Study On Vapour-phase Selective O-methylation Of Catechol With Methanol Over Catalysts

As an important chemical raw material,o-hydroxyanisole(guaiacol)has been widely used in pharmaceutical intermediates,spices,food additives and so on.Gas-solid phase catalysis is a relatively mature alkylation technology.Due to the low activity of commercial aluminum catalysts and the need of toxic additives in the reaction process,it is of great importance to develop new gas-solid phase alkylation catalysts with high efficiency,non-toxicity,stability and environmental protection.In this paper,the relationship between the activity difference and the structure of phosphate system catalysts was studied through the characterization of the texture properties of the catalysts.The effect of W loading on the activity of cerium phosphate catalyst was studied.The effect of W and K loading on the activity of cerium phosphate catalyst was investigated.The activity difference of different phosphate and the effect of W loading on the catalyst were investigated.The main results are as follows:(1)Study on the performance of different catalysts for the alkylation of catecholComparing α and γ phase activated alumina,ZSM-5,HAP,SAPO-34,MCM-22 and cerium phosphate,it was found that cerium phosphate has the highest catalytic performance.For the mono-etherification reaction catalyst,the higher the surface acidity,the higher the activity.The strong acidity promotes the deposition of carbon deposits and deactivates the catalyst.The strength of the weak alkalinity determines the selectivity of the monoetherification.These factors work together.In the catalyzed process of catechol monoetherification.Cerium phosphate has the highest weak acidity and reactivity.(2)Catalytic performance of phosphate system catalyst for catechol monoetherificationA series of phosphate catalysts were prepared by precipitation method.It was found that the catalytic performance of cerium phosphate is the best,the highest conversion rate can reach80%,and the monoetherification selectivity can reach 98%.The stronger the surface acidity of the catalyst,the higher the reaction activity,the stronger the surface acidity,and the faster the carbon deposition rate;the stronger the surface alkalinity,the higher the monoetherification selectivity.(3)The influence of additives W or K on the catalytic effect of cerium phosphate catalyst for alkylationThe supporting agent W can improve the alkylation activity of the catalyst.When the supporting amount is 1%wt,the alkylation activity of the catalyst is the highest.Theintroduction of the promoter W can significantly increase the weak acid strength of the catalyst surface,significantly increase the activity of the catalyst,and have little effect on the strong acid strength,and the stability of the catalyst remains unchanged;the weak alkalinity of the catalyst surface is reduced,and the catalyst is monoetherified.The selectivity has also been reduced after the impact.When the promoter K is introduced into the W-supported cerium phosphate catalyst,the stability of the catalyst is obviously improved.