Process for the dehydration of alcohols to olefins

Abstract

This invention relates to the field of alcohol dehydration for olefin preparation technology, and discloses a method for alcohol dehydration for olefin preparation. The method includes: contacting an alcohol with a dehydration catalyst in the presence of hydrogen to carry out a dehydration reaction, wherein the dehydration catalyst comprises a main component selected from at least one of zirconium oxide, silicon oxide, and alumina. The method provided by this invention can effectively reduce various side reactions caused by alcohol dehydrogenation, improve reaction selectivity, reduce the impurities and types of reaction products, significantly reduce polymers and gums generated by aldehyde or ketone condensation, significantly delay catalyst deactivation due to carbon deposition, give the catalyst a longer lifespan, and reduce both material and energy consumption of the reaction.

Description

Technical Field

[0001] This invention relates to the field of alcohol dehydration for olefin preparation technology, and more specifically, to a method for alcohol dehydration for olefin preparation. Background Technology

[0002] The main methods for preparing olefins include paraffin cracking, solvent extraction, ethylene oligomerization, Fischer-Tropsch synthesis, and alcohol dehydration. Paraffin cracking and solvent extraction methods have strict operating conditions, complex reaction processes, low product purity, and numerous byproducts, and have been gradually phased out. Ethylene oligomerization is simple, technologically mature, produces high-purity, high-quality products, and generates little waste; this method is monopolized by global oil giants. Fischer-Tropsch synthesis uses coal as a raw material, resulting in low industrialization costs, but product separation is costly and difficult. Alcohol dehydration for olefin preparation has a simple process route, mild reaction conditions, high product purity, concentrated distribution, and easy separation; the production process is relatively clean, and the distillation process has low energy consumption, making it a competitive synthetic route.

[0003] Alpha-olefins occupy an important position among olefins and have a wide range of applications. Alpha-olefins are olefins with carbon-carbon double bonds at the terminal positions, with the general molecular formula CH2=CH-R (R being an alkyl group). They are very important petrochemical raw materials and are widely used in various fields, such as as comonomers, intermediates, plasticizers, bactericides, emulsifiers, oil additives, and in the production of surfactants, plastics, and various fine organic chemicals.

[0004] Alcohol dehydration catalysts can be divided into two categories: one is redox catalysts, which have many side reactions, low selectivity for the target product, and difficulty in product separation; the other is acid-base bifunctional catalysts, in which the acidic and basic sites on the surface synergistically catalyze the reactants, exhibiting better activity, selectivity, and longer lifespan, and have unique catalytic performance in dehydration reactions.

[0005] US20180009725A1 discloses a method for producing ethylene by gas-phase dehydration of ethanol using a composite oxide as a support for a heteropolyacid catalyst. The support is composed of zirconium oxide and different transition metal oxides.

[0006] CN101940938A discloses a heteropolyacid-modified alumina ethanol dehydration catalyst and its preparation method. The catalyst comprises, by weight, the following components: a) 0.5-30 parts of heteropolyacid, and b) 70-99.5 parts of alumina. This method mainly addresses the problems of high cost and low ethylene yield in existing ethanol dehydration catalysts. However, the heteropolyacid-modified alumina ethanol dehydration catalyst is difficult to separate from the product, resulting in difficulties in catalyst recovery.

[0007] CN112275315A discloses a sulfur-modified metal-supported molecular sieve catalyst, its preparation method, and its application in the preparation of isosorbide. The sulfur-modified metal-supported molecular sieve catalyst is obtained by sequentially modifying H-type molecular sieves with metal salts and sulfur-containing compounds. This catalyst promotes the efficient dehydration reaction of sorbitol; however, the catalyst modified with sulfate ions has poor thermal stability, short service life, and is prone to carbon deposition and deactivation, and SO42-... 2- Its catalytic activity is easily lost in liquid-phase reactions, which limits its application in industrial production.

[0008] EP3233765B1 discloses a heteropolyacid catalyst supported on a mixed oxide and its application in the dehydration of ethanol to ethylene. This supported heteropolyacid catalyst comprises: i) a mixed oxide of silica and transition metal oxides as a support; or ii) a mixed oxide of zirconium oxide and different transition metal oxides as a support. Compared to conventional supported heteropolyacid catalysts, this catalyst exhibits a longer catalyst lifetime in the alcohol dehydration reaction; however, its smaller specific surface area limits its catalytic activity.

[0009] CN108745422A discloses a 1,4-butanediol dehydration catalyst with tunable surface acidity / basicity, its preparation method, and its application. In this method, the support is selected from a zirconia support, and the active component is loaded onto the zirconia support to obtain a supported catalyst. This catalyst is used for the dehydration of 1,4-butanediol to prepare 3-buten-1-ol. However, the preparation process of this catalyst is complex, the catalyst composition is complex, and the conversion rate of 1,4-butanediol and the selectivity of 3-buten-1-ol are relatively low.

[0010] From the perspective of existing alcohol dehydration technologies, the industrial application of catalytic alcohol dehydration to olefins still suffers from problems such as numerous side reactions, severe carbon buildup, and easy catalyst deactivation. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems of numerous side reactions, severe carbon buildup, and easy catalyst deactivation in existing catalytic alcohol dehydration to olefin production technologies. This invention provides a method for alcohol dehydration to olefin production. This method proposes for the first time to carry out the dehydration reaction of alcohol to olefin production under hydrogen conditions, which has fewer side reactions, significantly delays the carbon buildup and deactivation of the catalyst, and gives the catalyst a longer lifespan.

