Design and evaluation of a sustainable catalyst for biodiesel production

Thesis Abstract

The increasing global demand for sustainable and environmentally friendly energy sources has intensified interest in biodiesel production, yet the reliance on conventional catalysts—primarily homogeneous alkaline catalysts—poses significant challenges related to catalyst recovery, environmental pollution, and high production costs. Addressing these issues requires the development of innovative, sustainable catalytic systems that are efficient, recyclable, and environmentally benign. This study aims to design, synthesize, and evaluate a novel bio-based heterogeneous catalyst derived from agricultural waste materials for application in biodiesel production through transesterification of vegetable oils. Specifically, the objectives are to (1) synthesize a bio-silicate catalyst doped with transition metal oxides from rice husk ash, (2) characterize the catalyst using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area analysis, and X-ray Diffraction (XRD), and (3) assess the catalyst’s performance in biodiesel synthesis from refined soybean oil under various operational parameters. Methodologically, the research adopts a mixed-methods approach comprising experimental design and analytical evaluation. The catalyst synthesis involves calcination of rice husk ash at varying temperatures to optimize surface properties, followed by impregnation with transition metal nitrates, notably calcium or magnesium, using wet impregnation techniques. A factorial experimental design will be employed with three key parameters—catalyst loading, methanol-to-oil molar ratio, and reaction temperature—each tested at three levels to determine optimal conditions. The study population includes 150 experimental runs based on the design, with a control using commercially available alkaline catalyst for comparative analysis. Data collection instruments encompass gas chromatography-mass spectrometry (GC-MS) for biodiesel yield and purity assessment, coupled with the aforementioned characterization techniques. Catalyst stability and reusability will be evaluated through five consecutive reaction cycles, and data will be analyzed via Analysis of Variance (ANOVA), response surface methodology (RSM), and regression analysis to determine statistical significance and optimize operational conditions. Expected findings suggest that the bio-silicate catalyst doped with transition metals will exhibit superior catalytic activity, higher biodiesel yields (anticipated to exceed 95%), and enhanced recyclability compared to conventional catalysts. The catalyst's high surface area, porosity, and active site density are projected to facilitate efficient transesterification at lower reaction temperatures and with reduced catalyst loadings, thus aligning with principles of green chemistry and sustainability. Additionally, the study will elucidate the relationship between catalyst physicochemical properties and biodiesel yield, contributing to the theoretical understanding of bio-based catalysts in renewable energy applications. This research is anticipated to make a significant contribution to knowledge by providing a sustainable, cost-effective alternative to conventional catalysts derived from easily accessible agricultural waste materials, thereby promoting circular economy principles within the biofuel sector. The findings will inform industry practices on catalyst design and application, emphasizing environmental benefits and economic viability. The main conclusion underscores the potential of agriculturally derived bio-silicate catalysts in advancing sustainable biodiesel production, with recommendations emphasizing further scale-up studies, lifecycle assessment, and integration into current biodiesel manufacturing processes for commercial application.