阅读说明：本技术 制备异辛酸的工艺方法 (Process for preparing isooctanoic acid ) 是由 杨忠梅 吕爱梅 孟宪谭 张敏 侯磊 李玉田 于 2018-09-05 设计创作，主要内容包括：本发明属于异辛酸的制备技术领域,具体的涉及一种制备异辛酸的工艺方法。将异辛醇和氢氧化钠两种物料投入固定床反应器,在惰性气氛条件下进行氧化,以TiO<Sub>2</Sub>-CeO<Sub>2</Sub>金属氧化物为催化剂,反应至无氢气生成；物料在固定床反应器出口减压并进入酸化池,采用硫酸对其进行酸化处理,搅拌20～40min,静置分层放去水层,水洗共三次,最后经过减压脱水精馏,得到异辛酸产品。该工艺方法催化剂易回收,反应条件温和,且生产成本低、收率高,反应时间短,缩短生产周期,可以连续工业化规模生产。(The invention belongs to the technical field of preparation of isooctanoic acid, and particularly relates to a process method for preparing isooctanoic acid. Putting two materials of isooctanol and sodium hydroxide into a fixed bed reactor, oxidizing under the condition of inert atmosphere, and using TiO 2 ‑CeO 2 The metal oxide is used as a catalyst and reacts until no hydrogen is generated; and (3) decompressing the material at the outlet of the fixed bed reactor, feeding the material into an acidification tank, carrying out acidification treatment on the material by using sulfuric acid, stirring for 20-40 min, standing for layering, draining off a water layer, washing for three times, and finally carrying out decompression, dehydration and rectification to obtain an isooctanoic acid product. The method has the advantages of easy recovery of catalyst, mild reaction conditions, low production cost, high yield, short reaction time, shortened production period, and continuous industrializationAnd (5) producing a mould.)

1. A process for preparing isooctanoic acid, which is characterized in that: the method specifically comprises the following steps: putting two materials of isooctanol and sodium hydroxide into a fixed bed for reactionOxidizing in an inert atmosphere to obtain TiO₂-CeO₂The metal oxide is used as a catalyst and reacts until no hydrogen is generated; and (3) decompressing the material at the outlet of the fixed bed reactor, feeding the material into an acidification tank, carrying out acidification treatment on the material by using sulfuric acid, stirring for 20-40 min, standing for layering, draining off a water layer, washing for three times, and finally carrying out decompression, dehydration and rectification to obtain an isooctanoic acid product.

2. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: TiO 2₂-CeO₂The mass of the metal oxide catalyst accounts for 5-8% of that of the isooctyl alcohol.

3. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: the mass fraction of isooctyl alcohol is 99%, and the mass fraction of sodium hydroxide is 30-40%.

4. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: the mass ratio of isooctyl alcohol to sodium hydroxide is 1: 1.1-1.3.

5. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: putting two materials, namely isooctanol and sodium hydroxide, into the fixed bed reactor, wherein the isooctanol and the sodium hydroxide are respectively put into the fixed bed reactor, and the input airspeed is 1h < -1 > to 2h < -1 >.

6. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: TiO 2₂-CeO₂The metal oxide is coated on the gamma-Al by adopting a dipping-sintering process₂O₃TiO formation on the surface of the molecular sieve₂-CeO₂A metal oxide catalyst; TiO 2₂-CeO₂The loading amount of the metal oxide is 4 percent of the total mass of the catalyst; wherein the TiO is₂Accounting for 85 percent of the specific surface area of the catalyst coating and a catalyst promoter CeO₂Accounting for 15 percent of the specific surface area of the catalyst coating.

7. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: the operating conditions of the fixed bed reactor were: under the condition of inert atmosphere, the temperature is 210-225 ℃, and the pressure is 2-4 MPa.

8. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: the material is decompressed at the outlet of the fixed bed reactor and enters an acidification pool, and the pressure is normal pressure.

9. The process for the preparation of isooctanoic acid as claimed in claim 1, wherein: the concentration of the sulfuric acid solution is 30-40%, and the pH value after acidification is 2.5-3.5.

