Development of High Porosity Cordierite Honeycomb Substrate for SCR Application to Realize High NOx Conversion Efficiency and System Compactness

Abstract

Today the Ammonia Selective Catalytic Reduction (SCR) system with good NOx conversion is the emission technology of choice for diesel engines globally. High NOx conversion SCR systems combined with optimized engine calibration not only address the stringent NOx emission limits which have been introduced or are being considered for later this decade, but also reduce CO 2 emissions required by government regulations and the increase in fuel economy required by end-users. Reducing the packaging envelope of today's SCR systems, while retaining or improving NOx conversion and pressure drop, is a key customer demand.High SCR loadings ensure high NOx conversion at very low temperatures. To meet this performance requirement, a High Porosity Substrate which minimizes the pressure drop impact, was introduced in SAE Paper 2012-01-1079 [1], [2], [3]. The High Porosity Substrate with an equivalent catalyst amount demonstrated a pressure drop reduction in SCR substrate against the baseline conventional substrate. Moreover, high porosity substrate with high catalyst amount shows a possibility to achieve high NOx conversion and significant downsizing. As previously proven [4], [5], [6], High CellDensity is an effective way to increase catalyst surface area and NOx conversion at high temperatures due to the mass transfer effect. A High Porosity, High Cell Density Substrate has been developed which offers a notable improvement in NOx conversion over a wide temperature range as well as SCR substrate volume reduction. This paper will define the concept and SCR NOx conversion performance of the new High Porosity with High Cell Density Substrate compared to conventional substrate. The evaluation also includes pressure drop, durability, and potential SCR downsizing.

Development of Emission Control Systems to Enable High NOx Conversion on Heavy Duty Diesel Engines

“…For the downstream flow through SCR catalysts, work is continuing to demonstrate that high NO x reduction can be achieved by placing a high amount of active catalytic material on highly porous and high cell density flow through substrates [6,7,8]. In the current study, results are being presented from the evaluation of combinations of a cold start catalyst plus SCR-DPF unit with downstream high porosity SCR catalysts to achieve high NO x conversions.…”

High Porosity Substrates for Fast-Light-Off Applications

“…The microstructure of the substrate may be engineered to either allow or inhibit penetration of washcoat particles into the wall. A recent example is use of porous substrate walls to host zeolite washcoat for selective catalytic reduction (SCR) to lower pressure drop and simultaneously increase the catalyst load [17].…”

Simulation study on improving the selective catalytic reduction efficiency by using the temperature rise in a non-road transient cycle

“…18 In addition, application of both a high cell density and a high-porosity substrate makes it possible to attain not only a notable improvement in the NO x conversion over a wide temperature range but also a reduction in the volume of the SCR substrate. 21…”

“…17 Second, there have been many research studies and developments to improve the geometrical characteristics of the SCR substrates. [18][19][20][21][22] One of the key technical directions is to increase the cell density of the SCR substrate to 900 cells/in 2 , while 400 cells/in 2 is the commercial mainstream value utilized at present. 18,20 A high-cell-density substrate can easily provide more active catalytic sites, which enables the exhaust gas to have more deNO x reaction opportunities.…”

“…18 In addition, application of both a high cell density and a highporosity substrate makes it possible to attain not only a notable improvement in the NO x conversion over a wide temperature range but also a reduction in the volume of the SCR substrate. 21 Third, improvements in the urea mixing and dosing technologies are quite impressive. [23][24][25][26][27] Design optimization for the exhaust flow promotes evaporation of the urea-water-solution spray droplets, thermal decomposition of the urea and mixing of the urea with the exhaust gas stream, which give a better spatial distribution and a higher uniformity of NH 3 before the SCR catalyst.…”