CN113441137A

CN113441137A - Preparation method of catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in mono-olefin-rich atmosphere, product and application

Info

Publication number: CN113441137A
Application number: CN202110717977.5A
Authority: CN
Inventors: 路军岭; 夏玉佳; 刘放
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2021-09-28

Abstract

The invention discloses a preparation method of a high-selectivity and high-stability catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in a mono-olefin-rich atmosphere, and a product and application thereof. The catalyst comprises a carrier, an active metal component Pd, an auxiliary agent metal component Au, Ag or Cu and a specific amount of gallium oxide wrapping layer, wherein the wrapping layer is wrapped on the surface of a bimetal supported catalyst precursor of the active metal component and the auxiliary agent metal component which are loaded on the carrier in a discontinuous mode. The high-selectivity hydrogenation catalyst provided by the invention can show excellent catalytic performance in the selective hydrogenation reaction of acetylene or 1, 3-butadiene in a monoolefin-rich atmosphere, can realize the complete conversion of acetylene or 1, 3-butadiene at a mild temperature, can keep the high selectivity (more than 95%) of ethylene or butylene when the conversion rate reaches 100%, and can effectively inhibit carbon deposition, so that the high-selectivity hydrogenation catalyst can be kept stable for a long time.

Description

Preparation method of catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in mono-olefin-rich atmosphere, product and application

Technical Field

The invention relates to a preparation method of a wrapped bimetal supported catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in a mono-olefin-rich atmosphere, and a product and application thereof.

Background

In petrochemical industry, steam cracking of naphtha produces a rich low chain mono-olefin, but often contains small amounts of diolefins or acetylenes in this olefin stream; in downstream olefin polymerization processes, dienes or alkynes tend to adsorb onto the surface of the polymerization catalyst more readily than mono-olefins and render the catalyst poisoned and ineffective. Therefore, the reduction of the content of diolefin or alkyne to below 10ppm is an essential step. At present, the problem is mainly solved by using selective hydrogenation of diene and alkyne to generate mono-olefin, diene or alkyne is selectively converted into mono-olefin by selecting a proper catalyst, and the method not only removes the diene or alkyne but also realizes the maximum utilization rate of raw materials. Among them, selective hydrogenation of 1, 3-butadiene in olefin-rich hydrocarbon and selective hydrogenation of acetylene in ethylene-rich hydrocarbon have been widely studied.

At present, catalysts for preferential hydrogenation of acetylene in an ethylene-rich atmosphere and preferential hydrogenation of 1, 3-butadiene in a propylene-rich atmosphere are mainly classified into the following types:

(a)palladium-based single metal catalyst: pd-based catalysts are widely used in hydrogenation reactions due to their hydrogenation activity to double and triple bonds, wherein the removal of small amounts of 1, 3-butadiene and acetylene from mono-olefins produced by naphtha cracking by selective hydrogenation is an industrially important application of Pd-based catalysts. However, due to the competition of mono-olefin hydrogenation reaction, people find that when the conversion rate of 1, 3-butadiene and acetylene is high, the selectivity of corresponding mono-olefin is rapidly reduced, and the maximum utilization rate of raw materials is difficult to realize. For example, chinese patent application CN101862653B mentions that Pd nanoparticles are supported on an alumina carrier with a Pd loading of 0.035%. When the acetylene conversion is close to 100%, the selectivity of ethylene is only 24%, and the selectivity is very limited, and the maximum utilization rate of raw materials cannot be realized if the acetylene conversion is applied in industry. As another example, in Chinese patent application CN109092302B, Pd nano-particles are mentioned to be loaded on an alumina carrier, and the loading amount of Pd is mentionedIs 0.5%. As the 1, 3-butadiene approaches full conversion, there is also a slight loss of 1-butene originally in the reaction gas. In addition, Pd-based single metal catalysts are relatively unstable and tend to deactivate the catalyst during the reaction by forming hydrocarbon and carbon deposits.

(b)Palladium-based bimetallic catalyst: a common method to improve the selectivity of ethylene over supported Pd nanocatalysts is by adding a second metal to form a Pd-based bimetallic catalyst. Compared with Pd-based single metal catalysts, the catalyst improves the selectivity of the Pd-based single metal catalyst under high conversion rate by sacrificing the activity of the Pd-based single metal catalyst, and the activity and the selectivity cannot be obtained at the same time. For example, in the case of the supported PdCu catalyst mentioned in chinese patent application CN111013603A, when the ratio of hydrogen to acetylene is 10, the conversion rate of acetylene close to 100% can be achieved at 200 ℃, and the ethylene selectivity under this condition is 70.8%, compared with the ethylene selectivity of 39.1% in the Pd-based single metal catalyst in this patent, the selectivity improvement effect is limited and the catalyst activity is low. Synthesis of Ga by hydrothermal method in Chinese patent application CN110935445A₂O₃A carrier on which Pd is supported by an impregnation method, and passing H₂Pretreatment to form Pd₂Ga/Ga₂O₃The bimetallic catalyst has the ethylene selectivity up to 82% under the condition that the acetylene conversion rate is 95%, but the activity of the bimetallic catalyst is poor, and the 95% conversion rate can be realized only under the temperature of 200 ℃. In the chinese patent application CN109092302B, it is mentioned that PdLa (or PdCe, PdLaCe) nanoparticles are loaded on an alumina carrier, and when 1, 3-butadiene is nearly completely converted at 40 ℃, there is a slight loss of about 3% of original 1-butene in the reaction gas, and the selectivity improvement is very limited, and 1-butene in the original reaction gas is also hydrogenated. When the selectivity of the bimetallic catalyst is improved, the activity is reduced, the activity and the selectivity cannot be simultaneously considered, and the improvement of the selectivity is limited.

