Preparation and application of high-stability catalyst for preparing bioethylene through bioethanol dehydration

Abstract

The invention relates to a high-stability heteropolyacid catalyst for preparing bioethylene through dehydration of bioethanol. A preparation method of the high-stability heteropolyacid catalyst comprises the following steps: (1) loading an auxiliary agent; and (2) loading an active component. The catalyst is prepared by taking common silicon oxide as a carrier and loading an auxiliary agent and an active component step by step, the condition is mild, and the process is stable and controllable. By loading a proper amount of metal nickel, the adsorption of a precursor generating carbon deposition is promoted, and an active component for catalyzing the dehydration of bioethanol is protected, so that the stability of the catalyst is improved. The prepared catalyst has the advantages of low reaction temperature, high activity, strong carbon deposition resistance, good stability at high space velocity and the like.

Description

Technical Field

[0001] The invention relates to a catalytic method for preparing bio-ethylene by dehydrating bio-ethanol, and in particular to a catalytic dehydration method for bio-ethanol on a supported heteropolyacid catalyst modified by an auxiliary agent. Background Art

[0002] Ethylene is an important indicator of a country's petrochemical level. Ethylene is an important chemical raw material that can be used to synthesize important chemical products such as polyethylene, ethylene oxide, polyvinyl chloride, PET, and ethylbenzene. At present, my country's ethylene production is mainly produced through naphtha cracking and coal-to-methanol olefins, with a large production scale of more than one million tons per year. The use of ethanol dehydration to ethylene technology can get rid of the constraints of oil and gas resources, realize the flexible production of small and medium-sized high-purity ethylene, and fill the market demand for small and medium-sized ethylene. Raw material ethanol has a wide range of sources and can be produced through fermentation or thermochemical conversion processes from biomass, industrial waste gas, coal, solid waste, etc. Using bioethanol as a raw material is of great significance for reducing greenhouse gas emissions and achieving dual carbon goals. The bioethanol dehydration to ethylene technology has a simple reaction process, easy separation of reaction products, and is environmentally friendly. It is suitable for small-scale production and can partially or completely replace petroleum ethylene. It has important economic value and energy strategic significance.

[0003] The development of efficient catalysts is the key to the production of ethylene by dehydration of bioethanol. The heterogeneous catalysts used for the dehydration of ethanol to produce ethylene mainly include activated alumina, molecular sieves and heteropoly acids. Activated alumina has high mechanical strength and good selectivity, but high reaction temperature, low space velocity, high unit energy consumption and low equipment utilization. Patent CN 101244971 A reports a preparation method of a nano molecular sieve catalyst for dehydration of bioethanol to produce ethylene, which has low reaction temperature, high ethanol conversion rate and high ethylene selectivity, but the process requires the introduction of carrier gas, poor catalyst stability, harsh preparation conditions and difficult control of crystallinity, which limit its further industrial application. Patents CN 105709822 A and CN 106944139 A disclose a method for the dehydration of ethanol to produce ethylene catalyzed by heteropoly acid ammonium salt. However, when the above-mentioned unmodified catalyst is used for the dehydration of ethanol to produce ethylene, it is easy to generate carbon deposits and cause a decrease in activity.

[0004] The present invention develops a new method for preparing a highly stable bioethanol dehydration catalyst. Before loading the active component, a catalyst precursor modified with auxiliary nickel is first obtained by an impregnation method, and by loading a suitable amount of metal nickel, the adsorption of the precursor generating carbon deposits is promoted, and the active component used for catalyzing the dehydration of bioethanol is protected, thereby improving the stability of the catalyst. The method is simple to operate and can be applied to acid catalysis fields such as alcohol dehydration. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a method for preparing a catalyst for dehydrating bioethanol to produce bioethylene with mild reaction conditions, controllable preparation process and simple steps. The prepared catalyst has the advantages of mild reaction conditions, high activity and good stability at high space velocity, can be applied to acid-catalyzed alcohol dehydration reactions and has broad application prospects.

[0006] The technical solution is:

[0007] The method for preparing a high-stability catalyst for dehydrating bioethanol to produce bioethylene of the present invention comprises the following steps:

[0008] (1) Loading auxiliary agent: The raw salt is prepared into a solution, impregnated onto a silica carrier, and after aging, drying, calcining, and reduction, a catalyst precursor loaded with auxiliary agent is obtained; this step is a key step of the present invention, and its function is to obtain a suitable content of metallic nickel through loading, promote the adsorption of the precursor that generates carbon deposits, protect the active center used to catalyze the dehydration of ethanol, and thus improve the stability of the catalyst.

[0009] (2) Loading active components: The raw materials are prepared into a solution, and impregnated onto the catalyst precursor obtained in step 1. After aging, drying, and calcination, a high-stability catalyst for dehydrating bioethanol to produce bioethylene is obtained.

