Comparative study of coke deposition on catalysts in reactions with and without oxygen |
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Authors: | P Praserthdam C Chaisuk P Kanchanawanichkun |
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Institution: | (1) Petrochemical Research Laboratory, Department of Chemical Engineering, Chulalongkorn University, 10330 Bangkok, Thailand |
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Abstract: | Two types of catalysts, i.e. Pt/γ Al2O3 and Cu/Na-ZSM-5, were used to investigate the catalyst activity and amount of coke formation on the spent catalysts. The
reactions of particular interest were the hydrocarbon oxidation and the SCR of NO with and without O2. Propane and propene were used as the hydrocarbon sources. The reaction conditions were as follows: reaction temperature
=170–500°C, GHSV=4,000 hr−1, TOS=2 hr, feed composition depending on each reaction, but the composition of gases were fixed as HC=3,000 ppm, NO=1,000
ppm and O2=2.5%, using He balance. It was found that both the case of Pt/γ Al2O3 and the case of Cu/Na-ZSM-5, propene provided higher conversion and coke deposition than propane in the presence or the absence
of O2 and/or NO. For Pt/γ Al2O3 catalyst, in case of the absence of oxygen reactions, the propene conversion dropped more rapidly than the propane conversion.
Finally the reaction of propene gave a lower percent of hydrocarbon conversion than the reaction of propane. Additionally,
propene had a higher percent selectivity of coke formation for the reaction with the absence of oxygen, but propane had a
higher percent selectivity of coke formation for the reaction with the presence of oxygen. For Cu/Na-ZSM-5, in the system
with absence and presence of oxygen, the addition of oxygen caused a significant change in % coke selectivity. With the presence
of NOx, the percent conversion of both propane and propene decreased and that the % coke selectivity of propane decreased, whereas
that of in propene increased. |
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