Preparation and application of a high-stability catalyst for dehydration of bio-ethanol to bio-ethylene

Abstract

The present application relates to a kind of biological ethanol dehydration preparation biological ethylene high stability heteropoly acid catalyst, its preparation method includes the following steps: (1) load auxiliary agent and (2) load active component.The present application uses common silicon oxide as carrier, step-by-step load auxiliary agent and active component preparation catalyst, mild condition, process stable controllable.By loading suitable content of metal nickel, promote the precursor adsorption of carbon deposition, protect the active component for catalyzing biological ethanol dehydration, to improve the stability of catalyst.The prepared catalyst has the advantages such as low reaction temperature, high activity, strong carbon deposition resistance, good stability under high air speed.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalytic method for the dehydration of bio-ethanol to bio-ethylene, in particular to a catalytic dehydration method of bio-ethanol on an auxiliary-modified supported heteropoly acid catalyst. BACKGROUND

[0002] Ethylene is an important symbol of the level of a country's petrochemical industry. Ethylene is an important chemical raw material, which can be used to synthesize polyethylene, ethylene oxide, polyvinyl chloride, PET, ethylbenzene and other important chemical products. At present, the production of ethylene in China is mainly through the cracking of naphtha and the production of coal to methanol, with a large production scale of more than one million tons per year. The use of ethanol dehydration to produce ethylene technology can break the constraints of oil and gas resources, realize flexible production of small and medium scale high purity ethylene, and fill the market demand for small and medium scale ethylene. The raw material ethanol is widely available, which can be produced by fermentation or thermochemical conversion process from biomass, industrial waste gas, coal, solid waste, etc. Using bio-ethanol as raw material is of great significance to reduce greenhouse gas emissions and achieve the dual carbon goal. The bio-ethanol dehydration to produce ethylene technology has the advantages of simple reaction process, easy separation of reaction products and environmental friendliness, and is suitable for small-scale production, which can partially or completely replace petroleum ethylene, and has important economic value and energy strategy significance.

[0003] The development of high-efficiency catalysts is the key to the production of ethylene by dehydration of bio-ethanol. The heterogeneous catalysts for the dehydration of ethanol to produce ethylene mainly include active alumina, molecular sieve and heteropoly acid, etc. The active alumina has high mechanical strength and good selectivity, but the reaction temperature is high, the space velocity is low, the unit energy consumption is high, and the utilization rate of equipment is low. Patent CN 101244971 A reports a preparation method of a nano molecular sieve catalyst for the dehydration of bio-ethanol to produce ethylene, which has a low reaction temperature, high ethanol conversion rate and high ethylene selectivity. However, this process needs to pass in a carrier gas, the catalyst stability is poor, the preparation conditions are harsh, and the crystallinity is difficult to control, which limits its further industrial application. Patents CN 105709822 A and CN 106944139 A disclose a method for the dehydration of ethanol to produce ethylene using ammonium salt of heteropoly acid as catalyst. However, the above unmodified catalysts for the dehydration of ethanol to produce ethylene are prone to generate carbon deposition, which leads to the decrease of activity.

[0004] The present application develops a new method for preparing a high-stability bio-ethanol dehydration catalyst. Before loading the active component, the catalyst precursor is obtained by impregnation method with the aid of nickel modification, and by loading a suitable amount of metal nickel, the precursor for generating carbon deposition is adsorbed to protect the active component for catalyzing the dehydration of bio-ethanol, thereby improving the stability of the catalyst. This method is simple in operation and can be applied to the field of acid catalysis such as alcohol dehydration. SUMMARY

[0005] The present application aims to provide a preparation method of a catalyst for preparing bio-ethylene from bio-ethanol by dehydration, which has mild reaction conditions, controllable preparation process and simple steps, and has the advantages of mild reaction conditions, high activity and good stability at high air speed, and can be applied to alcohol dehydration reaction catalyzed by acid, and has wide application prospect.

