(654a) Preparation of Heterogeneous Catalyst for Biodiesel Synthesis

Increasing biodiesel consumption requires optimized production processes allowing high production capacities, simplified operations, high yields, and the absence of special chemical requirements and waste streams. The utilization of a successful heterogeneous catalyst will cope with most of the economical and environmental drawbacks of a homogeneous process. In conventional homogeneous method, removal of catalysts after reaction is technically difficult and, a large amount of wastewater was produced to separate and clean the catalyst and the products. The heterogeneous catalyst is rapidly separated from the reaction mixture by filtration without requiring the use of a solvent, show easy regeneration, and has a less corrosive character, leading to safer, cheaper and more environment-friendly operation. Nowadays only one industrial application, developed by the IFP, uses heterogeneous base catalysts for the transesterification of vegetable oils to produce biodiesel. The French Institute of Petroleum (IFP) has announced the construction of a 160,000 t/yr biodiesel plant that is based on the use of an heterogeneous catalyst. The Esterfip-H process involving a heterogeneous solid catalyst consisted of a mixed oxide of Zn and Al with a spinel structure. The reaction is performed at higher temperature and pressure than homogeneous catalysis processes, with an excess of methanol. In this study a new type of heterogeneous catalyst for FAME synthesis was prepared using sol-gel method. The active component of catalyst is Zn or K and alumina and silica or pure alumina are the catalyst support. Catalyst was prepared using one step sol-gel procedure using aluminium-sec butoxide and tetra-oxi-orto-silane in 1-buthanol as solvent. Geling of this mixture was realized using different salts of Zn and K. Obtained gels with Zn and K as active metals was dryed for preparation corresponding aerogels (drying in supercritical CO2) or at normal pressure and elevated temperature for obtaining xerogel. The influence of different parameters for preparing aerogel and xerogel catalyst was investigated (temperature and duration of drying for obtaining xerogel; ratio of Al and Si in the final gel; amount of active metals). All the necesary catalyst characteristics were determined using different instrumental techniques (X-Ray, pore size distribution, mercury porosimetry, AAS; TG and DSC). Catalyst testing was performed at elevated temperature and pressure using different ratio of metahnol and vegetable oil. The analysis of reaction product (FAME and glycerol) was performed using GC (FID detectors) with mgabohrs capillary column designed for analysis of heavy hydrocarbons at high temperature. The yield of FAME was analysed for different time of methanolysis performed in a batch reactor and corresponding kinetic parameters (reaction rate constants and order) determined.