Catalyst for catalytic continuous decarbonylation hydrogenation reaction, and preparation method and application thereof

Abstract

The application belongs to the field of chemical catalysis, and particularly relates to a catalyst for catalyzing continuous decarbonylation hydrogenation reaction and a preparation method and application thereof. The catalyst is Ni-M / SNTs@MgO, which comprises active metal Ni, auxiliary metal M, carrier SNTs and surface-coated MgO, the auxiliary metal M is one or more of Cu, Co, Zn, Zr and Mo, and the carrier SNTs is a silicon dioxide nanotube; and the preparation method comprises surface-coating MgO on Ni-M / SNTs by using an atomic layer deposition method. The catalyst has low cost, excellent catalytic performance when used for preparing tetrahydrofuran by continuous decarbonylation hydrogenation of furfural, furfural conversion rate is greater than 99%, and tetrahydrofuran selectivity is greater than 90%. The catalyst has no obvious deactivation sign when continuously operated for more than 3000 hours, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical catalysis, and particularly relates to a catalyst for catalyzing continuous decarbonylation hydrogenation reaction and a preparation method and application thereof. BACKGROUND

[0002] Tetrahydrofuran (THF) is an important raw material for synthesizing polyurethane elastomer, polybutylene succinate (PBS), polybutylene terephthalate (PBT), spandex fiber, special rubber and paint, and is also an important organic reaction solvent and raw material. The market volume of THF is huge, and the global sales reached 4.53 billion US dollars in 2023, and is expected to have an annual growth rate of 6.7% from 2024 to 2030.

[0003] At present, the mainstream production process of THF in industry is Reppe method, which uses calcium carbide acetylene as raw material, formaldehyde and acetylene to react to generate 1,4-butynediol, and then 1,4-butynediol is subjected to hydrogenation and acid catalytic dehydration to obtain THF. The market demand for THF is huge and shows a growing trend. Due to the unsustainability of fossil raw materials, and the long reaction steps of Reppe method, a large amount of CO2 is discharged in the production of THF. Unlike the traditional petrochemical-based production process of tetrahydrofuran, the bio-based production route is to obtain furfural by hydrolysis of corn cobs, straw and the like, to obtain furan by decarbonylation of furfural, and to obtain tetrahydrofuran by hydrogenation of furan. The carbon emission of the whole process is greatly reduced, and the influence of trace amounts of aromatic hydrocarbon impurities remaining in tetrahydrofuran is reduced, which is more suitable for the pharmaceutical industry.

[0004] The preparation of tetrahydrofuran by furfural method mainly includes two steps. In the first step, furfural is subjected to decarbonylation reaction in the presence of a catalyst in a fixed bed reactor to prepare furan, generally using Pd, Pt and other noble metal catalysts, and the furan yield can reach more than 85%. The second step of hydrogenation reaction is carried out in a high-pressure reaction kettle, and the THF yield is about 90%. Xue Li et al. (Natural Gas Chemical Industry, 2002, 27:9-12.) prepared 0.6%Pt-1.2%M / Al2O3-TiO2 (M is an additive) for furfural gas phase decarbonylation to prepare furan, at a reaction space velocity of 0.3~0.4 h -1 , a reaction temperature of 290~325℃, a furfural conversion rate of 100%, and a reaction time of 500 h, the furan yield reached more than 85%. Patent CN1308986A discloses a high-efficiency noble metal catalyst for furfural gas phase decarbonylation to produce furan, which uses Al2O3-TiO2 composite oxide as the carrier, the Pt loading amount is 0.4~0.7%, and K2O and the like are used as additives with a content of 0.5~2.0%. The catalyst is used at normal pressure, at a temperature of 280℃, a furfural volume space velocity of 0.9 h -1, the molar ratio of furfural to hydrogen was 0.5-2.0, the conversion rate of furfural was 80-97%, and the selectivity of furan was 85-92%. Wang Chengxue et al. (Fine Chemicals, 2010, 35: 75-78.) used Pd / C as a catalyst to generate tetrahydrofuran by hydrogenation of furan in a tank reactor. The conversion rate of furan was 92%, and the yield of tetrahydrofuran was 90.2%. At present, the two-step process of furfural decarbonylation to furan and further hydrogenation of furan to prepare tetrahydrofuran has a relatively complicated process route, the total yield of tetrahydrofuran is relatively low, and additional equipment investment and energy consumption for separation of intermediate products are increased. The development of one-step process for preparing tetrahydrofuran from furfural has good application prospect.

