The Coal and Methane conversion process described herein by Mobil Oil, around which we center our discussion, deserves a far better exposition than the US Patent itself, even with it's full Disclosure, provides.
In brief sum, and as opined for us by one of our fully-functioning consultants, Mobil is replacing Oxygen, in "partial oxidation" reactions, with Sulfur, Oxygen's close relative in the Periodic Table of Elements, and, thus, somewhat similar to Oxygen in the way it chemically interacts with other substances.
Partial oxidation is key to the process of generating hydrocarbon synthesis gas from Coal. And, similar processes - - which we haven't dwelled much upon in our reports, although they are related to the various Carbon Dioxide-Methane "reforming" technologies we have documented - - can be applied to Methane.
Furhermore, Sulfur, so closely related to Oxygen, will react with other elements and compounds in much the same way Oxygen does; but, with a slight difference.
Being a "larger" atom to begin with, Sulfur doesn't "bind", for reasons beyond our fathoming, to other elements quite as strongly or tightly as does Oxygen.
Thus, when we form compounds such as Carbon Disulfide and Hydrogen Sulfide (H2S), it's easier, it requires less energy and effort, to get the Carbon and Hydrogen "out" of them, for subsequent recombination with each other, to form hydrocarbons, than it does to get the Carbon and Hydrogen out of the corollary compounds, Carbon Dioxide and Water (H2O).
And, consequently, Sulfur can be removed almost entirely from the reactants, while some Oxygen, on the other hand, bound so tightly, always "clings", and goes along for the ride in subsequent processing steps.
Sulfur can thus be thought of as a more efficient chemical "conduit" for Carbon and Hydrogen; a means of conveying them into hydrocarbon-synthesizing reactions.
So, an additional benefit is, that, since little or no Oxygen is passed through the subsequent catalytic reactions that form the desired end-product hydrocarbons, the "energy density" of the products is improved. Fewer "oxygenated" hydrocarbons, i..e, alcohols, with their somewhat lower energy content, are formed.
Furthermore, and perhaps importantly, somewhat less of the original Carbon is lost via complete oxidation into less-reactive Carbon Dioxide, though some CO2 is formed during one or two of the necessary reactions.
In essence, Mobil proposes that Sulfur can be reacted with Coal and with Methane, and be thereby made to form Carbon Sulfide(s) and Hydrogen Sulfide, which compounds are then more easily broken down into their elemental constituents than are their Oxygen-based correlatives, i.e.: Carbon Monoxide, Carbon Dioxide and Water. And, the elements, Carbon and Hydrogen, can then be more readily recombined into the desired Hydrocarbons, while Sulfur is recovered and recycled back into the system to process more Coal and more Methane.
As a consequence, far less of the available Hydrogen is, thus, "lost" in the formation of H2O during the reactions; and, in fact, so much Hydrogen becomes available that it can be produced in excess, be made almost as a by-product, which has some additional implications related to the productivity of the system.
We think it's all pretty slick; and, it does relate to other, similar, Sulfur-based and Sulfur-facilitated Carbon conversion technologies we have documented a few times previously.
As we explain, in comments following excerpts from the initial link in this dispatch to:
"United States Patent 4,543,434 - Process for Producing Liquid Hydrocarbon Fuels
Date: September, 1985
Inventor: Clarence Chang, NJ
Assignee: Mobil Oil Corporation, NY
Abstract: A process for the synthesis of liquid hydrocarbon fuels and hydrogen based on the use of sulfur as an oxidant.
Claims: A catalytic process for converting coal to a liquid hydrocarbon fuel and hydrogen mixture comprising the sequential steps of:
(a) contacting said coal with sulfur thereby forming a product comprising carbon disulfide;
(b) contacting the carbon disulfide with water thereby forming a product comprising a carbonyl sulfide fraction and a hydrogen sulfide fraction;
(c) disproportionating the carbonyl sulfide fraction into a product comprising carbon dioxide and carbon disulfide, and removing the carbon disulfide as a separate product;
(Note: We're told that "disproportionating" is just college-boy speak for saying that, in essence, they're making two things at once from the same reaction using the same raw materials.)
(d) hydrogenating the carbon disulfide (as specified) and separating the reaction product into a hydrogen sulfide fraction and as a desired product a hydrocarbon fraction;
(e) contacting said hydrogen sulfide fraction of with one or more metals selected from the group consisting of Group VI-B and Group VIII metals thereby forming a metal sulfide and hydrogen ...; and: recovering said metal sulfide ... and thermally decomposing it ... into a metal and elemental sulfur.
(Note: There is nothing exotic about "Group VI-B and Group VIII metals". They would include such things as Molybdenum and plain old Nickel, whose value as hydrogenation and hydro-treating catalysts has been known and exploited to great good effect by the petroleum industry for many, many decades. A bit more about them could be learned via: "United States Patent: 4596785; Group VIII and VIB Metal Sulfide Catalysts, their Manufacture and their Use for Hydrotreating Hydrocarbon Cuts Containing Sulfur"; wherein we learn that such VI-B and VIII catalysts "are active for all possible reactions between hydrogen and a hydrocarbon mixture containing sulfur compounds, and in particular, ... hydrogenation, hydrodesulfuration, hydrodenitrogenation, (and) hydrocracking.")
(And) A catalytic process for converting ... methane to a liquid hydrocarbon fuel mixture and hydrogen comprising (a set of reactions closely-similar to those employed for Coal).
Background and Field: The invention disclosed and embodied herein relates to the synthesis of liquid hydrocarbon fuels and hydrogen from coal or (methane) or related materials.
The invention further relates to a thermochemical cycle based on the use of sulfur as an oxidant, the recovery of sulfur and hydrogen from by-product hydrogen sulfide and to a process wherein said synthesis is carried out in the presence of a ZSM-5 type catalyst.
