Method for preparing epsilon-caprolactone through catalytic dehydrogenation of 1, 6-hexanediol

Abstract

The invention relates to a method for preparing epsilon-caprolactone by catalytic dehydrogenation of 1, 6-hexanediol, a catalyst adopted in the method takes a molecular sieve as a carrier and at least one of Sn, W, Ge and Pb as an active component, and the catalyst is in a reduced state and / or an oxide of the elements; the catalyst is prepared by the following method: introducing an active component into a molecular sieve in an ion exchange manner, or introducing active metal into the molecular sieve in an in-situ synthesis manner in the process of preparing the molecular sieve from a molecular sieve precursor. According to the method, the conversion rate of 1, 6-hexanediol is very high and reaches the advanced level of the prior art, the subsequent separation process is simplified, and the separation cost is reduced; compared with a traditional Cu-based catalyst, the preparation method has the advantages that the limitation of high cost of a traditional Pt catalyst is eliminated, and compared with the traditional Cu-based catalyst, no Cr component is adopted, so that the preparation method is green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol, in particular to a method for preparing epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol using a new catalyst, and belongs to the technical field of fine chemical products. BACKGROUND

[0002] Epsilon-caprolactone is a seven-membered cyclic lactone composed of five methylene groups (-CH2-) and one ester group (-COO-). The current research interest in epsilon-caprolactone comes from its excellent performance and wide application. The ring-opening polymerization of epsilon-caprolactone can produce poly-caprolactone, which is non-toxic, harmless and 100% biodegradable. As an important synthetic polymer material, poly-caprolactone is an important raw material for the synthesis of poly-caprolactone resin and poly-caprolactone polyol, and is applied in the fields of medicine, high-grade furniture, paint, aerospace, etc. However, the current industrial production of epsilon-caprolactone mainly adopts the cyclohexanone oxidation route, and there are a series of technical problems such as safety control, purification of polymerization inhibition and yield improvement in the synthesis process. At the same time, due to the existence of technical monopoly problem, the production of epsilon-caprolactone in China is relatively difficult.

[0003] In recent years, a research team of Sichuan University has studied the synthesis of epsilon-caprolactone by gas-phase catalytic dehydrogenation of 1,6-hexanediol using CuO / Cr2O3 / Al2O3 as the catalyst (Liu Y. Research on the synthesis of lactone monomers by catalytic dehydrogenation of diols [D]. Sichuan University, 2007. DOI: 10.7666 / d.y1212521). Wu Yanbin et al. of Meichem Chemical Co., Ltd. introduced ZnO into the CuO / Cr2O3 / Al2O3 catalyst to improve the performance of the Cu-based catalyst (Wu Y, Wu Z, Yan G. Research on a synthesis process of biodegradable polymer monomer epsilon-caprolactone [J]. Fine and Special Chemicals, 2015, 23: 37-39, DOI: 10.3969 / j.issn.1008-1100.2015.01.010). Both of the above two catalysts containing Cr species show good dehydrogenation activity of 1,6-hexanediol, but the limiting factor is that the catalyst itself has high toxicity, especially the Cr species, which causes equipment corrosion, water pollution and human carcinogenicity. Although the patent CN202110357604.1 provides a CuO-ZnO-M x O yThe M in the catalyst (M is one or more of Cr elements, Mo elements and Co elements) can be Mo and Co. However, the conversion of 1,6-hexanediol is not high in the Cu-based catalyst without Cr species, which is between 69.1-78.3%, and the unconverted 1,6-hexanediol and the target product epsilon-caprolactone can form an azeotrope, which cannot be separated by direct product distillation, and often needs to increase more separation processes, which makes the later separation process complex. It is found that in addition to the Cu-based catalyst, Pt-based catalysts are also reported to have the effect of catalyzing 1,6-hexanediol to generate epsilon-caprolactone (Acceptorless dehydrogenative lactonization of diols by Pt-loaded SnO2 catalysts[J]. RSC Advances, 2015, 5: 29072-29075, DOI: 10.1039 / c5ra03337c), but the price of the Pt-based catalyst in the field of dehydrogenation has always been an important factor limiting its application.

