Catalytic materials from inorganic side streams via alkali activation

Alkali activation is an alternative way to increase utilization of inorganic side streams and wastes in high-value product development. For catalysis it opens a new approach for the development of efficient materials.
Powdered catalysts in white cups
Powdered alkali-activated and solgel made vanadia catalysts ready for use.

Why are alternative raw materials needed for catalysis?

Roughly about 85 % of chemical production processes use catalysts in certain phases of production. Over 90 % of these catalysts are solid heterogeneous catalysts. Catalytic materials are used for speeding up the chemical reactions and lowering the energy required. The role of the catalysts is thus very important from economic and environmental points of view. Catalysts are also very important in several environmental technologies, such as catalytic converters of passenger cars, water purification processes and clean energy production, such as hydrogen production from water via photocatalysis.

The heterogeneous catalytic materials contain metals and metal oxides, of which a remarkable share is included in EU’s critical raw materials list. In addition, the catalysts very often contain expensive noble metals. Despite of these facts, the catalysts are needed for accelerating reactions all over the world. Due to these reasons, the researchers are continuously searching for new alternatives, which would consist of economic and abundant materials for the catalysts. Industrial by-products, inorganic waste materials and recycling open new possibilities for this purpose.

Alkali-activated materials for environmental applications

One possibility to make use of the wastes and by-products is alkali activation. This process is quite familiar in the production of construction materials, but it has found an application in catalyst preparation quite recently. Performance of geopolymers and alkali-activated materials have been studied quite widely in fine chemicals production. However, published information in environmental applications is less available, especially in the field of gas emission treatment. One of the complications of applying the alkali-activated materials in gas-phase reactions is their low surface area. Typically, over 100 m2/g specific surface areas are required for gas-phase catalysts, which is not inherently reached in, for example, geopolymerization. We have recently applied acid leaching to increase the specific surface area of geopolymer materials. Acid leaching removes aluminum from the geopolymer structure and partly destroys the polymeric structure, but increases the specific surface area markedly. These types of materials have been proposed for supports for catalysts for abatement and utilization of volatile organic compound emissions. In some cases of utilization of volatile organic compounds, the alkali-activated materials have proven to be even better than corresponding catalytic materials, shown by high product formation at lower temperature range. The recent results show the good properties of the material, comparable to typical catalyst supports used, and opens a way to utilize industrial by-products or inorganic waste materials in high-value end products.

The work is carried out in close collaboration between the Environmental and Chemical Engineering research unit and the Fiber and Particle Engineering research unit. The work is related to the Preventing environmental contamination thematic area of the InStreams Hub. The InStreams Hub is a cross-disciplinary research community at the University of Oulu focusing on inorganic circular economy.

M.Sc. (Eng.) Tiina Laitinen is a doctoral researcher in the Environmental and Chemical Engineering research unit. Her work focuses on the development of catalytic materials for utilization of volatile organic compounds. She has wide expertise on development and characterization of novel catalytic materials as well as evaluation of the materials’ performance indicators.

Docent Satu Ojala is a university researcher in the Environmental and Chemical Engineering research unit. She has long experience on environmental engineering, including material development and characterization, gas emission abatement and water purification. Her research interests include in situ and operando characterization of catalytic materials and phenomena as well as utilization of organic and inorganic wastes in environmental applications.