A carbon-based catalyst, a preparation method and application thereof

Abstract

The present application provides a carbon-based catalyst and its preparation method and application, and belongs to the technical field of tetrahydrothiophene production technology, to solve the technical problems of low conversion rate and poor long-term catalytic stability in the reaction of tetrahydrofuran direct sulfurization to prepare tetrahydrothiophene.(1) Biomass carbon source is treated with phosphoric acid;(2) The biomass carbon source treated in step (1) is mixed and dispersed with aluminum-containing compound or molybdenum-containing compound in solvent I, and after the reaction is finished, the porous carbon precursor is evaporated to dryness;(3) The porous carbon precursor is mixed and dispersed with rare earth metal salt or transition metal compound in solvent II, and evaporated to dryness to obtain the catalyst precursor;(4) The catalyst precursor is carbonized to obtain the carbon-based catalyst.The initial conversion rate of tetrahydrofuran of the catalyst is 99.5%, the maximum value of tetrahydrothiophene selectivity is 99.7%, and after 1000h continuous catalytic reaction evaluation, the maximum conversion rate of the catalyst is 98.9%.

Description

Technical Field

[0001] This invention belongs to the technical field of tetrahydrothiophene production technology, and particularly relates to a carbon-based catalyst, its preparation method, and its application. Background Technology

[0002] Tetrahydrothiophene (THT) is an important sulfur-containing saturated heterocyclic compound widely used as an odorant and warning agent in natural gas due to its distinctive odor. Natural gas itself is colorless and odorless, making leaks undetectable and highly prone to causing accidents. Currently, international standards require the use of tetrahydrothiophene as an odorant for city gas, natural gas, and other gases, replacing previously used odorants such as ethanethiol. Tetrahydrothiophene can also be used as an intermediate in the production of novel pharmaceuticals, pesticides, and polymer synthetic materials, and in the formulation of dental and pharmaceutical primers. With technological advancements, many applications and functions of tetrahydrothiophene are being developed, and domestic demand is gradually increasing.

[0003] The tetrahydrofuran synthesis method is a recently developed process for producing tetrahydrothiophene. Using tetrahydrofuran as a raw material, it involves reacting with hydrogen sulfide in a tubular fixed-bed reactor in the presence of a composite catalyst, undergoing a one-step thiochemical reaction at high temperature and atmospheric pressure to synthesize tetrahydrothiophene. The entire process comprises four parts: raw material and recovery system, synthesis reaction, product distillation, and waste treatment. This method offers advantages such as simple process flow, low investment, and easy waste treatment. Currently, however, it faces challenges such as high catalyst synthesis costs, low catalyst conversion rates, and poor catalyst stability. Summary of the Invention

[0004] To address the technical problems of low catalyst conversion and poor long-term catalytic stability in the direct sulfidation of tetrahydrofuran to tetrahydrothiophene, this invention proposes a carbon-based catalyst, its preparation method, and its application. This catalyst features mild reaction conditions, high reaction activity, high selectivity, high catalyst stability, and low cost.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A carbon-based catalyst, the preparation method of which includes the following steps:

[0007] (1) Treat the biomass carbon source with strong acid;

[0008] (2) The biomass carbon source treated in step (1) is mixed and dispersed with aluminum-containing or molybdenum-containing compounds in solvent I for reaction. After the reaction is completed, the mixture is evaporated or filtered to obtain a porous carbon precursor.

[0009] (3) The porous carbon precursor and rare earth metal salt or transition metal compound are mixed and dispersed in solvent II, stirred evenly, evaporated or filtered to obtain the catalyst precursor.

[0010] (4) Carbonize the catalyst precursor to obtain a carbon-based catalyst.

[0011] The biomass carbon source is one of the following: sawdust, straw, peanut shells, bamboo, coconut shells, or polymer waste.

[0012] The strong acid is phosphoric acid. The phosphoric acid treatment process is as follows: the biomass carbon source is dispersed in phosphoric acid and stirred at 70-90℃ for 1-3 hours, and then filtered. The concentration of the phosphoric acid is 40-85wt%. The mass ratio of biomass carbon source to phosphoric acid is 1:(1-10).

[0013] The aluminum-containing compound is aluminum isopropoxide, aluminum hydroxide, sodium aluminate, aluminum dihydrogen phosphate, aluminum sec-butoxide, aluminum tert-butoxide, or aluminum triethanolamine; the molybdenum-containing compound is one of ammonium molybdate, molybdic acid, phosphomolybdic acid, or molybdic acid.

