CN107445829B - Method for preparing glyoxylic ester by oxidizing glycolate - Google Patents
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Abstract
The invention relates to a method for preparing glyoxylic acid ester by oxidizing glycolate, and mainly solves the problem of low yield of glyoxylic acid ester prepared by oxidizing glycolate in the prior art. The invention discloses a method for preparing glyoxylic ester by oxidizing glycolate, which comprises the steps of sequentially passing streams containing glycolate and oxygen-containing gas through n-stage reactors connected in series to obtain glyoxylic ester; wherein n is more than or equal to 2; t is1＝110～290℃，Tn+1‑TnThe technical scheme of 30-200 ℃ better solves the problem, and can be used for industrial production of glyoxylate through oxidative dehydrogenation of glycolate.
Description
Technical Field
The invention relates to a method for preparing glyoxylic acid ester by oxidizing glycolate.
Background
Glyoxylic acid esters are a chemical combination of aldehydes and esters that can undergo a variety of reactions, particularly hydrolysis, to produce glyoxylic acid. Glyoxylic acid is an organic intermediate for synthetic flavors, pharmaceuticals, foods, varnish raw materials, dyes, plastic additives and the like, and can be used for producing oral penicillin, vanillin, mandelic acid, allantoin and the like, so the consumption of glyoxylic acid is also increasing at home and abroad.
The glyoxylic acid production method is currently about more than ten kinds depending on the starting materials, and the most commonly used industrially are oxalic acid electrolytic reduction, glyoxal nitric acid oxidation, maleic acid (anhydride) ozonization, and the like. Two major problems are encountered in the glyoxylate industry at home today: firstly, the large-batch and high-quality glyoxylic acid is insufficient in supply, so that the price advantage of downstream products cannot be fully exerted, and the market development of the glyoxylic acid and the downstream products thereof is seriously influenced; secondly, the glyoxalic acid is produced by adopting a glyoxal method basically in China. The fluctuation of the international crude oil price influences the price of the glyoxal and finally influences the price of the glyoxylic acid.
China has abundant coal and natural gas resources, but insufficient petroleum resources, so that a method for opening up a non-petroleum route has important strategic significance in China. In the 70 th 20 th century, under the influence of the world petroleum crisis, a great deal of C1 chemical research mainly using natural gas and coal-based raw materials is carried out in various countries, and related technologies are rapidly developed in the 90 th century, so that a great breakthrough is made particularly in the aspect of researching the production of ethylene glycol by using coal or natural gas as raw materials, and a great deal of process by-product glycolate is generated, so that the development of a non-petroleum route for preparing methyl glyoxylate by oxidizing glycolate has very high competitiveness.
However, experimental research shows that the reaction for synthesizing glyoxylic ester through oxidation of glycolic ester has huge exotherms, and the danger of temperature runaway and the like can occur if the control is not proper. Moreover, the reaction for preparing glyoxylic acid ester by oxidizing the glycolic acid ester is the first-stage reaction in the whole oxidation reaction process, and if the reaction temperature is not well controlled, the bed temperature is overhigh due to huge heat release, and then the reaction is continuously carried out downwards to generate a large amount of acid; or yet further oxidation, large amounts of carbon dioxide and water are produced. Both reactions result in a reduced yield of glyoxylate. Therefore, in the production process of glyoxylic ester, how to control the temperature of the reaction bed layer is a very important link. However, the yield of glyoxylate is not high in the current domestic and foreign reports of the reaction. For example, U.S. Pat. No. 4,4340748 discloses a process for obtaining glyoxylic esters by vapor-phase catalytic oxidation of glycolic acid esters as a starting material with an oxygen-containing gas at 100 to 600 ℃, preferably 200 to 400 ℃, but the yield of glyoxylic esters is low, being 88.3% or less, and in some cases only 43.5% of glyoxylic esters.
Disclosure of Invention
The invention aims to solve the technical problem that the yield of the glycolic acid ester prepared by glycolic acid ester oxidation is low in the prior art, and provides a novel method for preparing the glycolic acid ester by glycolic acid ester oxidation. The method has the characteristic of high yield of glyoxylic ester.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for preparing glyoxylic ester by oxidizing glycolic ester comprises the steps of preparing glycolic ester and oxygen-containing glycolic esterSequentially passing the gas flow through n stages of reactors connected in series to obtain glyoxylic ester; wherein n is more than or equal to 2; t is1＝110～290℃，Tn+1-Tn＝30～200℃。
In the above technical solution, preferably, T is1＝160～260℃，Tn+1-Tn＝40～150℃。
In the above technical solution, preferably, n is 2 to 6; more preferably, n is 3 to 4.
