Manganese oxide as catalyst for tar cleaning of biomass-derived gas

The possibilities to upgrade raw gas with the use of a manganese oxide have been investigated in an application for secondary tar cleaning of biomass-derived gas. Experiments were conducted in a reactor system where a novel technique that combines tar cleaning with catalyst regeneration is applied. Raw gas from the Chalmers non-catalytic steam biomass gasifier—containing roughly 32 gtar/Nmgas3—was fed to the tar cleaning reactor. The tar reforming qualities of the manganese oxide were evaluated in the reactor system using a mixture of 23 wt.% catalysts in silica sand at the temperatures 700 and 800°C. Experiments showed that the catalyst was continuously regenerated from carbon deposits and that the total amount of tars was decreased by as much as 44.5 % at a gas residence time of 0.4 s in the bed. The catalyst showed activity in water–gas shift reaction and the H2/CO ratio increased from 0.6 in the raw gas to a peak value of 1 in the reformed gas at 800°C. Only a slight decrease in methane and acetylene content was observed for both operating temperatures.