Technical Field

The invention belongs to the technical field of preparation of isooctanoic acid, and particularly relates to a process method for preparing isooctanoic acid.

Background

Isooctanoic acid, academic name 2-ethylhexanoic acid, english name: 2-ethylhexoic acid, molecular weight: 144.21, it is colorless oily liquid, soluble in ether, slightly soluble in ethanol, and has mild odor. It is a fine chemical product and is widely applied in various industries and fields.

At present, the production methods of isooctanoic acid can be roughly divided into two types: one is to produce isooctanoic acid by using isooctaldehyde or isooctenal as raw material; the other is to produce the isooctanoic acid by using octanol as a raw material. The first method has the advantages of reasonable use of raw materials, mild reaction conditions and easy large-scale continuous production; however, the first method is suitable for large-scale chemical production with an intermediate product isooctaldehyde, and the isooctanoic acid produced by the method is far from meeting the market demand; since the aldehyde material is a large chemical industry intermediate and has no commercial product supply, if the large chemical industry is left for producing the isooctanoic acid, only another method for producing the isooctanoic acid by taking octanol as a raw material can be adopted. The process for producing the isooctanoic acid by using the octanol as the raw material has various methods, but has the defects of high production cost, large investment, high raw material and energy consumption, serious equipment corrosion, low product yield, low yield, high public expense, difficulty in forming large-scale production and unsuitability for industrial production.

The existing method for producing isooctanoic acid by using isooctanol mainly comprises the following five methods, including a potassium permanganate oxidation method, a nitric acid oxidation method, a high-pressure dehydrogenation oxidation method, a normal-pressure dehydrogenation oxidation method and a catalytic dehydrogenation esterification method.

The potassium permanganate oxidation method is to prepare isooctanoic acid by using isooctanol and potassium permanganate as oxidant in the presence of NaOH. The method has the defects of poor oxidation catalysis effect, low product yield, long process flow, side reaction, large raw material consumption, certain corrosion to equipment, high cost and low performance index of the obtained product, so that the possibility of large-scale production does not exist.

The nitric acid oxidation method uses ammonium vanadate as a catalyst in addition to nitric acid as an oxidizing agent. The method has the defects that nitric acid has strong corrosivity, high requirements on equipment corrosion resistance and large equipment investment, harmful gas NO is emitted in the reaction process, esterification is easy to generate, carboxylic acid can be obtained only by hydrolysis, and the complexity of the process flow is increased, so that large-scale production is not easy to realize.

The high pressure dehydrogenation oxidation method is that isooctanol and sodium hydroxide react under high pressure, dehydrogenation and oxidation are carried out to generate 2-ethyl caproic acid sodium, and then the isooctanoic acid is obtained after acidification by sulfuric acid. The method has the disadvantages that the reaction is required to be carried out at higher temperature and pressure, the operation is difficult, the equipment corrosion is serious, the requirement on the equipment is strict, the engineering investment is increased, and the large-scale production is not easy to realize.

The normal pressure dehydrogenation oxidation method is based on the high pressure dehydrogenation oxidation method, adopts metal oxide as catalyst, and dehydrolyzes isooctyl alcohol and sodium hydroxide under normal pressure to obtain isooctanoic acid. The method has the defects of long process flow, low product yield, difficult catalyst recovery, large raw material and energy consumption, low performance index of the obtained product and no possibility of large-scale production.

The catalytic dehydrogenation esterification method is to perform dehydrogenation reaction on isooctyl alcohol under the catalysis of metal oxide at the reaction temperature of 180-210 ℃ to generate diisooctyl ester. The method has the disadvantages that the method is used in two processes of esterification and saponification, thereby reducing the utilization rate of isooctanol, and simultaneously, the product cost is increased due to the rectification process, and the method is less applied industrially.

In addition, although there are electrolytic oxidation and ultrasonic methods, random molding is possible because of high production cost and low product performance index.