(c)Oxide-coated palladium-based single metal catalyst: for palladium-based catalysts, in addition to adding a second metal to increase its selectivity, it is also often accomplished by an oxide coating process. Lourfield teacher subject group of Chinese science and technology university, using atomic layer deposition technologyBy using alumina to Pd/Al₂O₃The Pd/Al is improved by wrapping₂O₃The selectivity of butene, especially 1-butene, in the hydrogenation reaction of 1, 3-butadiene is improved from the original 25% to more than 90% when the 1, 3-butadiene is nearly completely converted, the selectivity of the 1-butene is improved from 12% to 56% (ACS Catalysis,2015.5 (5): p.2735-2739), the activity is slightly reduced, and the catalyst coated by alumina is required to realize the complete conversion of the 1, 3-butadiene at the temperature of nearly 100 ℃ (uncoated Pd/Al₂O₃Only about 65 deg.c). The Huangwei New teacher's topic group of the university of science and technology of China uses the atomic layer deposition technology to utilize gallium oxide to Pd/Al₂O₃The coating is carried out, the activity and the selectivity of the catalyst in the acetylene hydrogenation reaction are improved, the selectivity is finally optimized after 10 cycles of gallium oxide coating, and the selectivity is improved from about 5% to 60% when the conversion rate is 70% (ACS Catalysis,2016.6 (6): p.3700-3707). Although the selectivity of the oxide-coated palladium single-metal catalyst is greatly improved, the improvement effect is still limited, and the selectivity under high conversion rate needs to be further improved.

(d)Other catalysts: in selective hydrogenation reaction of alkyne and diolefin, besides the common Pd-based catalyst, noble metals are also available: ag. Au, Pt, non-noble metal: cu, Ni, etc., and the activity of the catalyst is generally poor. For example, in the supported Ni-M (alkali metal) -silicon aluminum molecular sieve (Z) catalytic system mentioned in Chinese patent application CN107088436A (acetylene is hydrogenated alone, and no ethylene exists in reaction gas), wherein the loading amount of Ni is 0.2-20%, the content of alkali metal is 0.8-8%, the conversion rate of acetylene is close to 100% at 200 ℃, and the selectivity of ethylene is 97.7% in the Ni-Na-Z catalyst mentioned in the patent. AgPd bimetallic catalysts with different proportions are synthesized by a method of using extracts in plants as reducing agents by the subject group of Sundawa teachers at the university of Xiamen, and the AgPd bimetallic catalysts have poor activity and no activity at 35 ℃ (ACS Sustainable Chemistry)&Engineering,2014.2 (5): p.1212-1218), and corresponding Ag₁Pd₃At this temperature, the catalyst achieves complete conversion of 1, 3-butadiene. The activity of this type of catalyst is very poorIt is difficult to reduce the alkyne and diolefin content to below 10ppm or to achieve the reduction by a higher temperature.

In addition, since the advent of atomic layer deposition technology (U.S. Pat. No. 4,058,430(1977)), there has been interest in attempting catalyst preparation using the technical advantages of atomic layer deposition for precise control (surf. Sci. Rep., (2016, 71, 410-) -472; Acc. chem. Res.,2013,46, 1806-) -1815; ACS Catal.2015,5,1804-₂O₃Deposition of Al on the surface of the catalyst₂O₃The wrapping layer realizes the sintering resistance and the carbon deposit resistance of the catalyst in the high-temperature ethane partial oxidative dehydrogenation reaction (Science,2012,335, 1205-1208; PCT/US 2012/039343); the aforementioned gallium oxide vs. Pd/Al₂O₃The Pd/Al is improved by wrapping₂O₃Activity and selectivity in acetylene hydrogenation reactions (ACS Catalysis,2016.6 (6): p.3700-3707); Pd/Al coated by iron oxide₂O₃Pd/Al₂O₃In the hydrogenation of 1, 3-butadiene, the activity of the catalyst and the selectivity of butene are improved to a certain extent, but the selectivity of butene and 1-butene at high conversion rate still needs to be improved.

In summary, the catalysts reported in the literature, whether they are monometallic, bimetallic or oxide-coated, still have limited improvement in olefin selectivity, and especially at high conversion, the lower olefin selectivity is still difficult to meet the industrial demand. In addition, the catalyst reported in the above documents still has a large amount of carbon deposit during the catalytic hydrogenation reaction, resulting in poor stability of the catalyst. Therefore, how to remarkably improve the selectivity of the olefin under high conversion rate of the catalyst and greatly improve the carbon deposition resistance of the catalyst on the basis of maintaining higher catalytic activity is a key for realizing hydrogenation with high selectivity and high stability.

How to combine the synergistic effect of the bimetal with the effective encapsulation of the oxide to promote the application of the bimetal catalyst in the selective hydrogenation reaction of acetylene or 1, 3-butadiene in the atmosphere rich in mono-olefin has not been reported.

Disclosure of Invention

In order to overcome one or more defects in the prior art, the invention aims to provide a wrapped bimetal supported catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in a mono-olefin-rich atmosphere by finding a suitable oxide wrapping and effectively combining with bimetal to generate a synergistic effect, so that high selectivity of ethylene or butylene can be maintained under high conversion rate of acetylene or 1, 3-butadiene in the mono-olefin-rich atmosphere, good catalyst activity is maintained, carbon deposition can be effectively inhibited, and catalyst stability is improved.

To this end, in one aspect, the present invention provides a process for the preparation of a wrapped bimetallic supported catalyst for the selective hydrogenation of acetylene or 1, 3-butadiene in a monoolefin rich atmosphere, characterized in that the catalyst comprises a support, an active metal component, a promoter metal component and a wrapping oxide, wherein the support is selected from the group consisting of SiO, a co-catalyst and a wrapping oxide₂、Al₂O₃、TiO₂、MgO、CeO₂、ZrO₂One or more of activated carbon, carbon black, graphene and carbon nanotubes, the active metal component being metal Pd and the promoter metal component being one or more selected from Au, Ag and Cu, the coating oxide being gallium oxide and being coated in a discontinuous manner on the surface of a bimetal supported catalyst precursor of the active metal component and the promoter metal component supported on a carrier,

the method comprises the following steps:

providing the bimetal supported catalyst precursor, wherein the content of the active metal component metal Pd calculated by Pd element is 0.1-5 wt%, and the content of the auxiliary metal component metal element calculated by metal element is 0.1-10 wt% based on the total weight of the bimetal supported catalyst precursor; and

depositing the wrapped-layer oxide onto the surface of the bimetallic supported catalyst precursor by a chemical vapor deposition method or an atomic layer deposition method to obtain the wrapped bimetallic supported catalyst, wherein the content of the wrapped-layer gallium oxide in terms of Ga element is 0.9-2.5 wt% based on the total weight of the obtained wrapped bimetallic supported catalyst.

