CN109718764B

CN109718764B - Noble metal catalyst for preparing propylene by propane dehydrogenation and preparation and application thereof

Info

Publication number: CN109718764B
Application number: CN201711020751.XA
Authority: CN
Inventors: 李为臻; 任国庆; 刘凯鹏; 杨静怡; 张涛
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2017-10-27
Filing date: 2017-10-27
Publication date: 2022-04-12
Anticipated expiration: 2037-10-27
Also published as: CN109718764A

Abstract

The invention belongs to the field of catalysts and preparation thereof, and relates to a magnesium-gallium composite oxide supported noble metal catalyst, and preparation and application thereof, in particular to a magnesium-gallium composite oxide supported noble metal catalyst for propane dehydrogenation to prepare propylene and a preparation method thereof. The catalyst is prepared from magnesium gallium composite oxide MgO. xGa₂O₃(0.5<x<2) And a noble metal active component with the loaded mass fraction of 0.01-5wt%, wherein the active component comprises: one or more of Rh, Ir and Pt. The catalyst shows high propylene selectivity and high-temperature sintering resistance to propane dehydrogenation reaction in a fixed bed reactor at the temperature of 550-700 ℃, and has the advantage of high cyclic carbon burning regeneration stability.

Description

Noble metal catalyst for preparing propylene by propane dehydrogenation and preparation and application thereof

Technical Field

The invention relates to an anti-sintering noble metal catalyst for high-selectivity generation of propylene by propane dehydrogenation, preparation and application thereof, and a method for high-selectivity preparation of propylene by propane dehydrogenation by using the catalyst.

Background

Propylene is an important basic chemical raw material in industry, and is widely used for producing chemical products such as polypropylene, acrylonitrile, acrylic acid, propylene oxide, carbonyl alcohol and the like. Propylene is currently produced mainly by three routes: a process of preparing ethylene and propylene as byproducts by naphtha cracking, a process of preparing olefin (MTO) from methanol and a process of preparing propylene by Propane Dehydrogenation (PDH). The yield of propylene, which is the byproduct of naphtha cracking, is about 80% of the total yield of propylene, but the process is not a process for producing propylene as a target product, so that the process is difficult to meet the demand as the demand of propylene increases. Therefore, the process of producing propylene in a targeted manner will become an important way to expand the source of propylene. Propane is an important component of natural gas, and with the discovery and exploitation of a large amount of shale gas, the process of directly generating propylene by propane dehydrogenation becomes an important process for producing propylene.

The propane dehydrogenation reaction is a strongly endothermic reaction. To achieve higher propane conversion, the reaction generally needs to be carried out at high temperatures above 550 degrees. But the excessive reaction temperature is easy to cause the cracking reaction of propane to generate low-carbon hydrocarbon, so that the selectivity of propylene is reduced; meanwhile, the catalyst can be sintered and surface carbon deposition is inactivated under the high-temperature condition. Therefore, the key point of the propane dehydrogenation technology is to prepare a catalyst with high propylene selectivity, high sintering resistance and carbon deposition resistance.

The current commercial propane dehydrogenation catalysts are mainly platinum-series and chromium-series catalysts, and are Pt/Al modified by Sn, K or Li adopted by the Oleflex process of UOP₂O₃And CrO adopted in the Catofin process of ABB Lummus₃/Al₂O₃As a representative. Wherein, the chromium catalyst is easy to generate surface carbon deposition and is quickly deactivated in the dehydrogenation process, frequent carbon burning regeneration is needed, and chromium has great influence on human health and environment, so the utilization of the chromium catalyst is limited; the platinum catalyst has the advantages of higher propane dehydrogenation activity, low pollution and the like, and becomes a hot spot of the propane dehydrogenation catalyst.

