(434h) Direct Coupling of Bromine-Mediated Methane Activation and Coal Gasification: Albr3 Assisted Conversion of Methyl Bromide to Light Hydrocarbons and Quantitative Catalyst Regeneration

Bromine mediated methane activation has been proposed as a possible route to large scale hydrocarbon production from methane but suffers from long-term catalyst instability and corrosion problems associated with methyl bromide, free bromine and hydrogen bromide [1] The process could in principle make extensive use of the selective mono-bromination of methane (>99 %) as discovered by G. Olah in 1985 [2] and may use methyl bromide as a first intermediate before conversion to higher hydrocarbons (see below).

In order to overcome these limitations, we have investigated the use of a completely oxide, oxygen or water free system as to reduce chemical transport of oxide catalysts and corrosion. Catalyst instability was inherently removed by applying a homogeneous alternative, AlBr3. This highly active system allowed conversion of methyl bromide at very low temperature (180 to 210 °C) enabling the broader use of fluorocarbons for reactor lining and overcomes the corrosion problem. The absence of any oxide catalysts removes chemical transport of partially volatile constituents, re-deposition and deactivation. Volatile aluminium bromide is fully stable can be fully regenerated.

The inherent formation of carbonaceous deposits during conversion of methylen equivalents (CH3Br = -CH2- + HBr; also MeOH) was integrated into the process by direct conversion of the deposits into the desired range of products. The process therefore avoids carbon loss due to coke burn-off and results in competitive product yields [3].

The results are discussed in terms of possible large-scale implementation and estimated energy requirements.

References:

[1] I. Lorkovic, M. Noy, M. Weiss, J. Sherman, E. McFarland, G.D. Stucky, P.C. Ford,C1 Coupling via bromine activation and tandem catalytic condensation and neutralization over CaO/zeolite composites, Chem. Commun. 2004, 566 – 567.

[2] G. A. Olah, B. Gupta, M. Farina, J. D. Feldberg, W. M. Ip, A. husain, R. Karpeles, K. Lammertsma, A. K. Melhotra, N. J. Trivedi, Journal of the American Chemical society 1985, 107, 7097.

[3] Neil Osterwalder and Wendelin J. Stark, European Patent Application EP 06 005 927.6 and US provisional application 2006.