阅读说明：本技术 二聚酸及其连续生产方法、连续生产系统和应用 (Dimer acid, continuous production method thereof, continuous production system and application ) 是由 伏朝林 赵杰 陶志平 朱忠朋 李涛 于 2019-09-23 设计创作，主要内容包括：本发明提供一种二聚酸的连续生产方法及连续生产系统,该连续生产方法包括使包含C-(18)脂肪酸和溶剂的混合体系于含有催化剂的固定床反应器中进行连续的聚合反应,以制得二聚酸,其中：催化剂包含载体及负载于载体的活性组分,活性组分包含铝,载体为MCM-41分子筛或MCM-48分子筛,其中以摩尔比计,催化剂的硅铝比为(5～80):1。通过采用特定催化剂和方法制备二聚酸,使所得二聚酸纯度、产率和选择性均得到了明显提升,同时所得二聚酸单环占比高,用于抗磨剂时,有利于提高其抗磨性能。本发明的方法还能够保证聚合反应的连续进行,适用于二聚酸的大规模生产。(The invention provides a continuous production method and a continuous production system of dimer acid, wherein the continuous production method comprises the step of enabling the dimer acid to contain C 18 Carrying out continuous polymerization reaction on a mixed system of fatty acid and solvent in a fixed bed reactor containing a catalyst to prepare dimer acid, wherein: the catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component contains aluminum, the carrier is an MCM-41 molecular sieve or an MCM-48 molecular sieve, and the silicon and the aluminum of the catalyst are calculated according to the molar ratioThe ratio is (5-80): 1. The dimer acid is prepared by adopting a specific catalyst and a method, so that the purity, yield and selectivity of the obtained dimer acid are obviously improved, and meanwhile, the obtained dimer acid has high monocyclic occupation ratio and is beneficial to improving the wear resistance when being used as an antiwear agent. The method of the invention can also ensure the continuous operation of the polymerization reaction and is suitable for the large-scale production of the dimer acid.)

1. A method for continuously producing dimer acid, comprising: make it contain C₁₈Carrying out continuous polymerization reaction on a mixed system of fatty acid and solvent in a fixed bed reactor containing a catalyst to prepare the dimer acid, wherein:

the catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component contains aluminum, the carrier is an MCM-41 molecular sieve or an MCM-48 molecular sieve, and the silica-alumina ratio of the catalyst is (5-80): 1 in terms of molar ratio.

2. The continuous production method according to claim 1, wherein the silicon-aluminum ratio of the catalyst is (20-40): 1.

3. The continuous production process according to claim 1, wherein the active component further comprises M, wherein M is one or more selected from the group consisting of lithium, boron, calcium and phosphorus, and the active component M is present in an amount of not more than 1.2 wt% of the catalyst.

4. The continuous production process according to claim 3, wherein the active component M is present in an amount of 0.6 to 0.9 wt% based on the catalyst content.

5. The continuous production method according to claim 1, wherein the polymerization reaction is carried out under a carbon dioxide atmosphere.

6. The continuous production method according to claim 1, wherein the polymerization reaction has a reaction pressure of 2MPa to 8MPa, a reaction temperature of 200 ℃ to 270 ℃ and a volume space velocity of 1h^-1～5h^-1。

7. The continuous production method according to claim 1, wherein C is₁₈The fatty acid is tall oil fatty acid, oleic acid or linoleic acid.

8. The continuous production method according to claim 1, wherein C is₁₈The fatty acid accounts for 20-80 wt% of the mixed system.

9. The continuous production method according to claim 1, wherein the solvent is one or more selected from petroleum ether and aromatic hydrocarbon.

10. The continuous production method according to claim 1, further comprising: and (3) after the material out of the fixed bed reactor is subjected to water cooling treatment, recovering the solvent through reduced pressure distillation for recycling.

11. A continuous production system of dimer acid for use in the continuous production method according to any one of claims 1 to 10, comprising:

a raw material premixing device provided with C₁₈Fatty acid feed and solvent feed for the C₁₈Mixing a fatty acid and the solvent;

the discharge end of the raw material premixing device is connected to the feed end of the fixed bed reactor, and the fixed bed reactor is provided with a fixed bed layer containing the catalyst.

12. The continuous production system of claim 11, further comprising a carbon dioxide gas supply device, wherein the gas outlet end of the carbon dioxide gas supply device is connected to the gas inlet end of the fixed bed reactor.

13. The continuous production system of claim 11, further comprising a water cooling device, a feed end of the water cooling device being connected to a discharge end of the fixed bed reactor.

14. The continuous production system according to claim 13, further comprising a recycling device, wherein a feeding end of the recycling device is connected to a discharging end of the water cooling device, and a discharging end of the recycling device is connected to the solvent feeding end through a circulating pipeline, so that the solvent passing through the recycling device enters the raw material premixing device for recycling.

15. Continuous production system according to claim 11, characterised in that the solvent feed end, C₁₈The fatty acid feeding end and the feeding end of the fixed bed reactor are respectively provided with a delivery pump and a valve so as to respectively control the C₁₈The delivery of fatty acid, the solvent and the mixed system.