[0004] Therefore, the development and optimization of the key catalyst in the preparation of epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol is still a focus of research in this field. In order to overcome the limitations of the existing catalysts for the preparation of epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol and to broaden the types of catalysts for the preparation of epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol, the present application is proposed. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a method for preparing epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol, which uses a catalyst with non-noble metal as active component, thereby overcoming the high cost limitation of traditional Pt catalysts, and the components in the catalyst are less than Cr in the Cu-based catalyst 6+ In terms of toxicity, the catalyst in the present application has the advantages of green environmental protection and the like. In addition, in the method of the present application, the catalyst exhibits good dehydrogenation performance and stability, and the conversion rate of 1,6-hexanediol is high, which can simplify the subsequent separation process and reduce the separation cost.

[0006] In order to achieve the above technical purposes, the technical scheme adopted by the present application is as follows:

[0007] A method for preparing epsilon-caprolactone by catalytic dehydrogenation of 1,6-hexanediol, which uses the following catalyst to catalyze the reaction, the catalyst uses molecular sieve as carrier, at least one selected from Sn, W, Ge and Pb as active component, which is in a reduced state and / or oxide of the above elements; the catalyst is prepared by the following method: introducing the active component into the molecular sieve by ion exchange, or introducing the active metal into the molecular sieve by in-situ synthesis during the preparation of the molecular sieve by using the molecular sieve precursor.

[0008] Further, the active component is in the range of 0.5-30%, preferably 3-25%, more preferably 5-20% by weight of the total catalyst, calculated as the reduced and / or oxidic form of the active component.

[0009] Further, the molecular sieve is selected from at least one of ZSM series molecular sieve and Beta series molecular sieve.

[0010] Further, the ZSM series molecular sieve has a Si / Al atomic ratio in the range of 10-4000, preferably 200-1000, and the Beta series molecular sieve has a Si / Al atomic ratio in the range of 100-2000, preferably 250-900.

[0011] Further, specifically, the ZSM series molecular sieve is selected from at least one of ZSM-5, ZSM-10, ZSM-11, ZSM-12 and ZSM-18, and the Beta series molecular sieve is Beta-26 molecular sieve.

[0012] Further, the molecular sieve is a Na type molecular sieve after Na ion exchange.

[0013] Further, the Na type molecular sieve is prepared by mixing a solution of sodium salt with the molecular sieve, stirring, heating to perform ion exchange reaction, and optionally repeating the ion exchange process for 1-5 times, and obtaining the Na type molecular sieve after calcination. The temperature for stirring after mixing is in the range of 20-80°C, and the time is in the range of 3-18h. The temperature for heating is in the range of 90-130°C, and the time is in the range of 6-24h. The temperature for calcination is in the range of 300-800°C, and the time is in the range of 3-10h.

[0014] Further, the solution of sodium salt is an aqueous solution or an alcoholic solution, preferably an aqueous solution or an ethanol solution.

[0015] Further, the active component is introduced into the molecular sieve by ion exchange, and the specific process is as follows: mixing a solution containing active component salt with the molecular sieve, stirring, heating to perform ion exchange reaction, and optionally repeating the ion exchange process for 1-5 times, and obtaining the catalyst after calcination. The temperature for stirring after mixing is in the range of 20-80°C, and the time is in the range of 3-18h. The temperature for heating is in the range of 90-130°C, and the time is in the range of 6-24h. The temperature for calcination is in the range of 300-600°C, and the time is in the range of 3-10h.

[0016] Further, in the above method, multiple active components are introduced at one time, or multiple active components are introduced by repeating the above process.

