Catalytic Dehydrogenation of Hydrocarbons

Skarchenko, V K

doi:10.1070/rc1971v040n12abeh001988

Cited by 8 publications

(1 citation statement)

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“…29−31 The dehydrogenation mechanism will also involve the help of catalysts to overcome energy barriers in the range of 64− 104 kJ mol −1 , and in the case of cyclohexane, the release of hydrogen would occur along the formation of an intermediate sextet; i.e., the cyclohexane molecule adsorbs onto the catalyst surface on six points to enable the dissociation of the six C−H bonds (Figure 2(b)). 32,33 According to the multiplet theory, reactions involving the dissociation of two C−H bonds would occur via a doublet mechanism involving a two-point adsorption of the molecule to be dehydrogenated (Figure 2(a)). 34 It should be noted that hydrogenation reactions are generally favorable because of their exothermic nature, for example, the enthalpy of conversion of benzene into cyclohexane at 205 kJ mol −1 .…”

Section: General Principlesmentioning

confidence: 99%

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Salman

Rambhujun

Pratthana

et al. 2022

Ind. Eng. Chem. Res.

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With the renewed interest for hydrogen as an energy carrier, means to produce, but most importantly store, transport, and distribute, "green" hydrogen over long distances has become important. In this context, liquid organic molecules that can be hydrogenated and dehydrogenated under mild conditions of temperature and pressure continue to attract significant attention. These liquid organic molecules referred as "liquid organic hydrides" in the early 1980s include molecules such as cyclohexane, methylcyclohexane, decalin, N-heterocycles, methanol, ethanol, and formic acid. However, current liquid organic hydrides still suffer from limitations along with the emergence of more effective catalysts to meet the requirement of competing (de)hydrogenation reactions, as well as new chemistry to enable their (de)hydrogenation reactions under milder conditions and extended cycle lives. Herein, we critically review common state-ofthe-art catalyst designs, which remain one of the main barriers to the effective emergence of liquid organic hydrogen carriers enabling the widespread transport and distribution of hydrogen. Many of the most effective current catalysts are based on noble metals. Transitioning away from these rare critical elements to enable hydrogen uptake/release from organic compounds under economically viable chemical routes is a necessity.

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Section: General Principlesmentioning

confidence: 99%

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Salman

Rambhujun

Pratthana

et al. 2022

Ind. Eng. Chem. Res.

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Direct Sulfonation of Methane to Methanesulfonic Acid by Sulfur Trioxide Catalyzed by Cerium(IV) Sulfate in the Presence of Molecular Oxygen

Mukhopadhyay

Bell

2004

Adv Synth Catal

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Direct sulfonation of methane with SO 3 to methanesulfonic acid (MSA) is accomplished in sulfuric acid with almost 100% selectivity in the presence of a catalyst, namely, Ce and Rh salts and molecular oxygen as the catalyst regenerator. In the absence of O 2 , the catalyst remains effective but the selectivity to MSA decreases to 53% and byproducts, principally CH 3 OSO 3 H, are formed. The effects of O 2 pressure, catalyst concentration, temperature, SO 3 concentration, and methane pressure have been examined on the rate of SO 3 conversion to MSA. The conversion of SO 3 to MSA was the same when CF 3 SO 3 H was used as the solvent instead of H 2 SO 4 .Keywords: C À H activation; metal catalyst; methane; methanesulfonic acid; molecular oxygen; sulfonation; sulfur trioxide Methanesulfonic acid (MSA, 70 wt %) is widely used in electrochemical systems and is an excellent catalyst for the esterification, alkylation, and condensation of organic compounds. [1] Lower reaction temperatures are required when using MSA rather than titanate catalysts, and purer, more colorless products can be obtained using MSA than those produced using sulfuric or para-toluenesulfonic acid as the catalyst. Anhydrous MSA is also particularly well suited for pharmaceutical applications and as a catalyst for aromatic alkylation. The current commercial process for the synthesis of MSA involves chlorine oxidation of methylmercaptan. [2] While this process is highly productive, it produces six moles of HCl per mole of MSA, resulting in a coupling of the demand for the primary product and the byproduct. As an alternative it is interesting to consider a direct methane sulfonation route using SO 3 or SO 2 and O 2 as the sulfonating agent. Sen and co-workers [3a] and, more recently, we [3b, c] have shown that a compound such as K 2 S 2 O 8 can be used as a free radical initiator [3d] to sulfonate methane with SO 3 in fuming sulfuric acid.Identification of a catalytic process for the sulfonation of methane would highly desirable, since this would eliminate the need for a free-radical initiator. While Ishii and co-workers have reported success in the vanadium-catalyzed sulfonation of adamantane to the corresponding sulfonic acids using SO 2 and O 2 , methane did not undergo sulfonation to MSA. [4] Hg-based catalysts have been used at elevated temperature (300 ± 450 8C) for methane sulfonation with SO 3 to MSA; however this process exhibits a low yield and cannot be implemented due to problems in isolating MSA from a mixture of byproducts, mainly esters and disulfonic acids formed during this reaction. [5] In subsequent studies, Periana and co-workers [6] have reported the selective sulfonation of CH 4 to MSA in fuming sulfuric acid at 180 to 220 8C using Hg salts [6a] or Pt complexes as the catalyst. [6b] In both the cases, the metal cations undergo reduction and are reoxidized by sulfuric acid. [6] We have recently shown that Hg(CF 3 SO 3 H) 2 can be used in the presence of O 2 to synthesize MSA by the reaction of methane and SO 3 in ...

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ChemInform Abstract: KATALYTISCHE DEHYDRIERUNG VON KOHLENWASSERSTOFFEN

Skarchenko¹

1972

Chemischer Informationsdienst

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Catalytic Dehydrogenation of Hydrocarbons

Cited by 8 publications

References 1 publication

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Direct Sulfonation of Methane to Methanesulfonic Acid by Sulfur Trioxide Catalyzed by Cerium(IV) Sulfate in the Presence of Molecular Oxygen

ChemInform Abstract: KATALYTISCHE DEHYDRIERUNG VON KOHLENWASSERSTOFFEN

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