16. A dimer acid obtained by the continuous production method according to any one of claims 1 to 10.

17. The dimer acid according to claim 16, wherein the dimer acid comprises one or more of acyclic dimer acid, monocyclic dimer acid, and bicyclic dimer acid, and wherein the content of monocyclic dimer acid is 60 wt% or more of the dimer acid.

18. The dimer acid according to claim 17, wherein said acyclic dimer acid constitutes 5 to 40 wt% of said dimer acid, and wherein said bicyclic dimer acid constitutes 5 to 40 wt% of said dimer acid.

19. Use of a dimer acid according to any one of claims 16 to 18 in an antiwear agent.

Technical Field

The invention relates to a chemical synthesis technology, in particular to dimer acid, a continuous production method, a continuous production system and application thereof.

Background

Dimer acid, commonly referred to as dimer fatty acid, is a complex mixture of ingredients, so called because the major constituent contains two carboxylic acid groups. At present, dimer acid is widely applied to the fields of synthetic printed circuit board materials, ink manufacturing, rocket motor materials and the like. In addition, the dimer acid also has stronger polarity, is easy to adsorb on the surface of metal to form an oil film, and effectively reduces the friction and the abrasion of metal parts, so the dimer acid has excellent lubricity and abrasion resistance, can be used as an anti-wear agent of fuel, and is particularly used in the field of aviation fuel.

At present, jet fuel antiwear agents abroad are mainly dimer acid type, and naphthenic acid type antiwear agents are mainly used at home. The naphthenic acid is mainly derived from diesel oil and aviation kerosene, but the sources of the natural naphthenic acid are increasingly limited as refineries begin to adopt hydrogenation processes to refine the diesel oil and the aviation kerosene. Therefore, there is an increasing demand for dimer acid-based antiwear agents from an international standpoint as well as from a raw material source.

Dimer acids typically comprise acyclic, monocyclic and bicyclic C in composition₃₆Unsaturated fatty acids. Abrasion resistance of dimer acidThe composition of which has an important relationship. The classical antiwear agent action mechanism considers that the more the number of molecular rings is, the poorer the flexibility of the molecules is, but the more the number of rings is, the more stable the adsorption energy of the molecules on the metal surface can be properly improved; further, the higher the degree of unsaturation in the molecule, the greater the coefficient of friction. Therefore, in summary, the content of the bicyclo-fatty acid in the dimer acid is reduced, the proportion of the monocyclic fatty acid is improved, the olefin content of the dimer acid is reduced as much as possible, the flexibility of the dimer acid is improved, the friction coefficient of the dimer acid is reduced, and the abrasion resistance of the dimer acid is improved.

Much research has been done on the synthesis of dimer acid, but most have used clay as a polymerization catalyst. The preparation process of the argil as the catalyst is mature, but the argil has the defects of adsorbing a certain amount of dimer acid products, being difficult to regenerate, large solid waste generation amount and the like. The synthesis of dimer acids using other catalysts has also been reported, such as Lewis acids, ionic liquids, zirconium dioxide (ZrO)₂) Etc. as a catalyst. Lewis acids, e.g. AlCl₃It is toxic and not easy to separate from the product, and the subsequent treatment is troublesome; the ionic liquid has high activity, but is difficult to separate due to high price, so that the ionic liquid is difficult to realize large-scale production and use; patent CN 104785297A discloses two ionic liquids for synthesizing dimer acid antiwear agent, but the ionic liquid preparation process is complex and the preparation cost is high; ZrO (ZrO)₂It is also a catalyst which has been studied more, but the yield of the product is low when it catalyzes the synthesis of dimer acid, for example, the article "influence of three catalysts on dimerization of safflower oil fatty acid under autogenous pressure" describes ZrO₂When the dimer acid is used as a catalyst, the yield of the dimer acid is only 67.49 percent, and needs to be further improved. In the existing method, the polymerization process of the dimer acid is also easy to generate decarboxylation side reaction, which causes the problems of reduced yield of the dimer acid and increased by-products.

In addition, the dimer acid has the characteristics of high viscosity and poor fluidity, and is easy to cause the problems of unsmooth feeding, pipeline blockage, catalyst surface activity coverage and the like in the production process, so that the conventional dimer acid synthesis method is mostly a batch method and is difficult to realize large-scale industrial production.

It is noted that the information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The present invention has a primary object to overcome at least one of the above-mentioned drawbacks of the prior art, and to provide a method and a system for continuously producing dimer acid, and dimer acid produced by the continuous production method and use thereof. The dimer acid is prepared by adopting a specific catalyst and a method, so that the purity, yield and selectivity of the obtained dimer acid are obviously improved, and meanwhile, the obtained dimer acid has high monocyclic occupation ratio and is beneficial to improving the wear resistance when being used as an antiwear agent. The invention can also ensure the continuous polymerization reaction and is suitable for the large-scale production of the dimer acid.

