A catalyst, preparation method and application thereof for preparing 2-ethylhexanal by hydrotreating isooctenal

Abstract

The present invention discloses a catalyst suitable for isooctenal hydrogenation, its preparation method and application. The catalyst carrier is a mesoporous alumina composite material modified by g-carbon nitride, the main active component is one or two of Ni and Co, and the second active component is one or two of Mo and W. Among them, the mass of g-carbon nitride accounts for 5-35 wt% of the carrier, preferably 15-25 wt%. The present invention significantly increases the specific surface area of the traditional alumina catalyst, improves its pore structure, enhances the dispersion degree and stability of the active component, has more stable reaction performance, mild reaction conditions, and the selectivity of 2-ethylhexanal can reach 99%.

Description

Technical Field

[0001] The present invention relates to a mesoporous alumina catalyst for the liquid-phase hydrogenation of isooctenal to prepare 2-ethylhexanal, a preparation method thereof, and a method for preparing 2-ethylhexanal using the catalyst. Technical Background

[0002] 2-Ethylhexanal (abbreviated as isooctenal) is an important chemical raw material. It can not only be hydrogenated to prepare isooctanol for use as a plasticizer alcohol raw material, but also be oxidized to form isooctanoic acid, which is widely used in fields such as coatings and plastics.

[0003] At present, the industrial production of isooctenal is mainly from an isooctanoic acid co-production unit. Using propylene and syngas as raw materials, butyraldehyde is prepared by low-pressure hydroformylation. Butyraldehyde undergoes an aldol condensation reaction under alkaline conditions to obtain an isooctenal enrichment liquid, and this enrichment liquid is directly subjected to selective hydrogenation without separation to prepare isooctenal. Isooctenal has two types of double bonds, namely carbon-carbon double bonds and carbon-oxygen double bonds. The difficulty of this process lies in achieving high conversion and high selectivity for the hydrogenation reaction of carbon-carbon double bonds. At the same time, the polycondensed heavy components in the butyraldehyde condensation liquid are also the main reasons for the deactivation of the hydrogenation catalyst. Therefore, synthesizing an efficient catalyst is the key to realizing this technology.

[0004] Patent US4018831 uses Al2O3 as a carrier to load two active metals, nickel and palladium. Using a high-pressure fixed bed at a reaction temperature of 90-180 °C, a reaction pressure of 0.7-3.5 MPa, and an airspeed of 0.5-3 h -1 Under the conditions, the conversion rate of catalytic selective hydrogenation of isooctenal to isooctenal is 74%, and the selectivity can reach 97%, but the yield of isooctenal is relatively low.

[0005] Patent US3903171A uses silica as a carrier to support the noble metal palladium. Using a high-pressure fixed bed, at 1-25 MPa, the reaction raw materials are diluted with isooctenal as a solvent to improve the product selectivity. The disadvantage of this method is that the use of a pure silica-based carrier results in low reaction activity and low catalyst throughput, leading to low product yield.

[0006] Patent CN111054437 uses a polymer matrix crosslinked with a polybasic acid to support the noble metal palladium. Using a high-pressure reactor at a reaction temperature of 50-130 °C and a reaction pressure of 1-5 MPa, the conversion rate of catalytic selective hydrogenation of isooctenal to isooctenal can reach 99%, and the selectivity can reach 99%. However, the crosslinking degree of the catalyst matrix has a great influence on the stability and activity of the carrier. It is difficult to control the crosslinking degree during the scale-up production process, and it is difficult to maintain stable reaction activity.

[0007] The literature reports a method for the selective hydrogenation of isooctenal using a Pd / γ-Al2O3 catalyst. At a reaction temperature of 85-95 °C, a reaction pressure of 2.45 MPa, and an airspeed of 0.15-0.3 h-1 Under this condition, the yield of isooctanal is 98%, and the selectivity can reach 99%. The overall yield of this method is relatively high, but the catalyst throughput is low and the cost is high. At the same time, γ-Al2O3 has strong acidity, and the high tar content in the isooctenal raw material easily leads to catalyst carbon deposition and deactivation.

