Polymer templated nanowire catalysts

Abstract

Nanowires useful as heterogeneous catalysts are provided. The nanowire catalysts are prepared by polymer templated methods and are useful in a variety of catalytic reactions, for example, the oxidative coupling of methane to ethane and / or ethylene. Related methods for use and manufacture of the same are also disclosed.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61 / 564,834, filed on Nov. 29, 2011; Provisional Patent Application No. 61 / 564,836, filed on Nov. 29, 2011; and U.S. Provisional Patent Application No. 61 / 651,399, filed on May 24, 2012; each of which are incorporated herein by reference in their entireties.BACKGROUND[0002]1. Technical Field[0003]This invention is generally related to novel nanowire catalysts and, more specifically, to nanowires prepared via polymer templated methods. The nanowires are useful as heterogeneous catalysts in a variety of catalytic reactions, such as the oxidative coupling of methane to ethylene.[0004]2. Description of the Related Art[0005]Catalysis is the process in which the rate of a chemical reaction is either increased or decreased by means of a catalyst. Positive catalysts increase the speed of a chemical reaction, while negative catalysts slow it down...

AI Technical Summary

Benefits of technology

The present patent is about methods for making nanowires that can be used as catalysts in chemical reactions. The methods involve using polymer templates and metal ions to create nanowires with metal oxides, metal oxy-hydroxides, metal oxycarbonates, or metal carbonates. The nanowires can be used in a variety of chemical reactions such as oxidative coupling of methane. The patent also describes a method for creating a core / shell structure with different metal oxides or oxy-hydroxides on the nanowire surface. Overall, the patent provides methods for making nanowires with improved activity and selectivity for chemical reactions.

Problems solved by technology

Thus, at a given temperature, a positive catalyst tends to increase the yield of desired product while decreasing the yield of undesired side products.

Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated or destroyed by secondary processes, resulting in loss of catalytic activity.

This transport and adsorption of reactants is often the rate limiting step in a heterogeneous catalysis reaction.

In addition, homogeneous catalysts can be difficult to separate from the reaction mixture.

While there are multistep paths to convert methane to certain specific chemicals using first; high temperature steam reforming to syngas (a mixture of H2 and CO), followed by stochiometry adjustment and conversion to either methanol or, via the Fischer-Tropsch (F-T) synthesis, to liquid hydrocarbon fuels such as diesel or gasoline, this does not allow for the formation of certain high value chemical intermediates.

This multi-step indirect method also requires a large capital investment in facilities and is expensive to operate, in part due to the energy intensive endothermic reforming step.

It is also inefficient in that a substantial part of the carbon fed into the process ends up as the GHG CO2, both directly from the reaction and indirectly by burning fossil fuels to heat the reaction.

Since the OCM reaction was first reported over thirty years ago, it has been the target of intense scientific and commercial interest, but the fundamental limitations of the conventional approach to C—H bond activation appear to limit the yield of this attractive reaction.

One type of catalyst expected to meet the above need are nanowire catalysts comprising various metal elements; however, methods for preparation of nanowire catalysts which fulfill these needs are not readily available in the art.

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