INVESTIGATION OF NICKEL SUPPORTED ON ZEOLITE CATALYST IN THE HYDROTHERMAL CATALYTIC DEOXYGENATION OF PALMITIC ACID: APPLICATION OF RSM DESIGN FOR OPTIMIZATION

ABSTRACT

Fatty acid and its derivatives have been considered to be a promising precursor for the production of biodiesel and jet-fuel range of hydrocarbons. This study aims to investigate the efficiency of nickel supported on zeolite (ZSM-5) catalyst in a hydrothermal condition to obtain hydrocarbons within the diesel and jet-fuel range from palmitic acid with no external supply of hydrogen gas. The method employed in this study was the hydrothermal catalytic deoxygenation of Palmitic Acid over Ni/ZSM-5 catalyst. The catalyst was synthesized through wet impregnation of Ni on ZSM-5. An RSM model was used to obtain factorial variables of metal loading and temperature to give maximum paraffin yield and PA Conversion. The reaction was carried out in a batch reactor loaded with a calculated amount of the palmitic acid, the catalyst and water in its supercritical state, and allowed to run for a batch time of 3hrs. 0.5g metal loading (10% – 50%) and reaction temperature (250°C to 300°C) were varied for each run while the quantity of water remained 4mL for every run. Results obtained show that PA conversion and paraffin yield show positive relationship with metal loading. As metal loading increased from (0% to 20%), PA conversion and paraffin yield also increased from (6.6% to 96%) and (0.07% to 66%) respectively. Side reactions that led to the formation of palmitone also reduced with increased metal loading. Also, results obtained show that as the temperature of the reactions increase from (250°C to 300°C) the PA conversion and paraffin yield increase from (5.2% to 97.2%) and (2.8% to 60.5%) respectively. It was also observed from the results obtained that presence of water greatly improved the conversion of PA and paraffin yield (17.2 to 66.8%) and (1.8% to 35.5%) respectively when compared to the run carried out without water which had a PA conversion and paraffin yield of (<20%) and (<10%) respectively. Significant improvement was attributed to the formation of in-situ H2. The presence of water also suppressed the side reactions leading to the formation of palmitone and palmitate. It was v concluded that, compared to decarboxylation and hydrodeoxygenation, decarbonylaation was the major path for hydrothermal deoxygenation of PA catalyzed by Ni/ZSM-5