Method for preparing long-chain olefin and co-producing fatty aldehyde and formic acid from fatty acid methyl ester

Abstract

The invention belongs to the technical field of fatty acid methyl ester conversion, and discloses a method for preparing long-chain alpha-olefin and co-producing fatty aldehyde and formic acid from fatty acid methyl ester. The method comprises the following steps: carrying out hydrogenation reaction on fatty acid methyl ester to generate fatty alcohol and methanol; carrying out dehydration / dehydrogenation reaction on the fatty alcohol to obtain long-chain alpha-olefin, fatty aldehyde, water and hydrogen; carrying out dehydrogenation reaction on the methanol to generate methyl formate and hydrogen; carrying out hydrolysis reaction on the methyl formate to obtain formic acid and methanol; wherein the catalyst used in the dehydration / dehydrogenation reaction of the fatty alcohol comprises a dehydrogenation active site, a dehydration active site, a dispersing aid and a carrier; the dispersity of the dehydrogenation active site is greater than 31.0%; the concentration of the dehydration active site is 4.5 to 9.0 [mu] mol / g. Three high-added-value products of long-chain alpha-olefin, fatty aldehyde and formic acid can be simultaneously produced by using the single raw material fatty acid methyl ester, the comprehensive utilization rate of byproducts in the process is high, zero discharge of wastewater in the process is realized, and balanced utilization of the raw material and the products is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fatty acid methyl ester conversion, and particularly relates to a method for preparing long-chain α-olefins from fatty acid methyl esters with co-production of fatty aldehydes and formic acid. Background Art

[0002] Long-chain α-olefins are important hydrocarbons, mainly used in fields such as polymer materials and surfactants. They can be combined with other monomers through polymerization reactions to prepare polymer materials such as polyethylene and polypropylene; they can also be used to prepare surfactants such as sodium alkylbenzene sulfonate, which are widely used in detergents, emulsifiers, wetting agents, etc.; as raw materials for rubber, they are synthesized with other monomers to form rubber; they can also be used to prepare polymer additives, asphalt modifiers, pharmaceutical intermediates, spices, etc. The global long-chain α-olefin market has a large scale and high market demand, and is one of the important raw materials in the chemical industry.

[0003] The production of long-chain α-olefins can be obtained by hydrogenating fatty acid methyl esters to obtain fatty alcohols, and then through catalytic dehydration reactions, as reported in patents CN103333038B and CN105693905B.

[0004] Fatty aldehydes appear in natural plants, but their content in nature is very small. Fatty aldehydes have special fragrances and properties, making them raw materials for food flavors, cosmetic fragrances, and special pharmaceutical intermediates. Fatty aldehydes have broad application prospects in fields such as food, cosmetics, and medicine.

[0005] The production methods of formic acid include methanol carbonylation and methanol dehydrogenation-hydrolysis methods. Among them, the methanol dehydrogenation-hydrolysis method is a green and environmentally friendly formic acid synthesis technology, as reported in patents CN111774070B and CN105859555B.

[0006] Formic acid is a colorless and transparent liquid, commonly used in the manufacture of pharmaceuticals, rubber, leather, dyes and other industries. Formic acid is widely used in fields such as food, medicine, and cosmetics as preservatives, catalysts or acidic regulators, and is favored because of its low toxicity, easy volatility, good solubility, etc. In addition, formic acid can also be used as a cleaning agent, dehydrating agent, disinfectant, etc., and is widely used in various fields. The global market demand for formic acid is relatively large, and with the continuous expansion of emerging markets, its market prospect is still very broad.

[0007] If fatty acid methyl ester is used as a raw material for hydrogenation to produce fatty alcohol, and the fatty alcohol is then subjected to dehydration / dehydrogenation reaction to produce two target products, namely α-olefin and fatty aldehyde, the ratio of the two products can be flexibly adjusted according to the change of market demand, so that the same reaction device and catalyst can produce two products with relatively high added value. At the same time, another hydrogenation product of fatty acid methyl ester, methanol, can be dehydrogenated to produce formic acid. This systematic method can improve the competitiveness of products and the economy of the entire process.

[0008] In view of this, the present invention is specifically proposed. Summary of the Invention

[0009] The object of the present invention is to provide a method for preparing long-chain α-olefin by co-producing fatty aldehyde and formic acid from fatty acid methyl ester, so as to realize the production of three high-value-added products from a single raw material.