Patent CN200610045996.3 discloses a method for preparing isooctanoic acid by a composite catalytic method; the reactants are isooctanol and sodium hydroxide, the catalyst is a composite catalyst formed by combining calcium oxide, vanadium pentoxide and rare earth oxide, the temperature of the alcohol-base oxidation reaction is 240-280 ℃, the reaction time is 1.8-2.2h, hydrogen is removed, the solid catalyst is filtered out, sulfuric acid is added for acidification reaction, and then the isooctanoic acid product is prepared by decompression and dehydration. The catalyst has high activity, short oxidation reaction time, less side reaction, no need of rectification, and dehydration to obtain the finished product, thereby improving the production efficiency and reducing the production cost.

Patent CN200710189641.6 discloses a method for preparing isooctanoic acid, wherein isooctanol and sodium hydroxide react under the condition of 250-260 ℃ temperature and 2.8-3.2MPa pressure by using zinc acetate as catalyst under the inert atmosphere until no hydrogen is generated, then the reaction is carried out for 30-50min under pressure maintaining, then crude isooctanoic acid is obtained by acidification at 65-80 ℃, and the refined isooctanoic acid is obtained by rectification and purification. The production period of the product is 8-10h, and the purity of the product can reach 99.5%.

Patent CN85108701 discloses a method for preparing isooctanoic acid by catalytic oxidation of isooctanol, which takes lead oxide as a catalyst, the oxidation reaction temperature is 210 ℃, the heating is carried out for 3-4h, the heat preservation reaction is carried out for 1h, the temperature is reduced to 100 ℃, and sulfuric acid is added for acidification to obtain the isooctanoic acid product. The conversion rate of isooctanol reaches 98.65 percent.

The three patents all adopt an alcohol-alkali oxidation method to prepare the isooctanoic acid, and all have the problems of high alcohol-alkali oxidation reaction temperature and high pressure, thereby not only bringing potential safety hazards to the operation of the device, but also improving the equipment investment and the production cost.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a process method for preparing isooctanoic acid. The method has the advantages of easy recovery of the catalyst, mild reaction conditions, low production cost, high yield, short reaction time, shortened production period and continuous industrial mass production.

The process method for preparing the isooctanoic acid specifically comprises the following steps: putting two materials of isooctanol and sodium hydroxide into a fixed bed reactor, oxidizing under the condition of inert atmosphere, and using TiO₂-CeO₂The metal oxide is used as a catalyst and reacts until no hydrogen is generated; and (3) decompressing the material at the outlet of the fixed bed reactor, feeding the material into an acidification tank, carrying out acidification treatment on the material by using sulfuric acid, stirring for 20-40 min, standing for layering, draining off a water layer, washing for three times, and finally carrying out decompression, dehydration and rectification to obtain an isooctanoic acid product.

Wherein:

TiO₂-CeO₂the mass of the metal oxide catalyst accounts for 5-8% of that of the isooctyl alcohol.

The mass fraction of isooctyl alcohol is 99%, and the mass fraction of sodium hydroxide is 30-40%.

The mass ratio of isooctanol to sodium hydroxide is 1: 1.1-1.3, preferably 1: 1.2.

Putting two materials of isooctanol and sodium hydroxide into a fixed bed reactor, namely respectively putting isooctanol and sodium hydroxide at an airspeed of 1h^-1～2h^-1。

TiO₂-CeO₂The metal oxide is coated on the gamma-Al by adopting a dipping-sintering process₂O₃TiO formation on the surface of the molecular sieve₂-CeO₂A metal oxide catalyst; TiO 2₂-CeO₂The loading amount of the metal oxide is 4 percent of the total mass of the catalyst; wherein the TiO is₂Accounting for 85 percent of the specific surface area of the catalyst coating and a catalyst promoter CeO₂Accounting for 15 percent of the specific surface area of the catalyst coating.

The above specific surface area is also an effective surface area for the catalyst action.

The operating conditions of the fixed bed reactor were: under the condition of inert atmosphere, the temperature is 210-225 ℃, and the preferable temperature is 215-220 ℃; the pressure is 2-4 MPa, preferably 2.5-3 MPa.

The material is decompressed at the outlet of the fixed bed reactor and enters an acidification pool, and the pressure is normal pressure.

