Spillover effect for the oxidation of H2S in the presence of ammonia and water
About: This article is published in Studies in Surface Science and Catalysis.The article was published on 2001-01-01. It has received 1 citations till now. The article focuses on the topics: Spillover effect.
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TL;DR: In this article, vanadium oxide based catalysts were used for the selective removal of H 2 S. All the vanadium-based catalysts are effective for the conversion of hydrogen sulfide to ammonium thiosulfate (ATS) and elemental sulfur (S) without any considerable emission of sulfur dioxide.
Abstract: Publisher Summary This chapter investigates the development of vanadium oxide based catalysts for the selective removal of H 2 S. Hydrogen sulfide was successfully converted to ammonium thiosulfate (ATS) and elemental sulfur (S) without any considerable emission of sulfur dioxide. All the vanadium-based catalysts were effective for the conversion of H 2 S to ATS and S. A comparative analysis of V 2 O 5 with the mechanical mixture V 2 O 5 +Bi 2 O 3 (1:3) showed an increase of X–H 2 S and decrease of S–SO 2 over all the temperature range from 260–320°C. The reduction of V 2 O 5 is considered as a main cause of deactivation in the oxidation of H 2 S. To understand the role of Bi 2 O 3 in the mixture of V 2 O 5 +Bi 2 O 3 (1:3), TPR/TPO and x-ray photoelectron spectroscopy (XPS) analysis were performed. The operation with Bi 2 O 3 first followed by V 2 O 5 showed higher conversion than the reverse order operation. One conclusion can be drawn from this result that Bi 2 O 3 is a donor phase and V 2 O 5 is an acceptor phase for a mobile species.
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TL;DR: In this paper, the authors discuss the possible reasons why these phases cooperate (act synergetically) and different interpretations of the synergy is often due to remote control and discuss the various modifications of the acceptor brought about by spill-over oxygen.
Abstract: This review paper concerns allylic oxidations and oxidative dehydrogenations. The corresponding catalysts often contain two or several oxide phases. The objective is to discuss the possible reasons why these phases cooperate (act synergetically). Different interpretations are reviewed. The authors discuss in detail the evidence showing that the synergy is often due to remote control. In such a mechanism, one phase, the donor, dissociates oxygen to form a surface mobile species which spills over to the other phase, or acceptor. The acceptor is the potentially active phase. This phase needs to be irrigated by spill-over oxygen to exhibit maximum activity and selectivity. The various modifications of the acceptor brought about by spill-over oxygen are discussed: maintaining the acceptor at a high oxidation state, preventing the destruction of the structure of the acceptor, and inhibiting the formation of carbonaceous deposits or coke precursors. Parallel experiments with the same two-phase catalysts catalysing an oxygen aided dehydration suggest that the role of spill-over oxygen is to protect some Bronsted acidity of the acceptor. This interpretation of the cooperation between phases permits definite roles to be attributed to the oxide phases present in multicomponent catalysts and to measure approximately their ability to act as donors or acceptors.
198 citations
TL;DR: In this article, the Sb-V-O system was used for propane ammoxidation to acrylonitrile and high rate and selectivity for propylene formation at low conversion are characteristic for samples with excess vanadia and considering XRD, Raman, infrared and XPS results, this is explained by formation of amorphous vanadia spread over the surface of SbVO4.
141 citations
TL;DR: In this article, the basics of methods for removing sulphur dioxide and hydrogen sulphide from what are called acid gases, as well as equipment for this purpose, together with a discussion of the advantages and disadvantages of particular processes.
133 citations
TL;DR: In this article, the authors investigated selective catalytic oxidation of H 2 S to elemental sulfur using TiO 2 /SiO 2 catalysts and showed that the selectivity to sulfur was remarkably decreased, while the presence of water vapor decreased both the activity and selectivity.
Abstract: Selective catalytic oxidation of H 2 S to elemental sulfur using TiO 2 /SiO 2 catalysts was investigated in this study. The reaction test with pure TiS 2 and Ti(SO 4 ) 2 and cyclic temperature operation showed that TiO 2 had good resistance to sulfation and sulfidation, which are known as the main causes of catalytic deactivation in sulfur recovery process. Catalyst deactivation caused by deposition of sulfur on the catalyst surface resulted in a decrease in the conversion of H 2 S, not in the selectivity to sulfur, at low reaction temperatures. With an increase in the O 2 /H 2 S ratio from 0.5 to 4, the conversion was slightly increased, but the selectivity to elemental sulfur was remarkably decreased. The presence of water vapor decreased both the activity and selectivity. Temperature programmed desorption with NH 3 and CH 3 COOH and reaction tests after doping K 2 O and B 2 O 3 to TiO 2 /SiO 2 revealed that the selective oxidation of H 2 S occurred on acidic sites and the reverse Claus reaction proceeded on basic sites.
112 citations
103 citations