WO2020082199A1

WO2020082199A1 - Catalyst for synthesizing oxalate by co coupling reaction, preparation and uses

Info

Publication number: WO2020082199A1
Application number: PCT/CN2018/111136
Authority: WO
Inventors: Libin YAN
Original assignee: Pujing Chemical Industry Co., Ltd
Priority date: 2018-10-22
Filing date: 2018-10-22
Publication date: 2020-04-30
Also published as: AU2023204635A1; AU2018446561A8; AU2018446561A1; RU2702116C1

Abstract

The invention relates to a catalyst for synthesizing an oxalate by a CO coupling reaction. The catalyst comprises an active component, an auxiliary agent and hollow microspheres of α-Al₂O₃ as a carrier. The auxiliary agent may comprise an auxiliary element selected from the group consisting of nickel, cobalt, manganese, zirconium, cerium, lanthanum, molybdenum, barium, vanadium, titanium, iron, yttrium, niobium, tungsten, tin and bismuth. Also provided is a process for making the catalyst and a method for using the catalyst in synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN).

Description

CATALYST FOR SYNTHESIZING OXALATE BY CO COUPLING REACTION, PREPARATION AND USES

FIELD OF THE INVENTION

The invention relates to a catalyst for synthesizing an oxalate by a CO coupling reaction and its preparation and uses.

BACKGROUND OF THE INVENTION

As an important chemical raw material, dimethyl oxalate can be used to prepare oxalic acid, ethylene glycol, etc. or as a pharmaceutical intermediate. As an important chemical raw material, ethylene glycol is mainly used in the production of polyethylene terephthalate (PET) . To produce ethylene glycol via the traditional production route, ethylene oxide is obtained from petroleum ethylene and then hydrogenated. This route belongs to the “oil route” . The advantage lies in the maturity of the technology, but the disadvantage is that the energy consumption is high and the cost of the product is seriously affected by the international crude oil prices.

Among the various processes for ethylene glycol synthesis reported so far, the process route for synthesizing oxalic acid diester from CO and then hydrogenating oxalic acid diester to make ethylene glycol has matured gradually. By the end of 2009, a 200,000-ton industrial demonstration unit was completed in the high-tech development zone in Tongliao City of the Inner Mongolia Autonomous Region and successfully produced qualified ethylene glycol products, proclaiming that the coal-based ethylene glycol technology has officially moved towards large-scale industrialization.

One of the key technologies for ethylene glycol production from coal-based syngas is the development of a catalyst for the reaction of CO with methyl nitrite to form dimethyl oxalate. Japanese Patent No. JP8242656 reports a process for the synthesis of dimethyl oxalate from CO and methyl nitrite using a catalyst loaded with a platinum group having a space-time yield at 432 g·L ^-1·h ^-1. U.S. Patent No. 4,507,494 reports a space-time yield of methyl ester at 429-462 g·L ^-1·h ^-1 and selectivity for dimethyl oxalate from CO up to 95%when a Pd Ti/Al ₂O ₃ catalyst was used. The existing CO carbonylation catalysts are generally catalysts loaded with Pd on α-Al ₂O ₃. In order to improve the space-time yield, auxiliary agents such as Zr (Chinese Patent No. CN 1066070C) , Ir (Chinese Patent Publication No. CN 101279257A) , and Ce (Chinese Patent No. CN 1141179C) have been studied in China.

In recent years, a large number of patents report catalysts comprising additives such as Mo, Ni, Ti, Fe, Ga, Cu, Zn, Na ₂O and SiO ₂ are added as auxiliary agents in catalysts, and used in the synthesis of an oxalate from CO and methyl nitrite.

In addition, researchers have conducted extensive research on the modification of α-Al ₂O ₃ and novel carriers.

Chinese Patent No. CN102649056B describes the use of palladium as an active component, ruthenium or osmium as an auxiliary agent, and alumina and silica as a composite carrier to prepare a catalyst with high selectivity and a high specific surface area, but poor space-time yield.

Chinese Patent Publication No. CN106607024A reports the use of palladium as an active component, zinc as an auxiliary agent, and a rare earth element modified alumina as a carrier to make a catalyst having a specific surface area of 3-40 m ²/g, a space-time yield of dimethyl oxalate at a level greater than 760 g·L ^-1·h ^-1, and stable operation for 3,000 h.