[0010] To achieve the above object, the present invention specifically adopts the following technical solutions: A method for preparing long-chain α-olefin by co-producing fatty aldehyde and formic acid from fatty acid methyl ester, comprising the following steps: S1: Hydrogenating fatty acid methyl ester to produce fatty alcohol and methanol; after separating the hydrogenation products of fatty acid methyl ester, namely fatty alcohol and methanol, the fatty alcohol is used as a raw material for producing long-chain α-olefin and fatty aldehyde, and the methanol is used as a raw material for producing formic acid; S2: Subjecting the fatty alcohol to dehydration / dehydrogenation reaction to obtain long-chain α-olefin, fatty aldehyde, water and hydrogen; S3: Subjecting the methanol to dehydrogenation reaction to produce methyl formate and hydrogen; S4: Subjecting the methyl formate to hydrolysis reaction to obtain formic acid and methanol; Wherein, the catalyst used in the dehydration / dehydrogenation reaction of the fatty alcohol comprises a dehydrogenation active site, a dehydration active site, a dispersion aid and a carrier; the dispersion degree of the dehydrogenation active site is greater than 31.0%; the concentration of the dehydration active site is 4.5 - 9.0 μmol / g.

[0011] In the technical solution of the present invention, preferably, the dispersion degree of the dehydrogenation active site is greater than 31.0%. Below this value, the distribution of the active metal is uneven and agglomeration occurs, resulting in a decrease in the dehydrogenation performance of the catalyst; the concentration of the dehydration active site is between 4.5 - 9.0 μmol / g. Below this ratio, the dehydration activity of the catalyst is insufficient, and above this ratio, the generated α-olefin is isomerized to form internal olefin.

[0012] Optionally, the dehydrogenation active site is provided by any one or several of transition metals Cu, Zn, Cr, the dehydration active site is provided by active oxides TiO2 and / or Al2O3, the dispersion aid is CeO2 and / or Y2O3, and the carrier is diatomaceous earth, silica or molecular sieve.

[0013] Metals such as Cu, Zn, and Cr have excellent alcohol dehydrogenation functions; the role of TiO2 or Al2O3 is to form active oxides, enabling the catalyst to have excellent hydroxyl dehydration functions; the role of CeO2 or Y2O3 is to form dispersion aids, which can improve the dispersion of active components on the carrier, enabling the catalyst to have efficient fatty alcohol dehydrogenation and dehydration functions.

[0014] Optionally, the proportion of the transition metal is 0.8 - 3.6 wt%, the proportion of the active oxide is 6.1 - 10.8 wt%, the proportion of the dispersion aid is 0.5 - 2.3 wt%, and the proportion of the carrier is 86.4 - 91.0 wt%.

[0015] Optionally, the preparation method of the catalyst includes: S101: Add polyacrylamide and the carrier into the aqueous solution of the transition metal compound simultaneously. After precipitation, filter and collect the precipitate, wash it, perform the first static settlement, the first drying, and freezing to obtain Sample 1; S102: Add the active oxide precursor compound and the dispersion aid into water to obtain an aqueous solution, impregnate it on Sample 1 in an equal volume, and after the second static settlement and the second drying, obtain Sample 2; S103: Heat and reduce Sample 2 in an H2 atmosphere, and then after cooling to room temperature in an H2 atmosphere, passivate it with oxygen-deficient air to obtain the product.

[0016] Specifically, the method of Step S101 is as follows: Add the transition metal compound into deionized water to form an aqueous solution. Add polyacrylamide and the carrier into the aqueous solution of the transition metal compound simultaneously. With the carrier as the nucleation center, polyacrylamide and the transition metal compound are co-deposited on the surface of the carrier to form a precipitate. The purpose of using polyacrylamide is that the nitrogen-containing functional groups of polyacrylamide can complex with the transition metal compound and uniformly precipitate it on the surface of the carrier, constructing the dehydrogenation active sites and providing conditions for the introduction of subsequent dehydration active sites.

[0017] Furthermore, the transition metal compound is one or several of copper nitrate, zinc nitrate, or chromium nitrate in any proportion mixture; Preferably, the mass ratio of the transition metal compound to polyacrylamide is (0.45 - 1.12):(0.30 - 0.76); Preferably, the mass ratio of the transition metal compound to the carrier is (0.45 - 1.12):(10 - 12); Preferably, the first static settlement is carried out at room temperature for 2 - 5 h; Preferably, the first drying is multiple drying; Preferably, the multiple drying is carried out at 30 - 60 °C for 2 - 5 h and then at 100 - 120 °C for 6 - 12 h; Preferably, the freezing temperature is -25 °C or below.

[0018] In the above step S102, as a preferred embodiment, before impregnation, the aqueous solution is heated to 40 - 60 °C, and then impregnated on Sample 1 in an equal volume, which can greatly reduce the stacking coverage probability between the dehydrogenation active sites and the dehydration active sites, so that the dehydrogenation active sites and the dehydration active sites are organically matched to achieve the best catalytic effect.

[0019] In the method of the present invention, during the preparation of the catalyst, two methods of introducing a dispersion aid and freeze impregnation are used simultaneously to highly disperse and reasonably match the two active components, so that they can play a role simultaneously and efficiently synthesize α-olefins and fatty aldehydes.

