Zeolite molecular sieve catalyst containing rare earth elements and its synthesis method and use

Abstract

The present application provides a zeolite molecular sieve catalyst containing rare earth elements, and a synthesis method and use thereof, wherein the rare earth element is selected from at least one of the following: yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; based on the weight of the zeolite molecular sieve, the content of the rare earth element is greater than 0% by weight and less than or equal to 0.017% by weight, and the zeolite molecular sieve has a silicon-aluminum ratio of 45:1 to 60:1. The catalyst of the present application achieves a catalytic activity that is superior to that of conventional catalysts in the isomerization reaction of linear unsaturated carboxylic acids to prepare isomerized saturated carboxylic acids, and can use raw materials with a linear monounsaturated carboxylic acid content far lower than that of the past to achieve excellent target product selectivity and yield.

Description

Technical Field

[0001] The present application relates to the field of oil and fat chemical industry, and more specifically to a technology for improving zeolite molecular sieve catalysts to enhance the reaction performance of catalytic isomerization of linear unsaturated carboxylic acids. Background Art

[0002] Long-chain fatty acids are a raw material that has received special attention and are widely used in lubricants, polymers, solvents, cosmetics, etc. However, straight-chain saturated fatty acids (such as C18:0) are solid at room temperature, which makes it difficult to handle and process them in many applications; while unsaturated fatty acids are liquid at room temperature, but because of the presence of CC double bonds in the carbon chain, their stability is very poor and they are not suitable for many applications. Isomerized saturated fatty acids refer to branched saturated fatty acids with one or more alkyl side chain structures connected to the main chain. They can largely avoid the problems of straight-chain saturated fatty acids, and because they do not contain CC double bonds in the carbon chain, they have excellent stability. Due to their excellent performance, industrial production in various fields has a very high demand for isomerized saturated fatty acids.

[0003] In order to produce high-quality branched saturated fatty acids on a large scale, people have invested a lot of energy and cost in order to develop a new synthesis technology. Initially, isomerized saturated fatty acids were separated as byproducts of the dimer acid production process, but their physical and chemical properties and output were difficult to meet market requirements. For this reason, people have further developed a process for synthesizing isomerized saturated fatty acids by catalytic isomerization of linear unsaturated fatty acids, in which different types of zeolite molecular sieves are mainly used as catalysts, and examples of these catalysts include ZSM-5 zeolite molecular sieves, β-zeolite molecular sieves, mordenite molecular sieves and ferrierite molecular sieves. However, the problem faced by this process is that the conversion rate and selectivity of the target product of isomerized saturated fatty acids are not ideal, usually both of which are only at a level of about 30% to 40%. There have been some reports that the raw material conversion rate can be increased to a level of about 70% or 80% by adding additional additives, but the selectivity of the target product of isomerized saturated fatty acids can only reach a level of less than 50%, so the yield of the target product is always unsatisfactory. In order to solve the above problems, the researchers proposed an idea of ​​increasing the purity of straight-chain monounsaturated fatty acids in the raw materials as much as possible. However, this approach has very limited improvement on the selectivity and yield of the target product. In addition, the high requirements for raw material purity will further lead to severe restrictions on raw material sources and a significant increase in production costs, which will have an adverse impact on the industrial promotion and scale expansion of the process.

[0004] A lot of research has been conducted on this, but so far no process has been developed that has low requirements on raw material costs and can achieve extremely excellent raw material conversion rate, target product selectivity and yield. There is an urgent need in the art to develop solutions to the above technical problems. Summary of the invention

[0005] In response to the above problems, the inventors of the present application conducted in-depth research and successfully developed a simple, low-cost and effective process method, which achieves excellent catalytic performance in an extremely simple and cost-saving manner, effectively solving a long-standing problem in the prior art.

[0006] The first aspect of the present application provides a zeolite molecular sieve catalyst containing rare earth elements, characterized in that the rare earth element is selected from at least one of the following: yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium; preferably, the rare earth element is praseodymium, samarium, or a combination thereof; based on the weight of the zeolite molecular sieve, the content of the rare earth element is greater than 0% by weight and less than or equal to 0.017% by weight; the zeolite molecular sieve has a silicon-aluminum ratio of 45:1 to 60:1. The catalyst can be used for the catalytic isomerization of linear unsaturated carboxylic acids to prepare isomerized saturated carboxylic acids, for example, it can be used for the synthesis of branched stearic acid by isomerization reaction of oleic acid, linoleic acid or a combination thereof.

[0007] The second aspect of the present application provides a method for synthesizing the zeolite molecular sieve catalyst, which comprises the following steps: (a) mixing a silicon source, an aluminum source, a rare earth element source, a template, a pH adjuster and a solvent to form a raw material mixture; (b) hydrothermally treating the raw material mixture to obtain a solid material; (c) calcining the solid material to obtain a zeolite molecular sieve catalyst precursor; and (d) performing ion exchange on the zeolite molecular sieve catalyst precursor.

[0008] The third aspect of the present application provides a method for preparing an isomerized saturated carboxylic acid by catalytic isomerization of a raw material containing a linear unsaturated carboxylic acid, the method comprising the following steps: (A) in a reaction system containing the catalyst of the present application, isomerizing the linear unsaturated carboxylic acid in the raw material to obtain an isomerized intermediate; (B) hydrogenating the isomerized intermediate obtained in step (A) to obtain the isomerized saturated carboxylic acid. According to a preferred embodiment of the present application, the linear unsaturated carboxylic acid is C 12 -C 22 Straight chain unsaturated carboxylic acid, more preferably oleic acid, linoleic acid, or a combination thereof; the isomerized saturated carboxylic acid is C 12 -C 22 The branched saturated carboxylic acid is more preferably branched stearic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the following paragraphs, various embodiments of the present application are discussed in conjunction with the accompanying drawings. However, it should be noted that the embodiments shown in the accompanying drawings and described in detail below are only some preferred embodiments of the present application, and the scope of protection of the present application is defined by the claims, but is not limited to these preferred embodiments. In addition, for the purpose of clear display, the reactors and various components shown in the drawings of the specification are not drawn according to the true scale.

