INFLUENCE OF LA_2O_3 ADDITION ON COKE RESISTANCE AND REGENERATION OF NI/OLIVINE CATALYST IN STEAM REFORMING OF BENZENE

摘要

The gasification of biomass provides a competitive means of obtaining a clean, hydrogen rich gas for energy and chemicals production. Its industrial feasibility depends mainly on the tar elimination technologies. Tar catalytic reforming is a process to covert the condensable tar into permanent gases at the typical temperatures of 650～900℃. This involves oxidation of the tar components using steam to produce hydrogen and carbon oxides. It has the advantages over a simple scrubbing operation of increasing the gas yield and the overall efficiency of the biomass thermochemical conversion process. Ni-based catalysts are the most common used catalysts in steam reforming of methane and naphtha for its cheapness and high activity. However most of commercial reforming nickel catalysts display a rapid deactivation due to the build-up of surface carbon. These catalysts, which have been essentially designed for paraffinic hydrocarbons reforming, are not well suited for the molecular structures present in tar compounds and heavy feedstocks [1]. Many researchers are therefore devoting to develop novel catalyst formulations to optimize desired catalyst properties [2]. Courson et al. [3] prepared a nickel catalyst supported on olivine calcined at 1100℃. They reported that this catalyst is stable with its strong nickel-olivine interaction, and very active for dry and steam reforming of methane. In our previous study, we tested Ni-olivine catalyst in the steam reforming of benzene [4]. The catalyst was deactivated quickly and lost more than 50% of its initial activity within 20 minutes of treatment. It is possible to improve the anti-deactivation of the catalyst by incorporating oxide of basic rare earth. Present paper deals with the performances of La_2O_3 promoted Ni-olivine catalyst with the aim of reducing the coke formation as well as retrieving activity through regeneration. Benzene was chosen as the model compound because it is the main constituent of tar and also it represents a stable aromatic structure for tar molecules [5].