to provide a metal oxide catalyst which can stably produce a methanol intermediate under the conditions of high temperature and high pressure.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation as well as a preparation method and application thereof.
The purpose of the invention can be realized by the following technical scheme:
the first purpose of the technical scheme is to protect a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation, wherein the catalyst is formed by mixing a Cu-based catalyst and an HZSM-5 molecular sieve;
the Cu-based catalyst is a mixed oxide composed of a Cu main body and a modified metal, and the mass ratio of the Cu-based catalyst to the surface HZSM-5 molecular sieve is 1: 3-3: 1;
the modified metal is one of Zr, Zn, Ce and Ti, wherein the content of Cu oxide is 50-95 wt%, and the content of the modified metal is 5-50 wt%.
Further preferably, the mass ratio of the Cu-based catalyst to the surface HZSM-5 molecular sieve is 1: 2-1: 1
Further, the HZSM-5 molecular sieve is modified by a surface Si coating method.
Further, the modified metal is Zr or Zn.
Further, the modified metal is preferably Zr.
Further, the SAR of the HZSM-5 molecular sieve is 12.5-125. Namely, the Si/Al element ratio is 12.5 to 125.
Further preferably, the SAR of the HZSM-5 molecular sieve is preferably 25-50.
The second purpose of the technical scheme is to protect a preparation method of the catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation, which comprises the following steps:
s1: weighing a proper amount of copper nitrate and zirconium nitrate solid according to a stoichiometric number, and dissolving the copper nitrate and the zirconium nitrate solid in ethanol to prepare an ethanol solution to obtain a solution I;
s2: preparing a precipitant solution, dropwise adding the solution I into the precipitant solution, and stirring for reaction to obtain a solution II;
s3: carrying out suction filtration on the solution II, then drying to obtain a precursor I, and roasting the precursor I to obtain a component I;
s4: and mixing the component I with the HZSM-5 molecular sieve modified by the surface Si coating method, grinding, and tabletting to obtain the finished catalyst.
Further, the Si coating method modified HZSM-5 molecular sieve comprises the following steps:
a1: adding HZSM-5 into a cyclohexane solution of TEOS, and soaking for 4 hours;
a2: removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at 550 ℃ for 4 hours under the air condition, wherein the heating rate is 1-10 ℃/min;
and (3) performing the steps of A1 and A2 for 1-5 times to finally obtain the Si coating method modified HZSM-5 molecular sieve.
Further, the total concentration of copper nitrate and zirconium nitrate in the ethanol solution in S1 was 1M, wherein the molar ratio of metal ions was Cu: zr is 0.5: 0.5-0.95: 0.05;
the concentration of the precipitant in the S2 is 0.5M, and the stirring reaction time is 0.5 h;
the roasting condition in S3 is roasting in air condition, the roasting temperature is 400 ℃, the roasting time is 3 hours, and the heating rate is 1-10 ℃/min.
Further preferably, the stoichiometric ratio Cu: zr is 9: 1.
Further, the precipitant in S2 is any one of oxalic acid, sodium hydroxide, ammonium carbonate, ammonia water, and hydrates thereof that is soluble in water.
Further, the pressure for tabletting is 20-40MPa, and then the obtained solid is ground to 40-60 meshes to obtain the finished catalyst.
