CN1149047A

CN1149047A - Diethyl oxalate by gas phase CO link-coupled regeneration catalyzing circulation

Info

Publication number: CN1149047A
Application number: CN 96109811
Authority: CN
Inventors: 许根慧; 马新宾; 李振花; 何菲; 陈洪钫; 陈锦文
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 1996-09-18
Filing date: 1996-09-18
Publication date: 1997-05-07
Anticipated expiration: 2016-09-18
Also published as: CN1056135C

Abstract

A gas-phase process for preparing diethyl oxalate includes gas-phase CO coupling, regeneration andcatalytic cycle. Under the existance of ethylnitrite, CO is catalytically coupled to generate diethyl oxalate at 100-120 deg.C and 0.1 MPa for 1-3 seconds. After condensing the resultant gas, condensed colourless transparent diethyl oxalate liquid with 99% of impurity is obtained. The NO gas which is not condenced goes into regenerating tower to generate ethyl nitrite for reuse. It uses load-type bimetal solid catalyst Pd-Fe/Al2O3.

Description

Gas phase method CO coupling regeneration catalytic circulation preparationof diethyl oxalate

The present invention belongs to a catalytic reaction process of chemical engineering.

Diethyl oxalate and oxalic acid are important organic chemical raw materials and intermediates, and are widely used in the industries of chemical industry, metallurgy, pharmacy and the like. At present, the sodium formate method and the nitric acid oxidation method are mostly adopted in domestic oxalic acid production, the cost of the used raw materials is high, the pollution is serious, and a certain gap exists between the cost and the international advanced level. The production route of oxalic acid is continuously updated in foreign countries, and the seventies are mainly based on the development of petrochemical industry, and the raw material route is improved, for example, the yield of oxalic acid can reach more than 90 percent based on propylene by synthesizing oxalic acid by a propylene oxidation method in French Roner-Planck company. In the eighties, as petroleum energy has been in crisis, new raw material routes of monocarbonization chemical, which replace petroleum with coal, are developed internationally, for example, united states carbon company and japan udon product company have developed and researched the research of preparing dimethyl oxalate by gas phase method coupling catalysis of synthesis gas CO and preparing ethylene glycol by pressurized hydrogenation, the method was proposed by D.M. Fenton et al as early as 1965, and the research has found that dialkyl oxalate is synthesized by CO coupling. In the early stage, oxalate is synthesized by CO pressurized liquid phase reaction, and in 1978 Nippon Yudu, a 6000-ton liquid phase method production device for producing oxalic acid annually is built. In order to improve the deficiency of the liquid phase process, gas phase process research procedures have been proposed in recent years. In 1983, a patent report on the preparation of oxalic acid by CO coupling gas phase method was published in Japan Yudu xing (U.S. P.4 '453' 026, 1983), which is the preparation of dimethyl oxalate by CO catalytic coupling and the preparation of oxalic acid by hydrolysis of dimethyl oxalate. The gas phase method overcomes the defects of the liquid phase method, and has mild reaction conditions and less catalyst loss. In China, palladium chloride and copper chloride are used as catalysts in southwest chemical research institute at the earliest time, and a liquid phase method is used for synthesizing diethyl oxalate, wherein the conversion rate of ethanol is 18.03%, and the selectivity of diethyl oxalate is 79.63%. The Chinese academy of health, Fujian institute of health and south China university, etc. have successively conducted CO coupling gas phase method research, and in 1985, professor Chen-Pingchen of the Chinese academy of health, etc. applied for the invention of Chinese patent, "CO catalyzed coupling to synthesize oxalic acid" (application date: 85 years, 4 months, 1 days, application number: 85101616), which proposes a process route for producing dimethyl oxalate by the reaction of CO and methyl nitrite on a palladium-supported activated alumina catalyst.

