Synthesis and characterization of NiZn/mesoporous carbon as heterogeneous catalyst for carboxylation reaction of acetylene with CO₂

Utilization of fossil fuel, charcoal, oil, and natural gases, which are carbon-rich materials, is widely used for human sustainability. However, utilization of such materials contributes to higher atmospheric CO₂ concentration. The increase of CO₂ emission leads to higher temperature and climate change due to 'greenhouse effect'. Therefore, conversion of CO₂ to value-added chemicals has drawn many attentions. In this research, carboxylation reaction of acetylene and CO₂ has been carried out using mesoporous carbon modified by nickel and zinc metals as heterogeneous catalyst. Mesoporous carbon has been successfully synthesized using soft template method with pluronic F127 as template and phloroglucinol as carbon precursor. Mesoporous carbon was then modified with nickel and zinc (NiZn/MC) using homogeneous deposition precipitation method, followed by reduction for 90 min at 400 °C under a flow of H₂ (30 ml/min). XRD diffraction pattern showed peaks for 2θ around 31.79°, 34.54°, 36.31°, 44.04°, 51.51°, 56.51°, 62.22° and 75.68° which indicate the presence of NiZn and ZnO. EDX result revealed that mesoporous carbon material has been successfully modified by nickel and zinc metals, with 11.68 % and 8.69 % metal loadings for nickel and zinc, respectively. NiZn/MC catalyst was then used for carboxylation reaction of acetylene with CO₂. The reactions were carried out in batch reactor with varied pressures, 1.5 bar, 2.5 bar and 3.5 bar. Acrylic acid, as the desired product, was not observed in analysis with HPLC. However, more polar species was noticed at retention time of 3.15 min, where the optimum pressure was found to be at 2.5 bar.