CO₂-Syn: Utilizing CO₂ emissions from the cement industry as a raw material

The aim of the project partners is the sustainable use of CO₂-containing waste gases from the cement industry. Specifically, a novel process chain is to be created to enable the synthesis of olefins and higher alcohols from carbon dioxide process gases. The solution adopted is called "power-to-chemicals”. This involves using renewable energies such as wind power to convert CO₂ and water into carbon monoxide and hydrogen via electrolysis. Mixtures of these two substances – known as synthesis gases – are then used to produce the desired chemical products by means of further catalytic conversion processes.

Since the CO₂ released by the cement plants has to be elaborately purified and conditioned for further processing, one focus of the project is on the development of new catalyst materials. Specifically, the researchers are working with sulfide-, nitride- and phosphide-based materials. They are very stable to typical catalyst poisons such as sulfur, but have not yet been systematically investigated as potential catalysts for synthesis gas production from CO₂ or for subsequent synthesis gas conversion to olefins and higher alcohols.

In the cement industry, carbon dioxide is an unavoidable by-product: It is formed when calcium carbonate is burned to calcium oxide and is subsequently released. With global production of four billion metric tons of cement, the industry is currently responsible for around four to eight percent of global CO₂ emissions. The production of one metric ton of cement clinker, for example, emits around 0.8 tonnes of CO₂.

To reduce these emissions, various measures are currently being implemented to increase energy efficiency and replace fossil fuels with alternative fuels. Efforts are also being made to reduce the proportion of cement clinker – and thus of calcium oxide – in the cement by using other materials. Another option that has hardly been considered so far is Carbon Capture and Utilization (CCU) – that is, the capture and utilization of CO₂ as a raw material for the production of valuable chemical products such as basic chemicals, fuels, fertilizers or plastics. One solution for CCU is the “power-to-chemicals” concept envisaged in the CO₂-Syn project. 

In April 2023, the project partners drew a positive interim balance: Among other things, they succeeded in identifying promising catalysts for the conversion of carbon dioxide released by cement plants and preparing their testing under real conditions.

The researchers from the Leuchtstoffwerk and the Ruhr-Universität Bochum were able to synthesize more than 20 potential catalysts and make them available to Fraunhofer UMSICHT. Initial tests have already been carried out there and promising samples identified. Now the catalyst tests for the synthesis gas conversion to olefins and higher alcohols will begin under process conditions close to the application.

In parallel, a comprehensive analysis of the site took place at the Phoenix cement plant. This forms the basis for the experimental and systemic consideration of the electrocatalytic and thermocatalytic processes. This includes both experimental investigations on the influence of the gas matrix in the catalytic processes and considerations on the integration of the process chain of electrolysis and thermocatalysis into the plant network of the cement plant.

• Ruhr-Universität Bochum
• Leuchtstoffwerk Breitungen GmbH
• Phoenix Zementwerke Krogbeumker GmbH & Co.KG

The project "CO₂-Syn – Material CO₂ utilization from cement plant process gases with coupled electrochemical and thermally catalyzed processes" is funded under the funding measure "Application-oriented non-nuclear R&D in the 7th Energy Framework Research Program of the Federal Government" in the funding area "Technologies of CO₂-circular economy" of the Federal Ministry of Economics and Climate.