[0012] In their research on the production of olefins from alcohol dehydration, the inventors of this invention discovered that, in addition to olefins, the reaction products also include aldehydes or ketones generated from the dehydrogenation of alcohols. On the one hand, the condensation polymerization of aldehydes or ketones deactivates the dehydration catalyst; on the other hand, it increases the separation difficulty and energy consumption. Furthermore, in the process of alcohol dehydration to olefins, it is generally believed that the introduction of hydrogen will cause the olefins to hydrogenate to alkanes, thus reducing selectivity and yield. If the catalyst has a strong hydrogenation capacity, it will indeed promote the hydrogenation of olefins to alkanes. However, the inventors of this invention have found that by appropriately selecting the hydrogenation capacity, the formation of aldehydes or ketones can be suppressed without causing the olefins to hydrogenate. By using the dehydration catalyst of this invention under hydrogen-containing conditions for the alcohol dehydration reaction, side reactions can be significantly reduced and carbon deposition can be greatly slowed down.

[0013] To achieve the above objectives, the present invention provides a method for preparing olefins by dehydration of alcohol, the method comprising: contacting an alcohol with a dehydration catalyst in the presence of hydrogen to carry out a dehydration reaction, wherein the dehydration catalyst comprises a main component selected from at least one of zirconium oxide, silicon oxide and aluminum oxide.

[0014] Through the above technical solution, the method provided by the present invention can carry out alcohol dehydration reaction under hydrogen conditions, which can effectively reduce various side reactions caused by alcohol dehydrogenation, improve reaction selectivity, reduce the impurities and types of reaction products, significantly reduce polymers and gums generated by aldehyde or ketone condensation, significantly delay the carbon deposition and deactivation of catalyst, give catalyst a longer life, and reduce the material and energy consumption of the reaction. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] In this invention, "optional" means that a certain component may or may not be contained, or that a certain operation may or may not be performed.

[0017] The present invention provides a method for preparing olefins by dehydration of alcohol, the method comprising: contacting an alcohol with a dehydration catalyst in the presence of hydrogen to carry out a dehydration reaction, wherein the dehydration catalyst comprises a main component selected from at least one of zirconium oxide, silicon oxide and aluminum oxide.

[0018] In their research on the production of olefins from alcohol dehydration, the inventors of this invention observed through numerous experiments that dehydrogenation reactions occur simultaneously with alcohol dehydration, producing aldehydes or ketones. On the one hand, the condensation polymerization of aldehydes or ketones deactivates the dehydration catalyst; on the other hand, it increases the difficulty of separation and energy consumption. The inventors unexpectedly discovered that conducting the alcohol dehydration reaction under hydrogen-exposed conditions can significantly suppress the dehydrogenation reaction, greatly reduce carbon deposition, and improve catalyst stability. Furthermore, existing technologies have not yet documented dehydration reactions for the production of olefins from alcohols under hydrogen-exposed conditions.

[0019] According to some embodiments of the present invention, preferably, the conditions for the dehydration reaction include: a reaction temperature of 200-360°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, or any value within the range formed by any two of the above values, preferably 240-320°C, more preferably 260-310°C; and / or a reaction pressure of 0.1-0.3 MPa, for example, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, or any value within the range formed by any two of the above values, preferably 0.1-0.2 MPa; and / or a liquid hourly space velocity (LHSV) of the alcohol of 0.05-1.2 h⁻¹. -1 For example, it can be 0.05h. -1 0.1h -1 0.2h -1 0.3h -1 0.4h -1 0.5h -1 0.6h -1 0.7h -1 0.8h -1 0.9h -1 1h -1 1.1h -1 1.2h -1 Or any value within the range formed by any two of the above values, preferably 0.1-1h. -1 The above-described preferred embodiments are beneficial for improving the selectivity of olefins and reducing the formation of aldehydes or ketones, thereby reducing carbon deposition. Specifically, excessively high reaction temperatures can easily lead to the formation of aldehydes or ketones or trigger olefin polymerization; conversely, excessively low liquid hourly space velocity of alcohols results in a longer residence time of the material in the catalyst bed, which can easily trigger olefin polymerization.

[0020] According to some embodiments of the present invention, preferably, the molar ratio of the alcohol to hydrogen feed is 0.1-6:1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 6:1, or any value within the range formed by any two of the above values, preferably 0.3-3:1. Using the above preferred embodiments is beneficial for improving the selectivity of olefins. An appropriate amount of hydrogen can not only inhibit the formation of aldehydes or ketones and the hydrogenation of olefins, but also promote material diffusion, avoiding the polymerization of unsaturated compounds to form heavy components and carbon deposits.

[0021] According to some embodiments of the present invention, the dehydration of alcohols can generally produce alkenes, such as primary alcohols, secondary alcohols, and tertiary alcohols. The methods described can be used for various alcohol dehydration reactions to produce alkenes, and all can achieve the inventive objectives of the present invention to a certain extent.

[0022] According to some embodiments of the present invention, preferably, the alcohol is selected from alcohols having 2-18 carbon atoms, for example, alcohols having 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms, or any value within the range formed by any two of the above values. From the perspective of olefin applications, primary alcohols having 2-18 carbon atoms and / or secondary alcohols having 3-18 carbon atoms are preferred; more preferably, the hydroxyl group of the secondary alcohol is located on the second carbon atom of the carbon chain.

[0023] According to some embodiments of the present invention, preferably, the alcohol is selected from at least one of ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, 2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol, 2-octanol, 4-methyl-2-pentanol, 2-ethyl-1-hexanol, 2-propyl-1-heptanol, and 1,4-butanediol.

[0024] According to some embodiments of the present invention, preferably, the olefin is an α-olefin.

[0025] According to some embodiments of the present invention, when the method is used for the dehydration reaction of secondary alcohols in which the hydroxyl group is located on the second carbon atom of the carbon chain, the dehydration of these secondary alcohols can generate α-olefins and β-olefins, and at the same time, they can also be dehydrogenated to generate the corresponding ketones. The specific type of product is related to the catalyst. Therefore, to improve the selectivity of α-olefins, it is not only related to the process conditions but also to the catalyst.

