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PROCESS & TECHNOLOGY FOR METHANOL AND DME

The methane formation is highly exothermic, while methanol formation is mildly exothermic
but carbon monoxide formation is mildly endothermic. Also all these reactions are equilibrium
controlled.
For methanation of carbon dioxide large numbers of catalysts are reported in the literature
and Ni on silica is most widely studied. Several other catalysts are also reported such as VIIIB
metals (e.g., Ru and Rh) supported on various oxides (e.g., SiO , TiO , Al O , ZrO , and CeO )
2
2
2
3
2
2
[141].
The conversion to carbon monoxide is actually reverse of Low Temperature Shift reaction.
Therefore, the catalyst system is very similar to LTS based on Cu/Zn. Many new catalysts
are reported in literature which includes nickel, Noble metals etc. Raney nickel is also an
active catalyst for hydrogenation and appears to have high reactivity for methanation reaction.
This reaction can also be speeded up by electrochemical route. Recently, Brookhaven
National Laboratory announced a process using ionic liquid to speed up this reaction using
the commercial catalysts. [142]. Due to its endothermic nature, reaction is favoured at high
temperature.

Methanol formation produces heat during the transformation. Decrease in reaction temperature
and increase in reaction pressure favours this hydrogenation reaction. Typically, catalysts used
in CO hydrogenation are those for methanol synthesis from CO hydrogenation. Large numbers
2
of catalysts are reported in the literature using Cu, Zn, Gallium, Palladium, Zirconium etc on
Silica support. Noble metal catalysts are also reported. Due to its importance, development
of more efficient catalyst is actively pursued by many research groups around the world. It is
also possible to carry out this reaction in liquid phase as in carbon monoxide hydrogenation
at lower pressure. Direct conversion to DME is possible by using a dual function catalyst by
incorporating acid function through addition of H ZSM 5 in conventional methanol catalyst. An
extensive review is published in the Journal of Royal Society of Chemistry, Chem. Soc Review
during 2011 by Wei Eang et.al on the recent developments on catalyst for carbon dioxide
hydrogenation. [141]
CRI has been very active in this area and they have set up similar plant for methanol in
Iceland with hydrogen from geothermal source. The process uses solid copper and zinc oxide
catalysts operates at 250 C and 100 atmosphere pressure. The technology may be available
0
from them. [101]
This route practically depends on the availability of cheap renewable hydrogen. The simplest
way for getting hydrogen is from electro splitting of water. A recent estimate of investment and
production cost for electricity from different routes clearly shows that geothermal energy is by
far the cheapest carbon free electricity. The cost of geothermal energy is almost 50% lower
than any other route [143]. Therefore, the success depends only on availability of geothermal
energy near carbon dioxide source.
A recent computation study indicates that there is a possibility of utilizing the available hydrogen
in ammonia plants to convert to methanol/DME by using carbon dioxide. This could reduce the
carbon footprint without much penalty [56]. The hydrogen from Chlor Alkali industry could be
captured for carbon dioxide reforming. These are possible small scale options to reduce carbon
emission from fossil fuels [57]. The same is true with hydrogen from steel plant or refineries.

44 Methanol and DME Production: Survey and Roadmap | 2017