CN112844407A

CN112844407A - Preparation method of carbon three-fraction selective hydrogenation catalyst

Info

Publication number: CN112844407A
Application number: CN201911186863.1A
Authority: CN
Inventors: 温翯; 韩伟; 车春霞; 苟尕莲; 梁玉龙; 李平智; 柏介军; 谭都平
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2021-05-28
Anticipated expiration: 2039-11-26

Abstract

The invention relates to a preparation method of an alkyne selective hydrogenation catalyst, in particular to a preparation method of a carbon three-fraction selective hydrogenation catalyst. The catalyst prepared by the method adopts alumina or mainly alumina as a carrier, and has a bimodal pore distribution structure, the catalyst at least contains Pd, Rh, Ni and Cu, wherein an active component Pd is loaded in two modes of solution and microemulsion; rh is loaded by a solution method, and is mainly distributed in pores of 15-35 nm of a carrier with Pd loaded by the solution method; ni and Cu are loaded by adopting a microemulsion dipping method, and Pd loaded by an emulsion method is mainly distributed in macropores of 70-300 nm of a carrier and loaded after Ni and Cu are loaded. The catalyst prepared by the method has lower reduction temperature, low green oil generation amount and excellent catalytic performance and coking resistance.

Description

Preparation method of carbon three-fraction selective hydrogenation catalyst

Technical Field

The invention relates to a preparation method of an alkyne selective hydrogenation catalyst, in particular to a preparation method of a high coking resistance catalyst for carbon three-fraction selective hydrogenation.

Background

Propylene is one of the most important basic raw materials in the petrochemical industry, is an important monomer for synthesizing various polymers, and is mostly prepared by steam cracking of petroleum hydrocarbons (such as ethane, propane, butane, naphtha, light diesel oil and the like). Propylene-based C obtained by this method₃The fraction contains 1.5 to 8.0% of Propyne (PD) + propadiene (MA). The presence of MAPD, which affects the quality of the polymerization product, is currently removed by selective hydrogenation in the petrochemical industry.

The traditional carbon-three hydrogenation catalyst adopts Al as the catalyst₂O₃The catalyst is used as a carrier, Pd is used as an active component, Ag is added as an auxiliary active component, and the specific surface area of the catalyst is 15-100 m²(ii) in terms of/g. The preparation method of the catalyst adopts an impregnation method. The influence of the surface tension of the impregnation liquid and the solvation effect is particularly obvious in the process of impregnating and drying the catalyst, and the precursor of the metal active component is deposited on the surface of the carrier in the form of aggregates. In addition, the distribution state between Pd and Ag is not ideal, and the catalyst activity is poorThe catalyst is not easy to control, the selectivity of the catalyst is mainly controlled by the aperture of the catalyst and the dispersion state of the active component, and the dispersion of the active component is influenced by the number of groups on the surface of the carrier and the solvation in the preparation process of the catalyst, so that the randomness of the dispersion of the active component of the catalyst is high, the preparation repeatability is poor, and the effect of the catalytic reaction is not ideal.

CN98810096 discloses a catalytic distillation method for removing MAPD in carbon three-fraction, which combines catalytic hydrogenation and rectification separation processes into one, and because the heat exchange is sufficient in the process, temperature runaway is not easy to occur, and a small amount of oligomer generated in the process is easy to carry out, and the coking degree on the surface of the catalyst can be greatly reduced. The method has high filling requirement on the catalytic distillation tower, and the distribution state of the fluid has great influence on the separation effect. The method also increases the difficulty of operation.

Patent No. cn201110086151.x discloses a selective hydrogenation method for carbon three-fraction, which adopts a catalyst comprising Pd as a main active component, alumina as a carrier, and a promoter silver. The carrier is adsorbed with a specific high molecular compound, a high molecular coating layer is formed on the surface of the carrier in a certain thickness, the compound with a functional group reacts with the high molecular compound to enable the compound to have the functional group capable of being complexed with the active component, and the active component is ensured to be orderly and highly dispersed by the complexation reaction of the active component on the surface of the carrier. By adopting the method, the carrier adsorbs specific high molecular compounds, and the high molecular compounds are chemically adsorbed with the high molecular compounds through the hydroxyl groups of the alumina, and the amount of the high molecular compounds adsorbed by the carrier is limited by the number of the hydroxyl groups of the alumina; the functional polymer and Pd have weak complexing effect, sometimes the loading capacity of the active components can not meet the requirement, and part of the active components are remained in the impregnation liquid, so that the cost of the catalyst is increased; the method for preparing the carbon three hydrogenation catalyst also has the defect of complex process flow.