[0026] According to some embodiments of the present invention, the dehydration catalyst comprises a main component selected from at least one of zirconium oxide, silicon oxide, and aluminum oxide.

[0027] According to some embodiments of the present invention, in order to improve the selectivity of secondary alcohols to α-olefins, preferably, the dehydration catalyst further includes an alkaline earth metal oxide; more preferably, the alkaline earth metal oxide is selected from at least one of magnesium oxide, calcium oxide, strontium oxide and barium oxide.

[0028] According to some embodiments of the present invention, preferably, the content of the alkaline earth metal oxide is 0.1-10 parts by weight relative to 100 parts by weight of the main component, for example, it can be 0.1 parts by weight, 0.2 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, or any value within the range formed by any two of the above values, preferably 0.2-8 parts by weight.

[0029] According to some embodiments of the present invention, preferably, the dehydration catalyst further includes metallic cobalt. Typically, existing dehydration catalysts all use oxides, and catalysts using metallic components, especially metallic components with hydrogenation capabilities, are not commonly found. The above-described preferred embodiments enable the dehydration catalyst to possess a certain selective hydrogenation capability to suppress the formation of aldehydes or ketones, while preventing the hydrogenation of olefins. Experiments show that metallic cobalt has a higher selectivity for carbonyl hydrogenation than for carbon-carbon double bond hydrogenation, while metallic nickel or copper have the opposite hydrogenation selectivity; therefore, metallic cobalt is chosen here. More preferably, the dehydration catalyst does not include nickel and copper.

[0030] According to some embodiments of the present invention, preferably, the cobalt content relative to 100 parts by weight of the main component is 0.01-0.035 parts by weight, for example, 0.01 parts by weight, 0.015 parts by weight, 0.02 parts by weight, 0.025 parts by weight, 0.03 parts by weight, 0.035 parts by weight, or any value within the range formed by any two of the above values, preferably 0.015-0.035 parts by weight. Using the above preferred embodiments is beneficial for further suppressing the formation of aldehydes or ketones, preventing the formation of polymers caused by aldol condensation, and avoiding olefin hydrogenation. If the content of metallic cobalt is too low, the hydrogenation capacity is too weak; if the content is too high, the hydrogenation capacity is too strong, leading to olefin hydrogenation.

[0031] According to some embodiments of the present invention, in order to further improve the performance of the catalyst, preferably, the dehydration catalyst further includes a modifier; more preferably, the modifier is selected from at least one of lanthanum oxide, potassium oxide, cerium oxide and zinc oxide.

[0032] According to some embodiments of the present invention, preferably, the content of the modifier is 0.1-6 parts by weight relative to 100 parts by weight of the main component, for example, it can be 0.1 parts by weight, 0.2 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, or any value in the range formed by any two of the above values, preferably 0.2-4 parts by weight.

[0033] According to some embodiments of the present invention, preferably, the dehydration catalyst comprises an alkaline earth metal oxide and a modifier, such that acidic and basic sites coexist on the surface of the catalyst. In the catalytic dehydration reaction of alcohols, the acidic and basic sites can play a synergistic role. On the one hand, the simultaneous presence of the alkaline earth metal oxide and the modifier can improve the basicity of the dehydration catalyst while better maintaining the number of acidic sites on the surface of the main component, thereby generating more acid-base synergistic active centers on the catalyst surface, which is conducive to the formation of α-olefins and inhibits the formation of β-olefins, thereby improving the selectivity of α-olefins. On the other hand, controlling the acidic and basic groups on the surface of the dehydration catalyst within a certain range can improve the adsorption-desorption performance of the catalyst, thereby promoting the diffusion of the reaction system, accelerating the reaction rate, reducing carbon deposition, and mitigating pore blockage.

[0034] According to a preferred embodiment of the present invention, the dehydration catalyst comprises a main component, an alkaline earth metal oxide, and metallic cobalt; wherein the main component is selected from at least one of zirconium oxide, silicon oxide, and aluminum oxide; the alkaline earth metal oxide is selected from at least one of magnesium oxide, calcium oxide, strontium oxide, and barium oxide; the content of the alkaline earth metal oxide is 0.1-10 parts by weight relative to 100 parts by weight of the main component; and the content of cobalt is 0.01-0.035 parts by weight. The above preferred embodiment is advantageous for suppressing the formation of aldehydes or ketones, preventing the formation of polymers caused by aldol condensation, and avoiding olefin hydrogenation.

[0035] According to a preferred embodiment of the present invention, the dehydration catalyst comprises a main component, an alkaline earth metal oxide, metallic cobalt, and a modifier; wherein the main component is selected from at least one of zirconium oxide, silicon oxide, and aluminum oxide; the alkaline earth metal oxide is selected from at least one of magnesium oxide, calcium oxide, strontium oxide, and barium oxide; the modifier is selected from at least one of lanthanum oxide, potassium oxide, cerium oxide, and zinc oxide; relative to 100 parts by weight of the main component, the content of the alkaline earth metal oxide is 0.1-10 parts by weight; the content of cobalt is 0.01-0.035 parts by weight; and the content of the modifier is 0.1-6 parts by weight. Using the above preferred embodiment is beneficial for generating more α-olefins and further reducing carbon deposition.

[0036] According to some embodiments of the present invention, in order to further optimize the selectivity and service life of the dehydration catalyst for α-olefins, preferably, the ammonia adsorption capacity of the dehydration catalyst is 0.15-0.4 mmol·g. -1 Preferably, it is 0.18-0.28 mmol·g -1 .

