The primary subjects of this dispatch are two, rather enormously complex, United States Patents issued just last year to scientists in the employ of our beloved oily behemoth, ExxonMobil.
The central object of both disclosed technologies, so closely related that we can't fathom the reason why two separate patents were issued, is the conversion of Methane into liquid hydrocarbons, primarily those that comprise the basic Gasoline blending stock often shorthanded as "BTX", i.e., Benzene, Toluene and Xylene.
And, though not necessarily highlighted or emphasized by ExxonMobil, though we will, through our excerpts, make certain the point is made clear, is the fact that such conversion of Methane into, essentially, Gasoline, is effected by reacting Methane with, among other, but non-essential, possibilities, Carbon Dioxide.
And, before we proceed, allow us to remind you where we might, in the first place, get the Methane.
As demonstrated, for just one instance, in:
1975 Texaco Methane from Coal | Research & Development; concerning: "USP 3928000 - Production of a Clean Methane-rich Fuel Gas from High-sulfur Containing Hydrocarbonaceous Materials; 1975; Assignee: Texaco, Inc. New York; Abstract: (An) improved process for converting low-cost high-sulfur containing hydrocarbonaceous materials into a clean methane-rich gas ... . (A) process for producing a methane-rich gas comprising CH4 ... from a sulfur-containing ... fuel such as ... coal";
we can make all of the Methane we might want out of pretty much any old impure, and thus-inexpensive, grade of Coal we might have lying around.
Or, as seen, again for just one instance, in:
Penn State Solar CO2 + H2O = Methane | Research & Development | News; which contains the report: "High-Rate Solar Photocatalytic Conversion of CO2 and Water Vapor to Hydrocarbon Fuels; The Pennsylvania State University; 2009; Summary: Efficient solar conversion of carbon dioxide and water vapor to methane ... is achieved";
we can make that Methane, for ExxonMobil's disclosed reactions with CO2, out of CO2.
And, as you will see in our highly-distilled excepts, from the initial and following links, with brief comment and a few other links inserted and appended, ExxonMobil has some intriguing suggestions about where we might get that CO2:
"United States Patent 7,772,447 - Production of Liquid Hydrocarbons from Methane
Date: August, 2010
Inventor: Larry Iaccino, et. al., TX
Assignee: ExxonMobil, Houston
Abstract: (A) process for converting methane to liquid hydrocarbons ... , including benzene and/or naphthalene, and produce a first effluent stream comprising hydrogen ... .
Claims: A process for converting methane to higher hydrocarbons, the process comprising: (a) 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 ... .
(We are absolutely compelled to interject with comment here. Note that both "naphthalene" and extra "hydrogen" are produced. Though further processing is specified for the products, directed to the making of Gasoline blending stock, we submit that some of that Methane- and CO2-derived "naphthalene" could be reacted with some of that co-produced "hydrogen", and be made, as explained in one earlier report:
WVU Hydrogenates Coal Tar | Research & Development | News; concerning: "Hydrogenation of Naphthalene and Coal Tar Distillate; Abhijit Bhagavatula; West Virginia University; (Synopsis:) The hydrogenation of naphthalene ... in a Trickle Bed Reactor (to form) the hydrogenated product, tetralin. Coal-derived liquids have been produced at West Virginia University (WVU) by hydrogenating coal (which) involves the conversion of coal to refinable crude hydrocarbons, from which liquid fuels such as gasoline, diesel, kerosene, etc., can be produced. (Coal) was hydrogenated ... using (tetralin) as the solvent";
to form the WVU-specified Hydrogen-donor solvent, "tetralin", which can then be used to convert Coal, as confirmed by WVU, into "liquid fuels such as gasoline".)
A process for converting methane to higher hydrocarbons and hydrogen
The process ... further comprising reacting at least part of the hydrogen ... with (more) oxygen containing species to produce a further (additional) effluent stream (of) hydrocarbon; wherein said oxygen-containing species comprises carbon monoxide and/or carbon dioxide.
(All those entranced by all of the loose talk and euphoric recent reportage concerning the potentials for fueling cars in WV directly with Marcellus Shale gas should take note of the following.)
A particular difficulty in using natural gas as a liquid hydrocarbon source concerns the fact that many natural gas fields around the world contain large quantities, sometimes in excess of 50%, of carbon dioxide. Not only is carbon dioxide a target of increasing governmental regulation because of its potential contribution to global climate change, but also any process which requires separation and disposal of large quantities of carbon dioxide from natural gas is likely to be economically prohibitive. In fact, some natural gas fields have such high carbon dioxide levels as to be currently considered economically unrecoverable.