[0010] Figure 1 A process flow chart showing a method for synthesizing a zeolite molecular sieve catalyst containing a rare earth element according to one embodiment of the present application is shown;

[0011] Figure 2 A schematic diagram of the reaction mechanism for synthesizing branched stearic acid from oleic acid through an isomerization step and a hydrogenation step according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0012] "Range" disclosed herein is in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0013] In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.

[0014] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0015] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0016] In this application, if there is no special explanation, the "including" mentioned herein means open or closed. For example, the "including" may mean that other components not listed may also be included, or only the listed components may be included.

[0017] In the present application, the terms "zeolite molecular sieve catalyst containing rare earth elements", "zeolite molecular sieve containing rare earth elements", "rare earth-doped zeolite molecular sieve catalyst", and "catalyst" can be used interchangeably, all of which refer to the zeolite molecular sieve catalyst containing rare earth elements that is synthesized in situ by introducing rare earth element precursors into the raw materials as described in the present invention.

[0018] The newly developed catalyst in the present application is a zeolite molecular sieve containing rare earth elements, and the zeolite molecular sieve has a porous solid skeleton microstructure mainly composed of silicon-oxygen tetrahedrons and oxygen-aluminum tetrahedrons connected to each other by shared oxygen atoms, and the characteristics of the zeolite molecular sieve and various synthesis processes are known in the art. According to one embodiment of the present application, the average pore size of the microporous structure of the zeolite molecular sieve can be 0.5-200 nanometers, such as 1-150 nanometers, or 2-120 nanometers, or 3-100 nanometers, or 4-80 nanometers, or 5-70 nanometers, or 6-60 nanometers, or 7-50 nanometers, or 8-40 nanometers, or the average pore size of the microporous structure can be within the numerical range obtained by combining any two of the above end values. In the present invention, "silicon-aluminum ratio" is a parameter used to characterize the element composition ratio in the zeolite molecular sieve, especially the ratio of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron structure; Specifically, the silicon-aluminum ratio is the molar ratio of silicon and aluminum in the zeolite molecular sieve (Si:Al molar ratio). According to another embodiment, the silicon-aluminum ratio of the zeolite molecular sieve can be 45:1 to 60:1, for example 48:1 to 58:1, or 50:1 to 57:1, or 52:1 to 56:1, or 54:1 to 55:1, or the silicon-aluminum ratio can be within the numerical range obtained by combining any two of the above end values.

[0019] The rare earth element is introduced into the zeolite molecular sieve by in-situ introduction of a certain amount of rare earth element during the synthesis process. The rare earth element can be selected from at least one of the following: yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium; preferably, the rare earth element is praseodymium, samarium, or a combination of praseodymium and samarium. According to one embodiment of the present application, when the rare earth elements in the zeolite molecular sieve include both praseodymium and samarium, the weight ratio of praseodymium to samarium can be Pr:Sm=1:20 to 20:1, or 1:15 to 15:1, or 1:12 to 12:1, or 1:10 to 10:1, or 1:8 to 8:1, or 1:6 to 6:1, or 1:5 to 5:1, or 1:4 to 4:1, or 1:3 to 3:1, or 1:2 to 2:1, or 1:1 to 2:3, or the weight ratio of praseodymium to samarium can be within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, the rare earth elements do not include gadolinium. According to another embodiment of the present application, the rare earth elements do not include gadolinium in combination with any other rare earth elements.

[0020] According to another embodiment of the present application, based on the weight of the zeolite molecular sieve catalyst, the content of rare earth elements in the zeolite molecular sieve catalyst is greater than 0 weight % and less than or equal to 0.017 weight %, for example, it can be 0.001 weight % to 0.016 weight %, or 0.002 weight % to 0.015 weight %, or 0.003 weight % to 0.014 weight %, or 0.004 weight % to 0.013 weight %, or 0.005 weight % to 0.012 weight %, or 0.006 weight % to 0.011 weight %, or 0.007 weight % to 0.010 weight %, or 0.008 weight % to 0.009 weight %, or can be within the numerical range obtained by combining any two of the above end values.

[0021] Figure 1 A flow chart showing a method for synthesizing the zeolite molecular sieve catalyst according to one embodiment of the present application is shown as follows: Figure 1 As shown, the method comprises steps (a) to (d). In step (a), a silicon source, an aluminum source, a rare earth element source, a template, a pH regulator and a solvent are mixed to form a raw material mixture.

[0022] According to one embodiment of the present application, the silicon source may include at least one selected from the following: sodium silicate, water glass, silicic acid, silica gel, silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, tetraisopropyl orthosilicate, tetra-n-butyl orthosilicate, tetraisobutyl orthosilicate, etc., or a combination of the above silicon sources. According to a preferred embodiment of the present application, the silicon source may be silica sol, which is a dispersion of nanometer-sized silica particles in water or solvent, preferably a dispersion in water. According to an exemplary embodiment, based on the total weight of the silica sol, the silicon content calculated as SiO2 may be 20-50% by weight, for example, 25-45% by weight, or 30-40% by weight, or 35-40% by weight, or the silicon content calculated as SiO2 may be within the numerical range obtained by combining any two of the above end values.

