Methyl Chloride Production from Methane over Lanthanum-Based Catalysts

Abstract

Abstract:The mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methane activation proceeds through oxidation-reduction reactions on the surface of catalysts with an irreducible metal-lanthanum, which is significantly different from known mechanisms for oxidative chlorination. Activity and spectroscopic measurements show that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with an intermediate extent of chlorination are all active for this reaction. The catalyst is stable with no noticeable deactivation after three weeks of testing. Kinetic measurements suggest that methane activation proceeds on the surface of the catalyst. Flow and pulse experiments indicate that the presence of hydrogen chloride is not required for activity, and its role appears to be limited to maintaining the extent of catalyst chlorination. In contrast, the presence of gas-phase oxygen is essential for catalytic activity. Density-functional theory calculations suggest that oxygen can activate surface chlorine species by adsorbing dissociatively and forming OCl surface species, which can serve as an active site for methane activation. The proposed mechanism, thus, involves changing of the formal oxidation state of surface chlorine from -1 to +1 without any changes in the oxidation state of the underlying metal.

A DFT based equilibrium study on the hydrolysis and the dehydration reactions of MgCl2 hydrates

“…6). This method is, successfully, applied for studying molecular systems involving magnesium, 7 chlorides, 33,34 and hydrogen bonds. 35 A spinrestricted Kohn-Sham method is used with a doubly polarized triple-ζ basis set, while keeping the integration accuracy to the maximum throughout the calculation.…”

Structure and phase analysis of one-pot hydrothermally synthesized FePO4-SBA-15 as an extremely stable catalyst for harsh oxy-bromination of methane

“…FePO 4 -SBA-15 (OP) was directly synthesized via a one-pot hydrothermal technique, using Fe(NO 3 ) 3 and H 3 PO 4 as the precursors. FePO 4 /SBA-15 (IMP) was also prepared as a reference, using an impregnation method and commercially available SBA-15 as the support.…”

“…Photochemical or thermal halogenation of hydrocarbon with halogen is known as a free radical chain process and lacks selectivity. Many interesting works [1][2][3][4] have been carried out to improve the selectivity of methyl halide. However, halogens are highly corrosive to equipment and dangerous to handle which present a big trouble for the industrialization.…”

“…In view of halogen corrosion, methane oxidative bromination [5][6][7][8] and chlorination [9] were studied which use hydrobromic acid or HCl as reactants instead of halogens to reduce corrosion problem. Zhou et al [5,6,10] firstly reported methane oxidative bromination (OBM) reaction and developed Ru-and Rh-containing catalysts which showed high selectivity for CH 3 Br and excellent stability, but the uses of noble metals raise the production cost. We also reported FePO 4 /SiO 2 [8] for the OBM reaction, producing nearly equal-molar CH 3 Br and CO which could be used as feed stock for producing acetic acid.…”

Demonstration of CO2 Conversion to Synthetic Transport Fuel at Flue Gas Concentrations

“…With CDU processes in mind, the two obvious candidates for the starting hydrocarbon and alcohol shown in Figure 3 would be methane and methanol, both readily synthesized by the hydrogenation of CO2 (Figure 4) (Mikkelsen et al, 2010;Saeidi et al, 2014). The selective formation of methyl halide from the reaction of methane and the elemental halogen is somewhat challenging, due to the higher reactivity of the products than starting materials, although appropriate choice of rare-earth or precious metal catalyst can yield the desired product (Olah et al, 1985;Podkolzin et al, 2007). By comparison, the conversion of methanol into any of the methyl halides is rather trivial using the hydrogen halide to carry out nucleophilic substitution.…”