In the above technical scheme, the outlet of each stage of reactor is provided with a heat exchanger H1……Hn(ii) a And the material flow containing the glycolate and the oxygen-containing gas enters each stage of heat exchanger to exchange heat with the material flow at the outlet of the stage of reactor, and then enters the first stage of reactor. Preferably, the streams containing glycolate and oxygen-containing gas enter the heat exchangers H of each stage in sequence1……HnWith the outlet stream W of the respective reactor stage1……WnAfter heat exchange, the reaction liquid enters a first-stage reactor.
In the above technical scheme, the outlet material flow W of the nth stage reactornAnd heat exchanger HnAfter heat exchange, the mixture enters a gas-liquid separator.
In the technical scheme, before the glycolate and the oxygen-containing gas enter the heat exchanger, the glycolate and the oxygen-containing gas are firstly gasified in a gasifier to obtain the material flow containing the glycolate and the oxygen-containing gas.
In the technical scheme, the oxygen-containing gas is preheated in a preheater before entering the gasifier.
In the technical scheme, the temperature of the preheater is 80-150 ℃.
In the technical scheme, the volume percentage of oxygen in the oxygen-containing gas is 0.5-40%.
In the technical scheme, the molar ratio of oxygen to glycolate in the oxygen-containing gas is (0.25-2): 1.
In the technical scheme, the residence time of the material flow containing the glycolate and the oxygen-containing gas in each stage of reactor is 0.5-10 seconds, and the pressure of each stage of reactor is 0-0.5 MPa.
In this specification, T1Is the first stage reactor temperature，TnIs the nth stage reactor temperature, Tn+1Is the n +1 stage reactor temperature. T is1The temperature of the first-stage reactor is 110-290 ℃. T isn+1-TnThe temperature of the n +1 th-stage reactor is 30-200 ℃, namely the temperature of the n +1 th-stage reactor is 30-200 ℃ higher than that of the nth-stage reactor. H1A heat exchanger after the first reactor stage HnIs a heat exchanger after the nth stage reactor. W1Is an outlet stream of the first stage reactor, WnIs the outlet stream of the nth stage reactor.
In the present invention, the reaction of the glycolic acid ester and oxygen-containing gas-containing stream in the reactor to form the glyoxylic acid ester is carried out in the presence of a catalyst. The catalyst comprises 1-90 parts by weight of at least one metal or oxide selected from iron, molybdenum, vanadium, silver or copper and 10-99 parts by weight of at least one carrier selected from alumina or silica.
The inventor researches and discovers that the reaction for synthesizing glyoxylic ester by oxidizing the glycolic acid ester is an exothermic reaction, the exothermic quantity is large, so measures must be taken to control the temperature in a reactor, otherwise, the dangers of temperature runaway and the like are easy to occur; moreover, excessive oxidation of the glyoxylic ester produced to acid or further oxidation of the glyoxylic ester to produce large amounts of carbon dioxide and water can affect the glyoxylic ester yield. Therefore, the invention adopts a multistage reactor and a multistage heat exchange process, the low-grade raw materials sequentially exchange heat with the gas stream at the outlet of the reactor and then enter the first reaction zone, so that a large amount of heat energy generated in the reaction process is removed in time, the temperature in the reactor is controlled, the glyoxylate is ensured not to be excessively oxidized, and the selectivity of the glyoxylate in the reaction process is improved. Meanwhile, oxygen in the reaction feed gas is partially consumed in the reaction process, so that the oxygen content in the reaction gas is reduced, and the conversion rate of the raw material glycolate is influenced. In a word, by adopting the technical scheme of the invention, the conversion rate of the glycolate is more than 97%, the selectivity of the glycolate can reach 96%, and a better technical effect is achieved.
Drawings
FIG. 1 is a schematic diagram of a process for preparing glyoxylic acid ester by oxidizing glycolate, which comprises a 2-stage reactor and a 2-stage heat exchanger.
FIG. 2 is a schematic diagram of a process for preparing glyoxylic acid ester by oxidizing glycolate, which comprises a 3-stage reactor and a 3-stage heat exchanger.