[0037] According to some embodiments of the present invention, in order to further optimize the selectivity and lifespan of the dehydration catalyst for α-olefins, preferably, the carbon dioxide adsorption capacity of the dehydration catalyst is 0.16-0.4 mmol·g. -1 Preferably, it is 0.18-0.35 mmol·g -1 .

[0038] According to some embodiments of the present invention, in order to further improve the catalytic performance of the dehydration catalyst, preferably, the specific surface area of ​​the dehydration catalyst is 40-150 m². 2 ·g -1 Preferably 50-130m 2 ·g -1 ; and / or, the pore volume of the dehydration catalyst is 0.05-0.2 mL·g. -1 Preferably, it is 0.1-0.2 mL·g -1 .

[0039] According to some embodiments of the present invention, there are no particular limitations on the introduction method of the alkaline earth metal oxide, metallic cobalt, and modifier. The alkaline earth metal oxide, metallic cobalt, and modifier can be loaded on the main component or dispersed in the main component. In order to better exert the role of the alkaline earth metal oxide, metallic cobalt, and modifier, and improve the stability and selectivity of the catalyst, preferably, at least one of the alkaline earth metal oxide, metallic cobalt, and modifier is introduced during the preparation process of the main component. The preparation process generally refers to the process of precipitation of the main component matrix to generate precipitate products, such as the process of synthesizing basic zirconium carbonate using zirconium oxynitrate as a raw material, and the process of synthesizing boehmite (i.e., hydrated alumina, hydrated aluminum hydroxide) from aluminum nitrate using carbon dioxide, etc.

[0040] According to some embodiments of the present invention, the dehydration catalyst can be prepared by existing methods that can obtain ammonia adsorption and carbon dioxide adsorption amounts that meet the above-mentioned ranges, and obtaining a dehydration catalyst with ammonia adsorption and carbon dioxide adsorption amounts that meet the above-mentioned ranges is something that can be done by those skilled in the art.

[0041] According to some embodiments of the present invention, preferably, the preparation method of the dehydration catalyst includes: providing a solution containing a main component matrix in the presence of a solvent, and precipitating the mixed solution with a precipitant to obtain a precipitated product; then calcining the precipitated product; wherein the main component matrix is ​​selected from at least one of a zirconium source, a silicon source, and an aluminum source. In the preparation method, those skilled in the art will understand that: if the raw material providing the main component matrix already contains the required amount of alkaline earth metal element, cobalt element, and modifier metal element, then only this raw material needs to be used for molding; if the raw material providing the main component matrix does not contain alkaline earth metal element, cobalt element, and modifier metal element, or the content of the elements is low (insufficient), then additional alkaline earth metal element, cobalt element, and modifier metal element can be introduced.

[0042] According to some embodiments of the present invention, preferably, the zirconium source is selected from at least one of zirconium dichloride, zirconium nitrate, zirconium oxynitrate, and zirconium oxysulfate.

[0043] According to some embodiments of the present invention, preferably, the silicon source is selected from tetraethyl orthosilicate and / or silica sol.

[0044] According to some embodiments of the present invention, preferably, the aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum sulfate, and aluminum isopropoxide.

[0045] According to some embodiments of the present invention, preferably, the precipitant is selected from at least one of carbon dioxide, nitric acid, ammonia, urea, sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate. Wherein, when the precipitant is carbon dioxide, it is preferably provided in the form of a mixed gas; more preferably, the concentration of carbon dioxide in the mixed gas is 20-30 mol%. When the precipitant is selected from at least one of nitric acid, ammonia, urea, sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate, it can be provided in the form of an aqueous solution; more preferably, the concentration of the precipitant in the aqueous solution is 20-30 wt%. When synthesizing the precursor of the main component, the final pH value of the synthesis can be controlled within a normal range; for example, when synthesizing the alumina precursor pseudoboehmite, the pH value is controlled at 10-10.5.

[0046] According to some embodiments of the present invention, the solution contains a main component parent; the solvent in the solution is selected from water and / or ethanol, preferably water.

[0047] According to some embodiments of the present invention, preferably, the solution further contains an alkaline earth metal matrix.

[0048] According to some embodiments of the present invention, preferably, the alkaline earth metal precursor is selected from alkaline earth metal salts, more preferably from at least one of alkaline earth metal nitrates, alkaline earth metal formates, alkaline earth metal oxalates, and alkaline earth metal lactates; more preferably, the alkaline earth metal salt is selected from at least one of magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate. Further preferably, the alkaline earth metal precursor can be provided in the form of an alkaline earth metal salt solution. The solvent in the solution is selected from water and / or ethanol, preferably water.

[0049] According to some embodiments of the present invention, preferably, the solution further contains a cobalt source. The range of types of cobalt source that can be selected is wide, and there are no particular limitations. For example, the cobalt source can be a conventional soluble cobalt salt in the art, preferably selected from at least one of cobalt nitrate, cobalt acetate, cobalt formate, basic cobalt carbonate, cobalt citrate, cobalt chloride, cobalt sulfate, and cobalt phosphate.

[0050] According to some embodiments of the present invention, preferably, the solution further contains a modifier matrix.

[0051] According to some embodiments of the present invention, preferably, the modifier matrix is ​​selected from at least one of lanthanum nitrate, potassium hydroxide, potassium nitrate, potassium carbonate, cerium nitrate, and zinc nitrate. More preferably, the modifier matrix can be provided in the form of a metal salt solution. The solvent in the solution is selected from water and / or ethanol, preferably water.

[0052] According to some embodiments of the present invention, there is no particular limitation on the order of addition of the alkaline earth metal matrix, the cobalt source and the modifier matrix. The alkaline earth metal matrix, the cobalt source and the modifier matrix can be mixed and then added to the system containing the main component matrix, or the alkaline earth metal matrix, the cobalt source and the modifier matrix can be added separately to the system containing the main component matrix.