However, Pt-based catalysts also have more problems, mainly the low propylene selectivity of single Pt catalysts and the sintering deactivation of Pt nanoparticles. In order to improve the selectivity of propylene, the current common strategy is to modulate the geometric structure and electronic properties of Pt by adding auxiliaries such as Sn, Cu, Ga, Zn, Li, K, V, etc., for example, CN101898130B discloses a propane dehydrogenation catalyst with platinum group metal as an active component and tin as an auxiliary, and the addition of tin auxiliary significantly improves the selectivity and reaction stability of propylene. Bert et Al (Angew. chem. int. Ed.2014,53, 9251-one 9256) report Pt/Al modified with Ga promoter₂O₃The addition of the catalyst and the Ga auxiliary agent can obviously improve the Pt/Al with extremely low Pt loading₂O₃Propane conversion and propylene selectivity of the catalyst. Although the method for modifying the auxiliary agent can obviously improve the propylene selectivity of the platinum-based catalyst, the auxiliary agent is easy to reduce and precipitate under the high-temperature reaction condition, and the performance of the catalyst is further influenced. CN101884922A discloses a sol-gel method, in which a tin component is introduced into an aluminum sol, and after drying and forming, active components platinum and other metal additives are impregnated, so as to slow down the reduction precipitation of the tin component, but the preparation process of the catalyst is complicated, and the effect of inhibiting tin precipitation is limited. On the other hand, in order to improve the anti-sintering performance of the propane dehydrogenation platinum-based catalyst, an acidic porous material is often used as a carrier, and the anti-sintering performance of Pt is realized through the limited-area action of a pore channel. CN106311311A discloses a group IIB metal or alkaline earth metal as an auxiliary agent modified mesoporous molecular sieve supported platinum catalyst, which shows good propane dehydrogenation stability for propane dehydrogenation reaction, and can still maintain good propane dehydrogenation conversion rate and improved propylene selectivity after 100 hours of reaction.

It can be seen that, in the prior art, platinum is mostly used as an active component, and an auxiliary agent is added to modulate the geometric structure and the electronic property of the catalyst, so as to obtain high propylene selectivity; porous materials are used as carriers in order to obtain high sintering resistance.

Disclosure of Invention

The invention discloses a magnesium-gallium composite oxide loaded anti-sintering noble metal catalyst for a reaction of generating propylene with high selectivity by propane dehydrogenation, and solves the problems of low propylene selectivity and high-temperature sintering of noble metal of the existing propane dehydrogenation platinum-based catalyst under the condition of no addition of an auxiliary agent. Provides a preparation method of the catalyst and a method for preparing propylene with high selectivity by using the catalyst in propane dehydrogenation.

In order to achieve the purpose, the invention provides a noble metal-supported catalyst for preparing propylene magnesium gallium composite oxide by propane dehydrogenation, which is characterized in that a carrier of the catalyst is magnesium gallium composite oxide MgO. xGa₂O₃(0.5<x<2) The active component is any one or more than two of Rh, Ir and Pt, wherein the weight percentage of the noble metal is 0.01-5wt%, and the optimized weight percentage is 0.1-1 wt%.

The preparation method of the catalyst comprises the following steps:

1) preparing a magnesium-gallium composite oxide carrier: magnesium-containing metal salt precursor and gallium-containing metal salt precursor are mixed according to the proportion of Mg: the Ga molar ratio is 1: 2x (x is more than 0.5 and less than 2) is mixed and dissolved in water, the precursor is nitrate or acetate of magnesium or gallium to form 0.01-5mol/L solution, a proper amount of ammonia water is added, the pH value is adjusted to be 8-10, the mixture is stirred for 0.5-24 hours, the mixture is filtered, a filter cake is dried for 2-24 hours at the temperature of 90-150 ℃, and then the mixture is roasted for 2-12 hours at the temperature of 400-600 ℃, so as to obtain the magnesium-gallium composite oxide carrier;

2) preparing a catalyst: the preparation method comprises the steps of dipping a magnesium gallium composite oxide carrier into a precursor solution of active components Rh, Ir and Pt with certain content, wherein the precursor is chloride or nitrate of noble metal and the like, stirring for 2-24 hours, then filtering, washing, drying for 2-24 hours at 90-150 ℃, then roasting for 2-12 hours at 400-600 ℃ in an air atmosphere, and then reducing for 2-12 hours at 500-800 ℃ in a hydrogen atmosphere to obtain the catalyst with the weight percentage content of the noble metal of 0.01-5wt%, wherein the particle size of the active components is distributed from single atom to 3 nm. The catalyst has high sintering resistance, and after the catalyst is roasted for 24 hours at 800 ℃ in an air atmosphere, the particle size of the active component still exists in a nano particle form from a single atom to 3nm or below.

The invention also provides a high-selectivity propane dehydrogenation preparationA process for producing propylene. The method specifically comprises the following steps: the catalyst is adopted, a fixed bed reaction device is utilized, propane and hydrogen with the volume ratio of 1:1 are taken as raw materials, and the space velocity is 3000-50000h^-1The pressure is 0.1-0.2Mpa, and the reaction is 550-700 ℃. The results show that the method can obtain the propane conversion rate close to the equilibrium conversion rate and the propylene selectivity of more than 90 percent, and the catalyst still shows high propane conversion rate and propylene selectivity after multiple carbon burning cycles of regeneration.

Drawings

FIG. 1 shows Rh/MgO. Ga prepared by examples 2, 3 and 4 of the process of the present invention₂O₃(a)，Ir/MgO·Ga₂O₃(b) And Pt/MgO & Ga₂O₃(c) Electron microscopy of the three catalysts.