[0017] Further, the solution containing active component salt is an aqueous solution or an alcoholic solution, preferably an aqueous solution or an ethanol solution.

[0018] Further, the active metal is introduced into the molecular sieve in an in-situ synthesis manner in the process of preparing the molecular sieve from the molecular sieve precursor, and the specific process is as follows: a precursor solution is obtained by mixing a silicon source, an aluminum source and a template agent, an aqueous solution containing an active component salt is dropped into the precursor solution, and then mixed and crystallized, dried and calcined to obtain the catalyst.

[0019] Further, the temperature for mixing before crystallization is 20-80℃, and the time is 3-18h; the temperature for crystallization is 130-180℃, and the crystallization time is 12-100h; the drying temperature is 70-140℃, the calcination temperature is 300-800℃, preferably 450-600℃, and the calcination time is 3-10h.

[0020] Further, the silicon source is at least one selected from tetraalkyl orthosilicate, silica sol and silicon dioxide; the aluminum source is at least one selected from pseudoboehmite, aluminum hydroxide, aluminum nitrate, aluminum isopropylate, aluminum sulfate, aluminum chloride and sodium metaaluminate; and the template agent is at least one selected from tetrapropylammonium bromide, cyclohexylamine, ethylenediamine, tetraalkylammonium hydroxide and cetyltrimethylammonium bromide.

[0021] Further, the active component salt is at least one selected from nitrate, acetate, sulfate and chloride of Sn, nitrate, acetate, sulfate and chloride of Pb, hydrate of ammonium paratungstate, hydrate of ammonium tungstate, tetramethyl germanium, tetraethyl germanium, tetrabutyl germanium and ethoxy germanium.

[0022] Further, the catalyst can be directly used for catalyzing the reaction under the hydrogen condition, or is used for catalyzing the reaction under the hydrogen condition after reduction treatment. The reduction treatment is carried out by using the conventional method in the art; as one of the specific embodiments, the reduction gas used in the reduction treatment is hydrogen, the reduction treatment temperature is 500-700℃, and the treatment time is 2-8h.

[0023] Further, the reaction temperature for preparing ε-caprolactone by catalytically dehydrogenating 1,6-hexanediol is 200-300℃, preferably 250-300℃, the volume space velocity of 1,6-hexanediol is 0.2-1.5h -1 , and the hydrogen / alcohol ratio is 50-200:1.

[0024] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0025] (1) In the method of the present application, the conversion rate of 1,6-hexanediol is very high, reaching the advanced level of the prior art, simplifying the subsequent separation process and reducing the separation cost.

[0026] (2) The catalyst used in the application takes at least one of Sn, W, Ge and Pb as an active component, breaks away from the high cost limitation of traditional Pt catalysts, and has green and environmentally friendly characteristics compared with traditional Cu-based catalysts which do not use Cr components.

[0027] (3) Although Sn, W, Ge and Pb are also commonly used as catalyst active components for other reactions, they have not been used in the reaction of catalytic dehydrogenation of 1,6-hexanediol to prepare ε-caprolactone, especially the reaction involves dehydrogenation and cyclization esterification. In combination with the preparation method of the application, the outstanding effect of the catalyst exceeds the expectation of those skilled in the art. DETAILED DESCRIPTION

[0028] In order to better understand the content of the application, the technical solutions of the application will be described clearly and completely in combination with the specific embodiments of the application, examples. The following embodiments are used to illustrate the application, but not to limit the scope of the application.

[0029] In addition, any method and material similar or equivalent to the described content can be applied to the method of the application. The preferred implementation methods and materials described herein are only for demonstration.

[0030] The content of each component of the catalyst prepared in the following examples is determined by XRF.

[0031] In the following examples and comparative examples, the content of each component in the product is determined by Agilent gas chromatograph.