In order to achieve the purpose, the invention adopts the following technical scheme:

one aspect of the present invention provides a method for continuously producing dimer acid, comprising: make it contain C₁₈Carrying out continuous polymerization reaction on a mixed system of fatty acid and solvent in a fixed bed reactor containing a catalyst to prepare dimer acid, wherein: the catalyst comprises a carrier and an active component loaded on the carrier, wherein the active component contains aluminum, the carrier is an MCM-41 molecular sieve or an MCM-48 molecular sieve, and the silica-alumina ratio of the catalyst is (5-80): 1 in terms of molar ratio.

According to one embodiment of the invention, the silicon-aluminum ratio of the catalyst is (20-40): 1.

According to one embodiment of the invention, the active component further comprises M, wherein M is selected from one or more of lithium, boron, calcium and phosphorus, and the active component M accounts for not more than 1.2 wt% of the catalyst.

According to one embodiment of the invention, the active component M represents between 0.6% and 0.9% by weight of the catalyst content.

According to one embodiment of the invention, the polymerization reaction is carried out under an atmosphere of carbon dioxide.

According to an embodiment of the inventionThe application mode is that the reaction pressure of the polymerization reaction is 2MPa to 8MPa, the reaction temperature is 200 ℃ to 270 ℃, and the volume space velocity is 1h^-1～5h^-1。

According to one embodiment of the invention, C₁₈The fatty acid is tall oil fatty acid, oleic acid or linoleic acid.

According to one embodiment of the invention, C₁₈The fatty acid accounts for 20-80 wt% of the mixed system.

According to one embodiment of the present invention, the solvent is one or more selected from petroleum ether and aromatic hydrocarbons.

According to an embodiment of the present invention, the continuous production method further comprises: and (3) after the material out of the fixed bed reactor is subjected to water cooling treatment, recovering the solvent through reduced pressure distillation for recycling.

Still another aspect of the present invention provides a continuous production system for dimer acid used in the above continuous production method, comprising: a raw material premixing device and a fixed bed reactor, wherein the raw material premixing device is provided with a component C₁₈Fatty acid feed and solvent feed for C₁₈Mixing fatty acid and solvent; the discharge end of the raw material premixing device is connected to the feed end of the fixed bed reactor, and the fixed bed reactor is provided with a fixed bed layer containing a catalyst.

According to one embodiment of the invention, the device further comprises a carbon dioxide gas supply device, and the gas outlet end of the carbon dioxide gas supply device is connected to the gas inlet end of the fixed bed reactor.

According to one embodiment of the invention, the device further comprises a water cooling device, and the feeding end of the water cooling device is connected to the discharging end of the fixed bed reactor.

According to an embodiment of the invention, the system further comprises a recovery processing device, wherein a feed end of the recovery processing device is connected to a discharge end of the water cooling device, and a discharge end of the recovery processing device is connected to a solvent feed end through a circulating pipeline, so that the solvent passing through the recovery processing device enters the raw material premixing device for recycling.

According to one embodiment of the invention, the solvent feed end, C₁₈Fatty acid feed end and fixed bed reactionThe feed end of the device is respectively provided with a delivery pump and a valve to respectively control the valve C₁₈The delivery of fatty acid, solvent and mixed system.

In another aspect, the present invention provides a dimer acid obtained by the above continuous production method.

According to one embodiment of the present invention, the dimer acid contains one or more of acyclic dimer acid, monocyclic dimer acid, and bicyclic dimer acid, and the content of monocyclic dimer acid is 60 wt% or more of the content of dimer acid.

According to one embodiment of the present invention, the acyclic dimer acid constitutes 5 to 40 wt% of the dimer acid content, and the bicyclic dimer acid constitutes 5 to 40 wt% of the dimer acid content.

Another aspect of the invention provides the use of the dimer acid described above in an antiwear agent.

According to the technical scheme, the continuous production method and the continuous production system for the dimer acid have the advantages and positive effects that:

the invention provides a method for continuously producing dimer acid and a continuous production system suitable for the continuous production method, aiming at the problems of discontinuous preparation process of the existing dimer acid, high solid waste pollution, difficult regeneration of a catalyst, high cost, low yield of the dimer acid and the like. By adopting the specific molecular sieve catalyst, the purity, yield and selectivity of the dimer acid are obviously improved, and meanwhile, the obtained dimer acid has high monocyclic occupation ratio, and is beneficial to improving the wear resistance when being used as an antiwear agent. In addition, the method prevents the possible blockage of a reaction system by adopting a solvent dilution method, so that the process for preparing the dimer acid can be continuously and stably carried out, and the method is suitable for large-scale production of the dimer acid.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

FIG. 1 representatively illustrates a continuous production system in accordance with one embodiment of the present invention;

FIG. 2 is an IR spectrum of dimer acid of example 1 of this invention.

