High Throughput Vehicle Test for Spatiotemporal Emissions Evaluation 2018-01-0642
The conventional evaluation of automotive catalysts has been carried out based on end-pipe measurement whereby the gas at the tailpipe of an automobile or the outlet of the bench reactor is monitored by using various analytical techniques such as Fourier-transform infrared spectroscopy (FTIR), mass spectrometry (MS), and gas chromatography (GC). However, this approach only provides overall gas concentrations at the exit flow of a monolith catalyst. Thereby, there is a deficiency of information on intra-catalyst chemistry. To obtain deeper insights on the design of an automotive catalyst, an emission breakdown analysis is critical. In this way, a comprehensive understanding of continuous processes along the catalyst length can be achieved. Here, we introduce the High Throughput Vehicle Test (HTVT), which is an analysis technology method for simultaneous emission observations at different catalyst positions in the vehicle. The core samples with different lengths were embedded in the original monolith catalyst for HTVT. Moreover, the gas concentrations along the length of the catalyst were measured by FTIR and gas analyzers. We then assessed the spatiotemporal distribution of reactions along two NOx trap bricks at the underflow catalytic converter (UCC) position of a gasoline vehicle during the FTP-75 (Federal Test Procedure) cycle. The results of the feasibility test suggest that HTVT can be utilized with temperature reliability and spatially resolved emissions within a ±12% error range. This study includes the HTVT results on the position impact of NOx storage component (NSC) and the Platinum Group Metals (PGM) ratio at the front and rear bricks of NOx trap performance. HTVT results exhibited that NOx conversions mainly occurred in the first quarter of the monolith catalyst, followed by CO conversions at the middle of catalyst length. The accountable HC conversions were detected in the last quarter of the catalyst axis. Both of the NSC zoned catalysts exhibited the enhancement of NOx conversion compared to the reference. The PGM front zoned catalyst represented the highest HC conversion, and the PGM rear catalyst showed an identical HC conversion to the reference at the outlet of the catalyst. These key findings demonstrate the feasibility of HTVT as a technology for spatiotemporal emissions evaluation. Furthermore, the new insights from the intra-catalyst reaction at zoned catalysts could facilitate the development of spatially coupled NOx trap catalysts.