[0032] 1,6-hexanediol conversion rate and ε-caprolactone selectivity are calculated by the following formula:

[0033]

[0034] ε-caprolactone yield (%) = 1,6-hexanediol conversion rate (%) x ε-caprolactone selectivity (%)

[0035] Wherein, n HM,i is the initial amount of 1,6-hexanediol, n HM,f is the amount of 1,6-hexanediol at the reactor outlet, n CPL，formed is the amount of ε-caprolactone generated, all of which are in moles.

[0036] Example 1

[0037] 20g of commercial ZSM-5 (silicon aluminum ratio = 400) was added to 150mL of 0.06mol / L stannous chloride (SnCl2·2H2O) ethanol solution, stirred at 60℃ for 12h, then dried in an oven at 110℃ overnight, repeated three times, and then calcined in air at 550℃ for 5h to obtain the catalyst.

[0038] The weight percentage of each component, based on the total weight of the catalyst, is: SnO25.80%, ZSM-5944.20%.

[0039] Catalyst evaluation: The catalyst was pre-reduced before reaction. The pre-reduction conditions were: hydrogen flow rate of 50 mL / min, reduction temperature of 550°C, and reduction time of 4 h. Then the 1,6-hexanediol reaction was carried out, and the reaction conditions were: reaction temperature of 260°C, volume space velocity of 0.25 h -1 , and hydrogen / alcohol ratio of 100. After the reaction was stable, the conversion of 1,6-hexanediol was 95.5%, the selectivity of ε-caprolactone was 47.9%, and the yield of ε-caprolactone was 45.7%.

[0040] After the catalyst reacted for 250 h, the dehydrogenation activity decreased, and after the reaction for 320 h, the conversion of 1,6-hexanediol decreased to 86.2%, and the yield of ε-caprolactone was 41.5%.

[0041] The catalyst was regenerated, and the regeneration conditions were: oxygen flow rate of 40 mL / min, regeneration temperature of 600°C, and regeneration time of 2 h. The regenerated catalyst was reduced, and the reduction conditions were: hydrogen flow rate of 50 mL / min, nitrogen flow rate of 50 mL / min, reduction temperature of 600°C, and reduction time of 6 h. Then the 1,6-hexanediol reaction was carried out, and the reaction conditions were: reaction temperature of 260°C, volume space velocity of 1.0 h -1 , and hydrogen / alcohol ratio of 100. The evaluation results of the regenerated catalyst were: 1,6-hexanediol conversion of 95.0%, and ε-caprolactone yield of 45.3%.

[0042] Example 2

[0043] 20 g of commercial ZSM-5 (silicon / aluminum ratio = 400) was added to a 1 mol / L aqueous sodium nitrate (NaNO3) solution, stirred at 75°C for 8 h, then washed with deionized water until neutral, dried at 110°C overnight, and calcined in air at 550°C for 5 h to obtain Na-type ZSM-5. The obtained Na-type ZSM-5 molecular sieve was added to 150 mL of a 0.06 mol / L stannous chloride (SnCl2·2H2O) ethanol solution, stirred at 60°C for 12 h, washed with a deionized water and ethanol mixed solution, dried at 110°C overnight, repeated three times, and calcined in air at 550°C for 5 h to obtain the catalyst.

[0044] The weight percentage of each component, based on the total weight of the catalyst, is: Na2O 0.21%, SnO25.75%, and ZSM-594.04%.

[0045] Catalyst evaluation: The catalyst was not reduced, and 1,6-hexanediol was directly introduced for reaction. The reaction conditions were as follows: the reaction temperature was 260°C, the volume space velocity was 0.25 h -1 , and the hydrogen / alcohol ratio was 100. The conversion of 1,6-hexanediol and the yield of ε-caprolactone showed an upward trend with the reaction. After 10 h of reaction, the reaction reached a steady state. The catalyst evaluation results were as follows: the conversion of 1,6-hexanediol was 96.5%, the selectivity of ε-caprolactone was 49.5%, and the yield of ε-caprolactone was 47.8%.