In some preferred embodiments, the deposition of the cladding oxide comprises the steps of:

(a) placing the bimetal supported catalyst precursor in a reactor at 20-500 ℃, and introducing steam serving as a wrapping layer gallium precursor to be adsorbed on the surface of the bimetal supported catalyst precursor;

(b) introducing an oxidant to convert the clad gallium precursor adsorbed on the surface of the bimetallic supported catalyst precursor to the clad oxide;

(c) optionally repeating the above steps (a) and/or (b) one or more times, preferably 1-20 times.

In some preferred embodiments, the envelope gallium precursor is one or more selected from the group consisting of trimethyl gallium, triethyl gallium, gallium acetylacetonate, and pentamethylcyclopentadienyl gallium;

in some preferred embodiments, the oxidizing agent is selected from O₂、O₃、H₂O、H₂O₂NO and NO₂One or more of (a).

In some preferred embodiments, the method further comprises the steps of: purging the reactor with an inert gas between step (a) and step (b) and after step (b).

In some preferred embodiments, the bimetallic supported catalyst precursor is obtained by:

loading soluble salts of the active metal component and the auxiliary metal component on a carrier together by an impregnation method, and then drying and roasting to obtain the catalyst; or

Firstly, loading soluble salt of the assistant metal component on a carrier by an impregnation method to obtain an assistant metal loaded precursor, and depositing the active metal component on the assistant metal loaded precursor by an atomic layer deposition method after drying and roasting to obtain the assistant metal loaded precursor; or

And (6) purchasing and obtaining.

In another aspect, the present invention provides a wrapped bimetallic supported catalyst obtainable according to the above process, which catalyst is capable of effecting a selective hydrogenation reaction of acetylene or 1, 3-butadiene in a monoolefin rich atmosphere.

In another aspect, the present invention provides the use of the above-described wrapped bimetallic supported catalyst for the selective hydrogenation of acetylene or 1, 3-butadiene in a monoolefin-rich atmosphere.

In some preferred embodiments, the wrapped bimetallic supported catalyst is pretreated prior to use, wherein the pretreatment is oxidation with an oxygen-containing atmosphere at a temperature of 180 to 300 ℃ for 0.1 to 2 hours, followed by reduction with a hydrogen-containing atmosphere at a temperature of 100 to 200 ℃ for 0.1 to 2 hours.

In some preferred embodiments, in the selective hydrogenation reaction of acetylene in the monoolefin-rich atmosphere, the gas composition ratio by volume is acetylene to hydrogen to ethylene (0.1-1): (1-10): (10-50); in the selective hydrogenation reaction of the 1, 3-butadiene in the monoolefin-rich atmosphere, the gas composition ratio by volume of 1, 3-butadiene to hydrogen to propylene is (0.1-1): (1-10): (10-70).

According to the invention, gallium oxide is deposited on the surface of a bimetal supported catalyst precursor formed by a specific amount of bimetal PdAg, PdAu or PdCu by a chemical vapor deposition method or an atomic layer deposition method, and the obtained wrapped bimetal supported catalyst can show excellent catalytic performance in the selective hydrogenation reaction of acetylene or 1, 3-butadiene in a monoolefin-rich atmosphere, for example, the complete conversion of acetylene or 1, 3-butadiene in the monoolefin-rich atmosphere is realized at a mild temperature, and simultaneously, the high selectivity of ethylene or butene can be respectively maintained, so that the aim of combining the activity and the selectivity is achieved, carbon deposition can be effectively inhibited, and further, the high-selectivity catalyst can be kept stable for a long time.

Drawings

FIG. 1 shows5cGa prepared according to inventive example 1₂O₃-PdAg/SiO₂Catalyst and comparative example 1 (PdAg/SiO)₂Catalyst) acetylene conversion, ethylene selectivity, and temperature (deg.c) for selective hydrogenation of acetylene in an ethylene-rich atmosphere.

FIG. 2 shows 10cGa prepared according to example 1 of the present invention₂O₃-PdAg/SiO₂Transmission electron micrographs of the catalyst.

FIG. 3 shows 10cGa prepared according to example 1 of the present invention₂O₃-PdAg/SiO₂The results of a localized area two-dimensional elemental analysis of the catalyst, in which fig. 3(1) shows a photograph showing only silver element; fig. 3(2) shows a photograph showing the presence of two elements of silver and palladium, and fig. 3(3) shows a photograph showing the presence of three elements of silver, palladium and gallium after the gallium oxide coating layer is coated.

FIG. 4 shows 10cGa prepared according to example 2 of the present invention₂O₃-PdAg/SiO₂High angle annular dark field-scanning transmission electron microscope for spherical aberration correction of catalyst

FIG. 5 shows 10cGa prepared according to example 2 of the present invention₂O₃-PdAg/SiO₂Catalyst and PdAg/SiO prepared in comparative example 1₂Acetylene conversion, ethylene selectivity and temperature (. degree. C.) profiles for selective hydrogenation of acetylene in an ethylene-rich atmosphere.

FIG. 6 shows 10cGa prepared according to example 2 of the present invention₂O₃-PdAg/SiO₂Catalyst and comparative example 1 (PdAg/SiO)₂Catalyst) 1, 3-butadiene conversion, butene selectivity and temperature (. degree. C.) profile for the selective hydrogenation of 1, 3-butadiene in a propylene-rich atmosphere.

FIG. 7 shows 10cGa prepared according to example 2 of the present invention₂O₃-PdAg/SiO₂Catalyst and comparative example 1 (PdAg/SiO)₂Catalyst) stability profile at around 90% conversion of acetylene.