[0008] In summary, it is necessary to find a catalyst with high conversion rate, stable activity, and suitable for industrial production of isooctenal raw materials with high tar content to solve various deficiencies in the existing technology. Summary of the Invention

[0009] The object of the present invention is to provide a catalyst loaded with Group VIB metals on a g-C3N4 modified mesoporous alumina composite material, a preparation method thereof, and an application in the selective hydrogenation of isooctenal, aiming at the deficiencies of the existing technology. The g-C3N4 modified mesoporous alumina composite material synthesized with SBA-15 as a template agent in the present invention is simple to prepare. The catalyst support contains a large number of N-containing groups, which can effectively stabilize metal nanoparticles. At the same time, using SBA-15 as a template agent has a larger specific surface area, a more regular pore structure, and a suitable acid-base distribution and dual active centers, which can improve the selectivity of isooctanal. At the same time, it has strong hydrogenation cracking properties for the butyraldehyde trimer and tetramer components in the hydrogenation raw material to increase the yield of isooctanal.

[0010] To achieve the above invention purpose, the technical scheme adopted by the present invention is as follows:

[0011] A catalyst suitable for the selective hydrogenation of isooctenal, wherein the catalyst support is a g-carbon nitride modified mesoporous alumina composite material, the main active component is one or two of Ni and Co, and the second active component is one or two of Mo and W, wherein the mass of g-carbon nitride accounts for 5-35 wt% of the support, preferably 15-25 wt%.

[0012] The synthesis of the g-carbon nitride modified mesoporous alumina composite material first uses SBA-15 as a template to obtain α-Al2O3 / SBA-15, then adds a nitrogen-containing precursor and calcines to obtain a g-C3N4 / α-Al2O3 / SBA-15 composite material, and finally uses hydrofluoric acid for acidolysis to obtain a g-C3N4 / α-Al2O3 composite material with a regular pore structure.

[0013] Preferably, according to the catalyst of the present invention, the main active metal is Ni, and its content is 0.2-0.8%, and the second active metal is Mo, and the content is preferably 0.2-0.4%.

[0014] To achieve the above invention, the present invention provides a method for preparing a g-C3N4 modified mesoporous alumina hydrogenation catalyst based on SBA-15 as a template, including the following steps:

[0015] (1) Using P123 as the template agent (with the molecular formula EO20PO70EO20 and a molecular weight of 5800), and pseudo-boehmite and tetraethyl orthosilicate as raw materials, α-Al2O3 / SBA-15 molecular sieve is prepared through crystallization, filtration, and calcination.

[0016] (2) Dissolve the N-containing precursor in methanol and then drop it onto the above molecular sieve, dry at 40 - 50 °C for 1 - 2 h, and calcine in a nitrogen atmosphere at 400 - 500 °C to obtain the g-C3N4 / α-Al2O3 / SBA-15 composite material.

[0017] (3) Pickle the material in step (2) with HF, then wash, filter, and dry it with deionized water to obtain a mesoporous alumina composite material modified with g-carbon nitride using SBA-15 as the template.

[0018] (4) Drop the aqueous solutions of soluble nickel salts and molybdenum salts onto the g-carbon nitride modified mesoporous alumina composite material in step (3), stir, dry, and calcine in a nitrogen atmosphere to obtain the catalyst; preferably, the calcination temperature is 400 - 600 °C, and the calcination time is 3 - 8 h.

[0019] In step (1) of the present invention, the mass ratio of alumina to SBA-15 is (1 - 10):1, and the preferred mass ratio is (1 - 5):1.

[0020] In step (1) of the present invention, the crystallization temperature is 70 - 150 °C, preferably 80 - 100 °C, the crystallization time is 1 - 48 h, and the preferred time is 12 - 24 h.

[0021] In step (1) of the present invention, the calcination temperature is 800 - 1500 °C, calcine for 1 - 5 h, preferably 1200 °C for 3 h, and the obtained alumina crystal form is α-Al2O3.