[0046] Example 3

[0047] The catalyst in Example 2 was used, and the catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: the hydrogen flow rate was 50 mL / min, the reduction temperature was 550°C, and the reduction time was 4 h. The reaction conditions were as follows: the reaction temperature was 260°C, the volume space velocity was 0.25 h -1 , and the hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: the conversion of 1,6-hexanediol was 97.0%, the selectivity of ε-caprolactone was 48.1%, and the yield of ε-caprolactone was 46.7%. After 460 h of reaction of the catalyst, the dehydrogenation activity decreased. After 550 h of reaction, the conversion of 1,6-hexanediol was 89.5%, the selectivity of ε-caprolactone was 50.1%, and the yield of ε-caprolactone was 44.8%.

[0048] Example 4

[0049] Commercial ZSM-5 (silicon / aluminum ratio = 400) and ZSM-18 (silicon / aluminum ratio = 300) were added to a 1 mol / L aqueous sodium nitrate (NaNO3) solution at a mass ratio of 1:1, stirred at 75°C for 8 h, washed with deionized water until neutral, dried at 100°C overnight, and calcined in air at 550°C for 5 h to obtain Na-type ZSM-5 and ZSM-18. The obtained Na-type ZSM-5 and ZSM-18 molecular sieves were added to a 0.05 mol / L Sn(CH3CO2)2 and 0.05 mol / L lead acetate (Pb(CH3CO2)2·3H2O) ethanol solution, stirred at 60°C for 12 h, washed with a deionized water and ethanol mixed solution, dried at 100°C overnight, repeated three times, and calcined in air at 550°C for 5 h to obtain the catalyst.

[0050] The weight percentage of each component was as follows, based on the total weight of the catalyst: Na2O 0.20%, SnO2 6.34%, PbO 9.30%, ZSM-5 42.08%, and ZSM-18 42.08%.

[0051] Catalyst evaluation: The catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: hydrogen flow rate was 50 mL / min, reduction temperature was 550 °C, and reduction time was 4 h. The reaction conditions were as follows: reaction temperature was 260 °C, volume space velocity was 0.25 h-1, and hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 97.1%, the selectivity of ε-caprolactone was 50.4%, and the yield of ε-caprolactone was 48.9%. -1

[0052] Example 5

[0053] Commercial ZSM-5 (silica / alumina ratio = 400) and Beta-26 (silica / alumina ratio = 200) were added to 1 mol / L aqueous sodium nitrate (NaNO3) solution at a ratio of 1:1 (mass ratio), stirred at 80 °C for 8 h, washed with deionized water until neutral, dried at 100 °C overnight, and calcined in air at 550 °C for 5 h to obtain Na-type ZSM-5 and Beta-26. The obtained Na-type ZSM-5 and Beta-26 molecular sieves were added to 0.05 mol / L aqueous ammonium paratungstate solution, stirred at 80 °C for 12 h, washed with deionized water, dried at 120 °C overnight, repeated three times, and calcined in air at 550 °C for 5 h. The above sample was added to 0.05 mol / L lead acetate (Pb(CH3CO2)2·3H2O) ethanol solution, stirred at 60 °C for 12 h, washed with a mixed solution of deionized water and ethanol, dried at 100 °C overnight, repeated three times, and calcined in air at 550 °C for 5 h to obtain the catalyst.

[0054] The weight percentage of each component was as follows: Na2O 0.18%, WO3 9.51%, PbO 8.99%, ZSM-5 40.66%, and Beta-26 40.66%, based on the total weight of the catalyst.

[0055] Catalyst evaluation: The catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: hydrogen flow rate was 50 mL / min, reduction temperature was 550 °C, and reduction time was 4 h. The reaction conditions were as follows: reaction temperature was 260 °C, volume space velocity was 0.25 h -1 , hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 95.6%, the selectivity of ε-caprolactone was 50.6%, and the yield of ε-caprolactone was 48.4%.