[0014] In step (2), the mass ratio of aluminum-containing compound or molybdenum-containing compound, biomass carbon source, and solvent I is (1-3):7:(10-20); the reaction conditions in step (2) are: reaction temperature of 120-200℃, reaction time of 1-24h, and stirring speed of 200-500rpm / min.

[0015] The rare earth metal salt is cerium nitrate or cerium sulfate; the transition metal compound is one of ammonium tungstate, vanadium oxalate, niobium oxalate or phosphotungstic acid; the mass ratio of the rare earth metal salt or transition metal compound, biomass carbon source and solvent II in step (3) is (1-3):7:(10-20).

[0016] Solvent I and Solvent II are respectively one of ethanol, methanol, acetone or distilled water.

[0017] The carbonization in step (4) involves calcining the catalyst precursor in an inert atmosphere, wherein the calcination temperature is 600-800℃, the calcination time is 5-24h, and the heating rate is 5-20℃ / min.

[0018] An application of a carbon-based catalyst, wherein the carbon-based catalyst is used to catalyze the sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, the steps being: mixing tetrahydrofuran and hydrogen sulfide in a mass ratio of 2:(1-2), adding the carbon-based catalyst, and reacting at 240-280℃ for 1-30 min; the mass ratio of tetrahydrofuran to carbon-based catalyst is (1400-1000):1.

[0019] The beneficial effects of this invention are as follows: Firstly, this invention employs a high-concentration phosphoric acid pretreatment of the biomass carbon source, chemically carbonizing and activating the surface of the biomass carbon source. This allows aluminum or molybdenum compounds to be uniformly and effectively dispersed in the pores and surface of the biomass carbon material. This not only realizes the strong acidic sites of aluminum and molybdenum atoms but also leverages the hierarchical pore structure and high specific surface area of ​​the carbon material, resulting in an extended catalyst lifetime. Furthermore, the aluminum and molybdenum atoms in the catalyst prepared by this invention exhibit more significant catalytic activity compared to other metal atoms such as iron, copper, and cobalt. Simultaneously, the rare earth metal salts or transition metal compounds exhibit a synergistic effect with aluminum or molybdenum, primarily through diatomic interactions, which enhances both the catalyst's stability and its selectivity for tetrahydrothiophene. Catalytic performance evaluation showed that the catalyst achieved a maximum initial conversion rate of 99.5% for tetrahydrofuran and a maximum selectivity of 99.7% for tetrahydrothiophene. After 1000 hours of continuous catalytic reaction, the maximum catalyst conversion rate reached 98.9%. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] The catalyst preparation method in this embodiment is as follows:

[0023] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was mixed and dispersed with 10 g of aluminum isopropoxide in 100 mL of distilled water, stirred and reacted, and filtered to obtain a porous carbon precursor. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0024] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and 30 g of vanadium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0025] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0026] The initial conversion rate of the catalyst was 99.5%, the selectivity for tetrahydrothiophene was 99.0%, and after 1000 h of catalytic reaction, the conversion rate was 98.9%.

[0027] Example 2

[0028] The catalyst preparation method in this embodiment is as follows:

[0029] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was mixed with 10 g of phosphomolybdic acid and dispersed in 100 mL of distilled water, stirred and reacted, and filtered to obtain a porous carbon precursor. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0030] (2) First, the porous carbon precursor obtained in the first step is mixed with 200 mL of distilled water and 30 g of vanadium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0031] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0032] The initial conversion rate of the catalyst was 99.1%, the selectivity for tetrahydrothiophene was 98.8%, and after 1000 h of catalytic reaction, the conversion rate was 98.9%.

[0033] Example 3

[0034] The catalyst preparation method in this embodiment is as follows:

[0035] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was then mixed and dispersed with 10 g of aluminum isopropoxide in 200 mL of distilled water, stirred, and reacted. After filtration, a porous carbon precursor was obtained. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0036] (2) First, the porous carbon precursor obtained in the first step is mixed with 200 mL of distilled water and 30 g of cerium sulfate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0037] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0038] The initial conversion rate of the catalyst was 99.1%, the selectivity for tetrahydrothiophene was 98.5%, and after 1000 h of catalytic reaction, the conversion rate was 98.0%.

