CN119346183A

CN119346183A - A highly efficient and stable propylene selective superposition catalyst and its preparation method

Info

Publication number: CN119346183A
Application number: CN202411672922.7A
Authority: CN
Inventors: 刘建华; 杨坚; 郧栋; 刘褀壬; 许传芝; 夏春谷
Original assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Current assignee: Lanzhou Institute of Chemical Physics LICP of CAS
Priority date: 2024-11-21
Filing date: 2024-11-21
Publication date: 2025-01-24

Abstract

The invention relates to a high-efficiency stable propylene selective superposition catalyst, which consists of a layered hydrotalcite main body layer plate structure comprising divalent and trivalent metal cations and interlayer anions, a metal oxide auxiliary agent and a coated core-shell structure. Meanwhile, the invention also discloses a preparation method of the catalyst. The invention obtains the coated core-shell structure through reasonably regulating and controlling the active components and the acid sites and through surface modification, has low branching degree in selectively overlapping olefin products (C6, C9 and C12), and has the excellent characteristics of simple preparation process, regeneration, reuse, low cost and the like.

Description

Efficient and stable propylene selective superposition catalyst and preparation method thereof

Technical Field

The invention relates to the technical field of catalysts, in particular to a high-efficiency stable propylene selective superposition catalyst and a preparation method thereof.

Background

Propylene is an important chemical raw material, mainly used for producing polypropylene, acrylonitrile, propylene oxide, isopropyl benzene (phenol/acetone), oxo alcohol (butyl/octyl alcohol), acrylic acid, isopropyl alcohol and the like, and other uses also comprise alkylate, catalytic selective lamination, dimerization and the like, and is an important petrochemical basic raw material next to ethylene. The propylene is produced by petroleum routes, namely steam cracking and catalytic cracking processes, and in recent years, new processes of coal chemical industry such as Methanol To Olefins (MTO) and Methanol To Propylene (MTP), propane dehydrogenation, carbon tetraolefin disproportionation and the like are increasingly mature, such as propylene produced by tens of enterprises such as China's middle sea shell, china's Huaning coal, wanhua chemistry, china's combined creation, saika, qilu's petrochemical industry, yangzi petrochemical industry, shanghai petrochemical industry and the like, the total production capacity reaches 4000 tens of thousands of tons/year, and the consumption of propylene is gradually behind the ever-increasing propylene monomer yield, so that development of efficient and stable processes for converting propylene into chemical intermediates with high added value is an urgent need and a challenging opportunity in the chemical industry.

The heterogeneous catalysis propylene selective lamination is one of the very promising paths, can prepare a series of chemical products, such as dimer 4-methyl-1-pentene, can be used for synthesizing high-performance polyolefin, can be used as a high-octane gasoline blending component, can also be used for preparing hexacarbon alcohol to be used as a gold mineral emulsion selector, can be used for preparing nonionic surfactants, and can be used for lubricating oil additives, plasticizers and the like. The propylene selective lamination process which occupies monopoly abroad is a solid phosphoric acid catalyst used in SPAC process developed by UOP company in the United states, and is prepared by taking diatomite as a carrier to load phosphoric acid, as reported in patents US4097365 and US 4738767. Boric acid is added to stabilize the framework structure on the basis of the national Shanghai petrochemical institute, and T-49 and T-99 catalysts are developed as reported in patent CN1078663A, CN 1285241A. The solid phosphoric acid catalyst is used in industry to realize propylene selective superposition at the temperature of 150-200 ℃ and the pressure of 4-5 MPa, and the single pass conversion rate is 40-80%, but the catalyst has the fatal defects of easy mud formation and agglomeration, high continuous operation difficulty of the process, strict control of water injection in the reaction process is needed to prolong the service life, the maximum is prolonged for half a year, the catalyst cannot be regenerated after deactivation, and in addition, the process has the advantages of large olefin cracking degree, wide carbon number distribution and poor economy. Compared with the traditional solid phosphoric acid catalyst, the catalyst for synthesizing the solid phosphoric acid by using the molecular sieve, the aluminosilicate and the activated carbon is as reported in patent US5051386, but the defect of the catalyst cannot be fundamentally changed. The solid acid catalyst has better activity in the preparation of high-value-added high-carbon olefin products by polymerizing low-carbon olefin, represented by MOGD technology developed by Mobil company, takes HZSM-25 pore zeolite molecular sieve as catalyst and Al ₂O₃ as cocatalyst, and obtains about 80% of diesel oil component under the reaction condition of T=190-310℃, p =4-10 MPa. The alumina or alumina/silica is used as a carrier to load metal sulfate substances, as reported in patents US3959400 and CN1193552A, CN1077452C, the propylene conversion rate is more than 90%, wherein the sum of the selectivities of the selectively overlapped products nonene and dodecene is about 70%, but the catalyst has strong acidity to cause cracking isomerization of the selectively overlapped products, the carbon number distribution is wide, and the requirement of low branching degree of the desired olefin oligomer cannot be met.