[0005] Compared with noble metal-based catalysts, non-noble metal catalysts such as Ni, Co, and Cu have advantages in cost. Wang et al. (Chem. Eng., 2019, 36:1235-1242.) used mesoporous Al2O3 supported Ni metal catalyst for decarbonylation of furfural to furan, with methanol as hydrogen donor, and obtained 85% furan yield at 280℃. Zhang et al. (Chem. Eng. J., 2023, 466:143237.) prepared a catalyst Co-MoC / CN with Co-MoC heterostructure and applied it to the reaction of decarbonylation of furfural to furan. At 180℃, under the condition of H2 pressure of 2 MPa, the furan yield was 72.21%. Carmen et al. (ACS Sustainable Chemistry & Engineering, 2019, 7(8):7676-7685.) prepared Ni-MgO solid solution catalyst by coprecipitation-calcination-reduction method, and obtained 96% furfural conversion rate and 88% furan yield at 190℃. However, the catalyst was deactivated after 24 h of reaction. The use of non-noble metal catalysts has problems such as lower furan yield and easy deactivation of catalyst.

[0006] Main reaction:

[0007]

[0008] Main side reaction:

[0009]

[0010] The previous invention patent application CN202410473562.1 of the applicant provides a method for preparing tetrahydrofuran by one-step continuous reaction of furfural, which comprises the following reaction steps: furfural is delivered to a vaporizer by a feeding pump for vaporization, hydrogen and furfural are reacted under the action of a catalyst, furfural undergoes decarbonylation to form furan, and the furan is further hydrogenated on the same catalyst to form tetrahydrofuran; the catalyst is a Pd-M1-M2 / γAl2O3 catalyst. The continuous process adopted by the invention is simple, the conversion rate of furfural is more than 99%, the yield of tetrahydrofuran can reach 75%, the yield of 2-methyltetrahydrofuran can reach 20%, the total yield of the two is 95%, and the single-pass life of the catalyst is more than 2000h.

[0011] In addition, Chinese patent application CN202410421839.6 discloses a method for synthesizing tetrahydrofuran from furfural in one step and a preparation method of a catalyst therefor. The catalyst is a bimetallic catalyst, and the bimetallic catalyst comprises M1 and M2, wherein M1 is Pd, and M2 is selected from one of Pt, Rh, Ru, Ni, Cu, Co, Mn and Ce; the catalyst comprises an active component and a carrier, wherein the bimetallic catalyst is the active component, and the carrier is selected from at least one of activated carbon, silicon dioxide, aluminum oxide, magnesium oxide, S-1 molecular sieve, ZSM-5 molecular sieve, Beta molecular sieve, MOR molecular sieve and Y molecular sieve; the loading amount of M1 is 0.5-3.5% based on the total weight of the catalyst, and the loading amount of M2 is 0.5-3.5% based on the total weight of the catalyst. The catalyst of the invention can be used in the reaction of hydrogenating furfural to form tetrahydrofuran, and can improve the conversion rate of furfural and the selectivity of tetrahydrofuran.

[0012] However, the catalysts used in the above-mentioned method for synthesizing tetrahydrofuran from furfural in one step are all Pd-containing noble metal catalysts, and non-noble metal catalysts cannot be used. Therefore, there is a need in the art for a new solution to solve the problems of low furan yield and easy deactivation of the catalyst in the non-noble metal catalysts used in the prior art for synthesizing tetrahydrofuran from furfural in one step. SUMMARY

[0013] Based on the above-mentioned problems, the present application provides a non-noble metal catalyst with high activity, high selectivity and high stability for catalyzing the continuous decarbonylation and hydrogenation of furfural to prepare tetrahydrofuran.

[0014] The present application first provides a catalyst for catalyzing the continuous decarbonylation and hydrogenation reaction, which is Ni-M / SNTs@MgO, and comprises active metal Ni, auxiliary metal M, carrier SNTs and surface-coated MgO, the auxiliary metal M is one or more of Cu, Co, Zn, Zr and Mo, and the carrier SNTs is a silicon dioxide nanotube; the preparation method of the catalyst comprises surface-coating MgO on Ni-M / SNTs by using an atomic layer deposition method.

[0015] In a specific embodiment, the mass fraction of active metal Ni in the catalyst is 20-35wt%, the mass fraction of the auxiliary metal M is 0.1-5wt%, the number of MgO coating layers is 1 or more, and the rest is the carrier; and TEA (triethanolamine) is used in the preparation of the carrier SNTs.

[0016] In a specific embodiment, the mass fraction of active metal Ni in the catalyst is 27-29.5wt%; the mass fraction of the auxiliary metal M is 0.5-3wt%; and the number of MgO coating layers is 1-7.

[0017] In the present application, preferably, the mass fraction of active metal Ni in the catalyst is 29-29.5wt%; the mass fraction of the auxiliary metal M is 0.5-1wt%; and the number of MgO coating layers is 1-3.

[0018] The present application also provides a preparation method of the catalyst, wherein the preparation method of the carrier SNTs adopts a two-phase layering method and specifically comprises: mixing cetyltrimethylammonium chloride (CTAC), TEA, carbon nanotubes (CNTs), deionized water, tetraethyl orthosilicate (TEOS) and cyclohexane, stirring at a certain temperature, and then preparing SNTs through centrifugation, drying and calcination.