CN2005800220708.2 discloses a selective hydrogenation catalyst for acetylene and diolefin in light olefin raw material, which is composed of a first component selected from copper, gold and silver and a second component selected from nickel, platinum, palladium, iron, cobalt, ruthenium and rhodium, and in addition, the catalyst also includes at least one inorganic salt and oxide selected from zirconium, lanthanide and alkaline earth metal mixture. The catalyst forms a fluorite structure after being calcined, used or regenerated. The total content of the catalyst oxide is 0.01-50%, and the preferred roasting temperature is 700-850 ℃. The addition of a third oxide, modified alumina or silica support, helps to increase catalyst selectivity and activity, selectivity after regeneration. The technology still takes copper, gold, silver, palladium and the like as active components and takes nickel, platinum, palladium, iron, cobalt, ruthenium, rhodium and the like as auxiliary components, and the regeneration performance of the catalyst is improved by modifying the oxide of the carrier.

CN102218323A discloses a hydrogenation catalyst for unsaturated hydrocarbons, the active component is a mixture of 5-15% of nickel oxide and 1-10% of other metal oxides, the other metal oxides can be one or more of molybdenum oxide, cobalt oxide and iron oxide, and in addition, 1-10% of an auxiliary agent is also included. The technology is mainly used for hydrogenating and converting ethylene, propylene, butylene and the like in the tail gas of the coal-to-liquid industry into saturated hydrocarbon, and has good deep hydrogenation capacity. The technology is mainly used for the total hydrogenation of ethylene, propylene, butylene and the like in various industrial tail gases rich in CO and hydrogen, and is not suitable for the selective hydrogenation of alkyne and dialkene.

CN200810114744.0 discloses an unsaturated hydrocarbon selective hydrogenation catalyst and a preparation method thereof. The catalyst uses alumina as a carrier, uses palladium as an active component, and improves the impurity resistance and the coking resistance of the catalyst by adding rare earth, alkaline earth metal and fluorine, but the selectivity of the catalyst is not ideal.

ZL201310114077.7 discloses a hydrogenation catalyst, the active components in the catalyst are Pd, Ag and Ni, wherein the Pd and the Ag are loaded by adopting an aqueous solution impregnation method, and the Ni is loaded by adopting a W/O microemulsion impregnation method. After the method is adopted, Pd/Ag and Ni are positioned in pore channels with different pore diameters, green oil generated by reaction is saturated and hydrogenated in a large pore, and the coking amount of the catalyst is reduced.

However, the reduction temperature of Ni is usually about 500 ℃, and the reduced Pd atoms are easy to gather at the temperature, so that the activity of the catalyst is greatly reduced, the equivalent amount of active components needs to be greatly increased to compensate the activity loss, and the selectivity is reduced.

Disclosure of Invention

The invention aims to provide a preparation method of an alkyne selective hydrogenation catalyst, in particular to a preparation method of a hydrogenation catalyst before carbon three-fraction selective hydrogenation.

The invention provides a preparation method of an alkyne selective hydrogenation catalyst, wherein a carrier of the catalyst is alumina or mainly alumina and has a bimodal pore distribution structure, and active components of the catalyst at least contain Pd, Rh, Ni and Cu, and the preparation method is characterized in that the active components Pd are loaded in two modes of solution and microemulsion; rh is loaded by a solution method, and Pd loaded by the solution method is mainly distributed in pores of the carrier; ni and Cu are loaded by a microemulsion impregnation method, and Pd loaded by microemulsion is mainly distributed in macropores of the carrier.

In the catalyst prepared by the preparation method, selective hydrogenation reaction of alkyne occurs in a main active center consisting of Pd and Rh, Ni and Cu are soaked in macropores of a carrier in a form of microemulsion, and green oil generated in the reaction generates saturated hydrogenation on the active center consisting of Cu and Ni.

The Cu has the function of forming Ni/Cu alloy in the roasting process, effectively reduces the reduction temperature of the nickel in the reduction process, reduces the polymerization of the Pd at high temperature, and improves the dispersion degree of the main active component.

For hydrogenation reaction, generally, before the catalyst is applied, the hydrogenation catalyst needs to be reduced first to ensure that the active component exists in a metallic state, so that the catalyst can have hydrogenation activity. Because activation is a high temperature calcination process during catalyst preparation, the metal salt decomposes to metal oxides, which form clusters, which are typically nano-sized. Different oxides need to be reduced at different temperatures due to different chemical properties. However, for nano-sized metals, a critical temperature is around 200 ℃, and above this temperature, the aggregation of metal particles is very significant. Therefore, the reduction temperature of the active component is very important for the preparation method of the hydrogenation catalyst.