[0056] Example 6

[0057] ​Example 1 10 W 12 O 41 ·5H2O) were dissolved in 10.0 g of deionized water to form solution B; solution B was added dropwise to solution A under stirring, and the mixture was stirred at 60°C for 6 h, then transferred into an autoclave and crystallized at 160°C for 48 h. After filtration and washing with deionized water, the product was dried at 100°C overnight and calcined in air at 550°C for 5 h to obtain the catalyst.

[0058] The weight percentages of the components were as follows: Na2O 0.17%, WO3 7.48%, SnO2 7.51%, and ZSM-5 84.84%, based on the total weight of the catalyst.

[0059] Catalyst evaluation: The catalyst was pre-reduced before the reaction. The pre-reduction conditions were as follows: hydrogen flow rate 50 mL / min, reduction temperature 550°C, and reduction time 4 h. The reaction conditions were as follows: reaction temperature 260°C, volume space velocity 0.25 h -1 , and hydrogen / alcohol ratio 100. The results of the catalyst evaluation were as follows: 1,6-hexanediol conversion 99.0%, selectivity of ε-caprolactone 52.1%, and yield of ε-caprolactone 51.6%.

[0060] Example 7

[0061] Example 1 10 W 12 O 41• 0.93 g tin dimethyl dichloride (C2H6Cl2Sn), 0.71 g ammonium paratungstate ((NH4)10H32W12O40«5H2O), 0.73 g lead acetate (Pb((CH3CO2)2«3H2O) were dissolved in 10.0 g deionized water to form solution B; solution B was added dropwise to solution A under stirring condition of solution A, and 0.58 g germanium oxide fine powder was added, the above mixture was moved into an autoclave after stirring at 60 °C for 6 h, and crystallization was carried out at 160 °C for 48 h. After filtration and washing with deionized water, drying overnight at 100 °C, and calcination in air at 550 °C for 5 h, a catalyst was obtained.

[0062] The weight percentage of each component was as follows: Na2O 0.16%, WO3 4.58%, SnO2 4.60%, PbO 3.11%, GeO2 4.20%, ZSM-5 83.35%, based on the total weight of the catalyst.

[0063] Catalyst evaluation: The catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: hydrogen flow rate was 50 mL / min, reduction temperature was 550 °C, and reduction time was 4 h. The reaction conditions were as follows: reaction temperature was 260 °C, volume space velocity was 0.25 h-1, and hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 98.0%, the selectivity of ε-caprolactone was 50.0%, and the yield of ε-caprolactone was 49.0%. -1

[0064] Example 8

[0065] 0.93 g tin dimethyl dichloride (C2H6Cl2Sn), 0.71 g ammonium paratungstate ((NH4)10H32W12O40«5H2O), 0.73 g lead acetate (Pb((CH3CO2)2«3H2O) were dissolved in 10.0 g deionized water to form solution B; solution B was added dropwise to solution A under stirring condition of solution A, and 0.58 g germanium oxide fine powder was added, the above mixture was moved into an autoclave after stirring at 60 °C for 6 h, and crystallization was carried out at 160 °C for 48 h. After filtration and washing with deionized water, drying overnight at 100 °C, and calcination in air at 550 °C for 5 h, a catalyst was obtained. 10 W 12 O 41 • 0.93 g tin dimethyl dichloride (C2H6Cl2Sn), 0.71 g ammonium paratungstate ((NH4)10H32W12O40«5H2O), 0.73 g lead acetate (Pb((CH3CO2)2«3H2O) were dissolved in 10.0 g deionized water to form solution B; solution B was added dropwise to solution A under stirring condition of solution A, and 0.58 g germanium oxide fine powder was added, the above mixture was moved into an autoclave after stirring at 60 °C for 6 h, and crystallization was carried out at 160 °C for 48 h. After filtration and washing with deionized water, drying overnight at 100 °C, and calcination in air at 550 °C for 5 h, a catalyst was obtained.