[0019] In a specific embodiment, the mass ratio of CTAC, TEA, CNTs, deionized water, TEOS, cyclohexane is 2-4:1-2:1-2:100-200:30-60:2-4; the stirring temperature in the carrier preparation process is 40-60℃, the stirring rate is 800-1000r / min, and the stirring time is 18-24h; the centrifugation rate is 8000-16000r / min, the centrifugation time is 5-10min, and the white solid powder is obtained after centrifugation; the drying temperature is 80-120℃, and the drying time is 2-6h; the calcination is carried out under N2 or Ar atmosphere at a flow rate of 30-50mL / min, a heating rate of 2-4℃ / min, a calcination temperature of 500-600℃, and a calcination time of 3-5h.

[0020] In a specific embodiment, the preparation method of the Ni-M / SNTs@MgO catalyst precursor comprises: mixing a certain amount of SNTs, nitrate of Ni and metal M, and methanol, and refluxing at a certain temperature; after centrifugation, water washing and drying, the solid powder obtained by the impregnation method is placed in an ALD (atomic layer deposition) reaction cavity, a solution of water and bis(ethylcyclopentadienyl)magnesium (Mg(C5H4C2H5)2) is subjected to pulse circulation deposition, i.e., the surface of Ni-M / SNTs is coated with a MgO layer, thereby obtaining the Ni-M / SNTs@MgO catalyst precursor.

[0021] In a specific embodiment, the mass ratio of SNTs, nitrate of metal Ni, nitrate of metal M, methanol in the preparation process of the catalyst precursor is 2.16-4.32:3.3-7.05:0.046-0.29:50-100; the reflux temperature is 60-80℃, the reflux time is 2-6h; the ALD reaction cavity temperature is 180-220℃, the pulse time is 1-2s, and the deposition times is 1-7.

[0022] In a specific embodiment, the nitrate of metal Ni is Ni(NO3)2·6H2O, and the nitrate of metal M is one or more of Cu(NO3)2·3H2O, Co(NO3)2·6H2O, Zn(NO3)2·6H2O, Zr(NO3)4·5H2O and Mo(NO3)4·5H2O.

[0023] In a specific embodiment, the catalyst precursor is calcined and reduced to obtain a Ni-M / SNTs@MgO catalyst; the calcination is carried out under N2 or Ar atmosphere, the flow rate is 30-50mL / min, the heating rate is 2-4℃ / min, the calcination temperature is 450-550℃, and the calcination time is 4-6h; the reduction is carried out using 5%H2 / Ar mixed gas, the flow rate is 30-50mL / min, the heating rate is 2-4℃ / min, the reduction temperature is 200-400℃, and the reduction time is 2-4h.

[0024] The application also provides the use of the catalyst prepared by the above method in the reaction of catalyzing the continuous decarbonylation and hydrogenation of furfural to prepare tetrahydrofuran; the reaction is carried out in a fixed bed reactor, and includes that the Ni-M / SNTs@MgO is pressed into a tablet, 20-40 mesh particles are screened as the catalyst, and the catalyst is loaded in the constant temperature zone of the reaction tube; the reaction temperature is 200-300℃; the mass space velocity of furfural is 0.2-0.5h-1, the molar ratio of hydrogen to furfural is 1-50.0, and the reaction pressure is normal pressure. -1

[0025] In the application, in the reaction of catalyzing the continuous decarbonylation and hydrogenation of furfural to prepare tetrahydrofuran, the reaction temperature is 240-280℃, and the molar ratio of hydrogen to furfural is 20-50, preferably 30-40.

[0026] The catalyst Ni-M / SNTs@MgO has a sandwiched layer tubular hollow structure, and the surface is coated with a MgO layer.

[0027] ​In the present application, when calculating the theoretical load of nickel (i.e. the mass fraction of metal Ni) and the theoretical load of metal M (i.e. the mass fraction of metal M), only the mass of the carrier, metal nickel and metal M is counted, and the mass of the finally coated MgO layer is not counted.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] 1. Compared with the traditional petrochemical route Reppe method, the present application uses furfural as raw material, and a step continuous decarbonylation hydrogenation process is used to prepare bio-based tetrahydrofuran, which reduces CO2 emissions and improves the quality of tetrahydrofuran.

[0030] 2. The catalyst Ni-M / SNTs@MgO provided by the present application has a special structure, which not only makes the reactants have good contact with the metal active sites, but also the MgO coating layer is beneficial to prevent the metal active components Ni and M from being deactivated due to sintering and coking, and the catalyst has good stability.