The concentration of the sulfuric acid solution is 30-40%, preferably 35%; the pH value after the acidification treatment is 2.5-3.5, and the preferable pH value is 3.

The invention changes the original stirring process of the reaction kettle into the fixed bed load with low flow rate through the load of the catalyst, reduces the filtering process and can reduce the reaction time by about 2 to 3 hours compared with the prior art.

The reaction mechanism of the present invention is as follows:

due to the fact thatγ-Al₂O₃Is a defective spinel structure with two crystal lattice vacancies on the preferentially exposed surface, and supported metal cations can be selectively inserted into the vacancies to form a spinel crystal phase, and the supported Ti ions enter Al₂O₃TiAl generated after lattice₂O₃Spinels, have a catalytic effect in a variety of oxidation reactions.

The rare earth element has larger ionic radius, and the surface structure of the active component can be changed by doping the rare earth element in the catalyst to form a special composite oxide. CeO (CeO)₂The rare earth oxide is a composite oxide which shows special oxidation-reduction property in reaction, has large ion radius of rare earth elements, can change the surface structure of an active component and forms a special structure with other components in a catalyst. CeO (CeO)₂① can improve the dispersion degree of noble metal on the carrier surface, ② has excellent oxygen storage capacity, can absorb oxygen under the condition of sufficient oxygen and release oxygen under the condition of oxygen deficiency to improve the catalytic activity of the catalyst, ③ can also make the model structure more stable, prevent volume shrinkage and improve the mechanical strength of the catalyst carrier₂As an auxiliary agent, the catalytic activity of the catalyst in the reaction of oxidizing isooctyl acid by isooctanol can be improved.

The invention adopts a fixed bed reactor, and the loaded molecular sieve catalyst is used for bed layer fixation, thereby reducing the loss of the catalyst surface activity caused by the stirring of the reaction kettle. The high activity system containing the cocatalyst can ensure the reaction conversion rate when the fixed bed is circulated at low airspeed, simultaneously reduce the technical process of catalyst filtration and shorten the production period.

As a preferred technical scheme, the process for preparing isooctanoic acid of the present invention specifically comprises the following steps: oxidizing isooctanol and sodium hydroxide in inert atmosphere to obtain TiO₂-CeO₂The metal oxide is used as a catalyst and is loaded on the gamma-AI₂O₃On a molecular sieve, under the conditions of the temperature of 210-225 ℃ and the pressure of 2-4 MPa, the space velocity is 1h^-1～2h^-1Respectively to be provided withPutting the two materials into a fixed bed reactor to react until no hydrogen is generated, decompressing the materials at the outlet of the reactor, entering an acidification tank, carrying out acidification treatment on the materials by adopting 30-40% sulfuric acid, keeping the pH value at about 2.5-3.5, stirring for 20-40 minutes, standing, layering, draining off a water layer, washing for 3 times, and finally carrying out decompression, dehydration and rectification to obtain an isooctanoic acid product.

Compared with the prior art, the invention has the following beneficial effects:

(1) the catalyst is TiO₂-CeO₂The metal oxide can ensure the stability of the pH value of the reaction environment under the condition of low space velocity and accelerate the reaction rate.

(2) The catalyst provided by the invention is applied to a fixed bed reactor, can be repeatedly used, has a longer service life, reduces the washing process compared with other catalysts, and shortens the production period.

(3) Because of TiO₂-CeO₂The activity of the metal oxide catalyst is higher because of the catalyst promoter CeO₂The addition of (2) has mild reaction conditions, and the conversion rate can be ensured to reach 99.3% under the condition of low airspeed.

(4) By taking a set of conventional isooctanoic acid production device with 0.5t/h as an example, the catalyst and the fixed bed reactor of the invention can reduce the device operation period by 10-20% and increase the annual benefit by more than 10%.

(5) The technical method for preparing the isooctanoic acid has the advantages of easy recovery of the catalyst, mild reaction conditions, low production cost, high yield, short reaction time, shortened production period and continuous industrial scale production.

Detailed Description

The present invention is further described below with reference to examples.