[0053] According to some embodiments of the present invention, preferably, the precipitation is carried out under stirring conditions. Preferably, the precipitation temperature is 5-80°C, for example, it can be 5°C, 8°C, 10°C, 12°C, 15°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, or any value within the range formed by any two of the above values.

[0054] According to some embodiments of the present invention, preferably, after precipitation, an aging step is further included to obtain the precipitated product. The aging generally refers to the process of continuing to stir for a period of time at a temperature slightly higher than the precipitation temperature (e.g., 5-20°C higher than the precipitation temperature) or keeping it at a constant temperature for a period of time.

[0055] According to some embodiments of the present invention, preferably, the aging conditions include: a temperature of 30-90°C, preferably 50-90°C; and a time of 10-120 min, preferably 20-120 min.

[0056] According to some embodiments of the present invention, preferably, the method further includes the steps of washing and drying the precipitated product. The washing is generally done by washing the precipitated product with deionized water until it is neutral. The drying time can be reasonably selected according to the drying temperature, the amount of material and the type of drying equipment. Under preferred conditions, the drying is carried out at 70-150°C for 2-20 hours.

[0057] According to some embodiments of the present invention, preferably, the method further includes a step of shaping the dried product. The shaping can be performed using conventional methods such as ball rolling, kneading, or extrusion to process the dried product into a certain shape, such as a strip or a sphere.

[0058] According to some embodiments of the present invention, the calcination generally refers to the process of removing water of crystallization at high temperature, often accompanied by crystal transformation and decomposition to generate oxides. Preferably, the calcination conditions include: a temperature of 400-800℃, more preferably 450-650℃; a time of 1-20h, more preferably 2-10h; and a heating rate of 1-5℃ / min, more preferably 1.5-5℃ / min.

[0059] According to some embodiments of the present invention, preferably, the method further includes heat-treating the calcined product in a reducing atmosphere. The heat treatment is used to at least partially reduce the cobalt oxide in the calcined product to metallic cobalt.

[0060] According to some embodiments of the present invention, preferably, the reducing atmosphere is provided by a reducing gas containing hydrogen and optionally an inert gas (e.g., nitrogen and / or argon); more preferably, the reducing gas contains 10-30 vol% hydrogen.

[0061] According to some embodiments of the present invention, during the heat treatment, the temperature is gradually increased, and the temperature increase should not be too rapid, for example, the heating rate should not exceed 20°C / hour. The heat treatment time can be determined by monitoring the production of H2O in the reduction system; that is, the heat treatment ends when the reduction system no longer produces new H2O. Those skilled in the art can select the appropriate heat treatment time accordingly. Preferably, the heat treatment temperature is 300-450°C, more preferably 350-440°C; and the time is 1-24 hours, more preferably 2-8 hours.

[0062] According to a preferred embodiment of the present invention, the method is particularly suitable for the dehydration of methyl isobutyl methanol (MIBC) to prepare 4-methyl-1-pentene, which has higher selectivity for the target product and significantly delays the deactivation of the catalyst by carbon deposition, thus giving the catalyst a longer service life.

[0063] In this invention, atmospheric pressure refers to one standard atmosphere.

[0064] In this invention, all pressures mentioned are absolute pressures.

[0065] The present invention will be described in detail below through embodiments.

[0066] In the following examples, the specific surface area and pore volume of the catalyst were measured by nitrogen adsorption-desorption (BET) method. Test conditions: experimental gas: N2 (purity 99.999%); degassing conditions: 10℃·min -1 Heat to 350℃ and evacuate for 4 hours; Instrument name: Automatic Micropore & Chemisorption Analyzer; Instrument model: ASAP 2420, MICROMERITICS, USA.

[0067] The acidic sites (ammonia adsorption capacity) of the catalyst were obtained by NH3-TPD testing. The testing method is as follows: approximately 0.1 g of sample was accurately weighed and placed in a sample tube, and the sample was heated at 10 °C / min under He purging conditions. -1 The temperature was raised to 600℃ and held for 1 hour. The temperature was then lowered to 120℃, and the gas was changed to a 10% NH3-He mixture for adsorption for 60 minutes. The mixture was then purged with He gas for 1 hour. After the baseline stabilized, counting began at 10℃·min. -1 The temperature was raised to 600℃ and maintained for 30 minutes. Recording was then stopped to complete the experiment. The peak area was integrated to calculate the amount of NH3 desorbed (acidic sites of the catalyst). Test instrument: Automated Catalyst Characterization System, model: Autochem 2920, product of Micrometeoroids, USA.

[0068] The basicity sites (CO2 adsorption capacity) of the catalyst were determined using CO2-TPD. The test conditions were as follows: approximately 0.1 g of sample was accurately weighed and placed in a sample tube, and the sample was adsorbed at 10 °C / min under He purging conditions. -1 The temperature was raised to 600℃ and held for 1 hour. The temperature was then lowered to 120℃, and the gas was changed to a 10% CO2-He mixture for adsorption for 60 minutes. The mixture was then purged with He gas for 1 hour. After the baseline stabilized, counting began at 10℃·min. -1The temperature was raised to 600℃ and maintained for 30 minutes. Recording was then stopped to complete the experiment. The CO2 desorption capacity (the basic sites of the catalyst) was calculated by integrating the peak area. Test instrument: Automated Catalyst Characterization System; Instrument model: Autochem 2920, a product of Micrometeoroids, USA.

[0069] The elemental composition of the main component and the catalyst was analyzed using inductively coupled plasma atomic emission spectrometry.

