Steam reforming model compounds of biomass gasification tars: conversion at different operating conditions and tendency towards coke formation

The purification of biomass-derived syngas via tar abatement by catalytic s team reforming has been investigated using benzene, toluene, naphthalene, a nthracene and pyrene as surrogated molecules. The effects of temperature an d steam-to-carbon ratio on conversion, and the tendency towards coke format ion were explored for each model compound. Two commercial nickel-based cata lysts, the UCI G90-C and the ICI 46-1, were evaluated. The five tar model c ompounds had very different reaction rates. Naphthalene was the most diffic ult compound to steam reform, with conversions from 0.008 g(org-conv)/g(cat ) min (790 degreesC) to 0.022 g(org-conv)/g(cat) min (890 degreesC) at an S IC ratio of 4.2. The most reactive compound was benzene, with a conversion of 1.1 g(org-conv)/g(cat) min at 780 degreesC and an SIC ratio of 4.3. The tendency towards coke formation grew as the molecular weight of the aromati c increased. The minimum SIC ratio for toluene was 2.5 at a catalyst temper ature of 725 degreesC, and for pyrene at 790 degreesC it was 8.4. In genera l, catalyst temperatures and SIC ratios need to be higher than for naphtha in order to prevent the formation of coke on the catalyst. (C) 2001 Elsevie r Science B.V. All rights reserved.