Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2001-05-21
2002-09-17
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S243000, C570S245000, C570S254000, C568S893000, C562S520000, C585S324000, C585S642000
Reexamination Certificate
active
06452058
ABSTRACT:
BACKGROUND OF THE INVENTION
In a first aspect, this invention pertains to a process for the oxidative halogenation of methane or halogenated C
1
hydrocarbons. For the purposes of this discussion, the term “oxidative halogenation” shall refer to a process wherein methane or a halogenated C
1
hydrocarbon (the “reactant hydrocarbon”) is contacted with a source of halogen and, optionally, a source of oxygen so as to form a halogenated C
1
hydrocarbon having a greater number of halogen substituents as compared with the reactant hydrocarbon. The oxidative chlorination of methane with hydrogen chloride in the presence of oxygen to form methyl chloride is an example of this process.
Monohalogenated methanes, such as methyl chloride, find utility in the production of silicones and higher halogenated methanes and can also be used as intermediates in the production of numerous commodity chemicals, for example, methanol, dimethyl ether, light olefins, including ethylene and propylene, and higher hydrocarbons, such as gasolines. Other halogenated C
1
hydrocarbons, such as dichloromethane, find utility as solvents, as intermediates for the manufacture of silicones, and in the methylation or etherification of cellulose, alcohols, and phenols, for example.
In a second aspect, this invention pertains to a process of preparing methyl alcohol and/or dimethyl ether by way of the oxidative halogenation of methane to form methyl halide and thereafter the hydrolysis of methyl halide to form methanol and/or dimethyl ether. Both methanol and dimethyl ether can be used as components in gasolines. Methanol, itself, can be used as a motor fuel, as a source of energy, and as a raw material feedstock for a variety of useful syntheses.
In a third aspect, this invention pertains to a process of preparing light olefins, such as ethylene, propylene, and butenes, and/or heavier hydrocarbons, such as C5+ gasolines, by way of the oxidative halogenation of methane to form methyl halide and the subsequent condensation of methyl halide to form light olefins and/or gasolines. Light olefins, such as ethylene, propylene, and butenes, are used as monomers in the production of poly(olefins), such as poly(ethylene), poly(propylene) and poly(butadienes), as well as being used as feedstocks for many valuable chemicals, for example, styrene, vinyl chloride monomer, cumene, and butadiene. The utility of gasolines is well known.
In a fourth aspect, this invention pertains to a process of preparing vinyl halide monomer using methane as a raw material. Vinyl halide monomer finds utility in the manufacture of poly(vinyl halide) polymers, notably poly(vinyl chloride).
In a fifth aspect, this invention pertains to a process of preparing acetic acid using methane as a raw material. Acetic acid finds wide utility in the manufacture of vinyl acetate and cellulose acetate, and in the production of important solvents, such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl acetate.
As ready supplies and access to crude oil have become more uncertain, alternative sources of hydrocarbons and fuel have been sought out and explored. The conversion of natural gas, containing predominantly low molecular weight alkanes, to higher molecular weight hydrocarbons has received increasing consideration, as natural gas is generally available from readily secured and reliable sources. Large deposits of natural gas, chiefly composed of methane, are found in many locations throughout the world. In addition, low molecular weight alkanes are generally present in coal deposits and can be formed during mining operations, in various petroleum processes, and in the gasification or liquefaction of synthetic fuelstocks, such as, coal, tar sands, oil shale, and biomass. Moreover, in the search for petroleum, large amounts of natural gas are often discovered in remote parts of the world, such as remote parts of Western Canada, Australia, China, and the former Soviet Union, where there are no local markets for the use of natural gas as a fuel or as a chemical feedstock.
Much of the readily accessible natural gas is used in local markets as fuel in residential, commercial, and industrial applications. Typically, materials used as fuel are traded at prices below the prices commanded for chemical feedstocks. Use of natural gas as a chemical feedstock is, thus, a high-value application. Accessibility, however, is a major obstacle to the effective and extensive use of remote gas, whether for fuel or feedstock. In fact, vast quantities of natural gas are often flared, particularly in remote areas from which its transport in gaseous form is practically impossible.
Conversion of natural gas to useful chemical feedstocks, preferably liquid feedstocks, offers a promising solution to the problem of transporting low molecular weight hydrocarbons from remote locations; but conversions of this sort present a special challenge to the petrochemical and energy industries. The dominant technology now employed for utilizing remote natural gas involves its conversion to synthesis gas, also commonly referred to as “syngas,” a mixture of hydrogen and carbon monoxide, with the syngas subsequently being converted to liquid products. Synthesis gas can be converted to syncrude, such as, with Fischer-Tropsch technology, and syncrude can then be upgraded to transportation fuels using typical refining methods. Alternatively, synthesis gas can be converted to liquid oxygenates, such as methanol, which in turn can be converted to more conventional transportation fuels via certain zeolitic catalysts.
While syngas processing provides a means for converting natural gas into a more easily transportable liquid that in turn can be converted into useful chemical products, the intermediate step involved in such processing, i.e., the formation of the synthesis gas, is disadvantageously costly. The cost occurs in adding oxygen to the substantially inert methane molecule to form the syngas mixture of hydrogen and carbon monoxide, and occurs again in removing the oxygen when hydrocarbons are the desired end-product. As a further disadvantage, if synthesis gas is to be used to make methanol or hydrocarbon products, the syngas should be made at high pressure and high temperature to achieve acceptable syngas formation rates. Accordingly, a search continues for alternate means of converting methane directly to more valuable chemical feedstocks.
A potential alternate route to activating methane involves its oxidative halogenation in a first step to form methyl halide or other lower halogenated methanes, e.g., dihalomethanes, which can then be converted in a second step into valuable commodity chemicals, such as methanol, dimethyl ether, light olefins, and higher hydrocarbons, including gasoline. When applied to chlorine halogenation, this route has been referred to as the “chlorine-assisted” route, which can be represented by the following two-step process (I) and (II):
CH
4
+HCl+O
2
→chloromethane(s)+H
2
O (I)
chloromethane(s)→chemical product+HCl (II)
For such a reaction scheme to be practical, the HCl generated in the second step should be efficiently recycled to the first step of the process.
Numerous references describe the catalyzed oxidative halogenation of methane to halogenated methanes, as noted for example in the following representative art: U.S. Pat. Nos. 3,172,915, 3,657,367, 4,769,504, and 4,795,843. Catalysts for the oxidative halogenation of hydrocarbons, such as methane, have typically consisted of first row transition metal halides, particularly, copper chloride, with promoters, such as potassium and lanthanum chlorides, supported on silica or alumina. Other common catalysts include iron compounds or cerium oxide, optionally, with one or more alkali or alkaline earth metal chlorides, and/or optionally, with one or more rare earth compounds, supported on an inert carrier, typically alumina, silica, or an aluminosilicate.
Disadvantageously, the oxidative halogenation processes cited hereinabove produce an unacceptable qu
Hickman Daniel A.
Jones Mark E.
Schweizer Albert E.
Dow Global Technologies Inc.
Siegel Alan
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