Formic acid activated clay catalyst as well as preparation method and application thereof

Abstract

The invention provides a formic acid activated clay catalyst as well as a preparation method and application thereof. The method comprises the following steps: 1, activating clay with formic acid under a heating condition; and step 2, roasting the activated clay. The catalyst can be used for catalyzing synthesis of dimer acid through simple steps and shows extremely high catalytic activity, and the synthesized dimer acid product has extremely high yield and excellent viscosity characteristic.

Description

Technical Field

[0001] The present application relates to the fields of catalysis and oil chemical industry, and more specifically to a formic acid activated clay catalyst and a preparation method thereof, and also to the use of the catalyst for dimerizing acid products. Background Art

[0002] Dimer acid usually refers to dimer fatty acid, which is a transparent light yellow or light brown viscous liquid at room temperature, has good thermal stability, does not condense at -20°C, has certain fluidity and good transparency. It does not boil at 250°C, and gel precipitation does not occur in the system. When heated in the air, the color becomes significantly darker.

[0003] As a basic chemical raw material, dimer acid has a wide range of applications, such as additives in the synthesis of polyamide resins, synthesis of dimer acid polyester polyols and metalworking fluids. In particular, high-viscosity dimer acid has excellent performance and is extremely important in the synthesis of polyamide ink resins and in the application of metalworking fluids as corrosion inhibitors, adhesives and lubricants. People are in great need of efficiently obtaining dimer acid products with excellent properties (such as viscosity properties) with simple and low-cost processes.

[0004] The prior art dimer acid synthesis process generally comprises using raw carboxylic acid (such as oleic acid, etc.) and / or its ester as raw material, and preparing the product through catalytic dimerization reaction, wherein the catalyst used is mainly clay or modified clay. However, these prior art methods all have major defects, such as poor catalytic reaction activity of clay catalyst, clay catalyst has to be used in a large amount, clay catalyst has high oil absorption, low yield of dimer acid product and low viscosity, poor product quality and other problems.

[0005] In order to overcome the above problems, people have been conducting various research and development, trying to improve the catalysts of the existing technology or optimize the reaction process, but have not been able to obtain satisfactory results.

[0006] Therefore, there is an urgent need in the art to develop a new catalyst and reaction process for diacid catalytic reaction, which needs to be able to achieve excellent catalytic performance with simple process design and low cost, with low catalyst dosage, and the synthesized dimer acid can achieve excellent yield and excellent product performance (especially viscosity performance).

[0007] In view of the above problems in the prior art, the inventors of the present application have conducted a lot of in-depth research and developed a novel method to effectively overcome the above defects in the prior art. Summary of the invention

[0008] The first aspect of the present invention provides a method for preparing a formic acid activated clay catalyst, the method comprising:

[0009] Step 1: Activate the clay with formic acid under heating conditions;

[0010] Step 2: calcining the activated clay.

[0011] According to one embodiment of the first aspect of the present application, the clay is selected from at least one of the following: bentonite, kaolin, and montmorillonite.

[0012] According to an embodiment of the first aspect of the present application, the step 1 is performed in the following manner: forming a mixture comprising formic acid, water and clay, and heating the mixture at a temperature of 70-100° C. for 1-8 hours.

[0013] According to another embodiment of the first aspect of the present application, based on 100 parts by weight of clay, the amount of formic acid used is 6-12 parts by weight, and the amount of water used is 50-400 parts by weight.

[0014] According to another embodiment of the first aspect of the present application, in step 2, solid-liquid separation is first performed to separate the activated clay, and then calcined at a temperature of 300-600° C. for 2-12 hours.

[0015] According to another embodiment of the first aspect of the present application, the method further comprises step three: grinding the calcined clay obtained in step two into powder.

[0016] The second aspect of the present invention provides a formic acid activated clay catalyst, which is prepared by the method of the present invention.

