The Study on the Preparation of Trisodium phosphate-impregnated on Bottom Ash using Wet Impregnation Method for the Use as the Catalysts in Biodiesel Production

Abstract

This work aimed to study the preparation of trisodium phosphate impregnated on bottom ash using wet impregnation method for use as the catalyst in transesterification reaction. Both coal bottom ash and trisodium phosphate were wastes or by-products from the combustion and Thai monazite ore separation, respectively. The catalyst was characterized using BET, CO2-TPD, XRD, and XRF techniques. The results from XRD showed that coal bottom ash consisted of quartz and mullite (mostly Si and Al). The various synthesis conditions were investigated such as trisodium phosphate (TSP) loadings, impregnation temperatures, and calcination temperatures. TSP loadings were varied at 10, 20, 30 and 40 wt%. The impregnation temperatures were carried out at room temperature (25 °C), 40, 60 and 80 °C, and the calcination temperatures were studied at 150, 250, 350 and 450 °C. The results showed that the highest %FAME of 90.26% was observed when using the catalyst which was impregnated using TSP loading of 40% at the impregnation temperature of 60 °C and the calcinations temperature of 350 °C. The %FAME strongly depended on the basicity of catalyst. Higher basicity of catalyst provided more activities of catalyst in transesterification reaction. In addition, the Box-Behnken experimental design was used in this work to study the interaction between variables and responses. The trend of %FAME result using Box-Behnken corresponded to the results from the study of various conditions mentioned previously. The optimum conditions of catalyst synthesis were observed using Minitab optimizer, which were TSP loading of 40 wt%, impregnation temperature of 80 °C and calcination temperature of 278 °C.

Furthermore, the suitable ratio of methanol to oil and the reusability were studied. The suitable ratio of methanol to oil was 18:1. After the reaction, the catalyst was washed with methanol several times to reuse in the transesterification reaction. It showed that the reusability of catalyst was not observed due to the loss of active sites and the deactivation of the catalyst.

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