Effect of support on selectivity and on-stream stability of surface VOx species in non-oxidative propane dehydrogenation
07 Apr 2014-Catalysis Science & Technology (The Royal Society of Chemistry)-Vol. 4, Iss: 5, pp 1323-1332
TL;DR: Al2O3, SiO2(MCM-41), and Siral® with a SiO 2 content varying from 1 to 70 wt.% were used to prepare supported catalysts with a V loading below one monolayer.
About: This article is published in Catalysis Science & Technology.The article was published on 2014-04-07. It has received 58 citations till now. The article focuses on the topics: Dehydrogenation & Propene.
Citations
More filters
TL;DR: The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance, as dehydrogenation for the production of light olefins has become extremely relevant.
Abstract: A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.
1,306 citations
TL;DR: In this article, a review describes recent advances in the fundamental understandings of the Propane Dehydrogenation (PDH) process in terms of emerging technologies, catalyst development and new chemistry in regulating the catalyst structures and inhibiting the catalyst deactivation.
Abstract: Propylene is an important building block for enormous petrochemicals including polypropylene, propylene oxide, acrylonitrile and so forth. Propane dehydrogenation (PDH) is an industrial technology for direct propylene production which has received extensive attention in recent years. With the development of dehydrogenation technologies, the efficient adsorption/activation of propane and subsequential desorption of propylene on the surfaces of heterogeneous catalysts remain scientifically challenging. This review describes recent advances in the fundamental understandings of the PDH process in terms of emerging technologies, catalyst development and new chemistry in regulating the catalyst structures and inhibiting the catalyst deactivation. The active sites, reaction pathways and deactivation mechanisms of PDH over metals and metal oxides as well as their dependent factors are also analysed and discussed, which is expected to enable efficient catalyst design for minimizing the reaction barriers and controlling the selectivity towards propylene. The challenges and perspectives of PDH over heterogeneous catalysts are also proposed for further development.
222 citations
TL;DR: In this paper, the authors examined active species by attaining various fractions of V5+, V4+, and V3+ ions by adjusting the surface vanadium density on an alumina support.
Abstract: Supported VOx catalysts are promising for use in propane dehydrogenation (PDH) because of the relatively superior activity and stable performance upon regeneration. However, the nature of the active sites and reaction mechanism during PDH over VOx-based catalysts remains elusive. We examined active species by attaining various fractions of V5+, V4+, and V3+ ions by adjusting the surface vanadium density on an alumina support. The results reveal a close relationship between TOF and the fraction of V3+ ion, indicating that V3+ was more active for PDH. In situ diffuse reflectance infrared Fourier transform spectroscopy showed the same strong adsorbed species during both propane dehydrogenation and propylene hydrogenation. The results indicated that such an intermediate may correspond to V species containing a C═C bond, i.e., V–C3H5, and a reaction mechanism was proposed accordingly.
163 citations
TL;DR: The hydroxyl groups are found to improve the catalyst that leads to better stability by suppressing the coke deposition, and the catalytic performance for PDH is closely connected to the concentration of V-OH species on the catalyst.
Abstract: Supported vanadium oxides are one of the most promising alternative catalysts for propane dehydrogenation (PDH) and efforts have been made to improve its catalytic performance. However, unlike Pt-based catalysts, the nature of the active site and surface structure of the supported vanadium catalysts under reductive reaction conditions still remain elusive. This paper describes the surface structure and the important role of surface-bound hydroxyl groups on VOx / γ-Al2 O3 catalysts under reaction conditions employing in situ DRIFTS experiments and DFT calculations. It is shown that hydroxyl groups on the VOx /Al2 O3 catalyst (V-OH) are produced under H2 pre-reduction, and the catalytic performance for PDH is closely connected to the concentration of V-OH species on the catalyst. The hydroxyl groups are found to improve the catalyst that leads to better stability by suppressing the coke deposition.