There is therefore a need for an improved process for converting methane to liquid hydrocarbons, particularly where the methane is present in a natural gas stream containing large quantities of carbon dioxide.
Summary: In one aspect, this application describes a process for converting methane to higher hydrocarbons, the process comprising: (a) contacting a feed containing methane and at least one of H2, H2O, CO and CO2 with a ... catalyst ... to convert said methane to ... a first effluent stream comprising aromatic hydrocarbons and hydrogen.
Any methane-containing feedstock can be used in the process of the invention ... .
(And, again, as in: Penn State Solar CO2 + H2O = Methane | Research & Development | News, and, as in: 1975 Texaco Methane from Coal | Research & Development; we can make that Methane out of either Coal or Carbon Dioxide.)
In addition ... carbon dioxide can also be converted to useful aromatics products either directly ... or indirectly through conversion to methane and/or other hydrocarbons.
Suitable sources of carbon dioxide include flue gases ... ."
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Folks, let's stop and make that perfectly clear: Methane can be converted to "higher hydrocarbons" by reacting it, in essence, as ExxonMobil directly specifies, with the Carbon Dioxide in "flue gases".
If it's going to take a while for the implications of that to sink in, here's a little more food for thought to pile on top of it:
ExxonMobil almost immediately improved the process, and broadened the scope, of US Patent 7,772,447.
As seen in:
"United States Patent: 7795490 - Production of Aromatics from Methane
Date: September, 2010
Inventor: Larry Iaccino, et. al., TX
Assignee: ExxonMobil, Houston
Abstract: In a process for converting methane to aromatic hydrocarbons, a feed containing methane is supplied to one or more reaction zone(s) containing catalytic material operating under reaction conditions effective to convert at least a portion of the methane to aromatic hydrocarbons ... .
Claims: A process for converting methane to higher hydrocarbon(s) including aromatic hydrocarbon(s) in a reaction zone, the process comprising: providing to said reaction zone a hydrocarbon feedstock containing methane ... .
(And) wherein said feedstock further comprises at least one of CO, CO2, H2, H2O, and/or O2.
(Hold the phone, just a moment, please. And, allow us to remind you of a little more about those "further" components:
As seen in: Pittsburgh & Germany 1940 Coal & Steam to Hydrocarbons | Research & Development; concerning: "United States Patent 2,220,357 - Synthetical Production of Liquid Hydrocarbons; 1940; Assignee: Koppers Company, Pittsburgh, PA"; wherein (Hydrogen and Carbon Monoxide in specified proportions ... are made by) alternate blows of air and ... steam through ... carbonaceous fuel (and) carbon dioxide ... also reacts with the steam; and, in:
Texaco 1950 Coal + Steam = Hydrocarbon Syngas | Research & Development; concerning: "United States Patent 2,516,974 - Gasifying Carbonaceous Material; 1950; Assignee: Texaco Development Corporation, NY"; wherein is disclosed how a "stream of combustible gases, predominantly hydrogen and carbon monoxide" is made "by the reaction of water vapor with" Coal.
we can make any "CO" and "H2" we might need, to combine with "H2O", and with additional "CO2", perhaps recovered from a shale gas cleaning and stripping plant, to add to the "methane" and make such a combined "feedstock" for the process herein, of ExxonMobil's US Patent 7795490, to ultimately make "aromatic hydrocarbons", by using Steam to gasify Coal.)
(And) wherein said catalytic material comprises at least one of molybdenum, tungsten, rhenium, a molybdenum compound, a tungsten compound, a zinc compound, and a rhenium compound on ZSM-5, silica or an aluminum oxide.
Background: Aromatic hydrocarbons, particularly benzene, toluene, ethylbenzene and xylenes, are important commodity chemicals in the petrochemical industry. Currently, aromatics are most frequently produced from petroleum-based feedstocks by a variety of processes, including catalytic reforming and catalytic cracking. However, as the world supplies of petroleum feedstocks decrease, there is a growing need to find alternative sources of aromatic hydrocarbons.
(There) is a need to develop a process for converting methane to higher hydrocarbon(s), which provides high efficiency for heat transfer, adequate hydrocarbon/catalyst contacting, and/or improved process conditions to maximize selectivity to desired higher hydrocarbons, e.g., aromatic compound(s), while minimizing coke formation.
The invention described herein seeks to provide an improved methane aromatization process in which performance is improved by controlling the temperature and composition profile in the reactor system.