[0010] Preferably, in step (1), the carrier is silicon oxide, and the properties are: specific surface area 350±100m 2 / g, pore volume 0.8±0.4mL / g, average pore diameter 12±6nm.

[0011] Preferably, in step (1), the auxiliary agent is metallic nickel, and the content thereof is 1-5 wt %.

[0012] Preferably, in step (1), the nickel source in the raw salt is Ni(NO3)2·6H2O, and the nickel salt solution is impregnated onto the carrier by an impregnation method, aged for 10-12 hours, dried at 110-130°C for 6-12 hours, calcined at 450-550°C for 4-6 hours, and reduced in hydrogen at 400-550°C for 4-6 hours to obtain a catalyst precursor loaded with an additive.

[0013] Preferably, the active component in step (2) is one or more of silicotungstic acid, phosphotungstic acid and phosphomolybdic acid, and the content of the active component is 10-40wt%; the content of the carrier is 55-89wt%.

[0014] Preferably, in step (2), the active component solution is impregnated into the catalyst precursor by an impregnation method, aged for 10-12 hours, dried at 110-130° C. for 6-12 hours, and calcined at 250-350° C. for 4-6 hours to obtain the catalyst.

[0015] Application of a high-stability heteropolyacid catalyst in the dehydration reaction of bioethanol to bioethylene.

[0016] Preferably, a fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 220-280°C, the reaction pressure is 0.5-1.5MPa, and the mass space velocity is 1-10h in terms of ethanol. -1 .

[0017] The present invention uses common silicon oxide as a carrier, loads auxiliary agents and active components in steps to prepare a catalyst, the conditions are mild, and the process is stable and controllable. By loading a suitable amount of metal nickel, the adsorption of the precursor that generates carbon deposits is promoted, and the active components used to catalyze the dehydration of bioethanol are protected, thereby improving the stability of the catalyst. The prepared catalyst has the advantages of low reaction temperature, high activity, strong anti-carbon deposition ability, good stability at high space velocity, etc.

[0018] Beneficial technical effects

[0019] 1. The present invention prepares the bioethanol dehydration catalyst by loading the auxiliary agent and the active component step by step, with simple steps, mild conditions and controllable process. The metal center in the prepared catalyst helps to adsorb the precursor for generating carbon deposits, protects the active center for dehydration, and improves the stability in use;

[0020] 2. The catalyst has the advantages of low reaction temperature and good stability. The reaction process is simple, controllable and easy to operate, and has broad application prospects. DETAILED DESCRIPTION

[0021] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0022] The properties of the silicon oxide carrier used in the following examples are: specific surface area 285m 2 / g, pore volume 0.79mL / g, pore diameter 5.2-13.8nm.

[0023] Example 1

[0024] (1) Loading auxiliary agent: Weigh 10 g of silica carrier and add it to 10 mL of aqueous solution containing 1.53 g of Ni(NO3)2·6H2O. Ripen at room temperature for 12 h, dry at 120°C for 12 h, calcine at 500°C in air for 4 h, and reduce at 500°C in H2 atmosphere (flow rate 50 mL / min) for 3 h. XRD results show that the crystalline phase is Ni, thus obtaining a catalyst precursor loaded with auxiliary agent, in which the content of auxiliary nickel is 3 wt%.

[0025] (2) Loading active components: The catalyst precursor prepared in step (1) was added to 10 mL of 4.29 g H4SiW 12 O 40·24H2O aqueous solution, aged at room temperature for 12h, dried at 120℃ for 12h, and calcined in air at 250℃ for 4h to obtain a catalyst, denoted as catalyst 1, with the active component (H4SiW 12 O 40 ) content is 30wt%.

[0026] (3) Catalyst evaluation: The catalyst was evaluated in a fixed bed tubular reactor. The raw material was bioethanol. The reaction temperature was 240°C, the reaction pressure was 1.0 MPa, and the mass space velocity was 10 h -1 After gas-liquid separation, the products were respectively sent to gas chromatography for analysis of composition and content. The tail gas flow rate was monitored and counted by a flow meter. The conversion rate of ethanol and the selectivity of ethylene and ether were calculated based on the comprehensive reaction results of the gas-liquid phase.

[0027] Example 2: Different types of additive raw material salts - NiCl2·6H2O

[0028] Compared with Example 1, Example 2 differs in that in step (1), 10 mL of the impregnation solution contains 1.25 g of NiCl2·6H2O, and the rest of the process and conditions are exactly the same as those of Example 1; the prepared catalyst is recorded as Catalyst 2.