[0023] According to another embodiment of the present application, the aluminum source may include an inorganic aluminum source or an organic aluminum source, for example, may include at least one selected from the following: aluminum sulfate, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum phosphate, alum (potassium aluminum sulfate dodecahydrate), aluminum formate, aluminum acetate, aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum isobutoxide, aluminum sec-butoxide, or a combination of the above aluminum sources. According to a preferred embodiment of the present application, the aluminum source may be aluminum sulfate, which may be mixed with other raw materials in the form of a solid or aqueous solution to form the raw material mixture.

[0024] According to another embodiment of the present application, the template may include alkyl ammonium halides, alkyl phosphonium halides, organic amines, etc., for example, at least one selected from the following: diethylamine, hexamethylenediamine, 1-ethylpyridinium bromide, 1-ethylpyridinium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylphosphonium bromide, hexadecyltrimethylphosphonium chloride, lauryltrimethylammonium bromide, lauryltrimethylammonium chloride, and a mixture of two or more of the above templates. According to another embodiment of the present application, based on the total weight of the raw material mixture, the content of the template may be greater than 0% by weight to less than or equal to 4.2% by weight, for example, 0.1-4.0% by weight, or 0.5-3.5% by weight, or 1.0-3.0% by weight, or 1.5-2.5% by weight, or 1.6-2.0% by weight, or the content of the template may be within the numerical range obtained by combining any two of the above endpoints.

[0025] According to one embodiment of the present application, a pH regulator may be included in the raw material mixture as needed to adjust the raw material mixture to a desired pH range, for example, to adjust the pH range to 7 to 14, for example, the pH range of the raw material mixture may be 8-13, or 9-12, or 10-11, or the pH range of the raw material mixture may be within the numerical range obtained by combining any two of the above endpoints. Examples of pH regulators may include various inorganic acids, organic acids, or mixtures thereof, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, formic acid, acetic acid; and may also include various inorganic bases, organic bases, or mixtures thereof, such as sodium hydroxide, potassium hydroxide, ammonia water, urea.

[0026] According to one embodiment of the present application, the raw material mixture may further contain water or other organic solvents as required, preferably the raw material mixture contains only water without using organic solvents. Water suitable for the present application may be selected as required, such as tap water, distilled water, redistilled water, deionized water, etc.

[0027] According to one embodiment of the present application, the components in the raw material mixture have the following molar ratios calculated based on the molar ratios of the components: Al2O3 / SiO2 / rare earth element / template / pH adjuster / water=1:30-150:0.01-0.05:10-50:150-350:3000-4000. According to an exemplary embodiment, the molar ratio of Al2O3 to SiO2 here can be 1:40-140, for example, 1:50-120, or 1:60-100, or 1:70-80, or 1:90-120, or within the numerical range obtained by combining any two of the above end values. According to another exemplary embodiment, the molar ratio of rare earth element to Al2O3 here can be 0.01-0.05:1, for example, 0.02-0.04:1, or 0.03-0.035:1, or within the numerical range obtained by combining any two of the above end values. According to another exemplary embodiment, the molar ratio of the template to Al2O3 can be 10-50:1, such as 20-40:1, or 30-35:1, or within the numerical range obtained by combining any two of the above end values. According to another exemplary embodiment, the molar ratio of the pH regulator to Al2O3 can be 150-350:1, such as 180-300:1, or 200-250:1, or within the numerical range obtained by combining any two of the above end values. According to another exemplary embodiment, the molar ratio of water to Al2O3 can be 3200-3800:1, such as 3300-3600:1, or 3400-3500:1, or within the numerical range obtained by combining any two of the above end values. It is known in the field of zeolite molecular sieves that the water described herein includes water generated in various ways, such as added pure water, water in an aqueous solution, water in a gel or sol, crystal water in a raw material, water generated by any reaction between the components, etc. It should be noted here that it is known in the field of zeolite molecular sieves that the molar ratio of each component used in the raw material mixture may be different from the molar ratio of the corresponding elements in the obtained zeolite molecular sieve product. This is because during the hydrothermal synthesis process, not all raw materials (such as silicon, aluminum, rare earth elements) can be completely introduced into the framework of the zeolite molecular sieve. However, the inventors of the present application have determined through extensive research that by controlling the content of various raw materials in the raw material mixture within the above-mentioned ratio range, the obtained zeolite molecular sieve can have the desired silicon-aluminum ratio and rare earth element content.

[0028] According to one embodiment of the present application, the raw material mixture mainly comprises the aluminum source, silicic acid, a rare earth element source, a template, a pH adjuster and water; for example, it is composed of the aluminum source, silicon source, a rare earth element source, a template, a pH adjuster and a solvent. Accordingly, according to one embodiment of the present application, the zeolite molecular sieve is mainly composed of silicon oxide, aluminum oxide and rare earth element oxide, or is completely composed of silicon oxide, aluminum oxide and rare earth element oxide.

[0029] According to one embodiment of the present application, various raw materials can be mixed together in any desired order to form the raw material mixture. According to another embodiment of the present application, a silicon source is added to water to form material A, and an aluminum source is independently added to water to form an aluminum source dispersed in water, and then a pH regulator, a rare earth element source and a template are added to the aluminum source dispersed in water to form material B, and then material A is mixed with material B under stirring conditions (e.g., mild, medium or vigorous stirring conditions), for example, material A is added to material B under stirring conditions, or material B is added to material A under stirring conditions, or material A and material B are added to the same container at the same time under stirring conditions to form the raw material mixture. According to another embodiment of the present application, the raw material mixture can also be stirred at a temperature range of room temperature to 50°C to form a gel.