FIG. 3 is a schematic diagram of the process for preparing glyoxylic acid ester by oxidizing glycolate, which comprises a 4-stage reactor and a 4-stage heat exchanger.
In FIGS. 1 to 3, 1 is a preheater, 2 is a vaporizer, 3 is a first-stage reactor, and 4 is a first-stage heat exchanger H15 is a second-stage reactor, 6 is a second-stage heat exchanger H27 is a gas-liquid separating tank, 8 is a third-stage reactor, and 9 is a third-stage heat exchanger H310 is a fourth-stage reactor, 11 is a fourth-stage heat exchanger H4。
FIG. 1 is an embodiment comprising a 2-stage reactor and a 2-stage heat exchanger.
FIG. 2 is an embodiment comprising a 3-stage reactor and a 3-stage heat exchanger.
FIG. 3 is an embodiment comprising a 4-stage reactor and a 4-stage heat exchanger.
In FIG. 1, an oxygen-containing gas is preheated by a preheater 1. The preheated oxygen-containing gas is mixed with the glycolate and then enters the gasifier 2 to gasify the glycolate. The outlet of each stage of reactor is provided with a heat exchanger. The gasified material and gas W at the outlet of the first-stage reactor 31Exchanging heat in the first-stage heat exchanger 4, then entering the second-stage heat exchanger 6, and exchanging heat with the gas W at the outlet of the second-stage reactor 52And (4) heat exchange. The material after heat exchange firstly enters a first-stage reactor 3 to be in contact reaction with a catalyst, and then enters a second-stage reactor 5, namely, the reaction effluent of the former-stage reactor enters the next-stage reactor to be in contact reaction with the catalyst after heat exchange of the reaction effluent of the former-stage reactor in a heat exchanger. The reaction effluent from the second-stage reactor 5 is cooled by a second-stage heat exchanger 6, and then is separated by a gas-liquid separation tank 7 to obtain a liquid-phase product containing glyoxylate, and the gas phase enters the subsequent flow.
In FIG. 2, the oxygen-containing gas is preheated by preheater 1. Preheated oxygen-containing gas andthe alcohol acid ester is mixed and then enters a gasifier 2 to gasify the alcohol acid ester. The outlet of each stage of reactor is provided with a heat exchanger. The gasified material and gas W at the outlet of the first-stage reactor 31Exchanging heat in the first-stage heat exchanger 4, then entering the second-stage heat exchanger 6, and exchanging heat with the gas W at the outlet of the second-stage reactor 52Exchanging heat, finally entering a third-stage heat exchanger 9 and exchanging heat with gas W at the outlet of a third-stage reactor 83And (4) heat exchange. The material after heat exchange firstly enters a first-stage reactor 3 to be in contact reaction with a catalyst, then enters a second-stage reactor 5, and finally enters a third-stage reactor 8, namely the reaction effluent of the previous-stage reactor enters the next-stage reactor to be in contact reaction with the catalyst after heat exchange in a heat exchanger. The reaction effluent from the third-stage reactor 8 is cooled by a third-stage heat exchanger 9, and then is separated by a gas-liquid separation tank 7 to obtain a liquid-phase product containing glyoxylate, and the gas phase enters the subsequent flow.
In FIG. 3, the oxygen-containing gas is preheated by preheater 1. The preheated oxygen-containing gas is mixed with the glycolate and then enters the gasifier 2 to gasify the glycolate. The outlet of each stage of reactor is provided with a heat exchanger. The gasified material and gas W at the outlet of the first-stage reactor 31Exchanging heat in the first-stage heat exchanger 4, then entering the second-stage heat exchanger 6, and exchanging heat with the gas W at the outlet of the second-stage reactor 52Exchanges heat with the gas W at the outlet of the third-stage reactor 8 and then enters a third-stage heat exchanger 93Exchanging heat, and finally entering a fourth-stage heat exchanger 11 to exchange heat with the gas W at the outlet of the fourth-stage reactor 103And (4) heat exchange. The material after heat exchange firstly enters a first-stage reactor 3 to be in contact reaction with a catalyst, then enters a second-stage reactor 5, then enters a third-stage reactor 8, and finally enters a fourth-stage reactor 10, namely the reaction effluent of the previous-stage reactor enters a next-stage reactor to be in contact reaction with the catalyst after heat exchange in a heat exchanger. The reaction effluent from the fourth stage reactor 10 is cooled by a fourth stage heat exchanger 11, separated by a gas-liquid separation tank 7 to obtain a liquid phase product containing glyoxylate, and the gas phase enters the subsequent flow.