In conclusion, the catalytic reaction for preparing diethyl oxalate by gas-phase CO coupling is a new process route in the synthesis of oxalate and oxalic acid at present, wherein the synthesized diethyl oxalate is hydrolyzed to prepare oxalic acid, and then is hydrogenated to obtain glycol and aminated to obtain organic chemical products such as ammonium oxalate and the like.

The invention aims to overcome the defects in the production of oxalate and the synthesis of oxalic acid at present, provides a process for preparing diethyl oxalate by cyclic coupling, regeneration and catalysis of CO in a gas phase method with ethyl nitrite, and the process adopts a self-closed cyclic process, has mild reaction conditions, high catalyst selectivity, good stability, good product quality and no three-waste pollution. The reaction equation is as follows:

coupling reaction: (1)

and (3) regeneration reaction: (2)

the invention is characterized in that a gas phase method is adopted, CO is subjected to coupling, regeneration and catalytic circulation under the participation of ethyl nitrite to prepare diethyl oxalate, the reaction temperature is 100-120 ℃, the pressure is 0.1MPa, the reaction contact time is 1-3 seconds, the gas obtained from the coupling reaction is condensed, separated and collected to obtain colorless and transparent diethyl oxalate condensate with the weight percent of more than 99 percent, the non-condensable gas containing NO enters a regeneration tower, the ethyl nitrite generated by the regeneration reaction is recycled to a coupling reactor for continuous use, and the catalyst is Pd-Fe/Al₂O₃The supported bimetallic solid catalyst has Pd0.1-1 wt% and Fe0.3-2 wt% of carrier, and has space time yield STY of 700 g product/liter hour.As can be seen from the above reaction process, the reaction equation (1) is CO coupling catalytic reaction, generating diethyl oxalate in the presence of ethyl nitrite with accompanying NO gas, the reaction equation (2) is that NO is regenerated in the presence of ethanol and oxygen to obtain ethyl nitrite, and the ethyl nitrite is returned to the coupling reaction process for recycling use, as can be seen from the above reaction equation,in the reaction process, the ethyl nitrite and the NO can be recycled, and only CO and a small amount of oxygen are actually consumed in the process. If the product is oxalic acid instead of diethyl oxalate, the ethanol can be further recovered by oxalic ester hydrolysis, so the method has the characteristics of simple and reasonable raw material route, low cost, good yield, no pollution and the like.

The technological process of the gas phase method CO coupling, regeneration and catalytic cycle diethyl oxalate preparation is shown in figure 1.

In the figure:

1-mixer, 2-coupling reactor, 3-condensation separator,

4-a product storage tank, 5-a regeneration tower, 6-a partial condenser,

7-tail gas purifier, 8-alcohol-water rectifying tower, 9-condenser,

10-gas circulating pump, 11-regenerated liquid storage tank, 12-liquid pump,

13-ethanol storage tank, 14-ethanol feeding pump, 15-ethanol inlet,

16-oxygen inlet, 17-N₂A gas inlet.

The technological process mainly comprises a CO coupling reactor, an ethyl nitrite regeneration reactor and an alcohol-water rectifying tower, and is described as follows:

the method comprises the following steps of enabling a mixed raw material gas obtained by mixing purified CO and ethyl nitrite from a regeneration tower 5 through a mixer 1 to enter a coupling reactor 2, enabling a product obtained after reaction to pass through a condensation separator 3, collecting a product diethyl oxalate into a product storage tank 4, enabling most of uncondensed circulating gas NO to enter the regeneration tower 5 through a gas circulating pump 10, enabling a small amount of uncondensed circulating gas NO to be discharged after being purified through a tail gas purifier 7, enabling reaction gas at the top of the regeneration tower 5 to be subjected to fluttering collection through a partial condenser 6 to return to the regeneration tower 5, enabling the uncondensed gas to be ethyl nitrite and enter the mixer 1 to be mixed with the purified raw material gas CO. The liquid discharged from the bottom of the regeneration tower 5 is put into a storage tank 11, and is sent into an alcohol-water rectifying tower 8 by a liquid pump 12, the ethanol evaporated from the top is condensed by a condenser 9, flows into an ethanol storage tank 13, and is returned to the regeneration tower for recycling by a feed pump 14, and the wastewater liquid at the bottom of the rectifying tower can be returned to an industrial water system. Ethanol is supplemented by line 15.