[0020] Preferably, the dosage of the active oxide precursor compound is 0.93 - 6.82 times that of the transition metal compound; further, the dosage of the dispersion aid is 0.28 - 0.88 times that of the transition metal compound; furthermore, the mass ratio of the active oxide precursor compound, the dispersion aid and water is (1.10 - 7.63):(0.19 - 0.99):(8 - 15).

[0021] If the dosage of the active oxide is too low, the dehydration active sites are insufficient, and the catalyst cannot achieve effective hydroxyl dehydration reaction activity. If the dosage of the active oxide is too high, the dehydration active sites are excessive, resulting in the further isomerization of α-olefins into internal olefin by-products. If the dosage of the dispersion aid is too low, the dispersion of the dehydrogenation and dehydration active components is insufficient, and the conversion rate of fatty alcohols decreases. If the dosage of the dispersion aid is too high, it occupies too much of the carrier surface, resulting in a decrease in the selectivity of α-olefins and fatty aldehydes.

[0022] Preferably, the second standing is carried out at room temperature for 2 - 5 h; Preferably, the second drying is multiple drying; more preferably, the multiple drying is carried out at 30 - 60 °C for 2 - 5 h and then at 100 - 120 °C for 6 - 12 h.

[0023] The multiple drying conditions are the optimal conditions. Single drying or beyond this range will cause uneven distribution of active components during drying and cracking of the catalyst, affecting the subsequent preparation conditions and ultimately the catalyst performance.

[0024] In the above step S103, the heating and reduction in an H2 atmosphere are as follows: heating to 300 - 500 °C at a rate of 0.5 - 2.0 °C / min, with a reduction time of 4 - 6 h; the H2 space velocity is 400 - 700 h -1 。

[0025] Preferably, the passivation with oxygen-deficient air is carried out as follows: passivate with oxygen-deficient air having an O2 content of 0.5-2.0% for 3-5 h.

[0026] In the technical solution of the present invention, for the catalyst used, the method of embedding nitrogen-containing organic matter is adopted to complex and co-precipitate metals such as Cu, Cr, Zn and the organic matter, so as to achieve a highly dispersed dehydrogenation active site, creating a basic condition for the organic matching of the dehydrogenation active site and the dehydration active site introduced subsequently; the method of freeze impregnation is adopted to introduce dehydration active sites such as TiO2 and Al2O3 onto the dehydrogenation catalyst. At the same time, through promoters such as CeO2 and Y2O3, the two active sites of dehydrogenation and dehydration are highly dispersed and organically matched, so that the catalyst has both the function of alcohol dehydrogenation and the function of hydroxyl catalytic dehydration.

[0027] Optionally, in the step S1, the temperature of the hydrogenation reaction is 180-270 °C, and the pressure is 3.0-6.0 MPa. The temperature of the hydrogenation reaction can be any value between 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C or 270 °C, and the pressure can be any value between 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa or 6.0 MPa.

[0028] The above operating conditions are the optimal operating conditions obtained through a large amount of theoretical analysis and experimental verification. If the temperature of the hydrogenation reaction is lower than 180 °C or the pressure is lower than 3.0 MPa, the hydrogenation reaction activity of the catalyst is insufficient, and fatty acid methyl ester cannot be fully hydrogenated to obtain fatty alcohol and methanol; if the reaction temperature is higher than 270 °C or 6.0 MPa, the product fatty alcohol and methanol will undergo an over-hydrogenation reaction, and the alcohols will be further decomposed into hydrocarbons.

[0029] Preferably, in the hydrogenation reaction, the liquid hourly space velocity of the fatty acid methyl ester is 0.2-2.0 h -1 , and the H2 hourly space velocity is 200-1000 h -1 . The liquid hourly space velocity of the fatty acid methyl ester can be 0.2 h -1 , 0.4 h -1 , 0.6 h -1 , 0.8 h -1 , 1.0 h -1 , 1.2 h -1 , 1.4 h -1 , 1.6 h -1 , 1.8 h -1 or 2.0 h -1 between any values, and the H2 hourly space velocity can be 200 h -1 , 400 h -1 , 600 h -1 , 800 h-1 or 1000h -1 Any value between them.

[0030] When the liquid hourly space velocity of fatty acid methyl ester is higher than 2.0 h -1 or the H2 hourly space velocity is lower than 200 h -1 , the hydrogenation reaction activity of the catalyst is insufficient, and the fatty acid methyl ester cannot be fully hydrogenated to obtain fatty alcohol and methanol; when the liquid hourly space velocity of fatty acid methyl ester is lower than 0.2 h -1 or the H2 hourly space velocity is higher than 2000 h -1 , the over-hydrogenation reaction of the product fatty alcohol and methanol will occur, and the alcohols will be further decomposed into hydrocarbons.