[0017] The third aspect of the present invention provides a method for preparing dimer acid, the method comprising:

[0018] Step A: dimerizing the monomeric carboxylic acid / carboxylate raw material in the presence of a catalyst;

[0019] Step B: acidifying and separating the product mixture obtained in step A to obtain a dimer acid product;

[0020] The monomeric carboxylic acid / carboxylate raw material is a C6-C22 carboxylic acid / carboxylate containing one or more carbon-carbon unsaturated double bonds and at least one carboxyl group / ester group;

[0021] The catalyst is the formic acid activated clay catalyst of the present invention.

[0022] According to an embodiment of the third aspect of the present application, in the step A, in the presence of a catalyst, water and lithium carbonate, the monomer carboxylic acid / carboxylate raw material is subjected to a dimerization reaction, the dimerization reaction temperature is 180-320°C, the dimerization reaction duration is 1-6 hours, and the dimerization reaction pressure is 0.15-1.2MPa. According to an embodiment of the third aspect of the present application, based on 100 parts by weight of the monomer carboxylic acid / carboxylate raw material, the amount of the catalyst is 5-8 parts by weight, the amount of the water is 0.1-5 parts by weight, and the amount of the lithium carbonate is 0.05-1 part by weight.

[0023] According to one embodiment of the third aspect of the present application, in the step B, the product mixture obtained in the step A is acidified and filtered to obtain a crude dimer acid, and the crude dimer acid is subjected to a first distillation at 170-190° C. using a thin film evaporator, and the crude product obtained by the first distillation is subjected to a second distillation in a short-path evaporator at 230-235° C. to obtain a final dimer acid product.

[0024] The fourth aspect of the present invention provides a dimer acid product, which is prepared by the method of the third aspect, wherein the dimer content in the dimer acid product is ≥80%, and the viscosity of the dimer acid product is ≥8500 mPa·S.

[0025] In the specific implementation section below, the method and prepared product of the present application are further introduced in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram showing a dimer acid synthesis reaction using oleic acid as a raw material according to an exemplary embodiment of the present application is shown;

[0027] Figure 2 A schematic diagram showing another exemplary embodiment of the present application for synthesizing dimer acid using linoleic acid as a raw material. DETAILED DESCRIPTION

[0028] "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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] According to one embodiment of the present application, the catalyst for synthesizing dimer acid is a clay catalyst activated with formic acid, which can be prepared by a method comprising the following steps:

[0034] Step 1: Activate the clay with formic acid under heating conditions;

[0035] Step 2: calcining the activated clay.

[0036] According to another embodiment of the present application, the clay is selected from one or more of the following: bentonite, kaolin, and montmorillonite; preferably, the clay is bentonite or kaolin.

[0037] According to a preferred embodiment of the present application, the step 1 is performed in the following manner: a mixture comprising formic acid, water and clay is formed, and the mixture is heated for a period of time so that the clay is activated by the formic acid.

[0038] According to one embodiment of the present application, the formic acid is pure formic acid or formic acid containing a small amount of moisture or impurities, such as 85-100 wt % formic acid, preferably 90-100 wt % formic acid, and most preferably 98 wt % formic acid.

[0039] According to one embodiment of the present application, based on 100 parts by weight of clay, the amount of formic acid used is 6-12 parts by weight, preferably 8-10 parts by weight.

[0040] In the present invention, the water used to prepare the formic acid activated clay catalyst is deionized water. According to another embodiment of the present application, based on 100 parts by weight of clay, the amount of water used is 50-400 parts by weight, preferably 150-300 parts by weight, and more preferably 200-250 parts by weight.

[0041] According to one embodiment of the present application, the reaction temperature of step 1 is 70-100° C., preferably 80-90° C. According to one embodiment of the present application, the reaction duration of step 1 is 1-8 hours, preferably 2-6 hours, and more preferably 2.5-4 hours.

[0042] According to one embodiment of the present application, in step 2, the solid-liquid mixture obtained in step 1 is first subjected to solid-liquid separation, for example, by filtration, and then the activated clay obtained by separation is calcined. The calcination temperature is 300-600°C, preferably 400-500°C; the calcination duration is 2-12 hours, preferably 3-10 hours, and more preferably 4-6 hours. According to one embodiment of the present application, the calcination is carried out in an air atmosphere and under normal pressure.

