Newswise — RUDN chemists have created activated carbon catalysts for the production of higher alcohols from syngas. The researchers described how the microstructure of activated carbon affects the efficiency and other parameters of catalysis. The results are published in ACS Omega
A mixture of carbon monoxide (carbon monoxide) and hydrogen is called syngas in chemistry. It is the product of the first stage in the conversion of biomass and natural gas into desired products. It is from syngas that liquid fuels are obtained, including higher alcohols – alcohols with more than two carbon atoms. However, catalysts are required for its production. One promising approach is to use activated carbon. This porous material can become a base that absorbs substances like a sponge and increases the efficiency of the reaction. RUDN chemists have created several new catalysts based on activated carbon and auxiliary elements.
“The production of higher alcohols from syngas is an economically attractive method for producing chemicals and fuels. The activity of catalysts supported on carbonaceous materials is greater than that of catalysts based, for example, on metal oxides. In the chemical industry, activated carbon is widely used as a catalyst carrier due to its specific properties – high stability at high pressures and temperatures, large surface area and porosity, resistance to acidic and alkaline conditions, minimal interaction with the active substance” , Tatiana Sheshko, Ph.D, associate professor of RUDN University Adsorption and Catalysis Laboratories said.
Chemists have used several types of activated carbon – in the form of powder and fibers. Based on this, RUDN researchers created catalysts with potassium, cobalt and molybdenum. To fill the carbon base with the right elements, the chemists used cobalt acetate, potassium hydroxide and ammonium heptamolybdate. After that, the future catalyst was dried for 7 hours at a temperature of 80-100 ohC. A total of four types of catalysts were obtained from four types of charcoal.
Then, new compounds were tested for catalysis in the reaction to obtain alcohols from synthesis gas. For each type of catalyst, the experiment lasted 16 hours. The temperature in the reactor was increased by 20 ohC every 4 hours. The composition of the products obtained was checked at the same frequency.
All catalysts showed different results, which is explained by different microstructure – pore size and number, surface area, etc. The most effective catalyst was the obtained compound based on fibrous activated carbon – at a temperature of 360 ohC, almost 50% of the original carbon monoxide transformed into the target product. Powdered carbon catalysts have shown greater selectivity – the ability to selectively accelerate the production of a particular product. RUDN chemists also discovered an unusual pattern – substances with larger pores were not more active, but vice versa.
“We studied powders and fibers activated carbons with different textural characteristics as catalyst supports for the production of alcohols from syngas. An unusual correlation was found between porosity and catalytic activity. The microporous powder complex was found to be more active than the complex with larger pores,” said Mohamed Osman, postgraduate student at RUDN University.