[0022] In step (2) of the present invention, the N-containing precursor is one or more of urea, melamine, and N,N-dimethylformamide. Preferably, urea and melamine are mixed, and the preferred molar ratio is 1 - 3:1.

[0023] In step (3) of the present invention, the drying temperature is 70 - 130 °C, the time is 1 - 5 h, preferably the drying temperature is 80 - 110 °C, and the time is 3 - 4 h.

[0024] In step (4) of the present invention, the molybdenum salt is one or two of ammonium molybdate, molybdenum nitrate, and molybdenum oxalate. Preferably, it is ammonium molybdate, and the nickel salt is one or two of nickel nitrate, nickel sulfate, and nickel chloride. Preferably, it is nickel nitrate.

[0025] According to one aspect of the present invention, a method for preparing 2-ethylhexanal is provided. Under the action of the above catalyst, isooctenal and hydrogen are selectively hydrogenated in a fixed-bed reactor at a temperature of 60-110 °C, a pressure of 0.5-5 MPa, a space velocity of 1-10 h -1 -1, and a volume ratio of hydrogen to isooctenal of 50:1 to produce 2-ethylhexanal.

[0026] The beneficial effects of the present invention are as follows: The g-C3N4 modified material contains a large number of N-containing groups, which can effectively stabilize metal nanoparticles and the catalyst activity is stable. At the same time, using SBA-15 as a template agent has a larger specific surface area, a more regular pore structure, and a suitable acid-base distribution and dual-metal active centers, which can increase the selectivity of isooctanal to more than 99%. At the same time, it has strong hydrogenation cracking properties for butyraldehyde trimer and tetramer in the hydrogenation raw material to increase the yield of isooctanal. Specific Embodiments

[0027] The following specific embodiments are used to further illustrate the present invention. These embodiments are only used to illustrate the present invention, but the implementation manners of the invention are not limited thereto.

[0028] Raw materials and sources: The hydrogenation raw material isooctenal is the condensation liquid prepared by the aldol condensation of butyraldehyde catalyzed by 2% NaOH. It is directly hydrogenated without removing the polymers therein. The process of preparing 2-ethyl-2-hexenal from n-butyraldehyde is well-known in the art. The isooctenal raw material used contains 0.9 wt% of n-butyraldehyde, 96.7 wt% of isooctenal, and 2.4 wt% of butyraldehyde polycondensed heavy components. Other raw materials are all commercially available.

[0029] Example 1

[0030] Weigh 4 g of template agent P123 and put it into a 500 mL beaker, then pour in 160 mL of dilute hydrochloric acid (1 mol / L), and stir to dissolve at 4 °C; gradually add 10.4165 g of tetraethyl orthosilicate dropwise, and add 4.2917 g of pseudoboehmite, then continue to stir and react for 6 h; then crystallize at 70 °C for 1 h, filter, wash, dry, and calcine at 800 °C for 5 h to obtain α-Al2O3 / SBA-15 molecular sieve.

[0031] Dissolve 0.3097 urea in methanol and drop it into the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 400 °C for 3 h to obtain g-C3N4 / α-Al2O3 / SBA-15 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 70 °C for 5 h to obtain a mesoporous alumina composite material modified with g-carbon nitride using SBA-15 as a template

[0032] Weigh 0.0129 g of ammonium molybdate and 0.0166 g of nickel sulfate, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine in a nitrogen atmosphere at 400 °C for 8 h to obtain hydrogenation catalyst A.

[0033] Example 2

[0034] Weigh 4 g of template agent P123 and put it into a 500 mL beaker, then pour in 160 mL of dilute hydrochloric acid (1 mol / L), stir and dissolve at 4 °C; slowly add 10.4165 g of tetraethyl orthosilicate dropwise, and add 21.4586 g of pseudo-boehmite, then continue to stir and react for 6 h; then crystallize at 90 °C for 24 h, filter, wash, dry, and calcine at 1200 °C for 3 h to obtain α-Al2O3 / SBA-15 molecular sieve.