In the fig. 1-3, the temperature of the first reaction zone is 110-290 ℃, the temperature of the next reaction zone is 30-200 ℃ higher than that of the previous reaction zone, the reaction contact time is 0.5-10 seconds, and the pressure is 0-0.5 MPa.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Detailed Description
[ example 1 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 97%, and the selectivity of methyl glyoxylate was 96.4%.
[ example 2 ]
The flow shown in FIG. 1 was employed, wherein a mixed gas of oxygen and nitrogen containing 0.5% of oxygen and methyl glycolate were used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials was controlled to 0.25.
Wherein, the preheater 1 is preheated to 150 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 330 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.1%, and the selectivity of methyl glyoxylate was 95.1%.
[ example 3 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 40% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 80 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 230 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 96.1%, and the selectivity of methyl glyoxylate was 93.4%.
[ example 4 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 20% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 80 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 230 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 97.2%, and the selectivity of methyl glyoxylate was 94.1%.
[ example 5 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 10% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 1.
Wherein, the preheater 1 is preheated to 100 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.2%, and the selectivity of methyl glyoxylate was 95.1%.
[ example 6 ]
The flow shown in FIG. 1 was employed, in which a mixed gas of oxygen and nitrogen containing 1% of oxygen and methyl glycolate were used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials was controlled to 0.5.
Wherein, the preheater 1 is preheated to 130 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 280 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.3%, and the selectivity of methyl glyoxylate was 95.2%.
[ example 7 ]
The flow shown in FIG. 1 was employed, wherein a mixed gas of oxygen and nitrogen containing 50% of oxygen and methyl glycolate were used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials was controlled to 0.5.
Wherein, the preheater 1 is preheated to 80 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 96.3%, and the selectivity of methyl glyoxylate was 93.1%.
[ example 8 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 50 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 95.8%, and the selectivity of methyl glyoxylate was 95.9%.
[ example 9 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 110 ℃, the contact time of reaction gas and catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 250 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 95.7%, and the selectivity of methyl glyoxylate was 96.2%.
[ example 10 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 3 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 3 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.1%, and the selectivity of methyl glyoxylate was 95.4%.
[ example 11 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 160 ℃, the contact time of reaction gas and catalyst is 3 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 260 ℃, the contact time of the reaction gas and the catalyst is 3 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 97.5%, and the selectivity of methyl glyoxylate was 95.9%.
[ example 12 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 200 ℃, the contact time of the reaction gas and the catalyst is 1 second, and the pressure is 0.12 MPa; the second stage reactor condition is 280 ℃, the contact time of the reaction gas and the catalyst is 1 second, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.1%, and the selectivity of methyl glyoxylate was 94.5%.
[ example 13 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the condition of the first-stage reactor is 240 ℃, the contact time of reaction gas and a catalyst is 2 seconds, and the pressure is 0.5 MPa; the second stage reactor condition is 300 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.5 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.7%, and the selectivity of methyl glyoxylate was 93.5%.
[ example 14 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 260 ℃, the contact time of the reaction gas and the catalyst is 0.6 second, and the pressure is 0 MPa; the second stage reactor condition is 310 ℃, the contact time of the reaction gas and the catalyst is 0.6 second, and the pressure is 0 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.8%, and the selectivity of methyl glyoxylate was 93.2%.
[ example 15 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 290 ℃, the contact time of the reaction gas and the catalyst is 0.5 second, and the pressure is 0.2 MPa; the second stage reactor conditions were 320 ℃, the contact time of the reaction gas and the catalyst was 0.5 seconds, and the pressure was 0.2 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.4% and the selectivity of methyl glyoxylate was 92.5%.
[ example 16 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 10 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 220 ℃, the contact time of the reaction gas and the catalyst is 10 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 97.5%, and the selectivity of methyl glyoxylate was 96.3%.
[ example 17 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the condition of the second-stage reactor is 380 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 5% molybdenum oxide and the rest is alumina catalyst.
The reaction results showed that conversion of methyl glycolate was 97.4% and selectivity of methyl glyoxylate was 94.1%.
