The Mobil Oil Coal-to-Hydrocarbon conversion process disclosed herein can "result in from 30% to 40% overall reduction in processing costs", relative to other, prior art indirect Coal conversion processes, with the end result being a liquid hydrocarbon fuel.
It achieves those savings in a way which, though not directly stated or specified, also likely reduces the amount of Carbon Dioxide co-generated by the system, both in the Coal gasifier and in the catalytic reactor where the product synthesis gas is chemically condensed into liquid hydrocarbons.
The strategy employed is to generate Coal syngas in a high-efficiency Coal gasifier without the addition of Steam to the mix of gases with which the Coal is gasified, which practice however results in a synthesis gas blend of Hydrogen and Carbon Monoxide with a Hydrogen content too low for subsequent catalysis into either alcohols, such as Methanol, or into Gasoline-range hydrocarbons, but which also reduces the amount of Carbon Dioxide generated in the gasifier.
Further, Hydrogen-generating processes incorporated into prior-art or alternative indirect Coal conversion systems, specifically the Water Gas Shift reaction, wherein Carbon Monoxide reacts with Steam to form Hydrogen and Carbon Dioxide, though not entirely eliminated, are reduced in scope and made integral with the catalytic synthesis of hydrocarbons in the reactor, a feature which reduces capital cost, extends catalyst life, and helps to further reduce Carbon Dioxide emission.
But, CO2 emission in and of itself is not a primary concern of Mobil Oil herein. CO2 emission is important only insofar as it represents a loss of Carbon from the system. Reducing the co-production of CO2 leads to a direct increase in the percentage of the original Carbon in the Coal that is productively entrained in the product hydrocarbons.
All of that is accomplished by focusing on the production, from Coal, of one hydrocarbon, Dimethyl Ether, DME, as opposed to Alcohol, Gasoline or what are generically known as "distillates"; and, which DME has some rather unique properties and potentials. More about it can be learned via:
Dimethyl ether - Wikipedia, the free encyclopedia; "DME is a promising fuel in diesel engines ... owing to its high cetane number, which is 55, compared to diesel's, which is 40–53. Only moderate modification are needed to convert a diesel engine to burn DME. The simplicity of this short carbon chain compound leads during combustion to very low emissions of particulate matter, NOx, and CO. For these reasons as well as being sulfur-free, DME meets even the most stringent emission regulations in Europe, U.S., and Japan. Mobil is using DME in their methanol to gasoline process".
And, as we reported more than three years ago, via:
West Virginia Coal Association | Clean Energy from Coal-Derived DME | Research & Development; concerning "'Clean Energy from Dimethyl Ether'; SRI Consulting Publishes Techno-Economic DME from Coal Report; Dimethyl ether (DME) is a clean energy fuel that can be manufactured from various primary energy resources including coal. DME is a colorless, nontoxic and environmentally benign compound ... . When DME is combusted, it generates absolutely no sulfur oxides and 90% less nitrogen oxide emissions than today’s fossil fuels. Today, SRI Consulting (SRIC) published its techno-economic report DME from Coal providing detailed analysis of two leading DME from coal technologies and their process economics. (SRI) calculated that DME as an energy source is economically viable when the crude oil price is at US$55 a barrel";not only is DME a cleaner-burning fuel than Diesel, we can make it from Coal, and use it profitably, when the price of crude oil is at "US$55 a barrel".
And, as can be learned from our US Department of Energy's Energy Information Administration, via:
Spot Prices for Crude Oil and Petroleum Products; as of April 1, 2013, the price of West Texas Intermediate crude oil, as delivered in Oklahoma, was $97, and change, per barrel. So, we've got some wiggle room.
As noted by the Wikipedia, in our citation above, "Mobil is using DME in their methanol to gasoline process"; with that being a technology which we've referred many times to and made many reports of, as, for one example, in:West Virginia Coal Association | ExxonMobil Coal to Methanol to Gasoline | Research & Development; concerning both: "United States Patent 4,348,486 - Production of Methanol via Catalytic Coal Gasification; 1982; Exxon Research and Engineering Company; Claims: A process for the production of methanol from a carbonaceous feed material (by)gasifying said carbonaceous feed material with steam ... and added hydrogen and carbon monoxide (and) wherein said carbonaceous feed material comprises coal.
The process of the invention provides a highly efficient method of integrating a thermoneutral gasification process with a methanol synthesis process in order to produce methanol and thus has many advantages over thermoneutral gasification processes in the past which could be used only to produce gaseous products. This invention provides a process for producing methanol by the substantially thermoneutral reaction of steam with coal"; and: "United States Patent 4,035,430 - Conversion of Methanol to Gasoline; 1977; Mobil Oil Corporation; Claims: (A) method for converting methanol to gasoline boiling products in a plurality of sequentially arranged catalyst beds ... . This invention relates to the method and system for converting methanol to gasoline boiling components".
