The use of vanadia selective catalytic reduction (V-SCR) catalysts for NO X reduction from diesel engine exhaust is well known. These catalysts are also active for hydrocarbon (HC) and particulate matter (PM) oxidation. This dual functionality (oxidation and reduction) of V-SCR catalysts can help certain applications achieve the legislative limits with an improved margin. In this work, NO X reduction, HC and CO oxidation over V-SCR were studied independently and simultaneously in microreactor tests. The effect of various parameters (HC speciation, concentration, ANR, and NO\u2082/NO X ratio) was investigated and the data was used to develop a kinetic model. Oxidation of CO, C\u2083H\u2086, and n-C\u2081\u2080H\u20
82\u2082 is first order in CO/HC, while C\u2087H\u2088 oxidation is less than first order in C\u2087H\u2088. All these reactions were zero order in O\u2082. Oxidation activity decreased in order: C\u2087H\u2088 \u227b n-C\u2081\u2080H\u20
82\u2082 \u227b C\u2083H\u2086 \u227b CO. HC oxidation was inhibited by NH\u2083. The presence of HCs was found to inhibit NO X conversion, but only after the HC had started to react. This can be explained by NO X reduction being inhibited not by the HC itself, but by the CO produced from partial oxidation of the HC. The V-SCR catalyst was also tested on a diesel engine in the absence of an upstream DOC and DPF to investigate its performance. The results confirm that V-SCR can remove HC and PM effectively: for temperatures above 230°C, V-SCR showed 45-75% HC conversion and 20-60% PM removal, under the specific engine conditions tested. This data was used to validate the kinetic model.
The use of vanadia selective catalytic reduction (V-SCR) catalysts for NO X reduction from diesel engine exhaust is well known. These catalysts are also active for hydrocarbon (HC) and particulate matter (PM) oxidation. This dual functionality (oxidation and reduction) of V-SCR catalysts can help certain applications achieve the legislative limits with an improved margin. In this work, NO X reduction, HC and CO oxidation over V-SCR were studied independently and simultaneously in microreactor tests. The effect of various parameters (HC speciation, concentration, ANR, and NO\u2082/NO X ratio) was investigated and the data was used to develop a kinetic model. Oxidation of CO, C\u2083H\u2086, and n-C\u2081\u2080H\u2082\u2082 is first order in CO/HC, while C\u2087H\u2088 oxidation is less than first order in C\u2087H\u2088. All these reactions were zero order in O\u2082. Oxidation activity decreased in order: C\u2087H\u2088 \u227b n-C\u2081\u2080H\u2082\u2082 \u227b C\u2083H\u2086 \u227b CO. HC oxidation was inhibited by NH\u2083. The presence of HCs was found to inhibit NO X conversion, but only after the HC had started to react. This can be explained by NO X reduction being inhibited not by the HC itself, but by the CO produced from partial oxidation of the HC. The V-SCR catalyst was also tested on a diesel engine in the absence of an upstream DOC and DPF to investigate its performance. The results confirm that V-SCR can remove HC and PM effectively: for temperatures above 230°C, V-SCR showed 45-75% HC conversion and 20-60% PM removal, under the specific engine conditions tested. This data was used to validate the kinetic model.
