CN111992209B - Catalyst for synthesizing dimethyl oxalate and preparation method and application thereof - Google Patents

Catalyst for synthesizing dimethyl oxalate and preparation method and application thereof Download PDF

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CN111992209B
CN111992209B CN202010907404.4A CN202010907404A CN111992209B CN 111992209 B CN111992209 B CN 111992209B CN 202010907404 A CN202010907404 A CN 202010907404A CN 111992209 B CN111992209 B CN 111992209B
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catalyst
dimethyl oxalate
methyl nitrite
mother liquor
salt solution
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汪达军
王光中
王辉
赵建恒
张伟良
谢忠伟
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Shandong Aside Technology Co ltd
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Abstract

The invention discloses a catalyst for synthesizing dimethyl oxalate and a preparation method and application thereof, belonging to the technical field of catalytic synthesis of dimethyl oxalate. The structural formula of the catalyst is Pd x Mg (0.7‑x) Al (0.2‑y) M y O, wherein M is selected from any one of Pr, Y and In, and x is more than or equal to 0.001 and less than or equal to 0.005,0.02 and less than or equal to Y is less than or equal to 0.05. The catalyst consists of Pd 2+ 、Mg 2+ 、Al 3+ 、M 3+ The mixed salt solution is prepared by coprecipitation with a precipitator. The catalyst is used for catalyzing carbon monoxide and methyl nitrite to synthesize dimethyl oxalate through gas phase coupling, the dispersion degree of Pd in the catalyst is high, the catalytic activity is ensured, the consumption of noble metal Pd is reduced, the catalyst cost is low, and the preparation is simple; and the conversion rate of methyl nitrite, the selectivity of dimethyl oxalate generation and the space-time yield of dimethyl oxalate are greatly improved when dimethyl oxalate is synthesized, and the catalyst stability is high.

Description

Catalyst for synthesizing dimethyl oxalate and preparation method and application thereof
Technical Field
The invention relates to a catalyst for synthesizing dimethyl oxalate and a preparation method and application thereof, belonging to the technical field of catalytic synthesis of dimethyl oxalate.
Background
Dimethyl oxalate ((COOCH) 3 ) 2 ) I.e., dimethyl oxalate, as a colorless monoclinic crystal having a melting point of 54 ℃ and a boiling point of 163.5 ℃, is soluble in alcohols and ethers and is decomposable in hot water. Dimethyl oxalate can be used for preparing oxalic acid by hydrolysis and can also be used for preparing glycol by hydrogenation, and the dimethyl oxalate serving as an important chemical intermediate has extremely important commercial development and application valueThe value is obtained. At present, two main synthesis processes of dimethyl oxalate are available, wherein the first process is obtained by esterifying oxalic acid and methanol in the presence of sulfuric acid, and the process has the defects of large wastewater discharge and serious environmental pollution; the second is formed by carbon monoxide (CO) and methyl nitrite (CH) 3 ONO) is prepared by gas-phase coupling reaction under the catalysis of noble metal, and the process specifically comprises two steps, wherein the first step is Nitric Oxide (NO) and methanol (CH) 3 OH) and oxygen (O) 2 ) Reaction to produce methyl nitrite (CH) 3 ONO), the second step of CO and CH 3 ONO is prepared through coupling reaction under the action of noble metal catalyst (COOCH) 3 ) 2 While generating NO; the main reaction equation is as follows:
(1)2NO+1/2O 2 +2CH 3 OH→2CH 3 ONO+H 2 o (no catalyst);
(2)2CO+2CH 3 ONO→(COOCH 3 ) 2 +2NO (noble metal catalyst);
(3)2CO+1/2O 2 +2CH 3 OH→(COOCH 3 ) 2 +H 2 o (total reaction formula).