Wherein the reference numbers are as follows:

100: raw material premixing device

100a：C₁₈Fatty acid feed end

100 b: solvent feed end

100 c: discharge end of raw material premixing device

200: fixed bed reactor

201: fixed bed layer

200 a: feed end of fixed bed reactor

200 b: discharge end of fixed bed reactor

200 c: gas inlet end of fixed bed reactor

300: carbon dioxide gas supply device

300 b: air outlet end of carbon dioxide air supply device

400: water cooling device

400 a: feed end of water cooling device

400 b: discharge end of water cooling device

400 c: air outlet end of water cooling device

500: recovery processing device

500 a: feed end of recovery processing device

500 b: discharge end of recovery processing device

500 c: discharge end of dimer acid product

Detailed Description

The following presents various embodiments or examples in order to enable those skilled in the art to practice the invention with reference to the description herein. These are, of course, merely examples and are not intended to limit the invention. The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to yield one or more new ranges of values, which ranges of values should be considered as specifically disclosed herein.

Referring to fig. 1, a continuous production system according to an embodiment of the present invention is representatively illustrated. As shown in FIG. 1, the continuous production system of the present invention is described by taking as an example the continuous production method of dimer acid to be applied to the present invention. In this embodiment, the continuous production system for dimer acid provided by the present invention mainly comprises a raw material premixing device and a fixed bed reactor. The structure and functional relationship of the main components of an exemplary embodiment of the continuous dimer acid production system according to the present invention will be described in detail with reference to fig. 1. Unless otherwise specified, the ports of the following main components are connected by means of pipes.

As shown in fig. 1, in the present embodiment, the present invention provides a continuous production system of dimer acid, comprising: a raw material premixing device 100 and a fixed bed reactor 200, wherein the raw material premixing device 100 is used for mixing C₁₈Fatty acid and solvent are mixed, and the raw material premixing devices 100 are respectively provided with C₁₈Fatty acid feed 100a and solvent feed 100b to separate C₁₈The fatty acid and solvent enter the feedstock premixing device 100.

The discharge end 100c of the raw material premixing device 100 is connected to the feed end 200a of the fixed bed reactor 200, and the fixed bed reactor 200 is provided with a fixed bed layer 201 containing a catalyst. The fixed bed 201 may be disposed at an intermediate position of the fixed bed reactor 200, but the present invention is not limited thereto.

According to the invention, in the continuous production of dimer acid, C₁₈Fatty acids and solvents are passed through C₁₈The fatty acid feeding end 100a and the solvent feeding end 100b enter the raw material premixing device 100 to be uniformly mixed to obtain a mixed system, the mixed system enters the fixed bed reactor 200 through the feeding end 200a of the fixed bed reactor and contacts with the catalyst on the fixed bed layer 201 to carry out polymerization reaction, and the reacted product can be discharged through the discharging end 200b of the fixed bed reactor. Wherein the catalyst comprises a carrier and an active component loaded on the carrier, the active component comprises aluminum, the carrier is an MCM-41 molecular sieve or an MCM-48 molecular sieve, and the catalyst comprises the following components in molar ratioThe silicon-aluminum ratio is (5-80): 1.

According to the invention, the dimer acid has the characteristics of high viscosity and poor fluidity, and is easy to cause the problems of unsmooth feeding, pipeline blockage, catalyst surface activity coverage and the like in the production process, so that the conventional dimer acid synthesis method is mostly a batch method and is difficult to realize large-scale industrial production. The method prevents the possible blockage of a reaction system by adopting a solvent dilution method, so that the process of preparing the dimer acid can be continuously and stably carried out, and the method is suitable for large-scale industrial production.

In addition, the inventor of the invention finds that the dimer acid can be effectively synthesized by adopting the molecular sieve catalyst loaded with specific components and active components with specific content, and the purity, yield and selectivity of the obtained dimer acid are obviously improved. Wherein, the aluminum can make the catalyst have certain acidity and catalyze the olefin to carry out polymerization reaction. The molecular sieve is an MCM-41 molecular sieve or an MCM-48 molecular sieve, and is preferably the MCM-41 molecular sieve. The molecular sieve has the aperture range of 4-8 nm, and has rich mesoporous structure and large specific surface area (800 m)²/g-1000m²The mesoporous material of/g) enables aluminum to have acidic active sites after being added, can better perform catalytic polymerization, and is particularly beneficial to enabling the monocyclic ratio of the synthesized dimer acid to be higher when the mesoporous material is used for synthesizing the dimer acid, thereby being beneficial to improving the abrasion resistance of the dimer acid. The acid amount of the catalyst can be influenced by adjusting the silicon-aluminum ratio in the molecular sieve, and the catalytic activity of the catalyst is further influenced. The inventor finds that the silicon-aluminum ratio of the catalyst of the invention is too large or too small, which affects the selectivity and yield of the dimer acid, and the silicon-aluminum ratio is preferably (5-80): 1, preferably (20-40): 1.