[0043] According to one embodiment of the present application, after the calcination step, the calcined solid material is ground into powder to obtain the catalyst of the present invention.

[0044] The catalyst of the present invention can be used for dimerization of monomeric carboxylic acid / carboxylate raw materials, achieving excellent catalytic activity with simple reaction steps and processes, and making the dimer acid product obtained thereby have excellent properties, especially viscosity properties.

[0045] In the present invention, the monomer carboxylic acid / carboxylate raw material represents one or more carboxylic acids and / or carboxylate with carbon-carbon double bonds, preferably aliphatic carboxylic acids and / or carboxylate. According to a specific embodiment of the present application, the monomer carboxylic acid / carboxylate raw material comprises one or more C6-C22 carboxylic acids (preferably aliphatic carboxylic acids) and / or carboxylate, and contains one or more (e.g., one, two, three, four, five or six) carbon-carbon double bonds and at least one (e.g., one, two, three or four) carboxyl / carboxylate groups in each molecule. According to an embodiment of the present application, the carboxylate can be an ester formed by carboxylic acid and various alcohols, such as C1-C12 alkyl esters, and more specifically can be methyl esters, ethyl esters, propyl esters, butyl esters, ethylene glycol esters, glycerides, etc. of the above-mentioned carboxylic acids.

[0046] According to an exemplary embodiment of the present application, the monomer carboxylic acid / carboxylate raw material mainly comprises oleic acid, oleic acid ester, linoleic acid, linoleic acid ester, or a combination thereof. Taking oleic acid as an example, Figure 1Schematic diagram of the reaction mechanism of synthesizing dimer acid from monomer acid raw material (oleic acid) of the present invention is shown, wherein two oleic acid (octadecenoic acid) molecules undergo dimerization reaction under the catalytic action of the catalyst of the present invention to generate dimer (a). Figure 2 The schematic diagram of the reaction mechanism of synthesizing dimer acid from monomeric acid raw material (linoleic acid) of the present invention is shown, wherein two linoleic acid (octadecadienoic acid) molecules undergo dimerization reaction under the catalytic action of the catalyst of the present invention to generate dimers (b), (c) and (d). Figure 2 As shown, when the raw material unsaturated carboxylic acid contains two or more carbon-carbon double bonds per molecule, a cyclization reaction may occur to a certain extent in the process of forming the dimer. In this case, a part of the dimer product may contain a cyclic structure, such as a cycloalkyl group, a cycloalkenyl group, etc., but this part of the dimer containing a cyclic structure will not affect the use of the dimer product.

[0047] According to another exemplary embodiment of the present application, the monomeric carboxylic acid / carboxylate raw material is a mixture of monomeric carboxylic acids / carboxylate esters derived from vegetable oils. According to a specific exemplary embodiment of the present application, the raw material is soybean oil, wherein soybean oleic acid contains: palmitic acid: 1.0-2.9%, stearic acid: 4.1-5.0%, oleic acid: 28.1-29.9%, linoleic acid: 54.0-55.9%, linolenic acid: 1.6-3.2%, arachidic acid: 1.1-2.0%. That is to say, in this embodiment, the raw material is a mixture of multiple unsaturated fatty acids, and the corresponding product is also a mixture of multiple dimers.

[0048] According to one embodiment of the present invention, a method for preparing dimer acid comprises the following steps:

[0049] Step A: dimerizing the monomeric carboxylic acid / carboxylate raw material in the presence of the catalyst of the present invention;

[0050] Step B: Acidifying and separating the product mixture obtained in step A to obtain a dimer acid product.

