Higher Alcohols Synthesis: Experimental and Process Parameters Study over a CNH-Supported KCoRhMo Catalyst

The present work investigated the effects of operating conditions (temperature (<i>T</i>), pressure (<i>P</i>), and gas hourly space velocity (GHSV)) on the higher-alcohols synthesis reaction, using a downward-flow fixed-bed reactor. The carbon nanohorn (CNH)-supported KCoRhMo catalysts with compositions of 9% K, 4.5% Co, 1.5% Rh, and 15 wt % Mo were used for this study. The Design Expert software was used to analyze the interaction effects of <i>T</i> (290–370 °C), <i>P</i> (800–1400 psig), and GHSV (2.4–4.8 m³(STP)/kg_cat/h) on CO conversion, alcohols, and hydrocarbon product selectivities, as well as their respective yields. The validity of the models was assessed by statistical tests: test of significance and coefficient of determination (<i>R</i>²) values. The recorded <i>R</i>² values suggested that the quadratic models generated could sufficiently depict the experimental data. Increasing temperature and pressure in the ranges of 290–350 °C and 800–1400 psig, respectively, resulted in corresponding increases in CO conversions; however, with increasing GHSV, the CO conversion decreased monotonically. Numerical optimization assessments of the models selected the optimum operating conditions to be 325 °C, 1320 psig, and 2.4 m³(STP)/kg_cat/h to give the maximum ethanol and higher alcohols space time yields of 0.126 and 0.177 g/g_cat/h, respectively