[0070] The amount of carbon deposited on the catalyst was determined using the O2-TPO test. The test conditions were as follows: 0.2 g of sample was accurately weighed, and argon gas at a flow rate of 40 mL / min was used as the carrier gas. The sample was pretreated at 150 °C for 60 min, then cooled to 100 °C. A mixture of oxygen and argon gas (oxygen volume fraction 20%) at a flow rate of 40 mL / min was used as the analytical gas, and the temperature was programmed to 900 °C at a rate of 10 °C / min for a temperature-programmed oxidation process. Signals from CO2, CO, and other gases were detected during the temperature-programmed oxidation process. The testing instrument was a fully automated temperature-programmed chemisorption analyzer; model: AutoChemⅡ2920, a product of Micromeritics, USA.

[0071] Preparation Examples 1-6 illustrate the dehydration catalyst and its preparation method of the present invention.

[0072] Preparation Example 1

[0073] 500g of zirconium oxynitrate was dissolved in 3L of deionized water to prepare a solution. Under stirring in a 50℃ water bath, 20wt% ammonia solution was added dropwise until the pH reached 10.0. The resulting mixture was then allowed to stand at 60℃ for 2.0h, followed by centrifugation to obtain the precipitate. The precipitate was then washed with deionized water until the pH reached 6.8. The filter cake was dried at 120℃ for 2h, and the dried product was then heated in a muffle furnace at 5℃·min⁻¹. -1 The heating rate was increased to 550℃, and the catalyst was calcined at this temperature for 2 hours to obtain dehydration catalyst C-1. The test results are shown in Table 1.

[0074] Preparation Example 2

[0075] Weigh 400g of sodium aluminate, 9.5g of calcium nitrate tetrahydrate, and 0.2g of cobalt nitrate hexahydrate and dissolve them in 3L of deionized water to prepare a mixed solution. Under stirring conditions in a 12℃ water bath, introduce carbon dioxide gas (i.e., a mixture of CO2 and N2 containing 25 mol% CO2) into the mixed solution to adjust the pH to 10.5. After stopping the introduction of carbon dioxide gas, continue to maintain this state for 20 minutes. Then filter the resulting precipitate system to obtain the precipitate product. Wash the precipitate product with deionized water until pH = 7.0, dry it at 80℃ for 8 hours, and then dry it at 120℃ for 4 hours. Shape the dried powder using a kneader and extruder, and place it in a muffle furnace at 5℃·min⁻¹. -1 The temperature was increased to 650℃ and calcined at this temperature for 3 hours. Then, it was reduced with hydrogen at 440℃ for 2 hours to obtain the dehydration catalyst C-2. The test results are shown in Table 1.

[0076] Preparation Example 3

[0077] Weigh out 375g of zirconium oxynitrate, 9.5g of calcium nitrate tetrahydrate, and 0.1g of cobalt nitrate, and dissolve them in 3L of deionized water to prepare a mixed solution. Under stirring conditions in a 60℃ water bath, add ammonia solution (25wt%) dropwise to the mixed solution to adjust the pH to 7.2, and continue this process for 30 minutes. Centrifuge to obtain the precipitate. Wash the precipitate with deionized water until the pH reaches 6.8, and dry the filter cake at 120℃ for 3 hours. Finally, heat the dried product in a muffle furnace at 2℃·min⁻¹. -1 The temperature was increased to 550℃ and calcined at this temperature for 4 hours. Then, it was reduced with hydrogen at 400℃ for 3 hours to obtain the dehydration catalyst C-3. The test results are shown in Table 1.

[0078] Preparation Example 4

[0079] Weigh 800g of zirconium oxynitrate, 40g of calcium nitrate tetrahydrate, and 0.3g of cobalt nitrate and dissolve them in 6L of deionized water to prepare a mixed solution. Under stirring in a 60℃ water bath, add sodium carbonate solution (25wt%) dropwise to the mixed solution to adjust the pH to 7.0, and continue this process for 40 minutes. Centrifuge to obtain the precipitate. Wash the precipitate with deionized water until the pH reaches 7.0, and dry the filter cake at 120℃ for 3 hours. Finally, heat the dried product in a muffle furnace at 1.5℃·min⁻¹. -1 The temperature was increased to 580℃ and calcined at this temperature for 4 hours. Then, it was reduced with hydrogen at 420℃ for 3 hours to obtain the dehydration catalyst C-4. The test results are shown in Table 1.

[0080] Preparation Example 5

[0081] Weigh out 860g of zirconium oxynitrate, 60g of calcium nitrate tetrahydrate, 0.4g of cobalt nitrate, and 18.3g of lanthanum nitrate hexahydrate, and dissolve them in 6L of deionized water to prepare a mixed solution. Under stirring conditions in a 60℃ water bath, add sodium carbonate solution (25wt%) dropwise to the mixed solution to adjust the pH to 7.0, and continue this process for 40 minutes. Centrifuge to obtain the precipitate. Wash the precipitate with deionized water until the pH reaches 7.0, and dry the filter cake at 120℃ for 3 hours. Finally, heat the dried product in a muffle furnace at 1.5℃·min⁻¹. -1 The temperature was increased to 580℃ and calcined at this temperature for 4 hours. Then, it was reduced at 420℃ for 3 hours with a mixture of hydrogen and nitrogen containing 20 vol% hydrogen to obtain the dehydration catalyst C-5. The test results are shown in Table 1.

