Oxidative halogenation of C1 hydrocarbons to halogenated C1
Simon G. Podkolzin, Eric E. Stangland, Albert E. Schweizer, Mark E. Jones
Assigned to Dow Global Technologies Inc., Washington Street, 1790 Building,
Midland, MI 48674 USA
International Application: PCT/US2006/015993; International Filing Date:
25.04.2006; IPC: C07C 17/154 (2006.01)
An oxidative halogenation process involving contacting
methane, a C1 halogenated hydrocarbon, or a mixture thereof with a
source of halogen and a source of oxygen, at a molar ratio of reactant
hydrocarbon to source of halogen in a feed to the reactor greater than 23/1,
and/or at a molar ratio of reactant hydrocarbon to source of oxygen in a feed
to the reactor greater than about 46/1; in the presence of a rare earth halide
or rare earth oxyhalide catalyst, to produce a halogenated C1
product having at least one more halogen as compared with the C1
reactant hydrocarbon, preferably, methyl chloride. The process can be
advantageously conducted to total conversion of source of halogen and source
of oxygen. The process can be advantageously conducted with essentially no
halogen in the feed to the reactor, by employing a separate catalyst
halogenation step in a pulse, swing or circulating bed mode. The production of
methyl halide can be integrated into downstream processes for manufacture of
valuable commodity chemicals.
Evolution of feed and product component traces
monitored by a mass spectrometer in pulse experiments.
When a pulse of CH4+O2
is introduced over a chlorinated lanthanum catalyst, a mixture of CH3Cl
and H2O is produced. These kinetic pulse experiments show that a gas-phase source of chlorine is
not necessary for the reaction, and chlorine can be supplied by the
Effect of removing a source of chlorine (HCl) from the
feed stream for oxidative hydrochlorination of methane:
0.5 O2 + HCl = CH3Cl + H2O
Although the reaction
rate decreases without HCl, the catalyst can sustain the chlorination
reaction for a significant period of time. In addition, the selectivity in
methane activation increases to practically 100% in the absence of HCl.
|Results of reaction mechanism studies were used for optimization
of reaction conditions :
- High methane
ratios improve selectivity. Practically 100% selectivity can be achieved
at high methane to oxygen ratios.
- Reaction can be conducted with 100%
conversion of HCl, while maintaining high selectivity to CH3Cl.
This can eliminate expensive HCl and H2O separation.
- Methane activation can be operated in a
swing, alternating feed or pulse mode: pulses of CH4+O2
can be alternated with pulses of HCl. This can simplify separations and
Possible alternating feed reactor operation.
Flow scheme of an integrated process for converting
natural gas into higher hydrocarbons.
Selective methane chlorination can be a part of an
integrated process for conversion of natural gas to higher hydrocarbons.
In the first step, methane is reacted with HCl and O2 and
selectively converted into a CH3Cl intermediate over a
chlorinated lanthanum catalyst. In the second step, the CH3Cl
intermediate is reacted over a zeolite catalyst to produce hydrocarbons
and to regenerate HCl. The recovered HCl is recycled to the first
In this process, three is no net consumption or
production of chlorinated products. Oxidative chlorination in this flow
scheme is used only as a means of selective methane activation, and the
overall reaction is equivalent to that of oxidative methane coupling:
2 CH4 + O2 = C2H4
+ 2 H2O
Reaction mechanism studies of oxidative methane
hydrochlorination are described in
the 2007 paper by Simon Podkolzin et al.
in the Journal of the American Chemical Society.
Go to previous or next publication summary