The third purpose of the technical scheme is to protect the application of the catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation obtained by the preparation method, and the catalyst comprises the following steps:
and (3) an activation process: filling the catalyst into a fixed bed reactor, and adopting H with the concentration of 0-100 percent2/N2Mixed gas or 0% 100% H2Pretreating the/Ar mixed gas, wherein the pretreatment temperature is 250-500 ℃, the pressure is 0-2.0 MPa, and the activation time is 1-50 h;
the reaction process is as follows: after the activation process is finished, reducing the pressure in the fixed bed reactor to normal pressure, adjusting the temperature in the fixed bed reactor to 300-500 ℃, and introducing CO with the molar ratio of 0.5: 1-1: 5 into the fixed bed reactor2：H2Reacting the mixed gas with toluene, wherein the reaction pressure is 0.5-8.0MPa, and the gas phase space velocity GHSV of the fed material of the reaction is 1000h-1～50000h-1The liquid phase space velocity LHSV is 0.1h-1～3h-1。
Further preferably, the application process comprises the steps of:
and (3) an activation process: filling the catalyst into a fixed bed reactor, and adopting the concentration of N2Carrying out pretreatment, wherein the pretreatment temperature is 300 ℃, the pressure is 0MPa, and the activation time is 2 h;
the reaction process is as follows: adjusting the temperature in the fixed bed reactor to 360-420 ℃, and introducing a mixture of the raw materials in a molar ratio of 1: 3 CO2：H2Reacting the mixed gas with toluene, wherein the reaction pressure is 3.0-5.0 MPa, and the gas phase space velocity GHSV of the fed material of the reaction is 12000h-1The liquid phase space velocity LHSV is 1h-1。
Compared with the prior art, the invention has the following technical advantages:
1) the catalyst has the advantages that the metal oxide in the catalyst takes copper as a main body, has better methanol selectivity and reaction activity, and can provide sufficient methanol intermediate for the second step of toluene alkylation of the coupling reaction; the key innovation point of the technical scheme is that Si coating passivation treatment is carried out on the surface of the molecular sieve, so that the shape selection function of HZSM-5 is further improved, thermodynamic equilibrium distribution of xylene is broken, and the selectivity of a target product is improved.
2) Compared with the traditional toluene-methanol alkylation method, the reaction mode provided by the invention can reduce the side reaction of methanol to olefin caused by improper methanol/toluene feed ratio, and improve the production efficiency of xylene; meanwhile, the isomerization reaction of the dimethylbenzene can be inhibited, and the selectivity of the p-dimethylbenzene in the product is improved; the method obviously improves the reactivity of toluene alkylation and the selectivity of xylene, obtains good stability of the catalyst at high temperature, provides a new idea for carbon dioxide hydrogenation and toluene aromatic ring alkylation, and has good industrialization prospect.
3) The Cu salt and the precipitating agent used in the preparation of the catalyst precursor are cheap and easy to obtain, and the catalyst is prepared by a grinding and tabletting method, so that the method can improve the proximity between reaction sites.
4) The invention provides a method for preparing a coupling copper-based-molecular sieve catalyst by a physical mixing method, which has the advantages of simple preparation process, easily controlled conditions, short production period, no environmental pollution and capability of realizing batch production. With CO2The by-product olefin of the reaction is mainly distributed in the gas phase, and is easily separated from the heavy aromatic hydrocarbon product obtained by alkylation of toluene, so that the method has good economic benefit.
5) The catalyst shows good stability after 100h of continuous high-temperature reaction and does not show obvious inactivation tendency, so the technical scheme of the invention has good industrialization prospect.
Drawings
FIG. 1 shows the product analysis after 15h of run of a catalyst sample according to the invention.
Detailed Description
The present invention is further described below with reference to specific embodiments, and those skilled in the art can make various modifications to the embodiments without departing from the technical principles of the present invention, and these modifications should be construed as being within the scope of the present invention.
Aspects of the selection of the metal salt: in the examples, nitrate is exemplified, and other metal salts such as carbonate, chloride, sulfate and nitrite can achieve the effects of the present invention.
In terms of molecular sieve: in the examples, HZSM-5 is mainly used as an example for illustration, and other alkali metals such as Y-type molecular sieve, mordenite and the like can also achieve the effects of the present invention, wherein SAR has a large influence on the catalytic performance within a reasonable range exceeding the preferred value.
In the aspect of molecular sieve modification: in the experimental examples, the Si coating method is used for illustration, and other modified samples such as core-shell structure and ion exchange can achieve the effects of the invention.