Layered composite metal hydroxides (LDHs) are assembled orderly from laminate metal cations and interlayer anions with a two-dimensional structure, and have a plurality of excellent properties such as adjustability, adsorptivity, memory effect, topological invariance, surface acidity and alkalinity and the like. The catalyst has great potential application in heterogeneous catalysis, and by adjusting unique physical and chemical properties, including microstructure, surface/interface defect structure and surface acid/alkali sites, the catalyst becomes an important carrier material, and particularly has important application in the construction of dual-function or multifunctional heterogeneous catalysts.

In summary, the heterogeneous catalytic propylene selective polymerization reaction mainly has the problems of insufficient catalyst stability, serious isomerization of selective polymerization olefin products and the like.

Disclosure of Invention

The invention aims to solve the technical problem of providing a high-efficiency stable propylene selective polymerization catalyst which is simple to prepare, renewable and reusable.

The invention aims to provide a preparation method of the efficient and stable propylene selective polymerization catalyst.

In order to solve the problems, the efficient and stable propylene selective lamination catalyst is characterized by comprising a layered hydrotalcite main layer plate structure comprising divalent and trivalent metal cations and interlayer anions, a metal oxide auxiliary agent and a coated core-shell structure.

The divalent and trivalent metal cations are two or more of Ni, fe, co, cu, mg, al, and the molar ratio of the divalent cations to the trivalent cations is 1:4-4:1.

The metal oxide auxiliary agent is one or more of ZrO ₂、TiO₂、ZnO₂、SiO₂, caO and MgO, and the content of the metal oxide auxiliary agent is 5-20% of the mass of the catalyst.

The preparation method of the efficient and stable propylene selective polymerization catalyst is characterized in that the method is characterized in that a layered hydrotalcite main body laminate structure with adjustable active components is compounded with a metal oxide auxiliary agent, and then the surface modification is carried out on the layered hydrotalcite main body laminate structure to obtain the catalyst with a coated core-shell structure.

The preparation method of the efficient and stable propylene selective polymerization catalyst comprises the following steps:

⑴ Preparing nitrate aqueous solution or carbonate aqueous solution of divalent and trivalent metal cations and alkali solution of anions respectively, wherein the molar concentration of the metal cations in the salt solution is 0.1% -1%, the molar concentration of the anions in the alkali solution is 0.5% -5%, and then preparing layered hydrotalcite by a coprecipitation method from the nitrate aqueous solution or the carbonate aqueous solution and the alkali solution, wherein N is the metal cations;

⑵ Adding a metal oxide auxiliary agent into the layered hydrotalcite, aging for 12-24 hours in an oil bath at 50-80 ℃, filtering, washing with deionized water for 4-8 times, and filtering to obtain a filter cake, and drying at 70-110 ℃ for 12-24 hours to obtain N-LDHs/MO _x;

⑶ The prepared N-LDHs/MO _x is ground and screened to obtain precursor powder particles with the particle size larger than 100 meshes, the precursor powder particles are immersed and dissolved in a step-by-step immersing method to obtain a surface modifier, the surface modifier is uniformly stirred after immersion, the surface modifier is firstly placed in an oven to be dried at 70-110 ℃ for 12-24 h, and then placed in a roasting furnace to be roasted at 400-600 ℃ for 4-8 h in an inert atmosphere, so that the catalyst N-LDHs/MO _x @modifier with a coated core-shell structure is obtained.

The alkali solution in the step ⑴ is an aqueous solution of sodium hydroxide and sodium carbonate mixed according to any volume ratio.