The source of the raw material gas for purification, namely CO, is not limited, and can be used for preparing synthesis gas from coal, urban coal gas, steel mill waste gas and flue gas, the content of purified CO is more than 50 percent (mole percentage), and the purified CO can be used for CO contained in CO₂Can be regarded as inert gas, does not influence the reaction effect. The raw material gas is mixed at the inlet of the coupling reactor, the composition is controlled to be (mol%) CO-25-35%, and C₂H₅ONO-9～22％，NO-4～11％，CO₂-1 to 5% and the balance N₂。

Examples of the invention are now described below and can be considered as an addition to the description of the reaction process.

Example (1). 20ml of catalyst with the particle size of 1.2mm is weighed and placed in a tubular fixed bed reactor, the inner diameter of the reactor is 25mm, the length of the reactor is 480mm, inert fillers with the same particle size as the catalyst are filled above and below a reaction bed layer to ensure that reaction airflow is preheated and uniformly distributed, an automatic temperature control device is adopted to ensure that the temperature deviation of thereaction bed layer is not more than +/-0.5 ℃, and the reaction can be regarded as isothermal plug flow operation.

Mixing purified feed gas CO with ethyl nitrite from a regeneration tower, and feeding the mixture into a coupling reactor, wherein the inlet feed composition (mol%) of the reactor is as follows: CO 26%, CO ₂4％、C₂H₅ONO10％、NO5％、N₂55 percent of mixed raw material gas enters from the upper end of the reactor and is discharged from the bottom of the reactor after reaction. The reaction conditions are as follows: the reaction temperature is 110 ℃, the reaction pressure is 0.1MPa, the reaction contact time is 1.4 seconds, and the gas after the reaction is condensed and separated, and the product is collected in a storage tank. The obtained product was a colorless transparent liquid, and the product purity by chromatography was 99.8% diethyl oxalate (wt%), and the remaining small amount of components were ethyl formate and ethyl carbonate by-products. The composition of the non-condensable gas after the reaction (mol%) is as follows: CO 12%, ethyl nitrite 5%, NO 13%,CO₂4.8% and the balance N₂. The gas is sent into a regeneration tower through a gas circulating pump, the regeneration tower is a gas-liquid turbulent flow packed tower, and the gas is continuously introduced into the regeneration tower according to the online monitoring of the chromatogramAnd (2) reacting oxygen and ethanol added according to a stoichiometric ratio with NO noncondensable gas discharged by the coupling reaction to generate ethyl nitrite, wherein the regeneration tower is operated at normal temperature and normal pressure, the reaction contact time is 1-2 seconds, a product ethyl nitrite after the reaction is discharged from a tower top partial condenser and sent to the coupling reactor for recycling, generated water and unreacted ethanol are sent to an alcohol-water rectifying tower from the tower bottom, water is separated, and 98% (mol%) of ethanol distilled from the tower top is returned to the regeneration tower for recycling. In order to ensure that the inert gas in the uncondensed circulating gas does not need to be discharged in a small amount in an accumulated manner and the concentration of each component is stable, the composition of the inert gas is directly monitored and controlled on line by chromatographic analysis, and the discharge amount is related to the operation condition and the activity of the catalyst. The determined amount of air released in this example is 2% or less of the total amount of circulating gas. The reaction process is carried out in a gas-phase continuously operated circulation system. The catalyst has stable activity after 1000 hours of stability test, and the space time yield STY of the catalyst is 700 (g product/liter per hour). The catalyst composition is Pd_0.3Fe_0.5/Al₂O₃。

Example (2). Weighing 30ml of cylindrical catalyst with the diameter of 3mm and the length of 4mm, placing the cylindrical catalyst into a tubular fixed bed reactor, wherein the inner diameter of the reactor is 25mm, the length of the reactor is 480mm, and inert fillers of particles such as the catalyst and the like are filled above and below a reaction bed layer.

