Oxidative Functionalization of Methane on Heterogeneous Catalysts

Sanchez‐Sanchez, Maricruz; Lercher, Johannes A.

doi:10.1002/9781119379256.ch8

Cited by 2 publications

(2 citation statements)

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“… 6 , 17 , 18 A commercially interesting catalyst must be able to operate over prolonged times with high CH 3 Cl selectivity and CH 4 conversion level. 19 Furthermore, the selectivity to CO x needs to be minimized to make optimal use of the chemical feedstock and to lower separation costs. 14 These aforementioned requirements are challenging, and very little is known about how to fulfill these catalyst requirements.…”

Section: Introductionmentioning

confidence: 99%

“…From the perspective of a circular economy approach, methane oxychlorination (MOC) has the additional advantage of being able to utilize HCl, a byproduct of other chlorination reactions. , However, the corrosive and oxidative environment under which the MOC catalysts must operate pose technological challenges and hinder the industrialization of the process. ,, A commercially interesting catalyst must be able to operate over prolonged times with high CH 3 Cl selectivity and CH 4 conversion level . Furthermore, the selectivity to CO x needs to be minimized to make optimal use of the chemical feedstock and to lower separation costs .…”

Section: Introductionmentioning

confidence: 99%

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Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Terlingen

Oord

Ahr³

et al. 2022

ACS Catal.

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The direct conversion of CH 4 into fuels and chemicals produces less waste, requires smaller capital investments, and has improved energy efficiency compared to multistep processes. While the methane oxychlorination (MOC) reaction has been given little attention, it offers the potential to achieve high CH 4 conversion levels at high selectivities. In a continuing effort to design commercially interesting MOC catalysts, we have improved the catalyst design of EuOCl by the partial replacement of Eu 3+ by La 3+ . A set of catalytic solid solutions of La 3+ and Eu 3+ (i.e., La x Eu 1– x OCl, where x = 0, 0.25, 0.50, 0.75, and 1) were synthesized and tested in the MOC reaction. The La 3+ –Eu 3+ catalysts exhibit an increased CH 3 Cl selectivity (i.e., 54–66 vs 41–52%), a lower CH 2 Cl 2 selectivity (i.e., 8–24 vs 18–34%), and a comparable CO selectivity (i.e., 11–28 vs 14–28%) compared to EuOCl under the same reaction conditions and varying HCl concentrations in the feed. The La 3+ –Eu 3+ catalysts possessed a higher CH 4 conversion rate than when the individual activities of LaOCl and EuOCl are summed with a similar La 3+ /Eu 3+ ratio (i.e., the linear combination). In the solid solution, La 3+ is readily chlorinated and acts as a chlorine buffer that can transfer chlorine to the active Eu 3+ phase, thereby enhancing the activity. The improved catalyst design enhances the CH 3 Cl yield and selectivity and reduces the catalyst cost and the separation cost of the unreacted HCl. These results showcase that, by matching intrinsic material properties, catalyst design can be altered to overcome reaction bottlenecks.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Terlingen

Oord

Ahr³

et al. 2022

ACS Catal.

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Activation of C–H bonds of normal alkanes in sulfuric acid solutions of Mn(III)/Mn(II)

Volkova¹,

Opeida²

2021

Kataliz ta naftohimia

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One of the most important directions of establishing the mechanisms of activation of C–H bonds, both in saturated and aromatic hydrocarbons in aqueous and sulfuric acid solutions of oxidants, metal complexes and radicals, is to study the kinetics of reactions and the influence of temperature, environment, nature of reagents, etc. The study of mechanisms is important for the development of technologies for processing hydrocarbons into products with high added value. In this work, to determine the nature of limiting stages and mechanisms of reactions of one group of saturated hydrocarbons, normal alkanes, we use the dependences of substrate selectivity (relative rate constants) on their characteristics: ionization potentials, energy and number of primary and secondary C–H bonds. To determine the nature of the limiting stages of reactions of normal alkanes, the correlations between the logarithms of substrate selectivity of alkanes reactions in H2SO4 solutions with one of the most active manganese(III) ions and molecule properties or C–H bond type were studied by the method of correlation analysis. Comparison of the obtained results with quantum-chemically calculated enthalpy changes of different possible variants of the course of this elementary reaction allowed to clarify the mechanism and propose tests to perform the mechanism of the slow limiting stage. It is shown that for alkanes (ethane, pentane, hexane, heptane, octane) the linear dependence with the ionization potential is most accurately performed, the least accurate is the correlation with the number of secondary C–H bonds, which indicates the electron abstraction in the slow limiting stage. For the shorter pentane – octane series, correlation dependences on both the number of secondary C–H bonds and the ionization potentials are performed with almost equal accuracy, which makes it impossible to establish the nature of the slow stage. The results of quantum-chemical calculations of hexane reactions in Mn(III)/Mn(II)–H2SO4 solutions showed that the most favorable are the electron abstraction by manganese(III) and subsequent proton transfer or homolysis of the C–H bond under the action of bisulfate radical, which is likely formed in the oxidation of sulfuric acid by manganese(III).

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Oxidative Functionalization of Methane on Heterogeneous Catalysts

Cited by 2 publications

References 151 publications

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Activation of C–H bonds of normal alkanes in sulfuric acid solutions of Mn(III)/Mn(II)

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