[0066] The weight percentage of each component was as follows: Na2O 0.30%, WO3 7.18%, SnO2 5.54%, PbO 4.75%, ZSM-5 82.23%, based on the total weight of the catalyst. ​

[0067] Catalyst evaluation: The catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: hydrogen flow rate was 50 mL / min, reduction temperature was 550 °C, and reduction time was 4 h. The reaction conditions were as follows: reaction temperature was 260 °C, volume space velocity was 0.25 h -1 , and hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 96.5%, selectivity of ε-caprolactone was 55.0%, and yield of ε-caprolactone was 53.1%. After the catalyst reacted for 580 h, dehydrogenation activity decreased, and after the catalyst reacted for 650 h, 1,6-hexanediol conversion decreased to 90.1%, and yield of ε-caprolactone was 50.5%. The catalyst was calcined in air at 600 °C for 6 h and then reduced in hydrogen at a flow rate of 50 mL / min and a temperature of 550 °C for 4 h. The reaction conditions were as follows: reaction temperature was 260 °C, volume space velocity was 0.25 h -1 , and hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 96.1%, selectivity of ε-caprolactone was 55.5%, and yield of ε-caprolactone was 53.3%.

[0068] Comparative Example 1

[0069] Cu-based composite metal oxide CuO-ZnO-Co2O3-MoO3 was prepared by coprecipitation. A certain amount of copper nitrate, zinc nitrate, cobalt nitrate and ammonium molybdate were weighed and prepared into a metal ion aqueous solution with a total molar concentration of metal ions of 1 mol / L. A 1 mol / L sodium carbonate aqueous solution was prepared as a precipitant. A beaker containing 100 mL of deionized water was placed in a water bath, the temperature was set to 60 °C, and stirring was started. The metal ion aqueous solution and the sodium carbonate aqueous solution were added dropwise into the beaker, and the pH value was detected. The dropping speed of the precipitant was adjusted to keep the pH value of the system between 7.5 and 8.5. The obtained precipitate was aged at 80 °C for 2 h. After filtration and washing, the precipitate was dried at 100 °C for 10 h, calcined in a muffle furnace at 500 °C for 4 h, and pressed into a tablet. The composite metal oxide CuO-ZnO-Co2O3-MoO3 was sieved to obtain a composite metal oxide with a mesh size of 20-40. The composition of the composite metal oxide was as follows: CuO 38.10%, ZnO 38.50%, Co2O3 6.40%, and MoO3 17.00%.

[0070] The 1,6-hexanediol dehydrogenation reaction was carried out in a fixed bed reactor. The catalyst was pre-reduced before reaction. The pre-reduction conditions were as follows: hydrogen flow rate was 50 mL / min, nitrogen flow rate was 50 mL / min, reduction temperature was 300 °C, and reduction time was 6 h. The reaction conditions were as follows: reaction temperature was 290 °C, volume space velocity was 1.0 h -1 , and hydrogen / alcohol ratio was 100. The catalyst evaluation results were as follows: 1,6-hexanediol conversion was 65.9%, selectivity of ε-caprolactone was 64.3%, and yield of ε-caprolactone was 42.4%.

Claims

1. A method for preparing ε-caprolactone by catalytic dehydrogenation of 1,6-hexanediol, characterized in that, The catalyst is used to catalyze the reaction. The catalyst is supported by a molecular sieve and has at least one active component selected from Sn, W, Ge and Pb, which are in the reduced state and / or oxide of the above elements. The catalyst is prepared by the following method: introducing the active component into the molecular sieve by ion exchange, or introducing the active metal into the molecular sieve in situ during the preparation of the molecular sieve using a molecular sieve precursor.

2. The method according to claim 1, characterized in that, The active component accounts for 0.5-30% of the total weight of the catalyst.

3. The method according to claim 1, characterized in that, The molecular sieve is selected from at least one of the ZSM series molecular sieves and the Beta series molecular sieves.