[0039] Example 4

[0040] The catalyst preparation method in this embodiment is as follows:

[0041] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was mixed and dispersed with 10 g of phosphomolybdic acid in 200 mL of distilled water, stirred and reacted, and filtered to obtain a porous carbon precursor. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0042] (2) First, the porous carbon precursor obtained in the first step is mixed with 200 mL of distilled water and 30 g of cerium sulfate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0043] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0044] The initial conversion rate of the catalyst was 98.3%, the selectivity for tetrahydrothiophene was 98.4%, and after 1000 h of catalytic reaction, the conversion rate was 97.5%.

[0045] Example 5

[0046] The catalyst preparation method in this embodiment is as follows:

[0047] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was then mixed and dispersed with 10 g of aluminum dihydrogen phosphate in 100 mL of distilled water, stirred, and reacted. After filtration, a porous carbon precursor was obtained. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0048] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and 30 g of phosphotungstic acid and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0049] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0050] The initial conversion rate of the catalyst was 99.3%, the selectivity for tetrahydrothiophene was 98.6%, and after 1000 h of catalytic reaction, the conversion rate was 98.0%.

[0051] Example 6

[0052] The catalyst preparation method in this embodiment is as follows:

[0053] (1) Under the conditions of a pretreatment temperature of 70℃, a pretreatment speed of 200 rpm / min, and a pretreatment stirring time of 1 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was then mixed, stirred, and reacted with 10 g of aluminum isopropoxide, and finally filtered to obtain a porous carbon precursor. The mixing and reaction time was 1 h, the stirring speed was 200 rpm / min, and the reaction temperature was 120℃.

[0054] (2) First, the porous carbon precursor obtained in the first step is mixed with 200 mL of distilled water and 10 g of cerium nitrate and stirred. The mixture is then placed in an oven to dry and obtain the catalyst precursor. The drying temperature is 100 °C and the drying time is 24 h. Then, it is placed in a tube furnace to carbonize and obtain catalyst 2. The calcination temperature is 600 °C and the calcination time is 5 h. The heating rate is 5 °C / min and the nitrogen flow rate is 15 mL / min.

[0055] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 240°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1 and a mass ratio of tetrahydrofuran to catalyst of 1400:1.

[0056] The initial conversion rate of the catalyst was 99.0%, the selectivity for tetrahydrothiophene was 99.7%, and after 1000 h of catalytic reaction, the conversion rate was 98.6%.

[0057] Example 7

[0058] The catalyst preparation method in this embodiment is as follows:

[0059] (1) Under the conditions of a pretreatment temperature of 80℃, a pretreatment speed of 200 rpm / min, and a pretreatment stirring time of 2 h, 70 g of coconut shell and 70 g of phosphoric acid (85 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was then mixed and dispersed with 30 g of molybdic acid in 200 mL of acetone, stirred and reacted, and finally filtered to obtain a porous carbon precursor. The mixing reaction time was 3 h, the stirring speed was 200 rpm / min, and the reaction temperature was 200℃.

[0060] (2) First, the porous carbon precursor obtained in the first step is mixed with 200 mL of ethanol and 10 g of ammonium tungstate and then placed in an oven to dry to obtain a catalyst precursor. The drying temperature is 100 °C and the drying time is 24 h. Then, it is placed in a tube furnace to carbonize to obtain a catalyst. The calcination temperature is 800 °C and the calcination time is 10 h. The heating rate is 20 °C / min and the nitrogen flow rate is 15 mL / min.

[0061] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 260°C for 15 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:2 and a mass ratio of tetrahydrofuran to catalyst of 1200:1.

[0062] The initial conversion rate of the catalyst was 98.9%, the selectivity for tetrahydrothiophene was 99.6%, and after 1000 h of catalytic reaction, the conversion rate was 97.9%.

[0063] Example 8

[0064] The catalyst preparation method in this embodiment is as follows:

[0065] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 200 rpm / min, and a pretreatment stirring time of 3 h, 700 g of coconut shell and 700 g of phosphoric acid (40 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was mixed and dispersed with 20 g of aluminum hydroxide in 150 mL of ethanol, stirred and reacted, and finally evaporated to dryness to obtain a porous carbon precursor. The mixing reaction time was 2 h, the stirring speed was 200 rpm / min, and the reaction temperature was 150℃.

[0066] (2) First, the porous carbon precursor obtained in the first step is mixed with 150 mL of distilled water and 10 g of niobium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 100 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 2. The calcination temperature is 700 °C and the calcination time is 24 h. The heating rate is 10 °C / min and the nitrogen flow rate is 15 mL / min.

[0067] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 30 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1 and a mass ratio of tetrahydrofuran to catalyst of 1000:1.