[0031] Optionally, the temperature of the dehydration / dehydrogenation reaction in step S2 is 220 - 320 °C, and the pressure is 0.1 - 0.4 MPa. The temperature of the dehydration / dehydrogenation reaction can be any value between 220 °C, 240 °C, 260 °C, 280 °C, 300 °C, or 320 °C, and the pressure of the dehydration / dehydrogenation reaction can be any value between 0.1 MPa, 0.2 MPa, 0.3 MPa, or 0.4 MPa. The liquid hourly space velocity of the fatty alcohol is 0.1 - 1.0 h -1 . The liquid hourly space velocity of the fatty alcohol can be 0.1 h -1 , 0.2 h -1 , 0.3 h -1 , 0.4 h -1 , 0.5 h -1 , 0.6 h -1 , 0.7 h -1 , 0.8 h -1 , 0.9 h -1 or 1.0 h -1 Any value between them.

[0032] When the temperature of the dehydration / dehydrogenation reaction is lower than 220 °C or higher than 0.4 MPa, the dehydration / dehydrogenation reaction activity of the catalyst is insufficient, and the conversion rate of fatty alcohol decreases; when the reaction temperature is higher than 320 °C or the reaction pressure is lower than 0.1 MPa, the dehydrated product long-chain α-olefin will be further decomposed to form short-chain olefins. Through experimental verification, when the liquid hourly space velocity of fatty alcohol is higher than 1.0 h -1 , the dehydration / dehydrogenation reaction activity of the catalyst is insufficient, and the conversion rate of fatty alcohol decreases; when the liquid hourly space velocity of fatty alcohol is lower than 0.1 h -1 , the dehydrated product long-chain α-olefin will be further decomposed to form short-chain hydrocarbons.

[0033] Optionally, the temperature of the dehydrogenation reaction in step S3 is 200 - 300 °C, and the pressure is 0.1 - 0.4 MPa. The temperature of the dehydrogenation reaction can be any value between 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C, and the pressure of the dehydration reaction can be any value between 0.1 MPa, 0.2 MPa, 0.3 MPa or 0.4 MPa.

[0034] Verified by experiments, when the dehydrogenation reaction temperature is lower than 200 °C or higher than 0.4 MPa, the dehydrogenation reaction activity of the catalyst is insufficient and the methanol conversion rate decreases; when the reaction temperature is higher than 300 °C or the reaction pressure is lower than 0.1 MPa, the dehydrogenation product methyl formate will further decompose to form hydrocarbons.

[0035] Preferably, the liquid hourly space velocity of methanol is 0.3 - 3.0 h -1 . The liquid hourly space velocity of methanol can be any value between 0.3 h -1 , 0.6 h -1 , 0.9 h -1 , 1.2 h -1 , 1.5 h -1 , 1.8 h -1 , 2.1 h -1 , 2.4 h -1 , 2.7 h -1 or 3.0 h -1 between any values.

[0036] Verified by experiments, when the liquid hourly space velocity of methanol is higher than 3.0 h -1 , the dehydrogenation reaction activity of the catalyst is insufficient and the methanol conversion rate decreases; when the liquid hourly space velocity of fatty alcohol is lower than 0.3 h -1 , the dehydrogenation product methyl formate will further decompose to form hydrocarbons.

[0037] Optionally, the hydrogen obtained in step S2 and / or S3 is recycled and used for the hydrogenation reaction in step S1.

[0038] Optionally, the methanol obtained in step S4 is recycled and used for the dehydrogenation reaction in step S3.

[0039] Optionally, 90 - 98% of the water required for the hydrolysis reaction in step S4 comes from the water generated in step S2, and 2 - 10% comes from external water supply.

[0040] Optionally, the molar ratio of fatty acid methyl ester, long-chain α-olefin, fatty aldehyde and formic acid is 100:(90.4 - 98.2):(1.2 - 8.9):(96.4 - 98.2).

[0041] In the process of producing long-chain α-olefins and fatty aldehydes from fatty acid methyl esters, methanol, water, and hydrogen are by-produced. The reaction requires hydrogen as a raw material for the hydrogenation reaction; the production of formic acid by methanol dehydrogenation requires raw materials methanol and water, and hydrogen is by-produced. The present invention creatively couples the above two production processes, comprehensively utilizes the hydrogen and water generated in the reaction process, achieves the comprehensive utilization of raw materials and products, does not use external hydrogen additionally, and the hydrogen generated by methanol dehydrogenation and fatty alcohol dehydrogenation is used not only for the hydrogenation of fatty acid methyl esters but also for the hydrogen loss in the process. At the same time, the methanol generated by the hydrolysis reaction of methyl formate is returned to the system to continue the dehydrogenation reaction to generate methyl formate and hydrogen, realizing recycling. On the one hand, it greatly saves the raw material cost, and at the same time avoids the waste of resources caused by the emission of by-products.

