A catalytic/sorption hybrid process for landfill gas cleanup

Landfill gas (LFG) consists primarily of methane and carbon dioxide and a few percent of O-2, N-2, and H2O. It also contains numerous other organic compounds, many containing halogens and sulfur. Such compounds besides being potentially toxic to human, animal, and plant life, in addition present challenges to the further processing of LFG. For example, halogen-and sulfur-containing compounds in LFG severely impact the life of reforming catalysts used to produce H-2, to be utilized in a fuel cell for the production of electric energy. For such processing, it is important to reduce the concentration of such compounds from the level of tens to hundreds of parts per million, typically found in LFG, down to the single-digit parts per million and, most preferably, parts per billion level. Effective processes to accomplish this are not currently available. This paper describes the development of such a process, which is well-suited to fuel-cell applications of LFG. The process combines catalytic hydroprocessing, utilizing Co-Mol Al2O3 or Ni-Mo/Al2O3 catalysts in an atmospheric pressure reactor, together with sorption technology, utilizing disposable adsorbents, for the removal of HCl and H2S produced during the catalytic treatment. In laboratory, and field investigations the process has been shown to be very effective in removing the S- and Cl-containing organic compounds, for the most part down to their analytical detection limits. In companion field tests, no significant catalyst deactivation was observed during over 1000 h of testing.