فهرست نشریات علمی دسترسی آزاد ایران

Due to their low cost, clays can be used as promising catalysts in industries. So, this study used five various clays with different elemental compositions and structures as catalyst bases for the esterification process. The clays were activated with sulfuric acid and characterized using XRD, TGA, BET-BJH, FESEM, EDS, mapping, and TPD-NH3 analyses. The results showed that the clays have a quartz base structure, with three containing a kaolinite phase and the other two containing albite. Minerals with kaolinite had higher surface area and larger pore volumes, and their structure was sheet-like. In contrast, albite minerals with a dense and granular structure exhibited lower activity in the esterification reaction. Among the samples containing kaolinite, the sample with a higher Si to Al ratio exhibited higher activity (93.8%) in the esterification reaction. However, a significant decrease in catalyst activity was observed after one cycle of use (reduced the conversion to 59.1%). Therefore, the synthesis method of the acidic catalyst was modified, although initially showing lower activity (75.6%) due to a low percentage of surface acid groups, it preserved its activity and demonstrated a very slight decrease (less than 4%) after the third use. The proper interaction and distribution of acidic groups on the surface with appropriate bonding and ion exchange in the clay base were the main factors in increasing the stability of this catalyst. The result shows that clay can be a potential, and cost-effective catalyst source for chemical reactions and presents a facile and practical method for producing biodiesel in large-scale operation.