Patent US2963348
Linked above and attached, you will find US Patent Number 2,963, 348; for a "Hydrocarbon Conversion Process", that was issued and assigned to "Texaco Development Corporation" on December 6, 1960.
Some informative excerpts:
"This invention relates to a method and apparatus for the conversion of hydrocarbons ... it is directed to the conversion of sulfur-containing carbonaceous fuels to high Btu gas and elemental sulfur to generate a synthesis gas ... .
Heretofor, sulfur-containing fuels have been considered unsatisfactory for conversion to high Btu gas ... because of the tendency of sulfur to poison the catalyst used in the methanation step.
In this invention, the problem of sulfur poisoning ... has been overcome and ... the sulfur is separated as a useful product.
The process of this invention is applicable to ... coal of various grades ... .
An advantage of this invention is that carbonaceous fuels containing ... sulfur may be readily converted into high Btu value heating gases."
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Gases, we would submit, that, as in the phrase "to generate a synthesis gas", above, could then be passed over a Fischer-Tropsch, or similar, catalyst for further conversion and condensation, for "synthesis", into low-sulfur, "high Btu value" liquid fuels.
In 1960, Texaco, based on knowledge of the German and Japanese WWII synthetic coal-to-liquid fuel operations, would have been aware of that.
This patent is not just a technology for producing substitute natural gas, SNG, from coal. It is a patent on technology that refines a step in the overall coal conversion process, whether the end product is to be SNG, or, after Fischer-Tropsch catalysis, synthetic liquid fuels. This technology removes sulfur from a Coal conversion process so that the end product, whether substitute gas or synthetic gasoline, will be cleaner.
And, a by-product with commercial value, Sulfur, is recovered.