[0042] The beneficial effects of the present invention: The present invention uses a single raw material, fatty acid methyl ester, to simultaneously produce three high-value-added products: long-chain α-olefins, fatty aldehydes, and formic acid. Among them, the total molar yield of long-chain α-olefins and fatty aldehydes is greater than 92%, and the molar yield of formic acid is greater than 96%. The hydrogen by-produced in the dehydrogenation reaction is used for the hydrogenation reaction, and the water generated in the dehydration reaction is used for the hydrolysis reaction, comprehensively utilizing the hydrogen and water generated in the reaction process to achieve the balanced utilization of raw materials and products. Almost no external hydrogen is used in the process, and the process wastewater is zero-discharged. Compared with the prior art, the present invention has the advantages of high comprehensive utilization rate of by-products, zero wastewater discharge, and high system integration.

[0043] In the process of preparing α-olefins and fatty aldehydes, the synergistic effect of transition metals, active oxides, and dispersion aids in the catalyst used in the present invention enables the catalyst to simultaneously have the functions of dehydration and dehydrogenation of fatty alcohols, generating α-olefins and fatty aldehydes. The ratio of α-olefin and fatty aldehyde products can be adjusted according to the operating parameters by this method. For the preparation method of this catalyst, a co-precipitation method of transition metal salts and polyacrylamide is used to deposit transition metals and organic carbon and nitrogen compounds on the carrier, so that the nitrogen-containing functional groups are complexed with transition metal compounds, thereby promoting the dispersion of active components; the stacking and covering of active components are inhibited by freeze impregnation, and the method of freeze impregnation combined with dispersion aids is used to immobilize the active site precursor on the catalyst, improving the synergistic effect of each active component and enabling the catalyst to have the dual-functional characteristics of synthesizing two products. Brief Description of the Drawings

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 This is the production process flow chart of the embodiment of the present invention. Specific embodiments

[0047] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0048] Example 1 Preparation of catalyst Weigh 0.70 g of zinc nitrate and add it to 100 ml of deionized water. Add 0.47 g of polyacrylamide and 11 g of carrier molecular sieve to the solution at the same time. Filter and wash the obtained precipitate, place it at room temperature for 2 h, dry it at 50 °C for 4 h, dry it at 100 °C for 9 h, and freeze it at -25 °C or below to obtain Sample 1.

[0049] Add 1.83 g of titanium oxysulfate and 0.19 g of cerium nitrate to 15 ml of deionized water. Heat the obtained solution to 40 °C and impregnate it on Sample 1 in an equal volume. Place it at room temperature for 4 h, dry it at 50 °C for 3 h, and dry it at 120 °C for 9 h to obtain Sample 2.

[0050] Heat Sample 2 to 300 °C at a rate of 0.5 °C / min in an H2 atmosphere and reduce it at this temperature for 5 h. The H2 space velocity is 600 h -1 . After the reduced sample is cooled to room temperature in an H2 atmosphere, passivate it with lean oxygen air with an O2 content of 0.5% for 4 h to obtain the catalyst.

[0051] The obtained catalyst has a zinc metal percentage content of 1.2 wt%, a titanium dioxide percentage content of 10.8 wt%, a cerium oxide percentage content of 0.5 wt%, a carrier molecular sieve percentage content of 87.5 wt%, a zinc dehydrogenation active site dispersion degree of 33.2%, and a dehydration active site concentration of 4.5 μmol / g.

[0052] Example 2 Preparation of catalyst Weigh 1.12 g of copper nitrate and add it to 100 ml of deionized water. Add 0.76 g of polyacrylamide and 12 g of carrier diatomite to the solution at the same time. Filter and wash the obtained precipitate, place it at room temperature for 3 h, dry it at 40 °C for 2 h, dry it at 120 °C for 10 h, and freeze it at -25 °C or below to obtain Sample 1.

[0053] 7.63 g of aluminum nitrate and 0.99 g of cerium nitrate were added to 8 ml of deionized water. The resulting solution was heated to 50 °C and impregnated onto Sample 1 in equal volume. It was left at room temperature for 4 h, dried at 30 °C for 4 h, and then dried at 110 °C for 6 h to obtain Sample 2.

[0054] Sample 2 was heated to 400 °C at a rate of 1.0 °C / min under a H2 atmosphere and reduced at this temperature for 6 h. The H2 space velocity was 700 h -1 . After the sample was cooled to room temperature under a H2 atmosphere, it was passivated with lean oxygen air with an O2 content of 1.0% for 5 h to obtain the catalyst.

[0055] The obtained catalyst had a metal copper percentage content of 1.8 wt%, an aluminum oxide percentage content of 9.5 wt%, a cerium oxide percentage content of 2.3 wt%, a carrier diatomaceous earth percentage content of 86.4 wt%, a copper dehydrogenation active site dispersion of 35.5%, and a dehydration active site concentration of 5.9 μmol / g.