In some embodiments, the active component of the catalyst of the present invention further comprises M, wherein M is selected from one or more of lithium (Li), boron (B), calcium (Ca) and phosphorus (P), and the active component M accounts for not more than 1.2 wt% of the catalyst, preferably 0.6 wt% to 0.9 wt%. The introduction of the active component M can play a synergistic role with Al, and the acidity and the acid content of the catalyst can be changed by adjusting the content of the specific active component M, so that the catalyst is suitable for catalyzing the synthesis of dimer acid; in addition, the active component M also has a certain auxiliary agent effect and can induce or promote diene synthesis reaction, and further, the catalyst also has the advantages of easy recovery and recycling.

The preparation method of the catalyst comprises the following steps: adding a template agent and a silicon source into water, and uniformly stirring to obtain an initial gel mixture; adding an aluminum source, namely an aqueous solution containing an active component aluminum, such as aluminum sulfate, into the initial gel mixture, stirring and adjusting the pH value of the solution to 10-11 to obtain a gel precursor; heating the gel precursor for crystallization; after crystallization treatment, separating a crystallized solid product from a mother solution; and washing, drying and calcining the crystallized solid product to obtain the catalyst.

The invention also comprises adding a compound of active ingredient M to the initial gel mixture, wherein the compound of active ingredient M is selected from one or more of the chloride, hydroxide and carbonate compounds of M, M is selected from one or more of lithium, boron, calcium and phosphorus.

The hydrothermal synthesis method is adopted to dope M into the catalyst, so that the loading effect of the active component M is more stable, the dispersion is better, and compared with an impregnation method or an ion exchange method, the catalyst prepared by the method is more suitable for repeated cyclic utilization.

The aforementioned templating agents include, but are not limited to, one or more of cetyltrimethylammonium bromide (CTAB), tetrapropylammonium bromide, and tetraethylammonium bromide, and the silicon source includes, but is not limited to, one or more of Tetraethylorthosilicate (TEOS), solid amorphous silica, and sodium silicate. Preferably, the templating agent is cetyltrimethylammonium bromide and the silicon source is tetraethyl orthosilicate (TEOS).

In some embodiments, the active ingredient M is lithium and the compound containing the active ingredient M is selected from the group consisting of lithium chloride (LiCl), lithium carbonate (Li)₂CO₃) And lithium hydroxide (LiOH). Preferably, lithium chloride (LiCl).

According to the invention, the crystallization temperature and crystallization time have a certain influence on the catalyst synthesized. The crystallization temperature should not be too high or too low, and the time should not be too short or too long, which would result in a certain degree of catalyst performance degradation. In some embodiments, the temperature of the crystallization treatment is 120 ℃ to 160 ℃, preferably 130 ℃ to 150 ℃, and the time of the crystallization treatment is 18h to 30h, preferably 20h to 24 h.

In some embodiments, the aforementioned calcining comprises: calcining at 450-650 ℃ for 8-14 h at the heating rate of 2-5 ℃/min. Preferably, the heating rate is 3 ℃/min to 4 ℃/min, the calcining temperature is 500 ℃ to 600 ℃, and the calcining time is 10h to 12 h.

In the catalytic reaction for the preparation of dimer acid according to the present invention, the aforementioned C₁₈The fatty acid may be tall oil fatty acid, oleic acid or linoleic acid, preferably tall oil fatty acid. The oleic acid or linoleic acid can be derived from the transformation of vegetable oil and fat, including soybean oil, corn oil, sunflower seed oil, peanut oil, cottonseed oil, rapeseed oil, sesame oil, palm oil, coconut oil, castor oil and the like, and can also be synthetic oleic acid or linoleic acid, which is not limited in the invention.

In some embodiments, C₁₈Fatty acids in the above-mentioned mixed system, i.e. in C₁₈The total mass percentage of the fatty acid and the solvent is 20wt percent to 80wt percent, and preferably 30wt percent to 60wt percent. Too small an amount of solvent will not achieve the effect of dilution, and too large an amount of solvent will affect the concentration of the raw material and thus the yield of dimer acid.

In some embodiments, the solvent is petroleum ether or an aromatic hydrocarbon, such as benzene, and the like. Preferably, it is petroleum ether. Compared with aromatic solvents such as benzene and the like, the petroleum ether is relatively nontoxic and is more suitable for industrial production, and in addition, the petroleum ether has good compatibility with the dimer acid and is easy to remove, and the petroleum ether serving as the solvent does not influence the synthesis reaction of the dimer acid.

As shown in fig. 1, in some embodiments, the continuous production system of the present invention further comprises a carbon dioxide gas supply device 300, wherein the gas outlet end 300b of the carbon dioxide gas supply device 300 is connected to the gas inlet end 200c of the fixed bed reactor. The catalytic reaction is preferably carried out in carbon dioxide (CO)₂) The reaction is carried out under an atmosphere. The side reaction of decarboxylation is easy to occur in the polymerization process of the dimer acid, which causes the problems of the yield reduction and the increase of the by-products of the dimer acid. By reaction of carbon dioxideThe decarboxylation side reaction can be effectively inhibited under the atmosphere, so that the yield of the dimer acid is improved, and the generation of byproducts is reduced. Specifically, before the reaction, CO is used by the carbon dioxide gas supply means 300₂Replacing air in the fixed bed reactor with gas, and introducing CO₂The gas maintains the reaction system at a certain reaction pressure.

