Tar removal on dolomite and steam reforming catalyst: Benzene, toluene and xylene reforming

Tar removal performance of dolomite and commercial precious metal based steam reforming catalyst have been investigated by using the surrogated compounds of tar, namely benzene, toluene and xylene at changing tar loads and temperatures. Hydro- and steam dealkylation of alkyl aromatic hydrocarbons have been observed on dolomite and precious metal based catalyst. Gaseous products like H2 and CO2, started to be measured at 563 °C, and detection of benzene and toluene in case of xylene reforming proved the presence of selective reforming reaction on alkyl groups. Total steam reforming of aromatic rings has not been observed as sub-stoichiometric formation of reforming products meaning that selective steam reforming was only applied onto the alkyl groups of aromatics. Steam dealkylation reaction favorably occurred at 500–600 °C whereas thermal degradation and/or polymerization of aromatic compounds became the prevailing reaction with increasing the operation temperatures beyond 700 °C. Tar conversion was found to be independent on inlet tar load unless excess steam was present. Co-existence of tar and methane seemed beneficial as proved by enhanced methane reforming activity and complete tar removal. This improvement has been explained by the polymerization reaction of tar compounds and formation of unmeasurable soot particles.