Mixing purified feed gas CO with ethyl nitrite from a regeneration tower, and feeding the mixture into a coupling reactor, wherein the inlet feed composition (mol%) of the reactor is as follows: CO 30%, CO ₂2％，、C₂H₅ONO 20％、NO 10％、N₂38 percent of mixed raw material gas enters from the upper end of the reactor and is discharged from the bottom of the reactor after reaction. The reaction conditions are as follows: the reaction temperature is 120 ℃, the reaction pressure is 0.11MPa, the reaction contact time is 2.5 seconds, gas is condensed and separated after the reaction, a liquid product diethyl oxalate is collected into a product storage tank, the product purity is 99.75 percent (weight percent), and the rest small amount of impurities are ethyl formate and ethyl carbonate. The composition of the non-condensable gas after the reaction (mol%) is as follows: CO 18%, ethyl nitrite 9.2%, NO 19.4%, CO₂2.7% and the balance of N₂The gas is sent to a regeneration tower by a gas circulating pump and thenThe method comprises the following steps of (1) continuously introducing metered oxygen and ethanol according to a stoichiometric proportion to react with non-condensable gas discharged by coupling reaction according to a chromatographic on-line monitoring result to generate ethyl nitrite, wherein the regeneration tower is operated at normal temperature and normal pressure, the reaction contact time is 1-2 seconds, a product ethyl nitrite after reaction is discharged from the tower top through a partial condenser and is sent to a coupling reactor for recycling, generated water is condensed and then sent to an alcohol-water rectifying tower from the tower bottom, water is separated out, 98% (mol%) ethanol distilled from the tower top is returned to the regeneration tower for recycling, and the process is carried out in a circulating system of gas-phase continuous operation. The catalyst has stable activity after 1000 hours of stability test, the space time yield STY of the catalyst is 780 (g product/liter. hour), and the used catalyst has the composition of Pd_0.5Fe_0.5/Al₂O₃。

Claims

1. A gas-phase process for preparing diethyl oxalate by CO coupling, regeneration and catalytic circulation is characterized in that a gas-phase process is adopted, CO is catalyzed and coupled to generate diethyl oxalate under the participation of ethyl nitrite, the reaction temperature is 100-120 ℃, the pressure is 0.1MPa, the reaction contact time is 1-3 seconds, the reaction is a self-closed circulation process, mixed raw material gas formed by mixing purified raw material gas CO and ethyl nitrite from a regeneration tower enters a coupling reactor, gas after the reaction from the coupling reactor is condensed, separated and collected to obtain colorless and transparent diethyl oxalate condensate with the weight percent of more than 99 percent, non-condensable gas containing NO enters a regeneration tower, ethyl nitrite generated by regeneration reaction is recycled to the coupling reactor for continuous action, generated water and unreacted ethanol are sent to an alcohol-water rectifying tower, the ethanol is separated out and sent to the regeneration tower for recycling, the regeneration tower is a gas-liquid turbulence packed tower, the operation is carried out at normal temperature and normal pressure, the reaction contact time is 1-2 seconds, the introduced oxygen and ethanol are continuously introduced according to the stoichiometric ratio based on-line monitoring, and the catalyst is Pd-Fe/Al₂O₃The bimetallic supported catalyst comprises 0.1-1% of Pd0.1 and 2% of Fe0.3 (weight percent based on the carrier).

2. The process for preparing diethyl oxalate by gas-phase CO coupling, regeneration and catalytic circulation according to claim 1, wherein the composition of the mixed raw material gas comprising purified raw material gas CO and ethyl nitrite from the regeneration tower is controlled to be (mol%) CO-25-35%, C₂H₅ONO-9～22％、NO-4～11％、CO₂-1 to 5% and the balance N₂。