A KINETIC-MODEL FOR THE SYNTHESIS OF HIGH-MOLECULAR-WEIGHT ALCOHOLS OVER A SULFIDED CO-K-MO C CATALYST/

A statistically designed set of experiments was run in a recycle react or to evaluate the kinetics of the formation of higher-molecular-weigh t alcohols (higher alcohols) and total hydrocarbon byproducts from syn thesis gas (hydrogen and carbon monoxide) in a range of experimental c onditions that mirrors the limits of commercial production. The alkali -promoted, C-supported Co-Mo sulfide catalyst that was employed in thi s study is well known for its sulfur resistance. The reaction was carr ied out in a gradientless Berty-type recycle reactor. A two-level frac tional-factorial set consisting of 16 experiments was performed. Five independent variables were selected for this study, namely, temperatur e, partial pressure of carbon monoxide, partial pressure of hydrogen, partial pressure of inerts, and methanol concentration in the feed. Th e major oxygenated products were linear alcohols up to n-butanol, but alcohols of higher carbon number were also detected, and analysis of t he liquid product revealed the presence of trace amounts of ethers als o. Yields of hydrocarbons were non-negligible. The alcohol product fol lowed an Anderson-Schultz-Flory distribution. From the results of the factorial experiments, a preliminary power-law model was developed, an d the statistically significant variables in the rate expression for t he production of each alcohol were found. Based on the results of the power-law models, rate expressions of the Langmuir-Hinshelwood type we re fitted. The observed kinetics are consistent with the rate-limiting step for the production of each higher alcohol being a surface reacti on of the alcohol of next-lower carbon number. All other steps, includ ing CO-insertion, H-2-cleavage, and hydrogenation steps, do not appear to affect the rate correlations.