FIG. 8 shows 10cGa prepared according to example 2 of the present invention₂O₃-PdAg/SiO₂Catalyst and comparative example 1(PdAg @)SiO₂Catalyst) stability profile around 85% (example 2) and 90% (comparative example 1) conversion of 1, 3-butadiene.

Detailed Description

The inventors of the present invention have made intensive studies to achieve the above object and unexpectedly found that: on the one hand, not all oxide coatings can achieve the same effect. In the research, the inventors found that the coating such as alumina or cobalt oxide, although the selectivity can be improved to some extent, cannot effectively inhibit the generation of carbon, but only the coating obtained after atomic deposition in a discontinuous manner using a specific amount of gallium oxide can obtain the desired catalytic performance and carbon deposition resistance. In other words, while gallium oxide encapsulation and bimetallic supported catalysts are mentioned in the prior art, it is not obvious to combine the two, especially to deposit specific amounts in a specific deposition pattern to form the encapsulation layer. On the other hand, by using a chemical vapor deposition method or an atomic layer deposition method, a specific amount of gallium oxide is deposited on the surface of a bimetal supported catalyst precursor formed by specific amounts of bimetal PdAg, PdAu or PdCu as a wrapping layer, so that the wrapping layer oxide with high dispersibility can be accurately deposited; and by utilizing the precise control advantage of the chemical vapor deposition, particularly the atomic layer deposition technology, the deposition form of the coating oxide can be precisely regulated and controlled at the atomic level (namely, deposition is carried out in a discontinuous mode), so that the selectivity of the catalyst is improved to the maximum extent, the activity of the catalyst is maintained, and the high-selectivity hydrogenation catalyst which has both activity and selectivity and can realize selective hydrogenation of acetylene or 1, 3-butadiene in the atmosphere rich in mono-olefin is obtained.

More specifically, the invention provides a wrapped bimetal supported catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in monoolefin-rich atmosphere, which comprises a carrier, an active metal component, an auxiliary metal component and a wrapping layer oxide, wherein the carrier is selected from SiO₂、Al₂O₃、TiO₂、MgO、CeO₂、ZrO₂Active carbon, carbon black and grapheneAnd one or more of carbon nanotubes, the active metal component being metal Pd and the promoter metal component being one or more selected from Au, Ag and Cu, the coating oxide being gallium oxide and being coated in a discontinuous manner on the surface of the bimetal supported catalyst precursor of the active metal component and the promoter metal component supported on the carrier.

As referred to herein, the term "monoolefin" refers to an olefin having one double bond, examples of which include, but are not limited to, ethylene, propylene, butylene, and the like.

As referred to herein, "selective hydrogenation of acetylene or 1, 3-butadiene in a monoolefin-rich atmosphere" means: on the one hand, the content of acetylene or 1, 3-butadiene is low with respect to the content (generally by volume) of monoolefins, such as ethylene and/or propylene, in the atmosphere, while other equilibrium gases, such as inert gases, for example nitrogen or argon, etc., and possibly other impurity gases, may be present in such an atmosphere; on the other hand, the selective hydrogenation of acetylene or 1, 3-butadiene means that the hydrogenation of acetylene or 1, 3-butadiene is preferentially carried out with respect to the monoolefin present in the atmosphere (i.e., the catalyst of the present invention is highly selective), while the hydrogenation is a semi-hydrogenation, i.e., the main product from the selective hydrogenation of acetylene is ethylene, and the main product from the selective hydrogenation of 1, 3-butadiene is butene.

In the present invention, only for the purpose of clearer distinction, a precursor including the active metal component, the promoter metal component and the carrier to be subjected to gallium oxide wrapping is referred to as a bimetal supported catalyst precursor, and a catalyst obtained after the gallium oxide wrapping is referred to as a wrapped bimetal supported catalyst or a gallium oxide wrapped bimetal supported catalyst.

As mentioned above, the present invention can achieve precise deposition of a cladding oxide with high dispersibility by precisely controlling the deposition morphology of the cladding oxide at an atomic level using the precise control advantages of chemical vapor deposition, particularly Atomic Layer Deposition (ALD) technology, thereby depositing a gallium oxide cladding in a discontinuous manner on the surface of a bimetallic supported catalyst precursor formed of a specific amount of bimetallic PdAg, PdAu or PdCu. Here, the expression "deposited in a discontinuous manner" means that, in the wrapped bimetallic supported catalyst obtained according to the present invention, the gallium oxide wrapping layer does not completely cover the surface of the bimetallic supported catalyst precursor, but is instead deposited on the surface in a dotted or scattered manner or the wrapping layer is formed to have a plurality of pores (i.e., porous) therein so as to allow the active metal and/or promoter metal in the bimetallic supported catalyst precursor to be exposed to the reaction atmosphere during the reaction. Preferably, such a discontinuous coating is a porous coating, whereby the selectivity of the catalyst of the present invention can be more effectively improved while inhibiting carbon deposition and thus having higher stability. The inventors have found that if the washcoat gallium oxide is deposited on the bimetallic supported precursor in a continuous manner, i.e. forming a closed washcoat on its surface, the resulting final catalyst is less active and fails to achieve the desired high selectivity activity.

In the invention, based on the total weight of the bimetal supported catalyst precursor, the content of the active metal component metal Pd calculated by Pd element is 0.1-5 wt%, and the content of the auxiliary metal component calculated by metal element is 0.1-10 wt%; and the content of the wrapped gallium oxide in terms of Ga element is 0.9-2.5 wt% based on the total weight of the obtained wrapped bimetallic supported catalyst. The inventors have found that in the presence of a catalyst precursor in which the active metal Pd and the promoter metal component are present in combination in the above-specified amounts, the subsequent encapsulation of a specific amount of gallium oxide (content in Ga element of 0.9-2.5 wt% based on the total weight of the final catalyst) by chemical vapor deposition, in particular atomic layer deposition, in a discontinuous deposition, enables to obtain the desired high selectivity while suppressing carbon deposition and thus having a higher stability. In contrast, when the active metal Pd, the promoter metal component content and, in particular, the coating gallium oxide are not within the above-specified ranges, or the coating gallium oxide is not deposited in a discontinuous manner, it is difficult to coat the gallium oxide by the above-described method to obtain the desired overall catalytic performance.