In some embodiments, the reaction pressure is from 2MPa to 8MPa, preferably from 4MPa to 6 MPa. The volume space velocity of the reaction is 1h^-1～5h^-1Preferably 1h^-1～3h^-1. The yield and selectivity of dimer acid are affected to different degrees by too high or too low a reaction pressure and volume space velocity.

In some embodiments, the catalytic reaction temperature is 200 ℃ to 270 ℃, preferably 240 ℃ to 260 ℃. The yield and selectivity of dimer acid can be influenced by over-high catalytic reaction temperature, and the yield can be influenced by reducing the conversion rate of fatty acid to a certain extent by over-low temperature.

As shown in fig. 1, in some embodiments, the continuous production system of the present invention further includes a water cooling device 400, wherein a feed end 400a of the water cooling device is connected to a discharge end 200b of the fixed bed reactor, and the material reacted by the fixed bed reactor 200 enters the water cooling device 400 for water cooling. The water cooling device generally further comprises an air outlet 400c for discharging CO separated from the high-temperature material during cooling₂And (4) exhaust gas.

Further, in some embodiments, the water cooling device 400 is further connected with a recycling device 500, wherein the feeding end 500a of the recycling device 500 is connected to the discharging end 400b of the water cooling device, and the discharging end 500b of the recycling device is connected to the feeding end 100b of the solvent through a recycling pipeline, so that the solvent passing through the recycling device enters the raw material premixing device 100 for recycling. The recovery processing mode is generally that the material after water cooling processing is decompressed and distilled, the solvent is recycled after being recovered, and the dimer acid product is obtained after distillation and is discharged from the discharge end 500c of the dimer acid product.

According to the present invention, valves are disposed on the pipelines connected between the above-mentioned apparatuses, and sampling ports (not shown) may be disposed near the feeding end 200a of the fixed bed reactor 200 and near the discharging end 400b of the water cooling apparatus to monitor the technical indexes of the transported materials.

In some embodiments, solvent feed ends 100b, C₁₈The fatty acid feed end 100a and the feed end 200b of the fixed bed reactor are provided with a transfer pump and a valve, respectively, to control C₁₈The delivery of fatty acid, solvent and mixed system. Preferably, the control mode can realize the automatic control of the material conveying through a central control room by combining with an automatic control mode commonly used in the field.

The continuous production system and the continuous production method realize the continuous production of the dimer acid. By adopting the specific molecular sieve catalyst, the purity, yield and selectivity of the dimer acid are obviously improved, and meanwhile, the obtained dimer acid has high monocyclic occupation ratio, and is beneficial to improving the wear resistance when being used as an antiwear agent. In addition, aiming at the characteristics of high viscosity and poor fluidity of the dimer acid, the invention also adopts a method of specific solvent dilution to ensure the continuous operation of the polymerization reaction, and is suitable for the large-scale production of the dimer acid.

In another aspect, the present invention provides a dimer acid obtained by the above continuous production method.

In some embodiments, the dimer acid prepared by the above catalyst and the above method comprises one or more of acyclic dimer acid (e.g., formula I below), monocyclic dimer acid (e.g., formula II below), and bicyclic dimer acid (e.g., formula III below), and the monocyclic dimer acid comprises more than 60 wt% of the dimer acid content. In some embodiments, the acyclic dimer acid comprises 5 wt% to 40 wt% of the dimer acid content, and the bicyclic dimer acid comprises 5 wt% to 40 wt% of the dimer acid content.

The anti-wear properties of dimer acid are of significant concern with its composition. The classical antiwear agent action mechanism considers that the more the number of molecular rings is, the poorer the flexibility of the molecules is, but the more the number of rings is, the more stable the adsorption energy of the molecules on the metal surface can be properly improved; therefore, the content of the bicyclo-fatty acid in the dimer acid is reduced, the proportion of the monocyclic fatty acid is improved, the flexibility of the dimer acid is improved, the friction coefficient of the dimer acid is reduced, and the abrasion resistance of the dimer acid is improved. The dimer acid prepared by the method can effectively ensure that the monocyclic dimer acid accounts for more than 60 wt% of the content of the dimer acid. Therefore, when the dimer acid disclosed by the invention is used as an antiwear agent, the antiwear effect can be well improved, and the dimer acid has a good industrial application prospect.

The invention will be further illustrated by the following examples, but is not to be construed as being limited thereto. Unless otherwise specified, all reagents used in the invention are analytically pure.

