固體鹼觸媒應用於填充床反應器生產生質柴油

Abstract

生質柴油是一種替代能源，其化學結構為脂肪酸酯類，可由轉酯化反應產生。CaO當做生產生質柴油的觸媒，有極佳的反應性，但CaO的表面活性基會被空氣中水氣及二氧化碳毒化。過去文獻中指出，CaO在轉酯化反應中會和副產物甘油形成Ca(C3H7O3)2的結構，此觸媒基結構不會受空氣影響，可重複使用。本研究由CaCO3製備Ca(C3H7O3)2/CaCO3固體鹼觸媒，此結構的好處是在表面形成觸媒活性基Ca(C3H7O3)2，但內部仍有碳酸鈣為支撐保有機械強度，有利填充。應用固體觸媒的優勢，設計填充床反應器，進行連續式的轉酯化反應，反應後的產物直接與觸媒分離。探討醇油比、反應溫度、滯留時間對甲基酯產率造成的影響，發現Ca(C3H7O3)2/CaCO3觸媒重複使用性佳，但進料中含大量水分致使產率降低。使用微分反應器的假設，迴歸實驗數據，建立大豆油與甲醇的轉酯化反應速率動力式。

Biodiesel is an alternative fuel of diesel engine. The chemical structure of biodiesel is fatty acid ester. It can be produced by transesterification from triglyceride. Calcium oxide shows good catalytic activity in transesterification for biodiesel production, but the active surface sites of CaO are unavoidably poisoned by the atmospheric H2O and CO2. Previous studies reported that, Ca(C3H7O3)2 structure formed during transesterification by CaO and by-produced glycerol was tolerant to air-exposure and was reused without deactivation. In this research, Ca(C3H7O3)2/CaCO3 solid base catalyst was prepared. The advantage of Ca(C3H7O3)2/CaCO3 was that the particle surface was provided with Ca(C3H7O3)2 when the core remains CaCO3 to maintain the mechanical strength. Packed-bed reactor was used for continuous production of biodiesel. Reaction parameters including methanol to oil ratio, reaction temperature, residence time and reusability were discussed. Using the assumptions of differential reactor to determine the rate of reaction showed that Langmuir-Hinshelwood mechanism could be used to describe the rate equation.