Chinese Patent Publication No. CN108187691A relates to a preparation method of a catalyst having a packed composite structure for CO gas phase coupling synthesis of an oxalate and an application thereof. The catalyst comprises an alumina skeleton, and a filled composite structure carrier composed of a filler filled inside the skeleton, and an active component Pd and auxiliary agents Fe and Cu supported on the surface of the carrier. The space-time yield was up to 1,000 g·L ^-1·h ^-1.

At present, most catalysts for synthesizing dimethyl oxalate use Pd as an active component, and Mo, Ni, Ti, Fe, Ga, Cu, Zn or the like as an auxiliary agent, α-alumina or modified alumina as a composite carrier. The overall space-time yield is low, the surface area is small, and the impurity content of the raw material is high. A special dehydrogenation equipment is often required in an industrial system to achieve the purpose of purifying the raw material gas. The industrial system contains NO gas in the circulation system, and the presence of NO gas tends to cause the MN conversion rate to decrease.

There remains a new for an effective catalyst for synthesizing an oxalate by a CO coupling reaction.

SUMMARY OF THE INVENTION

The present invention provides a catalyst and its preparation and uses.

A catalyst for synthesizing an oxalate by a CO coupling reaction is provided. The catalyst comprises (a) an active component comprising palladium (Pd) or an oxide thereof; (b) an auxiliary agent comprising an auxiliary element selected from the group consisting of nickel, cobalt, manganese, zirconium, cerium, lanthanum, molybdenum, barium, vanadium, titanium, iron, yttrium, niobium, tungsten, tin and bismuth; and (c) a carrier consisting of hollow microspheres of α-Al ₂O ₃. The catalyst may have a specific surface area of 1-200 m ²/g. The catalyst may consist of the active component at a content of 0.005-1.000 wt%, the auxiliary agent at a content of 0.01-5.00 wt%, and the carrier. The auxiliary element may be selected from the group consisting of manganese, zirconium, cerium, lanthanum, vanadium, titanium, yttrium, niobium, tin and bismuth.

For each catalyst of the present invention, a process for preparing the catalyst is provided. The process comprises (a) dehydrating a carbohydrate solution to make a carbohydrate solid sample, wherein the carbohydrate solution comprises a carbohydrate having a carbonyl group, a hydroxyl group or a combination thereof; (b) drying the carbohydrate solid sample to make a structural precursor; (c) adding the structural precursor to an aluminum nitrate solution to make an aluminum sample; (d) dehydrating the aluminum sample to make an aluminum solid sample; (e) drying the aluminum solid to make a dried aluminum solid sample; (f) calcining dried aluminum solid sample to make a carrier consisting of hollow microspheres of α-Al ₂O ₃; (g) impregnating the carrier with an impregnation solution comprising the active component and the auxiliary agent to make a mixture; (h) drying the mixture to make a dried mixture; and (i) calcining the dried mixture.

The carbohydrate may be selected from the group consisting of glucose, fructose, sucrose and maltose. The process may further comprise washing the carbohydrate solid sample with deionized water and ethanol repeatedly before step (b) .

The structural precursor may be added to the aluminum nitrate solution at a structural precursor/aluminum nitrate mass ratio of 1: (5-50) .

The process may further comprise subjecting the aluminum sample to ultrasound treatment and letting it sit for 8-20 h in step (c) .

The process further comprises dissolving a salt of the auxiliary element and a Pd salt in deionized water to make an active component/auxiliary agent solution, and adjusting pH of the active component/auxiliary agent solution to 1-5 with diluted nitric acid, diluted hydrochloric acid, oxalic acid or citric acid to make the impregnation solution, and spraying the impregnation solution to the carrier at a volume equal to the that of the carrier. The Pd salt may be selected from the group consisting of a halide, a nitrate, an acetate and an acetylacetonate. The salt of the auxiliary element may be selected from the group consisting of a chloride, a nitrate, an acetate, an oxalate and an ammonium salt.

For each catalyst of this invention, a method for reducing a catalyst for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) is provided. The reduction method comprises exposing the catalyst to a reducing gas at 130-220 ℃ and under an atmospheric pressure for 3-8 h. The reducing gas is mixture of hydrogen (H ₂) and nitrogen (N ₂) , and has a molar H ₂ content of 5-30 %and a flow rate at 40-80 ml/min·g of the catalyst.