Others have noted some of the advantages of using DME, rather than Methanol, as the intermediate product in the conversion of Coal, through synthesis gas, into Gasoline, as seen, for example, in:
West Virginia Coal Association | The University of Akron Improves Coal to Gasoline Process | Research & Development; concerning: "'A Novel Synthesis Route for Liquid Fuels from Coal-derived Syngas'; Makarand Gogate, Conrad J. Kulik, and Sunggyu Lee; Department of Chemical Engineering; The University of Akron, Akron, Ohio; Fuel Science Program; Electric Power Research Institute; Palo Alto, California; Abstract: Coal-derived syngas can be converted to methanol using Liquid Phase Methanol Synthesis Process. Methanol can be further converted to gasoline using the Mobil Methanol-To-Gasoline (MTG) process. The combination of commercial syngas-to-methanol technology with the MTG Process thus provides a ready synthetic route for liquid hydrocarbon fuels. We have developed a novel process for one-step synthesis of Dimethyl Ether (DME) from syngas. This DME Synthesis improves the reactor productivity and syngas conversion, by as much as 100% over LPMeOH (Liquid Phase Methanol) Process. One-step DME synthesis is thus an ideal front-end for further conversion to gasoline.This substitution is justified not only because DME yields an identical product distribution as methanol, DME is also a true intermediate in the Mobil MTG process. The novel integration scheme has been termed as the Dimethyl Ether-to-Gasoline (DTG) process. The advantages of the UAEPRI (University of Akron and Electric Power Research Institute) DTG Process over the conventional Methanol-to-Gasoline Process are in: (a) enhanced syngas conversion, (b) superior hydrocarbon yield".With the above research work being, by the same team of scientists, further confirmed in:
West Virginia Coal Association | Akron, OH, Converts More Coal into Gasoline | Research & Development; concerning: "United States Patent 5,459,166 - Catalytic Process for Production of Gasoline from Synthesis Gas; 1995; Inventors: Sunggyu Lee, Makarand Gogate, et. al., OH and CA; Assignee: Electric Power Research Institute, Palo Alto, CA; Abstract: A process is provided whereby syngas is converted to gasoline via a liquid-phase process producing dimethyl ether as an intermediate".
A little more about the trade-offs between Coal-to-Methanol-to-Gasoline and Coal-to-Dimethyl Ether-to-Gasoline is explained by the above, former we believe, Akron University professor Sunggyu Lee, in:
West Virginia Coal Association | U of Akron: Methanol-to-Gasoline vs. DME-to-Gasoline | Research & Development; concerning: "Methanol-to-gasoline vs. DME-to-gasoline. II: Process comparison and analysis; Sunggyu Lee, et. al., University of Akron; Fuel Science and Technology International, 1995".
In sum, it can be more efficient and economical to produce Dimethyl Ether, via Syngas, from Coal; and, then, if desired, convert that substitute Diesel fuel into Gasoline in a separate process not really that much unlike some rather standard petroleum refinery hydrotreating processes. The difference between converting Methanol to Gasoline and Dimethyl Ether to Gasoline seeming to be, that, in the one Oxygen is removed and, in the other, Hydrogen is added.
In any case, Coal can be more economically converted, via synthesis gas, into Dimethyl Ether, as established by Mobil Oil in excerpts from the initial link in this dispatch to:
"United States Patent 4,423,155 - Dimethyl Ether Synthesis Catalyst
Patent US4423155 - Dimethyl ether synthesis catalyst - Google Patents
Dimethyl ether synthesis catalyst - Mobil Oil Corporation
Date: December 27, 1983
Inventors: Weldon Bell and Clarence Chang, NJ
Assignee: Mobil Oil Corporation, NY
Abstract: A new catalyst and process for synthesis of dimethyl ether from low H2 / CO ratio syngas are disclosed. The catalyst is a combination of Copper, Zinc and Aluminum, co-precipitated in predetermined relative amounts, which is found to be oxidatively regenerable and utilizable with the syngas product of modern coal gasifiers without the need for external water-gas-shift.
(Again, eliminating the "external water-gas-shift" would reduce capital costs, operational complexity and Carbon Dioxide co-production.)
Claims: A catalyst composition comprising: (A) coprecipitated metal components consisting essentially of Copper, Zinc and Aluminum wherein the atomic ratio of Al/(Cu+Zn) is greater than or equal to 0.2:1 and the ratio of Cu/Zn is from 0.2:1 to 5.0:1 and: (B) an acidic dehydrating component.
