Influence of ethylene on the formation of mixed alcohols over a MoS₂ catalyst using biomass-derived synthesis gas

Since 2011, a pilot plant for the production of mixed alcohols (MAs) from biomass-derived synthesis gas has been in operation. The pilot plant uses synthesis gas provided by a biomass-based combined heat and power plant (CHP) in Güssing, in which the fixed bed reactor is filled with a sulfidized molybdenum catalyst (MoS₂). The advantage of a sulfidized catalyst is resistance to sulfur components. Sulfur resistance significantly lowers the operating costs of such a plant. The main parts of the mixed alcohol synthesis plant in Güssing are a steam reforming unit, a glycol scrubber, a compression step, a fixed bed reactor for the synthesis itself, a condensation vessel for the separation of alcohols from the gas stream, and an expansion valve. The main aim of this project in the last year was to perform parameter variation to investigate the optimal operation point of the plant and to use these parameters to conduct long-time trials over several days. Parameter variation showed the impact of reaction temperature, pressure, and space velocity on product yield and distribution. The influence of the gas composition on the product distribution and side products was also investigated. This study was dedicated to investigating the influence of the ethylene content in the synthesis gas on the formation of propanol and ethyl mercaptan (C₂H₆S). During the experiments, several liters of MAs were produced. The alcohols consisted mainly of alcohols from carbon numbers between one and three. One of the main results of the first experiments was that the ethylene content in the synthesis gas has a high impact on the product distribution and is also responsible for side reactions to sulfur components.