For each catalyst of this invention, a method for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) is also provided. The synthesis method comprise exposing a feed gas to the catalyst of the present invention at a temperature of 100-160 ℃ and a pressure of 0.1-0.5 MPa. The feed gas is a mixture of methyl nitrite (MN) , monoxide (CO) and nitrogen (N ₂) , and has a CO/MN molar ratio of (1-3) : 1 and a volume space velocity, also known as gas hourly space velocity (GHSV) , at 3,000-10,000 h ^-1, whereby an oxalate is synthesized.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a catalyst for synthesizing an oxalate by a CO coupling reaction and its preparation and uses. The catalyst comprises an active component, an auxiliary agent and a carrier. The present invention solves the technical problems of high raw material requirement, low space-time yield and poor stability associated with the existing technologies by providing a catalyst for synthesizing an oxalate by a CO coupling reaction. The inventors have surprisingly discovered that a-Al ₂O ₃ hollow microspheres having large specific surface area can be used a carrier in the catalyst providing good metal dispersibility, low precious metal loading, high activity and selectivity in the reaction of CO and MN to synthesize dimethyl oxalate, strong resistance to hydrogen in raw material gas, high MN conversion rate in response to high NO content in the feed gas, and strong catalyst stability. Also provided is a process for preparing the catalyst as well as an application of the catalyst in a CO coupling reaction to synthesize an oxalate such as dimethyl oxalate.

A catalyst for synthesizing an oxalate by a CO coupling reaction is provided. The catalyst comprises an active component, an auxiliary agent and a carrier. The oxalate may be dimethyl oxalate, diethyl oxalate, or a combination thereof.

The term “active component” used herein refers to a substance in the catalyst that catalyzes one or more reactants to synthesize a target product. The active component may comprise palladium (Pd) or an oxide thereof. The active component may account for about 0.005-1.000 wt%, preferably 0.06-0.95 wt%, more preferably 0.2-0.6 wt%, of the catalyst. A Pd salt may be used to provide the active component in the catalyst. The Pd salt may be selected from the group consisting of a halide, a nitrate, an acetate and an acetylacetonate, preferably a halide, an acetate and a nitrate, more preferably a halide and a nitrate.

The term “auxiliary agent” used herein refers to a substance in the catalyst that promotes the interaction between an active component and a carrier in a catalyst. The auxiliary agent may comprise an element selected from the group consisting of nickel, cobalt, manganese, zirconium, cerium, lanthanum, molybdenum, barium, vanadium, titanium, iron, yttrium, niobium, tungsten, tin and bismuth, preferably an element selected from the group consisting of manganese, zirconium, cerium, lanthanum, vanadium, titanium, yttrium, niobium, tin and bismuth, more preferably an element selected from the group consisting of Cerium, lanthanum, yttrium, niobium, tin and bismuth. The auxiliary agent may account for about 0.01-5.00 wt%, preferably 0.1-4.0 wt%, more preferably 0.15-2.00 wt%, of the catalyst. A salt of an auxiliary element may be used to provide the auxiliary agent in the catalyst. The salt of the auxiliary element may be selected from the group consisting of a chloride, a nitrate, an acetate, an oxalate and an ammonium salt, preferably a chloride, a nitrate and an acetate; more preferably a chloride and a nitrate.

The term “carrier” used herein refers to a substance in the catalyst that provides support for an active component and an auxiliary agent. Depending on its structure, the carrier may change the distribution of the active component on the carrier such that the catalytic activity of the active component may be modified. The carrier consists of hollow microspheres of aluminum oxide (e.g., α-Al ₂O ₃) . The hollow aluminum oxide microspheres may be formed by aluminum oxide via covalent bonds. A microsphere comprises a shell that encompasses a hollow structure. The hollow structure may be about 1-90 v%, preferably 3-85 v%, more preferably 5-75 v%, of the total volume of the microsphere.

The term “specific surface area” used herein refers to a property of a solid defined as the total surface area of a material per unit of mass. The carrier in the catalyst of the present invention may have a specific surface area of 1-200 m ²/g, preferably 7-180 m ²/g, more preferably 10-150 m ²/g.

For each catalyst of the present invention, a process for preparing the catalyst is provided. The preparation process comprises preparing a carrier consisting of hollow microspheres of α-Al ₂O ₃, and preparing a catalyst from the carrier, an activity component and an auxiliary agent.