[0051] According to an exemplary embodiment of the present application, the monomeric carboxylic acid / carboxylate raw material includes a C6-C22 carboxylic acid / carboxylate containing one or more carbon-carbon unsaturated double bonds (preferably one or two carbon-carbon unsaturated double bonds) and at least one carboxyl group / ester group (preferably one or two carboxyl groups or carboxylate groups), such as C10-C20 carboxylic acid / carboxylate, preferably C12-C18 carboxylic acid / carboxylate, and more preferably C16-C18 carboxylic acid / carboxylate.

[0052] According to a specific embodiment of the present application, in the step A, the monomer carboxylic acid / carboxylate raw material is subjected to a dimerization reaction in the presence of a catalyst, water and lithium carbonate.

[0053] According to one embodiment of the present application, in the step A, the amount of the catalyst is 5-8 parts by weight, preferably 6-7 parts by weight, based on 100 parts by weight of the monomer carboxylic acid / carboxylate raw material. Compared with the prior art, one of the advantages of the present invention is that a lower amount of catalyst can be used to achieve an excellent yield of the target product (dimer).

[0054] According to one embodiment of the present application, in the step A, the amount of water is 0.1-5 parts by weight, preferably 0.5-2 parts by weight, and more preferably 1-1.5 parts by weight, based on 100 parts by weight of the monomer carboxylic acid / carboxylate raw material. Without wishing to be limited to any particular theory, in the dimerization reaction, the function of water is an activating aid.

[0055] According to one embodiment of the present application, in step A, the amount of lithium carbonate used is 0.05-1 part by weight, preferably 0.1-0.5 part by weight, based on 100 parts by weight of the monomer carboxylic acid / carboxylate raw material. Without wishing to be limited to any particular theory, in the dimerization reaction, the lithium carbonate functions as a co-catalyst.

[0056] According to one embodiment of the present application, in the step A, the temperature of the dimerization reaction is 180-320°C, preferably 200-240°C.

[0057] According to one embodiment of the present application, in the step A, the duration of the dimerization reaction is 1-6 hours, preferably 2-4 hours, and more preferably 3-3.5 hours.

[0058] According to one embodiment of the present application, the dimerization reaction is carried out in a closed high-pressure reactor, and the reaction pressure in the reactor depends on the content and type of materials therein and the reaction temperature. For example, the pressure of the dimerization reaction can be 0.15-1.2 MPa, preferably 0.6-1 MPa, and more preferably 0.7-0.7 MPa.

[0059] After the dimerization reaction in step A, the reaction mixture mainly contains the product dimer (dimeric carboxylate and / or dimer carboxylic acid), and also contains unreacted monomer raw materials (monomeric carboxylic acid and / or monomeric carboxylate), by-product trimer or higher degree of polymerization polymer (for convenience, the combination of trimers or higher polymers is hereinafter referred to as "polymer", which includes polycarboxylic acid with a degree of polymerization ≥3 and / or polycarboxylate with a degree of polymerization ≥3), solid catalyst, and a small amount of other components (such as water, lithium carbonate, etc.).

[0060] Next, the reaction mixture obtained in step A is acidified so that the metal cations (such as calcium ions) combined with the carboxylate groups in the product dimer are precipitated out of the system (such as precipitated), and the carboxylate groups originally combined with the metal cations in the dimer are converted back into carboxyl groups.

[0061] After acidification, the acidified reaction mixture is subjected to solid-liquid separation, such as filtration separation, to remove solid substances therein, such as catalysts and other insoluble substances. The separated liquid phase is washed with water and centrifuged to obtain crude dimer acid.

[0062] The crude dimer acid is then subjected to one or more further purification steps, such as one or more distillation steps.

[0063] According to one embodiment of the present application, the crude dimer acid is distilled in a thin film evaporator and a short path evaporator in sequence. According to a specific embodiment of the present application, the crude dimer acid is first distilled in a thin film evaporator at a temperature of 170-190° C. to remove water and low boiling point fractions contained in the crude dimer acid. The crude product obtained by the first distillation is second distilled in a short path evaporator at 230-235° C. to obtain a final dimer acid product.