4. The method according to claim 3, characterized in that, The ZSM series molecular sieves have a silicon-to-aluminum atomic ratio of 10-4000 and are selected from at least one of ZSM-5, ZSM-10, ZSM-11, ZSM-12 and ZSM-18.

5. The method according to claim 3, characterized in that, The Beta series molecular sieve is Beta-26 molecular sieve, with a silicon-to-aluminum atomic ratio of 100-2000.

6. The method according to claim 1, characterized in that, The molecular sieve is a Na-type molecular sieve that has undergone Na ion exchange.

7. The method according to claim 6, characterized in that, The preparation method of the Na-type molecular sieve is as follows: a sodium salt solution is mixed with the molecular sieve, stirred, and heated to carry out an ion exchange reaction. The above ion exchange process can be selectively repeated 1-5 times. After calcination, the Na-type molecular sieve is obtained.

8. The method according to claim 7, characterized in that, The mixing temperature is 20-80ºC and the stirring time is 3-18h; the heating temperature is 90-130ºC and the heating time is 6-24h; the calcination temperature is 300-800ºC and the calcination time is 3-10h.

9. The method according to claim 1, characterized in that, The process of introducing the active component into the molecular sieve by ion exchange is as follows: the solution containing the active component salt is mixed with the molecular sieve, stirred, and heated to carry out the ion exchange reaction. The above ion exchange process can be selectively repeated 1-5 times, and the catalyst is obtained after calcination.

10. The method according to claim 9, characterized in that, The mixing temperature is 20-80ºC and the stirring time is 3-18h; the heating temperature is 90-130ºC and the heating time is 6-24h; the calcination temperature is 300-600ºC and the calcination time is 3-10h.

11. The method according to claim 9, characterized in that, Multiple active components can be introduced in a single step, or the above process can be repeated to introduce multiple active components.

12. The method according to claim 1, characterized in that, In the process of preparing molecular sieves using molecular sieve precursors, active metals are introduced into the molecular sieves in an in-situ synthesis manner. Specifically, a precursor solution is obtained by mixing a silicon source, an aluminum source, and a template agent. An aqueous solution containing the active component salt is then added dropwise to the precursor solution. After mixing, the solution is crystallized, dried, and calcined to obtain the catalyst.

13. The method according to claim 12, characterized in that, The mixing temperature before crystallization is 20-80ºC, and the time is 3-18h; the crystallization temperature is between 130-180ºC, and the crystallization time is 12-100h; the drying temperature is 70-140ºC, the calcination temperature is 300-800ºC, and the calcination time is 3-10h.

14. The method according to claim 12, characterized in that, The silicon source is selected from at least one of tetraalkyl orthosilicate, silica sol, and silicon dioxide; the aluminum source is selected from at least one of boehmite, aluminum hydroxide, aluminum nitrate, aluminum isopropoxide, aluminum sulfate, aluminum chloride, and sodium aluminate; the template agent is selected from at least one of tetrapropylammonium bromide, cyclohexylamine, ethylenediamine, tetraalkylammonium hydroxide, and hexadecyltrimethylammonium bromide.

15. The method according to claim 9 or 12, characterized in that, The active component salt is selected from at least one of the following: Sn nitrate, acetate, sulfate and chloride; Pb nitrate, acetate, sulfate and chloride; ammonium paratungstate hydrate; ammonium tungstate hydrate; tetramethylgermanium; tetraethylgermanium; tetrabutylgermanium; and ethoxygermanium.

16. The method according to claim 1, characterized in that, The reaction temperature for the catalytic dehydrogenation of 1,6-hexanediol to prepare ε-caprolactone is 200-300ºC, and the volume hourly space velocity (VHSV) of 1,6-hexanediol is 0.2-1.5 h⁻¹. -1 The hydrogen-to-ethanol ratio is 50-200:1.

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