The carrier may be prepared by a preparation process. The carrier preparation process comprises dehydrating a carbohydrate solution, for example, at 150-180 ℃ for 6-12 h, to make a carbohydrate solid sample; drying the carbohydrate solid sample, for example, at 40-80 ℃ for 5-24 h, to make a structural precursor; adding the structural precursor to an aluminum nitrate solution to make an aluminum sample; dehydrating the aluminum sample, for example, at 6-80 ℃ for 10-20 h to make an aluminum solid sample; drying the aluminum solid, for example, at 6-80 ℃ for 10-20 h to make a dried aluminum solid sample; calcining dried aluminum solid sample, for example, at least 300-500 ℃ for 2-5 h under nitrogen gas and then at 1,000-1,200 ℃ for 1-6 h, to make a carrier consisting of hollow microspheres of α-Al ₂O ₃.

The carbohydrate solution may comprise a carbohydrate, which has a carbonyl group, a hydroxyl group or a combination thereof. The carbohydrate may be selected from the group consisting of glucose, fructose, sucrose and maltose, preferably glucose and sucrose, more preferably glucose.

The carrier preparation process may further comprise washing the carbohydrate solid sample with deionized water and ethanol repeatedly before drying. The carrier preparation process may further comprise subjecting the aluminum sample to ultrasound treatment and then letting it sit for 8-20 h before dehydration of the aluminum sample.

The catalyst may be prepared by a catalyst preparation process. The catalyst preparation process comprises impregnating the carrier with an impregnation solution comprising the active component and the auxiliary agent to make a mixture; drying the mixture, for example, at 65-130 ℃ for 5-10 h, to make a dried mixture; and calcining the dried mixture, for example, at 300-500 ℃ for 2-8 h, whereby the catalyst is prepared. The structural precursor may be added to the aluminum nitrate solution at a structural precursor/aluminum nitrate mass ratio of 1: (5-50) , preferably 1: (10-40) , more preferably 1: (15-30) .

The catalyst preparation process may further comprise dissolving a salt of the auxiliary element and a Pd salt in deionized water to make an active component/auxiliary agent solution, and adjusting pH of the active component/auxiliary agent solution to 1-5 with diluted nitric acid, diluted hydrochloric acid, oxalic acid or citric acid to make the impregnation solution, and spraying the impregnation solution to the carrier at a volume equal to the that of the carrier.

For each catalyst of the present invention, the catalyst is reduced before used for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) . The method comprises exposing the catalyst of the present invention to a reducing gas under reducing conditions, for example, at 130-220 ℃ and under an atmospheric pressure for 3-8 h. The reducing gas may be mixture of hydrogen (H ₂) and nitrogen (N ₂) , and have a molar H ₂ content of 5-30 %and a flow rate at 40-80 ml·min ^-1·g ^-1 of the catalyst. As a result, the catalyst is reduced.

For each catalyst of the invention, a method for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) is provided. The synthesis comprising exposing a feed gas to the catalyst of claim 1. The terms “feed gas” and “raw material gas” are used herein interchangeably, and refer to a gas that is introduced into a chemical process. The reaction temperature may be 100-160 ℃, preferably 115-130 ℃. The reaction pressure may be 0.1-0.5 MPa, preferably 0.2-0.4 MPa. The feed gas may be a mixture of methyl nitrite (MN) , monoxide (CO) and nitrogen (N ₂) . The feed gas may have a CO/MN molar ratio from 1: 1 to 3: 1, preferably 1.3-2.5. The feed gas or raw material gas may comprise hydrogen (H ₂) . The H ₂ content may be up to 500, 750, 1,000, 1,500 or 2,000 ppm. The gas hourly space velocity (GHSV) [ “Gas hourly space velocity (GHSV) ” is the same as “volume space velocity” ] of the feed gas may be at 3,000-10,000 h ^-1, 3,200-8,300 h ^-1 or 4,000-6,000 h ^-1. As a result, an oxalate is synthesized.

The carrier used in the present invention consists of α-Al ₂O ₃ hollow microspheres. The carrier has a large specific surface area enabling uniform distribution of the active metal and the auxiliary metal on the surface of the microspheres and effectively reducing the precious metal loading and improving the activity and stability of the catalyst.

The organic combination of the active metal, the auxiliary agent and the carrier may make the catalyst resistant to hydrogen in the raw material gas without a special dehydrogenation device. This is beneficial to reducing the investment in such a device and the purification cost of the raw material gas.

In the reaction of CO and methyl nitrite (MN) to synthesize dimethyl oxalate, the catalyst of the invention provides a high MN conversion rate, a high selectivity for dimethyl oxalate, strong stability and high yield of dimethyl oxalate.

