关键词: 准毛细间隙反应器, 茴香醚, 茴香醛二甲基缩醛, 电化学, 氧化, 电解质, 工艺条件

Abstract: The influences of anodic electrode material,supporting electrolyte and current density on the direct electrochemical oxidation synthesis of anisaldehyde dimethyl acetal (p-MBDMA) in a quasi capillary gap cell were investigated by the galvanostatic method. The electrochemical behavior of p-methoxytoluene (p-MT) and p-MBDMA in methanol was studied with linear sweep voltammetry. The experimental results showed that graphite as anodic material revealed good electrochemical catalytic activity to the oxidation of p-MT. The p-MBDMA yield of four anodic materials decreased in the following order:graphite > Ir-Ta/Ti > Ru-Ir/Ti > Pt/Ti and six supporting electrolytes followed the decreasing order:sodium p-toluenesulfonate > sodium benzenesulfonate > potassium fluoride > sodium methoxide > sodium perchlorate > sodium 3-nitrobenzenesulfonate. With current density varying from 1 to 9 A·dm^-2,reaction selectivity decreased with increasing current density. Furthermore,a proper amount of addition of 2,6-lutidine could improve the selectivity by avoiding further oxidation of p-MBDMA. Under the optimized conditions of 0.8～1.0 mol·L^-1 p-MT,1.0% (mass) sodium p-toluenesulfonate as supporting electrolyte and addition of 0.5% (mass) 2,6-lutidine,yield and current efficiency could reach 75% and 47% respectively. During the process of electrolysis,current density changed from 3.0 to 2.0 A·dm^-2 at 0.8 Q^* and the operating condition was under the electrolyte solution flow rate of 20 L·h^-1 at temperature 40℃. The research provided an important basis for commercialization of electrochemical oxidation synthesis of p-MBDMA.

Key words: quasi capillary gap cell, p-methoxytoluene, anisaldehyde dimethyl acetal, electrochemistry, oxidation, electrolytes, process condition