[0030] like Figure 1As shown, in step (b), the raw material mixture obtained in step (a) is transferred to a hydrothermal reactor for hydrothermal treatment. According to the specific raw materials and operating process used in step (a), the raw material mixture here can be in the form of a solution, a dispersion, a suspension or a gel. The hydrothermal reactor is known in the art and is a sealed high temperature and high pressure reactor, for example, it can be a stainless steel reactor with a polytetrafluoroethylene liner, after the raw material mixture is transferred therein, the hydrothermal reactor is sealed. The hydrothermal treatment is treated under hydrothermal conditions, for example, the heating temperature is 100-220°C, or 120-200°C, or 140-200°C, or 140-180°C, or 150-170°C, or 160-170°C, or the heating temperature can be within the numerical range obtained by combining any two of the above end values. The duration of the hydrothermal treatment can be 10-100 hours, for example 12-90 hours, or 15-80 hours, or 20-70 hours, or 24-60 hours, or 24-48 hours, or the duration of the hydrothermal treatment can be within the numerical range obtained by combining any two of the above end values. In the hydrothermal treatment process, the silicon and aluminum in the raw material spontaneously combine to form a zeolite molecular sieve with a microporous structure under the action of the template, and at the same time, rare earth elements are introduced into the skeleton structure of the zeolite molecular sieve, or rare earth elements are deposited in the pores of the zeolite molecular sieve, or rare earth elements are deposited on the surface of the zeolite molecular sieve, or any combination of two or three of the above situations. Solid materials are obtained by hydrothermal synthesis, and the solid materials already have the structure of zeolite molecular sieves. After the hydrothermal synthesis is completed, the hydrothermal reactor is cooled to room temperature, the materials therein are taken out, and the solid materials are retained after filtering.

[0031] like Figure 1 As shown, in step (c), the solid material obtained in step (b) is calcined to obtain a zeolite molecular sieve catalyst precursor. According to one embodiment of the present application, the calcination can be carried out in any suitable heating equipment, such as a muffle furnace, a tubular furnace, etc., and the calcination can be carried out in a suitable atmosphere, such as an air atmosphere, an oxygen atmosphere, a nitrogen atmosphere, an inert gas atmosphere, a reduced pressure condition, etc. The calcination temperature can be 500-650°C, for example, the calcination temperature can be 520-620°C, for example, 550-600°C, or 560-580°C, or within the numerical range obtained by combining any two of the above end values. The duration of calcination can be 8-30 hours, for example, 10-25 hours, or 12-24 hours, or 14-20 hours, or 16-18 hours, or the duration of calcination can be within the numerical range obtained by combining any two of the above end values.

[0032] like Figure 1As shown, in step (d), the zeolite molecular sieve catalyst precursor obtained in step (c) is subjected to ion exchange, for example, the zeolite molecular sieve catalyst precursor can be immersed in an acidic solution, and optionally stirred to replace the ions (such as metal cations, ammonium cations, etc.) on the surface of the zeolite molecular sieve with hydrogen ions. The acidic solution for ion exchange can be selected from at least one of the solutions of the following substances: phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonium chloride, formic acid, acetic acid, propionic acid, oxalic acid, sulfonic acid. The ion exchange can be performed once or repeated twice or more times, such as three times, four times, five times, six times or seven times, etc. For the case of performing multiple ion exchanges, after each ion exchange, the solid is separated from the acidic solution by conventional filtration or suction filtration, and then added to a new acidic solution to start the next ion exchange.

[0033] Optionally, after the ion exchange is completed, the ion-exchanged solid can also be subjected to secondary calcination, and the secondary calcination can be carried out in any suitable heating equipment, such as a muffle furnace, a tubular furnace, etc., and the calcination can be carried out in a suitable atmosphere, such as an air atmosphere, an oxygen atmosphere, a nitrogen atmosphere, an inert gas atmosphere, a reduced pressure condition, etc. The temperature of the secondary calcination can be 500-650°C, for example, the secondary calcination temperature can be 520-620°C, for example, 550-600°C, or 560-580°C, or within the numerical range obtained by combining any two of the above end values. The duration of calcination can be 8-30 hours, for example, 10-25 hours, or 12-24 hours, or 14-20 hours, or 16-18 hours, or the duration of calcination can be within the numerical range obtained by combining any two of the above end values.

[0034] After the above step (d), the zeolite molecular sieve catalyst of the present invention is obtained.

[0035] According to one embodiment of the present application, the zeolite molecular sieve catalyst of the present invention can be used as a catalyst for catalytic isomerization of a raw material containing a linear unsaturated carboxylic acid to prepare an isomerized saturated carboxylic acid, the method comprising the following steps:

[0036] (A) isomerizing the linear unsaturated carboxylic acid in the raw material in a reaction system containing the catalyst described in the present application to obtain an isomerized intermediate;

[0037] (B) hydrogenating the isomerized intermediate obtained in step (A) to obtain the isomerized saturated carboxylic acid.