[0056] Example 3 Preparation of the catalyst 0.67 g of chromium nitrate was weighed and added to 100 ml of deionized water. 0.45 g of polyacrylamide and 10 g of silica were simultaneously added to the solution. The resulting precipitate was filtered and washed, left at room temperature for 4 h, dried at 30 °C for 2 h, dried at 100 °C for 8 h, and then frozen below -25 °C to obtain Sample 1.

[0057] 1.10 g of titanium oxysulfate and 0.24 g of yttrium nitrate were added to 9 ml of deionized water. The resulting solution was heated to 60 °C and impregnated onto Sample 1 in equal volume. It was left at room temperature for 5 h, dried at 40 °C for 2 h, and then dried at 100 °C for 7 h to obtain Sample 2.

[0058] Sample 2 was heated to 500 °C at a rate of 0.5 °C / min under a H2 atmosphere and reduced at this temperature for 4 h. The H2 space velocity was 500 h -1 . After the sample was cooled to room temperature under a H2 atmosphere, it was passivated with lean oxygen air with an O2 content of 1.5% for 3 h to obtain the catalyst.

[0059] The obtained catalyst had a metal chromium percentage content of 3.6 wt%, a titanium dioxide percentage content of 7.2 wt%, a yttrium oxide percentage content of 0.8 wt%, a carrier silica percentage content of 88.4 wt%, a chromium dehydrogenation active site dispersion of 39.4%, and a dehydration active site concentration of 9.0 μmol / g.

[0060] Example 4 Method for preparing long-chain α-olefins by fatty acid methyl esters with co-production of fatty aldehydes and formic acid According to the method provided by the present invention and in accordance with Figure 1 the process flow chart shown, fatty acid methyl esters were used to prepare long-chain α-olefins, fatty aldehydes, and formic acid, asFigure 1 As shown, at the initial stage of the reaction, externally supplied hydrogen needs to be temporarily used to initiate the hydrogenation reaction. After the reaction starts and the reaction circulation system is established, the hydrogen produced by the subsequent reaction is sufficient for the hydrogen required for the entire system reaction. Compared with the self-produced hydrogen, the proportion of the externally supplied hydrogen at the initial stage is extremely low. After calculation, if the annual operating time is 8000 hours, the duration of the externally supplied hydrogen at the initial stage is only about 10 hours. The specific steps are as follows: S1: Methyl stearate with a liquid hourly space velocity of 0.6 h -1 is subjected to a hydrogenation reaction in a hydrogenation reactor under the conditions of 200 °C and 3.5 MPa, and the produced octadecanol and methanol are separated and reserved; S2: The octadecanol produced by the hydrogenation reaction in S1 is subjected to a dehydration / dehydrogenation reaction using the catalyst of Example 1 under the conditions of 240 °C and 0.3 MPa, and the liquid hourly space velocity of octadecanol is 0.6 h -1 , to obtain long-chain octadecene, octadecanal, water and hydrogen, and separation is carried out. Specifically, the target products, long-chain octadecene and octadecanal, are separately collected. At the same time, the hydrogen is introduced into the hydrogen recycling pipeline as shown in Figure 1 and enters the hydrogenation reactor for the hydrogenation reaction in S1; the water is introduced into the water recycling pipeline and enters the hydrolysis reactor for standby; S3: The methanol obtained in S1 is subjected to a dehydrogenation reaction under the conditions of 240 °C and 0.3 MPa to produce methyl formate and hydrogen, and the liquid hourly space velocity of methanol is 0.6 h -1 ; the hydrogen is introduced into the hydrogen recycling pipeline as shown in Figure 1 and enters the hydrogenation reactor for the hydrogenation reaction in S1; S4: The methyl formate obtained in S3 is subjected to a hydrolysis reaction in a hydrolysis reactor to obtain formic acid and methanol. After separation, the methanol returns to step S3 for continued dehydrogenation reaction, and the product formic acid is collected; 93% of the water used in this step comes from the water generated in step S2, and 7% comes from external water supply.

[0061] Example 5 Method for preparing long-chain α-olefins by fatty acid methyl ester with co-production of fatty aldehydes and formic acid The difference from Example 4 is that the raw material is methyl myristate, and the conditions for the hydrogenation reaction in S1 are 250 °C and 5.0 MPa; the dehydration / dehydrogenation reaction in S2 uses the catalyst of Example 2, and the reaction conditions are 300 °C and 0.1 MPa; the conditions for the dehydrogenation reaction in S3 are 300 °C and 0.1 MPa.

[0062] Example 6 Method for preparing long-chain α-olefins by fatty acid methyl ester with co-production of fatty aldehydes and formic acid It is different from Example 4 in that the raw material is methyl palmitate, the conditions for the hydrogenation reaction in S1 are 180 °C and 6.0 MPa; the catalyst used in the dehydration / dehydrogenation reaction in S2 is that of Example 3, and the reaction conditions are 220 °C and 0.4 MPa; the conditions for the dehydrogenation reaction in S3 are 200 °C and 0.4 MPa.

