SO_4^(2-)/TiO_2固体酸煅烧条件对其催化酯化反应活性的影响

Influence of the Calcination Conditions of Sulphated Titania on the Activity in the Esterification of High Acid Value Oil

以高酸值麻疯树油中游离脂肪酸与甲醇酯化反应作为目标反应,通过直接煅烧偏钛酸,得到了高酯化活性的 ST(SO_4^(2-)/TiO_2)固体酸催化剂,并用 X 射线衍射(XRD)、热重分析(TG)、BET 吸附等方法对其进行了表征。ST 固体酸制备过程中,煅烧温度是一个敏感的因素,而煅烧时间影响较小。随着煅烧温度的提高.强酸位数量逐渐增加,弱酸位数量逐渐减少。过高的煅烧温度将导致表面磺酸基团分解脱附,酸位强度和数量都迅速降低,酯化活性迅速降低。同时随着煅烧温度的提高,样品表面积和孔体积的减小也可能导致酯化活性降低。对于麻疯树油中游离脂肪酸与甲醇的酯化反应,酸强度 H_0介于-12.7与-8.2之间的酸中心具有较好的催化活性。

ST （SO4^2-/TiO2） solid acid catalysts with high activity, for the esterification of free fatty acid in high acid value Jatropha curcas L. oil with methanol, were prepared by directly calcining cheap metatitanie acid. The ST solid acid catalysts were eharaeterised using XRD, TG and BET techniques. The results proved that calcination temperature was a vital factor and that calcination time was a subsidiary factor in the process of preparation of ST solid acid. The strong acid site increased and the weak acid site decreased with the calcination temperature increasing. Since the surface sulfate decomposed at higher calcinations temperature, the amount and strength of acid site deceased sharply, which induced the decreasing of the esterifieation activity of the ST solid acid. The decreasing of BET area and pore volume possibly resulted in the decreasing of the esterifieation activity with calcination temperature increasing from 300 ℃ to 600 ℃. For the esterification of free fatty acid in high acid value Jatropha curccas L. oil with methanol, the acid site in Ho between - 12. 70 and - 8.2 has better catalytic activity.