[ example 18 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor conditions are 180 ℃, the contact time of the reaction gas and the catalyst is 0.8 second, and the pressure is 0.12 MPa; the second stage reactor condition is 330 ℃, the contact time of the reaction gas and the catalyst is 1 second, and the pressure is 0.12 MPa; the catalyst is 10% copper oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 97.4%, and the selectivity of methyl glyoxylate was 95.9%.
[ example 19 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 3 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 260 ℃, the contact time of the reaction gas and the catalyst is 3 seconds, and the pressure is 0.12 MPa; the catalysts were all 10% silver/alumina catalysts.
The reaction result is: the conversion of methyl glycolate was 95.8%, and the selectivity of methyl glyoxylate was 97.4%.
[ example 20 ]
By adopting the flow shown in FIG. 1, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the first-stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 260 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalysts were all 6% vanadium/alumina catalysts.
The reaction result is: the conversion of methyl glycolate was 97.8%, and the selectivity of methyl glyoxylate was 96.1%.
[ example 21 ]
By adopting the flow shown in FIG. 2, the mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the contact time of the reaction gas and the catalyst in the first reactor, the second reactor and the third reactor is 1.5 seconds, the pressure is 0.12MPa, and the reaction temperature is 180 ℃, 230 ℃ and 280 ℃ respectively; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.5%, and the selectivity of methyl glyoxylate was 96.2%.
[ example 22 ]
By adopting the flow shown in FIG. 3, a mixed gas of oxygen and nitrogen containing 5% of oxygen and methyl glycolate are used as raw materials, and the molar ratio of oxygen to glycolate in the raw materials is controlled to be 0.5.
Wherein, the preheater 1 is preheated to 120 ℃; the contact time of the reaction gas and the catalyst in the first, second, third and fourth reactors is 1 second, the pressure is 0.12MPa, and the reaction temperature is 180 ℃, 220 ℃, 260 ℃ and 300 ℃ respectively; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 98.2%, and the selectivity of methyl glyoxylate was 96.5%.
[ COMPARATIVE EXAMPLE 1 ]
The methyl glycolate oxidation test was performed according to the method of [ example 1 ], but only one reactor was used. Namely, mixed gas of oxygen and nitrogen containing 5 percent of oxygen and methyl glycolate are used as raw materials, and the molar ratio of the oxygen to the glycolate in the raw materials is controlled to be 0.5. The mixed gas of oxygen and nitrogen is firstly sent into a preheater to be preheated to 120 ℃, and then is gasified with methyl glycolate in a gasifier. The gasified raw material and the gas at the outlet of the reactor exchange heat in a first-stage heat exchanger and then enter the reactor to contact with a catalyst for reaction, the reaction effluent is separated by a gas-liquid separation tank to obtain a liquid-phase product containing glyoxylate, and the gas-liquid two-phase analysis is respectively carried out. Wherein the reactor conditions are 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa.
The reaction result is: the conversion of methyl glycolate was 89%, and the selectivity of methyl glyoxylate was 87.2%.
[ COMPARATIVE EXAMPLE 2 ]
The methyl glycolate oxidation test was performed according to the method of [ example 1 ], but the feedstock and reaction effluent were not heat exchanged in the process flow. Namely, mixed gas of oxygen and nitrogen containing 5 percent of oxygen and methyl glycolate are used as raw materials, and the molar ratio of the oxygen to the glycolate in the raw materials is controlled to be 0.5. The mixed gas of oxygen and nitrogen is firstly fed into a preheater 1 to be preheated to 120 ℃, and then is gasified with methyl glycolate in a gasifier 2. The gasified raw materials enter a first-stage reactor to be in contact reaction with a catalyst, then enter a second-stage reactor to be in contact reaction with the catalyst, the reaction effluent is separated by a gas-liquid separation tank 7 to obtain a liquid-phase product containing glyoxylate, and the gas phase and the liquid phase are respectively analyzed.
Wherein, the first stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 240 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 94.4% and the selectivity of methyl glyoxylate was 84.4%.