The process for synthesizing the dimethyl oxalate is an environment-friendly green chemical production process with high atom economy, and draws more and more attention. In the process of synthesizing dimethyl oxalate by carbonylation and coupling of CO and methyl nitrite, the side reactions mainly occur as follows: reaction of CO with methyl nitrite to form NO and dimethyl Carbonate (CH) 3 O-COOCH 3 ) The methyl nitrite is decomposed to generate NO and methyl formate (HCOOCH) 3 ) And methanol, CO reacting with NO to form N 2 And CO 2 (ii) a The above side reaction equation is as follows:
(4)CO+2CH 3 ONO→CH 3 O-COOCH 3 +2NO；
(5)4CH 3 ONO→4NO+HCOOCH 3 +2CH 3 OH；
(6)2CO+2NO→N 2 +2CO 2 。
at present, pd/alpha-Al is generally adopted in the second process 2 O 3 Is a catalyst, but alpha-Al 2 O 3 Small specific surface area, easy to cause Pd dispersionLow, can not be fully and effectively utilized, and the content of noble metal Pd in the catalyst is higher by 0.5-2wt%, so that the cost of the catalyst is higher. In addition, under the action of the catalyst, the selectivity of the carbonylation coupling reaction to generate the dimethyl oxalate is about 90 percent, the side reaction to generate the dimethyl carbonate is obvious, and the selectivity is generally between 5 and 10 percent, so that more byproducts are generated.
In order to further improve the yield of the dimethyl oxalate and reduce the production cost, the key point is to develop a low-price high-performance dimethyl oxalate synthesis catalyst. Much research work has been done by many scholars in China. For example, (1) High-Performance and Long-live Pd Nanocatalyst Directed by Shape Effect for CO Oxidative Coupling to methyl oxide, ACS Catalysis,2013,3,118, prepared by immersion-liquid phase reduction method, pd/alpha-Al with Pd (111) surface preferentially exposed, small Pd particles and uniform distribution 2 O 3 The space-time yield of the catalyst, 0.5% of the catalyst prepared, although more than industrial 2% 2 O 3 The yield is higher than 40 percent, but can only reach 642g/Lcat/h, and the problem of lower space-time yield still exists. (2) Preparation and activity of eggshell type Pd/alpha-Al 2O3 catalyst, reported in catalytic science 2009,3,213, eggshell type Pd/alpha-Al is prepared by adjusting the pH value of Pd impregnation liquid 2 O 3 The catalyst can concentrate Pd mainly on the surface layer of the carrier to improve the activity of the catalyst, and the selectivity of the prepared catalyst with the loading of 0.07 percent Pd to generate dimethyl oxalate is as high as 2 percent 2 O 3 And about 90%, but the conversion of methyl nitrite is only 83%, which has a problem of low conversion of methyl nitrite. (3) The synthesis of oxalate and oxalic acid from carbon monoxide and nitrous acid ester, natural gas chemical industry (C1 chemical and chemical industry), 1995,4,5, discloses adding auxiliary agents of Ti, V, mn and Mg to catalyst Pd/alpha-Al 2 O 3 The performance influence shows that the result is better when Ti is used as an auxiliary agent, the selectivity of the generated dimethyl oxalate reaches 70 percent, the space-time yield is improved by 50 percent and reaches 1244g/Lcat/h, but the selectivity of the dimethyl oxalate in the technical scheme is still lower. (4) Development of catalyst for synthesizing dimethyl oxalate by CO gas-phase coupling and industrial catalysis in 2019,3,43In the form of Pd-C/alpha-Al 2 O 3 As catalyst, at 130 deg.C and 3000h space velocity -1 In the process, the content of dimethyl oxalate in the product can reach more than 90 percent, the space-time yield is 813g/Lcat/h, and the yield of dimethyl oxalate in the technical scheme is still lower. (5) Research on the performance of Ce modified dimethyl oxalate catalyst by calcination temperature in natural gas chemical industry (C1 chemistry and chemical industry), 2017,6,39 reports a series of Pd-Ce/alpha-Al calcined at different temperatures synthesized by immersion method 2 O 3 The catalyst is used for synthesizing dimethyl oxalate in the raw material gas of V (CO)/V (CH) 3 ONO) =20/10, and the space velocity is 3000h -1 And the reaction is carried out at the temperature of 120 ℃, the conversion rate of the methyl nitrite is 88.6 percent, the