The invention applies the iron-based catalyst modified by the auxiliary agent to the reaction of carbon dioxide hydrogenation and toluene aromatic naphthenic reaction, and the adopted evaluation method comprises the following steps:
under the temperature of 30-500 ℃ and the pressure of 0.5-8.0MPa, using H with the concentration of 0-100 percent2/N2Mixed gas or 0% -100% of H2Activating the/Ar mixed gas for 1-50 h. After activation, the temperature is adjusted to 300-500 ℃, and CO is added2:H2The mixed gas and the toluene in the ratio of 0.5: 1-1: 5 react in a fixed bed reactor filled with the catalyst, the reaction pressure P is 0.5-8.0MPa, and the space velocity GHSV of reaction feeding is 1000h-1～50000h-1(ii) a And controlling the reaction temperature of the cold hydrazine to be 5-10 ℃ for collecting heavy hydrocarbon components. H in gas-phase product at outlet of cold hydrazine2，N2，CO，CO2The components were analyzed on-line by gas chromatography using a TCD detector equipped with a TDX-01 packed column, and the light hydrocarbon component (C)1-C7) The content of (D) can be analyzed on-line by gas chromatography using a FID detector equipped with an HP-PLOT Q capillary column. After the reaction is finished, collecting heavy hydrocarbon components in the cold trap, weighing and measuring the volumes of the oil phase and the water phase respectively. The resulting liquid fraction was analyzed by gas chromatography-mass spectrometry (GC-MS) using an off-line FID detector equipped with an HP-5 capillary column. The results of the analysis of the gas phase product and the liquid phase product are normalized to obtain the selectivity of various components and CO2And toluene conversion.
The specific performance test process is as follows:
the catalyst samples in each example were weighed out to 416mg each and placed in a constant temperature zone of a fixed bed reactor. Before reaction, the catalyst is activated in situ at 300 deg.C and 0.1MPa in N atmosphere2Activation time was 2 h. After the activation is finished, the temperature is adjusted to 360 ℃, and the raw material gas is switched to 20% CO/60% H2/20％N2The pressure was adjusted to 3.0MPa, the feed gas flow was adjusted to 83.2ml/min, the feed toluene flow was adjusted to 0.008ml/min, and the reaction was started when the temperature and pressure were stable. The gas product was analyzed on-line by gas chromatography (FID, TCD), sampling every 1 hour. And after the reaction is finished, collecting liquid components (water phase and oil phase) through a cold trap, wherein the content of hydrocarbons and oxygen-containing organic compounds in the water phase product is extremely low and negligible, and the oil phase product is analyzed through offline gas chromatography-mass spectrometry (GC-MS).
Example 1
Preparation of 1ZrCu-1ZSM5-25 catalyst (mass ratio of ZrCu oxide to ZSM-5 molecular sieve 1: 1, SAR of ZSM-5 25)
Firstly, weighing Cu in a stoichiometric ratio: dissolving copper nitrate and zirconium nitrate solid with Zr being 9:1 in ethanol to prepare ethanol solution with cation concentration of 1M, marking as solution I, weighing oxalic acid to prepare 0.5M ethanol solution to obtain solution II, dropwise adding the solution I into the solution II at the speed of 3ml/min under the condition of continuously stirring, and reacting for 30min after dropwise adding is finished to obtain solution III. And (3) carrying out suction filtration on the solution III, putting a filter cake into a 120 ℃ oven overnight for 8h for drying to obtain a precursor I, grinding the precursor I, putting the ground precursor I into a muffle furnace, and calcining the ground precursor I for 3h at the temperature of 400 ℃ under the air condition at the heating rate of 5 ℃/min to obtain a precursor II. Adding HZSM-5 with SAR being 25 into a cyclohexane solution of TEOS, soaking for 4h, removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at air condition, wherein the roasting temperature is 550 ℃, the roasting time is 4 hours, the heating rate is 5 ℃/min, and repeating the steps for multiple times to finally obtain a precursor III. And mixing the precursor II and the precursor III in a ratio of 1: 1, grinding and tabletting, wherein the used pressure is 40MPa, and grinding the obtained solid to 40-60 meshes to obtain the finished catalyst. Specific values of the selectivity and the conversion rate of the catalyst are obtained by a performance test of the catalyst at 360 ℃, and the specific values are shown in table 1.