(Note: We have many times documented ExxonMobil's "MTG"(r), methanol-to-gasoline, technology, which utilizes "a ZSM-5 type catalyst", and, wherein the Methanol is posited to be made from Coal. Additional reports concerning that technology are in process, but, for current reference and explanation, we suggest:
ExxonMobil "Clean Gasoline from Coal" | Research & Development; and, perhaps more specifically and especially:Mobil Oil Coal to Methanol to Gasoline | Research & Development, which addresses specifically:
"United States Patent: 4447310 - Production of Distillates ... Through Methanol to Gasoline; 1984; Assignee: Mobil Oil Corporation; Abstract: A process for producing a wide slate of fuel products from coal is provided by integrating a methanol-to-gasoline conversion process with coal liquefaction and coal gasification. The coal liquefaction comprises contacting the coal with a solvent under supercritical conditions whereby a dense-gas phase solvent extracts from the coal a hydrogen-rich extract which can be upgraded to produce a distillate stream. The remaining coal is gasified under oxidation conditions to produce a synthesis gas which is converted to methanol (which) is converted to gasoline by contact with a zeolite catalyst ... said zeolite catalyst (being) ZSM- 5.")
It is known that aliphatic organic compounds containing oxygen, sulfur, nitrogen and/or halogen constituents may be converted to aromatic hydrocarbons in commercially desirable yields in the presence of zeolites ... .
It is also known that synthesis gas, i.e., mixed carbon monoxide and hydrogen, can be catalytically converted into liquid hydrocarbon fuels such as gasoline boiling range products.
Coal (is one) of the raw materials used to provide materials for hydrocarbon conversion but to applicant's knowledge heretofore such technology unlike the present invention has used oxygen rather than sulfur as the oxidant.
Summary and Description: A novel process for the synthesis of liquid fuels from methane or natural gas, coal and/or related materials is disclosed herein. Further, an economical means of producing hydrogen is also provided. The aforementioned process offers an attractive alternative to prior art methods of coal gasification and CH4 (methane) steam reforming.
Liquid hydrocarbon fuels and H2 are co-produced according to the novel (process of this invention from Coal and/or Methane)."
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First, since we mentioned our previous reports of the utility of H2S, we remind you of just one of them, as in:
Exxon Methane and Hydrogen from H2S and Carbon Monoxide | Research & Development; concerning: "United States Patent 4,517,171 - Synthesis of H2 and CH4 from H2S and CO; 1985; Assignee: Exxon Research and Engineering Company, NJ; Abstract: Hydrogen and methane are synthesized from a gaseous feed comprising a mixture of H2S and CO"; wherein it's seen that Hydrogen Sulfide can enable the synthesis of Methane and even more Hydrogen when it's mixed with Carbon Monoxide, which can, for example, as seen in:
1915 CO2 Recycling | Research & Development | News; concerning: "US Patent 1,163,922 - Producing Carbon Monoxid from Carbon Dioxid; 1915; Abstract: This invention relates to the production of carbon monoxid (CO) gas (by) mixing powdered carbon and carbon dioxid (CO2) gas under sufficiently high temperature to cause a carbon molecule to combine with one of the oxygen elements of the CO2, resulting in 2CO";
be produced by reacting red-hot Coal with Carbon Dioxide.
Then, since Methane can be utilized to such good effect, with Coal, in the production of "hydrocarbon fuels and H2", via the process herein of "United States Patent 4,543,434", we remind you of:
Penn State Solar CO2 + H2O = Methane | Research & Development | News; wherein we're told by scientists at Penn State University, in their report "High-Rate Solar Photocatalytic Conversion of CO2 and Water Vapor to Hydrocarbon Fuels", that we can, using Solar energy to drive the process, effect the "conversion of carbon dioxide and water vapor to methane".
And, then, since molecular hydrogen, "H2", is a by-product, with the liquid hydrocarbons, of the process herein of Mobil's "United States Patent 4,543,434", we remind you as well, that, as in:
Sabatier reaction - Wikipedia, the free encyclopedia; "The Sabatier process ... involves the reaction of hydrogen with carbon dioxide ... to produce methane and water";
we could use that Hydrogen to make more Methane, out of Carbon Dioxide; and, we could recycle that Methane back into the process of "United States Patent 4,543,434", or, we could employ the Methane, as for one instance seen in:
Exxon 2010 CO2 + Methane = Liquid Hydrocarbons | Research & Development; concerning: "United States Patent 7,772,447 - Production of Liquid Hydrocarbons from Methane; 2010; Assignee: ExxonMobil; Abstract: (A) process for converting methane to liquid hydrocarbons ... comprising: contacting a feed containing methane and ... H2O (and) CO2 with a (specified) catalyst under conditions effective to convert said methane to aromatic hydrocarbons, including benzene and naphthalene, and produce a first effluent stream comprising aromatic hydrocarbons and hydrogen";
to recycle even more Carbon Dioxide, with the concurrent production of even more Hydrogen, which additional Hydrogen we could then, perhaps, direct into a process such as explained in:
WVU Hydrogenates Coal Tar | Research & Development; concerning: "Hydrogenation of Naphthalene and Coal Tar Distillate; West Virginia University; 2009; Abstract: The hydrogenation of naphthalene and coal-tar distillates (to form) the hydrogenated product, tetralin ... (and, wherein) coal was hydrogenated ... using (tetralin) as the solvent";
and thereby produce, perhaps from the Naphthalene generated by reacting Methane with Carbon Dioxide in that ExxonMobil process of "United States Patent 7,772,447", the Coal hydrogen-donor solvent, "tetralin", specified by WVU in their "West Virginia Process" for the direct liquefaction of Coal.