CN1231216A

CN1231216A - Process for preparing Pd/NaY catalyst used in CO low pressure synthesizing dimethyl carbonate

Info

Publication number: CN1231216A
Application number: CN 99100459
Authority: CN
Inventors: 马新宾; 许根慧; 何菲; 王保伟
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 1999-02-01
Filing date: 1999-02-01
Publication date: 1999-10-13
Anticipated expiration: 2019-02-01
Also published as: CN1078098C

Abstract

The preparation method of Pd/NaY catalyst for low-pressure synthesis of dimethyl carbonate with CO uses palladium chloride as raw material and includes the following steps: dissolution reaction to produce Pd (NH3)4Cl2, ion exchange with molecular sieve, washing with deionized water, drying and roasting to obtain the Pd/NaY catalyst which contains 0.5-2.0 wt% of metal palladium and no chlorine ion. Said catalyst has no corrosive action on the equipment, and does not affect the chroma of the product dimethyl carbonate.

Description

Preparation method of Pd/NaY catalyst for synthesizing dimethyl carbonate by CO at low pressure

The present invention belongs to a preparation method of Pd/NaY catalyst.

Dimethyl carbonate (DMC) is a very useful organic synthetic intermediate and a gasoline additive with excellent performance as a non-toxic chemical. The current advanced production method is a methanol oxidation carbonylation method, particularly, a CO low-pressure gas phase catalytic synthesis of dimethyl carbonate is to introduce a cocatalyst of methyl nitrite (oxygen carrier) in the gas phase methanol oxidation carbonylation synthesis process, CO reacts with the CO to generate DMC, nitric oxide generated in the reaction process further reacts with methanol and oxygen to generate methyl nitrite, and the whole process forms a self-closed cycle process without three wastes discharge. The reaction equation is as follows:

and (3) synthesis reaction: (1)

and (3) regeneration reaction: (2)

the catalyst used in the process of synthesizing dimethyl carbonate by reacting carbon monoxide with methyl nitrite is generally a supported palladium catalyst, the carrier is active carbon, and the active component is PdCl₂The auxiliary agent is CuCl₂、FeCl₃And the like. The activity of the catalyst is reduced due to the loss of chloride ions in the reaction process, so that chloride needs to be supplemented in the reaction raw material gas in the reaction process, and a trace amount of HCl gas is generally supplemented to maintain the activity of the catalyst, but serious equipment corrosion problems and poor chromaticity of the product dimethyl carbonate are caused due to the supplementation of HCl.

The invention aims to provide a preparation method of a Pd/NaY catalyst for low-pressure synthesis of dimethyl carbonate by CO. The catalyst prepared by the method is used in the process of synthesizing the dimethyl carbonate, not only has good catalytic performance, but also has no corrosion effect on equipment and does not influence the product chromaticity.

In order to achieve the above object, the present invention is achieved by the following technical means. Pd (NH) is prepared by taking a molecularsieve as a carrier and palladium chloride as a raw material through a dissolution reaction₃)₄Cl₂The solution is subjected to ion exchange with a molecular sieve, and then washed, dried and roasted by deionized water to finally prepare a Pd/NaY catalyst containing 0.5-2.0 wt% of metallic palladium and free of chloride ions, wherein the Pd/NaY catalyst is characterized in that: the atomic ratio of silicon to aluminum of the molecular sieve material is 25-3.0; the adopted solvent is 35 wt% of ammonia water, and the pH value of the solution is adjusted to 7-9; the drying temperature of the catalyst is 70-100 ℃, the roasting temperature is 150-250 ℃, and the roasting time is 2-3 hours.

The Pd/NaY catalyst prepared by the method is used in the process of synthesizing dimethyl carbonate by CO at low pressure, the suitable reaction conditions are that the reaction temperature is 80-120 ℃, the pressure is 0.1-0.3 MPa, the space velocity is 1000-7000 h, and the composition of the synthesis reaction raw material gas is (mol%): CO 10% -30%, CH₃ONO8％～20％、NO2％～7％、CH₃OH5％～10％、CO₂1 to 5 percent of the total weight of the catalyst, and the balance of inert gas nitrogen. The source of the purified feed gas CO used by the invention is not limited, and the CO can be carbon monoxide in tail gases such as coal synthesis gas, converter gas of a steel mill, blast furnace gas, yellow phosphorus production tail gas, synthetic ammonia copper purge gas, sealed calcium carbide furnace and the like, and the CO content can be used after purification and purification reaches more than 80%.

Embodiments of the invention will now be described as follows:

example (1):

0.25g of PdCl are weighed out₂Dissolved in 5ml of 35% ammonia water at 60 ℃ and then added with 15ml of deionized water to form Pd (NH)₃)₄Cl₂15g of NaY molecular sieve with the silicon-aluminum ratio of 2.7 is added into the aqueous solution, and exchange is carried out for 36h at room temperature. Washing with deionized water until no chloride ion is detected, oven drying at 85 deg.C, calcining at 200 deg.C in air atmosphere for 2 hr, and calcining at 100 deg.C with CO and N containing CO5 mol%₂Mixed gas reduction1 wt% Pd/NaY catalyst can be prepared in 3 h.