[0038] According to one embodiment of the present application, the straight-chain unsaturated carboxylic acid is a C12-C22 straight-chain unsaturated carboxylic acid, such as a C14-C20 straight-chain unsaturated carboxylic acid, or a C16-C18 straight-chain unsaturated carboxylic acid. According to another embodiment of the present application, the above-mentioned straight-chain unsaturated carboxylic acid has at least one carbon-carbon double bond (C=C) and at least one carboxyl group, for example, contains one, two, three, four or more carbon-carbon double bonds (C=C) and a carboxyl group, preferably contains one or two carbon-carbon double bonds (C=C) and a carboxyl group. According to another embodiment of the present application, the isomerized saturated carboxylic acid is a C12-C22 branched saturated carboxylic acid, such as a C14-C20 branched saturated carboxylic acid, or a C16-C18 branched saturated carboxylic acid. The "branched saturated carboxylic acid" contains one, two, three, four, five, six, seven or eight alkyl side chains connected to the main chain, such as C1-C6 alkyl side chains, or C1-C4 alkyl side chains, or C1-C3 alkyl side chains, or C1-C2 alkyl side chains.

[0039] Oleic acid usually inevitably contains some impurity components containing multiple unsaturated carbon-carbon double bonds, such as linoleic acid (whose carbon chain contains two carbon-carbon double bonds), etc. The catalytic process of the prior art usually requires the raw material to have a very high oleic acid purity, and the components such as linoleic acid present as impurities in the raw material will have a significant negative impact on the efficiency of the isomerization reaction and the quality of the product, resulting in the raw material with low oleic acid purity being unsuitable for use in the prior art. Different from this, the present invention uses the catalyst of the present application in the isomerization catalytic reaction, which can simultaneously make oleic acid and organic acids (such as linoleic acid) containing multiple unsaturated carbon-carbon double bonds present as impurity components can also be effectively isomerized to produce the desired branched saturated carboxylic acid (isomerized stearic acid) product, so in general, the method of the present application can use oleic acid with lower purity as a raw material to prepare the desired branched saturated carboxylic acid (isomerized stearic acid) product, while also being able to achieve excellent catalytic performance and the quality of the branched saturated carboxylic acid (isomerized stearic acid) product.

[0040] According to a preferred embodiment, the content (purity, by weight) of the straight-chain single carbon-carbon ethylenically unsaturated carboxylic acid (e.g., oleic acid) in the raw material used can be as low as 90%, for example, as low as 85%, or as low as 80%, or as low as 70%, or as low as 60%. For example, the content (purity, by weight) of the straight-chain single carbon-carbon ethylenically unsaturated carboxylic acid (e.g., oleic acid) in the raw material can be 60-99%, or 65-98%, or 68-97%, or 70-95%, or 70-92%, or 70-91%, or 70-86%, or 70-82%, or 70-78%, or 70-76%, or 70-74%, or a numerical range obtained by combining any two of the above end values. within; the achieved straight-chain single carbon-carbon olefinic unsaturated carboxylic acid conversion rate (calculated by weight ratio) can be at least 90%, or at least 92%, or at least 94%, for example 94.5-95.6%; the target product (branched saturated carboxylic acid) selectivity (calculated by weight ratio) can be at least 80%, or at least 82%, or at least 84%, or at least 85%, or at least 86%, or at least 87%, or at least 87.5%, for example 87.5-89.13%; the target product (branched saturated carboxylic acid) yield (calculated by weight ratio) can be at least 76%, or at least 78%, or at least 80%, or at least 81%, or at least 82%, or at least 83%, for example 83.15-85.20%. According to one embodiment of the present application, the raw materials used may also contain a small amount of straight-chain di-carbon-carbon ethylenically unsaturated carboxylic acid (such as linoleic acid). Based on the total weight of the raw materials, the content of straight-chain di-carbon-carbon ethylenically unsaturated carboxylic acid (such as linoleic acid) can be ≤2% by weight, or ≤4% by weight, or ≤6% by weight, or ≤8% by weight, or ≤10% by weight, or ≤12% by weight, or ≤14% by weight, or ≤16% by weight, or ≤18% by weight, or ≤20% by weight, or can be within the numerical range obtained by combining any two of the above end values.

[0041] In the following content of the application, the application of the catalyst of the application in the isomerization reaction of straight-chain unsaturated carboxylic acid is described as an example with oleic acid (C18:1, i.e., a straight-chain unsaturated carboxylic acid containing 18 carbon atoms, a carboxyl group and a carbon-carbon double bond), and as mentioned above, a small amount of linoleic acid is inevitably contained in the raw material containing oleic acid. The corresponding product obtained is isomerized stearic acid (i.e., branched stearic acid, C18:0, which is a branched saturated carboxylic acid with 18 carbon atoms and a carboxyl group, not containing a carbon-carbon double bond). But this is only an exemplary explanation, and the reactant and product type used by the catalyst of the application are not limited to this, but are applicable to all straight-chain unsaturated carboxylic acid raw materials and branched saturated carboxylic acid products described above. In the present invention, what described "isomerized stearic acid" and "branched stearic acid" represent is the combination of all stearic acid isomers with branched alkyl (alkyl side chain) structure.

[0042] For example Figure 2 The schematic diagram of the reaction process of catalyzing the isomerization reaction of oleic acid in a raw material containing oleic acid using the rare earth-zeolite molecular sieve catalyst of the present invention according to one embodiment of the present application is shown. Figure 2 As shown, oleic acid is a straight-chain aliphatic monocarboxylic acid containing a carbon-carbon double bond. Under the catalytic action of the rare earth-zeolite molecular sieve catalyst of the present invention, the oleic acid in the raw material undergoes an isomerization reaction under the catalytic reaction conditions to generate isomerized intermediates with various carbon chain connection structures. In addition, as mentioned above, a small amount of linoleic acid contained in the raw material also undergoes an isomerization reaction under the catalytic action of the catalyst to generate an isomerized intermediate as the target product. Without wishing to be limited to any specific theory, depending on the reaction conditions, these isomerized intermediate molecules may be a mixture of saturated or unsaturated branched C18 aliphatic carboxylic acids containing various branched structures. The isomerized intermediate molecules are then hydrogenated to saturate the unsaturated bonds therein, thereby obtaining the target product "isomerized stearic acid" (branched stearic acid). Figure 2 The molecular structure of an isomerized stearic acid is shown in FIG. 1 , which has a large number of branched structures, but as mentioned above, Figure 2 What is shown is merely an exemplary structure of isomerized stearic acid, and the product may actually contain a variety of other branched structures of "isomerized stearic acid" (branched stearic acid).

