CO2 Conversion into Methanol Using Granular Silicon Carbide (α6H-SiC): A Comparative Evaluation of 355 nm Laser and Xenon Mercury Broad Band Radiation Sources

Abstract

Granular silicon carbide (α6H-SiC) was investigated as a photo-reduction catalyst for CO2 conversion into methanol using a 355 nm laser from the third harmonic of pulsed Nd:YAG laser and 500 W collimated xenon mercury (XeHg) broad band lamp. The reaction cell was filled with distilled water, α6H-SiC granules and pressurized with CO2 gas at 50 psi. Maximum molar concentration of methanol achieved was 1.25 and 0.375 mmol/l and the photonic efficiencies of CO2 conversion into methanol achieved were 1.95 and 1.16 % using the laser and the XeHg lamp respectively. The selectivity of methanol produced using the laser irradiation was 100 % as compared to about 50 % with the XeHg lamp irradiation. The band gap energy of silicon carbide was estimated to be 3.17 eV and XRD demonstrated that it is a highly crystalline material. This study demonstrated that commercially available granular silicon carbide is a promising photo-reduction catalyst for CO2 into methanol. Gas Chromatograms of reaction products collected at 30–120 min irradiation in the presence of 355 nm laser having 40 mJ/pulse energy. The inset shows the comparison of retention time of GC peaks with the methanol standard and it is at 2.46 min.