The term “conversion rate” used herein refers to the percentage of methyl nitrite (MN) that is converted to a product. The average MN conversion rate of the catalyst according to the present invention may be at least about 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%or 100%, preferably 96-98%, for a period of time, for example, for at least 500, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000 or 10,000 hours, preferably for at least 6,000 h. The average MN conversion rate may be at least about 1%, 2%, 3%, 4%or 5%higher for period of time, for example, at least about 500, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000 or 10,000 hours using the catalyst of the present invention as compared with that using a catalyst without α-Al ₂O ₃ hollow microspheres.

The term “selectivity” used herein refers to the percentage of methyl nitrite (MN) converted to a target product in all of the converted methyl nitrite (MN) . The selectivity of the catalyst for dimethyl oxalate according to the present invention may be at least about 95.0%, 96.0%, 97.0%, 98.0%, 99.0%, 99.5%, 99.9%or 100%, preferably 97.0-98.8%for period of time, for example, for at least 500, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000 or 10,000 hours, preferably for at least 6,000 h. The selectivity rate of the catalyst for dimethyl oxalate may be at least about 1%, 2%, 3%, 4%or 5%higher for period of time, for example, for at least 500, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000 or 10,000 hours, using the catalyst of the present invention as compared with that using a catalyst without the α-Al ₂O ₃ hollow microspheres.

The term “space-time yield of dimethyl oxalate” used herein refers to the production amount of dimethyl oxalate per unit volume (or mass) of a catalyst per unit time. The space-time yield of dimethyl oxalate synthesized according to the present invention may be at least about 500, 1,000 or 2000 g·L ^-1·h ^-1. The space-time yield of dimethyl oxalate may be at least about 800, 1200 or 1600 g·L ^-1·h ^-1 higher for period of time, for example, for at least 500, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000 or 10,000 hours, preferably for at least 6,000 h, using the catalyst of the present invention as compared with that using a catalyst without the α-Al ₂O ₃ hollow microspheres.

In one embodiment, the hydrogen content of the raw material gas was 1,000 ppm and the NO content was 12%. The reaction temperature was 115-128 ℃. The reaction pressure was 0.3 MPa. The Gas Hourly Space Velocity (GHSV) ) may be 4,000 ^-1. When the GHSV was raised to 6,000 h ^-1, the catalyst activity did not decrease after 6,000 h of stable operation. The average conversion rate of MN was 96-98%.

The term “about” as used herein when referring to a measurable value such as an amount, a percentage, and the like, is meant to encompass variations of ±20%or ±10%, more preferably ±5%, even more preferably ±1%, and still more preferably ±0.1%from the specified value, as such variations are appropriate.

Example 1. Catalyst 1

Catalyst 1 was prepared. Glucose was used as a precursor to make a 1.2 mol/L glucose solution. 2 L of the glucose solution was maintained at 170 ℃ for 10 h. The resulting liquid was dehydrated, washed repeatedly with deionized water and ethanol. The resulting solid was dried at 50 ℃ for 20 h to obtain a structural precursor.

0.5 mol/L aluminum nitrate solution was prepared with ethanol as a solvent. 10.8 g of the structural precursor was added into 2L of the aluminum nitrate solution, sonicated at 25 ℃ for 50 min, then allowed to stand for 10 h. The resulting liquid was dehydrated. The resulting solid was dried at 70 ℃ for 15 h, and calcined at 380 ℃ for 3.5 h under a nitrogen atmosphere, followed by calcination at 1150 ℃ for 3 h in an air atmosphere to obtain α-Al ₂O ₃ hollow microspheres as a carrier.

Pd nitrate and Bi nitrate in amounts equivalent to those at 0.25 wt%and 0.60 wt%of the catalyst, respectively, and 30g of the carrier were dissolved in deionized water and then diluted nitric acid was used to adjust the pH of the resulting solution to 2.3. The resulting liquid is sprayed onto the carrier at 30 ℃ in equal volume. Then, the resulting sample was dried at 110 ℃ for 9 h, and then calcined in air at 310 ℃ for 4 h to obtain a Pd-Bi/α-Al2O ₃ catalyst.

The composition of the active component in the catalyst was measured by ICP, and the specific surface area of the catalyst was measured by a physicochemical adsorption meter.

Before the evaluation of the catalyst, the catalyst was loaded in a constant temperature zone in a

mm stainless steel fixed bed reactor with a catalyst loading of 8.7 mL. At a reduction temperature of 200℃ under normal pressure, a mixture of hydrogen and nitrogen was used, wherein the molar content of hydrogen was 15 %, the flow rate was 80 ml·min ^-1·g ^-1 catalyst, the reduction time was 8 h, then it was purged with nitrogen and cooled to 120 ℃.

