CN102698793A - Catalyst for preparing cyclohexanol and cyclohexanone from cyclohexane through catalytic oxidation - Google Patents

Abstract

The invention discloses a Ce-loaded MCM-48 mesoporous molecular sieve catalyst for preparing cyclohexanol and cyclohexanone by catalytic oxidation of cyclohexane and a preparation method thereof. The catalyst prepared by the present invention first adopts the hydrothermal method to prepare MCM-48 mesoporous molecular sieve, and then through the complexation of rare earth Ce by organosilylating reagent and the reaction with the hydroxyl group on the surface of MCM-48 mesoporous molecular sieve, Ce is carried on the Made on MCM-48 mesoporous molecular sieve. Under the condition that oxygen is an oxidant and there is no solvent, the catalyst prepared by the invention can achieve a conversion rate of cyclohexane up to 18.6%, and a total selectivity of cyclohexanol and cyclohexanone up to 90.8%. The catalyst prepared by the invention has the characteristics of simultaneously obtaining high activity and high alcohol and ketone selectivity, and the active component Ce of the catalyst is not easily lost during the reaction process.

Description

A kind of catalyst for the catalytic oxidation of cyclohexane to prepare cyclohexanol and cyclohexanone

technical field

The present invention relates to a kind of catalyst that is used for the catalytic oxidation of cyclohexane to prepare cyclohexanol and cyclohexanone and its preparation method and application. The hydroxyl groups on the surface of the pore molecular sieve reacted, and Ce was loaded on the MCM-48 mesoporous molecular sieve to make a catalyst. Under the conditions of no solvent and oxygen as the oxidant, the catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone was carried out.

Background technique

The catalytic oxidation reaction of cyclohexane is a very important reaction process. The cyclohexanol and cyclohexanone obtained from the oxidation of cyclohexane are important organic chemical raw materials and organic solvents. They are the raw materials for the manufacture of nylon-6 and nylon-66 . In addition, cyclohexanol and cyclohexanone are also used as solvents for resins, fats, paraffin oils, butyl rubber, etc., and are widely used in industries such as medicine, coatings, rubber, and pesticides.

At present, cyclohexanol and cyclohexanone are mainly produced by cyclohexane oxidation, among which the cyclohexane oxidation technology (DSM/HPO) developed by Dutch mining company is the most mature industrial technology at present, but the single-pass conversion rate of cyclohexane is only About 4%, the selectivity is about 80%, the production efficiency is low, the material consumption is large, and the pollution is relatively serious. In order to develop the production process of cyclohexanol and cyclohexanone, scholars at home and abroad have done a lot of research work on the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone. Compared with oxidants such as hydrogen peroxide and tert-butyl hydroperoxide, oxygen is used as oxidant, and cyclohexane is selectively oxidized to cyclohexanol and cyclohexanone without adding any solvent, because it has less energy consumption , less waste, environmental friendliness and other advantages, has been widely concerned by researchers.

At present, some patents have disclosed several molecular sieve catalysts for oxygen oxidation of cyclohexane. Chinese patent CN102211035A discloses a vanadium-doped ZSM-5 molecular sieve catalyst for cyclohexane oxidation reaction. When the molar ratio of vanadium to silicon in the catalyst is 0.02-0.03, the oxygen pressure is 0.5-2.5MPa, and the reaction temperature is 80-150°C, the conversion rate of cyclohexane can reach up to 14.7% within 1-10 hours of reaction, and cyclohexanol and cyclohexanol The overall selectivity to hexanone was 97.3%. Chinese patent CN101773849A discloses a copper-doped AlPO-5 molecular sieve catalyst for cyclohexane oxidation reaction. When the oxygen pressure is 0.5MPa and the reaction temperature is 140°C, the reaction 5h cyclohexane conversion rate is 8.2%. The total selectivity of hexanol and cyclohexanone is 98%. Chinese patent CN1781889A discloses a microporous molecular sieve loaded Pd or Pt noble metal catalyst for cyclohexane oxidation reaction. When the oxygen pressure is 0.9-1.0 MPa, the reaction temperature is 100-130 DEG C, and the precious metal is Pt, the conversion rate of cyclohexane is 13.5%, and the total selectivity of cyclohexanol and cyclohexanone is higher than 92%. Chinese patent CN1810746A discloses a Ce/AlPO-5 molecular sieve catalyst, under 0.5MPa oxygen condition, 140 ℃ reaction 4h, cyclohexane conversion can reach 13%, and the total selectivity of cyclohexanol and cyclohexanone is 92 %.

