Efficient, self sufficient production of methanol from a methane source via oxidative bi-reforming

Abstract

A method for producing methanol from a methane source such as methane from natural (shale) gas by first reacting one equivalent of methane with oxygen from the air to result in complete combustion to produce carbon dioxide and water in a molar ratio of 1:2; then conducting a bi-reforming process with a mixture of methane: carbon dioxide:water having a ratio of 3:1:2 to produce metgas, a mixture of hydrogen and carbon monoxide having a molar ratio of 2:1 to 2.1:1; and finally converting metgas exclusively to methanol. The thus produced methanol can be dehydrated to form dimethyl ether, with water produced being recycled back to the bi-reforming process, if necessary.

Description

BACKGROUND[0001]Although fossil fuels still have a wide application and high demand, they have limitations due to their finite reserves. Also, the combustion of fossil fuels produces carbon dioxide, which contributes to global warming.[0002]With the development of various large natural (shale) gas sources in many parts of the world and with the existence of other methane sources such as coal bed methane, methane hydrates, etc., the availability of extensive methane reserves is assured at least for this century. The conversion of natural (shale) gas into liquids, preferentially to methanol used for transportation fuels and source material for varied essential chemical products, is of great practical significance (Beyond Oil and Gas: The Methanol Economy, G. A. Olah, A. Goeppert and G. K. S. Prakash, 2nd Edition, Wiley-VCH, Weinheim, 2009). Currently, widely practiced steam reforming processes of methane generate syngas, CO:H2 with a ratio of 1:3. Additionally, dry reforming with carb...

AI Technical Summary

Benefits of technology

[0033]Presently, the commercial production of methanol uses syngas-based processes including ATR, which utilizes internal partial oxidation for providing the reaction heat but requires adjusting the syngas composition to CO-2H2 and producing unwanted by-products including CO2, thus necessitating carefully controlled conditions as well as additional costly steps. Consequently, modern methanol plants are economic and feasible only with >1 million tonnes / year capacity and represent a multi-billion dollar investment. As the simple and efficient process of the invention achieves extremely significant cost savings, it is possible to operate smaller plants (of ˜50,000 t / y capacity), which can be readily scaled up to >1 Mt / y mega plants. As the process of the invention does not need much external energy input or purification of CO2 or water, it is internally self-sufficient and can be used with great flexibility to location. Moreover, the process of the invention, which generates metgas to produce methanol from natural (shale) gas, can also be adapted to produce methanol from the exhausts of natural (shale) gas or even coal or oil burning power plants containing carbon dioxide and steam.

[0034]The individual reactions of the process of the invention, namely, the complete combustion of methane or natural (shale) gas with oxygen of the air, the bi-reforming reaction of methane using CO2 and H2O, and the synthesis of methanol from metgas (CO-2H2), are separately known and well proven. Applying the heat generated from the partial oxidation of methane for the reforming process is also known. For example, WO 2007 / 014487 discloses combining the partial oxidation of methane (POM) with the wet reforming and / or the dry reforming reaction in a single step. Although such “thermoneutral tri-reforming” reaction allows the heat produced in the exothermic partial oxidation of methane to be used in the endothermic steam and dry reforming reactions, the partial oxidation produces a mixture of products, thus necessitating further costly separation process and adjustments to obtain a syngas containing CO and H2 in a molar ratio of 1:2 for the production of methanol. The process of the present invention provides a simple, economic and environmentally benign solution for converting methane or natural (shale) gas exclusively to methanol by conducting the complete combustion of part of methane first and using the products of the complete combustion, i.e., CO2 and H2O, in a molar ratio of 1:2 for the subsequent bi-reforming reaction with methane or natural (shale) gas to produce metgas, which is subsequently used to produce exclusively methanol without requiring separation of products or the addition of energy from external sources.

[0035]The process of the invention in its entirety provides a new economic, environmentally carbon neutral and feasible method for the selective and exclusive production of methanol without waste and byproducts, which also has the flexibility of being adjusted to any local condition and available feeds. The process of the invention thus allows the efficient and environmentally friendly and economic processing of methane or natural (shale) gas to methanol and / or dimethyl ether, as well as their derived products.

[0036]The following examples illustrate the preferred embodiments of the invention without limiting them.

Problems solved by technology

Although fossil fuels still have a wide application and high demand, they have limitations due to their finite reserves.

These processes involve multiple steps to adjust the needed syngas ratio, however, and also produce significant amounts of carbon dioxide or other oxidation byproducts, which need to be separated or disposed.

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