[0035] Dissolve 11.0879 g of melamine in methanol and drop it into the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 500 °C for 8 h to obtain g-C3N4 / α-Al2O3 / SBA-15 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 80 °C for 2 h to obtain a mesoporous alumina composite material modified by g-carbon nitride with SBA-15 as the template.

[0036] Weigh 0.2037 g of molybdenum nitrate and 0.2030 g of nickel chloride, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine in a nitrogen atmosphere at 550 °C for 7 h to obtain hydrogenation catalyst B.

[0037] Example 3

[0038] Weigh 4 g of template agent P123 and put it into a 500 mL beaker, then pour in 160 mL of dilute hydrochloric acid (1 mol / L), stir and dissolve at 4 °C; slowly add 10.4165 g of tetraethyl orthosilicate dropwise, and add 42.9171 g of pseudo-boehmite, then continue to stir and react for 6 h; then crystallize at 120 °C for 48 h, filter, wash, dry, and calcine at 1500 °C for 1 h to obtain α-Al2O3 / SBA-15 molecular sieve.

[0039] Dissolve 10.2959 g of N,N-dimethylformamide in methanol and drop it into the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 450 °C for 6 h to obtain g-C3N4 / α-Al2O3 / SBA-15 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 110 °C for 3 h to obtain a mesoporous alumina composite material modified by g-carbon nitride with SBA-15 as the template.

[0040] Weigh 0.3067 g of ammonium molybdate and 0.4288 g of nickel nitrate, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine at 500 °C for 5 h under a nitrogen atmosphere to obtain hydrogenation catalyst C.

[0041] Example 4

[0042] Weigh 4 g of template agent P123 and put it into a 500 mL beaker, then pour in 160 mL of dilute hydrochloric acid (1 mol / L), stir and dissolve at 4 °C; gradually add 10.4165 g of tetraethyl orthosilicate dropwise, and add 30.042 g of pseudoboehmite, then continue to stir and react for 6 h; then crystallize at 150 °C for 36 h, filter, wash, dry, and calcine at 1200 °C for 3 h to obtain α-Al2O3 / SBA-15 molecular sieve.

[0043] Dissolve 5.4189 g of urea and 11.3792 g of melamine in methanol and dropwise add the solution to the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 400 °C for 8 h to obtain g-C3N4 / α-Al2O3 / SBA-15 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 130 °C for 1 h to obtain a mesoporous alumina composite material modified by g-carbon nitride with SBA-15 as the template.

[0044] Weigh 0.2471 g of molybdenum nitrate and 0.4645 g of nickel sulfate, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine at 500 °C for 5 h under a nitrogen atmosphere to obtain hydrogenation catalyst D.

[0045] Example 5

[0046] Weigh 4 g of template agent P123 and put it into a 500 mL beaker, then pour in 160 mL of dilute hydrochloric acid (1 mol / L), stir and dissolve at 4 °C; gradually add 10.4165 g of tetraethyl orthosilicate dropwise, and add 12.8751 g of pseudoboehmite, then continue to stir and react for 6 h; then crystallize at 100 °C for 12 h, filter, wash, dry, and calcine at 1200 °C for 3 h to obtain α-Al2O3 / SBA-15 molecular sieve.

[0047] Dissolve 10.8376 g of urea and 7.5862 g of melamine in methanol and dropwise add the solution to the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 500 °C for 5 h to obtain g-C3N4 / α-Al2O3 / SBA-15 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 100 °C for 4 h to obtain a mesoporous alumina composite material modified by g-carbon nitride with SBA-15 as the template.

[0048] Weigh 0.0981 g of ammonium molybdate and 0.183 g of nickel nitrate, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine at 600 °C for 4 h under a nitrogen atmosphere to obtain the supported hydrogenation catalyst E.

[0049] Comparative Example 1

[0050] Weigh 3.0042 g of SBA-16 molecular sieve and 12.8751 g of pseudo-boehmite into a 500 mL beaker, then pour 160 mL of dilute hydrochloric acid (1 mol / L), stir at 40 °C for 6 h; after filtration, washing, and drying, calcine at 1200 °C for 3 h to obtain α-Al2O3 / SBA-16 molecular sieve.

