CN115745793A - Method and catalyst for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde - Google Patents

Abstract

The invention relates to a method and a catalyst for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde, belonging to the technical field of chemical processes. Is characterized in that aldehyde is used as a raw material and continuously flows through a reactor filled with a mixed metal oxide solid catalyst to carry out gas-solid catalytic reaction, and ester is synthesized by one step. The product and the catalyst are automatically separated, and the method is suitable for automatic continuous large-scale production.

Description

Method and catalyst for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde

Technical Field

The invention relates to a method and a catalyst for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde, belonging to the technical field of chemical processes.

Background

Isobutyl isobutyrate is a medium boiling point solvent and chemical raw material, and the demand is increasing. The industrial production method of isobutyl isobutyrate synthesizes isobutyraldehyde through propylene hydroformylation, isobutyraldehyde is oxidized into isobutyric acid, isobutyraldehyde is hydrogenated into isobutanol, isobutyric acid and isobutanol react under catalysts such as sulfuric acid and the like to generate the isobutyric acid, and the isobutyric acid and the isobutanol are generated by several devices of 4 factories or workshops. Therefore, there has been a report on the development of a method for synthesizing isobutyl isobutyrate from isobutyraldehyde in one step.

In journal 2004, phase 11 of the chemical development, isobutyraldehyde is used as a raw material, retention time is 1.5-2 h at 5-10 ℃, and two molecules of isobutyraldehyde are condensed to synthesize one molecule of isobutyl isobutyrate under the action of an isobutoxy aluminum catalytic system. After the catalyst is removed, the crude product is refined to obtain isobutyl isobutyrate with the purity of more than or equal to 99.5 percent, the conversion rate of isobutyraldehyde is more than or equal to 98.5 percent, and the selectivity of isobutyl isobutyrate is more than or equal to 95.0 percent.

In journal of chemical engineering, 2019, phase 4, the method is reported that isobutyl isobutyrate is prepared in one step by catalyzing two molecules of isobutyraldehyde Tishchenko reaction with aluminum isobutylate as a catalyst, and the research on the synthesis process conditions of isobutyl isobutyrate is carried out by a one-factor experimental method, so that the better synthesis process conditions are determined to be m (aluminum isobutylate): m (isobutylaldehyde) = 1: 10, the reaction temperature is 10 ℃, and the reaction time is 3.5 hours. Under the process conditions, the conversion of isobutyraldehyde was greater than 99.0% and the yield of isobutyl isobutyrate was greater than 95.0%.

The great thesis of Quya Men, qingdao university of science and technology (2019) introduced that acetylacetone metal salt was used as a series of homogeneous catalysts to catalyze Tishchenko reaction of isobutyraldehyde, wherein m (zirconium acetylacetonate/silica gel) =10% m (isobutyraldehyde), isobutanol was used as a solvent, the reaction temperature =160 ℃, the reaction pressure =0.75MPa, and the reaction time =6.0h, and under the preferred process conditions, the yield of isobutyl isobutyrate was 73.27%, and the catalyst still maintained high activity after 3 times of repeated use.

Chinese patent (CN 03111256) describes the condensation of isobutyl isobutyrate from isobutyraldehyde as raw material under the action of a catalyst system mainly comprising aluminium alkoxide at-30-20 deg.C for 0.5-5 hours. The dosage of the main catalyst is 0.05 to 1.00g of aluminum per 100g of isobutyraldehyde, and the dosage of the cocatalyst is 0.01 to 10.00g per 100ml of main catalyst.

The above reported synthetic methods are homogeneous catalytic reactions, although it has the advantage of mild reaction conditions, the reaction speed at low temperature is very slow, the production scale is limited, the heat released by the reaction cannot be effectively utilized, the catalyst preparation cost is high, the separation of the catalyst from the raw materials and products needs to be solved after the reaction, the catalyst needs to be deactivated and then regenerated to reduce side reactions, the post-treatment is troublesome, and the intermittent operation is difficult for continuous large-scale production.

Chinese patent (CN 202011059503.8) discloses that carbon black is used as an inert matrix, a spatial synthesis method is combined with a hydrothermal microwave method to synthesize a nano CuO-MxOy (M = Ce, cr, ti) carrier with a mesoporous structure, a supercritical fluid impregnation method is used to load aluminum iso-butoxide on the surface of the carrier to prepare a catalyst, and iso-butyl isobutyrate is synthesized from iso-butyraldehyde in one step. The nature of this should be heterogenisation of the homogeneous catalyst aluminum iso-butoxide.

