Catalyst for preparing dimethyl carbonate by using urea alcoholysis and preparation method thereof

Abstract

The invention provides a catalyst for preparing dimethyl carbonate by using urea alcoholysis and a preparation method thereof. The catalyst has a specific surface area of 150-350 m / g, a specific pore volume of 0.5-2.0 cm / L and the pore-size distribution of 50-150, gamma-Al2O3 as a carrier accounts for 50-80 percentage of the catalyst by weight, and the balance comprises active constituents. The main active constituent comprises at least one of ZnO, CaO and PbO, and an active constituent oxide and an alumina carrier can form a stable spinelle structure. The catalyst has good stability, can achieve the stable operation service life longer than 500 hours, reacts with a urea methanol solution to synthesize the dimethyl carbonate with higher catalytic activity, has the simple preparation method, can finish load without special equipment, is beneficial to industrialized amplification, is a fixedly-carrier catalyst and solves the problem that the prior homogeneous catalyst is difficult to recycle.

Description

technical field [0001] The invention relates to a catalyst for producing dimethyl carbonate by alcoholysis of urea and a preparation method thereof, in particular to a supported metal oxide catalyst for producing dimethyl carbonate by reacting urea and methanol and a preparation method thereof. Background technique [0002] Dimethyl carbonate is an organic chemical with various reactivity and environmental friendliness. It can replace highly toxic phosgene and dimethyl sulfate for carbonylation, methylation, methoxylation and other reactions. The nature of the reaction has been paid more and more attention in recent years. At present, the mature synthesis methods of dimethyl carbonate mainly include phosgene method, oxidative carbonylation method and transesterification method. However, the process of phosgene method is complicated, the raw materials are highly toxic, and the by-product HCl seriously corrodes the equipment; the by-product water of the liquid-phase oxidative...

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Problems solved by technology

The carbon dioxide-methanol method mainly uses organometallic compounds as catalysts, which are expensive, have low reaction conversion rates, and are difficult to separate catalysts. The development of cheap, high-activity, and heterogeneous catalysts is the main direction of current research.

Although organotin compounds have good catalytic activity and product conversion rate, due to the high toxicity, high price, and difficulty in recovering homogeneous catalysts from products, the use of organotin compounds is affected.

[0005] CN1416949A has reported that zinc oxide is the main body, and 1~2 kinds of composite catalysts are formed in the oxides of lithium, magnesium, nickel, lead, aluminium, iron, molybdenum, zirconium and lanthanum, in urea: methyl alcohol=1: 20~40 Under the condition, ZnO-La prepared by co-precipitation method 2 o 3 Under the action of the binary catalyst, the yield of dimethyl carbonate reaches 49.7%. However, the catalyst is nano-sized particles, and there is a problem of separation from the product, which is not conducive to industrial application.

Due to the direct use of equal volume one-step impregnation method, the distribution of active components is uneven, and a large number of active components do not form a stable crystal structure with the carrier. Therefore, the active components are easy to lose during use, and the stability and life of the catalyst are not good.

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