In addition, some literatures have also reported the application of molecular sieve catalysts in the catalytic oxidation of cyclohexane. Li et al. prepared HMS molecular sieve catalysts modified by different metal elements (Ce, Ti, Co, Al, Cr, V, Zr), and found that the activity of CeO ₂ /V-HMS molecular sieve catalyst was the highest, under the condition of 0.5MPa oxygen , 140°C for 4 hours, the conversion rate of cyclohexane can reach 18%, but the selectivity of cyclohexanol and cyclohexanone is low, only 68% (Ind. Eng. Chem. Res. 2010, 5392: 5399). Zhan et al. prepared Ce-doped mesoporous material MCM-48 by hydrothermal method, and reacted at 140°C for 5 hours at an oxygen pressure of 0.5 MPa, and the conversion rate of cyclohexane was up to 8.1%. Cyclohexanol and cyclohexane The selectivity to ketones is 98.7% (J. RareEarths 2008, 515:522). Zhao et al. prepared a mesoporous silica-supported Au catalyst, stirred and reacted for 2 h at 1 MPa oxygen pressure and 150 °C, the conversion rate of cyclohexane was 16.6%, and the selectivity of cyclohexanol and cyclohexanone was 92.4% (Catal . Today 2010, 158: 220). Yang et al. prepared MCM-41 mesoporous molecular sieve-supported Ag catalyst, using _O2 as the oxidant, under the conditions of temperature 150 ° C and pressure 1.4 MPa, after stirring for 3 h, the conversion rate of cyclohexane can reach 10.7%. The overall selectivity of alcohols and ketones is 83.4% (J Porous Mater. 2011, 18:735).

In summary, by loading different metals on molecular sieves, molecular sieve catalysts with certain activity for cyclohexane oxidation can be obtained, and the activity is directly related to the properties of the supported metals. However, the existing catalysts still have the following disadvantages: (1) it is difficult to obtain high cyclohexane conversion rate and alcohol and ketone selectivity at the same time; (2) some highly active catalysts use noble metals as active components, and the catalyst cost is relatively low. high. Therefore, this patent uses Ce as the active component, utilizes the complexation of rare earth Ce by organosilylating reagents, and then reacts with the hydroxyl groups on the surface of mesoporous molecular sieves to load Ce in a point-to-point manner on MCM-48 mesoporous molecular sieves. The MCM-48 mesoporous molecular sieve catalyst loaded with Ce was prepared. The advantage of this preparation method is that more active components Ce can be loaded onto molecular sieves in a highly dispersed state, thereby endowing the catalyst with higher cyclohexane oxidation activity, and the catalyst prepared by this method has better stability , the active component Ce is not easily lost during the reaction.

Contents of the invention

The purpose of the present invention is to prepare a Ce-loaded MCM-48 mesoporous molecular sieve catalyst through the complexation of rare earth Ce by an organosilylating agent and the reaction with the hydroxyl group on the surface of the mesoporous molecular sieve. Under conditions such as oxygen being an oxidizing agent and no solvent, the catalyst has high activity and selectivity for the oxidation reaction of cyclohexane.

The organosilylating reagents are aminopropyltrimethoxysilane (APTMS) or 3,3,3-trifluoropropyltrimethoxysilane (FPTES), wherein the mass fraction of Ce is 0.9% to 9.5%, and the loading amount of organic matter is 0.56～1.54mmol/g.

First synthesize MCM-48 mesoporous molecular sieve by hydrothermal method, then mix cerium nitrate hexahydrate with aminopropyltrimethoxysilane or 3,3,3-trifluoropropyltrimethoxysilane, then add absolute ethanol, After stirring evenly, add MCM-48 mesoporous molecular sieve, and then stir and reflux at 50-80°C for 3-8 hours. After the reaction is finished, filter with suction and wash with absolute ethanol, and finally dry the obtained solid at 80-120° C. for 2-24 hours to prepare a Ce-loaded MCM-48 mesoporous molecular sieve catalyst.

The reaction conditions of the present invention are as follows: the oxygen pressure is 0.5 MPa, the reaction temperature is 140°C-180°C, the reaction time is 4h-10h, and the catalyst usage is 5mg.

Detailed ways

Example 1

Using hexadecyltrimethylammonium bromide as a template and ethyl orthosilicate as a silicon source to prepare pure silicon MCM-48, the specific process is: dissolve 0.6g of sodium hydroxide in 30mL of deionized water, and then add 5.2g of cetyltrimethylammonium bromide, stirred at 50°C for 1h, then added 6.0g of ethyl orthosilicate dropwise, stirred for 3h, then transferred the mixture into a 100mL crystallization kettle with a polytetrafluoroethylene liner , after crystallization at 100°C for 3 days, suction filtration and deionized water washing were performed, and then the obtained solid was dried at 100°C and calcined at 550°C for 6 hours to obtain MCM-48 mesoporous molecular sieve.

Mix 0.02g of cerium nitrate hexahydrate with 0.54g of aminopropyltrimethoxysilane, and add 30mL of absolute ethanol. After stirring evenly, add 0.3g of MCM-48 mesoporous molecular sieve, and then stir and reflux at 80°C for 3h. Suction filtration and washing with absolute ethanol were performed after completion, and the obtained solid was dried at 100° C. for 2 hours to obtain Ce-loaded MCM-48 mesoporous molecular sieve catalyst 1 .