The idea of the invention for solving the problem of catalyst coking is as follows:

the selective hydrogenation reaction of alkyne takes place in the main active center of the composition, such as Pd, Rh, and macromolecules such as green oil produced in the reaction, and easily enter the macropores of the catalyst. In the macropores of the catalyst, a Ni/Cu component is loaded, wherein Ni has a saturation hydrogenation function, and the green oil component can perform a saturation hydrogenation reaction at an active center consisting of Ni/Cu. Because the double bonds are saturated by hydrogenation, the green oil component can not generate polymerization reaction any more or the polymerization reaction rate is greatly reduced, the chain growth reaction is terminated or delayed, a fused ring compound with huge molecular weight can not be formed, and the fused ring compound is easily carried out of the reactor by materials, so the coking degree on the surface of the catalyst is greatly reduced, and the service life of the catalyst is greatly prolonged.

The method for controlling the Ni/Cu alloy to be positioned in the catalyst macropores is that Ni/Cu is loaded in the form of microemulsion, and the grain diameter of the microemulsion is larger than the pore diameter of carrier micropores and smaller than the maximum pore diameter of macropores. The nickel and copper metal salts are contained in the microemulsion and, due to steric resistance, are difficult to access to the smaller size pores of the support and therefore mainly to the macropores of the support.

The invention is not particularly limited in the process of loading Ni, Cu and Pd in a microemulsion manner, and Ni, Cu and Pd can be distributed in macropores of the carrier as long as the particle size of the microemulsion with the particle size of more than 35nm and less than 300nm can be formed.

In the invention, the process of loading palladium by a solution method is carried out by a supersaturated impregnation method, the solution containing palladium enters pores more quickly due to the siphonage action of the pores, the palladium exists in the form of chloropalladate ions, and the palladium is quickly targeted because the ions can form chemical bonds with hydroxyl on the surface of a carrier, so that the faster the solution enters the pore channels, the faster the loading speed is. Therefore, the catalyst is more easily supported in the pores during the impregnation of Pd by the solution method.

In the invention, Cu and Ni are loaded together, so that the reduction temperature of Ni can be reduced, because NiO is required to be completely reduced independently, the reduction temperature is generally 450-500 ℃, Pd agglomeration can be caused at the temperature, and after the Cu/Ni alloy is formed, the reduction temperature can be reduced by more than 100 ℃ and reaches 350 ℃ compared with the reduction temperature of pure Ni, so that the Pd agglomeration in the reduction process is relieved.

In the invention, a small amount of Pd supported by the microemulsion is more preferably on the surface of the Ni/Cu alloy, so that the reduction temperature of Ni can be further reduced and can reach below 200 ℃ and as low as 150 ℃.

In the invention, the adopted carrier is required to have a bimodal pore distribution structure, the distribution range of large pores and small pores in bimodal pore distribution is not particularly limited in the invention, the carrier can be selected according to reaction characteristics such as raw materials, process conditions, catalyst active components and the like, and the particularly recommended carrier is large pores with the pore diameter of 70-300 nm, and the pore diameter of the small pores is 15-35 nm. For the same reason, the present invention is not particularly limited to the composition of Pd, Rh, Ni, Cu in the active component. Carrier Al₂O₃The crystal form is alpha, theta or a mixed crystal form thereof; the preferred catalyst support preferably contains at least 80% alumina.

In the present invention, the active component of the catalyst is not particularly limited, and may be selected according to the reaction characteristics, such as raw materials, process conditions, etc., and a catalyst is particularly recommended: the catalyst at least comprises Pd, Rh, Ni and Cu, wherein the Pd is loaded in a micro-emulsion mode and a solution mode, the Ni and the Cu are loaded in a micro-emulsion mode, the Rh is loaded in a solution mode, the mass of the catalyst is 100%, the content of the Pd loaded in the solution is 0.25-0.40%, preferably 0.30-0.35%, the weight ratio of the Rh to the Pd loaded in the solution is 1.5-6.0, preferably 2.0-4.5%, the content of the Ni is 5.0-10%, preferably 6.8-8.0%, and the weight ratio of the Cu to the Ni is 0.1-1.0, preferably 0.4-0.8.

In the invention, the Ni/Cu load of the catalyst is impregnated in a microemulsion form in the preparation process. The Pd loading is impregnated by two methods, namely a solution method and a microemulsion method, and the solution loading of Pd and Rh can be carried out by a supersaturated impregnation method.

The invention also proposes a microemulsion loading mode, which comprises the following steps: dissolving precursor salt in water, adding oil phase, surfactant and cosurfactant, and stirring to form microemulsion, wherein the oil phase is alkane or cycloalkane, the surfactant is ionic surfactant and/or nonionic surfactant, and the cosurfactant is organic alcohol.

In the present invention, the kind and addition amount of the oil phase, the surfactant and the co-surfactant are not particularly limited, and the kind and addition amount of the oil phase, the surfactant and the co-surfactant can be determined according to the pore structures of the precursor salt and the carrier.

