Preparation method and device of dimer acid
Technical Field
The invention belongs to the field of dimer acid, and particularly relates to a preparation method and device of dimer acid.
Background
Dimer acid is named because the molecule contains two carboxylic acid groups, and mainly refers to that C18 unsaturated fatty acid generates dimer acid taking C36 as a main component according to Diels-Alder reaction under certain conditions. The basic structure of dimer acids is broadly divided into three categories, depending on the reaction mechanism: monocyclic, bicyclic and acyclic. Currently, commercial dimer acids are typically mixtures of three isomers.
The dimer acid has moderate molecular weight and unique structure, has long flexible carbon chains in molecules and relatively rigid annular structures, and has polar and nonpolar groups and reactive groups with active properties such as carbonyl and double bonds. These unique molecular structures provide unique physicochemical properties and wide application, and can be used for synthesizing polyurethane resins, corrosion inhibitors in petroleum processing equipment, lubricants, fuel additives, coatings, vegetable oil stabilizers, and the like.
At present, main raw materials for producing dimer acid are tall oil acid, cotton oleic acid, soybean oleic acid and the like, and main components are linoleic acid and oleic acid. The production process of the dimer acid mainly adopts a clay catalysis method or other catalyst catalysis methods, wherein the clay catalysis method is a dimer acid synthesis method widely adopted at present. The properties of the crude dimer acid produced by these two processes are substantially the same.
Liu Xianggong takes oleic acid as raw material, under the conditions of normal pressure and nitrogen protection, the reaction temperature is 240 ℃, the reaction time is 6h, the using amount of active clay is 12% (w) of oleic acid, and the using amount of LiCl is 1.2% (w) of oleic acid, the yield of dimer acid is 34.6% (petrochemical industry, 2015, 44 (4): 483-488).
WO 00/75252 discloses a synthesis method of dimer acid, which takes C18 fatty acid as raw material, the specific components are ,0.14% C14、6.97% C16、0.27% C16:1、3.22% C18、49.71% C18:1、28.56% C18:2、7.34%C18:3、0.56% C20、1.15% C20:1、0.29%C22 and 0.18 percent of C 22:1, the dosage of calcium bentonite is 4.5 percent of the raw material, the dosage of LiCO 3 is 0.07 percent of the raw material, the dosage of water is 1.0 percent of the raw material, the nitrogen is used for protection, the reaction temperature is 254 ℃, the reaction time is 4 hours, the highest pressure of a reaction system is 219psig, and the dimer acid content of the reaction system is 50.5 percent.
CN104804782a discloses a synthesis method of dimer acid, mixed fatty acid prepared from sunflower seed oil is used as raw material, 12% active clay is added, 1% Li 2CO3 is protected by nitrogen blowing, heating temperature is 240 ℃, reaction time is 6h, and yield of dimer acid is 67.6% after subsequent treatment.
In the method, the catalyst or the catalyst auxiliary agent is required to be added in the synthesis of the dimer acid, wherein the catalyst is added in a large amount, the catalyst is powdery, the subsequent separation and purification cost is high, the product is lost in the separation process, and certain environmental pollution is caused.
CN109879745A discloses a dimer acid and its synthesis method, which uses tungstic acid as raw material, in the presence of polymerization inhibitor, stirring while nitrogen purging, heating to 180-230 deg.c for reaction, and obtaining dimer acid product after reaction. The molecular formula of the prepared dimer acid is C 34H58(COOH)2, and the content of the dimer acid in the product is more than or equal to 55 percent. The invention synthesizes dimer acid by taking tungstic acid as a raw material, does not need to use a catalyst, has relatively mild reaction conditions and simple process, and has high yield of dimer acid. However, the dimer acid content in the product is low, and the ratio of the single-ring structure is still further improved.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method and a device of dimer acid. The product prepared by the invention has higher content of dimer acid, especially the proportion of single-ring structure is higher than 80%.
The preparation method of dimer acid provided by the invention comprises the following steps:
Adding eleostearic acid into a reactor, introducing nitrogen for purging, and preheating the eleostearic acid into liquid; the reactor is internally provided with atomizing equipment and an external circulation pipeline, the external circulation pipeline is provided with a metering pump, the metering pump is started, tungstic acid is atomized and then reacts at 160-200 ℃, and then returns to the atomizing equipment to carry out circulation reaction through the external circulation pipeline, so that a dimer acid product is finally prepared.
In the invention, the tung acid can be commercial tung acid or self-made tung acid, the iodine value of the tung acid is 140-160g/100g, and the acid value is 150-200mgKOH/g. The preparation process of the self-made eleostearic acid comprises the following steps: mixing tung oil with alkali, alcohol and water, performing homogeneous saponification to remove glycerol to generate fatty acid salt, acidifying the fatty acid salt, preserving heat for a certain time, distilling under reduced pressure to remove alcohol, extracting oil phase, washing the oil phase with water, distilling under reduced pressure to remove extractant and a small amount of water, and obtaining tung oleic acid.