The surface modifier in the step ⑶ is C or/and N modifier and Si or/and Al modifier, wherein the C or/and N modifier is one or more of melamine, polyethylene glycol, sucrose, glucose, mannitol and sorbitol, the addition amount of the C or/and N modifier is 0.5-3% of the catalyst, deionized water is adopted for dissolution, the Si or/and Al modifier is one or more of ethyl orthosilicate, methyl orthosilicate, aluminum isopropoxide and aluminum sec-butoxide, and the addition amount of the Si or/and Al modifier is 1-5% of the mass of the catalyst, and alcohol is adopted for dissolution.

The application of the catalyst in the process of preparing C6, C9 and C12 olefins is characterized in that the catalyst is contacted with propylene raw materials in a fixed bed reactor for selective polymerization reaction, wherein the contact conditions comprise the temperature of 80-150 ℃, the pressure of 2.0-5.0 megapascals and the hourly mass space velocity of the raw materials of 0.1-5.0 h ^-1.

The mass fraction of olefin in the propylene raw material is more than 99%.

The nitride in the propylene raw material is less than 1ppm, the sulfide is less than 5ppm, and the oxygen-containing compound is less than 20ppm.

Compared with the prior art, the invention has the following advantages:

The catalyst provided by the invention has a layered hydrotalcite main body laminate structure with adjustable active components, provides a special reaction channel for reactant propylene molecules, reasonably adjusts and distributes the active components and acid sites, and obtains a coated core-shell structure catalyst through surface modification, and has the characteristics of high olefin selective superposition activity, good stability and regeneration performance, and the preparation method is simple, the cost is low, and the obtained selective superposition olefin product has low branching degree. Experiments show that the propylene conversion rate is 85% -65% in the process condition range, wherein the C6 olefin selectivity is 45% -60%, the C9 olefin selectivity is 20% -30%, and the C12 olefin selectivity is 10% -20%.

Drawings

The following describes the embodiments of the present invention in further detail with reference to the drawings.

FIG. 1 is a catalyst provided in example 1 of the present invention.

Fig. 2 is an XRD characterization of the catalyst provided in example 1 of the present invention.

Fig. 3 is a TEM characterization of the catalyst provided in example 1 of the present invention.

FIG. 4 is a representation of the NH ₃ -TPD of the catalyst provided in example 1 of the present invention.

Detailed Description

The catalyst consists of layered hydrotalcite main layer plate structure with bivalent and trivalent metal cations and interlayer anions intercalated, metal oxide assistant and coated core-shell structure.

Wherein the divalent and trivalent metal cations are two or more of Ni, fe, co, cu, mg, al, and the molar ratio of the divalent cations to the trivalent cations is 1:4-4:1.

The preparation process of efficient stable propylene selective laminated catalyst includes compounding layered hydrotalcite main layer structure with adjustable active component and metal oxide assistant, and surface modification to obtain the coated core-shell catalyst.

The specific process is as follows:

⑴ Preparing nitrate aqueous solution or carbonate aqueous solution of divalent and trivalent metal cations and alkali solution of anions respectively, wherein the molar concentration of the metal cations in the salt solution is 0.1% -1%, the molar concentration of the anions in the alkali solution is 0.5% -5%, and then preparing layered hydrotalcite by a coprecipitation method from the nitrate aqueous solution or carbonate aqueous solution and the alkali solution, wherein N is the metal cations.

Wherein the alkali solution is an aqueous solution of sodium hydroxide and sodium carbonate mixed according to any volume ratio. The pH value of the solution is kept at 7-10 in the preparation process.

⑵ Adding a metal oxide auxiliary agent into layered hydrotalcite, aging for 12-24 hours in an oil bath at 50-80 ℃, filtering, washing with deionized water for 4-8 times, filtering, and drying the obtained filter cake at 70-110 ℃ for 12-24 hours to obtain the N-LDHs/MO _x.

⑶ Grinding the prepared N-LDHs/MO _x by using a mortar, sieving, grinding and sieving to obtain precursor powder particles with the particle size of more than 100 meshes, and impregnating the precursor powder particles with the dissolved surface modifier by adopting a step-by-step impregnation method. The surface modifier is one or more of C or/and N modifier and Si or/and Al modifier, wherein the C or/and N modifier is one or more of melamine, polyethylene glycol, sucrose, glucose, mannitol and sorbitol, the addition amount of the C or/and N modifier is 0.5-3% of that of the catalyst, deionized water is adopted for dissolution, and the Si or/and Al modifier is one or more of ethyl orthosilicate, methyl orthosilicate, aluminum isopropoxide and aluminum sec-butoxide, the addition amount of the Si or/and Al modifier is 1-5% of that of the catalyst, and alcohol is adopted for dissolution.