The oil phase recommended by the invention is saturated alkane or cycloalkane, preferably C6-C8 saturated alkane or cycloalkane, preferably cyclohexane and n-hexane; the surfactant is an ionic surfactant and/or a nonionic surfactant, preferably the nonionic surfactant, and more preferably polyethylene glycol octyl phenyl ether or cetyl trimethyl ammonium bromide; the cosurfactant is organic alcohol, preferably C4-C6 alcohol, more preferably n-butanol and/or n-pentanol.

In the recommended microemulsion loading mode, the recommended weight ratio of the water phase to the oil phase is 2.0-3.0, the weight ratio of the surfactant to the oil phase is 0.15-0.50, the weight ratio of the surfactant to the cosurfactant is 1.0-1.2, and the particle size of the microemulsion is controlled to be larger than 35nm and smaller than 300 nm; preferably, the weight ratio of the water phase to the oil phase is 2.1 to 2.2, and the weight ratio of the surfactant to the oil phase is 0.30 to 0.50. The grain diameter of the microemulsion is larger than the maximum aperture of the small hole and smaller than the minimum aperture of the large hole, which is more beneficial to the loading of the active component, and the distribution of the active component, especially Ni and Cu, in the prepared catalyst is more uniform.

The sequence of the steps of Pd solution loading and microemulsion loading Ni/Cu is not limited; the microemulsion loading of Pd is carried out after the step of loading Ni and Cu by the microemulsion; the solution of Rh was supported after the solution supporting step of Pd. In the two loading processes using the two microemulsion methods, the particle sizes of the microemulsions may be the same or different, preferably the same.

The invention also provides a more specific preparation method of the selective hydrogenation catalyst, which comprises the following steps:

(1) dissolving precursor salt of Ni and Cu in water, adding metered oil phase, surfactant and cosurfactant, fully stirring to form microemulsion, controlling the particle size of the microemulsion to be more than 35nm and less than 300nm, adding a carrier into the prepared microemulsion, soaking for 0.5-4 hours, filtering out residual liquid, drying for 1-6 hours at 80-120 ℃, and roasting for 2-8 hours at 400-600 ℃. Obtaining a semi-finished product catalyst A;

(2) dissolving a precursor salt of Pd in water, adjusting the pH value to 1.8-2.8, adding the semi-finished catalyst A into a Pd salt solution, soaking and adsorbing for 0.5-4 h, drying at 100-120 ℃ for 1-4 h, and roasting at 400-550 ℃ for 2-6 h to obtain a semi-finished catalyst B;

(3) adding Rh salt into deionized water with the saturated water absorption of 80-110 of the semi-finished catalyst B to completely dissolve the Rh salt, soaking the semi-finished catalyst B in the prepared solution, shaking uniformly, precipitating for 0.5-2 h, drying at 100-120 ℃ for 1-4 hours, and roasting at 400-550 ℃ for 2-6 hours to obtain a semi-finished catalyst C;

(4) dissolving Pd precursor salt in water, adding metered oil phase, surfactant and cosurfactant, fully stirring to form microemulsion, controlling the particle size of the microemulsion to be more than 35nm and less than 300nm, adding the semi-finished catalyst C into the prepared microemulsion, soaking for 0.5-4 hours, filtering out residual liquid, drying for 1-6 hours at 80-120 ℃, and roasting for 2-8 hours at 400-600 ℃ to obtain the catalyst.

For one sample, the conditions of step (1) and step (4) may be the same, or different, preferably the same, so as to ensure that Pd is supported on the surface of the Ni/Cu alloy.

In the above 4 steps, the loading of step (3) is carried out after the loading of Pd by the solution method in step (2); step 4 is after step (1).

The Pd loading by the solution method and the Ni/Cu loading by the microemulsion method can be carried out in any order.

In the step (2), the solution method loading of Pd can adopt a supersaturated impregnation method.

In the step (3), the loading of Rh may be carried out by a supersaturated impregnation method.

The carrier in the step (1) is alumina or mainly alumina and Al₂O₃The crystal form is preferably alpha, theta or a mixed crystal form thereof. The alumina content in the catalyst carrier is preferably above 80%, and the carrier may also contain other metal oxides such as magnesia, titania, etc.

The carrier in the step (1) can be spherical, cylindrical, clover-shaped, dentate spherical, clover-shaped and the like.

The ratio of the large pore volume to the small pore volume of the carrier in the step (1) is not limited and is determined according to the loading content of the active component.

The precursor salts of Ni, Cu, Rh and Pd in the above steps are soluble salts, and can be nitrates, chlorides or other soluble salts thereof.

The reduction temperature of the catalyst of the invention before use is preferably 150-200 ℃.