selectivity of the dimethyl oxalate is about 96.5 percent, the space-time yield is 1350g/Lcat/h at most, but the conversion rate of the methyl nitrite in the technical scheme is lower. Furthermore, the technical proposal is all expressed by alpha-Al 2 O 3 As a carrier, the catalyst has the defects of easy agglomeration of active components, poor stability and the like. (5) Catalyst Pd/gamma-Al disclosed in patent Process for preparing a catalyst of an organic acid in the organic phase US4229591A 2 O 3 、Pd/SiO 2 Or the reaction performance of Pd/active carbon in CO gas phase coupling synthesis of dimethyl oxalate, the highest space-time yield is 398g/Lcat/h, and the yield is lower. (6) Catalyst for synthesizing dimethyl oxalate by CO gas phase coupling and its preparation method, disclosed in CN105289589A, 0.05-0.3% 2 O 4 The catalytic performance in the reaction of synthesizing dimethyl oxalate by CO gas-phase coupling is that the selectivity of dimethyl oxalate reaches 98% at the airspeed of 2400/h, the space-time yield of dimethyl oxalate reaches 1125g/Lcat/h at most, but the preparation process of the catalyst has high energy consumption, low efficiency and unstable surface property.
In summary, in the presently disclosed technical solutions, some catalysts have high noble metal content and high price, some preparation methods are complicated, some methyl nitrite has low conversion rate, some dimethyl oxalate has low selectivity, some dimethyl oxalate has low space-time yield, and some have poor stability. The invention aims to provide a catalyst which is simple to prepare, low in price and excellent in reaction performance and is used for synthesizing dimethyl oxalate.
The above description is included in the technical knowledge of the inventors, and does not necessarily constitute a prior art.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a catalyst for synthesizing dimethyl oxalate as well as a preparation method and application thereof, so that the use amount of noble metal Pd is reduced while the catalytic activity is ensured, the cost of the catalyst is low, and the conversion rate of methyl nitrite, the selectivity of dimethyl oxalate generation and the space-time yield of dimethyl oxalate are greatly improved.
The invention adopts the following technical scheme to realize the purpose:
in one aspect, the invention provides a catalyst for preparing dimethyl oxalate, wherein the structural formula of the catalyst is Pd x Mg (0.7-x) Al (0.2-y) M y O, wherein M is selected from any one of Pr, Y and In, and x is more than or equal to 0.001 and less than or equal to 0.005,0.02 and less than or equal to Y is less than or equal to 0.05.
In preferred embodiments, x is taken from 0.002, 0.0025, or 0.003, and y is taken from 0.025, 0.03, or 0.035.
In another aspect, the invention also provides a preparation method of the catalyst for preparing dimethyl oxalate, and specifically, the catalyst comprises Pd 2+ 、Mg 2+ 、Al 3+ 、M 3+ The mixed salt solution is prepared by coprecipitation with a precipitator.
In a preferred embodiment, the mixed salt solution contains Pd 2+ 、Mg 2+ 、Al 3+ 、M 3+ The molar ratio of (1-5): (695-699): (150-180): 20-50).
In a preferred embodiment, the acid ion in the mixed salt solution is NO 3 - 、SO 4 - Or CH 3 COO - 。
In a preferred embodiment, the precipitating agent is Na 2 CO 3 Solutions, ammonia, sodium hydroxide solutions or ammonium carbonate solutions.
In a preferred embodiment, the preparation method of the catalyst for preparing dimethyl oxalate specifically comprises the following steps:
(1) Formulating Pd according to the composition of the catalyst 2+ 、Mg 2+ 、Al 3+ 、M 3+ Dripping the mixed salt solution and the precipitant into water simultaneously to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, and controlling the dripping speed of the mixed salt solution and the precipitant to maintain the pH of the precipitation mother liquor at 8-10;
(2) Aging the precipitation mother liquor in water bath at 50-80 deg.C for 8-15 hr;
(3) Filtering the aged precipitation mother liquor to obtain a solid, and washing and drying the solid to obtain a catalyst precursor;
(4) And roasting the catalyst precursor at the temperature of 600-700 ℃ for 3-6h to obtain the catalyst.
