Investigation of the influence of the catalyst in the process of producing biodiesel using supercritical methanol

Abstract

The article discusses various ways to produce biodiesel fuel: in the presence of homogeneous catalysts, in the presence of heterogeneous catalysts, in supercritical methanol. There was experimentally confirmed that the process of obtaining methyl ethers of fatty acids (FAME) in the supercritical methanol on the selectivity, on replacement of the target product and process stability in time can compete with catalytic methods. There was studied the efficiency of the catalyst at the transesterification of rapeseed oil in supercritical methanol under the following process parameters: temperature of 300°C, the pressure of 300 atmospheres, the volume fraction of oil 0,5. There was evaluated that during the first hours after the filing of the reagents into the reactor in the presence of a catalyst TiO2/Ti concentration FAME in the oil layer of the reaction products is more than in not catalysed reaction. However, approximately one hour after the beginning of the process of catalytic activity was sharply reduced, and the output of the FAME becomes less, than without a catalyst. By means of mass-spectral analysis of the product, extracted from the surface of the catalyst, it is discovered a tumor in the process of interesterification low-volatile and poorly soluble substances, blocking the active centres of the catalyst. In addition, the reduction in catalytic activity became the result of partial destruction of the surface layer of TiO2. It is established, that the washing of the spent catalyst mixture of solvents with the subsequent heating at 350°C allows largely to restore the activity of the catalyst.