适于木本植物油脂的催化剂研究：纳米固体超强酸催化剂对游离脂肪酸的酯化

Abstract

木本植物油脂与草本相比多为高酸价，用碱性催化剂进行酯交换时易发生皂化。两步法是先将游离脂肪酸酯化，再进行碱催化生产，可以提高资源的利用率，拓展原料的来源，降低成本。锡是少数几个可制备固体超强酸的金属。本文以掺锑二氧化锡纳米材料为基体，进行表面硫酸化。在330℃煅烧得到催化剂 /Sb-SnO2，酸性强(H0 ≥ –14.5)，超过100%硫酸(–11.9)近1000倍，为固体超强酸。TEM照片显示为纳米催化剂。将其应用在高酸值米糠油的酯化反应中，在常压、常温(70℃)下进行游离脂肪酸的酯化催化反应，对游离酸的酯化率为95%以上，残余米糠油的酸值由58.94 mg/g降到3~4 mg/g，可用液体碱催化剂继续进行酯交换反应。从而证实该催化剂可用于高酸价木本油脂两步法生成生物柴油，提高资源的利用率。 Generally woody plant oil bears a higher acid value than the oil from herbaceous plant. Basic catalyst will lead to soap reaction in transesterification of oil. Tow step method divides the production of biodiesel into the esterification of free fatty acid and the transesterification of oil, which improves resource utilization greatly and broadens sources of oil, contributing to a low cost. Sin is a few metals by which solid superacid can be prepared. The present paper used nanocrystal of SnO2 doped with Sb as carrier to superficially sulfate on it. Nano-catalyst @Sb-SnO2 calcined at 330˚C for 3 h is a solid superacid with a strong acidy, Hammett function H0 ≥ –14.5, stronger than 100% sulfuric acid (–11.9) near to 1000 times. The image of TEM showed the solid superacid is nano size. In esterification of rice bran oil with high acid value, the ratio of esterification of free fatty acid was up to 95% under normal pressure at 70˚C, and the acid value of remains of rice bran oil decreased from 58.94 to 3 - 4 mg KOH/g. So the remains of rice bran oil can be directly used for transesterification by homogeneous basic catalyst, thereby the tow step method can be practiced and enhance the utilization of rate oil resources.