The wrapped bimetallic supported catalyst of the present invention may be prepared by a process comprising: providing the bimetallic supported catalyst precursor; and depositing the wrapping layer oxide onto the surface of the bimetallic supported catalyst precursor by chemical vapor deposition or atomic layer deposition.

In the present invention, the bimetallic supported catalyst precursor formed of PdAg, PdAu or PdCu used is not particularly limited, and may be a bimetallic supported catalyst formed of various PdAg, PdAu or PdCu prepared by one or a combination of several methods such as an immersion method, an ion exchange method, a precipitation method, a sol-gel method, and the like. For example, the bimetallic supported catalyst precursor may be obtained by: the active metal component and the soluble salt of the auxiliary metal component are loaded on a carrier together by an impregnation method and then dried and roasted to obtain the active metal component, or the soluble salt of the auxiliary metal component is loaded on the carrier by the impregnation method to obtain an auxiliary metal loaded precursor, and the active metal component is deposited on the auxiliary metal loaded precursor by an atomic layer deposition method after the drying and roasting.

In the present invention, there is no particular requirement for the support used, as long as it can support the above-mentioned noble metal component or/and metal promoter metal component. Frequently or preferably, the support used is selected from SiO₂、Al₂O₃、TiO₂、MgO、CeO₂、ZrO₂One or more of activated carbon, carbon black, graphene and carbon nanotubes, wherein SiO is more preferred₂、Al₂O₃、TiO₂、CeO₂、ZrO₂Or activated carbon, more preferably SiO₂。

In the invention, the gallium oxide wrapping layer is deposited on the surface of the bimetallic supported catalyst precursor formed by PdAg, PdAu or PdCu by a chemical vapor deposition method or an atomic layer deposition method. Without being bound by any theory, it is believed that the bimetallic supported catalyst formed of Pd Ag, PdAu or PdCu generally has a higher catalytic activity due to the presence of Pd metal particles, and when the gallium precursor of the coating oxide is introduced onto the surface of the bimetallic supported catalyst precursor containing a specific amount of active metal Pd and promoter metal by a chemical vapor deposition method or an atomic layer deposition method, the gallium precursor of the coating oxide adsorbs onto the surface of the PdAg, PdAu or PdCu metal particles by dissociative adsorption; thereafter, the gallium precursor ligand of the coating oxide can be effectively removed by using the oxidant, and the surface position of the loaded metal particles can be accurately and selectively modified, so that the required high catalytic selectivity is provided, and carbon deposition is inhibited and the stability is higher.

In the present invention, preferably, the deposition of the capping layer oxide may include the steps of:

(a) placing the bimetal supported catalyst precursor in a reactor at 20-500 ℃, and introducing steam serving as a wrapping layer gallium precursor to be adsorbed on the surface of the bimetal supported catalyst precursor; and

(b) introducing an oxidant to cause the coating gallium precursor adsorbed on the surface of the bimetallic supported catalyst precursor to undergo a chemical reaction, thereby realizing the deposition of gallium coating oxide on the surface of the bimetallic catalyst, and thus obtaining the required high-selectivity hydrogenation catalyst;

in the present invention, the above steps (a) and/or (b) may be repeatedly performed one or more times, for example, 1 to 20 times, according to the need, for example, to adjust the thickness, deposition morphology, etc. of the gallium oxide cladding layer. Preferably, the number of depositions or cycles is no greater than 15, most preferably no greater than 10.

More preferably, the deposition or addition of the cladding oxide is achieved by atomic layer deposition, wherein the deposition comprises the steps of:

(1) putting a bimetal load type catalyst precursor into a reactor or a reaction cavity, heating to a certain temperature (for example, 20-500 ℃), and introducing gallium precursor steam of a wrapping layer precursor with a proper dosage to adsorb on the surface of the bimetal load type catalyst precursor;

(2) optionally purging the reactor or reaction chamber with an inert gas to purge the gallium precursor and other reaction products of the cladding precursor remaining therein;

(3) introducing an appropriate amount of oxidant to enable the oxidant to chemically react with the gallium precursor of the wrapping layer precursor adsorbed on the surface of the bimetallic catalyst precursor, thereby realizing the controllable deposition of the gallium wrapping layer oxide on the surface of the bimetallic catalyst.

(4) Optionally purging the reactor or reaction chamber with an inert gas to purge the remaining oxidant or other reaction products therein, thereby obtaining the highly selective hydrogenation catalyst.

(5) Optionally, the above steps (1) - (4) are repeated one or more times (i.e. one or more deposition cycles) in succession to provide more precise control of the content or amount of gallium encrusting oxide deposited, thickness, deposition morphology, etc.

In the present invention, preferably, the gallium oxide precursor for deposition by chemical vapor deposition or atomic layer deposition may be as follows: it is preferably one or more selected from trimethyl gallium, triethyl gallium, gallium acetylacetonate and pentamethylcyclopentadienyl gallium. Among these, particularly preferred gallium precursor is trimethylgallium.

In the present invention, preferably, the oxidizing agent used in the deposition of the cladding oxide may be selected from O₂、O₃、H₂O、H₂O₂NO and NO₂One or more of (a). More preferably, the oxidizing agent used is selected from O₂、O₃、H₂O or H₂O₂。

In the present invention, N is an inert gas which can be used₂Ar, He or a combination thereof, preferably N₂。

In the invention, in the process of depositing the coating oxide, the heating temperature of the reactor or the reaction cavity or the temperature of the bimetal supported catalyst precursor is preferably 20-500 ℃, more preferably 50-350 ℃, and most preferably 100-200 ℃.

The wrapped bimetal supported catalyst can be used for acetylene or 1, 3-butadiene selective hydrogenation reaction in an atmosphere rich in monoolefine such as ethylene.