Wherein, the solid is washed by deionized water until the pH is = 7; when dried, the mixture was dried at 120 ℃.
In another aspect, the invention also provides an application of the catalyst for preparing dimethyl oxalate, in particular to a method for catalyzing carbon monoxide and methyl nitrite to synthesize dimethyl oxalate through gas phase coupling.
In a preferred embodiment, the specific synthesis conditions are: introducing carbon monoxide and methyl nitrite gas into the catalyst Pd x Mg (0.7-x) Al (0.2-y) M y In the O reactor, under the reaction conditions of the reaction pressure of 0.05-0.5MPa and the temperature of 100-180 ℃, carbon monoxide and methyl nitrite contact and react with a catalyst to prepare dimethyl oxalate.
In a preferred embodiment, the total volume space velocity of carbon monoxide and methyl nitrite is (1500-4000)/h, and the molar ratio of carbon monoxide to methyl nitrite is (1.1-3.0): 1.
Benefits of the present application include, but are not limited to:
in the catalyst for synthesizing dimethyl oxalate and the preparation method and application thereof, the dispersion degree of Pd in the catalyst is high, the use amount of noble metal Pd is reduced while the catalytic activity is ensured, the catalyst cost is low, and the preparation is simple; when the catalyst provided by the invention is used for catalyzing carbon monoxide and methyl nitrite to synthesize dimethyl oxalate through gas-phase coupling, the conversion rate of methyl nitrite, the selectivity of dimethyl oxalate generation and the space-time yield of dimethyl oxalate are greatly improved, the activity selectivity of the catalyst is not obviously reduced after continuous evaluation for 1000 hours, the stability is high, and the catalyst is suitable for industrial production.
Detailed Description
In order to more clearly explain the overall concept of the present application, the following detailed description will be given by way of specific examples. It should be noted, however, that the following detailed description merely gives specific operation examples of the present invention by way of example, and the scope of the present invention is not limited thereto. The scope of the invention is limited only by the claims. It will be obvious to those skilled in the art that various other modifications and substitutions can be made to the described embodiments of the invention within the scope of the invention as defined by the claims and still achieve the same technical result and achieve the final technical object of the invention.
In the present invention, room temperature means a normal ambient temperature in a laboratory, and varies depending on seasons and locations, and is usually 25 ℃. In the following examples, all the starting materials used were commercially available, unless otherwise specified.
1. Preparation of the catalyst
Example (1-1):
the structural formula of the catalyst is Pd 0.002 Mg 0.698 Al 0.17 Pr 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.11g of palladium nitrate, 24.65g of magnesium nitrate, 15.19g of aluminum nitrate and 3.11g of praseodymium nitrate, dissolving the materials in 100g of deionized water to prepare a mixed salt solution at room temperature, and weighing 35 g) of sodium carbonate to dissolve the materials in 300g of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into l50g of deionized water to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, wherein the stirring speed is 100r/min, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH of the precipitation mother liquor at 8-10; the salt solution and the precipitating agent are simultaneously dripped into water according to the proportion, so that the effect of a bottom material is achieved, the precipitation is conveniently carried out while stirring, multiple components are simultaneously precipitated, the pH is stable, and the system is uniform;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH is =7, and then drying the solid for 10 hours at 120 ℃ by using a forced air drying oven to obtain a catalyst precursor;
(5) Roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in the air, and then sieving by using a sieve with 10-14 meshes to obtain the catalyst; when the roasting temperature is lower, the interaction among the components of the catalyst is not strong; when the calcination temperature is higher, the specific surface area of the catalyst is low, and the exposed active sites are few. .
