Synthesis and characterization of K₂CO₃ over Salmon-fishbone catalyst, kinetics and DFT analyses and biodiesel catalytic production from castor oil

A cost-effective and recyclable catalyst, K2CO3 supported on calcined salmon fish bone (K2CO3/SFB), was synthesized using an ultrasonic-assisted wet impregnation method. Various characterization techniques, including XRD, XPS, BET, FESEM, TGA, and FT-IR, were used to analyze the prepared catalysts. The catalytic efficiency of the sonicated K2CO3/SFB catalysts was evaluated in the transesterification reaction between Castor oil and methanol to produce biodiesel. The study also investigated the impact of calcination temperature and K2CO3 loading on the catalyst's performance, revealing that the highest catalytic activity was achieved with K2CO3 calcined at 773 K with a loading of 20 wt%. Optimized conditions for biodiesel production included a loading of catalyst at 10 wt%, a mol proportioan of 10 to 1 for methanol/oil, and a reaction temperature set at 338 K over a period of 2 h, resulting in a process yield of 99.63 %. The catalyst exhibited good stability over six reaction cycles, with only an 8 % decrease in activity. The kinetics studies were investigated with PLS-R, assuming fatty acid methyl esters as the main product and mono- and diglycerides as intermediate and established 95 % confidence intervals and found a rate constant of 1.05 h(-1) for the reaction and an energy required for activation. of 18.72 kJ/mol with the optimized catalyst. Additionally, DFT-D3 calculations showed strong interaction between the catalyst and triglyceride, with charge transfer enhancing the reaction rate, and p orbitals from the catalyst playing a significant role in hybridization with triglyceride's carbon and oxygen atoms.