[0031] 3. The Ni-M / SNTs@MgO catalyst provided by the present application has a highly adjustable surface acid-base degree, and has high selectivity, yield and stability in the preparation of bio-based tetrahydrofuran from furfural decarbonylation hydrogenation.

[0032] 4. The catalyst used in the present application is a non-noble metal-based catalyst, which has an advantage in cost compared with the Pd-based catalyst in the prior art.

[0033] 5. The present application includes a bimetallic active structure, and the introduction of the second metal M is beneficial to highlight the interaction and interface effect between the two metals, improve the electronic structure of the catalyst, and improve the performance of the catalyst; and the bimetallic component is easy to form an alloy, which further improves the dispersion of the metal in the catalyst and inhibits the agglomeration and sintering of the catalyst. The catalyst of the present application has a single substance coated on the outer surface, and the alkalinity of the MgO coating is higher in controllability, which is beneficial to the reaction towards the generation of tetrahydrofuran, and inhibits the generation of by-products.

[0034] 6. The catalyst described in the present application has excellent stability, and the catalytic reaction time is as long as 3000h without deactivation.

[0035] 7. The preparation method of the present application is first based on carbon nanotubes (CNTs), and a two-phase layered method is used to prepare a carrier silica nanotube (SNTs), and then an impregnation method is used to load active metals Ni and M, and an ALD method is used to coat an MgO layer to form a sandwiched layer pipe-shaped hollow structure catalyst; when it is used for catalyzing one-step continuous decarbonylation hydrogenation to prepare tetrahydrofuran, it has higher selectivity of the target product tetrahydrofuran and catalyst life than the prior art, and has good industrial application prospect.

[0036] 8. In the application of the present application, the catalyst is used to catalyze the preparation of tetrahydrofuran by one-step continuous decarbonylation hydrogenation. The reaction does not need to be carried out under high pressure. The atmospheric reaction condition adopted by the present application is conducive to reducing cost and energy consumption, and reducing the risk coefficient of operation. DETAILED DESCRIPTION

[0037] The embodiments listed in the present application will be described in detail below through specific examples, but the protection scope of the present application is not limited to the following examples.

[0038] Example 1

[0039] 1) Preparation of the carrier: 2 g of CTAC, 1 g of TEA, 1 g of carbon nanotubes, 100 mL of deionized water, 30 g of TEOS, and 2 g of cyclohexane were mixed in a 250 mL round-bottom flask and stirred at 60°C at a rate of 1000 r / min for 24 h.

[0040] 2) Centrifugation: The material synthesized in step 1) was centrifuged at a rate of 16000 r / min for 10 min to obtain a white solid powder.

[0041] 3) Drying: The white powder obtained after centrifugation in step 2) was washed with deionized water until neutral and dried at 120°C for 4 h.

[0042] 4) First calcination to obtain the carrier SNTs: The dried product in step 3) was placed in a N2 atmosphere at a flow rate of 30 mL / min and heated to 550°C at a rate of 2°C / min, and kept for 4 h to obtain the calcined product.

[0043] 5) Preparation of the catalyst precursor: 2.16 g of SNTs, 3.58 g of Ni(NO3)2·6H2O, 0.046 g of Cu(NO3)2·3H2O, and 50 g of methanol were refluxed at 80°C for 6 h, then centrifuged at a speed of 16000 r / min for 10 min, washed with deionized water until neutral, and dried at 120°C for 4 h. The dried material was placed in the center of the ALD reaction chamber, the temperature was 200°C, the pulse time of water vapor and bis(ethylcyclopentadienyl)magnesium was 2 s, and each ALD cycle deposition was treated with "expo" mode for porous materials, and 3 cycles of deposition were coated with 3 layers of MgO.

[0044] 6) Second calcination: The catalyst precursor coated with MgO layers in step 5) was placed in a N2 atmosphere at a flow rate of 30 mL / min and heated to 500°C at a rate of 2°C / min, and kept for 6 h to obtain the calcined product.

[0045] 7) Reduction: The calcined catalyst from step 6) was reduced under 30 mL / min of 5% H2 / Ar, ramping to 400 °C at a rate of 2 °C / min and holding for 4 h to obtain 29.5Ni-0.5Cu / SNTs@3MgO. The theoretical loading of Ni metal was 29.5 wt% and the theoretical loading of Cu was 0.5 wt% based on the total mass of the catalyst, with 3 layers of MgO coating.

[0046] Example 2

[0047] The amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g and the amount of Cu(NO3)2·3H2O was 0.1 g, and the rest was the same as in Example 1 to obtain 29Ni-1Cu / SNTs@3MgO. The theoretical loading of Ni was 29 wt% and the theoretical loading of Cu was 1 wt%.