Example (1-2):
the structural formula of the catalyst is Pd 0.001 Mg 0.699 Al 0.17 Pr 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.05g of palladium nitrate, 24.73g of magnesium nitrate, 15.22g of aluminum nitrate and 3.11g of praseodymium nitrate, dissolving the materials in 100g of deionized water to prepare a mixed salt solution, weighing 35g of sodium carbonate, and dissolving the sodium carbonate in 300ml of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into 50g of deionized water to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, wherein the stirring speed is 100r/min, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH of the precipitation mother liquor at 8-10;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH value is =7, and drying for 10 hours at 120 ℃ by using a forced air drying oven to obtain a catalyst precursor;
(5) And roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in air, and then sieving by using a 10-14-mesh sieve to obtain the catalyst.
Examples (1 to 3):
the structural formula of the catalyst is Pd 0.003 Mg 0.697 Al 0.17 Pr 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.16g of palladium nitrate, 24.57g of magnesium nitrate, 15.16g of aluminum nitrate and 3.10g of praseodymium nitrate, dissolving the weighed materials in 150ml of deionized water to prepare a mixed salt solution, weighing 35g of sodium carbonate, and dissolving the weighed materials in 300g of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into 50g of deionized water to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, wherein the stirring speed is 100r/min, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH of the precipitation mother liquor at 8-10;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH is =7, and then drying the solid for 10 hours at 120 ℃ by using a forced air drying oven to obtain a catalyst precursor;
(5) Roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in air, and then sieving by using a 10-14-mesh sieve to obtain the catalyst.
Examples (1 to 4):
the structural formula of the catalyst is Pd 0.005 Mg 0.695 Al 0.17 Pr 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.27g of palladium nitrate, 24.40g of magnesium nitrate, 15.80g of aluminum nitrate and 3.09g of praseodymium nitrate, dissolving the weighed materials in 100g of deionized water to prepare a mixed salt solution, and weighing 35g of sodium carbonate, dissolving the weighed materials in 300g of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into 50g of deionized water to obtain a precipitation mother solution, continuously stirring the precipitation mother solution at 100r/min in the dripping process, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH value of the precipitation mother solution at 8-10;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH is =7, and then drying the solid for 10 hours at 120 ℃ by using a forced air drying oven to obtain a catalyst precursor;
(5) Roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in air, and then sieving by using a 10-14-mesh sieve to obtain the catalyst.
Examples (1 to 5):
the structural formula of the catalyst is Pd 0.003 Mg 0.697 Al 0.17 Y 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.17g of palladium nitrate, 25.51g of magnesium nitrate, 15.74g of aluminum nitrate and 2.84g of yttrium nitrate, dissolving in 100g of deionized water to prepare a mixed salt solution, weighing 35g of sodium carbonate, and dissolving in 300g of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into 50g of deionized water to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, wherein the stirring speed is 100r/min, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH of the precipitation mother liquor at 8-10;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH is =7, and then drying the solid for 10 hours at 120 ℃ by using a forced air drying oven to obtain a catalyst precursor;
(5) Roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in air, and then sieving by using a 10-14-mesh sieve to obtain the catalyst.
Examples (1 to 6):
the structural formula of the catalyst is Pd 0.003 Mg 0.697 Al 0.17 In 0.03 The specific preparation method comprises the following steps:
(1) Weighing 0.17g of palladium nitrate, 25.03g of magnesium nitrate, 15.44g of aluminum nitrate and 2.19g of indium nitrate, dissolving the materials in 100g of deionized water to prepare a mixed salt solution, weighing 35g of sodium carbonate, and dissolving the sodium carbonate in 300g of deionized water to prepare a sodium carbonate solution;
(2) Slowly dripping a mixed salt solution of palladium nitrate, magnesium nitrate, aluminum nitrate and praseodymium nitrate and a sodium carbonate solution into 50g of deionized water to obtain a precipitation mother liquor, continuously stirring the precipitation mother liquor in the dripping process, wherein the stirring speed is 100r/min, and controlling the dripping speed of the mixed salt solution and the sodium carbonate solution to maintain the pH of the precipitation mother liquor at 8-10;
(3) Aging the precipitation mother liquor in water bath at 70 ℃ for 12h;
(4) Filtering the aged precipitation mother liquor to obtain a solid, washing the solid with deionized water until the pH is =7, and drying the solid at 120 ℃ for 10 hours by using a forced air drying oven to obtain a catalyst precursor;
(5) And roasting the catalyst precursor for 4 hours at 600 ℃ by using a muffle furnace, cooling in the air, and then sieving by using a 10-14-mesh sieve to obtain the catalyst.