[0063] Comparative Example 1 It is different from Example 4 only in that the temperature of the dehydration / dehydrogenation reaction in S2 is 350 °C.

[0064] Comparative Example 2 It is different from Example 4 only in that the temperature of the dehydrogenation reaction in S3 is 330 °C.

[0065] Comparative Example 3 It is different from Example 4 only in that the catalysts used for the preparation of α-olefins and fatty aldehydes from fatty alcohols are different. Compared with Example 1, in the preparation process, the amount of zinc nitrate added is 0.40 g, and the obtained catalyst has a metal zinc percentage content of 0.9 wt%, a titanium dioxide percentage content of 10.8 wt%, a cerium oxide percentage content of 0.5 wt%, a support molecular sieve percentage content of 87.8 wt%, a zinc dehydrogenation active site dispersion of 26.0%, and a dehydration active site concentration of 2.8 μmol / g.

[0066] Comparative Example 4 It is different from Example 4 only in that the catalysts used for the preparation of α-olefins and fatty aldehydes from fatty alcohols are different. Compared with Example 2, the difference is only that the amount of cerium nitrate added in the preparation process is 1.20 g. The obtained catalyst has a metal copper percentage content of 1.8 wt%, an aluminum oxide percentage content of 9.5 wt%, a cerium oxide percentage content of 2.7 wt%, a support diatomaceous earth percentage content of 86.0 wt%, a copper dehydrogenation active site dispersion of 21.2%, and a dehydration active site concentration of 3.6 μmol / g.

[0067] Comparative Example 5 It is different from Example 4 only in that the catalysts used for the preparation of α-olefins and fatty aldehydes from fatty alcohols are different. Compared with Example 3, the difference is only that freezing was not carried out during the preparation of Sample 1. The obtained catalyst has a metal chromium percentage content of 3.6 wt%, a titanium dioxide percentage content of 7.2 wt%, a yttrium oxide percentage content of 0.8 wt%, a support silica percentage content of 88.4 wt%, a chromium dispersion of 8.0%, and a dehydration active site concentration of 2.3 μmol / g.

[0068] The relevant parameters of the production processes and products of Examples 4-6 and Comparative Examples 1-5 are shown in Table 1 below: Table 1 Molar yields of the products synthesized from fatty acid methyl esters in Examples 4-6 and Comparative Examples 1-5 。

[0069] It can be seen from Examples 1-3 that the method for preparing long-chain α-olefins, co-producing fatty aldehydes and formic acid from fatty acid methyl esters provided by the present invention not only realizes the reasonable recycling of intermediate products and by-products during the reaction process, hardly uses hydrogen additionally, does not discharge wastewater during the reaction process, has a high overall yield, but also the yields of various target products can be adjusted and controlled, with high flexibility. It can be seen from Table 1 that the sum of the molar yields of long-chain α-olefins and fatty aldehydes is greater than 92%, and the molar yield of formic acid is greater than 96%.

[0070] By comparing Example 4 and Comparative Example 1, it can be seen that when other reaction conditions are the same and only the temperature of the S2 dehydration / dehydrogenation reaction step is different, Comparative Example 1 shows the same formic acid yield as Example 4, but the yields of long-chain α-olefins and fatty aldehydes decrease significantly due to the change of the dehydration / dehydrogenation reaction conditions, only being 70.2% and 0.2%, significantly lower than 84.2% and 9.8% of Example 4. Similarly, by comparing Example 4 and Comparative Example 2, it can be seen that when other reaction conditions are the same and only the temperature of the S3 dehydrogenation reaction step is different, the yields of long-chain α-olefins and fatty aldehydes in Comparative Example 2 and Example 4 are the same, and the formic acid yield is only 72.7%, significantly lower than 97.5% of Example 4. By comparing Example 4 and Comparative Examples 3-5, it can be seen that when other reaction conditions are the same and only the preparation method of the catalyst for preparing α-olefins and fatty aldehydes from fatty alcohols is different, Comparative Examples 3-5 show the same formic acid yield as Example 4, but the yields of long-chain α-olefins and fatty aldehydes decrease significantly due to the change of the dehydration / dehydrogenation catalyst components, only being 50.8-75.6% and 0.2-7.2%, significantly lower than 84.2% and 9.8% of Example 4. On the one hand, it shows that the present invention has a higher overall yield of target products and higher reaction efficiency by adopting a special catalyst preparation method and under the preferred reaction parameters or reaction conditions of the present invention.