[0082] Preparation Example 6

[0083] Weigh out 800g of zirconium oxynitrate, 6g of calcium nitrate tetrahydrate, 0.2g of cobalt nitrate, and 5.67g of lanthanum nitrate hexahydrate, and dissolve them in 6L of deionized water to prepare a mixed solution. Under stirring in a 60℃ water bath, add sodium carbonate solution (25wt%) dropwise to the mixed solution to adjust the pH to 7.0, and continue this process for 40 minutes. Centrifuge to obtain the precipitate. Wash the precipitate with deionized water until the pH reaches 7.0, and dry the filter cake at 120℃ for 3 hours. Finally, heat the dried product in a muffle furnace at 1.5℃·min⁻¹. -1 The temperature was increased to 580℃ and calcined at this temperature for 4 hours. Then, it was reduced at 420℃ for 3 hours with a mixture of hydrogen and nitrogen containing 20 vol% hydrogen to obtain the dehydration catalyst C-6. The test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] Note: * Alkaline earth refers to alkaline earth metal oxides

[0088] Examples 1-14 illustrate the method for preparing olefins by dehydration of alcohols according to the present invention, specifically 4-methyl-1-pentene is prepared by dehydration of methyl isobutyl methanol (4-methyl-2-pentanol, abbreviated as MIBC) as raw material.

[0089] Examples 1-6

[0090] 50 mL of each of the dehydration catalysts C-1 to C-6 prepared in Examples 1-6 were measured and placed in a fixed-bed reactor. The reactor was preheated with nitrogen at 310 °C for 1 h. Then, methyl isobutyl methanol (MIBC) and hydrogen were metered and fed into the top of the reactor using a metering pump for the dehydration reaction. The liquid hourly space velocity (LHSV) of MIBC was 0.25 h⁻¹. -1 The molar ratio of MIBC to hydrogen was 3, the reaction temperature was 270℃, and the reaction pressure was atmospheric pressure. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0091] Example 7

[0092] The method is the same as in Example 5, except that the liquid hourly space velocity (LHSV) of methyl isobutyl methanol (MIBC) is 0.5 h⁻¹. -1 The molar ratio of MIBC to hydrogen was 1, the reaction temperature was 280℃, and the reaction pressure was 0.15MPa. All other parameters were the same as in Example 5. When the reaction was stable (i.e., after 100h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0093] Example 8

[0094] The method is the same as in Example 5, except that the liquid hourly space velocity (LHSV) of methyl isobutyl methanol (MIBC) is 1 h⁻¹. -1 The molar ratio of MIBC to hydrogen was 0.3, the reaction temperature was 310℃, and the reaction pressure was 0.2MPa. All other parameters were the same as in Example 5. When the reaction was stable (i.e., after 100h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0095] Example 9

[0096] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 0.3, and all other parameters were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0097] Example 10

[0098] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 1.5, and all other aspects were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0099] Example 11

[0100] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 2.2, and all other parameters were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0101] Example 12

[0102] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 4.5, and all other parameters were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0103] Example 13

[0104] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 6, and all other aspects were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0105] Example 14

[0106] The method of Example 5 was followed, except that the molar ratio of MIBC to hydrogen was 0.1, and all other aspects were the same as in Example 5. When the reaction was stable (i.e., after 100 h of reaction), the reaction solution was sampled and analyzed. The analysis results are listed in Table 2.

[0107] The sampling and analysis method is gas chromatography, and calibration is performed by using a correction factor to prepare standard samples;

[0108] The conversion rate and selectivity are calculated based on the molar content of each component in the reaction solution (4-methyl-1-pentene is abbreviated as 4MP1, 4-methyl-2-pentene as 4MP2, and 4-methyl-2-pentanone as MIBK). The amount of carbon deposit is not considered when calculating the conversion rate and selectivity, and the selectivity of the oligomer is the balance.

[0109] MIBC conversion rate = 100% - n1 / [(n1 + n2 + n3 + n4) + 2 × n5] × 100%

[0110] 4MP1 selectivity = n2 / [(n2+n3+n4)+2×n5]×100%

[0111] 4MP2 selectivity = n3 / [(n2+n3+n4)+2×n5]×100%

[0112] MIBK selectivity = n4 / [(n2 + n3 + n4) + 2 × n5] × 100%

[0113] Wherein, n1 is the molar content of MIBC in the reaction solution; n2 is the molar content of 4MP1 in the reaction solution; n3 is the molar content of 4MP2 in the reaction solution; n4 is the molar content of MIBK in the reaction solution; and n5 is the molar content of oligomers (calculated as dimers of 4-methylpentene) in the reaction solution.

[0114] Comparative Examples 1-3

[0115] The methods of Examples 1-3 were followed respectively, except that hydrogen gas was not introduced during the dehydration reaction; otherwise, they were the same as in Examples 1-3. Samples of the reaction solution were taken for analysis, and the results are listed in Table 2.

[0116] Table 2

[0117]

[0118]

[0119] Note: ** Carbon deposits refer to the amount of carbon deposits after 600 hours of continuous reaction.

[0120] The results above show that both the examples and the comparative examples reacted continuously for 600 hours. The amount of carbon deposit in Examples 1-3 was less than 1.2 wt%, while the amount of carbon deposit in Comparative Examples 1-3 was 4.5 wt%, 4.3 wt%, and 3.8 wt%, respectively. This indicates that the method provided by the present invention for the dehydration of alcohols to prepare olefins has higher selectivity for the target product and significantly delays the deactivation of the catalyst due to carbon deposition, resulting in a longer catalyst lifespan.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the dehydration of an alcohol to produce an olefin, characterized in that, The method includes: in the presence of hydrogen, contacting an alcohol with a dehydration catalyst to carry out a dehydration reaction, wherein the dehydration catalyst includes a main component selected from zirconium oxide; The dehydration catalyst also includes alkaline earth metal oxides and metallic cobalt; The cobalt content is 0.01-0.035 parts by weight relative to 100 parts by weight of the main component; The content of the alkaline earth metal oxide is 0.1-10 parts by weight relative to 100 parts by weight of the main component; The alcohol is selected from primary alcohols having 2-18 carbon atoms and / or secondary alcohols having 3-18 carbon atoms; The hydroxyl group of the secondary alcohol is located on the second carbon atom of the carbon chain; The olefin is an α-olefin.

