CN1257014C

CN1257014C - Catalyst based on nano carbon fiber as carrier and method for preparing oxalate

Info

Publication number: CN1257014C
Application number: CN 03114989
Authority: CN
Inventors: 赵铁均; 顾雄毅; 戴迎春; 袁渭康
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2003-01-20
Filing date: 2003-01-20
Publication date: 2006-05-24
Anticipated expiration: 2023-01-20
Also published as: CN1446635A

Abstract

The present invention discloses a catalyst based on a nanometer carbon fiber as a carrier and a method for preparing oxalic ester. The catalyst is a composition, is characterized in that the catalyst comprises the nanometer carbon fiber as the carrier and metal palladium in catalytic effective quantity, and is prepared by a conventional impregnating method or deposition precipitating method. The oxalic ester can be conveniently prepared from the catalyst. Compared with a reaction of carbon monoxide and methyl nitrite to generate dimethyl oxalate, through the conversion rate and the selectivity of the methyl nitrite in a chromatogram analyzer, a result indicates that in the palladium catalyst based on a nanometer carbon fiber as a carrier, the conversion per pass of the dimethyl oxalate is more than 85% and the selectivity is approximate to 100%. Therefore, the catalyst is a catalyst for preparing the oxalic ester with good performance, and can be used for scale industrial production.

Description

Catalyst based on carbon nanofiber as carrier and method for preparing oxalate

Technical Field

The invention relates to a catalyst which takes carbon nanofibers as a carrier, palladium as active metal and added with transition metal as an auxiliary agent and a method for preparing oxalate by adopting the catalyst.

Oxalic acid and oxalate thereof are used as important chemical raw materials and widely applied to industries of medicine, dye, pesticide, precious metal extraction and the like, and can be used for producing glycol. Under normal conditions, oxalic acid is obtained by decomposing sodium formate and then reducing with sulfuric acid, the process flow is long, and the equipment is seriously corroded. The Japanese UBE company firstly proposes a method for synthesizing oxalate by coupling carbon monoxide through a palladium catalyst, and the chemical reaction formula is

The generated nitric oxide can be recycled through the following reaction, and the reaction can be carried out at normal temperature without a catalyst.

By studying carrier effect, adjuvant, etc., α -alumina was considered to be the best carrier for carbon monoxide coupled synthesis of oxalate (S.Uchiumi, K.Ataka an dT.Matsuzaki, J.org.chem.576(1999)279, T.Matsuzaki and A.Nakamura, Catal.Sur.Jpn.1(1997)77, U S Pat.4353843).

At present, the tubular carbon nanofibers show good prospects in the application of composite material reinforcing agents, electrode materials of batteries, novel hydrogen storage materials, catalyst carriers and other fields. Many applicable results have been obtained through Studies on nanocarbon fibers as catalyst carriers (M.S. Hoogenrad, R.A.G.M.van Leeuwarden, G.J.B.van Breda Vriesman, A.Broersma, A.J.van dillen and J.W.Geus, Sties Surf.Sci.C., 1994, 91: 263; J.M.Planeix, N.Costel, B.Coq, V.Brotons, P.S.Kumbrar, R.tartre, P.Genete, P.Bernier and P.M.Ajayan, J.Am.Chem.Soc.116(1994) 35; A.Chambers T.Nemes, N.M.Rodreuez T.K.K.K.J., J.am.Chem.S. Checker, Baker K.102, K.K.68, Baker K.31, K.K.K.K.K.K.10, K.103, K.K.K.K.K.K. Checker.103, K.K.K.K. K. 1998, and No. 35, No. 2, No.. Therefore, the nano carbon fiber has excellent physical and chemical properties, and is expected to replace the conventional carrier so as to improve the conversion rate and the selectivity. However, no catalyst of this type is available for industrial use, and it is therefore of great importance to develop and study a catalyst of this type that can be practically used in industrial production.

Disclosure of Invention

The invention aims to solve the technical problem of disclosing a catalyst based on carbon nanofibers as a carrier and a method for preparing oxalate by adopting the catalyst, so as to meet the requirements of relevant departments.