[0068] The initial conversion rate of the catalyst was 99.3%, the selectivity for tetrahydrothiophene was 99.4%, and after 1000 h of catalytic reaction, the conversion rate was 98.1%.

[0069] Comparative Example 1

[0070] The catalyst preparation method in this embodiment is as follows:

[0071] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture. Then, the mixture was mixed, stirred, and reacted, and finally filtered to obtain a porous carbon precursor. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0072] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and 30 g of vanadium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain the comparative catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0073] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to comparative catalyst 1 was 1000:1.

[0074] The initial conversion rate of the catalyst was 81.5%, the selectivity for tetrahydrothiophene was 82.7%, and after 1000 h of catalytic reaction, the conversion rate was 9.1%.

[0075] Comparative Example 2

[0076] The catalyst preparation method in this embodiment is as follows:

[0077] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500rpm / min, and a pretreatment stirring time of 3h, 70g of coconut shell and 10g of aluminum isopropoxide were first mixed, stirred and reacted, and then filtered to finally obtain a porous carbon precursor. The mixing reaction time was 24h, the stirring speed was 500rpm / min, and the reaction temperature was 200℃.

[0078] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and 30 g of vanadium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain the comparative catalyst 2. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0079] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1 and a mass ratio of tetrahydrofuran to catalyst of 1000:1.

[0080] The initial conversion rate of the catalyst was 79.3%, the selectivity for tetrahydrothiophene was 84.9%, and after 1000 h of catalytic reaction, the conversion rate was 10.5%.

[0081] Comparative Example 3

[0082] The difference from Example 1 is that the pretreatment in step (1) uses a phosphoric acid concentration of 15 wt%, while the other steps are the same.

[0083] The initial conversion rate of the catalyst was 81.2%, the selectivity for tetrahydrothiophene was 83.8%, and after 1000 h of catalytic reaction, the conversion rate was 22.5%.

[0084] Comparative Example 4

[0085] The catalyst preparation method in this embodiment is as follows:

[0086] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell was first pretreated with 100 mL of phosphoric acid (50 wt%) to obtain a mixture. Then, the mixture was mixed, stirred, and reacted, and finally filtered to obtain a porous carbon precursor. The mixing and reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0087] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and stirred. The whole body is placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120℃ and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain the comparative catalyst 3. The calcination temperature is 800℃ and the calcination time is 24 h. The heating rate is 20℃ / min and the nitrogen flow rate is 20 mL / min.

[0088] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1 and a mass ratio of tetrahydrofuran to catalyst of 1000:1.

[0089] The initial conversion rate of the catalyst was 82.5%, the selectivity for tetrahydrothiophene was 83.4%, and after 1000 h of catalytic reaction, the conversion rate was 15.2%.

[0090] Comparative Example 5

[0091] The catalyst preparation method in this embodiment is as follows:

[0092] (1) Under the conditions of a pretreatment temperature of 90℃, a pretreatment speed of 500 rpm / min, and a pretreatment stirring time of 3 h, 70 g of coconut shell and 200 g of phosphoric acid (50 wt%) were first mixed and pretreated to obtain a mixture, which was then filtered. The filtered product was mixed with 10 g of ferric nitrate nonahydrate and dispersed in 100 mL of distilled water, stirred and reacted, and filtered to obtain a porous carbon precursor. The mixing reaction time was 24 h, the stirring speed was 500 rpm / min, and the reaction temperature was 200℃.

[0093] (2) First, the porous carbon precursor obtained in the first step is mixed with 100 mL of distilled water and 30 g of vanadium oxalate and stirred. The mixture is then placed in an oven for drying to obtain the catalyst precursor. The drying temperature is 120 °C and the drying time is 24 h. Then, it is placed in a tube furnace for carbonization to obtain catalyst 1. The calcination temperature is 800 °C and the calcination time is 24 h. The heating rate is 20 °C / min and the nitrogen flow rate is 20 mL / min.

[0094] (3) The reaction to produce tetrahydrothiophene by direct sulfidation of tetrahydrofuran was carried out at a temperature of 280°C for 1 min, with a mass ratio of tetrahydrofuran to hydrogen sulfide of 2:1. The mass ratio of tetrahydrofuran to catalyst 1 was 1000:1.

[0095] The initial conversion rate of the catalyst was 67.4%, the selectivity for tetrahydrothiophene was 81.7%, and after 1000 h of catalytic reaction, the conversion rate was 61.3%.

