Activated carbon monolith catalyst, methods for making same, and uses thereof

Abstract

An activated carbon monolith catalyst comprising a finished self-supporting activated carbon monolith having at least one passage therethrough, and comprising a supporting matrix and substantially discontinuous activated carbon particles dispersed throughout the supporting matrix and at least one catalyst precursor on the finished self-supporting activated carbon monolith. A method for making, and a method for use, of such an activated carbon monolith catalyst in catalytic chemical reactions are also disclosed.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to catalytic structures, methods for making same, and uses thereof. In particular, this invention relates to activated carbon monolith catalysts and methods for making and using them. BACKGROUND OF THE INVENTION [0002] Carbon catalysts play an important role in various chemical processes from industrial to pharmaceutical settings. Carbon catalysts enable chemical reactions to occur much faster, or at lower temperatures, because of changes that they induce in the reactants. Carbon catalysts may lower the energy of the transition state of chemical reactions, thus lowering the activation energy. Therefore, molecules that would not have had the energy to react, or that have such low energies that it is likely that they would take a long time to do so, are able to react in the presence of a carbon catalyst by reducing the energy required for the reaction to occur. Not only do carbon catalysts increase the rate of react...

AI Technical Summary

Benefits of technology

[0015] The activated carbon monolith catalyst of this invention is not limited to use of precursor materials that must be carbonized to form a carbon catalyst support. It can include any activated carbon particles from any source. Thus, the activated carbon monolith catalyst of this invention can be made with activated carbon particles chosen for their superior activity and selectivity for a given application. The activated carbon monolith catalyst can then be expected to have a predictable activity and selectivity based on the knowledge available regarding the particular activated carbon particles used. In addition, the activated carbon particles in the activated carbon monolith catalyst of this invention are dispersed throughout the structure of the catalyst, giving depth to the catalyst activity and selectivity. The activated carbon particles are bound by a supporting matrix, which desirably is an inert binder and is not susceptible to attack by reaction media. Furthermore, the activated carbon monolith catalyst of this invention exhibits the desirable features of a ceramic monolith, while also presenting the advantage of a choice of a wide variety of particulate carbon substrates. Such desirable features include ease of separation of the catalyst from a product in a chemical reaction, and predictable fluid flow, among others. Because the activated carbon particles are fixed in a monolithic form, regions of the monolith, in particular embodiments, can include different catalysts as desired. Such regions would not migrate in monolithic form as they would with loose activated carbon particles.

Problems solved by technology

Carbon catalysts may lower the energy of the transition state of chemical reactions, thus lowering the activation energy.

While a particular carbon substrate might have the best features for activity and selectivity, it may not be the best choice considering the chemical process parameters.

For example, carbon granules suffer from attrition making exact pressure drop determinations difficult, and they scale up poorly in chemical processes.

Attrition is a particularly aggravating issue, because it alters the physical parameters of the chemical process as it proceeds, and causes financial loss, particularly when the catalyst is a precious metal.

For this reason, carbons of choice are typically nutshell carbons, which are durable, but which have very small pores that can harshly limit activity and selectivity.

Thus, perhaps one must exclude carbons with better catalytic properties, but which are too friable.

Although monoliths have advantages over fixed bed supports, there are still problems associated with traditional ceramic monoliths.

Exposure of the catalytic metal in the catalytic monolith to the reactants is necessary to achieve good reaction rates, but efforts to enhance exposure of the catalytic metal often have been at odds with efforts to enhance adhesion of the metal to the monolith substrate.

Thus, catalytic ceramic monoliths have fallen short of providing optimal catalytic selectivity and activity.

As seen below, ceramic carbon catalyst monoliths developed to date, on one hand may provide good selectivity and activity, but on the other hand may not be suitable for process parameters such as durability and inertness.

Conversely, ceramic carbon catalyst monoliths suitable for such process parameters may have diminished selectivity and activity.

In most cases, the binders are susceptible to attack by the reaction media in application.

Some cause side reactions, or poison the catalyst.

In either case, the parameters of flow are not predictable by simple, understandable models.

Although the carbons selected have generally been in use as unbound catalyst supports, and unbound activity and selectivity information on the carbon can sometimes be used, still the binder is not inert, and therefore binder influence is always an issue.

Furthermore, the carbons normally used in preparation of catalyst supports are prepared from naturally occurring materials such as wood, peat, nutshell, and coal, and not from refined or organic chemicals.

While carbonization may be a way of producing a carbon coating or structure, it extends marginally the catalyst art, and does not produce a catalyst utilizing the known carbon methods of choice in the art.

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