[0064] According to a preferred embodiment of the present application, compared with the prior art, the dimer acid product obtained by the method of the present invention has a much higher dimer content, for example, the dimer acid product contains ≥80% by mass of dimers, for example, the dimer content can be 80-85% by mass, preferably 80-82% by mass, based on the total mass of the dimer acid product; in addition, the content of polymers in the dimer acid product is 14-16% by mass, and the content of monomeric acid (or carboxylic ester) is 3-4% by mass.

[0065] According to another preferred embodiment of the application, compared with the prior art, the dimer acid product obtained by the method of the present invention has a much higher viscosity. For example, the viscosity (25°C) of the dimer acid product can be ≥8500mPa·S, preferably ≥8600mPa·S, and most preferably can reach above 9000mPa·S.

[0066] The method of the present invention can achieve the following advantages:

[0067] 1. The preparation process of formic acid activated clay catalyst is simple and the preparation cost is low;

[0068] 2. In the reaction of synthesizing dimer acid products, the amount of catalyst used is significantly reduced;

[0069] 3. The catalyst has excellent catalytic performance, the yield of dimer acid target product is greatly improved, and the economic benefits are significantly improved;

[0070] 4. The dimer product has excellent properties, especially has significantly improved viscosity.

[0071] In the following examples, the method of the present application is specifically described with specific examples, the purpose of which is to better understand the content of the present application. It should be understood that these examples are merely illustrative and not restrictive.

[0072] Example

[0073] The clay used in the following examples is Sun's white clay purchased from Anji Sun's Bentonite Factory; the monomer carboxylic acid / carboxylate raw material used is soybean oleic acid purchased from Fengyi Renewable Resources (Tianjin) Co., Ltd., and its main composition is palmitic acid: 2.3% by weight, stearic acid: 4.5% by weight, oleic acid: 30.4% by weight, linoleic acid: 55.8% by weight, linolenic acid: 2.4% by weight, and arachidic acid: 0.4% by weight. The other reagents used are all commercially available analytical reagents, so the water used is deionized water.

[0074] Example 1

[0075] First, 100 g of clay, 200 g of deionized water and 10 g of 98 wt% formic acid (i.e., a mixture of 98 wt% formic acid and 2 wt% deionized water) were added to a 1-liter three-necked glass flask, mixed and stirred evenly, and the flask was heated to 80° C. and stirred at this temperature for 2.5 hours. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The material in the flask was removed and filtered, and the solid was collected and calcined at 400° C. in an air atmosphere for 4 hours. The calcined solid was then ground into powder to obtain a formic acid-activated clay catalyst.

[0076] 100 g of soybean oleic acid, 6.5 g of the formic acid-activated clay catalyst obtained in the above steps, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0077] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0078] The liquid component obtained by the above steps was treated at 170-175° C. using a BWG-7 thin film evaporator produced by Nanjing Zhibote Technology Co., Ltd. to remove moisture and low-boiling fractions therein to obtain a crude product. The composition of the crude product was characterized using an Agilent 1260 Infinity high performance liquid chromatograph produced by Agilent, and the monomer acid content was measured to be 27.8% by mass, the dimer content was 60.6% by mass, and the polymeric acid content was 11.6% by mass.

[0079] The crude product was then short-path distilled at 230-235° C. in a BOG-15 molecular distillation apparatus produced by Nanjing Zhibote Technology Co., Ltd. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.6% by mass, the dimer content was 80.9% by mass, and the polymer acid content was 15.5% by mass.

[0080] The viscosity (25° C.) of the dimer acid product measured by a DVNXRV rotary viscometer produced by Brookfield Company was 9022 mPa·S.

[0081] The manufacturers and equipment models of various equipment used in the following Examples 2-3 and Comparative Examples 1-5 are as described in Example 1.

[0082] Example 2

[0083] First, 100 g of clay, 200 g of deionized water and 10 g of 98 wt% formic acid (i.e., a mixture of 98 wt% formic acid and 2 wt% deionized water) were added to a 1-liter three-necked glass flask, mixed and stirred evenly, and the flask was heated to 80° C. and stirred at this temperature for 2.5 hours. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The material in the flask was removed and filtered, and the solid was collected and calcined at 400° C. in an air atmosphere for 4 hours. The calcined solid was then ground into powder to obtain a formic acid-activated clay catalyst.

