(130b) Pilot Reactor Studies on a Low Temperature Soot Oxidation Catalyst

Pilot Reactor Studies on a Low Temperature Soot Oxidation Catalyst

^{1, 2}James Zokoe, ^1,2Changsheng Su^*, ¹Ashok Kumar, ¹Arvind Harinath

²Paul McGinn^*

¹: Cummins, Inc.

²: University of Notre Dame, Dept. of Chemical and Biomolecular Engineering

Corresponding author: changsheng.su@cummins.com
Corresponding author: pmcginn@nd.edu

Abstract

Diesel particulate filters (DPFs) will be required to meet current and future particulate matter (PM) and particulate number (PN) regulations in diesel engines for both on and off-highway applications.  In aftertreatment systems utilizing an active DPF regeneration methodology, fuel consumption and overall cost can be lessened by lowering the required temperature of O₂based soot oxidation by applying a PGM free catalyst.  Alkali metal based catalysts provide the low temperature oxidation of soot, but quickly degrade in the harsh conditions of the diesel exhaust.  Novel potassium-containing glass catalysts have recently been shown to stabilize the K within a silicate matrix and initial degradation studies have shown promise with soot oxidation as low as 380°C in loose catalyst-soot contact conditions [1,2,3].

To better understand potential performance limitations of these potassium-containing glass catalysts, degradation mechanisms experienced by the glasses with prolonged use were investigated and were found to fall into two categories termed as follows: combustion (K loss) and chemical (hydrothermal) degradation [3].  Potassium-containing catalyst coated mullite core sized samples (1” x 3”) were used to measure degradation through an end of useful lifetime (EUL) of an estimated 100,000 mi of engine use.  Testing was facilitated with the collaborative effort of the industry to perform pilot reactor scale catalyst testing for the diesel soot oxidation catalyst [4]. This pilot soot reactor was used to elicit continuous soot deposition and oxidation throughout the EUL test.

A baseline glass catalyst [2] was found to sustain acceptable soot oxidation temperatures after this estimated lifetime reactor testing (initial T₅₀ of 425°C, EUL T₅₀of 475°C,).  The measured catalytic degradation was found to be caused by K-accumulation and migration with Ca-rich precipitate formation on the surface [3].

Observations from this testing led to optimization of the baseline glass composition. An improved catalyst composition, herein termed Cat-2, was shown to provide greater hydrothermal durability while providing comparative soot oxidation temperatures to the Cat-1 catalyst.

[1]       An, H., Su, C., & McGinn, P. (2009). Application of potash glass as a catalyst for diesel soot oxidation. Catalysis Communications, 10(5), 509-512. doi:10.1016/j.catcom.2008.10.019.

[2]       Su, C. & McGinn, P. (2013). The effect of Ca⁺² and Al⁺³ additions on the stability of potassium disilicate glass as a soot oxidation catalyst. Applied Catalysis.B, Environmental, 138, 70-78. doi:10.1016/j.apcatb.2013.02.022.

[3]       Zokoe, J. & McGinn, P. (2015).  Catalytic diesel soot oxidation by hydrothermally stable glass catalysts.  Chemical Engineering Journal, 262, 68-77.  doi:10.1016/j.cej.2014.09.075.

[4]       Chen, X., Kumar, A., Klippstein, D., Stafford, R., Su, C., Yuan, Y., Zokoe, J., McGinn, P. Development and Demonstration of a Soot Generator Integrated Bench Reactor, (2014). SAE Technical Paper. doi:10.4271/2014-01-1589.