[0043] According to one embodiment of the application, the isomerization reaction is carried out in an autoclave reactor, for example, an autoclave reactor made of stainless steel or other suitable materials can be used. According to one embodiment of the application, the reaction is carried out under an inert atmosphere, for example, under a nitrogen atmosphere. According to one embodiment of the application, a raw material containing oleic acid and a catalyst of the present invention are added to the reactor, and the reactor is carried out at an elevated temperature. According to another embodiment of the application, water can also be optionally added to the reactor. According to one embodiment of the application, based on the total weight of all materials added in the reactor, the amount of the catalyst added can be 0.5-8% by weight, for example, 0.8-7% by weight, or 1-6% by weight, or 2-5% by weight, or 3-4% by weight, or can be within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, based on the total weight of all materials added in the reactor, the total amount of the added oil raw materials (including linear unsaturated carboxylic acids and other oils and impurities) can be 88-99.5% by weight, for example, 89-99% by weight, or 90-98% by weight, or 91-97% by weight, or 92-96% by weight, or 93-95% by weight, or 94-95% by weight, or within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, based on the total weight of all materials added in the reactor, the amount of water added can be 0-5% by weight, for example, 0.1-4.8% by weight, or 0.2-4.6% by weight, or 0.5-4% by weight, or 0.8-3.5% by weight, or 1-3% by weight, or 1.5-2.5% by weight, or 1.8-2% by weight, or within the numerical range obtained by combining any two of the above end values. The reaction temperature can be 200-300°C, for example 210-290°C, or 220-280°C, or 230-270°C, or 240-260°C, or 240-250°C, or the reaction temperature can be within the numerical range obtained by combining any two of the above end values. The duration of the catalytic reaction can be 2-48 hours, or 3-36 hours, or 4-30 hours, or 5-24 hours, or 6-18 hours, or 7-12 hours, or 8-10 hours, or the duration of the catalytic reaction can be within the numerical range obtained by combining any two of the above end values.According to one embodiment of the present application, during the reaction process, the pressure in the reactor is maintained at about 0.2-2 MPa, for example, 0.3-1.8 MPa, or 0.4-1.5 MPa, or 0.5-1.2 MPa, or 0.6-1.1 MPa, or 0.7-1 MPa, or 0.8-0.9 MPa, or the pressure in the reactor can be within the numerical range obtained by combining any two of the above end values.

[0044] According to one embodiment of the present application, after the isomerization reaction is completed, the crude product is filtered, and the obtained product is further subjected to hydrogenation and an optional purification step to obtain the desired product isostearic acid (branched stearic acid).

[0045] The present application is described below in the form of specific examples, and its purpose is to better understand the content of the present application. It should be understood that these examples are merely illustrative and non-restrictive. The reagents used in the examples are conventionally purchased from the market unless otherwise specified. The methods and conditions used in the examples are conventional methods and conditions unless otherwise specified.

[0046] Example

[0047] The water used in the following examples is distilled water, the silica sol used is a commercially available silica sol with a SiO2 weight content of 40 weight percent, and the other chemical reagents used in the following examples are all chemically pure and were purchased from suppliers and used directly without further treatment.

[0048] Synthesis Example 1: Synthesis of Zeolite Molecular Sieve Catalyst Containing Samarium

[0049] 21.28g silica sol (SiO2 content 40 wt%) was dissolved in 36.8g deionized water to form material A, aluminum sulfate was dissolved in water, and 1M KOH aqueous solution, 1M samarium nitrate aqueous solution and 1,6-hexanediamine template were added thereto in sequence to form material B, material A was slowly added dropwise to material B under vigorous stirring, and stirred at room temperature for 1.5 hours to form a raw material mixture in a gel state. The molar ratio of various materials in the mixture is as follows: Al2O3 / SiO2 / samarium element / template / KOH / water = 1:48.5:0.03:29:279:3375.

[0050] The raw material mixture in the gel state is transferred to a high-pressure hydrothermal autoclave with a tetrafluoroethylene liner, which is sealed and placed in a heating oven and heated at 160°C for 48 hours. After the reaction is completed, the temperature of the hydrothermal autoclave is lowered to room temperature, the hydrothermal autoclave is opened, the material therein is removed, and the solid is collected by filtration. The solid is calcined at 550°C in a muffle furnace for 15 hours, and the calcined solid is added to a 1M ammonium chloride aqueous solution at a ratio of 1:20 (solid: liquid weight ratio), stirred for 1 hour, and then filtered to recover the solid. The above process is repeated twice to complete the ion exchange process.

[0051] The solid that has undergone ion exchange is dried in an oven at 120° C. for 12 hours, and then calcined again in a muffle furnace at 550° C. for 2 hours to obtain the zeolite molecular sieve catalyst of the present invention, referred to as Sm-catalyst, having a silicon-aluminum ratio of 48.5: 1. The Sm content in the catalyst is determined to be 0.012% by weight by elemental analysis.