The catalyst had the following characteristics: at the beginning of the hydrogenation reaction, the hydrogenation activity of palladium is high and is mainly distributed in the pores, so that the selective hydrogenation reaction of acetylene mainly occurs in the pores. With the prolonging of the operation time of the catalyst, a part of by-products with larger molecular weight are generated on the surface of the catalyst, and due to the larger molecular size, the substances enter the macropores more frequently and the retention time is longer, the hydrogenation reaction of double bonds can be generated under the action of the nickel catalyst, so that saturated hydrocarbon or aromatic hydrocarbon without isolated double bonds is generated, and substances with larger molecular weight are not generated any more.

The catalyst prepared by the method has the advantages that the initial activity and the selectivity are obviously improved compared with those of the traditional catalyst.

The catalyst of the invention has greatly increased green oil generation amount even if the raw material contains more heavy fractions, and the activity and the selectivity of the catalyst still have no trend of reduction.

Drawings

FIG. 1 is a graph showing the distribution of reduction temperature peaks of Ni/Cu.

FIG. 2 is a flow diagram of carbon three hydrogenation using a non-prehydrogenation process.

FIG. 3 is a carbon three hydrogenation flow diagram using a pre-hydrogenation process.

In the figure: 1-oil wash column; 2-water washing tower; 3, a heat exchanger; 4-alkaline washing tower; 5-a demethanizer; 6-deethanizer; 7-depropanizer; 8-carbon three hydrogenation reactor; 9-a front-end depropanizer; 10-a carbon two hydrogenation reactor; 11-compressor.

Detailed Description

The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.

The analysis and test method comprises the following steps:

comparison table: GB/T-5816;

pore volume: GB/T-5816;

the content of active components in the catalyst is as follows: atomic absorption method;

microemulsion particle size distribution of Ni/Cu alloy: a dynamic light scattering particle size analyzer, which is used for analyzing on an M286572 dynamic light scattering analyzer;

the conversion and selectivity in the examples were calculated according to the following formulas:

MAPD conversion (%). 100 × Δ MAPD/inlet MAPD content

Propylene selectivity (%) ═ 100 x Δ propylene/. DELTA.MAPD

Example 1

Carrier: a commercially available spherical alumina carrier with bimodal pore distribution and a diameter of 4mm is adopted, and 100g of the spherical alumina carrier is weighed after being calcined at high temperature for 4 hours. The calcination temperature and the physical index of the carrier are shown in Table 1.

Preparing a catalyst:

(1) weighing a certain amount of nickel nitrate, dissolving copper chloride in deionized water, adding a certain amount of cyclohexane, Triton X-100 and n-butanol, fully stirring to form a microemulsion, soaking 100g of the weighed carrier into the prepared microemulsion for 1 hour, washing the carrier to be neutral by using the deionized water, drying the carrier for 2 hours at 120 ℃, and roasting the carrier for 5 hours at 550 ℃. Obtaining a semi-finished product catalyst A.

(2) Weighing a certain amount of palladium nitrate, dissolving in deionized water, adjusting the pH value to 1, then dipping the semi-finished catalyst A into the prepared Pd salt solution, drying for 2 hours at 110 ℃ after dipping and adsorption for 1 hour, and roasting for 6 hours at 380 ℃ to obtain a semi-finished catalyst B.

(3) Weighing rhodium nitrate, preparing into a solution by using deionized water, adding a semi-finished catalyst B into the solution, shaking, drying for 3 hours at 110 ℃ after the solution is completely absorbed, and roasting for 4 hours at 500 ℃ to obtain the required catalyst.

The particle size of the microemulsion prepared in the catalyst preparation process and the content of each component in the catalyst are shown in table 2.

Before use, the mixture is placed in a fixed bed reaction device and is mixed with N₂:H₂Reducing the mixed gas at 350 ℃ for 12 h.

Example 2

Carrier: a commercially available spherical carrier with bimodal pore distribution and a diameter of 4mm is adopted, and the composition of the carrier is 90% of alumina and 10% of titanium oxide. After high-temperature roasting for 4 hours, 100g of the carrier is weighed, and the physical indexes of the carrier are shown in Table 1.

Preparing a catalyst:

1) weighing a certain mass of nickel nitrate, dissolving copper chloride in deionized water, adding a certain amount of cyclohexane, TritonX-100 and n-hexanol, and fully stirring to form microemulsion. The carrier is added into the prepared microemulsion for dipping for 1 hour, washed to be neutral by deionized water, dried for 2 hours at 120 ℃ and roasted for 5 hours at 550 ℃. Obtaining a semi-finished product catalyst A.

(2) Weighing a certain amount of palladium nitrate, dissolving the palladium nitrate in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. And adding the semi-finished catalyst A into the prepared microemulsion, soaking for 4 hours, washing to be neutral by using deionized water, drying for 4 hours at 90 ℃, and roasting for 2 hours at 600 ℃ to obtain a semi-finished catalyst B.