In the invention, preferably, the wrapped bimetal supported catalyst is pretreated before use, wherein the pretreatment is oxidation for 0.1-2 hours at the temperature of 180-300 ℃ by using an oxygen-containing atmosphere, and then reduction for 0.1-2 hours at the temperature of 100-200 ℃ by using a hydrogen-containing atmosphere.

In the present invention, there is no particular limitation on the composition of the monoolefin-rich atmosphere to which the highly selective hydrogenation catalyst is applied. Typically, in selective hydrogenation applications, the volume content of acetylene or 1, 3-butadiene in the olefin-rich atmosphere is less than 2%. Preferably, in the selective hydrogenation reaction of acetylene in the monoolefin-rich atmosphere, the gas composition ratio by volume of acetylene to hydrogen to ethylene is (0.1-1): (1-10): (10-50); in the selective hydrogenation reaction of the 1, 3-butadiene in the monoolefin-rich atmosphere, the gas composition ratio by volume of 1, 3-butadiene to hydrogen to propylene is (0.1-1): (1-10): (10-70).

The method for depositing the coating oxide has good repeatability and wide applicability, is suitable for the bimetallic supported catalyst formed by any PdAg, PdAu or PdCu, and comprises the bimetallic supported catalyst formed by various PdAg, PdAu or PdCu prepared by one or more methods such as a dipping method, an ion exchange method, a precipitation method, a sol-gel method and the like.

The method for depositing the coating oxide is simple to operate, and the performance of the bimetallic supported catalyst formed by PdAg, PdAu or PdCu can be greatly improved only by one-step operation of a chemical vapor deposition method or an atomic layer deposition method.

According to the invention, by using a chemical vapor deposition method, particularly an atomic layer deposition method, after a coating oxide is deposited on the surface of a bimetallic supported catalyst formed by Pd Ag, PdAu or PdCu, the obtained high-selectivity hydrogenation catalyst can show excellent catalytic performance in the selective hydrogenation reaction of acetylene or 1, 3-butadiene in a monoolefin-rich atmosphere, for example, when the conversion rate of acetylene or 1, 3-butadiene is close to 100%, the selectivity of ethylene can still be kept above 90%, the selectivity of butene is kept above 97%, the activity of the catalyst is kept better, carbon deposition can be effectively inhibited, and the catalyst can be kept stable for a long time.

For a better understanding of the technical features, objects, and advantages of the present invention, reference will now be made to the following drawings and examples, in which the present invention is illustrated in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1: 5cGa₂O₃@AgPd/SiO₂Preparation of catalyst and activity test of acetylene selective hydrogenation in ethylene-rich atmosphere

Ag/SiO₂Preparation of the catalyst: using a conventional isovolumetric impregnation method, SiO is first impregnated₂Drying in an oven, and adding silver nitrate (AgNO)₃Sigma-Aldrich, 99% purity), stirring, oven drying overnight, grinding the sample thoroughly, and finally using 10% O at 500 deg.C₂Ar treatment is carried out for 3 h.

PdAg/SiO₂Preparation of a catalyst precursor: in a self-made viscous flow stainless steel tube reactor (GEMSTAR-6TM bench ALD, Arradiance) with ultra-high purity N as carrier gas₂(UHP, 99.999%) at a flow rate of 200 mL/min. The base pressure was 0.5Torr, 500mg of Ag/SiO₂The catalyst was loaded into the ALD reactor and Pd deposition was performed at 200 ℃. With palladium hexafluoroacetylacetonate (Pd (hfac)₂Sigma-Aldrich, 99.9%) and formaldehyde solution (Sigma-Aldrich, 37% HCHO and 15% CH)₃OH dissolved in water) as a precursor. Pd (hfac)₂The precursor vessel was heated to 65 ℃ to achieve sufficient vapor pressure. First pulse 150s Pd (hfac)₂Steam followed by N₂Blowing off unreacted Pd precursor, introducing formaldehyde solution to remove Pd ligand, and finally introducing N₂The unreacted formaldehyde solution was purged. To obtain Ag @ Pd/SiO₂Bimetallic supported catalyst precursor in Ag/SiO₂With 10 cycles of Pd deposited thereon. The inductively coupled plasma emission spectrometer (China university of science and technology) test of the obtained catalyst precursor sample shows that the total weight of the precursor is based onIn addition, the content of the auxiliary metal Ag calculated by Ag element is 4.54 wt%, and the content of the active metal Pd calculated by Pd element is 0.97 wt%.

Ga₂O₃Deposition of a wrapping layer: also in ultra-high purity N₂The reaction was carried out in a viscous flow type stainless steel tube reactor as a carrier gas, and the flow rate of the carrier gas was 200 mL/min. Using Ga (CH)₃)₃(Sigma-Aldrich, 99.99%) as Ga precursor, O₂(UHP, 99.999%) as an oxidizing agent, and sequentially exposing Ga (CH) for 5ms on the catalyst at 150 DEG C₃)₃120s of N₂1000s O₂And 120s of N₂The above steps were repeated 5 times. Finally, the sample was removed from the reaction chamber to obtain coated 5cGa₂O₃@AgPd/SiO₂Catalyst (here, "5 c" in the catalyst expression indicates that gallium oxide was deposited 5 times). Inductively coupled plasma emission spectroscopy (university of china science and technology) testing of the resulting wrapped catalyst sample showed that the content of the wrapped gallium oxide, calculated as elemental Ga, was 1.8 wt% based on the total weight of the wrapped catalyst sample.

Activity test 1: and carrying out activity test of acetylene selective hydrogenation in an ethylene-rich atmosphere. 20mg of 5cGa obtained in example 1 were added₂O₃@AgPd/SiO₂The coated catalyst was first ground and mixed homogeneously with 1g of quartz sand (to prevent the formation of "hot spots" in the reaction) and charged to a fixed bed reactor.

Pretreatment of a catalyst: first 10% O₂Treatment in an Ar atmosphere at 200 ℃ for 0.5H, followed by cooling to 150 ℃ and switching to 10% H₂And Ar, continuing to treat for 0.5 hour, and finally cooling to room temperature and introducing reaction gas for testing.