The reaction was started after the exhaust gas does not contain hydrogen. The reaction took place in raw material gas, which was a mixed gas of MN, CO and N ₂. The CO/MN molar ratio was 1.8: 1. The reaction temperature was 120 ℃. The reaction pressure was 0.3 MPa. The Gas Hourly Space Velocity (GHSV) was 6400 h ^-1.

Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 2. Catalyst 2

Catalyst 2 was prepared according the method described in Example 1 except that glucose was changed to maltose and Bi nitrate was changed to Co nitrate, and was evaluated according to the method described in Example 1 except that the reaction pressure was 0.27 MPa and the GHSV was 4300 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 3. Catalyst 3

Catalyst 3 was prepared according the method described in Example 1 except that glucose was changed to fructose and Bi nitrate was changed to Ti nitrate, and was evaluated according to the method described in Example 1 except that the CO/MN molar ratio was 1.25: 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 4. Catalyst 4

Catalyst 4 was prepared according the method described in Example 1 except that glucose was changed to sucrose and Bi nitrate was changed to Y nitrate, and was evaluated according to the method described in Example 1 except that the reaction temperature was 128 ℃. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 5. Catalyst 5

Catalyst 5 was prepared according the method described in Example 1 except that glucose was changed to fructose and Bi nitrate was changed to Ni nitrate, and was evaluated according to the method described in Example 1 except that the reaction temperature was 103 ℃ and the GHSV was 8100 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst. Example 6. Catalyst 6

Catalyst 6 was prepared according the method described in Example 1 except that glucose was changed to maltose and Bi nitrate was changed to Mn nitrate, and was evaluated according to the method described in Example 1 except that the reaction pressure was 0.15 MPa and the GHSV was 3300 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 7. Catalyst 7

Catalyst 7 was prepared according the method described in Example 1 except that glucose was changed to sucrose and Bi nitrate was changed to Zr nitrate, and was evaluated according to the method described in Example 1 except that the reaction pressure was 0.35 MPa and the GHSV was 9700 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 8. Catalyst 8

Catalyst 8 was prepared according the method described in Example 1 except that Bi nitrate was changed to Ce nitrate, and was evaluated according to the method described in Example 1 except that the CO/MN molar ratio was 1.75: 1 and the reaction temperature was 121 ℃. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 9. Catalyst 9

Catalyst 9 was prepared according the method described in Example 1 except that Bi nitrate was changed to La nitrate, and was evaluated according to the method described in Example 1 except that the CO/MN molar ratio was 1.75: 1 and the GHSV was 6900 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 10. Catalyst 10

Catalyst 10 was prepared according the method described in Example 1 except that Bi nitrate was changed to Mo ammonium salt, and was evaluated according to the method described in Example 1 except that the reaction pressure was 0.25 MPa and the GHSV was 5700 h ^-1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 11. Catalyst 11

Catalyst 11 was prepared according the method described in Example 1 except that Bi nitrate was changed to Ba nitrate, and was evaluated according to the method described in Example 1 except that the reduction temperature was 175 ℃. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 12. Catalyst 12

Catalyst 12 was prepared according the method described in Example 1 except that Bi nitrate was changed to V nitrate, and was evaluated according to the method described in Example 1 except that the reduction time was 5 h. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 13. Catalyst 13

Catalyst 13 was prepared according the method described in Example 1 except that Bi nitrate was changed to Fe nitrate and the dried solid was calcined at 420 ℃ for 2.8 h in a nitrogen atmosphere, and then calcined at 1080 ℃ for 3.5 h in an air atmosphere, and was evaluated according to the method described in Example 1 except that the GHSV was 8400 h ^-1, the reaction pressure was 0.2 MPa, and the reaction temperature was 110 ℃. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 14. Catalyst 14

Catalyst 14 was prepared according the method described in Example 1 except that Bi nitrate was changed to Nb oxalate and the dilute nitric acid in the preparation of the catalyst was changed to citric acid, and was evaluated according to the method described in Example 1 except that the GHSV was 5500 h ^-1, the reaction pressure was 0.3 MPa, the reaction temperature was 148 ℃, and the CO/MN molar ratio was 1.6: 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 15. Catalyst 15

Catalyst 15 was prepared according the method described in Example 1 except that Bi nitrate was changed to W ammonium salt, and was evaluated according to the method described in Example 1 except that the GHSV was 4700 h ^-1, the reaction pressure was 0.5 MPa, the reaction temperature was 160 ℃, and the CO/methyl nitrite molar ratio was 2.5: 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 16. Catalyst 16