In the catalyst prepared In the above example, pd is an active component, and Pr, Y or In is an auxiliary agent, the catalyst can exert high catalytic activity of Pd, and can inhibit sintering of Pd through ionic interaction.
Hydrotalcite belongs to an anionic layered compound, (Mg) 6 Al 2 (OH) 16 CO 3 ·4H 2 O) is typically hydrotalcite, mg 2+ 、Al 3+ Substituted by other equivalent metal ions to form hydrotalcite-like compound with the chemical composition general formula [ M Ⅱ 1-x M Ⅲ x (OH) 2 ] x+ (CO 3 ) x/2 ·mH 2 O,M Ⅱ Is a divalent metal cation, M Ⅲ Is a trivalent metal cation, when x has a value between 0.2 and 0.33, i.e. M Ⅱ /M Ⅲ When the molar ratio is between 2 and 4, the hydrotalcite compound with complete structure can be obtained, and the catalyst provided by the invention controls M Ⅱ /M Ⅲ 3.5 to achieve hydrotalcite structure of the catalyst precursor. The hydrotalcite layered compound is calcined at high temperature and then converted into hydrotalcite-based composite oxide, and the catalyst provided by the invention is calcined at 600-700 ℃ to form hydrotalcite layered junctionsThe structure collapsed to form a spinel structure.
2. Use of catalysts
The catalyst provided by the invention is specifically applied to catalyzing carbon monoxide and methyl nitrite to synthesize dimethyl oxalate through gas phase coupling.
The activity of the catalyst is evaluated by carrying out the synthetic reaction of dimethyl oxalate in a fixed bed reaction tube, the reaction tube is a stainless steel tube, the catalyst is filled in the reaction tube, and reaction gas enters the reaction tube after being mixed. Sampling ports are arranged in front of and behind the reactor, so that the composition of the reaction raw material gas and the composition of the reaction tail gas can be respectively measured on line to determine the conversion rate of methyl nitrite, the mixed gas after reaction is collected after ice-cold condensation, and the collected condensation product is weighed.
The analysis of the experimental product was carried out by gas chromatography, one being a TCD detector for N analysis 2 One is FID detector for analyzing CH 3 ONO、(COOCH 3 ) 2 . Methyl nitrite conversion rate, dimethyl oxalate selectivity and dimethyl oxalate space-time yield are main indexes for evaluating the performance of the catalyst, and are defined as follows:
methyl Nitrite (MN) conversion:
Figure BDA0002661912620000101
dimethyl oxalate (DMO) selectivity:
Figure BDA0002661912620000102
space-time yield of dimethyl oxalate:
Figure BDA0002661912620000103
in the formula:
Figure BDA0002661912620000104
is an inlet N 2 Volume ofThe number of points is given to the user,
Figure BDA0002661912620000105
is an outlet N 2 The volume fraction of the mixture is,
Figure BDA0002661912620000106
in order to obtain a volume fraction of the imported MN,
Figure BDA0002661912620000107
in order to obtain the volume fraction of the egress MN,
Figure BDA0002661912620000108
for the volume fraction of DMO at the outlet, WHSV is the volume space velocity, vm is the molar volume of the gas (22.4L/mol), M DMO Is the molar mass of DMO (118 g/mol)
Example (2-1):
10ml of Pd were charged into a stainless-tube reactor having an inner diameter of 12mm 0.002 Mg 0.698 Al 0.17 Pr 0.03 O catalyst, after nitrogen purging, starting to introduce carbon monoxide and methyl nitrite raw gas while continuing to introduce nitrogen, wherein the nitrogen introduction amount accounts for 40 percent of the total volume of the gas, and the molar ratio n (CO)/n (CH) of the carbon monoxide and the methyl nitrite 3 ONO) =2, and the space velocity of the total gas volume is 3000h -1 The reaction temperature is 120 ℃, and the reaction pressure is 0.3 MPa.
