Oxidation Catalyst Performance Considerations: Catalyst Temperature, Space Velocity, and Fouling
Installation of oxidation catalysts for reduction of carbon monoxide (CO), formaldehyde (CH2O) and/or Volatile Organic Compounds (VOCs) from engines is often required to meet current pollutant emission regulations. VOCs are usually defined as non-methane (CH4), non-ethane (C2H6) hydrocarbons, excluding CH2O. In specification and operation of oxidation catalysts three critical issues are catalyst temperature, space velocity, and fouling. Reduction efficiencies of a commercially available oxidation catalyst are evaluated as a function of temperature and space velocity on a catalyst slip stream, where temperature and space velocity are controlled. Catalyst efficiencies are measured for CO, CH2O, and VOCs. Individual VOC efficiencies are also evaluated. The primary species contributing to VOCs emitted from lean burn natural gas engines are ethylene (C2H4) and propane (C3H8). Two different lean burn natural gas engines are utilized with the slipstream, a Cooper-Bessemer GMV-4TF 2-stroke engine and a Cummins GTA8.3 4-stroke engine. Catalyst fouling is assumed to come primarily from lubricating oil. Lubricating oil specifications are reviewed for a Cooper-Bessemer GMV-4TF and engine oil carry-over is measured to determine its potential to cause catalyst fouling and contribution to VOC emissions.