[0029] Example 3: Different types of additive raw material salts - NiSO4·6H2O

[0030] Compared with Example 1, Example 3 differs in that in step (1), 10 mL of the impregnation solution contains 1.38 g of NiSO4·6H2O, and the rest of the process and conditions are exactly the same as those of Example 1; the prepared catalyst is recorded as Catalyst 3.

[0031] Example 4: Different types of additive raw material salts - Ni(CH3COO)2·4H2O

[0032] Compared with Example 1, Example 4 differs in that in step (1), 10 mL of the impregnation solution contains 1.31 g of Ni(CH3COO)2·4H2O, and the rest of the process and conditions are exactly the same as those of Example 1; the prepared catalyst is recorded as Catalyst 4.

[0033] Example 5: Increased additive loading - 5wt%

[0034] Weigh 10 g of silica carrier, add it to 10 mL of aqueous solution containing 2.61 g of Ni(NO3)2·6H2O, age it at room temperature for 16 h, dry it at 130°C for 6 h, calcine it at 650°C in air for 2 h, and reduce it at 600°C in H2 atmosphere (flow rate 50 mL / min) for 2 h to obtain a catalyst precursor loaded with an additive, wherein the content of the additive nickel is 5 wt%;

[0035] The catalyst precursor was added to 10 mL of 4.29 g H4SiW 12 O 40 ·In 24H2O aqueous solution, the mixture was aged at room temperature for 12 h, dried at 120°C for 12 h, and calcined in air at 250°C for 4 h to obtain a catalyst, which was designated as Catalyst 5 and had an active component content of 30 wt%.

[0036] The catalyst evaluation conditions were the same as in Example 1.

[0037] Example 6: Reduced additive loading - 1 wt%

[0038] Weigh 10 g of silica carrier, add it to 10 mL of aqueous solution containing 0.5 g of Ni(NO3)2·6H2O, age it at room temperature for 8 h, dry it at 110°C for 12 h, calcine it at 400°C in air for 8 h, and reduce it at 300°C in H2 atmosphere (flow rate 50 mL / min) for 8 h to obtain a catalyst precursor loaded with an additive, wherein the content of the additive nickel is 1 wt%;

[0039] The catalyst precursor was added to 10 mL of 4.29 g H4SiW 12 O 40 ·In 24H2O aqueous solution, the mixture was aged at room temperature for 12 h, dried at 120°C for 12 h, and calcined in air at 250°C for 4 h to obtain a catalyst, which was designated as Catalyst 6 and had an active component content of 30 wt%.

[0040] The catalyst evaluation conditions were the same as in Example 1.

[0041] Example 7: Different types of active components - phosphotungstic acid

[0042] Example 7 is different from Example 1 in that in step (2), 10 mL of the impregnation solution contains 4.29 g H3PW 12 O 40 ·xH2O, and the rest of the process and conditions are exactly the same as those in Example 1; the prepared catalyst is recorded as Catalyst 7.

[0043] Example 8: Different types of active components - phosphomolybdic acid

[0044] Example 8 is different from Example 1 in that in step (2), 10 mL of the impregnation solution contains 4.29 g H3PMo 12 O 40 ·xH2O, and the rest of the process and conditions are exactly the same as those in Example 1; the prepared catalyst is recorded as catalyst 8.

[0045] Example 9: Active ingredient loading increased - 40 wt%

[0046] Weigh 10 g of silica carrier, add it to 10 mL of aqueous solution containing 1.53 g of Ni(NO3)2·6H2O, age it at room temperature for 12 h, dry it at 120°C for 12 h, calcine it at 500°C in air for 4 h, and reduce it at 500°C in H2 atmosphere (flow rate 50 mL / min) for 3 h to obtain a catalyst precursor loaded with an additive, wherein the content of the additive nickel is 3 wt%;

[0047] The catalyst precursor was added to 10 mL of 6.67 g H4SiW 12 O 40 ·24H2O aqueous solution, aged at room temperature for 16 h, dried at 130°C for 6 h, and calcined in air at 400°C for 2 h to obtain a catalyst, denoted as catalyst 9, with an active component content of 40 wt%.

[0048] The catalyst evaluation conditions were the same as in Example 1.

[0049] Example 10: Active ingredient loading reduction - 10 wt%

[0050] Weigh 10 g of silica carrier, add it to 10 mL of aqueous solution containing 1.53 g of Ni(NO3)2·6H2O, age it at room temperature for 12 h, dry it at 120°C for 12 h, calcine it at 500°C in air for 4 h, and reduce it at 500°C in H2 atmosphere (flow rate 50 mL / min) for 3 h to obtain a catalyst precursor loaded with an additive, wherein the content of the additive nickel is 3 wt%;

[0051] The catalyst precursor was added to 10 mL of 1.11 g H4SiW 12 O 40 ·24H2O aqueous solution, aged at room temperature for 8 h, dried at 110°C for 12 h, and calcined in air at 200°C for 8 h to obtain a catalyst, denoted as catalyst 10, with an active component content of 10 wt%.