As a result of the reaction, the conversion of methyl nitrite was 94.7%, the selectivity of dimethyl oxalate was 98.6%, and the space-time yield of dimethyl oxalate was 1476g/Lcat/h.
The catalyst is operated for a long period, and after 1000 hours, the conversion rate of methyl nitrite is 94.5-94.8%, the selectivity of dimethyl oxalate is 98.4-98.7%, and the space-time yield of dimethyl oxalate is 1470-1479g/Lcat/h, which indicates that the catalyst has good stability.
Example (2-2) -example (2-6):
example (2-2) -example (2-6) the results of the synthesis reaction were recorded as shown in Table 1, except that the kind of the catalyst was changed in addition to example (2-1) and the conditions of the synthesis reaction were not changed.
TABLE 1 results of the gas phase coupling of carbon monoxide and methyl nitrite in different catalysts for the synthesis of dimethyl oxalate
Figure BDA0002661912620000111
In examples (2-2) to (2-6), the catalysts were operated for a long period of time, and the catalyst had good stability as shown by 1000 hours, fluctuation in conversion of methyl nitrite. + -. 0.2%, fluctuation in selectivity of dimethyl oxalate. + -. 0.2%, and fluctuation in space-time yield of dimethyl oxalate. + -. 0.4%.
Examples (2-7) -examples (2-20):
example (2-7) -example (2-20) on the basis of example (2-1), pd was used 0.003 Mg 0.697 Al 0.17 Y 0.03 O is catalyst, reaction conditions (n (CO)/n (CH) are changed 3 ONO), temperature, pressure, space velocity), the reaction results are reported in table 2.
TABLE 2 influence of the reaction conditions on the results of the gas-phase coupling of carbon monoxide with methyl nitrite to dimethyl oxalate
Figure BDA0002661912620000112
Figure BDA0002661912620000121
In the examples (2-7) to (2-20), the catalyst was operated for a long period under different reaction conditions, and after 1000 hours, the conversion rate of methyl nitrite varied by ± 0.2%, the selectivity of dimethyl oxalate varied by ± 0.2%, and the space-time yield of dimethyl oxalate varied by ± 0.4%, indicating that the reaction conditions were reasonable and the catalyst had good stability.
Comparative example 1:
10ml of Mg were added to a stainless steel tubular reactor having an inner diameter of 12mm 0.7 Al 0.2 O hydrotalcite catalyst, after nitrogen purging, continuouslyIntroducing nitrogen, carbon monoxide and methyl nitrite, wherein the nitrogen is introduced in an amount accounting for 40 percent of the total gas volume, and the molar ratio of the carbon monoxide to the methyl nitrite is n (CO)/n (CH) 3 ONO) =2, and the space velocity is 3000h -1 The reaction temperature is 120 ℃, and the reaction pressure is 0.3 MPa.
As a result of the reaction, the conversion of methyl nitrite was 23.1%, the selectivity of dimethyl oxalate was 54.7%, and the space-time yield of dimethyl oxalate was 200g/Lcat/h.
Comparative example 2:
10ml of Pd was added to a stainless steel tubular reactor having an inner diameter of 12mm 0.002 Mg 0.698 Al 0.2 Continuously introducing nitrogen, carbon monoxide and methyl nitrite into the O-type hydrotalcite catalyst after nitrogen purging, wherein the introduction amount of the nitrogen accounts for 40 percent of the total gas volume, and the molar ratio of the carbon monoxide to the methyl nitrite n (CO)/n (CH) 3 ONO) =2, and the space velocity is 3000h -1 The reaction temperature is 120 ℃, and the reaction pressure is 0.3 MPa.
As a result of the reaction, the conversion of methyl nitrite was 93.3%, the selectivity of dimethyl oxalate was 97.2%, and the space-time yield of dimethyl oxalate was 1433g/Lcat/h.
