Diesel Exhaust Treatment Using Catalysts/Zeolites-II Final rept. (Jul 03-Jun 05)

摘要

Catalytic converters have become a viable post-treatment system for reducing emissions from on-highway diesel engines. This investigation attempted to develop and test a catalyst (copper ion-exchanged ZSM-5 zeolite) system for its ability to effectively treat diesel exhaust gas. During the first phase of this investigation (UTCA project 02201), catalyst/zeolites were used in a laboratory scale plug flow reactor system to treat synthetic diesel exhaust gas maintaining operating temperature at 200-3000F (93.3-148.90C), pressures at 6 and 12 psig, and the space velocity through the reactor at approx. 8000 hr '. The exhaust gas composition was monitored before and after passing through the catalyst system using gas chromatography techniques. Despite relatively low operating temperature, the hydrocarbons (particularly methane) removal efficiency was fairly good, ranged from 30 percent to 80 percent depending upon the variation in the composition of the catalyst samples/zeolite structures. Therefore this catalyst system seemed promising for large reduction of hydrocarbons from the diesel exhaust. Two modiBed catalysts were prepared which involved incorporating CeO2 and ZrO2 as the external coating on the previously made Cu-ZSM-5 catalysts. The size and shape of new catalysts were changed to help minimize pressure drop as well as catalyst loss from the system at high back pressure. The conversion efficiency of methane was tested using both catalysts for temperatures in the range from 200 to 8000F (93.3-426.7 degrees C) at four different space velocities (ranging from approx. 10,000 to approx. 25,000 br ) and the conversion efficiency of butane was tested at the same temperature range and the space velocity of approx. 30,000 hr .