As can be seen from the performance data of the catalyst, the selectivity of p-xylene in the product reaches a higher level, the overall catalytic activity is better, and the performance is continuously stable within 100h in a stability test, which is shown in figure 1.
Example 2
Preparation of 1ZrCu-1ZSM5-25-HT catalyst (mass ratio of ZrCu oxide to ZSM-5 molecular sieve 1: 1, SAR of ZSM-5 25)
Firstly, weighing Cu in a stoichiometric ratio: dissolving copper nitrate and zirconium nitrate solid with Zr being 9:1 in ethanol to prepare ethanol solution with cation concentration of 1M, marking as solution I, weighing oxalic acid to prepare 0.5M ethanol solution to obtain solution II, dropwise adding the solution I into the solution II at the speed of 3ml/min under the condition of continuously stirring, and reacting for 30min after dropwise adding is finished to obtain solution III. And (3) carrying out suction filtration on the solution III, putting a filter cake into a 120 ℃ oven overnight for 8h for drying to obtain a precursor I, grinding the precursor I, putting the ground precursor I into a muffle furnace, and calcining the ground precursor I for 3h at the temperature of 400 ℃ under the air condition at the heating rate of 5 ℃/min to obtain a precursor II. Adding HZSM-5 with SAR being 25 into a cyclohexane solution of TEOS, soaking for 4h, removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at air condition, wherein the roasting temperature is 550 ℃, the roasting time is 4 hours, the heating rate is 5 ℃/min, and repeating the steps for multiple times to finally obtain a precursor III. And mixing the precursor II and the precursor III in a ratio of 1: 1, grinding and tabletting, wherein the used pressure is 40MPa, and grinding the obtained solid to 40-60 meshes to obtain the finished catalyst. Specific values of the selectivity and the conversion rate of the catalyst are obtained by a performance test of the catalyst at a high temperature of 420 ℃, and the specific values are shown in a table 1.
As can be seen from the performance data of the catalyst, the reaction activity of the catalyst is improved, but the selectivity of the xylene is greatly improved, so that the yield of the p-xylene is greatly improved, and the performance is still stable after 24 hours of reaction, see figure 1.
Example 3
Preparation of 1ZrCu-1ZSM5-50 catalyst (the mass ratio of ZrCu oxide to ZSM-5 molecular sieve is 1: 1, the SAR of ZSM-5 is 50)
Firstly, weighing Cu in a stoichiometric ratio: dissolving copper nitrate and zirconium nitrate solid with Zr being 9:1 in ethanol to prepare ethanol solution with cation concentration of 1M, marking as solution I, weighing oxalic acid to prepare 0.5M ethanol solution to obtain solution II, dropwise adding the solution I into the solution II at the speed of 3ml/min under the condition of continuously stirring, and reacting for 30min after dropwise adding is finished to obtain solution III. And (3) carrying out suction filtration on the solution III, putting a filter cake into a 120 ℃ oven overnight for 8h for drying to obtain a precursor I, grinding the precursor I, putting the ground precursor I into a muffle furnace, and calcining the ground precursor I for 3h at the temperature of 400 ℃ under the air condition at the heating rate of 5 ℃/min to obtain a precursor II. Adding HZSM-5 with SAR being 50 into a cyclohexane solution of TEOS, soaking for 4h, removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at air condition, wherein the roasting temperature is 550 ℃, the roasting time is 4 hours, the heating rate is 5 ℃/min, and repeating the steps for multiple times to finally obtain a precursor III. And mixing the precursor II and the precursor III in a ratio of 1: 1, grinding and tabletting, wherein the used pressure is 40MPa, and grinding the obtained solid to 40-60 meshes to obtain the finished catalyst. Specific values of the selectivity and conversion of the catalyst were obtained by performance testing of the catalyst at 360 ℃, see table 1.