Chinese patent (CN 202010840615.0) discloses a preparation method of a graft catalyst for synthesizing isobutyl isobutyrate by isobutyraldehyde catalysis, which is characterized in that: the preparation method comprises the following steps: (1) Dispersing the carrier in washing liquid, putting the washing liquid in an ultrasonic cleaning machine for ultrasonic treatment, and stirring for acidification; repeatedly washing the acidified carrier with distilled water to neutrality, and drying overnight to obtain an acidified solid carrier; (2) Heating 2-hydroxy-N-methylacetamide in a container, introducing nitrogen for protection, adding excessive simple substance sodium, and stirring at the same temperature for reaction to obtain organic sodium salt; (3) And (3) filtering the organic sodium salt obtained in the step (2), adding the filtered organic sodium salt and the carrier acidified in the step (1) into ethanol, stirring, filtering the stirred liquid, and drying to obtain the graft catalyst. The preparation of the catalyst is rather cumbersome, especially with an excess of elemental sodium.

In addition, no report on a method and a catalyst for synthesizing isobutyl isobutyrate from isobutyraldehyde in one step is found.

Disclosure of Invention

In order to overcome the defects of the reported method, the invention discloses a method and a catalyst for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde in one step.

The reaction takes isobutyraldehyde as a raw material, and two isobutyraldehyde molecules synthesize an isobutyl isobutyrate molecule:

2(CH ₃ ) ₂ CHCHO＝(CH ₃ ) ₂ CHCOOCH ₂ CH(CH ₃ ) ₂ (1)

the reaction mechanism is different from the general direct condensation reaction mechanism and process, on different activity centers of the same catalyst, two aldehyde molecules are disproportionated into acid and alcohol under the participation of water, the acid and the alcohol are re-esterified to obtain ester and discharge water, and the two series reactions belong to one-step in-place reaction from a macroscopic view:

2(CH ₃ ) ₂ CHCHO+H ₂ O＝(CH ₃ ) ₂ CHCOOH+(CH ₃ ) ₂ CHCH ₂ OH (2)

(CH ₃ ) ₂ CHCOOH+(CH ₃ ) ₂ CHCH ₂ OH＝(CH ₃ ) ₂ CHCOOCH ₂ CH(CH ₃ ) ₂ +H ₂ O (3)

the invention uses a fixed bed (also can be a fluidized bed or a micro-channel) reactor to carry out gas-solid phase catalytic reaction. The solid catalyst is contained in the reactor. The raw material aldehyde is sent out by a pump, preheated to be close to the reaction temperature to be gas, and then enters the reactor from the upper part of the fixed bed reactor for reaction. The reaction product is led out from the lower part of the reactor, exchanges heat with the raw material to recover heat, is cooled by water to form liquid, and is rectified and separated to remove unreacted raw material, so that the product is obtained.

The reaction format of the present invention is of the continuous flow type. In the process parameters, the flow rate of the aldehyde raw material is expressed by weight space velocity (weight flow rate kg of raw material/weight kg of catalyst. Multidot.h, abbreviated as h) ^-1 ) In the range of 0.2 to 5.0h ^-1 . The weight space velocity is physically defined as the weight of feed flowing over a unit weight of catalyst and is therefore also referred to as catalyst loading. The reaction temperature is 250-350 ℃. The reaction pressure is 0.1-3.0 MPa. Because of the molecular weight reduction reaction, pressurization is advantageous for chemical equilibrium, and the throughput can be increased. From the actual operating temperature and pressure, the residence time of the feedstock on the catalyst can be calculated, in the order of seconds to tens of seconds.

According to the reaction process, water in the raw materials only participates in the reaction, the water is not consumed after the reaction, the disproportionation reaction of the aldehyde is considered as a speed control step, the participation of water is needed, the intersolubility of the aldehyde and the water is poor, and some water is necessarily added when the water content in the aldehyde is low, so that the reaction speed is favorably improved, but the acid is generated by side when too much water is added.

It is advantageous to add an appropriate amount of isobutanol to the feed. Firstly, because the aldehyde synthesized ester is an exothermic reaction with medium intensity, after the alcohol is added, the alcohol is dehydrogenated into the aldehyde, which is an endothermic reaction, so that the total reaction exotherm is reduced, and the reaction is more stable and easy to control. Secondly, alcohol can react with acid, so as to reduce the acid content in the product. Thirdly, hydrogen gas is released when alcohol is dehydrogenated into aldehyde, so that the reaction pressure is stable and easy to control.

The key of the method provided by the invention is to design and use the catalyst. The catalyst is a solid mixed oxide MOx, wherein M is metal elements Cu, al, mn, zn, zr and rare earth elements, the weight composition range of each metal element is Cu =20-30%, al =0-30%, mn =0-15%, zn =0-30%, zr =10-30%, rare earth =0-5%, and x is the total number of oxygen atoms meeting the valence of each element in the catalyst.

The method of the invention has the following outstanding advantages:

1) The gas-solid catalytic reaction process has simple process and equipment, and the reaction material and the catalyst are easy to separate, so that the method is suitable for continuous large-scale production.

2) The reaction by-products are less, and the atom economy is strong. No pollution and no waste residue discharge, and is an environment-friendly production process.

