Size-dependent Kinetics Determination of MoS2-K2O/CNTS Nanocatalyst in the Synthesis of Alcohols from Syngas

Abstract

The influence of Mo particle size on the catalytic activity and product selectivity of alkalized MoS2 nanocatalysts has been investigated. Nanocatalysts are prepared using a microemulsion technique with water-to-surfactant ratios of 1-12. Three different techniques, including XRD, TEM, and hydrogen chemisorption were used to determine the molybdenum average particle size and their activity and selectivity in higher alcohols synthesis (HAS) carried out in a fixed bed microreactor at 330 °C and 70 bar. To fix the percentage of CO conversion, the GHSV is changed from 3.6 to 2.57 (nl/(hr.g catalyst)). The average MoS2 particle sizes are changed from 4.5 to 11.9 nm. The experimental results showed that changing particle size from 11.9 to 4.5 nm decreased the methanol formation rate from 0.00634 to 0.00534 (mol/(hr.g catalyst)) but increased ethanol formation rate from 0.00581 to 0.00787 (mol/(hr.g catalyst)) and higher alcohols formation rate from 0.00473 to 0.00657 (mol/(hr.g catalyst)). A size-dependent kinetics model was developed to calculate the alcohol formation rates versus catalyst average particle size. The model not only matched experimental and theoretical results, but also showed that MoS2 catalyst had size-dependent structure and for the prediction of product selectivity it was easier to use this mathematical model.