Studies on the influence of H 2 S and SO 2 on the activity of a PdO/Al 2 O 3 catalyst for removal of oxygen by total oxidation of (bio-)methane at very low O 2 :CH 4 ratios

Abstract

This work focuses on the deactivation and in-situ regeneration effects of a commercial PdO/Al 2 O 3 catalyst for removal of oxygen by oxidation of CH 4 at low O 2 :CH 4 ratios when hydrogen sulfide and sulfur dioxide are applied. The experimental work is carried out at an operating temperature range of 200 °C < T < 300 °C, atmospheric pressures and H 2 S contents of < 50 ppmv. SO 2 and H 2 S show a different behavior in the examined range of operating conditions. Due to the low operating temperatures and low oxygen contents applied in this work, it was possible to identify an intermediate species, presumably PdSO 3 , with an increased activity for the oxidation of methane. This stands in contrast to the literature, where SO 2 typically causes catalyst deactivation. Based on the experimental results, a reaction scheme was derived and kinetic measurements for each of the participating reactions were carried out separately.

High Stability of Rh Oxide-Based Thermoresistive Catalytic Combustion Sensors Proven by Operando X-ray Absorption Spectroscopy and X-ray Diffraction

“…29 The formation of the stable sulfate or/and sulfite species on PdO/Al 2 O 3 during H 2 S and SO 2 exposure was found to be a reason for the deactivation of the catalysts. 30 A similar effect was observed on bimetallic Pt-Pd particles. 31,32 Rhodium shows usually better resistance to SO 2 33 and H 2 S poisoning and can be reactivated by treatment in pure H 2 or O 2 at high temperatures.…”

“…After normal operation (at temperatures about 500–600 °C) for several hours and controlled exposure to the H 2 S gas, the enhancement of the Rh–O bond strength in the presence of sulfur might indicate the formation of rhodium sulfate causing the chemical blocking of the active oxygen leading to irreversible poisoning of the pellistors. The adsorption of H 2 S on O–Rh sites with following rhodium sulfite and sulfate formation due to the reaction with oxygen from the reactive gas mixture similar to the mechanism proposed for the PdO/Al 2 O 3 and Rh/Al 2 O 3 but without the formation of aluminum sulfate might also be applicable in this case of poisoning.…”

“…The catalytic activity is usually reduced by the presence of sulfur-containing compounds . The formation of the stable sulfate or/and sulfite species on PdO/Al 2 O 3 during H 2 S and SO 2 exposure was found to be a reason for the deactivation of the catalysts . A similar effect was observed on bimetallic Pt-Pd particles. , Rhodium shows usually better resistance to SO 2 and H 2 S poisoning and can be reactivated by treatment in pure H 2 or O 2 at high temperatures. , Formation of sulfonate and sulfate during the reforming at 800 °C has been reported for metallic Rh/Al 2 O 3.…”

Catalytic Oxygen Removal from Synthetic Coke Oven Gas: A Comparison of Sulfided CoMo/γ‐Al2O3 and NiMo/γ‐Al2O3 Catalysts with Pt/γ‐Al2O3 as Benchmark Catalyst

“…Oxygen causes corrosion in piping systems, which results in safety hazards due to gas leaks and costly replacement. The oxygen content in German natural gas networks is limited to 10 ppmv by law . A low oxygen content results in an immediate deactivation of the catalyst, e.g., in the Fischer‐Tropsch synthesis from a biogas process , .…”

Pd4S/SiO2: A Sulfur-Tolerant Palladium Catalyst for Catalytic Complete Oxidation of Methane

“…Supported PdO catalysts have shown excellent catalytic property in methane oxidation, and currently are under extensive study [11][12][13][14][15][16][17][18]. However, once sulfur species (e.g., H 2 S or SO 2 ) are present in the reaction atmosphere, the poisoning of PdO catalyst which would lead to inactive PdO-SO x is irreversible and the activity of the catalyst cannot be recovered at relatively low temperature [19][20][21][22][23][24][25].…”