The Catalyst Review September 2017 - 10

SPECIAL FEATURE
Emerging Technologies for Methane Cultivation

Figure 11. Methane activation technologies.

Several recent reviews address the topic of methane activation (Wang et
al. 2017; Horn and Schlogl 2015; Taifan and Baltrusaitis 2016; Schwach et
al. 2017). Figure 11 illustrates the activities in research and commercial
practice. Similarly, Horn and Schlogl (2015) reviewed methane conversion
to synthesis gas through different reforming steps, and one-step conversion
of methane into chemicals, including: 1) oxidative coupling to ethylene
mediated by oxygen and sulfur; direct oxidation to formaldehyde and
methanol; 2) halogenation and oxyhalogenation to methyl chloride and
methyl bromide; and 3) non-oxidative aromatization to aromatics. Readers
interested in recent development of methane activation technologies can
explore these reviews for further information.

Source: Wang et al. (2017)

From syngas by methane reforming-the only commercially
available methane activation technology-we can see that
methane activation does not simply require a good catalyst,
but also needs to overcome a strong endothermic reaction, as
methane is the most stable hydrocarbon. Several technologies
may be more promising and could bring the gas-based chemical
complex into a more competitive position.

Figure 12. Topsøe MTG and STG.

Haldor Topsøe STG Technology
The Haldor Topsøe STG technology (Topsoe 2017) combines the
syngas to methanol and methanol to gasoline processes into one
step, where the methanol is formed and consumed in situ without
need of further separation. It shortens the process steps, eliminates
the methanol purification step, and improves the process economics.

Source: Topsøe (2017)
Figure 13. Syngas to olefin
catalyst performance.

Selective Syngas to Light Olefins
The selective syngas to light olefins technology (Jiao et al. 2016) combines the syngas to methanol
and methanol to olefins processes, where the methanol is formed and consumed in situ without
need of further separation. This technology is more challenging, as desired product olefins are very
active. The success of this technology will make syngas to olefins more attractive, especially making
Chinese coal to olefins (CTO) technology more competitive in the olefin market.
Oxidative Coupling of Methane (OCM)
OCM has reached the level of pilot demonstration with the catalyst breakthrough by Siluria
Technologies. This is a significant advancement for OCM technology towards a commercially
Source: Jiao et al. (2016)
ready stage. Farrell et al. (2016) summarized the OCM catalyst development history in
Figure 14, and pointed out that the desired ethylene product is not thermodynamically favorable in
the reaction and that further improvements are needed. Currently, the recovery
Figure 14. OCM conversion of methane
and selectivity to C2 products.
of COx formed during the OCM reaction is an important step in overall process economics.
Alkane Substitution by Halogens
In contrast to typical methane activation by oxygen to form syngas, methane can be
activated by halogens (mostly chlorine and bromine) through a substitution reaction.
The substitution reaction is a mildly exothermic and lower temperature reaction,
suggesting lower capital cost in methane activation. The technology has potential if
the used halogen can be effectively recycled and managed. GTC Technology has a
GT-G2A process utilizing bromine as an activating agent. The simplified scheme is shown
in Figure 15. As seen in Figure 11, halogenation and oxyhalogenation have an operating
temperature below 600 oC. Lower temperature operation will reduce the energy intensity
and therefore make the process more competitive.

Source: Farrell et al. (2016)

The Catalyst Review

September 2017

The Catalyst Review September 2017

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