And after the impregnation is finished, uniformly stirring in a crucible, firstly placing in an oven to dry at 70-110 ℃ for 12-24 hours, and then placing in a roasting furnace to roast at 400-600 ℃ for 4-8 hours in an inert atmosphere, thus obtaining the catalyst N-LDHs/MO _x @modifier with a coated core-shell structure.

The catalyst is applied to the preparation of C6, C9 and C12 olefins, and the catalyst is contacted with propylene raw materials in a fixed bed reactor for selective superposition reaction, wherein the contact conditions comprise the temperature of 80-150 ℃, the pressure of 2.0-5.0 megapascals, the hourly mass space velocity of raw material liquid of 0.1-5.0 h ^-1, preferably the temperature of 80-110 ℃, the pressure of 2.0-3.0 megapascals and the hourly mass space velocity of raw material liquid of 0.4-2.0 h ^-1.

Wherein the mass fraction of olefin in the propylene raw material is more than 99 percent.

The propylene material has less than 1ppm of nitrides (basic or non-basic), less than 5ppm of sulfides (such as thioether, hydrosulfide and carbonyl sulfide), and less than 20ppm of oxygen-containing compounds (such as water, alcohol, ketone, ether, etc.).

The main products generated by the selective superposition of propylene are C6, C9 and C12 olefin products, the C6, C9 and C12 products with the purity of more than 99 percent are respectively obtained through reduced pressure rectification, the obtained selective superposition olefin products are hydrogenated into alkane, and the components of the selective superposition olefin products are determined.

Example 1

(1) Ni(NO₃)₂·6H₂0：77.86g,Ca(NO₃)₂·4H₂0：8.42g,Mg(NO₃)₂·6H₂0：15.9g,Al(NO₃)₃·9H₂0：55.2g, Was weighed and dissolved in 680ml deionized water to obtain a metal salt solution. 40.0g of NaOH and 21.2g of Na ₂CO₃ are weighed and dissolved in 200ml of deionized water to obtain an alkali solution. Placing 1000ml of a three-mouth bottle in an oil bath pot, simultaneously dropwise adding a salt solution and an alkali solution, keeping the pH of the mixed solution at about 9 under continuous stirring, weighing 40g of 30% by mass of silica sol after the dropwise adding is finished, weighing 15g of 30% by mass of titanium sol, adding the titanium sol into the three-mouth bottle, stirring for 0.5h, raising the temperature of the oil bath to 80 ℃, standing and aging for 24h, filtering, washing with deionized water for 4 times, and drying the obtained filter cake at 100 ℃ for 24h to obtain NiCa-LDHs/SiO ₂-TiO₂.

(2) Grinding the prepared NiCa-LDHs/SiO ₂-TiO₂ by using a mortar, weighing 20.0g of particles larger than 100 meshes, placing the particles in a crucible, dissolving 2.0g of melamine by using 10g of deionized water, dissolving 0.5g of aluminum sec-butoxide by using 5g of absolute ethyl alcohol, dissolving 0.5g of ethyl orthosilicate by using 5g of absolute ethyl alcohol, gradually slowly adding catalyst powder, uniformly stirring in the crucible, placing in a baking oven for drying at 100 ℃ for 24 hours, and then placing in a baking furnace for baking at 500 ℃ for 3 hours under the nitrogen atmosphere to obtain the C, N, si, al modified NiCa-LDHs/SiO ₂-TiO₂ @ CNSiAl catalyst, as shown in figure 1.

The catalyst of example 1 was characterized by its crystalline structure, as shown in fig. 2, and was predominantly the diffraction peak of TiO ₂. And meanwhile, particle dispersion characterization is carried out, and as shown in fig. 3, the metal particles are uniformly dispersed.

The acidity of the catalyst of example 1 was characterized, as shown in fig. 4, indicating that the catalyst had certain weak acid sites and medium strong acid sites.

Tabletting the solid particles in a tabletting machine under the pressure of 10MPa, grinding and sieving after tabletting, and taking the particles with 20-40 meshes for evaluating the catalytic performance.