Summary: In one aspect, the present invention resides in a process for converting methane to higher hydrocarbons including aromatic hydrocarbons.
As used herein the term "higher hydrocarbon(s)" means hydrocarbon(s) having more than one carbon atom per molecule, oxygenate having at least one carbon atom per molecule, e.g., ethane, ethylene, propane, propylene, benzene, toluene, xylenes, naphthalene, and/or methyl naphthalene; and/or organic compound(s) comprising at least one carbon atom and at least one non-hydrogen atom, e.g., methanol, ethanol, methylamine, and/or ethylamine.
As used herein the term "aromatic hydrocarbon(s)" means molecules containing one or more aromatic rings. Examples of aromatic hydrocarbons are benzene, toluene, xylenes, naphthalene, and methylnaphthalenes.
(The) present invention is a process for converting methane to higher hydrocarbons including aromatic hydrocarbons, the process comprising: providing to the reaction zone a hydrocarbon feedstock containing methane (and) at least one of CO, CO2, H2, H2O, and/or O2.
Hydrogen Management: Since hydrogen is a major component of (the effluent of one of the process steps), after recovery of the aromatic products, the effluent may be subjected to a hydrogen rejection step to reduce the hydrogen content of the effluent before the unreacted methane is recycled to ... maximize feed utilization. Typically the hydrogen rejection step comprises reacting at least part of the hydrogen ... with an oxygen-containing species, such as CO and/or CO2 (and) Fischer-Tropsch may be employed ... .
In addition to methane, the feed to the (initial) step may contain at least one of hydrogen, water, oxygen, carbon monoxide and carbon dioxide ... . These additives can be introduced as separate co-feeds ... (and) sources of carbon dioxide may include flue gases and Liquid Natural Gas plants, (and, various other chemical) plants."
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We'll conclude our excerpts there, so we can summarize and emphasize a few things.
First, note that, as immediately above, our venerable old Coal liquefaction friend "Fischer-Tropsch may be employed" to further process the intermediate gaseous products of these ExxonMobil inventions and synthesize various hydrocarbons.
We can, though, according to ExxonMobil, as herein confirmed by our own US Government experts, also react Methane with Carbon Dioxide, recovered, for instance, as ExxonMobil suggests, from a plant that cleans, compresses and liquefies Natural Gas, and, through that reaction, synthesize a variety of compounds, including the "benzene, toluene" and , "xylene" components of Gasoline blending stock.
And, once again, as in:
Consol 1953 Coal to Hydrogen & Methane with No CO2 | Research & Development; concerning: "United States Patent 2,654,661 - Gasification of Carbonaceous Solid Fuels; 1953; Assignee: Consolidation Coal Company, Pittsburgh; This invention relates to the gasification of carbonaceous solid fuels, and particularly to the production of ... methane and hydrogen in varying relative proportions depending upon the particular temperature and pressure conditions"; and, in:
US Air Force 1965 CO2 to Fuel Conversion | Research & Development; concerning the: "Catalytic Reduction of Carbon Dioxide to Methane; AF 3"(615)-1210 ... research on the catalytic reduction of carbon dioxide to methane and water; work (supervised by the) Air Force Flight Dynamics Laboratory, Research and Technology Division, Wright-Patterson Air Force Base, Ohio;
we can make the Methane we need, for the use in the processes herein of US Patents Number 7795490 and Number 7772447, to be reacted with Carbon Dioxide and thereby be converted into "higher hydrocarbons including aromatic hydrocarbons" from either Coal, or, Carbon Dioxide itself.
Further, we'll acknowledge that ExxonMobil also specifies that, in addition to than Carbon Dioxide, Carbon Monoxide can, as well as or instead of Carbon Dioxide, be included in the Methane reforming reactions.
Should, for whatever reason, Carbon Monoxide be preferable, then, we remind you, as in:
More Pre-WWII CO2 Recycling | Research & Development; concerning: "US Patent 2,128,262 - Carbon Monoxide Manufacture; 1938; Assignee: Semet-Solvay Engineering Corporation, NY; Abstract: An object of this invention is to provide an efficient and economical process for the manufacture of carbon monoxide of high purity by the reduction of carbon dioxide (wherein) carbon dioxide (is passed) through (an) incandescent body of coke to produce carbon monoxide"; that,
we can make all of the Carbon Monoxide we might want by passing Carbon Dioxide through red-hot Coal.
And, all of it goes toward the manufacture of a wide variety of "higher" and "aromatic hydrocarbons", including all those we might need to blend up Gasoline.