Comparative example 3:
adding 10ml of 0.55% PdMg into a stainless steel tubular reactor with an inner diameter of 12mm 0.7 Al 0.2 O load type catalyst, after nitrogen purging, continuously introducing nitrogen, carbon monoxide and methyl nitrite, wherein the introduction amount of the nitrogen accounts for 40 percent of the total gas volume, and the molar ratio of the carbon monoxide to the methyl nitrite n (CO)/n (CH) 3 ONO) =2, and the space velocity is 3000h -1 The reaction temperature is 120 ℃, and the reaction pressure is 0.3 MPa.
As a result of the reaction, the conversion of methyl nitrite was 91.8%, the selectivity of dimethyl oxalate was 96.4%, and the space-time yield of dimethyl oxalate was 1399g/Lcat/h.
The above-described embodiments should not be construed as limiting the scope of the invention, and any alternative modifications or alterations to the embodiments of the present invention will be apparent to those skilled in the art.
The present invention is not described in detail, but is known to those skilled in the art.

Claims (10)

1. The catalyst for preparing dimethyl oxalate is characterized in that the structural formula of the catalyst is Pd x Mg (0.7-x) Al (0.2-y) M y O, wherein M is selected from any one of Pr, Y and In, and x is more than or equal to 0.001 and less than or equal to 0.005,0.02 and less than or equal to Y is less than or equal to 0.05.
2. The catalyst for the preparation of dimethyl oxalate according to claim 1, characterized in that x is taken from 0.002, 0.0025 or 0.003 and y is taken from 0.025, 0.03 or 0.035.
3. The method for preparing a catalyst for dimethyl oxalate according to claim 1, wherein the catalyst is prepared by using Pd 2+ 、Mg 2+ 、Al 3+ 、M 3+ The mixed salt solution is prepared by coprecipitation with a precipitator.
4. The method for preparing a catalyst for dimethyl oxalate according to claim 3, wherein Pd is in a mixed salt solution 2+ 、Mg 2+ 、Al 3+ 、M 3+ The molar ratio of (1-5): (695-699): (150-180): 20-50).
5. The method for preparing a catalyst for dimethyl oxalate according to claim 3, wherein the acid ion in the mixed salt solution is NO 3 - 、SO 4 - Or CH 3 COO - 。
6. The method of claim 3, wherein the precipitant is Na 2 CO 3 Solutions, ammonia, sodium hydroxide solutions or ammonium carbonate solutions.
7. The method for preparing a catalyst for dimethyl oxalate according to claim 1, comprising the steps of:
(1) Pd 2+ 、Mg 2+ 、Al 3+ 、M 3+ The mixed salt solution and the precipitating agent are simultaneously dripped into water to obtain a precipitation mother liquor, the precipitation mother liquor is continuously stirred in the dripping process, and the dripping speed of the mixed salt solution and the precipitating agent is controlled to maintain the pH value of the precipitation mother liquor at 8-10;
(2) Aging the precipitation mother liquor in water bath at 50-80 deg.C for 8-15 hr;
(3) Filtering the aged precipitation mother liquor to obtain a solid, and washing and drying the solid to obtain a catalyst precursor;
(4) And roasting the catalyst precursor at the temperature of 600-700 ℃ for 3-6h to obtain the catalyst.
8. Use of the catalyst for the preparation of dimethyl oxalate according to claim 1 or 2, characterized in that: the catalyst is used for catalyzing gas phase coupling of carbon monoxide and methyl nitrite to synthesize dimethyl oxalate.
9. The use according to claim 8, characterized in that the synthesis conditions are: introducing carbon monoxide and methyl nitrite gas into the catalyst Pd x Mg (0.7-x) Al (0.2-y) M y In the O reactor, under the reaction conditions of the reaction pressure of 0.05-0.5MPa and the temperature of 100-180 ℃, carbon monoxide and methyl nitrite contact and react with a catalyst to prepare dimethyl oxalate.
10. Use according to claim 9, characterized in that: the total volume space velocity of the carbon monoxide and the methyl nitrite is (1500-4000)/h, and the molar ratio of the carbon monoxide to the methyl nitrite is (1.1-3.0): 1.
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