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An Approach Using Oxidative Coupling of Methane for Converting Biogas and Acid Natural Gas into High-Calorific Fuels
journal contribution
posted on 2018-10-09, 00:00 authored by Sergey Sokolov, Dominik Seeburg, Sebastian Wohlrab, Markus Friedel, Jörg Nitzsche, Evgenii V. KondratenkoBiogas
is a renewable
resource with prospects in production of
commodity chemicals or for power generation. The latter implies co-usage
of biogas and natural gas in gas distribution nets but puts a restriction
on the higher heating value (HHV) of all gases pumped into the net.
In this contribution, we analyzed and experimentally validated the
potential of the oxidative coupling of methane (OCM) as a method for
upgrading biogas HHV. The effects of the reaction conditions, i.e.,
reaction temperature, feed CH4/O2 ratio, and
co-feeding of CO2 or H2O, on HHV of the resulting
gas mixtures were studied. The highest HHV of 11.48 kW·h·m–3 after water condensation was obtained when performing
the OCM reaction over Mn–Na–WOx/SiO2 catalyst at 800 °C using a feed with
CH4/O2 ratio of 12 and 30 vol% water. This performance
was possible thanks to 86% selectivity to C2 hydrocarbons
(C2H4 and C2H6) at 15.2%
methane conversion. It was also possible to increase the selectivity
to 100% when carbon oxides formed in the OCM reaction were hydrogenated
to methane in a separate reactor containing a Fe2O3 catalyst and thus to obtain a gas mixture with HHV of 12.0
kW·h·m–3. Such combined approach can open
an environmentally friendly way for upgrading biogas or natural gas
with high CO2 content for direct applications in gas distribution
nets when using green source of energy for H2O splitting
to H2 and O2 required for the OCM and hydrogenation
reactions, respectively.