The reaction gas sample for activity test had a composition of 1% acetylene + 2% hydrogen + 50% ethylene + 47% argon by volume and a reaction gas flow rate of 20 mL/min.

In the temperature range of 20-120 ℃, the acetylene conversion rate and the ethylene selectivity of the catalyst are examined by increasing the reaction temperature, each temperature point is kept for 10min, and the test result is shown in figure 1. As can be seen from fig. 1, with the catalyst obtained in this example, complete conversion of acetylene is achieved at less than 100 ℃; the selectivity of ethylene is still maintained to be more than 90 percent until the acetylene conversion rate reaches 97 percent; and when acetylene is completely converted, the selectivity of ethylene is kept above 82%.

Example 2: 10cGa₂O₃@AgPd/SiO₂Preparation of catalyst and activity test of preferential hydrogenation acetylene in ethylene-rich atmosphere and selective hydrogenation of 1, 3-butadiene in propylene-rich atmosphere

10cGa₂O₃@PdAg/SiO₂Preparation of the catalyst: the catalyst preparation was the same as in example 1, except that Ga₂O₃The number of depositions of the wrapping layer was 10, thereby obtaining 10cGa₂O₃@AgPd/SiO₂A catalyst. Inductively coupled plasma emission spectrometer testing of the resulting wrapped catalyst sample showed that the content of the wrapped layer gallium oxide, calculated as elemental Ga, was 2.1 wt% based on the total weight of the wrapped catalyst sample.

The resulting 10cGa₂O₃-PdAg/SiO₂The transmission electron microscope results of the catalyst are shown in fig. 2, from which fig. 2 it can be seen that the metal particles are uniformly distributed on the carrier, fig. 3(1) to (3) are elemental analysis photographs of the particles of the resulting catalyst, in which fig. 3(1) shows a photograph showing only silver element; fig. 3(2) shows a photograph showing the presence of two elements of silver and palladium, and fig. 3(3) shows a photograph showing the presence of three elements of silver, palladium and gallium after the gallium oxide coating layer is coated. The presence of Ga, Pd and Ag in the particles is clearly seen in fig. 3, and where Ga is "dotted" or dispersed in a discontinuous fashion on the surface of the PdAg.

The resulting 10cGa₂O₃-PdAg/SiO₂High angle annular dark field-scanning transmission electron microscopy photographs of the spherical aberration corrected high angle annular dark field-scanning transmission electron microscopy of the catalyst are shown in fig. 4, and in fig. 4, it can be seen that although Ag and Pd have almost no difference in brightness, the interval between layers changes, indicating that a Pd shell exists outside the Ag core, demonstrating the existence of a Pd shell layer, a wrapping layer can also be observed outside the particle, and the arrows in the figures indicate that Ga in the amorphous state of the outermost layer is indicated by arrows₂O₃。

Activity test 2: the activity test for selective hydrogenation of acetylene in an ethylene-rich atmosphere was carried out in the same activity test procedure as in example 1, and the test results are shown in fig. 5. As can be seen from fig. 5, with the catalyst obtained in this example, a selectivity of 90% or more was maintained until the complete conversion of acetylene, while the complete conversion of acetylene (122 ℃) could be achieved at a milder temperature.

Activity test 3: and carrying out activity test of selective hydrogenation of 1, 3-butadiene in a propylene-rich atmosphere. 10mg of 10cGa obtained in example 2 were initially introduced₂O₃@AgPd/SiO₂The catalyst was ground and mixed homogeneously with 1g of quartz sand (to prevent the formation of "hot spots" in the reaction) and charged to a fixed bed reactor.

The reaction gas sample for the activity test had a composition of 1.9% 1, 3-butadiene + 3.8% hydrogen + 70% propylene + 24.3% argon by volume and a reaction gas flow rate of 25 mL/min.

In the temperature range of 20-80 ℃, the acetylene conversion rate and the ethylene selectivity of the catalyst are inspected by increasing the reaction temperature, each temperature point is kept for 10min, and the activity test result is shown in fig. 6. From fig. 6, it can be seen that the catalyst obtained in this example can achieve complete conversion of 1, 3-butadiene at about 70 ℃, and the selectivity of butene is always above 97%.

Stability test 1: mixing the above 10cGa₂O₃@AgPd/SiO₂The catalyst was tested for stability in the selective hydrogenation of acetylene in an ethylene rich atmosphere, where the catalyst dosage, reactor, pretreatment mode, reaction gas composition and flow rate were as described in activity test 1. Stability test the samples were tested continuously for 40 hours at about 90% acetylene conversion, the conversion and the selectivity of ethylene and butene were observed and the test results are shown in fig. 7. As can be seen from FIG. 7, the catalyst according to example 2 of the present invention is rich in ethyleneThe activity of acetylene in the atmosphere can be kept for a long time in the preferential hydrogenation reaction without obvious inactivation, and the selectivity of ethylene is not obviously reduced.

Stability test 2: mixing the above 10cGa₂O₃@AgPd/SiO₂The catalyst was tested for stability in a propylene-rich atmosphere in a selective hydrogenation of 1, 3-butadiene, where the catalyst dosage, reactor, pretreatment mode, reaction gas composition and flow rate were as described in activity test 3. Stability test the samples were tested continuously for 40 hours at about 85% 1, 3-butadiene conversion, the conversion and the selectivity of ethylene, butene, 1-butene were observed, and the test results are shown in fig. 8. As can be seen from FIG. 8, the catalyst of example 2 can maintain the activity for a long time without significant deactivation and without significant decrease in the selectivity of butene in the preferential hydrogenation reaction of 1, 3-butadiene in a propylene-rich atmosphere.

Comparative example 1: AgPd/SiO₂Preparation of catalyst and activity test of catalyst in selective hydrogenation of acetylene in ethylene-rich atmosphere and selective hydrogenation of 1, 3-butadiene in propylene-rich atmosphere

Catalyst: deposited Ga obtained in example 1 was used₂O₃PdAg/SiO obtained before coating₂The catalyst precursor was used as the catalyst of comparative example 1.