[0071] Please note that the technical features of the above examples can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above examples are described. However, as long as the combinations of these technical features do not conflict, they should be considered as the scope described in this specification. The above examples only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing long-chain α-olefins from fatty acid methyl esters with co-production of fatty aldehydes and formic acid, characterized in that, It includes the following steps: Hydrogenate fatty acid methyl ester to produce fatty alcohol and methanol; Perform dehydration / dehydrogenation reaction on the fatty alcohol to obtain long-chain α-olefin, fatty aldehyde, water and hydrogen; Perform dehydrogenation reaction on the methanol to produce methyl formate and hydrogen; Perform hydrolysis reaction on the methyl formate to obtain formic acid and methanol; Among them, the catalyst used in the dehydration / dehydrogenation reaction of the fatty alcohol includes a dehydrogenation active site, a dehydration active site, a dispersion aid and a carrier; the dispersion degree of the dehydrogenation active site is greater than 31.0%; the concentration of the dehydration active site is 4.5 - 9.0 μmol / g.

2. The method according to claim 1, characterized in that, The dehydrogenation active site is provided by any one or several of transition metals Cu, Zn, Cr, the dehydration active site is provided by active oxides TiO2 and / or Al2O3, the dispersion aid is CeO2 and / or Y2O3, and the carrier is diatomite, silica or molecular sieve.

3. The method according to claim 1, characterized in that, In the catalyst, the proportion of the transition metal is 0.8 - 3.6 wt%, the proportion of the active oxide is 6.1 - 10.8 wt%, the proportion of the dispersion aid is 0.5 - 2.3 wt%, and the proportion of the carrier is 86.4 - 91.0 wt%.

4. The method according to claim 1, wherein The preparation method of the catalyst includes: S101: Add polyacrylamide and the carrier into the aqueous solution of the transition metal compound at the same time. After precipitation, filter and collect the precipitate, wash it, perform the first static settling, the first drying, and freezing to obtain sample one; S102: Add the active oxide precursor compound and the dispersion aid into water to obtain an aqueous solution, impregnate it on the sample one in an equal volume, and perform the second static settling and the second drying to obtain sample two; S103: Heat and reduce the sample two in an H2 atmosphere, then cool it to room temperature in an H2 atmosphere and passivate it with lean oxygen air to obtain the product.

5. The method according to claim 4, characterized in that The step S101 satisfies one or more of the following conditions: a. The transition metal compound is one or several of copper nitrate, zinc nitrate or chromium nitrate in any proportion mixture; b. The mass ratio of the transition metal compound to polyacrylamide is (0.45 - 1.12):(0.30 - 0.76); c. The mass ratio of the transition metal compound to the carrier is (0.45 - 1.12):(10 - 12); d. The first static settling is carried out at room temperature for 2 - 5 h; e. The first drying is multiple drying; f. The multiple drying is drying at 30 - 60 °C for 2 - 5 h and drying at 100 - 120 °C for 6 - 12 h; g. The freezing temperature is -25 °C and below.

6. The preparation method according to claim 4 or 5, characterized in that, The step S102 satisfies one or more of the following conditions: a. The aqueous solution is heated to 40 - 60 °C before impregnation; b. The dosage of the active oxide precursor compound is 0.93 - 6.82 times that of the transition metal compound; c. The dosage of the dispersion aid is 0.28 - 0.88 times that of the transition metal compound; d. The mass ratio of the active oxide precursor compound, the dispersion aid and water is (1.10 - 7.63):(0.19 - 0.99):(8 - 15); e. The second static settling is carried out at room temperature for 2 - 5 h; f. The second drying is multiple drying; g. The multiple drying is drying at 30 - 60 °C for 2 - 5 h and drying at 100 - 120 °C for 6 - 12 h.

7. The preparation method according to claim 4, characterized in that, The step S103 satisfies one or more of the following conditions: a. The temperature increase and reduction under H2 atmosphere are as follows: The temperature is increased to 300 - 500 °C at a rate of 0.5 - 2.0 °C / min, the reduction time is 4 - 6 h; the H2 space velocity is 400 - 700 h -1 ; b. The passivation with oxygen - depleted air is: passivating with oxygen - depleted air with an O2 content of 0.5 - 2.0% for 3 - 5 h.

8. The method according to claim 1, wherein The temperature of the hydrogenation reaction is 180 - 270 °C, and the pressure is 3.0 - 6.0 MPa. In the hydrogenation reaction, the liquid hourly space velocity of the fatty acid methyl ester is 0.2 - 2.0 h -1 , and the H2 hourly space velocity is 200 - 1000 h -1 .

9. The method according to claim 1, characterized in that The temperature for the dehydration / dehydrogenation reaction of the fatty alcohol is 220 - 320 °C, the pressure is 0.1 - 0.4 MPa, and the liquid hourly space velocity of the fatty alcohol is 0.1 - 1.0 h -1 .

10. The method according to claim 1, wherein The molar ratio of the fatty acid methyl ester, long - chain α - olefin, fatty aldehyde and formic acid is 100:(90.4 - 98.2):(1.2 - 8.9):(96.4 - 98.2).

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