In the invention, the nitrogen purging time is 1-30min, preferably 20-30min.
In the invention, the temperature of the preheating reactor in the nitrogen purging process is more than 55 ℃, so that the tungstic acid is ensured to be in a liquid state.
In the invention, the reaction temperature of the reactor is controlled to be 160-200 ℃, preferably 160-180 ℃ and the reaction time is controlled to be 1-10h, preferably 2-3h in the reaction process.
In the present invention, the atomizing device provided in the reactor may be a conventional device capable of effecting atomization of a liquid, such as an atomizer, a jet nozzle, or the like.
In the invention, the metering pump is arranged on the outer circulation pipeline, and the metering pump is started to realize the circulating flow of the materials in the reactor.
In the invention, the heat exchanger is arranged on the outer circulation pipeline, and the heat exchanger is started to supplement the heat loss in the material circulation process.
In the invention, the three-way valve is arranged on the outer circulation pipeline, so that liquid can be discharged according to the requirement.
In the invention, further, alkyl quaternary ammonium salt and lithium-containing compound are added into tung oil acid raw material, and the mass ratio of the alkyl quaternary ammonium salt to the lithium-containing compound is 1-3:1. The alkyl quaternary ammonium salt is at least one of tetradecyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride and the like. The lithium-containing compound is at least one of lithium carbonate, lithium chloride, lithium hydroxide, and the like.
In the invention, the total dosage of the alkyl quaternary ammonium salt and the lithium-containing compound is 0.1-1.0% of the mass of eleostearic acid, preferably 0.1-0.5%.
The dimer acid of the present invention is synthesized by the method of the present invention described above. In the synthesized product, the content of tung oil dimer acid is more than or equal to 80%, wherein the proportion of the single-ring structure is more than 79%.
The invention also provides a preparation device for the dimer acid preparation method, which mainly comprises a reactor main body and an external circulation pipeline, wherein an atomization device is arranged in the reactor, the external circulation pipeline is provided with a metering pump and a heat exchanger through the atomization device, the metering pump is started, and tungstic acid reacts at 160-200 ℃ after passing through the atomization device and returns to the atomization device through the external circulation pipeline for circulation reaction.
Compared with the prior art, the invention has the following advantages:
(1) In the test process of preparing dimer acid, the inventor discovers that eleostearic acid can prepare dimer acid in the presence of no catalyst because of the unique structure of eleostearic acid is different from other vegetable oleic acid, but a polymerization inhibitor is needed to control the reaction, the yield of the product dimer acid is not high, and the single-ring structure ratio is not high. In order to improve the yield of dimer acid and the duty ratio of dimer acid with a single-ring structure, the inventor atomizes the raw materials and carries out the cyclic reaction, so that the effective dispersion and the efficient reaction of the eleostearic acid can be realized, the cross-linking polymerization of the eleostearic acid can be reduced under the condition of no polymerization inhibitor, and meanwhile, the oleic acid and the linoleic acid in the raw materials also participate in the reaction, so that the yield of the dimer acid is further improved.
(2) Alkyl quaternary ammonium salt and lithium-containing compound are added into the preparation raw material simultaneously, so that the content of C36 unsaturated fatty acid dimer acid in the product is improved, the content can be higher than 85%, and the improvement of the single ring structure is beneficial to improving the rust resistance of the product.
(3) The tung oil acid is used as a raw material to prepare the dimer acid, and is used as a conjugated diene body and a parent conjugated diene body, a catalyst is not needed in the preparation process, the reaction condition is relatively mild, the yield of the dimer acid is high, and the preparation process is environment-friendly.
Drawings
FIG. 1 is a schematic view of a production apparatus of the present invention;
Wherein, 1-reactor, 2-atomizing equipment, 3-thermometer, 4-manometer, 5-feed inlet and N2 export, 6-measuring pump, 7-heat exchanger, 8-N 2 entry, 9-leakage fluid dram, 10-three-way valve.
Detailed Description
The process and effect of the present invention for preparing dimer acid will be further illustrated by the following examples. The embodiment is implemented on the premise of the technical scheme of the invention, and detailed implementation modes and specific operation processes are given, but the protection scope of the invention is not limited to the following embodiment.
The experimental methods in the following examples, unless otherwise specified, are all conventional in the art. The experimental materials used in the examples described below, unless otherwise specified, were purchased from conventional biochemical reagent stores.
The content of dimer acid and trimer acid in the sample is measured by GPC, and the specific chromatographic conditions are as follows: shodex KF-801 gel chromatographic column, column temperature 35 ℃, mobile phase tetrahydrofuran, flow rate 1mL/min, differential detector, detector temperature 40 ℃ and sample injection amount 10 μl.