Example 4
Preparation of 2ZrCu-1ZSM5-25 catalyst (mass ratio of ZrCu oxide to ZSM-5 molecular sieve 1: 2, SAR of ZSM-5 25)
Firstly, weighing Cu in a stoichiometric ratio: dissolving copper nitrate and zirconium nitrate solid with Zr being 9:1 in ethanol to prepare ethanol solution with cation concentration of 1M, marking as solution I, weighing oxalic acid to prepare 0.5M ethanol solution to obtain solution II, dropwise adding the solution I into the solution II at the speed of 3ml/min under the condition of continuously stirring, and reacting for 30min after dropwise adding is finished to obtain solution III. And (3) carrying out suction filtration on the solution III, putting a filter cake into a 120 ℃ oven overnight for 8h for drying to obtain a precursor I, grinding the precursor I, putting the ground precursor I into a muffle furnace, and calcining the ground precursor I for 3h at the temperature of 400 ℃ under the air condition at the heating rate of 5 ℃/min to obtain a precursor II. Adding HZSM-5 with SAR being 25 into a cyclohexane solution of TEOS, soaking for 4h, removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at air condition, wherein the roasting temperature is 550 ℃, the roasting time is 4 hours, the heating rate is 5 ℃/min, and repeating the steps for multiple times to finally obtain a precursor III. And mixing the precursor II and the precursor III in a ratio of 1: 2, grinding and tabletting, wherein the used pressure is 40MPa, and grinding the obtained solid to 40-60 meshes to obtain the finished catalyst. Specific values of the selectivity and conversion of the catalyst were obtained by performance testing of the catalyst at 360 ℃, see table 1.
Example 5
Preparation of 1ZrCu-1ZSM5-25-HL catalyst (the mass ratio of ZrCu oxide to ZSM-5 molecular sieve is 1: 1, the SAR of ZSM-5 is 25)
Firstly, weighing Cu in a stoichiometric ratio: dissolving copper nitrate and zirconium nitrate solid with Zr being 9:1 in ethanol to prepare ethanol solution with cation concentration of 1M, marking as solution I, weighing oxalic acid to prepare 0.5M ethanol solution to obtain solution II, dropwise adding the solution I into the solution II at the speed of 3ml/min under the condition of continuously stirring, and reacting for 30min after dropwise adding is finished to obtain solution III. And (3) carrying out suction filtration on the solution III, putting a filter cake into a 120 ℃ oven for 8h overnight for drying to obtain a precursor I, grinding the precursor I, putting the ground precursor I into a muffle furnace, and calcining the ground precursor I for 3h at the temperature of 400 ℃ under the air condition at the temperature rise rate of 5 ℃/min to obtain a precursor II. Adding HZSM-5 with SAR being 25 into a cyclohexane solution of TEOS, soaking for 4h, removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at air condition, wherein the roasting temperature is 550 ℃, the roasting time is 4 hours, the heating rate is 5 ℃/min, and repeating the steps for multiple times to finally obtain a precursor III. And mixing the precursor II and the precursor III in a ratio of 1: 1, grinding and tabletting, wherein the used pressure is 40MPa, and grinding the obtained solid to 40-60 meshes to obtain the finished catalyst. The specific values of the selectivity and the conversion rate of the catalyst are obtained by a performance test that the gas-phase space velocity of the catalyst is unchanged and the liquid-phase space velocity is increased by 2.5 times under the condition of 360 ℃, and the specific values are shown in table 1.
