Study On The Preparation Of Methylal By One Step Process From Methanol

Methylalhyde?DMM?is an important methanol derivative.It has good solubility,high oxygen content and low toxicity.It is widely used in the industry,for example,as a solvent for fine chemicals,a diesel additive,and a raw material for the synthesis of high-concentration formaldehyde.Provide hydrogen source for fuel cells.The process of one-step methanol synthesis of methyl acetal has attracted more and more attention because of its environmental protection.At present,the research on the catalytic system of this process is mainly focused on three catalytic systems such as supported noble metals,heteropoly acids,and vanadium-based catalysts.However,from the perspective of the overall study,all three catalysts have the disadvantages of high catalyst cost,weak industrial properties,too strong acidity,strong corrosiveness to the equipment,and difficulties in separation and recovery.In this paper,a highly active,highly selective iron-molybdenum based bifunctional catalyst was developed for the above problems,and it was associated with the selective oxidation of methanol.The iron-molybdenum-based bifunctional catalysts prepared with different Mo/Fe ratios and different supports?Y-type molecular sieves,ZSM-5,SiO₂,Al₂O₃?were used to compare the catalytic activity and obtained The optimum Mo/Fe ratio is 2:1,and the best carrier is Y-type molecular sieve.It was confirmed that the Fe-Mo/Y zeolite catalyst is the best iron-molybdenum-based dual-function catalyst,and 91.5%DMM selectivity is achieved at663K.Since the methanol conversion of these basic iron-molybdenum based bifunctional catalysts is not ideal,the catalyst is further optimized based on the previous experiments.The results show that the catalytic performance of Fe-Mo/Composite 1 catalyst is better than that of a single supported Fe-Mo-based bifunctional catalyst.The excellent catalytic performance of Fe-Mo/Composite 1 catalyst not only benefits from the effective synergistic effect of iron and molybdenum,but also enhances the oxidizing ability of the catalyst.It also contributes to the synergistic effect of the Lewis acid site and B acid site of the compounded support to obtain the catalyst.The best match between the redox site and the acid site has the best catalytic activity,achieving 66.74%methanol conversion and 87.66%DMM selectivity at663K.Afterwards,the effects of reaction temperature,material ratio,reaction space velocity and other technological conditions on the production of methylal in one-step methanol were investigated.In addition,an orthogonal experiment with three factors and five levels was designed.Finally,the best process conditions were obtained:reaction temperature:663K The reaction space velocity is 7500 h^-1 and the methanol air ratio is 55%.Through the investigation of the stability of the catalyst,it was found that as the reaction time prolonged,the activity of the catalyst decreased and then remained unchanged,and the amount of decrease was small.Therefore,the catalyst had good stability and passed XRD,SEM and coke amount.The measurement also confirmed that the catalyst has better stability.