The technical idea of the invention is as follows:

heterogeneous catalytic reactions are widely used in the fields of petroleum, petrochemical and chemical industries, and reaction systems are characterized by the presence of a solid catalyst and reactants and products in a fluid state. In heterogeneously catalyzed reactions, the reaction takes place at the surface between the phases, i.e. the inner surface of the fluid and the catalyst. The performance of the catalyst support greatly affects the performance of the catalyst. In particular, the surface area of the catalyst support and its interaction with the active metal will affect the outcome of the catalytic reaction. Furthermore, the purity of the catalyst support and the purity of the active metal also influence the selectivity of the reaction. Generally, catalytic performance is generally proportional to the surface area of the catalyst, and therefore, higher specific surface areas are sought after by the catalyst. The rate of adsorption and desorption of reactants on the catalyst surface during the reaction is often related to the pore structure of the catalyst support.

In the process of synthesizing dimethyl oxalate by using carbon monoxide and nitrosomethyl ester in a gas phase, the reaction control step is the adsorption of the carbon monoxide on the surface of the catalyst, and an intermediate with large volume is formed in the reaction process, so that a catalyst carrier is required to have certain pore distribution.

In particular, the carbon nanofiber carrier related to the patent has few micropores, most of which are mesopores and macropores, and the atomic arrangement on the surface of the carbon nanofiber is favorable for forming a special action between an active metal and the carrier. Three kinds of carbon nanofibers with different graphite flake arrangement modes can be obtained by a catalytic chemical vapor deposition method, and are respectively called fishbone type, tubular type and flat plate type carbon nanofibers. The different structures depend on the respective catalysts, reaction temperatures and types of carbon-containing precursors.

The catalyst of the invention is a composition, which is characterized by comprising carrier nano carbon fibers and catalytically effective amount of metallic palladium, and preferably comprises the following components in percentage by weight:

90 to 98.9 percent of carrier carbon nanofiber

0.1 to 10 percent of metal palladium

1 to 10 percent of transition metal

The transition metal comprises one or more of iron, cobalt, nickel or cerium.

The carrier nano carbon fiber can be obtained by a catalytic chemical vapor deposition method disclosed by Baker, Rodriguez, J.Mater.Res.Vol.8(2), 3233-50 (1993); Langmuir, 11, 3862(1995)) documents, and the nano carbon fiber with three different graphite sheet arrangement modes are fishbone type, tubular type and flat plate type nano carbon fibers respectively.

The catalyst can be prepared by a conventional impregnation method or a precipitation method, for example, the catalyst can be prepared by the method disclosed in E.Boellaard, A.M.van der Karaan, and J.W.Gues, Studies surf.Sci.Catal., 91(1995), 931, and the invention is not repeated.

The catalyst of the invention can be used for conveniently preparing oxalate, and the specific method comprises the following steps:

putting the catalyst into a reactor, and introducing carbon monoxide, methyl nitrite and diluent gas nitrogen, wherein the reaction temperature is 80-140 ℃, and the carbon monoxide flow is 12.5 ml/min;

carbon monoxide, methyl nitrite and diluent gas nitrogen in a volume ratio of 0.5-3: 1: 5-9.

The space velocity of the reaction gasis 400h^-1-1000h^-1。

The results, as a result of conversion of methyl nitrite by a chromatographic analyzer, show that: under the same airspeed, in the palladium catalyst loaded with the carbon nanofibers as the carrier, the one-way conversion rate of dimethyl oxalate reaches 85%, and the selectivity approaches 100%, so that the catalyst provided by the invention is a catalyst with excellent performance for preparing oxalate, and can be used for large-scale industrial production.

Detailed Description

Example 1

Weighing 4.00g of tubular carbon nanofibers, adding the tubular carbon nanofibers into a pre-metered palladium chloride solution with a theoretical loading amount which can be equal to the total pore volume of the corresponding carbon nanofibers, stirring for one hour, standing overnight at 25 ℃, and drying the obtained wet solid at 120 ℃ for more than 12 hours. Heating from normal temperature to 350 ℃ at the heating rate of 2 ℃/min, maintaining for 5 hours, collecting the obtained solid, placing the solid in a reactor, reducing for 5 hours by using hydrogen in 50ml/min, and sealing for later use.

1.8g of the catalyst obtained in the above manner are weighed into a reactor and charged with COCarbon, methyl nitrite and diluent gas nitrogen, the reaction temperature can be 80-140 ℃, the corresponding flow rate is 12.5ml/min of carbon monoxide, the flow rate ratio of various gases is 12.5: 10: 77.5ml/min, and the space velocity of the reaction gas is 400h^-1The conversion rate of methyl nitrite in a chromatographic analyzer is 75 percent of the conversion rate per pass of dimethyl oxalate, and the selectivity is close to 100 percent.