Comparative example 1
This comparative example uses the catalytic data in document [1 ].
Compared with the document [1]]See table 1 for catalytic data, performance. It can be seen that the overall catalytic activity exhibited by the ZnZnZnOx-ZSM 5 catalysts was significantly lower than that exhibited by the catalysts of examples 1-5 of the present invention. The reason is that of examples 1 to 5The ZrCu oxide can generate a methanol intermediate more quickly under a high-temperature condition, so that the catalyst consumes more toluene in a subsequent alkylation reaction, and a higher toluene conversion rate is achieved. At the same time, compared with the literature, by CO2The conversion rate can be seen that the methanol produced by the catalyst is excessive, the excessive methanol is dehydrated in the ZSM-5 molecular sieve to generate olefin, the olefin is discharged through tail gas and does not appear in a liquid phase product, and the CO is improved2The utilization ratio of (2). In addition, compared with the literature, the catalyst in the experimental example 5 has the advantages that the toluene conversion rate is still basically consistent after the gas phase space velocity is unchanged and the liquid phase space velocity is increased by 2.5 times, and the selectivity of the dimethylbenzene is higher, so that the yield of the dimethylbenzene is increased by nearly three times. In a high-temperature experiment, the catalyst can still stably run at 420 ℃, and has no obvious inactivation after running for 100 hours at 360 ℃.
Table 1: the catalyst activity in each of the examples and comparative examples is shown in the table, wherein the literature does not refer to specific values.
Figure BDA0003002039020000091
Figure BDA0003002039020000101
Wherein:
[1] data from zuo.j.et al.science Advances,2020,6(34), eaba 5433;
comparative example 2
CN110496640A discloses a catalyst for synthesizing paraxylene, a preparation method and application thereof. The catalyst comprises zinc-aluminum spinel oxide and a modified acidic molecular sieve in a mass ratio of 1: 5-5: 1, wherein the zinc-aluminum spinel oxide optionally contains at least one other element selected from chromium, zirconium, copper, manganese, indium, gallium and silicon, and the modified acidic molecular sieve is selected from a modified acidic ZSM-5 molecular sieve, a modified acidic ZSM-11 molecular sieve and a mixture thereof.
Compared with the comparative example 2, the technical scheme has CO2High conversion rate, high xylene yield and high utilization rate of raw materials. The introduction of toluene promotes the movement of methanol in the product in the direction of the xylene production route, pulling CO2The reaction is balanced, and the proportion of CO in the product is reduced; the introduction of toluene in the product greatly simplifies the CO2The path for producing dimethylbenzene can reach the dimethylbenzene yield of 0.75gX·gcat -1·h-1Much higher than 0.04g in comparative example 2X·gcat -1·h-1While CO in the scheme2The proportion for the alkylation can be up to approximately 50%, compared with the conversion of CO in comparative example 22The ratio for the production of xylene was only 30%, so the performance of this scheme was superior to that of comparative example 2 in terms of xylene production.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. The catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation is characterized in that the catalyst is formed by mixing a Cu-based catalyst and an HZSM-5 molecular sieve;
the Cu-based catalyst is a mixed oxide composed of a Cu main body and a modified metal, and the mass ratio of the Cu-based catalyst to the surface HZSM-5 molecular sieve is 1: 3-3: 1;
the modified metal is one of Zr, Zn, Ce and Ti, wherein the content of Cu oxide is 50-95 wt%, and the content of the modified metal is 5-50 wt%.
2. The catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation according to claim 1, wherein the HZSM-5 molecular sieve is a surface Si coating modified HZSM-5 molecular sieve.
3. The catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation according to claim 1, wherein the modifying metal is Zr or Zn.
4. The catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation according to claim 1, wherein the HZSM-5 molecular sieve has SAR of 12.5-125.