[0006] The technical scheme is as follows:

[0007] The preparation method of the high-stability catalyst for preparing bio-ethylene from bio-ethanol by dehydration comprises the following steps:

[0008] (1) loading an auxiliary agent: preparing a raw salt solution, impregnating the solution into a silicon oxide carrier, and then performing aging, drying, calcination and reduction to obtain a catalyst precursor loaded with the auxiliary agent; this step is a key step of the present application, and the role of the step is to obtain a proper content of metal nickel by loading, promote the adsorption of a precursor for generating carbon deposition, protect the active center for catalyzing ethanol dehydration, and thus improve the stability of the catalyst.

[0009] (2) loading an active component: preparing a raw material solution, impregnating the solution into the catalyst precursor obtained in step 1, and then performing aging, drying and calcination to obtain the high-stability catalyst for preparing bio-ethylene from bio-ethanol by dehydration.

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

[0011] As a preferred, in step (1), the auxiliary agent is metal nickel, and the content is 1-5 wt%.

[0012] As a preferred, in step (1), the nickel source in the raw salt is Ni(NO3)2·6H2O, the nickel salt solution is impregnated into the carrier by using an impregnation method, the aging time is 10-12 h, the drying temperature is 110-130℃, the drying time is 6-12 h, the calcination temperature is 450-550℃, the calcination time is 4-6 h, the reduction temperature is 400-550℃, and the reduction time is 4-6 h, so as to obtain the catalyst precursor loaded with the auxiliary agent.

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

[0014] As a preferred, in step (2), the active component solution is impregnated into the catalyst precursor by using an impregnation method, the aging time is 10-12 h, the drying temperature is 110-130℃, the drying time is 6-12 h, the calcination temperature is 250-350℃, and the calcination time is 4-6 h, so as to obtain the catalyst.

[0015] Application of a high-stability heteropoly acid catalyst in a reaction of bio-ethanol dehydration to produce bio-ethylene.

[0016] As preferred, a fixed bed reactor is used, the raw material is bio-ethanol, the reaction temperature is 220-280 DEG C, the reaction pressure is 0.5-1.5 MPa, the mass space velocity is 1-10 h -1 .

[0017] The present application uses common silicon oxide as a carrier, and step-by-step loading of an auxiliary agent and an active component to prepare the catalyst, which has mild conditions and a stable and controllable process. By loading a suitable content of metal nickel, the adsorption of a precursor for generating accumulated carbon is promoted, and the active component for catalyzing bio-ethanol dehydration is protected, so that the stability of the catalyst is improved. The prepared catalyst has the advantages of low reaction temperature, high activity, strong anti-accumulated carbon capacity, and good stability at high space velocity.

[0018] Beneficial technical effects

[0019] 1. The bio-ethanol dehydration catalyst is prepared by step-by-step loading of an auxiliary agent and an active component, which has simple steps, mild conditions, and a controllable process. The metal center in the prepared catalyst helps to adsorb a precursor for generating accumulated carbon, protects the active center for dehydration, and improves the use stability.

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

[0021] In order to further illustrate the present application, several specific implementation cases are given below, but the present application is not limited to these examples.

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

[0023] Example 1

[0024] (1) Loading of an auxiliary agent: 10 g of a silicon oxide carrier is weighed and added to 10 mL of an aqueous solution containing 1.53 g of Ni(NO3)2·6H2O, and aged at room temperature for 12 h, dried at 120 DEG C for 12 h, calcined at 500 DEG C in air for 4 h, and reduced at 500 DEG C in H2 (flow rate 50 mL / min) for 3 h. The XRD result shows that the crystal phase is Ni, and a catalyst precursor loaded with an auxiliary agent is obtained, wherein the content of the auxiliary agent nickel is 3 wt%.

[0025] (2) Loading of an active component: the catalyst precursor prepared in step (1) is added to 10 mL of an aqueous solution containing 4.29 g of H4SiW 12 O 40• 24H2O solution, aging at room temperature for 12 h, drying at 120°C for 12 h, and calcination in air at 250°C for 4 h to obtain the catalyst, which is denoted as Catalyst 1, and the content of active component (H4SiW 12 O 40 ) is 30wt%.