[0084] 100 g of soybean oleic acid, 5.5 g of the formic acid-activated clay catalyst obtained in the above steps, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0085] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0086] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein, thereby obtaining a crude product. The composition of the crude product was characterized by high performance liquid chromatography, and the monomer acid content, the dimer content, and the polymer acid content were found to be 28.7% by mass, 60.0% by mass, and 11.3% by mass.

[0087] The crude product was then short-path distilled in a molecular evaporator at 230-235° C. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.7% by mass, the dimer content was 81.0% by mass, and the polymer acid content was 15.3% by mass.

[0088] The viscosity (25° C.) of the dimer acid product was measured by a viscometer and found to be 8688 mPa·S.

[0089] Example 3

[0090] First, 100 g of clay, 200 g of deionized water and 12 g of 98 wt% formic acid (i.e., a mixture of 98 wt% formic acid and 2 wt% deionized water) were added to a 1-liter three-necked glass flask, mixed and stirred evenly, the flask was heated to 80° C. and stirred at this temperature for 2.5 hours. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The material in the flask was removed and filtered, and the solid was collected and calcined at 400° C. in an air atmosphere for 4 hours. The calcined solid was then ground into powder to obtain a formic acid-activated clay catalyst.

[0091] 100 g of soybean oleic acid, 6.5 g of the formic acid-activated clay catalyst obtained in the above steps, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0092] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0093] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein, thereby obtaining a crude product. The composition of the crude product was characterized by high performance liquid chromatography, and the monomer acid content, the dimer content, and the polymer acid content were found to be 28.5% by mass, 60.0% by mass, and 11.5% by mass.

[0094] The crude product was then short-path distilled in a molecular evaporator at 230-235° C. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.8% by mass, the dimer content was 80.7% by mass, and the polymer acid content was 15.5% by mass.

[0095] The viscosity (25° C.) of the dimer acid product was measured by a viscometer and found to be 8719 mPa·S.

[0096] Comparative Example 1

[0097] In this Comparative Example 1, the catalytic performance of the clay catalyst activated with an inorganic acid (sulfuric acid) was investigated.

[0098] First, 100 g of clay, 200 g of deionized water and 5 g of 98 wt% sulfuric acid (i.e., a mixture of 98 wt% sulfuric acid and 2 wt% deionized water) were added to a 1-liter three-necked glass flask, mixed and stirred evenly, and the flask was heated to 80° C. and stirred at this temperature for 2.5 hours. After the reaction was completed, the temperature was lowered to room temperature and stirring was stopped. The material in the flask was removed and filtered, and the solid was collected and calcined at 400° C. in an air atmosphere for 4 hours. The calcined solid was then ground into powder to obtain a formic acid activated clay catalyst.

[0099] 100 g of soybean oleic acid, 6.5 g of the sulfuric acid-activated clay catalyst prepared in the above steps, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0100] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0101] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein to obtain a crude product. The composition of the crude product was characterized using a high performance liquid chromatograph, and the monomer acid content, the dimer content, and the polymer acid content were measured to be 37.1% by mass, 27.3% by mass, and 35.6% by mass. It can be seen that the raw material conversion rate in this comparative example is very low, and the product dimer acid yield is also very low, and the target product yield and the preparation of a high viscosity target product cannot be achieved at all, so there is no need to further distill and test the viscosity of the product.

[0102] Comparative Example 2

[0103] In this Comparative Example 2, the catalytic performance of the clay catalyst activated with an organic acid (citric acid) was investigated.