And (3) activity test: PdAg/SiO of comparative example 1₂The catalyst was subjected to two hydrogenation activity tests. The catalyst dosage, reactor, pretreatment mode, reaction gas composition and flow rate were the same as in activity tests 1 and 3, respectively. The results of the activity test are shown in FIGS. 1, 5 and 6, respectively. As can be seen from FIGS. 1 and 5, Ga is not passed through₂O₃Wrapped Ag @ Pd/SiO₂The catalyst realizes the complete conversion of acetylene at 108 ℃, the selectivity of ethylene is rapidly reduced after the conversion rate of acetylene exceeds 60 percent, and when the acetylene is close to the complete conversion, the selectivity of ethylene is only less than 20 percent, and simultaneously, the catalyst is used in a stability test; FIG. 6 shows uncoated Ag @ Pd/SiO₂The catalyst can realize the complete conversion of 1, 3-butadiene at about 70 ℃, the selectivity of the butene is always maintained to be more than 90 percent, but the selectivity of the 1-butene is continuously reduced and is not finally reached15％。

And (3) stability testing: stability tests were performed as described above for stability tests 1 and 2, respectively, and the results are shown in fig. 7 and 8. As can be seen from fig. 7, the deactivation was significant when the catalyst of comparative example 1 was used, tested for 40 hours at about 90% acetylene conversion; it can be seen from fig. 8 that the catalyst of comparative example 1 also exhibited a more significant deactivation in the selective hydrogenation of 1, 3-butadiene in a propylene-rich atmosphere.

Comparative example 2: catalyst obtained by forming gallium oxide coating layer by using impregnation method instead of atomic deposition method and performance test thereof

Preparing a catalyst: the catalyst preparation was the same as in example 2, except that the catalyst was impregnated on AgPd/SiO by a conventional impregnation method₂Ga in an amount of 2.1 wt% in terms of elemental Ga is formed on the catalyst precursor₂O₃And (7) a wrapping layer. The observation of the transmission electron microscope shows that the gallium oxide coating layer deposited by the dipping method is on AgPd/SiO₂The catalyst precursor has a continuous coating formed on its surface, i.e., the AgPd is integrally coated instead of being dotted or dispersed therein.

Performance testing and results: the resulting encapsulated catalysts were subjected to activity tests and stability tests in the same procedures as described in example 2 for activity tests 2-3 and stability tests 1-2. As a result, it was found that: (1) in the acetylene selective hydrogenation test in the ethylene-rich atmosphere, the selectivity of the ethylene product is lower than 50% at 100% acetylene conversion by using the catalyst obtained in the comparative example; (2) in the activity test of selective hydrogenation of 1, 3-butadiene in an ethylene-rich atmosphere, the selectivity of butene was below 60% overall at 100% 1, 3-butadiene conversion using the catalyst obtained in this comparative example; (3) the catalyst of the comparative example has obvious inactivation phenomenon in the selective hydrogenation reaction of acetylene in the ethylene-rich atmosphere and in the selective hydrogenation reaction of 1, 3-butadiene in the ethylene-rich atmosphere, and has poor stability.

Although specific embodiments of the invention have been described in detail, those skilled in the art will appreciate. Various modifications and substitutions of those details may be made in light of the overall teachings of the disclosure, and such changes are intended to be within the scope of the present invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for preparing a wrapped bimetallic supported catalyst for selective hydrogenation of acetylene or 1, 3-butadiene in a monoolefin rich atmosphere, characterized in that the catalyst comprises a support, an active metal component, an auxiliary metal component and a wrapping layer oxide, wherein the support is selected from SiO₂、Al₂O₃、TiO₂、MgO、CeO₂、ZrO₂One or more of activated carbon, carbon black, graphene and carbon nanotubes, the active metal component being metal Pd and the promoter metal component being one or more selected from Au, Ag and Cu, the coating oxide being gallium oxide and being coated in a discontinuous manner on the surface of a bimetal supported catalyst precursor of the active metal component and the promoter metal component supported on a carrier,

the method comprises the following steps:

2. The method of claim 1, wherein the depositing of the cladding oxide comprises the steps of:

3. The method of claim 2, wherein the envelope gallium precursor is one or more selected from the group consisting of trimethyl gallium, triethyl gallium, gallium acetylacetonate, and pentamethylcyclopentadienyl gallium.

4. The method of claim 2, wherein the oxidizing agent is selected from O₂、O₃、H₂O、H₂O₂NO and NO₂One or more of (a).

5. The method according to claim 2, characterized in that the method further comprises the steps of: purging the reactor with an inert gas between step (a) and step (b) and after step (b).

6. The method of claim 1, wherein the bimetallic supported catalyst precursor is obtained by:

And (6) purchasing and obtaining.

7. A wrapped bimetallic supported catalyst obtainable by the process according to any one of claims 1-6, which catalyst is capable of effecting a selective hydrogenation reaction of acetylene or 1, 3-butadiene in a monoolefin rich atmosphere.

8. Use of the wrapped bimetallic supported catalyst according to claim 7 for the selective hydrogenation of acetylene or 1, 3-butadiene in a monoolefin rich atmosphere.

9. The use according to claim 8, wherein the wrapped bimetallic supported catalyst is pretreated before use, wherein the pretreatment is oxidation with an oxygen-containing atmosphere at a temperature of 180-300 ℃ for 0.1-2 hours followed by reduction with a hydrogen-containing atmosphere at a temperature of 100-200 ℃ for 0.1-2 hours.

10. The use of claim 8, wherein in the selective hydrogenation of acetylene in the monoolefin-rich atmosphere, the gas composition ratio by volume is acetylene to hydrogen to ethylene (0.1-10) to (1-10) to (10-99); in the selective hydrogenation reaction of the 1, 3-butadiene in the monoolefin-rich atmosphere, the gas composition ratio by volume of the 1, 3-butadiene to the hydrogen to the propylene is (0.1-10) to (1-10) to (10-99).