The content of the monocyclic dimer acid in the dimer acid is determined by a gas chromatograph-mass spectrometer, and the type of equipment and analysis conditions adopted in the test are as follows: sample preparation is referred to GB/T17376 preparation of animal and vegetable fat and fatty acid methyl ester; the instrument adopts Thermo DSQ II, and the chromatographic column adopts Aglient DB-1HT; the conditions are that the initial temperature is 170 ℃, the temperature is kept for 1min, the temperature is raised to 350 ℃ at the speed of 5 ℃/min, the temperature of a sample inlet is 260 ℃, the temperature of a detector is 280 ℃, the split ratio is 20:1, and the sample feeding amount is 1 mu L.
The preparation device adopted in the embodiment of the invention is shown in the attached figure 1, and mainly comprises a reactor 1 and an external circulation pipeline, wherein an atomization device 2 is arranged in the reactor, the external circulation pipeline is arranged through the atomization device 2, a metering pump 6 and a heat exchanger 7 are arranged on the external circulation pipeline, the metering pump 6 is started, eleostearic acid reacts at 160-200 ℃ after passing through the atomization device 2, and then returns to the atomization device through the external circulation pipeline for circulation reaction. The reactor is internally provided with a temperature meter 3 and a pressure meter 4 for monitoring the temperature and the pressure, the top of the reactor is provided with a feed inlet 5 for supplementing materials and nitrogen gas outlets, and the bottom of the reactor is provided with a nitrogen gas inlet 8. The three-way valve 10 is arranged on the outer circulation pipeline, and liquid can be discharged through the liquid outlet 9 according to the requirement.
Example 1
The eleostearic acid adopts commercial eleostearic acid, the iodine value of the eleostearic acid is 150g/100g, and the acid value is 180mgKOH/g.
Adding eleostearic acid into a reactor, introducing nitrogen, purging for 30min, and preheating to 55 ℃ to enable eleostearic acid to be liquid; the atomization equipment is a jet nozzle, a metering pump is started, tungstic acid is subjected to reaction at 200 ℃ after atomization, then is returned to the atomization equipment through an external circulation pipeline to carry out circulation reaction for 3 hours, and after the reaction is finished, a three-way valve is opened to a liquid discharge state, and dimer acid products are collected.
The dimer acid content in the product was found to be 83.4% and the single ring structure was found to be 79.0%.
Example 2
The preparation process and operating conditions were the same as in example 1 except that commercially available eleostearic acid was used, the iodine value of eleostearic acid was 140/100g, and the acid value was 200mgKOH/g.
The dimer acid content in the product was determined to be 84.0% and the single ring structure was determined to be 80.2%.
Example 3
The preparation process and the operation conditions are the same as in example 1, except that eleostearic acid is prepared by the following method: 7.8g of NaOH, 70mL of ethanol and 35mL of water are added into a 250mL three-neck flask, stirring and heating are carried out to 60 ℃, 34.9g of tung oil is rapidly added, reflux reaction is carried out for 1.5H, then 4mol/L of H 2SO4 is used for regulating the pH value of a reaction system to 1, after heat preservation is continued for 1H, 0.15MPa reduced pressure distillation is used for recovering solvent methanol, 17.45g of petroleum ether is added, static separation is carried out, then hot water is utilized for carrying out acid removal washing for multiple times, static separation is carried out, 0.08MPa reduced pressure distillation is used for removing petroleum ether and a small amount of water, and tung oil acid is obtained, the acid value is 192.4mgKOH/g, and the iodine value is 146.5g/100g.
The dimer acid content in the product was 86.5% and the single ring structure was 81.2% as determined.
Example 4
The difference from example 1 is that: the method comprises the steps of adding alkyl quaternary ammonium salt and lithium-containing compound into tung oil acid raw material, wherein the mass ratio of the alkyl quaternary ammonium salt to the lithium-containing compound is 2:1, the alkyl quaternary ammonium salt is tetradecyl ammonium chloride, and the lithium-containing compound is lithium carbonate.
The dimer acid content in the product was determined to be 87.2% and the single ring structure was determined to be 89.8%.
Example 5
The difference from example 2 is that: the method comprises the steps of adding alkyl quaternary ammonium salt and lithium-containing compound into tung oil acid raw material, wherein the mass ratio of the alkyl quaternary ammonium salt to the lithium-containing compound is 1:1, and the alkyl quaternary ammonium salt is octadecyl trimethyl ammonium chloride and contains lithium chloride.
The dimer acid content in the product was 88.5% and the ratio of the single ring structure was 92.5% as determined.
Example 6
The difference from example 3 is that: the method comprises the steps of adding alkyl quaternary ammonium salt and lithium-containing compound into tung oil acid raw material, wherein the mass ratio of the alkyl quaternary ammonium salt to the lithium-containing compound is 3:1, the alkyl quaternary ammonium salt is cetyl trimethyl ammonium chloride, and the lithium-containing compound is lithium hydroxide.
The dimer acid content in the product was determined to be 87.3% and the single ring structure was determined to be 86.4%.
Comparative example 1
The preparation process and operating conditions were the same as in example 1 except that the reactor was a conventional stirred tank reactor. The dimer acid content in the product was found to be 40.3% and the trimer acid content was found to be 49.4%.