The catalyst is used for the selective polymerization reaction of propylene at the reaction temperature of 80 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 0.8h ^-1, liquid products are collected by a wide-mouth bottle after 24h operation, and the products are analyzed by gas chromatography, so that the propylene conversion rate is 88.6%, the C6 product selectivity is 57.2%, the C9 product selectivity is 28.1% and the C12 product selectivity is 11.5%.

Example 2

(1) Ni(NO₃)₂·6H₂0：43.70g,Mg(NO₃)₂·6H₂0：3.82g,Al(NO₃)₃·9H₂0：19.05g, Was weighed and dissolved in 680ml deionized water to obtain a metal salt solution. 40.0g of NaOH and 21.2g of Na ₂CO₃ are weighed and dissolved in 200ml of deionized water to obtain an alkali solution. And (3) placing 1000ml of a three-port bottle in an oil bath pot, simultaneously dropwise adding a salt solution and an alkali solution, keeping the pH of the mixed solution at about 10 under continuous stirring, weighing 5.0g of ZrO ₂ after the dropwise adding, adding into the three-port bottle, stirring for 0.5h, raising the temperature of the oil bath to 70 ℃, standing, ageing for 24h, filtering, washing with deionized water for 4 times, and drying the obtained filter cake at 100 ℃ for 24h to obtain Ni-LDHs/ZrO ₂.

(2) Grinding the prepared Ni-LDHs/ZrO ₂ by using a mortar, weighing 20.0g of particles larger than 100 meshes, placing the particles in a crucible, dissolving 1.0g of mannitol by using 10g of deionized water, dissolving 0.5g of methyl orthosilicate by using 10g of absolute methanol, slowly adding catalyst powder step by step, uniformly stirring in the crucible, placing in a baking oven, drying at 100 ℃ for 24 hours, and then placing in a baking furnace, and baking at 400 ℃ for 6 hours in a nitrogen atmosphere to obtain the C, si modified Ni-LDHs/ZrO ₂ @CSI catalyst. Tabletting the solid particles in a tabletting machine under the pressure of 10MPa, grinding and sieving after tabletting, and taking the particles with 20-40 meshes for evaluating the catalytic performance.

The catalyst is used for the selective polymerization reaction of propylene at the reaction temperature of 100 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 0.8h ^-1, liquid products are collected by a wide-mouth bottle after 24h operation, and the products are analyzed by gas chromatography, so that the propylene conversion rate is 52.4%, the C6 product selectivity is 47.6%, the C9 product selectivity is 27.2% and the C12 product selectivity is 17.6%.

Example 3

(1) Ni(NO₃)₂·6H₂0：40.87g,Co(NO₃)₃·6H₂0：5.45g,Mg(NO₃)₂·6H₂0：3.82g,Al(NO₃)₃·9H₂0：19.05g, Was weighed and dissolved in 680ml deionized water to obtain a metal salt solution. 40.0g of NaOH and 21.2g of Na ₂CO₃ are weighed and dissolved in 200ml of deionized water to obtain an alkali solution. And (3) placing 1000ml of a three-port bottle in an oil bath pot, simultaneously dropwise adding a salt solution and an alkali solution, keeping the pH of the mixed solution at about 9 under continuous stirring, weighing 5.0g of TiO ₂ after the dropwise adding, adding into the three-port bottle, stirring for 0.5h, raising the temperature of the oil bath to 80 ℃, standing, ageing for 24h, filtering, washing with deionized water for 4 times, and drying the obtained filter cake at 100 ℃ for 24h to obtain NiCo-LDHs/TiO ₂.

(2) Grinding the prepared NiCo-LDHs/TiO ₂ by using a mortar, weighing 20.0g of particles larger than 100 meshes, placing the particles in a crucible, dissolving 1.5g of glucose in 10g of deionized water and 0.5g of aluminum isopropoxide in 10g of isopropanol, slowly adding catalyst powder step by step, uniformly stirring in the crucible, placing in a baking oven, drying at 100 ℃ for 24 hours, and then placing in a baking furnace, and baking at 500 ℃ for 3 hours in a nitrogen atmosphere to obtain the C, al modified NiCo-LDHs/TiO ₂ @CAl catalyst. Tabletting the solid particles in a tabletting machine under the pressure of 10MPa, grinding and sieving after tabletting, and taking the particles with 20-40 meshes for evaluating the catalytic performance.