[0052] Synthesis Example 2: Synthesis of Zeolite Molecular Sieve Catalyst Containing Praseodymium

[0053] 21.28g silica sol (SiO2 content 40 wt%) was dissolved in 36.8g deionized water to form material A, aluminum sulfate was dissolved in water, and 1M KOH aqueous solution, 1M praseodymium nitrate aqueous solution and 1,6-hexanediamine template were added thereto in sequence to form material B, material A was slowly added dropwise to material B under vigorous stirring, and stirred at room temperature for 1.5 hours to form a raw material mixture in a gel state. The molar ratio of the materials in the mixture is as follows: Al2O3 / SiO2 / praseodymium element / template / KOH / water = 1:48.5:0.03:29:279:3375.

[0054] The raw material mixture in the gel state is transferred to a high-pressure hydrothermal autoclave with a tetrafluoroethylene liner, which is sealed and placed in a heating oven and heated at 160°C for 48 hours. After the reaction is completed, the temperature of the hydrothermal autoclave is lowered to room temperature, the hydrothermal autoclave is opened, the material therein is removed, and the solid is collected by filtration. The solid is calcined at 550°C in a muffle furnace for 15 hours, and the calcined solid is added to a 1M ammonium chloride aqueous solution at a ratio of 1:20 (solid: liquid weight ratio), stirred for 1 hour, and then filtered to recover the solid. The above process is repeated twice to complete the ion exchange process.

[0055] The solid that has undergone ion exchange is dried in an oven at 120° C. for 12 hours, and then calcined again in a muffle furnace at 550° C. for 2 hours to obtain the zeolite molecular sieve catalyst of the present invention, referred to as Pr-catalyst, having a silicon-aluminum ratio of 48.5: 1. The Pr content in the catalyst is determined to be 0.012% by weight by elemental analysis.

[0056] Comparative Synthesis Example 1

[0057] In this comparative synthesis example, the steps of Synthesis Example 1 were repeated, with the only difference being that the Sm element was replaced with an equimolar amount of Fe(NO3)3, and the obtained catalyst was recorded as Fe-catalyst.

[0058] Comparative Synthesis Example 2

[0059] In this comparative synthesis example, the steps of Synthesis Example 1 were repeated, except that the Sm element was replaced with an equimolar amount of Co(NO3)2, and the obtained catalyst was recorded as Co-catalyst.

[0060] Comparative Synthesis Example 3

[0061] In this comparative synthesis example, the steps of Synthesis Example 1 were repeated, except that the Sm element was replaced with an equimolar amount of Gd(NO3)3, and the obtained catalyst was recorded as Gd-catalyst.

[0062] Catalytic Reaction Examples 1-3 and Catalytic Reaction Comparative Examples 1-8:

[0063] In the following catalytic reaction examples 1-3 and catalytic reaction comparative examples 1-8, the catalytic reaction of oleic acid isomerization was carried out using the following steps, using different catalysts and raw materials of different oleic acid purities:

[0064] The isomerization catalytic step is carried out in the following manner: 120 g of oleic acid raw material, 4.8 g of catalyst and 2.4 g of water are added at one time to a 250 ml stainless steel high-pressure reactor equipped with a paddle stirrer, the air in the reactor is replaced with nitrogen three times, and then the reactor is sealed, the paddle stirrer is started for stirring, the temperature of the reactor is gradually increased to 270°C, and the reaction is continued at this temperature for 7 hours. During the reaction, the reaction pressure in the reactor is maintained at about 0.8 MPa using a pressure gauge and a pressure relief valve installed on the reactor.

[0065] After the reaction was completed, all the materials in the reactor were poured out, the solids were removed by suction filtration, and the liquid phase was collected.

[0066] The hydrogenation step was then carried out in the following manner: into a 250 ml stainless steel high-pressure reactor, 100 g of the collected liquid phase and 2 g of the catalyst were added, the reactor was sealed, the air in the reactor was replaced with nitrogen three times, and then filled with hydrogen at 2.0 MPa, a magnetic stirrer was started for stirring, the temperature of the reactor was gradually increased to 220°C, and the reaction was continued at this temperature for 5 hours. During the reaction, the reaction pressure in the reactor was maintained at 2.0 MPa using a pressure gauge and a charging valve installed on the reactor.

[0067] After the reaction is completed, all the materials in the reactor are poured out, the solid is removed by suction filtration, and the liquid phase is collected. Its composition and hydrogenation effect are determined by gas chromatography.

[0068] The collected liquid phase after the above hydrogenation was placed in a 1L beaker, placed in a low-temperature reaction tank and stirred slowly. The temperature was set to 23-30°C, and the temperature was lowered by one degree every 10 minutes to observe whether there was solid precipitation. When the solid accumulation reached a certain level, the temperature was stopped. At this time, the temperature was about 5-10°C, and the fractionation was completed. The solid was removed by suction and the liquid phase was collected. The composition and product purity were determined by gas chromatography.

[0069] According to the above characterization results, the raw material oleic acid conversion rate, target product isostearic acid selectivity and yield achieved by various catalysts of the present invention and comparative catalysts were calculated based on the following formula.

[0070] In the following formula: wulc-FA is the mass fraction of unsaturated fatty acids (oleic acid and linoleic acid) in the raw materials, 89%; wslc-FA is the mass fraction of saturated fatty acids in the raw materials, 8.43%; wdimer is the mass fraction of dimer acid in the product, %; wsbc-FA is the mass fraction of saturated fatty acids in the product, %; X is the oleic acid conversion rate, %; S is the selectivity of the reaction to produce isostearic acid, %; Y is the yield of isostearic acid, %.