The catalyst composition ... wherein said acidic dehydrating component is selected from the group consisting of gamma alumina; silica-alumina; clays; natural or synthetically prepared crystalline aluminosilicates; crystalline zeolites (as specified); phosphates; and titanium oxide in combination with silicon oxide, rare earths and clays.
(A lot of fairly common mineral substances will do the trick, it seems. There's nothing very exotic in any of that. The "synthetically prepared crystalline aluminosilicates" might even be something we could extract or make out of Coal Ash.)
The catalyst composition ... wherein said acid dehydrating component comprises from 5 wt % to 95 wt % of said composition (and) wherein said component comprises gamma alumina.
(The "gamma alumina" sounds complicated, or rare. It ain't. We can make it by heat-treating the mineral "boehmite", which, as can be learned via:
Boehmite - Wikipedia, the free encyclopedia; "is an aluminum oxide hydroxide" and a common component of the "aluminum ore bauxite". It is, further, a degraded or weathered version of pretty-darned common Aluminum-containing Spinel minerals. See:
Spinel - Wikipedia, the free encyclopedia.
And, if we can't find them, they were first synthesized in the lab more than a century ago, although some later techniques developed subsequent to the year 2000 are much better. The stuff, in other words, is, almost literally, as common and as easy to get as dirt.)
The composition ... wherein said atomic ratio of Aluminum (to Copper and Zinc is as specified).
The composition ... which is oxidatively regenerated by contacting with an oxygen-containing gas at temperatures of between about 250 and 540 C.
(The above claim is indicative of the economies of this catalyst and technology. Other syngas and carbon conversion catalysts, when they become fouled, typically with Carbon deposits, have to be reacted with superheated steam or Hydrogen, or be calcined, to restore reactivity. A little hot air, an "oxygen-containing gas", seems to do the trick in this case, which is an enormous savings, especially in terms of operational complexity.)
Background and Field: This invention is concerned with a process for converting synthesis gas (H2 and CO) to dimethyl ether.
There are at present two major routes for effecting the conversion of coal via synthesis gas to liquid fuels comprising the well publicized Fischer-Tropsch process and a more recently developed methanol to gasoline process such as provided in U.S. Pat. No. 3,928,483, issued Dec. 23, 1975.
(Production of gasoline hydrocarbons - Mobil Oil Corporation; "United States Patent 3,928,483 - Production of Gasoline Hydrocarbons; 1975; Inventor: Clarence Chang, et. al., NJ; Assignee: Mobil Oil Corporation, NY; Abstract: This specification discloses a process for the production of aromatics-rich gasoline boiling-range hydrocarbons from the lower alcohols methanol, ethanol and propanol, or their ethers. The process is carried out in two or more stages. In the first stage, an alcohol or an ether is contacted with a condensation catalyst to produce a reaction product containing aliphatic dehydration products thereof and water. In a subsequent stage, at least a portion of the product of the first reaction stage is contacted with, as a catalyst, a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least 12 and a constraint index of 1 to 12 to convert it in high yield to gasoline boiling-range hydrocarbons containing a high proportion of aromatics. In a preferred aspect a lower alcohol, suitably methanol, is dehydrated to an ether or a lower olefin or mixtures thereof, in the first stage, and this first stage product is then converted, over the referred to catalyst, to gasoline boiling-range hydrocarbons.")
The Fischer-Tropsch process produces a wide range of C1 to C50 products comprising gases, liquid hydrocarbons, oxygenates and water.
Common to each of the above processes is the overriding influence of the capital cost of synthesis gas (H2 +CO) production. This varies with gasifier design, which is in turn influenced by coal properties.
A principal advantage to be gained in producing dimethyl ether (DME) directly from syngas is that it has been found that this compound can be readily converted to gasoline range hydrocarbons using a special class of crystalline porotectosilicates, represented by ZSM-5 crystalline zeolite such as discussed in U.S. Pat. No. 3,928,483, wherein the formed methanol is dehydrated and the ether product thereof is converted over said ZSM-5 crystalline zeolite.
The present invention is directed to the conversion of synthesis gas or "syngas" to intermediate products which are readily convertible to gasoline boiling range hydrocarbons. The direct conversion of syngas to dimethyl ether is technically feasible. Furthermore, the conversion of dimethyl ether to gasoline boiling range products comprising olefins and aromatics is likewise achievable, as identified above, by employing the particular class of crystalline zeolite discussed therein and below.
In a more particular aspect, the present invention is concerned with improvements in the direct conversion of syngas to dimethyl ether whereby an economically attractive operation is attained by virtue of reducing the catalyst aging characteristics, in cooperation with utilization of an oxidative regeneration technique which has not heretofore been successful, and thus maintaining the catalyst at a high level of activity sufficient to sustain below or near equilibrium conversion level of the syngas feed.