Preparation example 1

This preparation example 1 is intended to illustrate the preparation of the catalyst of the present invention

(1) Dissolving 10g of cetyltrimethylammonium bromide (CTAB) template agent in 50mL of deionized water, and fully stirring for 10min at 50 ℃ until the solution becomes a transparent gel solid state;

(2) then, 44mL of tetraethyl orthosilicate (TEOS) was added thereto and mixed, and stirred at normal temperature for 30min to obtain an initial gel mixture;

(3) according to the requirement of Si/Al-40, Al with the concentration of 0.243mol/L is added₂(SO₄)₃10mL of aqueous solution; then according to the requirement of Li doping amount of 0.6 wt%, adding 15mL of 1.0mol/L LiCl solution as a lithium source, and stirring for about 30min to obtain a white colloidal solution;

(4) adjusting pH to 10-11 with strong ammonia water, and stirring for 60 min;

(5) transferring the mixture into a stainless steel reactor with a polytetrafluoroethylene lining, sealing, and crystallizing for 24 hours in an oven at the crystallization temperature of 140 ℃;

(6) after crystallization is finished, filtering and separating the crystallized solid product from mother liquor, and repeatedly washing the crystallized solid product to be neutral by using deionized water;

(7) drying at 80 deg.C for 12h to obtain dried solid product;

(8) and finally, calcining the mixture in a muffle furnace at 550 ℃ for 10 hours at the heating rate of 2 ℃/min to obtain the Li-Al-MCM-41 molecular sieve.

Preparation examples 2 to 5

The catalyst was prepared according to the method of preparation example 1, except that the content of the doping active component Li in the step (3) was changed, as shown in table 1 below:

TABLE 1

Comparative preparation example 1

The catalyst is prepared by adopting an impregnation method, and the method specifically comprises the following steps:

an Al-MCM-41 molecular sieve was synthesized according to the procedure of preparation example 1, except that no LiCl solution was added in step (3). Then according to the Li doping amount of 0.9 wt%, 0.3mol/L LiCl aqueous solution is used as a lithium source to be mixed with the Al-MCM-41 molecular sieve synthesized above, the mixture is placed for 10 hours at normal temperature with intermittent stirring, and finally the catalyst is dried for 12 hours at 80 ℃, so that the impregnation loading is completed, and the catalyst is obtained.

Comparative preparation example 2

A catalyst was prepared according to the method of comparative preparation example 1, except that an aqueous LiCl solution was used as a lithium source in an amount of 0.6 wt% Li doping.

Comparative preparation example 3

A catalyst was prepared according to the method of comparative preparation example 1, except that Li was used in an amount of Li doping of 0.6 wt%₂CO₃The aqueous solution acts as a lithium source.

Comparative preparation example 4

A catalyst was prepared according to the method of comparative preparation example 1, except that an aqueous LiOH solution was used as a lithium source in an amount of 0.6 wt% of Li doping.

Example 1

This example 1 is intended to illustrate the continuous production of dimer acid according to the present invention using the catalyst of preparation example 1.

In the raw material premixing device, petroleum ether is used as a solvent, and a 50 wt% soybean oleic acid solution is added and fully mixed. The catalyst of preparation example 1 was charged in a fixed bed, and then CO was introduced into the fixed bed reactor₂The air in the reaction mixture is replaced, and the fixed bed is heated to the reaction temperature of 240 ℃ at the heating rate of 5 ℃/min. Then pumping the raw material to a fixed bed reactor, wherein the volume space velocity is 2h^-1Adjusting back pressure valve and CO₂And an air inlet valve for keeping the reaction pressure at 5 MPa. After the system is stabilized for 10 hours, the system is treated by a water cooling device, and then the reaction discharge is taken for liquid chromatography analysis, wherein the conversion rate of fatty acid is 88.2 mol%, the selectivity of dimer acid is 85.1 mol%, and the yield of dimer acid is 75.1 mol%.

The structure distribution of the dimer acid obtained was measured, and the infrared measurement results are shown in FIG. 2. Wherein the proportion of the monocyclic dimer acid is 65%, the proportion of the acyclic dimer acid is 30%, and the proportion of the bicyclic dimer acid is 5%.

Examples 2 to 5

The dimer acid was prepared according to the method of example 1, except that the catalysts of preparation examples 2-5 were used to prepare dimer acid, and the results of fatty acid conversion, dimer acid selectivity and dimer acid yield after the reaction are shown in table 2 below.

TABLE 2

It is clear from comparative examples 1 to 5 that the effect on the yield of dimer acid is relatively large when the catalyst contains different Li contents. With the increase of the Li content, the selectivity and the yield of the dimer acid and the conversion rate of the fatty acid are obviously improved. The effect is relatively best when the Li content is 0.9 wt%. However, if the Li content is too high, the selectivity and yield will be reduced to some extent. This is because more Li decreases the crystallinity of the molecular sieve and affects the acidity and acid content of the catalyst.

It can be seen from comparative examples 1 and 6 to 7 that the selectivity and yield of the product are also affected to some extent when the catalyst is synthesized by using different lithium sources. Preferably, LiCl is selected as the lithium source.