[0104] First, 100 g of clay, 200 g of deionized water and 10 g of anhydrous citric acid were added to a 1-liter three-necked glass flask, mixed and stirred evenly, and the flask was heated to 80°C and stirred at this temperature for 2.5 hours. After the reaction was completed, the temperature was cooled to room temperature and stirring was stopped. The material in the flask was removed and filtered, and the solid was collected and calcined at 400°C in an air atmosphere for 4 hours. The calcined solid was then ground into powder to obtain a citric acid activated clay catalyst.

[0105] 100 g of soybean oleic acid, 6.5 g of the citric acid-activated clay catalyst prepared in the above steps, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0106] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0107] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein to obtain a crude product. The composition of the crude product was characterized by high performance liquid chromatography, and the monomer acid content was 34.2% by mass, the dimer content was 55.4% by mass, and the polymer acid content was 10.4% by mass.

[0108] The crude product was then short-path distilled in a molecular evaporator at 230-235° C. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.3% by mass, the dimer content was 81.4% by mass, and the polymer acid content was 15.3% by mass.

[0109] The viscosity (25° C.) of the dimer acid product was measured by a viscometer and found to be 7578 mPa·S.

[0110] Comparative Example 3

[0111] In this Comparative Example 3, the catalytic performance using unactivated clay as a catalyst was investigated.

[0112] 100 g of soybean oleic acid, 6.5 g of clay, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0113] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0114] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein to obtain a crude product. The composition of the crude product was characterized by high performance liquid chromatography, and the monomer acid content, the dimer content, and the polymer acid content were 32.2% by mass, 57.6% by mass, and 10.2% by mass.

[0115] The crude product was then short-path distilled in a molecular evaporator at 230-235° C. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.5% by mass, the dimer content was 82% by mass, and the polymer acid content was 14.5% by mass.

[0116] The viscosity (25° C.) of the dimer acid product was measured by a viscometer and found to be 7140 mPa·S.

[0117] Comparative Example 4

[0118] In this Comparative Example 4, the catalytic performance achieved when unactivated clay was used as a catalyst and formic acid was used in the catalytic reaction system was investigated.

[0119] 100 g of soybean oleic acid, 6.5 g of clay, 0.65 g of formic acid, 0.2 g of lithium carbonate and 1 g of deionized water were added to an autoclave equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the autoclave evenly. Then, the autoclave was closed, and the autoclave was heated to 240° C. and maintained at this temperature for 3 hours.

[0120] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0121] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein to obtain a crude product. The composition of the crude product was characterized using a high performance liquid chromatograph, and the monomer acid content, the dimer content, and the polymer acid content were measured to be 40.5% by mass, 30.7% by mass, and 28.8% by mass. It can be seen that the raw material conversion rate in this comparative example is very low, and the product dimer acid yield is also very low, and the target product yield and high viscosity target product cannot be achieved at all, so there is no need to further distill and test the viscosity of the product.

[0122] Comparative Example 5

[0123] In this Comparative Example 5, the catalytic performance using increasing amounts of unactivated clay as a catalyst was investigated.

[0124] 100 g of soybean oleic acid, 8 g of clay, 0.2 g of lithium carbonate and 1 g of deionized water were added to a high-pressure reactor equipped with a stirring device and a heating-temperature control device, and the stirring device was started to mix the materials in the reactor evenly. Then, the high-pressure reactor was closed, and the reactor was heated to 240° C. and maintained at this temperature for 3 hours.

[0125] After the reaction is completed, the reactor is cooled to room temperature, the reaction mass is taken out, 3 grams of phosphoric acid with a concentration of 85% by weight is added to the reaction mass and fully mixed to acidify the reaction mass. The reaction mass is then filtered using a stainless steel jacket positive pressure filter. The liquid phase obtained after filtration is washed with 50 grams of deionized water and treated using a centrifuge to remove phosphoric acid in the oil phase.

[0126] The liquid component obtained by the above steps was treated in a thin film evaporator at 170-175° C. to remove water and low boiling point fractions therein to obtain a crude product. The composition of the crude product was characterized by high performance liquid chromatography, and the monomer acid content was 30.0% by mass, the dimer content was 58.7% by mass, and the polymer acid content was 11.3% by mass.

