Development of a rapid ageing technique for modern methane combustion catalysts in the laboratory: Why does SO2 concentration play an essential role?

A Review on the Impact of SO2 on the Oxidation of NO, Hydrocarbons, and CO in Diesel Emission Control Catalysis

“…116 Another study regarding lean-burn CH 4 oxidation over bimetallic Pd/Pt/ Al 2 O 3 shows that low SO 2 concentration leads to more stable bulk PdSO 4 , while high-concentration SO 2 tends spill over onto the support to form less stable Al 2 (SO 4 ) 3 . 233 Although the former gathers a lower total sulfur amount, it acquires equal activity to the latter because of the lower desorption rate of sulfur and limited spillover ability, ending up with saturation of active sites. 131,233 Currently, the mandate over ultralow sulfur fuel (ULSD) makes DOCs possible to exhibit good performance for an extended time while continuous accumulation of sulfur species in DOCs can still result in degraded catalytic performance in the long run in reality.…”

“…233 Although the former gathers a lower total sulfur amount, it acquires equal activity to the latter because of the lower desorption rate of sulfur and limited spillover ability, ending up with saturation of active sites. 131,233 Currently, the mandate over ultralow sulfur fuel (ULSD) makes DOCs possible to exhibit good performance for an extended time while continuous accumulation of sulfur species in DOCs can still result in degraded catalytic performance in the long run in reality. 91 A last but not least concern associated with the real-world operation is that catalyst aging is a combination of hydrothermal aging and chemical contaminations (which are not only limited to S poison but also include non-S contaminants such as P and minor metal impurities).…”

“…119,241 However, with excess H 2 or dry CO, the stepwise reduction of sulfate will lead to the yield of H 2 S/COS or sulfur species adsorbed on Pt and oxides (e.g., in the form of cerium oxysulfur). 233,249,255,256 Moreover, the presence of H 2 O promotes SO 2 and H 2 S releases where surface hydroxyls may get involved in the formation of H 2 S even when H 2 O is absent. 240 For Pd-rich CH 4 oxidation catalysts, the regeneration may eventually result in the formation of Pd 4 S species (via PdSO 4 + 4H 2 → PdS + 4H 2 O).…”

“…An early report observes a full recovery of HCs oxidation in the simulated exhaust feed stream (containing propylene/propane mixture, CO, NO x ) when SO 2 is increased from 1 to 5 ppm and then returned to 1 ppm; however, a partial recovery is evident when SO 2 is reduced to 1 ppm from 30 ppm, unless the catalyst is operated at or above 700 °C . Another study regarding lean-burn CH 4 oxidation over bimetallic Pd/Pt/Al 2 O 3 shows that low SO 2 concentration leads to more stable bulk PdSO 4 , while high-concentration SO 2 tends spill over onto the support to form less stable Al 2 (SO 4 ) 3 . Although the former gathers a lower total sulfur amount, it acquires equal activity to the latter because of the lower desorption rate of sulfur and limited spillover ability, ending up with saturation of active sites. , Currently, the mandate over ultralow sulfur fuel (ULSD) makes DOCs possible to exhibit good performance for an extended time while continuous accumulation of sulfur species in DOCs can still result in degraded catalytic performance in the long run in reality …”

Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

“…For realistic conditions, besides adjusting the aging time and temperature, catalyst poisons in the feed, e.g., sulfur compounds, should also be considered [14]. Rapid aging procedures have, to the best of our knowledge, so far mainly been described for automotive emission catalysts, i.e., for the three-way catalyst [15,16], for diesel oxidation catalysts [14,16], for lean NO x trap catalysts [17] or for methane combustion catalysts in lean-operating natural gas engines [16,18] and for PEM fuel cells [19]. For other applications, there are only a few reports on rapid aging, e.g., for Cu catalysts for methanol synthesis, where sintering is responsible for deactivation [20].…”