FIG. 2 shows Rh/MgO. Ga prepared by the method of example 2 of the present invention₂O₃The catalyst was subjected to the conversion of propane and the selectivity to propylene obtained by applying the reaction of example 1.

FIG. 3 shows Ir/MgO. Ga prepared in example 3 by the method of the present invention₂O₃The catalyst was subjected to the conversion of propane and the selectivity to propylene obtained by applying the reaction of example 1.

FIG. 4 shows Pt/MgO. Ga prepared by example 4 of the method of the present invention₂O₃The catalyst was subjected to the conversion of propane and the selectivity to propylene obtained by applying the reaction of example 1.

FIG. 5 is a diagram of Pt/Al prepared in comparative example 1 by the method of the present invention₂O₃The catalyst was subjected to the conversion of propane and the selectivity to propylene obtained by applying the reaction of example 1.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and detailed description, but the invention is not limited thereto.

Example 1

Example 1 preparation of magnesium gallium composite oxide MgO. xGa by the method of the present invention₂O₃(x ═ 1). The method comprises the following specific steps: (1) respectively weighing 0.05 mol of magnesium nitrate hexahydrate and 0.10mol of gallium nitrate nonahydrate, dissolving in 500mL of water, stirring to dissolveForming 0.10mol/L magnesium nitrate and 0.20mol/L gallium nitrate solution; (2) then adding a proper amount of 10 wt.% ammonia water, adjusting the pH value to 9, stirring for 12 hours, and filtering; (3) drying the filter cake at 120 deg.C for 12 hr, and calcining at 600 deg.C for 5 hr to obtain MgO & Ga₂O₃A magnesium gallium composite oxide carrier.

Example 2

Embodiment 2 adopts the method provided by the present invention, and adopts the magnesium-gallium composite oxide prepared in embodiment 1 as a carrier to prepare a magnesium-gallium composite oxide supported highly dispersed rhodium catalyst. The specific method comprises the following steps: 5.0g of MgO. Ga are weighed₂O₃The carrier is added into 150ml rhodium chloride aqueous solution containing 0.05g rhodium, stirred for 2h at room temperature, filtered, washed, the obtained solid is dried for 2h at 150 ℃, roasted for 5h in the air at 600 ℃, and then reduced for 2h at 800 ℃ in pure hydrogen. Obtaining a highly dispersed rhodium catalyst loaded on the magnesium-gallium composite oxide, which is recorded as Rh/MgO & Ga₂O₃。

Example 3

Example 3 a highly dispersed iridium catalyst supported on a magnesium-gallium composite oxide was prepared using the magnesium-gallium composite oxide prepared in example 1 as a carrier by the method provided by the present invention. The specific method comprises the following steps: 5.0g of MgO. Ga are weighed₂O₃Adding the carrier into 150ml of chloroiridic acid aqueous solution containing 0.15g of iridium, stirring for 24h at room temperature, filtering, washing, drying the obtained solid at 90 ℃ for 24h, roasting in air at 400 ℃ for 12h, and reducing in pure hydrogen at 600 ℃ for 5 h. Obtaining the Mg-Ga composite oxide loaded high-dispersion iridium catalyst which is recorded as Ir/MgO & Ga₂O₃。

Example 4

Example 4 a high-dispersion platinum catalyst supported on a magnesium-gallium composite oxide was prepared using the magnesium-gallium composite oxide prepared in example 1 as a carrier by the method provided by the present invention. The specific method comprises the following steps: 5.0g of MgO. Ga are weighed₂O₃The carrier was added to 150ml of an aqueous solution of chloroplatinic acid containing 0.005g of platinum, stirred at room temperature for 12 hours, filtered, washed, and the resulting solid was dried at 120 ℃ for 12 hours, calcined at 500 ℃ in air for 10 hours, and then reduced in pure hydrogen at 500 ℃ for 12 hours. Obtaining the magnesium-gallium composite oxide with high loadDispersed platinum catalyst, designated as Pt/MgO & Ga₂O₃。

Comparative example 1

Comparative example 1a conventional equal volume impregnation method was used. Selecting the specific surface area of more than 100m²Commercial gamma-Al of/g₂O₃Weighing 5.0g of the gamma-Al as carrier₂O₃Added to an aqueous chloroplatinic acid solution containing 0.05g of platinum prepared in accordance with the water absorption amount thereof, ultrasonically shaken, stirred for 1 hour, dried at room temperature for 12 hours, and then dried at 80 ℃ for 12 hours to obtain a catalyst precursor. The catalyst precursor is roasted in air at 500 deg.c for 5 hr and reduced in pure hydrogen at 500 deg.c for 2 hr. To obtain gamma-Al₂O₃Supported highly dispersed platinum catalyst, designated Pt/Al₂O₃。

