Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes
and causes fouling of system components and pipework. Therefore, an efficient tar conversion in
the product gas is a key step of effective and reliable syngas production. One of the most promising
approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The
catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 C
downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar
conversion was developed and characterized in detail. An appropriate composition of transition
metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two
of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system
used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter
material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion
above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt
... mehr
and impregnated on a ceramic fiber filter composed of Al2O3(44%)/SiO2(56%), was the most active
catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene
conversion of around 93% over 95 h without catalyst deactivation.