[0051] Dissolve 10.8376 g of urea and 7.5862 g of melamine in methanol, drop the solution onto the above molecular sieve, then dry at 40 °C for 1 h, and then calcine at 500 °C for 5 h to obtain the g-C3N4 / α-Al2O3 / SBA-16 composite material. Then use 10% HF for pickling, wash with deionized water, filter, and dry at 100 °C for 4 h to obtain the mesoporous alumina composite material modified by g-carbon nitride using SBA-16 as a template

[0052] Weigh 0.0981 g of ammonium molybdate and 0.183 g of nickel nitrate, dissolve them in water, impregnate the above carrier with the solution, dry at 50 °C for 2 h, and calcine at 600 °C for 4 h under a nitrogen atmosphere to obtain the comparative hydrogenation catalyst F

[0053] Comparative Example 2

[0054] Weigh 9.0126 g of alumina, weigh 0.0981 g of ammonium molybdate and 0.183 g of nickel nitrate, dissolve them in water, impregnate the alumina carrier with the solution, dry at 50 °C for 2 h, and calcine at 600 °C for 4 h under a nitrogen atmosphere to obtain the unmodified alumina comparative hydrogenation catalyst G

[0055] Application Example

[0056] Preparation of isooctanal by hydrogenation of the catalyst in Example 1

[0057] Perform a continuous experiment using a high-pressure fixed bed, fill 100 g of catalyst A, and react isooctenal with hydrogen at 60 °C, 0.5 MPa, and a space velocity of 1 h -1 The reaction product is quantitatively detected by gas chromatography. The isooctenal raw material used is the above raw material.

[0058] Preparation of isooctanal by hydrogenation of the catalyst in Example 2

[0059] Perform a continuous experiment using a high-pressure fixed bed, fill 100 g of catalyst B, and react isooctenal with hydrogen at 110 °C, 5 MPa, and a space velocity of 7 h-1. The reaction product is quantitatively detected by gas chromatography. The isooctenal raw material used is the same raw material

[0060] Example 3 Preparation of isooctanal by catalytic hydrogenation

[0061] A continuous experiment was carried out in a high-pressure fixed bed. 100 g of catalyst C was filled, and isooctenal and hydrogen were reacted at 80 °C, 2.5 MPa, and a space velocity of 3 h-1. The reaction products were quantitatively detected by gas chromatography. The isooctenal raw material used was the same kind of raw material

[0062] Example 4 Preparation of isooctanal by catalytic hydrogenation

[0063] A continuous experiment was carried out in a high-pressure fixed bed. 100 g of catalyst D was filled, and isooctenal and hydrogen were reacted at 70 °C, 3 MPa, and a space velocity of 10 h-1. The reaction products were quantitatively detected by gas chromatography. The isooctenal raw material used was the same kind of raw material

[0064] Example 5 Preparation of isooctanal by catalytic hydrogenation

[0065] A continuous experiment was carried out in a high-pressure fixed bed. 100 g of catalyst E was filled, and isooctenal and hydrogen were reacted at 90 °C, 2 MPa, and a space velocity of 5 h-1. The reaction products were quantitatively detected by gas chromatography. The isooctenal raw material used was the same kind of raw material

[0066] Comparative Example 1 Preparation of isooctanal by catalytic hydrogenation

[0067] A continuous experiment was carried out in a high-pressure fixed bed. 100 g of comparative catalyst F was filled, and isooctenal and hydrogen were reacted at 90 °C, 2 MPa, and a space velocity of 5 h-1. The reaction products were quantitatively detected by gas chromatography.

[0068] The isooctenal raw material used was the same kind of raw material

[0069] Comparative Example 2 Preparation of isooctanal by catalytic hydrogenation

[0070] A continuous experiment was carried out in a high-pressure fixed bed. 100 g of comparative catalyst G was filled, and isooctenal and hydrogen were reacted at 90 °C, 2 MPa, and a space velocity of 5 h-1. The reaction products were quantitatively detected by gas chromatography.