(3) Weighing a certain amount of palladium nitrate salt, dissolving in water, adjusting the pH value to 2, adding the semi-finished product B into a Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain a semi-finished product catalyst C.

(4) Weighing a certain amount of rhodium nitrate, dissolving the rhodium nitrate in deionized water, soaking the semi-finished catalyst C in the prepared solution, drying the semi-finished catalyst C for 3 hours at 110 ℃, and roasting the semi-finished catalyst C for 4 hours at 500 ℃ to obtain the finished catalyst.

Before use, the mixture is placed in a fixed bed reaction device and is mixed with N₂:H₂Reducing the mixed gas at the temperature of 170 ℃ for 12h under the condition of 1: 1.

Example 3

Carrier: a commercially available spherical alumina carrier with bimodal pore distribution and a diameter of 4mm was used. After high-temperature roasting for 4 hours, 100g of the carrier is weighed, and the physical indexes are shown in table 1.

Preparing a catalyst:

(1) weighing a certain amount of palladium nitrate salt, dissolving in water, adjusting the pH value to 2, adding the carrier into a Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain a semi-finished catalyst A.

(2) Weighing a certain amount of rhodium nitrate, dissolving the rhodium nitrate in deionized water, soaking the semi-finished catalyst A in the prepared solution, drying the semi-finished catalyst A for 3 hours at 110 ℃, and roasting the semi-finished catalyst A for 4 hours at 500 ℃ to obtain a semi-finished catalyst B.

(3) Weighing a certain amount of nickel nitrate and copper chloride, dissolving in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. Adding the semi-finished catalyst B into the prepared microemulsion, soaking for 4 hours, washing to be neutral by deionized water, drying for 4 hours at 90 ℃, and roasting for 2 hours at 600 ℃. Obtaining a semi-finished product catalyst C.

(4) Weighing a certain amount of palladium nitrate, dissolving the palladium nitrate in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. Adding the semi-finished catalyst C into the prepared microemulsion, soaking for 4 hours, washing to be neutral by deionized water, drying for 4 hours at 90 ℃, and roasting for 2 hours at 600 ℃. And obtaining the finished catalyst.

Before use, the mixture is placed in a fixed bed reaction device and is mixed with N₂:H₂Reducing the mixed gas at the temperature of 160 ℃ for 12h under the condition of 1: 1.

Example 4

Preparing a catalyst:

(1) weighing a certain amount of nickel nitrate and copper chloride, dissolving in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. The carrier is added into the prepared microemulsion for dipping for 4 hours, then is washed to be neutral by deionized water, is dried for 4 hours at the temperature of 90 ℃, and is roasted for 2 hours at the temperature of 600 ℃. Obtaining a semi-finished product catalyst A.

(2) Weighing a certain amount of palladium nitrate salt, dissolving in water, adjusting the pH value to 2, adding the semi-finished catalyst A into a Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain a semi-finished catalyst B.

(3) Weighing a certain amount of rhodium nitrate, dissolving the rhodium nitrate in deionized water, soaking the semi-finished catalyst B in the prepared solution, drying the semi-finished catalyst B for 3 hours at 110 ℃, and roasting the semi-finished catalyst B for 4 hours at 500 ℃ to obtain a semi-finished catalyst C.

Before use, the mixture is placed in a fixed bed reaction device and is subjected to reduction treatment for 12H at the temperature of 170 ℃ by using mixed gas with the molar ratio of N2 to H2 being 1: 1.

Example 5

Preparing a catalyst:

(2) Weighing a certain amount of palladium nitrate, dissolving the palladium nitrate in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. Adding the semi-finished catalyst A into the prepared microemulsion, soaking for 4 hours, washing to be neutral by deionized water, drying for 4 hours at 90 ℃, and roasting for 2 hours at 600 ℃. Obtaining a semi-finished product catalyst B.

(3) Weighing a certain amount of palladium nitrate salt, dissolving in water, adjusting the pH value to 2, adding the semi-finished catalyst B into a Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain a semi-finished catalyst C.

(4) Weighing a certain amount of rhodium nitrate, dissolving in deionized water, soaking the semi-finished catalyst C in the prepared solution, drying at 110 ℃ for 3 hours, and roasting at 500 ℃ for 4 hours to obtain the finished catalyst.

Before use, the mixture is placed in a fixed bed reaction device and is subjected to reduction treatment for 12H at the temperature of 150 ℃ by using mixed gas with the molar ratio of N2 to H2 being 1: 1.

Comparative example 1

Preparing a catalyst:

(1) weighing a certain amount of nickel nitrate, dissolving the nickel nitrate in 70ml of deionized water, adding a certain amount of cyclohexane, Triton X-100 and n-butanol, fully stirring to form a microemulsion, dipping the carrier into the prepared microemulsion, washing the carrier to be neutral by using the deionized water after dipping for 1 hour, drying the carrier for 2 hours at 120 ℃, and roasting the carrier for 5 hours at 550 ℃. A semi-finished catalyst A1 was obtained.