Catalyst 16 was prepared according the method described in Example 1 except that Bi nitrate was changed to Sn chloride, and was evaluated according to the method described in Example 1 except that the GHSV was 7700 h ^-1, the reaction pressure was 0.18 MPa, the reaction temperature was 130 ℃, and the CO/methyl nitrite molar ratio was 1.3: 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 17. Catalyst 17

Catalyst 17 was prepared according the method described in Example 1 except that Bi nitrate was changed to La nitrate and Fe acetate, and was evaluated according to the method described in Example 1 except that the GHSV was 8300 h ^-1, the reaction pressure was 0.4 MPa, the reaction temperature was 115 ℃, and the CO/methyl nitrite molar ratio was 3: 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 18. Catalyst 18

Catalyst 18 was prepared according the method described in Example 1 except that Bi nitrate was changed to Ce nitrate.

mm stainless steel fixed bed reactor with a catalyst loading of 8.7 mL. At a reduction temperature of 200℃ under normal pressure, a mixture of hydrogen and nitrogen was used, wherein the molar content of hydrogen was 15 %, the flow rate was 80 ml·min ^-1·g ^-1 catalyst, the reduction time was 8 h, then it was purged with nitrogen and cooled to a reaction temperature.

The reaction was started after the exhaust gas does not contain hydrogen. The reaction took place in a mixture of MN, CO, N ₂ and H ₂ having a CO/MN molar ratio of 1.8: 1. The H2 content was 1,000 ppm. The NO content was 12%. The reaction temperature was 115-128 ℃, a reaction pressure was 0.3 MPa, and the GHSV was 4,000-6,000 h ^-1. Stable operation lasted for 6,000 h as the activity of the catalyst did not decrease. The average MN was 96-98%. The average space-time yield of dimethyl oxalate was as high as 1,400 g per liter of the catalyst (L) per hour (h) .

Example 19. Comparative catalyst 1

Comparative catalyst 1 was prepared according the method described in Example 1 except that the carrier was selected from conventional alpha alumina, and was evaluated according to the method described in Example 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst. Example 20. Comparative catalyst 2

Comparative catalyst 2 is identical to comparative catalyst 1 and was evaluated according to the method described in Example 1 except that the mixed gas further contained H ₂ at 1,000 ppm. Table 2 shows the catalyst activity of the catalyst.

Example 21. Comparative catalyst 3

Comparative catalyst 3 is identical to comparative catalyst 1 and was evaluated according to the method described in Example 20 except that the mixed gas further contained NO at 10%. Table 2 shows the catalyst activity of the catalyst.

Example 22. Comparative catalyst 4

Comparative catalyst 4 was prepared according the method described in Example 1 except that Bi nitrate was omitted, and was evaluated according to the method described in Example 1. Table 1 shows the composition and the specific surface area of the catalyst. Table 2 shows the catalyst activity of the catalyst.

Example 23. Comparative catalyst 5

Comparative catalyst 5 is identical to comparative catalyst 4 and was evaluated according to the method described in Example 20. Table 2 shows the catalyst activity of the catalyst.

Example 24. Comparative catalyst 6

Comparative catalyst 6 is identical to comparative catalyst 4 and was evaluated according to the method described in Example 21. Table 2 shows the catalyst activity of the catalyst.

Example 25. Comparative catalyst 7

Comparative catalyst 7 is identical to catalyst 1 and was evaluated according to the method described in Example 20. Table 2 shows the catalyst activity of the catalyst.

Example 26. Comparative catalyst 8

Comparative catalyst 8 is identical to catalyst 1 and was evaluated according to the method described in Example 21. Table 2 shows the catalyst activity of the catalyst.

Table 1. Composition and specific surface area of different catalysts

Table 2. Catalytic activity evaluation results of different catalysts

As shown in Examples 1-25, a-Al ₂O ₃ hollow microspheres were prepared as a catalyst carrier by a two-step method. The carrier had a large specific surface area. The active metal and the auxiliary metal may be uniformly distributed on the surface of the microspheres. This can effectively reduce the precious metal loading and improve the activity and stability of the catalyst. The organic combination of the active metal, the auxiliary agent and the carrier could make the catalyst resistant to hydrogen in the raw material gas without the need for a special dehydrogenation device. This is beneficial to reducing the investment of the equipment and the purification cost of the raw material gas. Moreover, the catalyst has a high MN conversion rate for high NO feed and good oxalate selectivity.