5. A preparation method of a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation is characterized by comprising the following steps:
s1: weighing a proper amount of copper nitrate and zirconium nitrate solid according to a stoichiometric number, and dissolving the copper nitrate and the zirconium nitrate solid in ethanol to prepare an ethanol solution to obtain a solution I;
s2: preparing a precipitant solution, dropwise adding the solution I into the precipitant solution, and stirring for reaction to obtain a solution II;
s3: carrying out suction filtration on the solution II, then drying to obtain a precursor I, and roasting the precursor I to obtain a component I;
s4: and mixing the component I with the HZSM-5 molecular sieve modified by the surface Si coating method, grinding, and tabletting to obtain the finished catalyst.
6. The method for preparing the catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation according to claim 5, wherein the Si coating method modified HZSM-5 molecular sieve comprises the following steps:
a1: adding HZSM-5 into a cyclohexane solution of TEOS, and soaking for 4 hours;
a2: removing cyclohexane by rotary evaporation at 80 ℃, drying and roasting at 550 ℃ for 4 hours under the air condition, wherein the heating rate is 1-10 ℃/min;
and (3) performing the steps of A1 and A2 for 1-5 times to finally obtain the Si coating method modified HZSM-5 molecular sieve.
7. The method for preparing a catalyst for carbon dioxide hydrogenation and toluene aromatic ring alkylation according to claim 5, wherein the total concentration of copper nitrate and zirconium nitrate in the ethanol solution in S1 is 1M, and the molar ratio of metal ions is Cu: zr is 0.5: 0.5-0.95: 0.05;
the concentration of the precipitant in the S2 is 0.5M, and the stirring reaction time is 0.5 h;
the roasting condition in S3 is roasting in air condition, the roasting temperature is 400 ℃, the roasting time is 3 hours, and the heating rate is 1-10 ℃/min.
8. The method for preparing a catalyst for aromatic ring alkylation of carbon dioxide hydrogenation and toluene according to claim 5, wherein the precipitant in S2 is any one of oxalic acid, sodium hydroxide, ammonium carbonate, ammonia water and its hydrate, which is soluble in water.
9. The use of the preparation method according to claim 5 for preparing a catalyst for the hydrogenation of carbon dioxide and the aromatic ring alkylation of toluene, comprising the following steps:
and (3) an activation process: filling the catalyst into a fixed bed reactor, and adopting H with the concentration of 0-100 percent2/N2Mixed gas or 0-100% of H2Pretreating the/Ar mixed gas, wherein the pretreatment temperature is 250-500 ℃, the pressure is 0-2.0 MPa, and the activation time is 1-50 h;
the reaction process is as follows: after the activation process is finished, reducing the pressure in the fixed bed reactor to normal pressure, adjusting the temperature in the fixed bed reactor to 300-500 ℃, and introducing CO with the molar ratio of 0.5: 1-1: 5 into the fixed bed reactor2：H2Reacting the mixed gas with toluene, wherein the reaction pressure is 0.5-8.0MPa, and the gas phase space velocity GHSV of the fed material of the reaction is 1000h-1～50000h-1The liquid phase space velocity LHSV is 0.1h-1～3h-1。
10. The use of the catalyst for aromatic ring alkylation of carbon dioxide with toluene according to claim 9, comprising the steps of:
and (3) an activation process: filling the catalyst into a fixed bed reactor, and adopting the concentration of N2Carrying out pretreatment, wherein the pretreatment temperature is 300 ℃, the pressure is 0MPa, and the activation time is 2 h;
the reaction process is as follows: adjusting the temperature in the fixed bed reactor to 360-420 ℃, and introducing a mixture of the raw materials in a molar ratio of 1: 3 CO2：H2Reacting the mixed gas with toluene, wherein the reaction pressure is 3.0-5.0 MPa, and the gas phase space velocity GHSV of the fed material of the reaction is 12000h-1The liquid phase space velocity LHSV is 1h-1。
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