[ COMPARATIVE EXAMPLE 3 ]
The methyl glycolate oxidation test was performed according to the method of [ example 1 ], but the reaction temperature of the second reactor was 250 ℃ higher than that of the first reactor. Namely, mixed gas of oxygen and nitrogen containing 5 percent of oxygen and methyl glycolate are used as raw materials, and the molar ratio of the oxygen to the glycolate in the raw materials is controlled to be 0.5. The mixed gas of oxygen and nitrogen is firstly fed into a preheater 1 to be preheated to 120 ℃, and then is gasified with methyl glycolate in a gasifier 2. The gasified raw materials enter a first-stage reactor to be in contact reaction with a catalyst, then enter a second-stage reactor to be in contact reaction with the catalyst, the reaction effluent is separated by a gas-liquid separation tank 7 to obtain a liquid-phase product containing glyoxylate, and the gas phase and the liquid phase are respectively analyzed.
Wherein, the first stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 430 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The reaction result is: the conversion of methyl glycolate was 99.5%, and the selectivity of methyl glyoxylate was 47.8%.
[ COMPARATIVE EXAMPLE 4 ]
The methyl glycolate oxidation test was performed according to the method of [ example 1 ], but the second stage reactor temperature was 20 ℃ higher than the first stage reactor temperature. Namely, mixed gas of oxygen and nitrogen containing 5 percent of oxygen and methyl glycolate are used as raw materials, and the molar ratio of the oxygen to the glycolate in the raw materials is controlled to be 0.5. The mixed gas of oxygen and nitrogen is firstly fed into a preheater 1 to be preheated to 120 ℃, and then is gasified with methyl glycolate in a gasifier 2. The gasified raw materials enter a first-stage reactor to be in contact reaction with a catalyst, then enter a second-stage reactor to be in contact reaction with the catalyst, the reaction effluent is separated by a gas-liquid separation tank 7 to obtain a liquid-phase product containing glyoxylate, and the gas phase and the liquid phase are respectively analyzed.
Wherein, the first stage reactor condition is 180 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the second stage reactor condition is 200 ℃, the contact time of the reaction gas and the catalyst is 2 seconds, and the pressure is 0.12 MPa; the catalyst is 50% ferric oxide and the rest is alumina catalyst.
The conversion of methyl glycolate was 80.4% and the selectivity of methyl glyoxylate was 95.4%.
Claims (11)
1. A method for preparing glyoxylic ester by oxidizing glycolate comprises the steps of sequentially passing streams containing glycolate and oxygen-containing gas through n-stage reactors connected in series to obtain glyoxylic ester; wherein n is more than or equal to 2; t is1= 110-290 ℃, the temperature of the next reaction zone is 30-200 ℃ higher than that of the previous reaction zone, and the outlet of each stage of reactor is provided with a heat exchanger H1……Hn(ii) a The material flow containing the glycolic acid ester and the oxygen-containing gas sequentially enters each stage of heat exchanger H1……HnWith the outlet stream W of the respective reactor stage1……WnAfter heat exchange, the reaction liquid firstly enters a first-stage reactor.
2. The method for preparing glyoxylic acid esters by oxidation of glycolic acid esters according to claim 1, wherein T is1=160～260℃。
3. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 1, wherein n = 2-6.
4. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 3, wherein n = 3-4.
5. The method for preparing glyoxylic acid esters by oxidation of glycolic acid esters according to claim 1, characterized in that the outlet stream W from the n-th stage reactor isnAnd heat exchanger HnAfter heat exchange, the mixture enters a gas-liquid separator.
6. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 1, wherein glycolic acid ester and oxygen-containing gas are gasified in a gasifier before entering the heat exchanger, thereby obtaining the stream containing glycolic acid ester and oxygen-containing gas.
7. The method for preparing glyoxylic acid esters by oxidation of glycolic acid esters according to claim 6, wherein the oxygen-containing gas is preheated in a preheater before entering the gasifier.
8. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 7, wherein the temperature of the preheater is 80-150 ℃.
9. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 1, wherein the oxygen-containing gas comprises 0.5 to 40 volume percent oxygen.
10. The method for preparing glyoxylic ester by oxidizing glycolic acid ester according to claim 1, wherein the molar ratio of oxygen to glycolic acid ester in the oxygen-containing gas is (0.25-2): 1.
11. The method for preparing glyoxylic acid ester by oxidizing glycolic acid ester according to claim 1, wherein the residence time of the glycolic acid ester-containing stream and the oxygen-containing gas in each stage of reactor is 0.5-10 seconds, and the pressure in each stage of reactor is 0-0.5 MPa.
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