[0026] (3) Catalyst evaluation: in a fixed-bed tubular reactor, the raw material is bioethanol, the reaction temperature is 240°C, the reaction pressure is 1.0 MPa, the mass space velocity is 10h -1 ; after gas-liquid separation, the composition and content of the product are analyzed by gas chromatography, the tail gas flow rate is monitored and counted by a flow rate counter, and the conversion rate of ethanol and the selectivity of ethylene and diethyl ether are calculated based on the reaction results of gas and liquid phases.

[0027] Example 2: Different types of raw material salts of the assistant—NiCl2·6H2O

[0028] Example 2 differs from Example 1 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 in Example 1; the prepared catalyst is denoted as Catalyst 2.

[0029] Example 3: Different types of raw material salts of the assistant—NiSO4·6H2O

[0030] Example 3 differs from Example 1 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 in Example 1; the prepared catalyst is denoted as Catalyst 3.

[0031] Example 4: Different types of raw material salts of the assistant—Ni(CH3COO)2·4H2O

[0032] Example 4 differs from Example 1 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 in Example 1; the prepared catalyst is denoted as Catalyst 4.

[0033] Example 5: Increased loading of the assistant—5wt%

[0034] 10 g of silica carrier is weighed and added to 10 mL of an aqueous solution containing 2.61 g of Ni(NO3)2·6H2O, aged at room temperature for 16 h, dried at 130°C for 6 h, calcined in air at 650°C for 2 h, and reduced in H2 (flow rate 50 mL / min) at 600°C for 2 h to obtain a catalyst precursor loaded with an assistant, wherein the content of the assistant nickel is 5wt%;

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

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

[0037] Example 6: Reduction of promoter loading - 1 wt%

[0038] 10 g of silica support was weighed and added to 10 mL aqueous solution containing 0.5 g Ni(NO3)2-6H2O, aged at room temperature for 8 h, dried at 110°C for 12 h, calcined at 400°C in air for 8 h, and reduced at 300°C in H2(flow rate 50 mL / min) for 8 h to obtain the promoter-loaded catalyst precursor, with a promoter nickel content of 1 wt%;

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

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

[0041] Example 7: Different active component - phosphotungstic acid

[0042] Example 7 differed from Example 1 in that in step (2), 10 mL of the impregnation solution contained 4.29 g H3PW 12 O 40 • xH2O, and the rest of the process and conditions were exactly the same as in Example 1; the catalyst obtained was labeled as Catalyst 7.

[0043] Example 8: Different active component - phosphomolybdic acid

[0044] Example 8 differed from Example 1 in that in step (2), 10 mL of the impregnation solution contained 4.29 g H3PMo 12 O 40 • xH2O, and the rest of the process and conditions were exactly the same as in Example 1; the catalyst obtained was labeled as Catalyst 8.

[0045] Example 9: Increase of active component loading - 40 wt%

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

[0047] Add the catalyst precursor to 10 mL of aqueous solution containing 6.67 g of H4SiW 12 O 40 ·24H2O, mature at room temperature for 16 h, dry at 130°C for 6 h, calcine in air at 400°C for 2 h, to obtain a catalyst, recorded as catalyst 9, the content of the active component is 40 wt%.

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

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

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

[0051] Add the catalyst precursor to 10 mL of aqueous solution containing 1.11 g of H4SiW 12 O 40 ·24H2O, mature at room temperature for 8 h, dry at 110°C for 12 h, calcine in air at 200°C for 8 h, to obtain a catalyst, recorded as catalyst 10, the content of the active component is 10 wt%.