[0048] Example 3

[0049] The amount of Ni(NO3)2·6H2O added in step 5) was 3.46 g and the amount of Cu(NO3)2·3H2O was 0.14 g, and the rest was the same as in Example 1 to obtain 28.5Ni-1.5Cu / SNTs@3MgO. The theoretical loading of Ni was 28.5 wt% and the theoretical loading of Cu was 1.5 wt%.

[0050] Example 4

[0051] The amount of Ni(NO3)2·6H2O added in step 5) was 3.4 g and the amount of Cu(NO3)2·3H2O was 0.19 g, and the rest was the same as in Example 1 to obtain 28Ni-2Cu / SNTs@3MgO. The theoretical loading of Ni was 28 wt% and the theoretical loading of Cu was 2 wt%.

[0052] Example 5

[0053] The amount of Ni(NO3)2·6H2O added in step 5) was 3.3 g and the amount of Cu(NO3)2·3H2O was 0.28 g, and the rest was the same as in Example 1 to obtain 27Ni-3Cu / SNTs@3MgO. The theoretical loading of Ni was 27 wt% and the theoretical loading of Cu was 3 wt%.

[0054] Example 6

[0055] The amount of TEA added in step 1) was 1.5 g and the amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g and the amount of Cu(NO3)2·3H2O was 0.1 g, and the rest was the same as in Example 1 to obtain 29Ni-1Cu / SNTs@3MgO. The theoretical loading of Ni was 29 wt% and the theoretical loading of Cu was 1 wt%.

[0056] Example 7

[0057] The amount of TEA added in step 1) was 2.0 g, the amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g, and the amount of Cu(NO3)2·3H2O was 0.1 g, and the others were the same as in Example 1 to obtain 29Ni-1Cu / SNTs@3MgO. The theoretical loading amount of Ni was 29 wt%, and the theoretical loading amount of Cu was 1 wt%.

[0058] Example 8

[0059] The amount of TEA added in step 1) was 3.0 g, the amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g, and the amount of Cu(NO3)2·3H2O was 0.1 g, and the others were the same as in Example 1 to obtain 29Ni-1Cu / SNTs@3MgO. The theoretical loading amount of Ni was 29 wt%, and the theoretical loading amount of Cu was 1 wt%.

[0060] Example 9

[0061] The amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g, and the amount of Cu(NO3)2·3H2O was 0.1 g, and the ALD cycle was deposited 1 time, i.e., 1 layer of MgO was coated, and the others were the same as in Example 1 to obtain 29Ni-1Cu / SNTs@1MgO. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Cu was 1 wt%, and 1 layer of MgO was coated.

[0062] Example 10

[0063] The amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g, and the amount of Cu(NO3)2·3H2O was 0.1 g, and the ALD cycle was deposited 5 times, i.e., 5 layers of MgO were coated, and the others were the same as in Example 1 to obtain 29Ni-1Cu / SNTs@5MgO. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Cu was 1 wt%, and 5 layers of MgO were coated.

[0064] Example 11

[0065] The amount of Ni(NO3)2·6H2O added in step 5) was 3.52 g, and the amount of Cu(NO3)2·3H2O was 0.1 g, and the ALD cycle was deposited 7 times, i.e., 7 layers of MgO were coated, and the others were the same as in Example 1 to obtain 29Ni-1Cu / SNTs@7MgO. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Cu was 1 wt%, and 7 layers of MgO were coated.

[0066] Example 12

[0067] The amounts of CTAC, TEA, CNTs, deionized water, TEOS, cyclohexane in step 1) were 2.6 g, 1.3 g, 1.3 g, 130 mL, 40 g, and 2.6 g, respectively. The amount of Ni(NO3)2·6H2O added in step 5) was 4.7 g, and the metal M precursor was Co(NO3)2·6H2O, with a dosage of 0.17 g. The other conditions were the same as in Example 1, and 29Ni-1Co / SNTs@3MgO was obtained. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Co was 1 wt%, and MgO was coated for 3 layers.

[0068] Example 13

[0069] The amounts of CTAC, TEA, CNTs, deionized water, TEOS, cyclohexane in step 1) were 2.6 g, 1.3 g, 1.3 g, 130 mL, 40 g, and 2.6 g, respectively. The amount of Ni(NO3)2·6H2O added in step 5) was 4.7 g, and the metal M precursor was Zn(NO3)2·6H2O, with a dosage of 0.16 g. The other conditions were the same as in Example 1, and 29Ni-1Zn / SNTs@3MgO was obtained. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Zn was 1 wt%, and MgO was coated for 3 layers.

[0070] Example 14

[0071] The amounts of CTAC, TEA, CNTs, deionized water, TEOS, cyclohexane in step 1) were 4 g, 2 g, 2 g, 200 mL, 60 g, and 4 g, respectively. The amount of Ni(NO3)2·6H2O added in step 5) was 7.05 g, and the metal M precursor was Zr(NO3)4·5H2O, with a dosage of 0.23 g. The other conditions were the same as in Example 1, and 29Ni-1Zr / SNTs@3MgO was obtained. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Zr was 1 wt%, and MgO was coated for 3 layers.