[0071] The isooctenal raw material used was the same kind of raw material

[0072] The hydrogenation results of all examples are shown in the following table

[0073] Table 1 Composition and reaction conditions of the reaction solutions obtained in Examples 1-5 and Comparative Examples 1-2

[0074]

Claims

1. A catalyst suitable for selective hydrogenation of isooctenal, wherein the catalyst support is a mesoporous alumina composite modified by g-carbon nitride, the main active component is Ni, and the second active component is Mo, and the mass of g-carbon nitride accounts for 5-35 wt% of the support; the preparation method of the catalyst comprises the following steps: (1) Using P123 as a template agent, pseudoboehmite and tetraethyl orthosilicate as raw materials, α-Al2O3 / SBA-15 molecular sieve is prepared through crystallization, filtration, and calcination; (2) Dissolving the N-containing precursor with methanol and then dropping it onto the above molecular sieve, drying at 40-50 °C for 1-2 h, and calcining in a nitrogen atmosphere at 400-500 °C to obtain g-C3N4 / α-Al2O3 / SBA-15 composite; (3) Pickling the material in step (2) with HF, and then washing, filtering, and drying with deionized water to obtain a mesoporous alumina composite modified by g-carbon nitride using SBA-15 as a template; (4) Dropping an aqueous solution of soluble nickel salt and molybdenum salt onto the g-carbon nitride modified mesoporous alumina composite in step (3), stirring, drying, and calcining in a nitrogen atmosphere to obtain the catalyst; the calcination temperature is 400-600 °C, and the calcination time is 3-8 h; the crystallization temperature in step (1) is 70-150 °C, the crystallization time is 1-48 h, the calcination temperature is 800-1500 °C, and the calcination is 1-5 h.

2. The selective hydrogenation catalyst for isooctenal as claimed in claim 1, wherein The main active metal is Ni, and its content is 0.2-0.8%, and the second active metal is Mo, and its content is 0.2-0.4%.

3. The selective hydrogenation catalyst for isooctenal as claimed in claim 1, characterized in that, In step (1), the mass ratio of alumina to SBA-15 is (1-10):

1.

4. The selective hydrogenation catalyst for isooctenal as described in claim 1, characterized in that, In step (1), the mass ratio of alumina to SBA-15 is (1-5):

1.

5. The selective hydrogenation catalyst for isooctenal as described in any one of claims 1-4, characterized in that, The crystallization temperature in step (1) is 80-100 °C, and the crystallization time is 12-24 h.

6. The selective hydrogenation catalyst for isooctenal according to any one of claims 1-4, characterized in that, The N-containing precursor in step (2) is one or more of urea, melamine, and N,N-dimethylformamide.

7. The selective hydrogenation catalyst for isooctenal as described in claim 6, characterized in that, The N-containing precursor in step (2) is a mixture of urea and melamine, and the molar ratio is 1-3:

1.

8. The selective hydrogenation catalyst for isooctenal as claimed in any one of claims 1-4, characterized in that, The drying temperature in step (3) is 70-130 °C, and the time is 1-5 h.

9. The selective hydrogenation catalyst for isooctenal as claimed in claim 8, characterized in that, The drying temperature in step (3) is 80-110 °C, and the time is 3-4 h.

10. The selective hydrogenation catalyst for isooctenal as described in any one of claims 1-4, characterized in that, The molybdenum salt in step (4) is one or two of ammonium molybdate, molybdenum nitrate, and molybdenum oxalate, and the nickel salt is one or two of nickel nitrate, nickel sulfate, and nickel chloride.

11. A preparation method of 2-ethylhexanal, the method comprising subjecting isooctenal and hydrogen to selective hydrogenation in a fixed-bed reactor at a temperature of 60-110 °C, a pressure of 0.5-5 MPa, a space velocity of 1-10 h -1 -1, and a volume ratio of hydrogen to isooctenal of 50:1 under the action of a catalyst suitable for selective hydrogenation of isooctenal as described in any one of claims 1-10 to produce 2-ethylhexanal.

Images