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

[0053] Comparative Example 1

[0054] Comparative Example 1 differs from Example 10 in that step (1) of loading the support with the promoter is omitted, and the rest of the process and conditions are exactly the same as in Example 10 (loading the active component heteropoly acid on the silica support); the catalyst prepared 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 catalysts prepared by the method described in the present application

[0056]

[0057] From Example 10 and Comparative Example 1, it can be seen that the loading of the promoter nickel is beneficial to improving the stability of the dehydration of ethanol to ethylene at high space velocity; from Examples 1 and 2, 3, 4, it can be seen that the effect of nickel nitrate in the raw material salt is the best, and the effects of nickel chloride, nickel sulfate and nickel acetate are not much different; from Examples 1, 7, 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, 10, it can be seen that the activity of the catalyst increases with the increase of the loading amount of the active component; from Examples 1, 5, 6, it can be seen that with the increase of the content of the promoter, the ethanol conversion rate and the ethylene selectivity slightly decrease after 24 h of reaction, but the stability of the catalyst increases with the increase of the content of the promoter after 800 h of reaction, and considering the initial activity and stability comprehensively, Example 1 is the best.

Claims

1. A method for preparing a high-stability catalyst for dehydration of bio-ethanol to produce bio-ethylene, the catalyst comprising an auxiliary agent, an active component and a carrier, wherein the auxiliary agent is metallic nickel, the active component is a heteropoly acid, and the carrier is silicon oxide; the content of the auxiliary agent in the catalyst is 0.5-10 wt%; the content of the active component is 5-50 wt%; and the rest is the carrier; the catalyst is prepared by loading the auxiliary agent and the active component, comprising the following steps: (1) loading the auxiliary agent: preparing a solution of nickel salt, impregnating the solution onto the silicon oxide carrier, and then aging, drying, calcining and reducing by hydrogen to obtain a catalyst precursor loaded with the auxiliary agent; (2) loading the active component: preparing a solution of the active component, impregnating the solution onto the catalyst precursor obtained in step (1), and then aging, drying and calcining to obtain the high-stability catalyst for dehydration of bio-ethanol to produce bio-ethylene.

2. The method according to claim 1, wherein: in step (1), the content of the auxiliary agent in the catalyst is 1-5 wt%; and the content of the active component is 10-40 wt%.

3. The method according to claim 1, wherein: in step (1), the nickel salt is one or more than two of Ni(NO3)2·6H2O, NiCl2·6H2O, Ni(SO4)2·6H2O or Ni(CH3COO)2·4H2O; the solution of the nickel salt is impregnated onto the carrier by the impregnation method, and then placed for aging for 8-16 h, dried at 110-130 ℃ for 6-12 h, calcined at 400-650 ℃ for 2-8 h, and reduced in hydrogen at 300-600 ℃ for 2-8 h to obtain the catalyst precursor loaded with the auxiliary agent. In step (1), the support is a common silica with the following properties: specific surface area 350 ± 100 m 2 / g, pore volume 0.8 ± 0.4 mL / g, average pore diameter 12 ± 6 nm.

4. The method according to claim 1, wherein: in step (2), the active component is one or more than two of silicotungstic acid, phosphotungstic acid and phosphomolybdic acid.

5. The method according to claim 1, wherein: in step (2), the solution of the active component is impregnated onto the catalyst precursor by the impregnation method, and then placed for aging for 8-16 h, dried at 110-130 ℃ for 6-12 h, and calcined at 200-400 ℃ for 2-8 h to obtain the catalyst. The catalyst is prepared by any one of the methods described in claims 1-5.

7. The high-stability catalyst for dehydration of bio-ethanol to produce bio-ethylene according to claim 6, wherein:

8. The high-stability catalyst for dehydration of bio-ethanol to produce bio-ethylene according to claim 7, wherein: ​ ​ ​ 6. A high stability catalyst for the dehydration of bio-ethanol to produce bio-ethylene, characterized in that: ​ ​ The fixed bed reactor is used, the raw material is bioethanol, the reaction temperature is 200-350 ℃, the reaction pressure is 0.1-2 MPa, the mass space velocity of ethanol is 0.5-20 h -1 . ​ The reaction temperature is 220-280 ℃; the reaction pressure is 0.5-1.5 MPa; the mass space velocity is 1-10 h -1 .

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