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Methane Conversions
Published in Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda, 1 Chemistry, 2022
Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda
In the chlorine-containing systems, chlorine can dehydrogenate C2H6 in the gas phase and this homogeneous reaction is responsible for obtaining large C2H4/C2H6 ratios. In the presence of water, most of the chlorine is lost as HCl. Operating the reaction at lower temperatures can minimize rate of chlorine loss. As oxidative dehydrogenation of ethane, in comparison to oxidative coupling of methane, is faster on chlorinated catalysts, the favorable C2H4/C2H6 ratio can be obtained by these catalysts. The role of Cl− ions is similar to CO2 for selectivity (Ahmed and Moffat, 1990a).
Bimodal Reaction Sequences in Oxidation of Hydrogen and Organic Compounds with Dioxygen
Published in Robert Bakhtchadjian, Bimodal Oxidation: Coupling of Heterogeneous and Homogeneous Reactions, 2019
Oxidative coupling of methane (OCM) on the metal oxides or on the mixture of metal oxides was intensively investigated beginning in the 1980s. The formation of C2 hydrocarbons in the oxidation of methane was first observed by Nersissyan, during his doctoral research (before 1979) work188 that is not well known by English readers.189 Previously, it was reported that in the oxidation of methane over alumina and silica, the solid substances generated free radicals escaping to the gas phase.190 In English-language research, Mitchell and Waghorne in their USA Patent reported the formation of the coupling products by oxidation of methane in 1980.191 Further intensive investigations in this field were directed primarily toward exploration of selective catalysts for the oxidative coupling of methane giving ethane and, by further oxidative dehydrogenation, giving ethylene as unique process. An enormous number of solid substances—about several hundred—were tested as catalysts in order to design industrially suitable process in these investigations.192 By 2011, the number of scientific publications in this field had reached about 2840 (2700 articles and 140 patents).192
Chemicals from Paraffin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
In the oxidative coupling process, methane (CH4) and oxygen react over a catalyst to form water and a methyl radical (CH3•) (often referred to as partial oxidation). The methyl radicals combine to form a higher molecular weight alkane, mostly ethane (C2H6), which dehydrogenates into ethylene (CH2=CH2). Complete oxidation (rapid formation of carbon dioxide before the radicals link up to form ethane and ethylene) is an undesired reaction. The function of the catalyst is to control the oxidation so that reactions can be kept on the desired path and catalysts used are mostly oxides of alkali, alkaline earth, and other rare earth metals. Hydrogen and steam are sometimes added in order to reduce coking on catalysts.
Studies on oxidative coupling of methane using Sm2O3-based catalysts
Published in Chemical Engineering Communications, 2019
Hasan Özdemir, M. A. Faruk Öksüzömer, M. Ali Gürkaynak
Utilization of methane is an important topic for both academia and industry because of the waste of many natural gas reserves by flaring, reinjecting or venting to the atmosphere causing environmental pollution and economic losses. From this perspective, oxidative coupling of methane (OCM), which produces ethane and ethylene directly from methane, attracted considerable attention over decades (Keller and Bhasin, 1982; Hinsen and Baerns, 1983; Otsuka et al., 1985; Zhou et al., 1994; Bajus and Back, 1998; Rane et al., 1998; Wang et al., 2009; Balint et al., 2012; Ferreira et al., 2012; Raouf et al., 2013; Elkins et al., 2014; Song et al., 2015; Chu et al., 2016; Hiyoshi and Sato 2016; Oh et al., 2016; Yildiz et al., 2016). However, it has not been possible to design a catalyst that could provide higher C2 (C2H6 and C2H4) yields than 27% for the commercialization of this process because of the thermodynamic and kinetic constraints (Elkins and Hagelin-Weaver, 2013; Ghose et al., 2014).
Different catalytic reactor technologies in selective oxidation of propane to acrylic acid and acrolein
Published in Particulate Science and Technology, 2018
Golshan Mazloom, Seyed Mehdi Alavi
Some of these two-zone fluidized beds are represented schematically in Figure 11. Two-zone fluidized bed has been applied to different processes during the past decades, including oxidative coupling of methane, oxidative dehydrogenation of hydrocarbons, butane oxidation to maleic anhydride, and dehydrogenation of hydrocarbon (Soler et al. 2001; Herguido, Menéndez, and Santamaría 2005). However, to our knowledge, a two-zone fluidized-bed reactor has not been investigated for the case of selective oxidation of propane to acrylic acid until now.