We have thoroughly documented that Methanol can be extracted from coal, and from carbon-recycling cellulose; and, as in Sabatier reactions, it can be synthesized from Carbon Dioxide, via methane.
We have also documented that, once obtained, Methanol can be further converted into gasoline, and a variety of organic chemicals useful as raw materials in the manufacture of plastics. One such notable technology, about which we have reported, is ExxonMobil's "MTG"(R), methanol-to-gasoline, process.
We have also reported on the coal gasification technology available from Germany's Lurgi AG, and it's applicability to commercial coal conversion industries.
Herein, according to Volkswagen, Lurgi has put the technologies together and developed it's own, "MTS", or "MtSynfuels"(R), methanol-to-synfuels, process.
Lurgi AG develops a process called MTSynfuels(R) (Methanol-to-Synfuels). Like Fischer-Tropsch-Processes (FT), the process is designed to produce liquid fuels from synthetic gases.
("Fischer-Tropsch" should by now be familiar to all our readers; and, the "synthetic gases" would, it should now go without saying, but say it we will, be produced from coal, among other things.)
The production of syngas and the synthesis of methanol
Like the FT process, syngas is the starting material for the MtSynfuels(R) process, which can be produced from various fossil fuels and renewable raw materials. The syngas must meet the same purity requirements and have the same composition (i.e. H2/CO = 2) as is usual for FT synthesis. The subsequent conversion of syngas to methanol is exothermic, as in the following reactions:
CO + 2 H2 –> CH3OH
CO2 + 3 H2 –> CH3OH + H2O
CO + H2O –> CO2 + H2
The methanol synthesis variant developed by Lurgi works at pressures of 50 - 100 bar and at temperatures between 220°C and 280°C with a Cu-Zn-Al2O3 catalyst.
(We submit that "a Cu-Zn-Al2O3 catalyst" would be a zeolite-type mineral similar to the zeolite used by ExxonMobil in their own "MTG"(R), Methanol-to-Gasoline, technology.)
The production of olefin
In the MtSynfuels® process the methanol is then catalytically converted to DME (Dimethylether) like this
2 CH3OH –> DME + H2O
and then into hydrocarbons e.g. to
DME –> 2/3 C3H6 + H2O
The zeolitic catalyser used for this step has a high selectivity for olefins. The conversion occurs at temperatures between 300°C and 550°C and at pressures between one and 20 bar.
(The processing temperature might seem high. But, the "conversion of syngas to methanol is exothermic", so heat generated by the reaction might be used to help to reduce needs for added energy; and, thus, increase efficiency and reduce costs. Also, note mention of "DME", which, as we have earlier documented, is a versatile liquid fuel and chemical manufacturing feed stock in it's own right.)
The oligomerisation of olefin
The product mixture from the methanol conversion is then fed to the next reaction level, where short-chain olefins are built up to larger molecules. For example:
4 C3H6 –> C12H24
This reaction occurs at temperatures between 150°C and 350°C and at pressures between 35 and 85 bar, using a zeolitic catalyser. The oligomerised products in the area of C10+ are separated by distillation from the product mixture and hydrogenated. The resulting flow directly represents the diesel product of the MtSynfuels® process. Apart from that, during the distillation, a low-molecular gasoline product containing paraffin and aromatics is separated. For the two main products diesel and gasoline a total yield of > 90% (relating to carbon) is specified, whereby the ratio of diesel to gasoline can vary over a wide range. LPG (C3/C4) and light ends (C1/C2) are produced as by-products and water is also produced from the methanol conversion process.
Lurgi gives the energy efficiency of the process chain of 67% as an advantage over the FT path (< 63%). The overall efficiency, including all operating materials, is however about the same for both paths. The gasoline product from the MtSynfuels(R) process has a significantly better quality than the gasoline-like by-product of an FT systhesis."
We're glad they improved the efficiency of the process, relative to "the FT path".
But, either way, you get gasoline from syngas; and, you get syngas from ... Coal.
