Synthesis Of Solid Acid Catalysts From Kaolin For Efficient Production Of Biodiesel From Shea Butter

ABSTRACT

This study reports synthesis of solidacid catalyst from cheaper raw materials for efficient biodiesel production. The dissertation consists of six main research section including: (1) Synthesis and characterization of ordered solidacid catalyst from kaolin; (2) Synthesis and characterization of hierarchical nanoporous HY zeolite from acid activated kaolin; (3) Synthesis of nanoporous HY zeolites from activated kaolin, a central composite design (CCD) optimization study; (4) Synthesis and application of hierarchical mesoporous HZSM-5 for biodiesel production; (5) Synthesis and characterization of sulfated HY zeolite (SHY) for biodiesel production; (6) Comparative pyrolysis kinetics study of biodiesel produced from Mesoporous ZSM-5 zeolites and Microporous ZSM-5. Towards synthesis of solidacid kaolinite, all the kaolinites peaks in the starting material disappeared after the thermal and acid activation. However, most of the crystalline peaks reappeared with greater intensities at the (0211) band after NaOH impregnation. Further, the crystallinity index calculated by weighted intensity ratio index (WIRI) at (0211) band showed superior crystallinity for the synthesized material than the starting kaolin. This work demonstrates that impregnation of NaOH on amorphous aluminosilicate is a novel route for synthesizing of crystalline solidacid.

The results hierarchical mesoporous HYzeolites synthesis indicated that aging time and crystallization time determine the hierarchical factor of the synthesized HY zeolite. Incorporation of appropriate amount of NaCl is also towards enhancing the textural properties. Further, this process was optimized by varying the aging and crystallization time as well as amount of NaOH solvent using CCD. All the process variables were found to be statistically significant for high crystallinity and SSA while only NaOH solvent is statistically significant for optimal hierarchy factor.

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In the quest for facile synthesis, more active solid acid, the produced zeolite in the last section was with sulfated groups. The effect of sulfate ions was observed on the textural and acidity properties as well as its catalytic activity. SHY gave biodiesel yield of 90.76% at 200 °C for 6 h while hierarchical HY gave yield of 72.42% at the same condition. This indicates that both pore structure and acid strength decide the activity of solid acids catalysts in biodiesel production.

Hierarchical mesoporous ZSM-5 (HMZeol) was also tested for biodiesel production. The catalysts synthesis was by desilication of conventional ZSM-5 with aqueous solution of NaOH (0.3 and 0.4 M). The sample treated with 0.4 M NaOH (0.4HMZeol) maximum biodiesel yield (82.12%) at 5:1 (methanol/oil) molar ratio, 1 wt % catalyst, and 3 h reaction time at 200 ᵒC. However, further increase in the parameters decreases the yield. Contrarily, 0.3HMZeol shows increase in yield with increase in operating parameters.

The pyrolysis kinetics of some biodiesel produced in section 5 and that of the shea butter were carried by thermal decomposition using TGA equipment. The average activation energy was computed based on best-fitted models. The reference ZSM-5 biodiesel exhibits lower EA (63.59 KJ/mol) compared to 0.3HMZeol and 0.4HMZeol biodiesel (66.69 and 72.98 KJ/mol respectively). This is attributed to higher acidity of the microporous zeolites used for ZBio. However, the reference ZSM-5 exhibited lower conversion due to steric hindrance.