The (DME) dimethyl ether synthesis techniques of this invention are of particular and novel interest upon noting that H2/CO ratio gases of either less than 1 or greater than 1 can be utilized. Thus, the ratio of H2/CO may be within the range of 0.4 to 3. However, it is particularly preferred to employ gas ratios equal to or less than 1, since such gas ratios are much more economically produced by modern high efficiency (Coal) gasifiers and such a source of syngas can result in from 30% to 40% overall reduction in processing costs.
In this low ratio (H2 /CO) syngas operating environment, it has been determined that the hydrogen (H2) deficiency of the low ratio syngas, in the range of 0.4 to 0.7, can be remedied or compensated for by injecting steam (H2O) into the catalyst mass separately or in admixture with the low ratio syngas charged.
This added steam (H2O) is subject to water-gas-shift reaction by the particular catalyst composition employed, resulting in a very effective and increased H2/CO ratio gas in the catalyst reaction zone. This particular operating mode thus eliminates the need for external water-gas-shift requirements to modify the low ratio syngas, thereby further contributing to the overall economic improvement of the processing combination.
The present investigation into obtaining direct conversion of syngas to dimethyl ether (DME), and the concepts developed therefrom, dramatically demonstrate that certain selected catalyst compositions, consisting of coprecipitated mixed oxides of Cu, Zn and Al and mixed with a suitable acid component such as gamma-alumina, provide high catalyst activity and selectivity for effecting dimethyl ether synthesis.
More important, however, was the discovery that these selected coprecipitated catalyst compositions could be periodically oxidatively regenerated to maintain desired high catalyst activity. That is, the particular catalyst compositions of the invention were maintained at high steady state activity for an extended on-stream syngas conversion operating period by relying upon particular oxidative regeneration and pretreatment techniques of relatively short duration as more particularly discussed herein. For example, the catalyst in the syngas reaction zone may be regenerated therein or it may be passed through a separate catalyst regeneration operation and then returned to the reaction zone to maintain desired catalyst activity and selectivity. The regeneration of the catalyst may be accomplished in a continuous, semi-continuous or an interrupted (e.g. periodic) operating mode, depending upon whether a fixed bed or a moving catalyst system is employed."
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It is, in sum, a much more economical process for converting Coal into a serviceable hydrocarbon fuel, DME, which can, oddly, be used both as a substitute for Diesel and as a substitute for liquefied petroleum gas, LPG, which, we should note, is not quite the same as liquefied natural gas, LNG. As an example of LPG, think of Propane and Butane. LNG can be thought of as being primarily Methane.
We remind you, too, however, that, speaking of Methane, just as, as seen most recently in:
West Virginia Coal Association | German Solar Energy is Converting CO2 into Methane | Research & Development; concerning: "US Patent Application 0130041051 - Method for Producing a Methane-rich Product Gas and Reactor System Usable for that Purpose; 2013; Assignee: Solar Fuel, Gmbh, (Germany); Abstract: The invention relates to a method for producing a methane-rich product gas, in which a starting gas containing hydrogen and carbon dioxide is catalytically methanated";
we can synthesize Methane from Carbon Dioxide, as we've also previously reported, in:
West Virginia Coal Association | Conoco Converts CO2 to Methanol and Dimethyl Ether | Research & Development; concerning: "United States Patent 6,664,207 - Catalyst for Converting Carbon Dioxide to Oxygenates; 2003; ConocoPhillips Company; Abstract: A catalyst and process for converting carbon dioxide into ... methanol and dimethyl ether"; and:
West Virginia Coal Association | California Recycles More and More Carbon Dioxide | Research & Development; concerning, only in part: "United States Patent 7,378,561 - Producing ... Synthetic Hydrocarbons from Carbon Dioxide and Water; 2008; University of Southern California; Abstract: A method for producing methanol and dimethyl ether (from) water (i.e., the moisture in the air) and carbon dioxide";
we can make the product of our subject, "United States Patent 4,423,155 - Dimethyl Ether Synthesis Catalyst", that is, the versatile hydrocarbon fuel, DME, out of CO2, as well as out of our abundant Coal.
So, any Carbon Dioxide that might be co-produced during the Coal gasification and subsequent syngas catalysis processes of "United States Patent 4,423,155" could simply be collected and forwarded into a subsidiary facility operating, say, the process of "United States Patent 7,378,561 - Producing ... Synthetic Hydrocarbons from Carbon Dioxide and Water", and be converted into more of the basic product, the cleaner, more environmentally-friendly substitute Diesel fuel, a substitute Diesel fuel which can, if wanted, be further converted into Gasoline, Dimethyl Ether.