The catalyst is used for the selective polymerization reaction of propylene at the reaction temperature of 90 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 0.4h ^-1, liquid products are collected by a wide-mouth bottle after 24h operation, and the products are analyzed by gas chromatography, so that the propylene conversion rate is 68.4%, the C6 product selectivity is 65.2%, the C9 product selectivity is 21.2% and the C12 product selectivity is 10.5%.

Example 4

(1) Ni(NO₃)₂·6H₂0：39.06g,Fe(NO₃)₃·9H₂O：18.1g,Mg(NO₃)₂·6H₂0：3.82g,Al(NO₃)₃·9H₂0：19.05g, Was weighed and dissolved in 680ml deionized water to obtain a metal salt solution. 40.0g of NaOH and 21.2g of Na ₂CO₃ are weighed and dissolved in 200ml of deionized water to obtain an alkali solution. Placing 1000ml of a three-port bottle in an oil bath pot, simultaneously dropwise adding a salt solution and an alkali solution, keeping the pH of the mixed solution at about 9 under continuous stirring, weighing 15g of 30% titanium sol after the dropwise adding is finished, weighing 1.5g of SiO ₂, simultaneously adding into the three-port bottle, stirring for 0.5h, raising the temperature of the oil bath to 80 ℃, standing and aging for 24h, filtering, washing with deionized water for 4 times, and drying the obtained filter cake at 100 ℃ for 24h to obtain NiFe-LDHs/TiO ₂-SiO₂.

(2) Grinding the prepared NiFe-LDHs/TiO ₂-SiO₂ by using a mortar, weighing 20.0g of particles larger than 100 meshes, placing the particles in a crucible, dissolving 2.0g of polyethylene glycol by using 10g of deionized water and 0.8g of aluminum sec-butoxide by using 10g of sec-butyl alcohol, slowly adding catalyst powder step by step, uniformly stirring in the crucible, placing in an oven, drying at 100 ℃ for 24 hours, and then placing in a roasting furnace, roasting at 550 ℃ for 3 hours in a nitrogen atmosphere to obtain the C, al modified NiFe-LDHs/TiO ₂-SiO₂ @CAl catalyst. Tabletting the solid particles in a tabletting machine under the pressure of 10MPa, grinding and sieving after tabletting, and taking the particles with 20-40 meshes for evaluating the catalytic performance.

The catalyst is used for the selective polymerization reaction of propylene at the reaction temperature of 90 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 1.2h ^-1, liquid products are collected by a wide-mouth bottle after 24h operation, and the products are analyzed by gas chromatography, so that the propylene conversion rate is 76.3%, the C6 product selectivity is 58.6%, the C9 product selectivity is 28.2% and the C12 product selectivity is 10.7%.

Example 5

(1) Ni(NO₃)₂·6H₂0：77.86g,Cu(NO₃)₂·3H₂O：15.2g,Mg(NO₃)₂·6H₂0：15.9g,Al(NO₃)₃·9H₂0：55.2g, Was weighed and dissolved in 680ml deionized water to obtain a metal salt solution. 40.0g of NaOH and 21.2g of Na ₂CO₃ are weighed and dissolved in 200ml of deionized water to obtain an alkali solution. Placing 1000ml of three-mouth bottles in an oil bath pot, simultaneously dropwise adding a salt solution and an alkali solution, keeping the pH of the mixed solution at about 9 under continuous stirring, weighing 35g of silica sol with the mass fraction of 30% after the dropwise adding is finished, weighing 2.5g of CaO, simultaneously adding the silica sol into the three-mouth bottles, stirring for 0.5h, raising the temperature of the oil bath to 80 ℃, standing and ageing for 24h, filtering, washing with deionized water for 4 times, and drying the obtained filter cake at 100 ℃ for 24h to obtain NiCu-LDHs/SiO ₂ -CaO.