[0072] Example 15

[0073] The amounts of CTAC, TEA, CNTs, deionized water, TEOS, cyclohexane in step 1) were 4 g, 2 g, 2 g, 200 mL, 60 g, and 4 g, respectively. The amount of Ni(NO3)2·6H2O added in step 5) was 7.05 g, and the metal M precursor was Mo(NO3)3·5H2O, with a dosage of 0.08 g. The other conditions were the same as in Example 1, and 29Ni-1Mo / SNTs@3MgO was obtained. The theoretical loading amount of Ni was 29 wt%, the theoretical loading amount of Mo was 1 wt%, and MgO was coated for 3 layers.

[0074] Comparative Example 1

[0075] Example 1 was repeated except that in step 5), no MgO layer was coated, to obtain catalyst 29.5Ni-0.5Cu / SNTs prepared. The theoretical loading of Ni was 29.5wt%, and the theoretical loading of Cu was 0.5wt%.

[0076] Comparative Example 2

[0077] Example 1 was repeated except that in step 5), no Ni(NO3)2·6H2O was added, and the amount of Cu(NO3)2·3H2O was 0.033g, to obtain 0.5Cu / SNTs@3MgO. The theoretical loading of Ni was 0, the theoretical loading of Cu was 0.5wt%, and 3 layers of MgO were coated.

[0078] Table 1

[0079]

[0080] Comparative Example 3

[0081] Example 1 was repeated except that in step 5), no metal M precursor was added, and the amount of Ni(NO3)2·6H2O was 3.55g, to obtain 29.5Ni / SNTs@3MgO. The theoretical loading of Ni was 29.5wt%, the theoretical loading of M was 0, and 3 layers of MgO were coated.

[0082] Comparative Example 4

[0083] Example 1 was repeated except that in step 5), no Ni metal precursor and no metal M precursor were added, to obtain SNTs@3MgO. The theoretical loading of Ni metal was 0, the theoretical loading of M metal was 0, and 3 layers of MgO were coated.

[0084] Comparative Example 5

[0085] Example 1 was repeated except that in step 1), no TEA was added, to obtain catalyst 29.5Ni-0.5Cu / SNTs@3MgO. The theoretical loading of Ni was 29.5wt%, the theoretical loading of Cu was 0.5wt%, and 3 layers of MgO were coated.

[0086] In the present application, the process parameters in the preparation process of each catalyst were different, as shown in Table 1. Table 1 shows the parameter differences in the preparation process of catalysts in Examples 1-15 and Comparative Examples 1-5.

[0087] Catalyst performance test example A

[0088] To test the activity of the catalyst, the conversion rate of furfural and the selectivity of bio-based tetrahydrofuran were compared in the reaction of continuous decarbonylation and hydrogenation of furfural to prepare bio-based tetrahydrofuran.

[0089] Table 2

[0090]

[0091] Specific operation is: first in the reaction tube most lower end fills 45g of 20-40 mesh raschig ring, then the catalyst prepared above is pressed into tablets, and is ground into 20~40 mesh particle size with a mortar. 3.0g of catalyst with particle size of 20~40 mesh is loaded in the constant temperature zone of the reaction tube with an inner diameter of 13mm. After loading is completed, the reaction is carried out under the conditions of a temperature of 260℃, a feed airspeed of 0.2h -1 , H2 / furfural = 30, and normal pressure. The reaction liquid is taken out after 6h, and the activity and product selectivity of the catalyst are analyzed in a gas chromatograph. The specific results are shown in Table 2. Table 2 is catalyst evaluation data for the preparation of bio-based tetrahydrofuran by continuous decarbonylation hydrogenation of furfural.

[0092] According to the data comparison of Examples 1 to 5 in Table 2, when the loading amount of Cu metal is 0.5~1wt%, and the loading amount of Ni metal is 29~29.5wt%, the continuous decarbonylation hydrogenation of furfural has excellent activity and selectivity, the conversion rate of furfural is 98.7~99%, and the selectivity of THF is 88.1% and 87.8% respectively. The Ni and Cu bimetallic catalyst has a good synergistic effect. When the content of Cu metal is further increased, the metal nanoparticles are aggregated, which inhibits the decarbonylation hydrogenation performance of the active sites of Ni metal, and the activity of the catalyst is reduced.

[0093] According to the data comparison of Example 2 and Examples 6~8 in Table 2, the purpose of introducing TEA is to accelerate the hydrolysis-condensation rate of TEOS, the molding of the catalyst, and the improvement of the surface physical properties of the catalyst during the preparation of the catalyst. If the content of TEA is too high, it may cause excessive hydrogenation ring-opening to reduce the selectivity of THF. In this embodiment, the preferred amount of TEA added is 1~2g, and more preferably 1~1.5g.