[0071]

[0072]

[0073] Y=XS

[0074] The various catalysts used in the following examples were synthesized from the above Synthesis Examples 1-2 (Sm-catalyst, Pr-catalyst) and Comparative Synthesis Examples 1-3 (Fe-catalyst, Co-catalyst, Gd-catalyst). Other catalysts (ferrierite, mordenite, H-ZSM-35, β-zeolite) were purchased from Alfa Aesar (China) Chemical Co., Ltd.

[0075] The "mixed oleic acid" and "high-purity oleic acid" used in the following examples were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., wherein the oleic acid content in the mixed oleic acid is 78%, the linoleic acid content is 15%, and the rest is 7% of other low-selective impurities; the oleic acid content in the high-purity oleic acid is 93%, the linoleic acid content is 2.6%, and the rest is 4.4% of other low-selective impurities.

[0076] The catalysts, raw material information and characterization results used in the above catalytic reaction examples 1-3 and catalytic reaction comparative examples 1-8 are shown in Table 1 below:

[0077] Table 1: Characterization results of catalytic reaction examples 1-3 and catalytic reaction comparative examples 1-8

[0078]

[0079] As can be seen from the above table, whether using a raw material with high oleic acid content or a raw material with low oleic acid content, the catalyst of the present application achieves excellent raw material conversion rate, target product selectivity and yield, which is significantly better than the catalytic activity of various commercially available zeolite catalysts. In addition, it can be seen that the catalyst of the present application can achieve the above-mentioned excellent catalytic activity regardless of whether it is for a raw material with high oleic acid purity or a raw material with low oleic acid purity, which is something that the prior art has not been able to achieve so far.

[0080] In the process developed in the prior art, linoleic acid cannot generate the target isostearic acid reaction with satisfactory selectivity, so the prior art usually regards linoleic acid as a part of impurities, but in the process of the present invention, linoleic acid can also generate isostearic acid with effective selectivity. Without wishing to be limited to a specific theory, the applicant speculates that based on the catalyst system and reaction process developed by the present invention, while improving the conversion rate of oleic acid raw material and the selectivity of the target product isostearic acid, the selectivity of linoleic acid to the target product isostearic acid can also be effectively improved, so that the process of the present invention can also achieve extremely excellent product selectivity when using low oleic acid purity raw material (relatively high oleic acid content and relatively high linoleic acid content).

[0081] The above examples are only specific examples listed in this application, but the technical features of this application are not limited to them. Any simple changes, equivalent replacements or other modifications made based on this application to solve basically the same technical problems and achieve basically the same technical effects are all covered within the protection scope of this application.

Claims

1. A method for preparing an isomerized saturated carboxylic acid by catalytic isomerization of a raw material containing a linear unsaturated carboxylic acid, the method comprising the following steps: (A) in a reaction system containing a catalyst, isomerizing the linear unsaturated carboxylic acid in the raw material to obtain an isomerization intermediate, wherein the linear unsaturated carboxylic acid is C 12 -C 22 A linear unsaturated carboxylic acid, wherein the content of oleic acid is at least 60% by weight based on the total weight of the raw material; (B) hydrogenating the isomerized intermediate obtained in step (A) to obtain the isomerized saturated carboxylic acid, wherein the isomerized saturated carboxylic acid is C 12 -C 22 Branched saturated carboxylic acids; The catalyst is a zeolite molecular sieve catalyst containing rare earth elements. The rare earth element is selected from at least one of the following: yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; The content of rare earth elements is greater than 0 weight % and less than or equal to 0.017 weight % based on the weight of the zeolite molecular sieve; Calculated by the molar ratio of silicon element to aluminum element, the silicon-aluminum ratio of the zeolite molecular sieve is 45:1 to 60:

1.

2. The method according to claim 1, characterized in that: The rare earth element is praseodymium, samarium, or a combination thereof.

3. The method according to claim 1, characterized in that The straight chain unsaturated carboxylic acid is oleic acid or a mixture of oleic acid and linoleic acid, and the isomerized saturated carboxylic acid is branched stearic acid.

4. The method according to claim 1, characterized in that The catalyst is synthesized by the following steps: (a) mixing a silicon source, an aluminum source, a rare earth element source, a template, a pH adjuster and a solvent to form a raw material mixture; (b) subjecting the raw material mixture to hydrothermal treatment to obtain a solid material; (c) calcining the solid material to obtain a zeolite molecular sieve catalyst precursor; (d) performing ion exchange on the zeolite molecular sieve catalyst precursor.

5. The method according to claim 4, characterized in that The raw material mixture satisfies the following conditions: the pH adjuster adjusts the pH value of the raw material mixture to 7 to 14.

6. The method according to claim 4, characterized in that: The silicon source is selected from at least one of the following: sodium silicate, water glass, silicic acid, silica gel, silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, tetraisopropyl orthosilicate, tetra-n-butyl orthosilicate, and tetraisobutyl orthosilicate; The aluminum source is selected from at least one of the following: aluminum sulfate, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum phosphate, alum, aluminum formate, aluminum acetate, aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum isobutoxide, aluminum sec-butoxide, or a combination thereof; The rare earth element source is selected from at least one rare earth element salt of the following: nitrate, acetate, formates; The template agent is selected from at least one of the following: diethylamine, hexamethylenediamine, 1-ethylpyridinium bromide, 1-ethylpyridinium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, Hexadecyltrimethyl chloride Lauryltrimethylammonium bromide, lauryltrimethylammonium chloride, and combinations thereof.

7. The method according to claim 4, characterized in that: The hydrothermal treatment in step (b) is carried out at a temperature of 140-200° C. for 24-60 hours; The calcination in step (c) is carried out at a temperature of 500-650° C. for 15-25 hours.

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