Catalyst application example 1

Rh/MgO. Ga prepared in example 2 was charged into a fixed bed reactor₂O₃Catalyst 0.3g (20-40 mesh) was diluted with 3.0g quartz sand (20-40 mesh). The catalyst is first pretreated, i.e. reduced in pure hydrogen at 600 ℃ for 2 hours. Carrying out reaction after pretreatment, wherein the reaction conditions are as follows: the mass space velocity of the propane feed is controlled to be 12000h^-1(ii) a Hydrogen is taken as diluent gas, and the volume ratio of the hydrogen to the propane is 1: 1; the reaction temperature is 580 ℃ and the reaction pressure is 0.1 MPa.

Catalyst application examples 2 to 4

According to the method of application example 1, except that Rh/MgO. Ga₂O₃Catalyst is replaced by Ir/MgO & Ga₂O₃、Pt/MgO·Ga₂O₃And Pt/Al₂O₃Respectively carrying out the reaction for preparing propylene by propane dehydrogenation.

Claims

1. A noble metal catalyst for preparing propylene by propane dehydrogenation is characterized in that a carrier of the catalyst is magnesium-gallium composite oxide MgOxGa₂O₃（0.5<x<2) The active component is any one or more than two of Rh, Ir and Pt, wherein the weight percentage of the noble metal is 0.01-5 wt%;

the preparation method of the catalyst comprises the following steps:

1) preparing a magnesium-gallium composite oxide carrier: magnesium-containing metal salt precursor and gallium-containing metal salt precursor are mixed according to the proportion of Mg: the Ga molar ratio is 1: 2x (0.5< x <2) is mixed and dissolved in water, the precursor is one or more than two of nitrate or acetate of magnesium or gallium to form 0.01-5mol/L solution, a proper amount of ammonia water is added, the pH value is adjusted to 8-10, the mixture is stirred for 0.5-24 hours, the mixture is filtered, the filter cake is dried for 2-24 hours at the temperature of 90-150 ℃, and then the mixture is roasted for 2-12 hours at the temperature of 400-600 ℃, so as to obtain the magnesium-gallium composite oxide carrier;

2) preparing a catalyst: soaking a magnesium-gallium composite oxide carrier in a precursor solution with the mass concentration of 0.0001-50 g/L of active components Rh, Ir and Pt, wherein the precursor is one or more than two of chlorides or nitrates of the noble metals, stirring for 2-24 hours, filtering, washing, drying at 90-150 ℃ for 2-24 hours, and then 400-600-inch air atmosphere^oC roasting for 2-12 hours, then at 500-^oReducing for 2-12 hours under the atmosphere of C hydrogen to obtain the catalyst with the weight percentage of the noble metal of 0.01-5wt percent.

2. The catalyst of claim 1, wherein: the weight percentage of the noble metal in the catalyst is 0.1-1 wt%.

3. A method of preparing the catalyst of claim 1, wherein:

2) preparing a catalyst: soaking the magnesium-gallium composite oxide carrier in active components Rh, Ir and Pt with the mass concentration of 0.0001-50 g/L of precursor solution, wherein the precursor is one or more than two of the chlorides or nitrates of the noble metals, is stirred for 2-24 hours, then is filtered and washed, is dried for 2-24 hours at 90-150 ℃, and then is dried under the air atmosphere of 400-^oC roasting for 2-12 hours, then at 500-^oReducing for 2-12 hours under the atmosphere of C hydrogen to obtain the catalyst with the weight percentage of the noble metal of 0.01-5wt percent.

4. Use of a catalyst according to claim 1, wherein: the method is applied to the reaction of preparing propylene by propane dehydrogenation, and specifically comprises the following steps: the catalyst is adopted, a fixed bed reaction device is utilized, propane and hydrogen with the volume ratio of 1:1 are taken as raw materials, and the space velocity is 3000-50000h^-1The reaction pressure is 0.001-0.2Mpa, the reaction temperature is 550-^oC。

5. Use of a catalyst according to claim 4, wherein: the reaction pressure is 0.1-0.2 MPa.

6. Use of a catalyst according to claim 4, characterized in that: the catalyst is firstly pretreated, namely, reduction treatment is carried out in pure hydrogen at the temperature of 500-700 ℃, and the treatment time is 2-5 h.

7. Use of a catalyst according to claim 6, characterized in that: the catalyst is firstly pretreated, namely, reduction treatment is carried out in pure hydrogen at 550-600 ℃.