准毛细间隙反应器中直接电氧化合成茴香醛二甲基缩醛

Direct electrooxidation synthesis of anisaldehyde dimethyl acetal in a quasi capillary gap cell

以准毛细间隙反应器为电化学合成装置，采用恒电流电解技术考察了阳极材料、支持电解质、电流密度等工艺参数对茴香醚直接电氧化合成茴香醛二甲基缩醛的影响。结果表明，收率从高到低采用的阳极材料依次为：石墨＞钛基铱钽＞钛基钌铱＞钛基铂；支持电解质依次为：对甲基苯磺酸钠＞苯磺酸钠＞氟化钾＞甲醇钠＞高氯酸钠＞间硝基苯磺酸钠；在电流密度1～9 A·dm-2范围内，反应选择性随着电流密度的增大而减小；添加适量的2,6-二甲基吡啶能抑制茴香醛二甲基缩醛的氧化从而提高反应选择性。在优化条件下，茴香醛二甲基缩醛的收率和电流效率分别达到75%和47%。

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＆amp;nbsp;of 20 L · h-1 at temperature 40℃. The research provided an important basis for commercialization of electrochemical oxidation synthesis of p-MBDMA.