Non-oxidative coupling of methane catalysed by supported tungsten hydride onto alumina and silica–alumina in classical and H2 permeable membrane fixed-bed reactors

Abstract

Non-oxidative coupling of methane with high selectivity into ethane (>99% among hydrocarbon) in a classical fixed-bed reactor catalysed by SiO(2)-Al(2)O(3) or gamma-Al(2)O(3) supported tungsten hydride is presented. Continuous hydrogen separation, using a Pd-Ag membrane in a fixed-bed reactor, led to methane coupling far beyond the thermodynamic equilibrium conversion.

Coupling of Methane to Ethane, Ethylene, and Aromatics over Nickel on Ceria–Zirconia at Low Temperatures

“…To improve the conversion to an acceptable level for industrial application without increasing the operating temperatures,t hese catalysts could be incorporated into membranes that can selectivity remove hydrogen to drive the reactioni n the forward direction.S everal studies in the literature have successfully demonstrated the use of such membranes on systems with either catalysts that are significantly more expensiveo r not as active as the catalyst in this study or for non-oxidative methane aromatization at high temperatures (700-800 8C). [27,65]…”

“…[17,23] An alternative strategy is the production of higherh ydrocarbons from methane in the absence of oxygen, the so-called non-oxidative coupling of methane (NOCM). [2,[24][25][26][27] Since there is no oxidizing agent in this reaction, over-oxidation is not an issue, and ah igh selectivity to C 2 + hydrocarbonsc ould be attained. However,t his reaction is thermodynamically limited because it is missingt he coupled oxidation reactiona sadriving force.…”

“…Various attempts to accomplish the NOCM reactionu sed classical and sometimes ill-defined heterogeneous catalysts in multistep processes:1 )methane dissociation on Ru or Pt particles by chemisorption (and stepwise surface carbon-carbon bond formation);a nd 2) liberation of products by hydrogenation. [25,27] Owing to the thermodynamic constraints of NOCM, a Methane is converted over nickel on ceriaz irconia (Ni/CZ)i nto ethane, aromatics, and hydrogen at steady state up to the thermodynamic limit at temperatures of 350 to 500 8C. At 450 and 500 8C, traces of ethylene are also produced.…”

Alkylidene and alkylidyne surface complexes: Precursors and intermediates in alkane conversion processes on supported single-site catalysts

“…Such processes are also related to alkane metathesis, and are likely to involve alkylidene intermediates. To date, these include: (i) methane/ propane cross-metathesis (Scheme 11a) [116], (ii) cross-metathesis of aromatics with alkanes (Scheme 11b) [117], (iii) non-oxidative methane coupling (Scheme 11c) [118,119]and (iv) non-oxidative coupling of methane and benzene (Scheme 11d) [120].…”

“…The mechanism could be related to that of alkane metathesis, based either on the one or two-sites cycle (vide supra, Schemes 8 and 9). Additionally, non-oxidative methane coupling (Scheme 11c) is catalysed by tantalum [118] or tungsten [119] hydrides, under higher temperature and pressure conditions (from 300 C and 50 atm, cf. propane metathesis: 150 C at 1 bar), and leads to an equimolar mixture of ethane and hydrogen by non-oxidative coupling.…”