[0052] The catalyst evaluation conditions were the same as in Example 1.

[0053] Comparative Example 1

[0054] Comparative Example 1 is different from Example 10 in that step (1) of loading the auxiliary agent on the carrier is omitted, and the remaining steps and conditions are exactly the same as those of Example 10 (loading the active component heteropoly acid on the silica carrier); the obtained catalyst is recorded as Catalyst 11. The content of the active component (heteropoly acid) in the catalyst is 10 wt%.

[0055] The following table lists the reaction evaluation results of the catalyst prepared by the method of the present invention:

[0056]

[0057] From Example 10 and Comparative Example 1, it can be seen that loading the auxiliary agent nickel is beneficial to improving the stability of ethanol dehydration to ethylene at high space velocity; from Examples 1 and 2, 3, and 4, it can be seen that nickel nitrate has the best effect among the raw salts, and there is little difference between nickel chloride, nickel sulfate, and nickel acetate; from Examples 1, 7, and 8, it can be seen that the activity and stability of silicotungstic acid are higher than those of phosphotungstic acid and phosphomolybdic acid; from Examples 1, 9, and 10, it can be seen that the catalyst activity increases with the increase in the loading amount of the active component; from Examples 1, 5, and 6, it can be seen that with the increase in the auxiliary agent content, the ethanol conversion rate and ethylene selectivity decrease slightly after 24 hours of reaction, but the stability of the catalyst increases with the increase in the auxiliary agent content after 800 hours of reaction. Considering the initial activity and stability comprehensively, Example 1 is the best.

Claims

1. A high-stability catalyst for dehydrating bioethanol to produce bioethylene, comprising an additive, an active component and a carrier, wherein the additive is metal nickel, the active component is a heteropoly acid, and the carrier is silicon oxide; the content of the additive in the catalyst is 0.5-10wt%, preferably 1-5wt%; the content of the active component is 5-50wt%, preferably 10-40wt%; the rest is the carrier; the preparation of the catalyst includes two parts: loading the additive and the active component: (1) Loading additives: nickel salt is prepared into a solution, impregnated onto a silicon oxide carrier, and then subjected to aging, drying, calcination, and hydrogen reduction to obtain a catalyst precursor loaded with additives; (2) Loading active components: The raw materials are prepared into a solution, impregnated onto the catalyst precursor obtained in step (1), and subjected to aging, drying, and calcination to obtain a high-stability catalyst for dehydration of ethanol to ethylene.

2. The method according to claim 1, characterized in that: In step (1), the carrier is common silicon oxide, and its properties are: specific surface area 350±100m 2 / g, pore volume 0.8±0.4mL / g, average pore diameter 12±6nm.

3. The method according to claim 1, characterized in that: In step (1), the auxiliary agent is metallic nickel, and the content thereof is 0.5-10 wt %, preferably 1-5 wt %.

4. The method according to claim 1, characterized in that: In step (1), the nickel salt is one or more of Ni(NO3)2·6H2O, NiCl2·6H2O, Ni(SO4)2·6H2O or Ni(CH3COO)2·4H2O; the nickel salt solution is impregnated onto the carrier by an impregnation method, left to mature for 8-16 hours (preferably 10-12 hours), dried at 110-130°C for 6-12 hours, calcined at 400-650°C (preferably 450-550°C) for 2-8 hours (preferably 4-6 hours), and reduced in hydrogen at 300-600°C (preferably 400-550°C) for 2-8 hours (preferably 4-6 hours) to obtain a catalyst precursor loaded with an auxiliary agent.

5. The method according to claim 1, characterized in that: In step (2), the active component is one or more of silicotungstic acid, phosphotungstic acid and phosphomolybdic acid.

6. The method according to claim 1, characterized in that: In step (2), the active component solution is impregnated onto the catalyst precursor by an impregnation method, left to mature for 8-16 hours (preferably 10-12 hours), dried at 110-130°C for 6-12 hours, and calcined at 200-400°C (preferably 250-350°C) for 2-8 hours (preferably 4-6 hours) to obtain a catalyst.

7. A high-stability catalyst for dehydrating bioethanol to produce bioethylene, characterized by: The catalyst used is prepared by any preparation method described in claims 1-6.

8. The method according to claim 7, characterized in that: A fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 200-350°C, preferably 220-280°C; the reaction pressure is 0.1-2MPa, preferably 0.5-1.5MPa; based on ethanol, the mass space velocity is 0.5-20h -1 , preferably 1-10h -1 .

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