Credit: © 2008 ACS

In biomass gasification, carbonaceous materials react with controlled amounts of gas at high temperatures to generate energy. A nasty by-product, which clogs up the equipment, is the black viscous liquid known as tar. Various forms of nickel-based catalysts have been used to remove tar with efficiencies of up to 95%, but for commercial applications cheaper and more effective catalysts are needed. Researchers at the Wuhan Polytechnic University, Huazhong University and Nanyang Technological University now report tar removal efficiencies of 99% using nanoparticles of nickel oxide as a catalyst1.

Rong Yan and colleagues used the well-known deposition–precipitation method to prepare the alumina-supported nickel oxide catalysts. The catalysts are spherical, about 12–18 nm in diameter, and have an eggshell structure, with nickel oxide particles coating the outside of the alumina core. When compared with commercially available nickel-based catalysts, the nanoparticles removed tar more efficiently at higher temperatures. In addition, the process increased the generation of valuable gases such as hydrogen and carbon monoxide gas, whilst lowering the production of unwanted hydrocarbons like methane. It was suggested that the nanoparticle catalyst enhanced the cracking of tar by keeping the vapour in the catalytic bed for longer.

Further studies on the lifetime of the catalyst and the reaction mechanism are needed, but the present material promises to remove tar efficiently while improving the quality of the gaseous by-products.