木质素磺酸盐制取香兰素的氧化反应

OXIDATION OF LIGNOSULFONATE TO VANILLIN

本文对亚硫酸盐木材纸浆废液中的木质素磺酸盐在碱性、空气氧化反应中对氢氧化钠、香兰素和碳酸钠的浓度变化规律进行了分析。对于固形物浓度为20%、28%和35%的废液,氢氧化钠加入量的合理范围分别80～110,95～140和110～160g/L。在废液固形物浓度28%、表压1.44MPa、180℃、空气体积流速3L/L·min 的条件下,香兰素的产量为10.8～14.3g/L,香兰素对木质素的得率为7.6～10.0%,反应时间为50min。

Concentration changes of vanillin,NaOH and Na_2CO_3 in the course of alkaline air oxidation of lignosulfonate present in spent sulfite liquor were investigated by using a 7-L pressurized reactor. NaOH is consumed in the production of vanillion,the reaction with organic acids,and the reaction with H_2CO_3 derived from the oxidation of organic matter.A small portion of NaOH is present as free alkaline to maintain the liquor's alkalinity.Thus 40 g/L Ca(OH)_2 was added to precipitate car- bonates and to reduce the requirement of NaOH.The reasonable ranges of the amount of NaOH added were determined as 80-110,95-140,and 110-160 g/L for the spent sulfite liquor containing 20 %,28 %,and 35 %solids,respectively.Within these ranges,however,the upper limits are recommended for the best profitability.When it is oxidized at 1.44 MPa,180℃ for 50 min,with an air space velocity of 3 L/L·min,10.8—14.3 g/L of vanillin was produced from the spent sul- rite liquor containing 28 % solids,and the vanillin yield(based on lignin)was 7.6—10.0 %. Further improvement of the process was achieved by reducing the liquor's sugar content through pentose fermentation,by which the alkaline consumption was reduced by 15 % as compared with the conventional hexose fermentation process.