[0096] Comparative Example 6

[0097] The difference from Comparative Example 5 is that 10g of ferric nitrate nonahydrate in step (1) is replaced with copper nitrate trihydrate, while the other steps are the same.

[0098] The initial conversion rate of the catalyst was 64.1%, the selectivity for tetrahydrothiophene was 80.2%, and after 1000 h of catalytic reaction, the conversion rate was 57.1%.

[0099] Comparative Example 7

[0100] The difference from Comparative Example 5 is that 10g of ferric nitrate nonahydrate in step (1) is replaced with cobalt nitrate hexahydrate, while the other steps are the same.

[0101] The initial conversion rate of the catalyst was 58.9%, the selectivity for tetrahydrothiophene was 79.6%, and after 1000 h of catalytic reaction, the conversion rate was 53.9%.

[0102] Table 1 Catalytic activity and stability of catalysts

[0103]

[0104]

[0105] Table 1 shows that, compared with Comparative Examples 1 and 4, the catalyst prepared in Example 1 exhibits higher conversion rate and selectivity, indicating a synergistic effect between aluminum and vanadium. In Comparative Examples 2 and 3, the catalysts prepared without high-concentration acid pretreatment showed significantly lower conversion rates and selectivity. This is mainly attributed to the fact that strong acids pre-carbonize and activate the surface of the biomass carbon source, which is more conducive to the adsorption of aluminum- or molybdenum-containing compounds, and the final carbonization further stabilizes them. Comparative Examples 5-7 show that aluminum- or molybdenum-containing compounds exhibit higher conversion rates and activities compared to other transition metals such as iron, copper, and cobalt.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a carbon-based catalyst in the catalytic sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, characterized in that, Includes the following steps: Tetrahydrofuran and hydrogen sulfide were mixed in a mass ratio of 2:(1-2), and a carbon-based catalyst was added. The mixture was reacted at 240-280℃ for 1-30 min. The mass ratio of tetrahydrofuran to the carbon-based catalyst was (1400-1000):

1. The carbon-based catalyst is prepared by a method comprising the following steps: (1) The biomass carbon source is pretreated with phosphoric acid at a concentration of 40-85wt%, and the mass ratio of biomass carbon source to phosphoric acid is 1:(1-10). The mixture is stirred at 70-90℃ for 1-3 hours. (2) The biomass carbon source treated in step (1) is mixed and dispersed with aluminum-containing or molybdenum-containing compounds in solvent I and reacted at 120-200℃ for 1-24h. After the reaction is completed, the mixture is evaporated or filtered to obtain a porous carbon precursor. The mass ratio of the aluminum-containing or molybdenum-containing compounds, biomass carbon source and solvent I is (1-3):7:(10-20). (3) The porous carbon precursor and rare earth metal salt or transition metal compound are mixed and dispersed in solvent II, stirred evenly, evaporated or filtered to obtain catalyst precursor; the rare earth metal salt is cerium nitrate or cerium sulfate; the transition metal compound is ammonium tungstate, vanadium oxalate, niobium oxalate or phosphotungstic acid; the mass ratio of the rare earth metal salt or transition metal compound, biomass carbon source and solvent II is (1-3):7:(10-20); (4) The catalyst precursor obtained in step (3) is carbonized in an inert atmosphere at 600-800℃ for 5-24h to obtain a carbon-based catalyst.

2. The application of the carbon-based catalyst according to claim 1 in the catalytic sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, characterized in that, The biomass carbon source is one of the following: wood chips, straw, peanut shells, bamboo, coconut shells, or polymer waste.

3. The application of the carbon-based catalyst according to claim 1 in the catalytic sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, characterized in that, The molybdenum-containing compound is one of ammonium molybdate, molybdic acid, phosphomolybdic acid, or silicomolybdic acid; the aluminum-containing compound is one of aluminum isopropoxide, aluminum hydroxide, sodium aluminate, aluminum dihydrogen phosphate, aluminum sec-butoxide, aluminum tert-butoxide, or aluminum triethanolamine.

4. The application of the carbon-based catalyst according to claim 1 in the catalytic sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, characterized in that, Solvent I and Solvent II are each independently one of ethanol, methanol, acetone or distilled water.

5. The application of the carbon-based catalyst according to claim 1 in the catalytic sulfidation of tetrahydrofuran to prepare tetrahydrothiophene, characterized in that, In the carbonization step, the heating rate is 5-20℃ / min.

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