Thermocatalytic conversion of palm oil over carbonate salts into renewable hydrocarbons: Pyrolysis kinetics study and comprehensive characterization for product selectivity analysis

This study evaluated the application of low-cost carbonate salts (Na 2 CO 3 , CaCO 3 , and K 2 CO 3 ) as reaction-promoting additives in the thermocatalytic cracking of palm oil to produce renewable hydrocarbons. Thermogravimetric and chemical characterization analyses showed that, at temperatures below 400 °C, the salts promoted saponification pathways, converting triglycerides into fatty acid salts, which subsequently degraded into volatile compounds above 450 °C. Kinetic analysis indicated that the additive salts also act as catalysts, reducing the average activation energy from 147.86 kJ mol –1 for the non-catalytic process to 140.23 kJ mol –1 (Na 2 CO 3 ), 125.33 kJ mol –1 (CaCO 3 ), and 106.51 kJ mol –1 (K 2 CO 3 ). Bio-oil characterization revealed increased formation of olefinic and paraffinic hydrocarbons (C 7 –C 15 ), with a significant reduction in fatty acids, especially in the process using K 2 CO 3 , which yielded bio-oils containing approximately 50% of hydrocarbons. The additive salts also promoted deoxygenation reactions, reducing compounds with 4 to 6 oxygen atoms per molecule and generating less oxygenated fractions with lower molecular mass and higher unsaturation. Among the tested salts, K 2 CO 3 demonstrated the highest efficiency in reducing activation energy and improving the compositional quality of the bio-oils, highlighting its superior potential for producing renewable hydrocarbons from palm oil.