(2) Grinding the prepared NiCu-LDHs/SiO ₂ -CaO by using a mortar, weighing 20.0g of particles larger than 100 meshes, placing the particles in a crucible, dissolving 2.0g of melamine by using 10g of deionized water, dissolving 0.5g of ethyl orthosilicate by using 10g of absolute ethyl alcohol, slowly adding catalyst powder, uniformly stirring in the crucible, placing in a baking oven at 100 ℃ for drying for 24 hours, and then placing in a baking furnace for baking at 550 ℃ for 3 hours under nitrogen atmosphere to obtain the C, N, si modified NiCu-LDHs/SiO ₂ -CaO@CNSi catalyst. Tabletting the solid particles in a tabletting machine under the pressure of 10MPa, grinding and sieving after tabletting, and taking the particles with 20-40 meshes for evaluating the catalytic performance.

The catalyst is used for the selective polymerization reaction of propylene at the reaction temperature of 110 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 0.8h ^-1, liquid products are collected by a wide-mouth bottle after 24h operation, and the products are analyzed by gas chromatography, so that the propylene conversion rate is 78.2%, the C6 product selectivity is 53.2%, the C9 product selectivity is 30.1% and the C12 product selectivity is 14.4%.

Comparative example 1

NiCa-LDHs/SiO ₂-TiO₂ precursor was prepared as in example 1, except that it was not surface modifier modified and the catalyst was used for propylene selective polymerization evaluation conditions as in example 1. The propylene conversion was 53.8%, the C6 product selectivity was 54.4%, the C9 product selectivity was 30.8%, and the C12 product selectivity was 11.6%.

Comparative example 2

Ni-LDHs/ZrO ₂ precursor was prepared as in example 2, except that the surface modifier modification was not performed, and the catalyst was used for the evaluation of propylene selective polymerization reaction under the same conditions as in example 2. The propylene conversion was analyzed to give a C6 product selectivity of 58.2%, a C9 product selectivity of 28.6% and a C12 product selectivity of 10.5%.

Comparative example 3

A NiCo-LDHs/TiO ₂ precursor was prepared as in example 3, except that the surface modifier modification was not performed and the catalyst was used for propylene selective polymerization evaluation conditions as in example 3. The propylene conversion was analyzed to give a C6 product selectivity of 52.6%, a C9 product selectivity of 28.4% and a C12 product selectivity of 17.1%.

Comparative example 4

NiFe-LDHs/TiO ₂-SiO₂ was prepared as in example 4, except that the surface modifier modification was not performed, and the catalyst was used for propylene selective polymerization evaluation conditions as in example 4. The propylene conversion was analyzed to be 68.9%, the C6 product selectivity was 55.4%, the C9 product selectivity was 25.4%, and the C12 product selectivity was 16.8%.

Comparative example 5

NiCu-LDHs/SiO ₂ -CaO was prepared as in example 5, except that the surface modifier modification was not performed, and the catalyst was used for the evaluation of propylene selective polymerization reaction under the same conditions as in example 5. The propylene conversion was analyzed to give a C6 product selectivity of 59.7%, a C9 product selectivity of 21.2% and a C12 product selectivity of 11.2%.

Examples 6 to 9

This example illustrates the catalytic reaction effect of the catalysts of the present invention having different surface modifying additive levels.

The same catalyst preparation method as used in example 1 was used to prepare catalysts with different surface modifier contents for the selective polymerization of propylene under the same conditions as in example 1, and the results are shown in Table 1.

TABLE 1

Surface modifier content%	Propylene conversion/%	C6 olefin Selectivity%	C9 olefin selectivity%	C12 olefin selectivity/%
					0.5	62.5	52.9	30.2	16.7
1.0	71.3	54.1	28.6	14.6
					3.0	78.3	50.6	32.3	12.4
5.0	51.3	58.2	24.5	10.9

As can be seen from Table 1, the catalytic reaction effect of the catalysts of the present invention is affected by the different surface modifying additive content.

Examples 10 to 13

This example illustrates the process conditions suitable for use in the present invention, wherein the mass space velocity (WHSV) of the feedstock is 0.4 to 2.0h ^-1.

The catalyst of example 1 was used to vary the mass space velocity of the feedstock, maintain the reaction temperature and pressure constant, and was used in the propylene selective polymerization reaction, and the results are shown in Table 2.

Table 2:

Example 14

The catalyst of example 1 was used to run the reaction at a reaction temperature of 80℃under a reaction pressure of 3.0MPa and a liquid hourly space velocity of 0.8h ^-1 for 1000h, and the results are shown in Table 3.

TABLE 3 Table 3

As shown in Table 3, the catalyst provided by the invention has good stability in propylene selective polymerization.