Example 2

Weighing 4.00g of fishbone carbon nanofibers, preparing a palladium-supported metal catalyst with the corresponding carbon nanofibers as carriers in the same manner as in example 1, wherein the content of palladium metal can be 0.1-5%, and introducing corresponding gas for reaction by firing and reducing processes in the same way as in example 1. The conversion rate of methyl nitrite is analyzed by chromatography, the conversion rate is more than 75%, and the selectivity is close to 100%.

Example 3

For the catalyst obtained in example 1, the reaction products were changed to carbon monoxide, ethyl nitrite and nitrogen gas, and the activity was examined in the same manner as in example 1. How to examine, the conversion rate is more than 80%, and the selectivity is close to 100%.

Example 4

Weighing 4.00g of tubular carbon nanofibers, putting the tubular carbon nanofibers into a pre-metered palladium chloride solution with a theoretical loading capacity, wherein the amount of the solution can be equal to the total pore volume of the corresponding carbon nanofibers, stirring for one hour, standing overnight at 25 ℃, adding a proper amount of ferric nitrate or nickel nitrate or cerium nitrate into the obtained wet solid, controlling the amount to be 1-5 wt%, the amount of the solution to be close to the pore volume of the carbon nanofibers, drying for more than 12 hours at 120 ℃ after standing overnight, heating to 350 ℃ from normal temperature at a heating rate of 2 ℃/min, maintaining for 5 hours, collecting the obtained solid, putting the solid into a reactor, reducing for 5 hours with hydrogen in 50ml/min, and sealing for later use.

Weighing 1.8g of the catalyst obtained by the method, placing the catalyst in a reactor, introducing carbon monoxide, methyl nitrite and diluent gas nitrogen, wherein the reaction temperature can be 80-140 ℃, the corresponding flow rate is 12.5ml/. min of carbon monoxide, the flow rate ratio of various gases is 12.5: 10: 77.5ml/min, and when the reaction gas is used, the conversion rate of the methyl nitrite in a chromatographic analyzer is more than 85%, and the selectivity is close to 100%.

Example 5

The catalyst obtained in the same examples 1, 2, 3 and 4 is put into butyl nitrite solution dissolved with butanol, stirred, and is reduced for 12 hours by introducing hydrogen, then carbon monoxide is introduced for reaction, and sampling is carried out in the reaction process to analyze the concentration of butyl oxalate in the solution, so that the conversion rate is greater than 85 percent, and the selectivity is close to 100 percent.

Example 6

Mixing proper amount of potassium cyanide and palladium chloride to prepare K₂Pd(CN)₄.H₂O, firstly, treating the carbon nanofibers in air at 400 ℃ for 5 hours, placing the carbon nanofibers in a beaker containing 400ml, firstly introducing a metered ferric nitrate solution, stirring the mixture for 2 hours to form a suspension, and then slowly introducing the diluted K₂Pd(CN)₄Is passed into the suspension under vigorous stirring until precipitation is complete. After stirring overnight, filtration and multiple washings with deionized water, the solid was dried at 120 ℃ for 12 hours. The following procedure is the same as in example 1. The conversion rate of the methyl nitrite in a chromatographic analyzer is more than 85 percent, and the selectivity is close to 100 percent.

Claims

1. The catalyst based on the carbon nanofiber as the carrier is characterized by comprising the carbon nanofiber as the carrier and metal palladium with effective catalytic amount, wherein the components and the contents by weight percentage comprise:

90 to 98.9 percent of carrier carbon nanofiber

0.1 to 10 percent of metal palladium

1 to 10 percent of transition metal.

2. The catalyst of claim 1 wherein the transition metal comprises one or more of iron, cobalt, nickel or cerium.

3. The catalyst according to claim 1 or 2, wherein the carbon nanofibers are fishbone, tubular, or plate-type carbon nanofibers.

4. A method for preparing oxalate by using the catalyst as described in any one of claims 1 to 3, comprising the steps of:

the catalyst is put into a reactor, and carbon monoxide, methyl nitrite and diluent gas nitrogen are introduced into the reactor to obtain the oxalate.

5. The process according to claim 4, wherein the reaction temperature is 80 to 140 ℃.

6. The process according to claim 4, wherein the space velocity of the reaction gas is 400h^-1-1000h^-1。

7. The method of claim 4, wherein the ratio of carbon monoxide to methyl nitrite to diluent gas is 0.5-3: 1: 5-9 by volume.