Comparative examples 1 to 4

Dimer acid was prepared according to the method of example 1, except that the catalysts of comparative preparation examples 1-4 were used to prepare dimer acid, and the results of fatty acid conversion, dimer acid selectivity and dimer acid yield after the reaction are shown in table 3 below.

TABLE 3

As can be seen from table 3 above, comparing comparative example 2 with example 1, the catalyst prepared by hydrothermal synthesis method has better Li supported on the molecular sieve than the impregnation method, so the catalyst has higher catalytic activity than the catalyst synthesized by impregnation method, and the selectivity and yield of the obtained product are also higher.

Comparing comparative example 1 and comparative example 2, it can be seen that the catalyst having a Li content of 0.9 wt% still has a better catalytic effect than the catalyst having a doping amount of 0.6 wt% under the impregnation method.

Comparing examples 1, 6 and 7 with comparative examples 2 to 4, respectively, it can be seen that the catalyst synthesized by hydrothermal synthesis method has higher catalytic activity than that synthesized by immersion method under different lithium source conditions.

Examples 8 to 11

Dimer acid was continuously produced as in example 1, except that the catalytic reaction was carried out using catalysts of different silica to alumina ratios, and the results were as shown in Table 4 below:

TABLE 4

As can be seen from table 4 above, different silica-alumina ratios have a great influence on the structural distribution of dimer acid. Preferably, the silicon-aluminum ratio is (20-40): when 1, the selectivity and the yield of the dimer acid are both high.

Examples 12 to 15

Dimer acid was continuously produced in the same manner as in example 1, except that the temperature of the catalytic reaction was changed, and the results were as shown in the following Table 5:

TABLE 5

As can be seen from Table 5 above, the catalytic reaction temperature has an influence on the reaction results. The catalytic reaction temperature is preferably from 240 ℃ to 260 ℃. The yield and selectivity of dimer acid can be influenced by overhigh catalytic reaction temperature, the conversion rate of fatty acid can be reduced to a certain degree by overlow temperature, and the influence on the yield is also large.

Examples 16 to 19

Dimer acid was prepared as in example 1, except that the pressure at which the reaction was catalyzed was varied and the results are shown in Table 6 below:

TABLE 6

As can be seen from Table 5 above, the yield and selectivity of dimer acid are affected to different extents when the reaction pressure is too high or too low. When the reaction pressure is 6MPa, the selectivity and the yield of the dimer acid are both high.

Comparative example 5

Dimer acid was prepared as in example 1, except that carbon dioxide was not used, and 4MPa of nitrogen (N) was used₂) Is a reaction atmosphere. After the catalytic reaction, the conversion rate of the fatty acid was 86.4 mol%, the selectivity of the dimer acid was 70.4 mol%, and the yield of the dimer acid was 60.8 mol%. Compared with the example 13, the product selectivity and yield are obviously improved by adopting carbon dioxide as the reaction atmosphere compared with nitrogen. Therefore, the reaction atmosphere of carbon dioxide is adopted, the decarboxylation side reaction can be effectively inhibited, the yield of dimer acid is further improved,the generation of byproducts is reduced.

Examples 20 to 23

Dimer acid was prepared as in example 1, except that the space velocity of the reaction catalyzed was varied and the results are shown in table 7 below:

TABLE 7

As can be seen from Table 7 above, the reaction space velocity is preferably 1h, either too high or too low, which affects the yield and selectivity of dimer acid to various degrees^-1～3h^-1It is preferable.

Examples 24 to 27

Dimer acid was prepared according to the method of example 1, except that the concentration of the raw material, soybean oleic acid, in the catalytic reaction was changed, and the reaction results are shown in the following table 8:

TABLE 8

As can be seen from table 8 above, the concentration of the reactant, i.e., the soybean oleic acid, has a certain effect on the yield of dimer acid. When the concentration of the soybean oleic acid is too high, the selectivity and the yield of the dimer acid are obviously reduced. Preferably, the concentration of the reactants is 30 wt% to 60 wt%.

Examples 28 to 31

Dimer acid was prepared as in example 1, except that the reaction output was taken every 10h for gas chromatographic analysis and the results are shown in Table 9 below:

TABLE 9

As can be seen from Table 9 above, the catalyst of the present invention has good stability, and after the dimer acid is continuously produced by the method of the present invention for 50 hours, the catalyst still has good activity, and the selectivity and yield of the dimer acid are not obviously reduced. Therefore, the catalyst and the method are suitable for continuously producing the dimer acid and have good industrial prospect.

In summary, the method for continuously producing dimer acid provided by the invention adopts the specific molecular sieve catalyst, so that the purity, yield and selectivity of the obtained dimer acid are obviously improved, and meanwhile, the obtained dimer acid has high monocyclic occupation ratio, and is beneficial to improving the wear resistance when being used as an antiwear agent. In addition, the method of the invention also ensures the continuous operation of the polymerization reaction, and the catalyst still has good activity after the dimer acid is continuously produced for 50 hours under the condition of specific solvent dilution, and the dimer acid has high yield and good selectivity, thereby being suitable for the large-scale production of the dimer acid.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.