Example 15

The catalyst of example 14 was subjected to an in situ calcination treatment. After the catalyst of example 14 was run for 1000 hours, the introduction of the propylene feed was stopped, air was introduced at a flow rate of 100ml/min, the temperature was raised to 500℃and calcination was carried out for 6 hours, and then the catalyst was run for 500 hours under the same conditions as in example 14, with an average conversion of propylene of 75% or more. This experiment shows that the catalyst of the present invention has good regeneration performance.

Example 16

The catalyst in the example 1 is adopted to perform reaction operation under the conditions of the reaction temperature of 80 ℃, the reaction pressure of 3.0MPa and the liquid hourly space velocity of 0.8h ^-1, and the obtained olefin product is subjected to reduced pressure rectification to obtain C6, C9 and C12 olefins with the purity of more than 99 percent. The rectified C6 product is subjected to hydrogenation reaction in a high-pressure reaction kettle, and a Ni-based catalyst is adopted to obtain the distribution of C6 olefin components, and the results are shown in Table 4.

TABLE 4 Table 4

C6 component	Selectivity/%
		Methyl pentene	50.4
Hexene	49.6
		Degree of branching	0.504

As can be seen from Table 4, the catalyst provided by the present invention has a low branching degree in the olefin product obtained in the propylene selective polymerization reaction.

Claims

1. A high-efficiency stable propylene selective superposition catalyst is characterized by comprising a layered hydrotalcite main body layer plate structure comprising divalent and trivalent metal cations and interlayer anions, a metal oxide auxiliary agent and a coated core-shell structure.

2. The efficient and stable propylene selective polymerization catalyst as claimed in claim 1, wherein the divalent and trivalent metal cations are two or more of Ni, fe, co, cu, mg, al, and the molar ratio of the divalent cations to the trivalent cations is 1:4-4:1.

3. The efficient and stable propylene selective polymerization catalyst as claimed in claim 1, wherein the metal oxide auxiliary agent is one or more of ZrO ₂、TiO₂、ZnO₂、SiO₂, caO and MgO, and the content of the metal oxide auxiliary agent is 5-20% of the mass of the catalyst.

4. The method for preparing the efficient and stable propylene selective polymerization catalyst according to any one of claims 1-3, which is characterized in that the method is characterized in that a layered hydrotalcite main body laminate structure with adjustable active components is compounded with a metal oxide auxiliary agent, and then the surface modification is carried out on the layered hydrotalcite main body laminate structure to obtain the catalyst with a coated core-shell structure.

5. The method for preparing the efficient and stable propylene selective polymerization catalyst according to claim 4, which comprises the following steps:

6. The method for preparing a high-efficiency stable propylene selective polymerization catalyst according to claim 5, wherein the alkaline solution in the step ⑴ is an aqueous solution of sodium hydroxide and sodium carbonate mixed according to any volume ratio.

7. The method for preparing the efficient and stable propylene selective polymerization catalyst according to claim 5, wherein the surface modifier in the step ⑶ is C or/and N modifier and Si or/and Al modifier, the C or/and N modifier is one or more of melamine, polyethylene glycol, sucrose, glucose, mannitol and sorbitol, the addition amount of the C or/and N modifier is 0.5% -3% of the catalyst, deionized water is adopted for dissolution, and the Si or/and Al modifier is one or more of tetraethoxysilane, methyl orthosilicate, aluminum isopropoxide and aluminum sec-butoxide, the addition amount of the Si or/and Al modifier is 1% -5% of the mass of the catalyst, and alcohol is adopted for dissolution.

8. The method for preparing C6, C9 and C12 olefins by using the catalyst according to any one of claims 1-3, wherein the catalyst is contacted with propylene raw material in a fixed bed reactor for selective polymerization reaction, the contact condition comprises the temperature of 80-150 ℃, the pressure of 2.0-5.0 megapascals and the mass space velocity of the raw material liquid of 0.1-5.0 h ^-1.

9. The method for preparing C6, C9 and C12 olefins by using the catalyst according to claim 8, wherein the mass fraction of olefins in the propylene raw material is more than 99%.

10. The method for preparing C6, C9 and C12 olefins by using the catalyst according to claim 9, wherein the content of nitride in the propylene raw material is less than 1ppm, the content of sulfide is less than 5ppm, and the content of oxygen is less than 20ppm.