135 citations
TL;DR: In this article, the progress of catalytic non-oxidative direct dehydrogenation of light alkanes has been summarized for different classes of the most promising catalysts in the selective degradation of ethane toethylene and propane-to-propylene, their syntheses, structural information, catalytic properties and mechanisms are comparatively summarized.
Abstract: Catalytic non-oxidative direct dehydrogenation of light alkanes serves as an effective reinforcement to selectively produce the corresponding olefins, and the heterogeneous metals and metal oxides, not limited to the commercially used Pt- and Cr-based catalysts, are widely investigated to enhance the efficiency. In this review, we outline the progress of these dehydrogenation catalysts that have been mainly developed in the past five years. For different classes of the most-promising catalysts in the selective dehydrogenation of ethane-to-ethylene and propane-to-propylene, their syntheses, structural information, catalytic properties and mechanisms are comparatively summarized.
121 citations
References
More filters
TL;DR: The use of carbon dioxide as an oxidant for ethane conversion to ethylene has been investigated as a potential way to reduce the negative impact of dangerous oxidant-paraffin mixtures and to achieve higher selectivity as mentioned in this paper.
Abstract: Catalytic paraffin dehydrogenation for the production of olefins has been in commercial use since the late 1930s, while catalytic paraffin oxydehydrogenation for olefin production has not yet been commercialized. However, there are some interesting recent developments worthy of further research and development. During World War II, catalytic dehydrogenation of butanes over a chromia-alumina catalyst was practiced for the production of butenes that were then dimerized to octenes and hydrogenated to octanes to yield high-octane aviation fuel. Dehydrogenation employs chromia-alumina catalysts and, more recently, platinum or modified platinum catalysts. Important aspects in dehydrogenation entail approaching equilibrium or near-equilibrium conversions while minimizing side reactions and coke formation. Commercial processes for the catalytic dehydrogenation of propane and butanes attain per-pass conversions in the range of 30–60%, while the catalytic dehydrogenation of C 10 –C 14 paraffins typically operates at conversion levels of 10–20%. In the year 2000, nearly 7 million metric tons of C 3 –C 4 olefins and 2 million metric tons of C 10 –C 14 range olefins were produced via catalytic dehydrogenation. Oxydehydrogenation employs catalysts containing vanadium and, more recently, platinum. Oxydehydrogenation at ∼1000 °C and very short residence time over Pt and Pt-Sn catalysts can produce ethylene in higher yields than in steam cracking. However, there are a number of issues related to safety and process upsets that need to be addressed. Important objectives in oxydehydrogenation are attaining high selectivity to olefins with high conversion of paraffin and minimizing potentially dangerous mixtures of paraffin and oxidant. More recently, the use of carbon dioxide as an oxidant for ethane conversion to ethylene has been investigated as a potential way to reduce the negative impact of dangerous oxidant–paraffin mixtures and to achieve higher selectivity. While catalytic dehydrogenation reflects a relatively mature and well-established technology, oxydehydrogenation can in many respects be characterized as still being in its infancy. Oxydehydrogenation, however, offers substantial thermodynamic advantages and is an area of active research in many fronts.
614 citations
TL;DR: In this article, the catalytic performances of Pt/Al2O3 and Pt-Sn/Al 2O3 catalysts for the dehydrogenation of propane through consecutive reaction-regeneration cycles have been studied under realistic reaction conditions.
243 citations
TL;DR: In this article, the authors show that the In content of the bimetallic particles increases with increasing bulk In/Pt ratio and reduction temperature, and that an increasing donation of electronic charge from In to Pt occurs with increasing In content in the PtIn particles.
197 citations
TL;DR: In this paper, the MCM-48-supported vanadium oxide catalysts have been investigated and the properties of the catalysts were characterized using ESR spectroscopy and chemical methods.
165 citations
TL;DR: In this article, a series of V/MCM-41 catalytic materials were synthesized by impregnation of MCM41 and the addition of vanadium during the preparation, and they were studied by different spectroscopic techniques (TEM, TPR, in situ UV-vis, and in situ Raman).
146 citations