Synthesis, Characterization and Catalytic Evaluation of Sonicated Nickel-based Catalysts for 1,3-Propanediol Production via Aqueous Phase Glycerol Reforming

Aqueous phase reforming (APR) is one of the most promising technologies for converting glycerol into 1,3-propanediol (1,3-PDO). The utilization of the noble metal catalyst for APR reaction had some drawbacks due to higher price and not easily available. Thus, Ni- based catalyst has attract much attention but this catalyst has a low thermal stability which can deactivate at high temperature. Besides that, previous studies also reported that the conventionally synthesized catalysts are highly agglomerated due to the uneven distribution of metals. To overcome these problems, sonochemical method was introduced during the preparation of Ni based catalysts and doped with Ca to improve the physicochemical properties towards high activity in APR of glycerol. To achieve the objective of study, 10%Ni-x%Ca/TiO2, 10%Ni-x%Ca/CeO2 and 10%Ni-x%Ca/ZrO2 catalysts (x= 0, 0.5, 3 and 5) were synthesized via sonochemical and wet impregnation methods (as benchmark). All the catalysts were subjected to various characterization techniques to observe the effect of ultrasound irradiation on the physicochemical properties of the catalysts. The performance of the catalysts was evaluated for APR of glycerol to 1,3-propanediol (1,3-PDO) at 230℃, 20 bar, 450 rpm for 1 h. The best catalyst with the highest yield and selectivity of 1,3-PDO was selected and further utilized for optimization study. The optimization study was carried out using experimental work and Response Surface Methodology (RSM) at varied temperatures (200 to 230℃) and pressure (10 to 30 bar), while the other parameters were kept constant. For this optimization study, only temperature and pressure were selected to be optimized because most of the literature reported that temperature and pressure had the most significant effect on the distribution of the products. The analysis showed that the ultrasound irradiation significantly improved the physicochemical properties and surface characteristics of the catalysts. Sonochemical catalysts have smaller particle sizes, leading to larger surface area and more active sites for the reaction to occur than wet impregnation catalysts.