Synthesis and characterization of hydrophobic nickel catalyst supported on different oxides for continuous liquid phase catalytic exchange reaction

Abstract

Hydrophobic Ni catalysts supported on three metal oxides coated with PTFE namely Ni/SiO2/PTFE, Ni/Cr2O3/PTFE, and Ni/Al2O3/PTFE were used in liquid-phase catalytic exchange (LPCE) reactions to enrich hydrogen isotope and produce deuterium oxide (heavy water). Wet impregnation method was employed to prepare the Ni/SiO2, Ni/Cr2O3, and Ni/Al2O3 before PTFE coating. The as prepared catalysts were characterized using different characterization techniques and their performances were evaluated in LPCE reaction using a continuous reactor. The performance evaluation based on the D2O yield can be ranked as Ni/Al2O3/PTFE > Ni/Cr2O3/PTFE > Ni/SiO2/PTFE > Ni/PTFE. The catalysts’ performances are strongly associated with the crystallite size, particle size, hydrophobicity, surface area, pore size, and metal-support interaction. Since isotope exchange requires a dry catalyst surface, the catalyst’s hydrophobicity plays a crucial role. In addition, the catalyst support improves the LPCE reaction efficiency, as the most efficient catalyst, Ni/Al2O3/PTFE, yielded 1220 ppm D2O, compared to 520 ppm for the benchmark catalyst, Ni/PTFE. The characterization results reveal that Ni/Al2O3/PTFE outperformed the other catalysts due to its low crystallite size (D = 23.04 nm), high hydrophobicity (WCA = 139.23°), higher surface area (16.31 m2g−1), small pores (pore size = 6.18 nm), and lowest average Ni particle size (40.89 nm).