[0094] According to the data comparison of Example 2 and Examples 9~11 in Table 2, coating a MgO layer on the surface of the catalyst is beneficial to improve the metal dispersion, prevent metal components from aggregating, leaching, and sintering, increase the basicity of the catalyst surface, and improve the catalytic activity and the selectivity of bio-based tetrahydrofuran. However, if the number of MgO coating layers is too high, the reactivity of the substrate and the metal active sites will be reduced, which will reduce the reaction performance of the catalyst. When the number of MgO coating layers is 1~3, the performance of the catalyst is best.

[0095] According to the data comparison of Example 2 and Examples 12~15 in Table 2, the electronic interaction between Co, Zn, Zr, Mo and Ni is not as good as that of Cu metal catalyst. When the loading amount of metal M is the same, the Ni-Cu bimetallic component has excellent reaction performance in the preparation of bio-based tetrahydrofuran by one-step decarbonylation hydrogenation of furfural.

[0096] According to the data comparison of Example 1 and Comparative Examples 1-5 in Table 2, the catalyst without MgO coating layer cannot control the basicity of the catalyst surface, and the dispersion of the metal component is poor, and the activity and product selectivity of the catalyst are reduced. If no Ni metal is added to the catalyst, the main metal active site is lacking, and the performance of the catalyst is significantly reduced. The second metal M in the catalyst is beneficial to improve the electronic structure of the Ni metal component and produce a synergistic effect with Ni, and if no M metal is added to the catalyst, the activity and selectivity of the catalyst are reduced. If no Ni metal and M metal are added to the catalyst, the pure silicon dioxide nanotube carrier has very low activity in the furfural decarbonylation hydrogenation reaction. If TEA is not introduced during the preparation of the catalyst, it is not conducive to the rapid formation of silicon dioxide nanotubes, resulting in a decrease in reaction performance.

[0097] Examples 16-26 are the optimization of reaction conditions for the continuous decarbonylation hydrogenation of furfural to prepare bio-based tetrahydrofuran in a fixed bed using the catalyst prepared according to Example 6. Table 3 shows the effect of reaction conditions on the performance of the THF reaction prepared by the continuous decarbonylation hydrogenation of furfural.

[0098] Table 3

[0099]

[0100] According to the data comparison results of Examples 16-21 in Table 3, increasing the reaction temperature is beneficial to improve the performance of the catalyst, but too high a reaction temperature will cause excessive hydrogenation of THF and reduce the selectivity of the target product. The temperature of the reaction is preferably 240-280°C, and the best is 260°C of Example 19 (the same as Example 6).

[0101] According to the data comparison results of Example 19 and Examples 22-27 in Table 3, as the molar ratio of H2 / furfural increases, the activity and selectivity of the catalyst gradually increase, and when the H2 / furfural ratio decreases, the performance of the catalyst is significantly reduced. However, considering the cost and energy consumption, the amount-of-substance ratio of H2 / furfural is controlled at 20-50, preferably 30-40.

[0102] According to the data comparison results of Example 19 and Examples 28-30 in Table 3, as the feed airspeed increases, the activity of the catalyst gradually decreases, which may be due to the shortening of the residence time of the reactants on the catalyst surface, resulting in insufficient reaction between furfural and the catalyst. Therefore, the feed airspeed is preferably maintained at 0.2 h -1 .

[0103] Catalyst performance test example B

[0104] The catalyst of Example 6 was tested for the life of the catalyst in the preparation of bio-based tetrahydrofuran by decarbonylation hydrogenation of furfural in a fixed bed reactor according to the reaction process conditions of Example 19, and the evaluation results are shown in Table 4. Table 4 is the life evaluation of the catalyst of the application.

[0105] Table 4

[0106]

[0107] According to the data results in Table 4, after the catalyst runs for 3000h, the performance of the catalyst does not decrease significantly, the Ni-Cu / SNTs@MgO catalyst has excellent activity, selectivity and stability, and has good industrial application prospects.

[0108] In general, the application belongs to the field of chemical catalysis, and specifically relates to a catalyst for catalyzing continuous decarbonylation hydrogenation reaction, and a preparation method and application thereof. The catalyst is Ni-M / SNTs@MgO, which comprises active metal Ni, auxiliary metal M, carrier SNTs and surface-coated MgO, the auxiliary metal M is one or more of Cu, Co, Zn, Zr and Mo, and the carrier SNTs is a silicon dioxide nanotube. The preparation method of the catalyst comprises surface-coating MgO on Ni-M / SNTs by using an atomic layer deposition method. The catalyst has low cost, excellent catalytic performance in the preparation of tetrahydrofuran by continuous decarbonylation hydrogenation of furfural, furfural conversion rate is greater than 99%, and tetrahydrofuran selectivity is greater than 90%. The catalyst has no obvious deactivation after continuous operation for more than 3000h, and has good industrial application prospects.