5ml of the 1 wt% Pd/NaY catalyst prepared by the method is placed in a tubular fixed bed reactor, inert fillers with the same particle size as the catalyst are filled above and below a reaction bed layer to ensure that reaction airflow is preheated and uniformly distributed, and an automatic temperature control device is adopted to ensure that the temperature deviation of the reaction bed layer is not more than +/-0.5 ℃ and the temperature of the catalyst bed layer is 100 ℃. The composition of the reactor inlet feed was CO 20%, CH₃ONO16％、NO3％、CH₃OH5％、CO₂1％、N₂55 percent, the reaction temperature is 100 ℃, the reaction pressure is normal pressure, and the space velocity (GHSV) is 3000h¹The reaction product was collected using low temperature methanol and the product composition was analyzed by gas chromatography. The space-time yield of dimethyl carbonate is 326 g/l.h, the selectivity is 92.8 percent, and the by-products of the product comprise dimethyl oxalate and methyl formate.

Comparative example (1):

weighing 0.25g of PdCl₂Dissolved in 5ml of 35% ammonia water at 60 ℃ and then added with 15ml of deionized water to form Pd (NH)₃)₄Cl₂15g of NaY molecular sieve with the silicon-aluminum ratio of 2.7 is added into the aqueous solution, and exchange is carried out for 36h at room temperature. Washing with deionized water until no chloride ion is detected, oven drying at 85 deg.C, baking at 150 deg.C for 2 hr in air atmosphere, and calcining at 100 deg.C with H-containing solution₂5 mol% of H₂、N₂The mixed gas is reduced for 3 hours to prepare the 1 wt% Pd/NaY catalyst.

5ml of the 1 wt% Pd/NaY catalyst prepared by the above method was placed in a tubular fixed bed reactor, and the space-time yield of dimethyl carbonate was 325 g/l.h under the reaction conditions of example (1), the selectivity was 92.7%, and the by-products were dimethyl oxalate and methyl formate.

Example (2):

0.13g of PdCl are weighed out₂Dissolved in 2.5ml of 35% ammonia at 60 ℃ and then added with 15ml of deionized water to form Pd (NH)₃)₄Cl₂15g of NaY molecular sieve with the silicon-aluminum ratio of 2.7 is added into the aqueous solution, and exchange is carried out for 36h at room temperature. Washing with deionized water until no chloride ion is detected, oven drying at 85 deg.C, calcining at 150 deg.C in air atmosphere for 2 hr, and calcining at 100 deg.C with CO and N containing CO5 mol%₂The mixed gas is returned for 3 hours to prepare the 0.5 wt% Pd/NaY catalyst.

5ml of the 0.5 wt% Pd/NaY catalyst prepared by the above method was placed in a tubular fixed bed reactor, and the space-time yield of dimethyl carbonate was 306 g/l.h under the reaction conditions of example (1), the selectivity was 94.3%, and the by-products were dimethyl oxalate and methyl formate.

Example (3):

0.38g of PdCl are weighed out₂Dissolved in 7.5ml of 35% ammonia at 60 ℃ and then added with 12.5ml of deionized water to form Pd (NH)₃)₄Cl₂15g of NaY molecular sieve with the silicon-aluminum ratioof 2.8 is added into the aqueous solution, and exchange is carried out for 48 hours at room temperature. Washing with deionized water until no chloride ion is detected, oven drying at 85 deg.C, calcining at 150 deg.C in air atmosphere for 2 hr, and calcining at 100 deg.C with CO and N containing CO5 mol%₂MixingThe gas reduction is carried out for 3 hours to obtain the 1.5 wt% Pd/NaY catalyst.

5ml of the 1.5 wt% Pd/NaY catalyst prepared by the above method was placed in a tubular fixed bed reactor, and the space time yield of dimethyl carbonate was 343 g/l.h under the reaction conditions of example (1), the selectivity was 91.5%, and the by-products were dimethyl oxalate and methyl formate.

Example (4):

0.5g of PdCl are weighed out₂Dissolved in 10ml of 35% ammonia water at 60 ℃ and then added with 10ml of deionized water to form Pd (NH)₃)₄Cl₂The aqueous solution was exchanged for 48h at room temperature by adding 15g of NaY molecular sieve with a Si/Al ratio of 2.8. Washing with deionized water until no chloride ion is detected, oven drying at 85 deg.C, calcining at 150 deg.C in air atmosphere for 2 hr, and calcining at 100 deg.C with CO and N containing CO5 mol%₂The mixed gas is reduced for 3 hours to prepare the 2 wt% Pd/NaY catalyst.

5ml of the 2 wt% Pd/NaY catalyst prepared by the above method was placed in a tubular fixed bed reactor, and the space-time yield of dimethyl carbonate was 315 g/l.h under the reaction conditions of example (1), the selectivity was 90.6%, and the by-products were dimethyl oxalate and methyl formate.

Claims

1. A process for preparing Pd/NaY catalyst used to synthesize dimethyl carbonate by CO low-pressure method includes dissolving Pd chloride in molecular sieve as carrier to obtain Pd (NH)₃)₄Cl₂And (2) carrying out ion exchange on the solution and a molecular sieve, washing by using deionized water, drying and roasting to finally obtain the chloride ion-free Pd/NaY catalyst containing 0.5-2.0 wt% of metal palladium, and the method is characterized by comprising the following steps: the atomic ratio of silicon to aluminum of the molecular sieve material is 2.5-3.0; the method is characterized in that 35 wt% of ammonia water is adopted as a solvent, the pH value of the solution is adjusted to be 7-9, the drying temperature of the Pd/NaY catalyst is 70-100 ℃, and the roasting temperature is 150-250 ℃.