The catalyst of the invention could be used for the reaction of CO and methyl nitrite to synthesize dimethyl oxalate. The hydrogen content of the raw material gas could be 1,000 ppm and the NO content could be 12%. The reaction temperature could be 115-128 ℃, and the GHSV could be 4,000-6,000 h ^-1. After 6,000 hours of stable operation, the activity of the catalyst did not decrease. The average MN conversion rate was 96-98%.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the invention.

Claims

A catalyst for synthesizing an oxalate by a CO coupling reaction, comprising:

(a) an active component comprising palladium (Pd) or an oxide thereof;

(b) an auxiliary agent comprising an auxiliary element selected from the group consisting of nickel, cobalt, manganese, zirconium, cerium, lanthanum, molybdenum, barium, vanadium, titanium, iron, yttrium, niobium, tungsten, tin and bismuth; and

(c) a carrier consisting of hollow microspheres of α-Al ₂O ₃.
The catalyst of claim 1, wherein the carrier has a specific surface area of 1-200 m ²/g.
The catalyst of claim 1, wherein the catalyst consists of the active component at a content of 0.005-1.000 wt%, the auxiliary agent at a content of 0.01-5.00 wt%, and the carrier.
The catalyst of claim 1, wherein the auxiliary element is selected from the group consisting of manganese, zirconium, cerium, lanthanum, vanadium, titanium, yttrium, niobium, tin and bismuth.
A process for preparing the catalyst of claim 1, comprising:

(a) dehydrating a carbohydrate solution to make a carbohydrate solid sample, wherein the carbohydrate solution comprises a carbohydrate having a carbonyl group, a hydroxyl group or a combination thereof;

(b) drying the carbohydrate solid sample to make a structural precursor;

(c) adding the structural precursor to an aluminum nitrate solution to make an aluminum sample;

(d) dehydrating the aluminum sample to make an aluminum solid sample;

(e) drying the aluminum solid to make a dried aluminum solid sample;

(f) calcining dried aluminum solid sample to make a carrier consisting of hollow microspheres of α-Al ₂O ₃;

(g) impregnating the carrier with an impregnation solution comprising the active component and the auxiliary agent to make a mixture;

(h) drying the mixture to make a dried mixture; and

(i) calcining the dried mixture, whereby the catalyst is prepared.
The process of claim 5, wherein the carbohydrate is selected from the group consisting of glucose, fructose, sucrose and maltose.
The process of claim 5, further comprising washing the carbohydrate solid sample with deionized water and ethanol repeatedly before step (b) .
The process of claim 5, wherein the structural precursor is added to the aluminum nitrate solution at a structural precursor/aluminum nitrate mass ratio of 1: (5-50) .
The process of claim 5, further comprising subjecting the aluminum sample to ultrasound treatment and letting it sit for 8-20 h in step (c) .
The process of claim 5, further comprising dissolving a salt of the auxiliary element and a Pd salt in deionized water to make an active component/auxiliary agent solution, and adjusting pH of the active component/auxiliary agent solution to 1-5 with diluted nitric acid, diluted hydrochloric acid, oxalic acid or citric acid to make the impregnation solution, and spraying the impregnation solution to the carrier at a volume equal to the that of the carrier.
The process of claim 10, wherein the Pd salt is selected from the group consisting of a halide, a nitrate, an acetate and an acetylacetonate.
The process of claim 10, wherein the salt of the auxiliary element is selected from the group consisting of a chloride, a nitrate, an acetate, an oxalate and an ammonium salt.
A method for reducing a catalyst for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) , comprising exposing the catalyst of claim 1 to a reducing gas at 130-220 ℃ and under an atmospheric pressure for 3-8 h, wherein the reducing gas is mixture of hydrogen (H ₂) and nitrogen (N ₂) , and has a molar H ₂ content of 5-30 %and a flow rate at 40-80 ml/min·g of the catalyst, whereby the catalyst is reduced.
A method for synthesizing an oxalate in a gas phase reaction between carbon monoxide (CO) and methyl nitrite (MN) , comprising exposing a feed gas to the catalyst of claim 1 at a temperature of 100-160 ℃ and a pressure of 0.1-0.5 MPa, wherein the feed gas is a mixture of methyl nitrite (MN) , monoxide (CO) and nitrogen (N ₂) , and has a CO/MN molar ratio of (1-3) : 1 and a volume space velocity at 3,000-10, 000 h ^-1, whereby an oxalate is synthesized.