(2) Weighing a certain amount of palladium nitrate, dissolving in deionized water, adjusting the pH value to 1, then soaking the semi-finished catalyst A into the prepared Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain a semi-finished catalyst B1.

(3) Weighing rhodium nitrate, preparing a solution by using deionized water, immersing the semi-finished catalyst B1 into the prepared solution, shaking, drying for 3 hours at 110 ℃ after the solution is completely absorbed, and roasting for 4 hours at 500 ℃ to obtain the required catalyst.

Before use, the mixture is placed in a fixed bed reaction device and is mixed with N₂:H₂Reducing the mixed gas at 490 deg.c for 12 hr.

Comparative example 2

Carrier: a commercially available spherical carrier with bimodal pore distribution and a diameter of 4mm is adopted, and the composition of the carrier is 90% of alumina and 10% of titanium oxide. After high-temperature roasting for 4 hours, 100g of the carrier is weighed, and the physical indexes are shown in table 1.

Preparing a catalyst:

(1) weighing a certain amount of nickel nitrate, dissolving copper nitrate in deionized water, adding a certain amount of cyclohexane, 14.3g of Triton X-100 and 13.60g of n-hexanol, and fully stirring to form microemulsion. The carrier is added into the prepared microemulsion for dipping for 1 hour, washed to be neutral by deionized water, dried for 2 hours at 120 ℃ and roasted for 5 hours at 550 ℃. A semi-finished catalyst A1 was obtained.

(2) Weighing a certain amount of palladium nitrate salt, dissolving in water, adjusting the pH value to 2, adding the semi-finished catalyst A1 into a Pd salt solution, soaking and adsorbing for 1h, drying for 2h at 110 ℃, and roasting for 6h at 380 ℃ to obtain the finished catalyst.

Comparative example 3

Carrier: a commercially available spherical alumina support with monomodal pore distribution and a diameter of 4mm was used. After high-temperature roasting for 4 hours, 100g of the carrier is weighed, and the physical indexes are shown in table 1.

Preparing a catalyst:

(1) weighing a certain amount of palladium chloride salt, dissolving in water, adjusting the pH value to 3, adding the weighed carrier into a Pd salt solution, soaking and adsorbing for 2h, drying at 120 ℃ for 1h, and roasting at 450 ℃ for 4h to obtain a semi-finished catalyst A1.

(2) Weighing a certain amount of rhodium nitrate, dissolving the rhodium nitrate in deionized water, soaking the semi-finished catalyst A1 in the prepared solution, drying the solution for 4 hours at 100 ℃ after the solution is completely absorbed, and roasting the solution for 6 hours at 400 ℃ to obtain the required catalyst.

The contents of the components in the catalyst are shown in Table 2.

Comparative example 4

Preparing a catalyst:

(2) Weighing a certain amount of rhodium nitrate, dissolving in deionized water, adding the semi-finished catalyst A into the prepared solution, drying at 110 ℃ for 3 hours, and roasting at 500 ℃ for 4 hours to obtain a semi-finished catalyst B.

(3) Weighing a certain amount of nickel nitrate and ferric chloride, dissolving in water, adding a certain amount of cyclohexane and TritonX-100, and fully stirring 6.03g of n-hexanol to form microemulsion. Adding the semi-finished catalyst B into the prepared microemulsion, soaking for 4 hours, washing to be neutral by deionized water, drying for 4 hours at 90 ℃, and roasting for 2 hours at 600 ℃. And obtaining the finished catalyst.

TABLE 1 Carrier Properties in examples and comparative examples

TABLE 2 content of active components of catalysts in examples and comparative examples

The performance of the catalyst is evaluated in a fixed bed single-stage reactor. The loading of the catalyst is 50ml, the space velocity of the reaction materials is 70/h, the operating pressure is 2.5MPa, and the hydrogen/PDMA is 1.2. The reaction mass composition is shown in Table 3.

TABLE 3 reaction Material composition

Reaction mass	C₃H₄(PDMA)	C₃H₆	C₃H₈	C₄ ⁺
					Content (v/v%)	6	79	14	1

The catalyst evaluation results are shown in Table 4.

Catalysts

1, 2, 3 were from examples 1, 2, 3, respectively; comparative examples 1, 2, 3, 4 were derived from comparative examples 1, 2, 3, 4, respectively.

TABLE 4 catalyst evaluation results

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A preparation method of a carbon three-fraction selective hydrogenation catalyst, the carrier of the catalyst is alumina or mainly alumina, and has a bimodal pore distribution structure, the active component of the catalyst at least contains Pd, Rh, Ni and Cu, and is characterized in that the active component Pd is loaded in two modes of solution and microemulsion; rh is loaded by a solution method, and Pd loaded by the solution method is mainly distributed in pores of the carrier; ni and Cu are loaded by a microemulsion impregnation method, and Pd loaded by microemulsion is mainly distributed in macropores of the carrier.