[0127] The crude product was then short-path distilled in a molecular evaporator at 230-235° C. to obtain a dimer acid product. The composition of the dimer acid product was characterized by gas chromatography, and the monomer acid content was 3.6% by mass, the dimer content was 80.8% by mass, and the polymer acid content was 15.6% by mass.

[0128] The viscosity (25° C.) of the dimer acid product was measured by a viscometer and found to be 8039 mPa·S.

[0129] From the above experimental comparison, it can be seen that the formic acid-activated clay catalysts in all the embodiments of the present invention achieve excellent yields of the target product dimer with less catalyst dosage, and the dimer product has more excellent viscosity properties.

[0130] In contrast, under the same conditions, the catalytic performance of the clay catalyst treated with an inorganic acid (sulfuric acid) and an organic acid different from formic acid (citric acid) and the clay catalyst not treated with acid is significantly worse, and more importantly, the viscosity of the obtained dimer product is much lower. In addition, it can be seen from Comparative Example 5 that the yield of the target product dimer can be increased to a certain extent by increasing the amount of catalyst (untreated clay), but the viscosity of the obtained dimer product is significantly lower than the viscosity of the dimer product obtained in the embodiment of the present invention.

Claims

1. A method for preparing a formic acid activated clay catalyst, the method comprising: Step 1: Activate the clay with formic acid under heating conditions; Step 2: calcining the activated clay.

2. The method according to claim 1, characterized in that The step 1 is performed by forming a mixture comprising formic acid, water and clay, and heating the mixture at a temperature of 70-100° C. for 1-8 hours; and The clay is selected from at least one of the following: bentonite, white clay, and montmorillonite.

3. The method according to claim 1 or 2, characterized in that Based on 100 parts by weight of clay, the amount of formic acid used is 6-12 parts by weight, and the amount of water used is 50-400 parts by weight.

4. The method according to claim 1 or 2, characterized in that: In step 2, solid-liquid separation is first performed to separate the activated clay, which is then calcined at a temperature of 300-600° C. for 2-12 hours.

5. The method according to claim 1 or 2, characterized in that: The method further comprises step three: grinding the calcined clay obtained in step two into powder.

6. A formic acid activated clay catalyst prepared by the method according to any one of claims 1 to 5.

7. A method for preparing dimer acid, the method comprising: Step A: dimerizing the monomeric carboxylic acid / carboxylate raw material in the presence of a catalyst; Step B: acidifying and separating the product mixture obtained in step A to obtain a dimer acid product; The monomeric carboxylic acid / carboxylate raw material is a C6-C22 carboxylic acid / carboxylate containing one or more carbon-carbon unsaturated double bonds and at least one carboxyl group / ester group; The catalyst is the formic acid activated clay catalyst as claimed in claim 6.

8. The method according to claim 7, characterized in that In the step A, in the presence of a catalyst, water and lithium carbonate, the monomer carboxylic acid / carboxylate raw material undergoes a dimerization reaction, the dimerization reaction temperature is 180-320° C., the dimerization reaction duration is 1-6 hours, and the dimerization reaction pressure is 0.15-1.2 MPa; Based on 100 parts by weight of the monomer carboxylic acid / carboxylate raw material, the amount of the catalyst is 5-8 parts by weight, the amount of water is 0.1-5 parts by weight, and the amount of lithium carbonate is 0.05-1 part by weight.

9. The method according to claim 7, characterized in that In the step B, the product mixture obtained in the step A is acidified and filtered to obtain a crude dimer acid, and the crude dimer acid is subjected to a first distillation at 170-190° C. using a thin film evaporator, and the crude product obtained by the first distillation is subjected to a second distillation at 230-235° C. in a short-path evaporator to obtain a final dimer acid product.

10. A dimer acid product, prepared by the method according to any one of claims 7 to 9, wherein the dimer content in the dimer acid product is ≥ 80%, and the viscosity of the dimer acid product is ≥ 8500 mPa·S.

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