2. The method of claim 1, wherein, The conditions of the dehydration reaction include: the reaction temperature is 200-360℃, the reaction pressure is 0.1-0.3MPa, the liquid phase volume space velocity of the alcohol is 0.05-1.2 h -1 .

3. The method according to claim 2, wherein, The conditions of the dehydration reaction include: the reaction temperature is 240-320℃, the reaction pressure is 0.1-0.2MPa, the liquid phase volume space velocity of the alcohol is 0.1-1 h -1 .

4. The method of any of claims 1-3, wherein, The dehydration reaction is carried out at a temperature of 260-310℃.

5. The method of any of claims 1-3, wherein, The molar ratio of alcohol to hydrogen in the feed is 0.1-6:

1.

6. The method according to claim 5, wherein, The molar ratio of alcohol to hydrogen in the feed is 0.3-3:

1.

7. The method of claim 1, wherein, The alcohol is selected from at least one of ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, 2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol, 2-octanol, 4-methyl-2-pentanol, 2-ethyl-1-hexanol, 2-propyl-1-heptanol, and 1,4-butanediol.

8. The method of claim 1, wherein, The alkaline earth metal oxide is selected from at least one of magnesium oxide, calcium oxide, strontium oxide, and barium oxide.

9. The method of claim 8, wherein, The content of the alkaline earth metal oxide is 0.2-8 parts by weight relative to 100 parts by weight of the main component.

10. The method of claim 1, wherein, The cobalt content is 0.015-0.035 parts by weight relative to 100 parts by weight of the main component.

11. The method according to claim 1, wherein, The dehydration catalyst also includes a modifier.

12. The method of claim 11, wherein, The modifier is selected from lanthanum oxide and cerium oxide.

13. The method of claim 12, wherein, The content of the modifier is 0.1-6 parts by weight relative to 100 parts by weight of the main component.

14. The method of claim 13, wherein, The content of the modifier is 0.2-4 parts by weight relative to 100 parts by weight of the main component.

15. The method of any of claims 8-14, wherein, At least one of alkaline earth metal oxides, metallic cobalt, and modifiers is introduced during the preparation of the main component.

16. The method of claim 1, wherein, The ammonia adsorption capacity of the dehydration catalyst is 0.15-0.4 mmol. g -1 The carbon dioxide adsorption capacity of the dehydration catalyst is 0.16-0.4 mmol. g -1 .

17. The method of claim 16, wherein, The ammonia adsorption capacity of the dehydration catalyst is 0.18-0.28 mmol. g -1 The carbon dioxide adsorption capacity of the dehydration catalyst is 0.18-0.35 mmol. g -1 .

18. The method of claim 1, wherein, The specific surface area of the dehydration catalyst is 40-150 m 2 g -1 The pore volume of the dehydration catalyst is 0.05-0.2 mL g -1 .

19. The method of claim 18, wherein, The specific surface area of ​​the dehydration catalyst is 50-130 m². 2 g -1 The dehydration catalyst has a pore volume of 0.1-0.2 mL. g -1 .

20. The method of claim 1, wherein, The method for preparing the dehydration catalyst includes: providing a solution containing a main component matrix, and precipitating the solution with a precipitant to obtain a precipitated product; then calcining the precipitated product; wherein the solution also contains an alkaline earth metal matrix, a cobalt source, and a modifier matrix, wherein the main component matrix is ​​selected from a zirconium source; The zirconium source is selected from at least one of zirconium oxychloride, zirconium nitrate, zirconium oxynitrate, and zirconium oxysulfate; The method further includes heat-treating the calcined product in a reducing atmosphere; The reducing atmosphere is provided by a reducing gas containing hydrogen and optionally an inert gas.

21. The method of claim 20, wherein, The precipitant is selected from at least one of ammonia, urea, sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

22. The method of claim 20, wherein, The alkaline earth metal parent material is selected from alkaline earth metal salts.

23. The method of claim 22, wherein, The alkaline earth metal salt is selected from at least one of alkaline earth metal nitrate, alkaline earth metal formate, alkaline earth metal oxalate, and alkaline earth metal lactate.

24. The method of claim 23, wherein, The alkaline earth metal salt is selected from at least one of magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate.

25. The method of claim 20, wherein, The cobalt source is selected from at least one of cobalt nitrate, cobalt acetate, cobalt formate, basic cobalt carbonate, cobalt citrate, cobalt chloride, cobalt sulfate, and cobalt phosphate.

26. The method of claim 20, wherein, The modifier matrix is ​​selected from at least one of lanthanum nitrate and cerium nitrate.

27. The method of claim 20, wherein, After precipitation, an aging step is also included to obtain the precipitate product.

28. The method of claim 27, wherein, The aging conditions include a temperature of 30-90℃ and a time of 10-120 minutes.

29. The method of claim 28, wherein, The aging conditions include a temperature of 50-90℃ and a time of 20-120 minutes.

30. The method of claim 20, wherein, The calcination conditions include: a temperature of 400-800℃, a time of 1-20h, and a heating rate of 1-5℃ / min.

31. The method according to claim 30, wherein, The calcination conditions include: a temperature of 450-650℃, a time of 2-10h, and a heating rate of 1.5-5℃ / min.

32. The method of claim 20, wherein, The reducing gas contains 10-30 vol of hydrogen.

33. The method of claim 20, wherein, The heat treatment is performed at a temperature of 300-450℃ for 1-24 hours.

34. The method of claim 33, wherein, The heat treatment is performed at a temperature of 350-440℃ for 2-8 hours.

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