2. The method for preparing the carbon three-fraction selective hydrogenation catalyst according to claim 1, wherein a majority of the Pd is loaded by using a solution, and a small portion of the Pd is loaded in a microemulsion manner, so that the portion of the Pd is mainly distributed in the macropores of the carrier.

3. The method for preparing the carbon three-fraction selective hydrogenation catalyst according to claim 1, wherein the pore diameter of the small pores of the carrier is 15-35 nm, the pore diameter of the large pores is 70-300 nm, and the particle size of the microemulsion is controlled to be larger than 35nm and smaller than 300nm when the microemulsion is loaded.

4. The method for preparing a catalyst for selective hydrogenation of carbon three-cut as claimed in claim 1 or 2, wherein the loading process in microemulsion mode comprises: dissolving precursor salt in water, adding oil phase, surfactant and cosurfactant, and stirring to form microemulsion, wherein the oil phase is alkane or cycloalkane, the surfactant is ionic surfactant and/or nonionic surfactant, and the cosurfactant is organic alcohol.

5. The method for preparing a carbon three-fraction selective hydrogenation catalyst according to claim 1, wherein the carrier Al is₂O₃The crystal form is alpha, theta or a mixed crystal form thereof; the alumina content in the catalyst carrier is more than 80%.

6. The method for preparing a selective hydrogenation catalyst for carbon three-cut as claimed in claim 4, wherein the microemulsion contains 2.0-3.0 wt% of water phase and oil phase, 0.15-0.50 wt% of surfactant and oil phase, and 1.0-1.2 wt% of surfactant and co-surfactant.

7. The method for preparing a carbon three-cut selective hydrogenation catalyst according to claim 1, wherein the step of loading Pd on microemulsion is after the step of loading Ni and Cu on microemulsion.

8. The method for preparing a carbon three-cut selective hydrogenation catalyst according to claim 1, wherein the solution-supporting of Pd and Rh is carried out by supersaturated impregnation.

9. The method for preparing the catalyst for selective hydrogenation of carbon three-cut as claimed in claim 1, wherein the order of the solution loading of Pd and the microemulsion loading of Ni/Cu is not limited during the preparation of the catalyst.

10. The method for preparing a carbon three-cut selective hydrogenation catalyst according to claim 1, wherein the step of loading Pd on microemulsion is after the step of loading Ni and Cu on microemulsion during the preparation process of the catalyst.

11. The method for preparing a catalyst for selective hydrogenation of carbon three-cut as claimed in claim 1, wherein the step of loading Rh in the catalyst preparation process by the solution method is after the step of loading Pd in the catalyst preparation process by the solution method.

12. The method for preparing a carbon three-fraction selective hydrogenation catalyst according to claim 1, wherein the preparation process specifically comprises the following steps:

(1) preparing Pd into an active component impregnation liquid, adjusting the pH value to be 1.8-2.8, adding a carrier into the Pd active component impregnation liquid, performing impregnation and adsorption for 0.5-4 h, drying for 1-4 h at 100-120 ℃, and roasting for 2-6 h at 400-550 ℃ to obtain a semi-finished catalyst A;

(2) dissolving precursor salts of Ni and Cu in water, adding metered oil phase, surfactant and cosurfactant, fully stirring to form microemulsion, controlling the particle size of the microemulsion to be larger than the aperture of small holes of a carrier and smaller than the aperture of large holes of the carrier, adding the semi-finished catalyst A into the prepared microemulsion, soaking for 0.5-4 h, filtering out residual liquid, drying for 1-6 h at 80-120 ℃, and roasting for 2-8 h at 400-600 ℃ to obtain a semi-finished catalyst B;

(3) loading Rh by a supersaturation impregnation method, namely, preparing Rh salt which is 80-110% of the saturated water absorption of a carrier, precipitating the Rh salt for 0.5-2 h after loading Rh on a semi-finished product catalyst B, drying the semi-finished product catalyst B at 100-120 ℃ for 1-4 h, and roasting the semi-finished product catalyst B at 400-550 ℃ for 4-6 h to obtain a semi-finished product catalyst C;

(4) dissolving Pd precursor salt in water, adding metered oil phase, surfactant and cosurfactant, fully stirring to form microemulsion, controlling the particle size of the microemulsion to be larger than 35nm and smaller than 300nm, adding the semi-finished catalyst C into the prepared microemulsion, soaking for 0.5-4 hours, filtering out residual liquid, drying for 1-6 hours at 80-120 ℃, and roasting for 2-8 hours at 400-600 ℃ to obtain the catalyst.