Catalyst activity evaluation conditions are: put 5mg of catalyst and 10mL of cyclohexane solution in a reaction kettle, fill with 0.5MPa oxygen, and then react at 140°C for 4h, centrifuge after the reaction, and analyze the reaction product with a gas chromatograph . The activity evaluation results are shown in Table 1.

Example 2

The 0.02 g of cerium nitrate hexahydrate in Example 1 was increased to 0.15 g, and the other processes were the same as in Example 1 to obtain Ce-loaded MCM-48 mesoporous molecular sieve catalyst 2. The catalyst activity evaluation conditions are the same as in Example 1, and the activity evaluation results are shown in Table 1.

Example 3

The 0.02 g of cerium nitrate hexahydrate in Example 1 was increased to 0.20 g, and the other processes were the same as in Example 1 to obtain Ce-loaded MCM-48 mesoporous molecular sieve catalyst 3. The catalyst activity evaluation conditions are the same as in Example 1, and the activity evaluation results are shown in Table 1.

Example 4

Aminopropyltrimethoxysilane in Example 1 is changed to 3,3,3-trifluoropropyltrimethoxysilane, other processes are the same as in Example 1, and the MCM-48 mesoporous molecular sieve catalyst loaded with Ce is obtained 4. The catalyst activity evaluation conditions are the same as in Example 1, and the activity evaluation results are shown in Table 1.

Example 5

Aminopropyltrimethoxysilane in Example 1 is changed to 3,3,3-trifluoropropyltrimethoxysilane, and the added 0.02g cerium nitrate hexahydrate is increased to 0.11g, and other processes are the same as in Example 1 , to obtain Ce-loaded MCM-48 mesoporous molecular sieve catalyst 5. The catalyst activity evaluation conditions are the same as in Example 1, and the activity evaluation results are shown in Table 1.

Example 6

Aminopropyltrimethoxysilane in Example 1 is changed to 3,3,3-trifluoropropyltrimethoxysilane, and the added 0.02g cerium nitrate hexahydrate is increased to 0.20g, and other processes are the same as in Example 1 , to obtain Ce-loaded MCM-48 mesoporous molecular sieve catalyst 6. The catalyst activity evaluation conditions are the same as in Example 1, and the activity evaluation results are shown in Table 1.

Example 7

The catalyst preparation conditions were the same as in Example 5. The reaction temperature was increased to 180° C., other reaction conditions were the same as in Example 1, the conversion rate of cyclohexane was 18.3%, and the selectivity of cyclohexanol and cyclohexanone was 92.7%.

Example 8

The catalyst preparation conditions were the same as in Example 5. The reaction time was extended to 10 hours, other reaction conditions were the same as in Example 1, the conversion rate of cyclohexane was 18.6%, and the selectivity of cyclohexanol and cyclohexanone was 90.8%.

Table 1 Catalyst performance evaluation results

Claims (3)

1. catalyst that is used for cyclohexane oxidation system cyclohexanol and cyclohexanone; Through organic-silylation reagent to the complexing of Rare-Earth Ce and with the hydroxyl reaction on mesopore molecular sieve surface, Ce is supported on the MCM-48 mesopore molecular sieve and makes, wherein organic-silylation reagent is respectively aminopropyl trimethoxysilane and 3; 3; 3-trifluoro propyl trimethoxy silane, the Ce mass percent is 0.9%～9.5%, carrying capacity is 0.56～1.54mmol/g on the organic matter.This catalyst can be solvent-free and be under the condition of oxidant with oxygen, and the catalytic oxidation cyclohexane generates cyclohexanol and cyclohexanone.

2. the preparation method who is used for the MCM-48 mesoporous molecular sieve catalyst that supports Ce of cyclohexane oxidation according to claim 1 is characterized in that:

At first through the synthetic MCM-48 mesopore molecular sieve of hydro-thermal method; Then with six nitric hydrate ceriums and aminopropyl trimethoxysilane or 3; 3,3-trifluoro propyl trimethoxy silane mixes, and adds absolute ethyl alcohol again; Add the MCM-48 mesopore molecular sieve after waiting to stir, then at 50～80 ℃ of following stirring and refluxing 3～8h.Carry out suction filtration after question response finishes and use absolute ethanol washing, with the solid that obtains dry 2～24h under 80～120 ℃, make the MCM-48 mesoporous molecular sieve catalyst that supports Ce at last.

3. the described application of MCM-48 mesoporous molecular sieve catalyst in cyclohexane oxidation system cyclohexanol and cyclohexanone that supports Ce of claim 1; It is characterized in that; Employing oxygen is oxidant, does not add any solvent, and reaction temperature is 140～180 ℃; Reaction time is 4～10h, and oxygen pressure is 0.5MPa.