[0109] The above only describes the preferred embodiments of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application shall be included in the protection scope of the application.​

Claims

1. A catalyst for catalyzing a continuous decarbonylation hydrogenation reaction, characterized in that, The catalyst is Ni-M / SNTs@MgO, comprising active metal Ni, auxiliary metal M, support SNTs, and surface-coated MgO. The auxiliary metal M is one or more of Cu, Co, Zn, Zr, and Mo, and the support SNTs are silica nanotubes. The catalyst is prepared by coating the surface of MgO onto Ni-M / SNTs using atomic layer deposition. The mass fraction of active metal Ni in the catalyst is 20-35 wt%, the mass fraction of auxiliary metal M is 0.1-5 wt%, the number of MgO coating layers is one or more, and the remainder is the support. The method for preparing the carrier SNTs adopts a two-phase layering method, specifically including: mixing hexadecyltrimethylammonium chloride (CTAC), triethanolamine (TEA), carbon nanotubes (CNTs), deionized water, tetraethyl orthosilicate (TEOS), and cyclohexane, stirring at a certain temperature, and then preparing SNTs by centrifugation, drying, and calcination. The preparation method of Ni-M / SNTs@MgO catalyst precursor is as follows: a certain amount of SNTs, metallic Ni and metallic M nitrates and methanol are mixed and refluxed at a certain temperature; after centrifugation, washing with water and drying, the solid powder obtained by impregnation method is placed in the atomic layer deposition (ALD) reaction chamber, and a solution of water and bis(ethylcyclopentadienyl)magnesium, i.e. Mg(C5H4C2H5)2 is pulsed and cyclically deposited to coat the surface of Ni-M / SNTs with a MgO layer, thus obtaining the Ni-M / SNTs@MgO catalyst precursor; The catalyst precursor was calcined and reduced to obtain the Ni-M / SNTs@MgO catalyst. The calcination was carried out under a N2 or Ar atmosphere at a flow rate of 30-50 mL / min, a heating rate of 2-4 °C / min, a calcination temperature of 450-550 °C, and a calcination time of 4-6 h. The reduction was carried out using a 5% H2 / Ar mixed gas at a flow rate of 30-50 mL / min, a heating rate of 2-4 °C / min, a reduction temperature of 200-400 °C, and a reduction time of 2-4 h.

2. The catalyst according to claim 1, characterized in that, The catalyst contains 27-29.5 wt% active metal Ni; the additive metal M contains 0.5-3 wt% additive metal M; and the MgO coating consists of 1-7 layers.

3. The catalyst according to claim 1, characterized in that, The mass ratio of CTAC, TEA, CNTs, deionized water, TEOS, and cyclohexane is 2~4:1~2:1~2:100~200:30~60:2~4. During carrier preparation, the stirring temperature is 40-60℃, the stirring rate is 800-1000 r / min, and the stirring time is 18-24 h. The centrifugation rate is 8000-16000 r / min, and the centrifugation time is 5-10 min, yielding a white solid powder. The drying temperature is 80-120℃, and the drying time is 2-6 h. Calcination is carried out under a N2 or Ar atmosphere at a rate of 30-50 mL / min, a heating rate of 2-4℃ / min, a calcination temperature of 500-600℃, and a calcination time of 3-5 h.

4. The catalyst according to claim 1, characterized in that, In the preparation of the catalyst precursor, the mass ratio of SNTs, Ni nitrate, M nitrate, and methanol is 2.16-4.32:3.3-7.05:0.046-0.29:50-100; the reflux temperature is 60-80℃, the reflux time is 2-6h; the ALD reaction chamber temperature is 180-220℃, the pulse time is 1-2s, and the number of depositions is 1-7.

5. The catalyst according to claim 4, characterized in that, The nitrate of metallic Ni is Ni(NO3)2·6H2O, and the nitrate of metallic M is one or more of Cu(NO3)2·3H2O, Co(NO3)2·6H2O, Zn(NO3)2·6H2O, Zr(NO3)4·5H2O, and Mo(NO3)4·5H2O.

6. The use of a catalyst according to any one of claims 1 to 5 in the reaction of catalyzing the continuous decarbonylation and hydrogenation of furfural to prepare tetrahydrofuran, characterized in that, The reaction is carried out in a fixed-bed reactor and includes pressing Ni-M / SNTs@MgO into tablets, sieving 20-40 mesh particles as catalyst, and loading the catalyst into the isothermal zone of the reaction tube; the reaction temperature is 200-300℃; and the furfural feed mass hourly space velocity is 0.2-0.5 h⁻¹. -1 The molar ratio of hydrogen to aldehyde is 1~50.0, and the reaction pressure is atmospheric pressure.

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