3) The catalyst does not contain noble metal and elements harmful to the ecological environment, and the preparation method is simple.

4) The reaction is a medium-intensity exothermic reaction, can produce water vapor as a byproduct, and partially meets the heat energy required by separation.

Detailed Description

The specific embodiment of the invention is as follows:

the solid catalyst is placed in the reaction tube of a fixed bed reactor. Before the reaction starts, H is used ₂ /N ₂ And (3) carrying out catalyst reduction on the mixed gas, namely reducing CuO in the catalyst components into metal Cu. After the temperature of the catalyst bed rises to the reaction temperature, the reduction process is finished. Pumping raw material aldehyde by a pump, exchanging heat with a reaction product and heating to a reaction temperature to form gas, entering the reactor from the upper part of the reactor to perform gas-solid catalytic reaction, enabling the reaction product to flow out from the bottom of the reactor, exchanging heat with the raw material and cooling by water to form liquid. After unreacted raw material aldehyde and byproducts are removed by rectification, the product ester is obtained. For the tubular reactor, the reaction temperature is controlled by the heat conducting oil flowing between the tubes, and for the single-tube reactor, the temperature can be controlled by electric heating or air cooling so as to carry out isothermal reaction. The reaction pressure is controlled by a product outlet valve in the water cooler.

Example 1:

4g of mixed metal oxide solid catalyst was placed in the middle of a stainless steel single-tube reactor having a size of 20X 3X 300mm, and both ends were filled with inert coarse quartz sand at fixed positions. The catalyst metal composition by weight Cu =25%, mn =15%, zn =30%, zr =30%. The temperature of the reactor was controlled by a temperature controller. H for catalyst ₂ /N ₂ After the temperature of the mixed gas is programmed to be increased to the reaction temperature for reduction and the temperature is increased to the reaction temperature, isobutyraldehyde (the water content is 0.1%) is pumped in by a metering pump. The isobutyraldehyde is preheated to about 250 ℃ by a preheater and enters a reactor. The reaction conditions are as follows: weight space velocity of the raw material liquid is 1h ^-1 The reaction temperature is 250 ℃, and the reaction pressure is 1.0MPa. And after the gas reaction product flows out, the gas reaction product directly enters a water cooler, is cooled into liquid, and is separated to obtain an ester product. The chromatographic analysis gave isobutyraldehyde conversion of 30% and ester selectivity of 85% with the by-products being predominantly unreacted isobutanol and isobutyric acid. They can be added into raw materials for recycling.

Example 2:

the catalyst component is CuAlLaZnZrO mixed metal oxide, and the weight composition of the catalyst metal comprises Cu =30%, al =25%, la =5%, zn =10%, and Zr =30%. Adding water accounting for 2 percent of isobutyraldehyde into raw material isobutyraldehyde, wherein the liquid weight space velocity is 1h ^-1 The reaction temperature is 260 ℃ and the reaction pressure is 2.0MPa. The aldehyde conversion was 50% and the ester selectivity was 90%, the other conditions being the same as in example 1.

Example 3:

the catalyst component is CuAlLaZnZrO mixed metal oxide, and the catalyst metal weight composition is Cu =30%, al =30%, la =3%, zn =12%, and Zr =25%. Isobutyl alcohol accounting for 10 percent of isobutyraldehyde is added into raw material isobutyraldehyde, and the liquid weight space velocity is 1.5h ^-1 The reaction temperature is 270 ℃ and the reaction pressure is 3.0MPa. The aldehyde conversion was 60% and the ester selectivity was 95%, the other conditions being the same as in example 1.

Claims (5)

1. A process for synthesizing isobutyl isobutyrate by disproportionation of isobutyraldehyde features that the isobutyraldehyde is used as raw material and heated to become isobutyraldehyde, which flows through a reactor containing solid catalyst to synthesize isobutyl isobutyrate in one step.

2. The process of claim 1, wherein the reactor is a fixed bed, fluidized bed or microchannel reactor and the reaction is a gas-solid phase catalytic reaction.

3. The process of claim 1, wherein the solid catalyst is a mixed metal oxide having a composition MOx, wherein M is the metal elements Cu, al, mn, zn, zr, and rare earth elements, the composition ranges of the metal elements by weight Cu =20-30%, al =0-30% Mn =0-15%, zn =0-30%, zr =10-30%, rare earth =0-5%, and x is the total number of oxygen atoms satisfying the valence of each element in the catalyst.

4. The process of claim 1, wherein the reaction is carried out in a continuous flow type in which the raw material is continuously fed into the reactor, the space velocity of the feed weight is 0.2 to 3h-1, the reaction temperature is 250 to 350 ℃, and the reaction pressure is 0.1 to 3MPa.

5. The process of claim 1 wherein the isobutyraldehyde starting material comprises 0-5% water and 0-30% isobutanol, based on the weight of isobutyraldehyde.