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  Carbon beads with multimodal pore size distributionThe Patent Description & Claims data below is from USPTO Patent Application 20070258879. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority under 35 U.S.C. 119 to U.S. Provisional Patent Application No. 60/749,591 filed on Dec. 13, 2005, the entire content of which is hereby incorporated by reference. BACKGROUND [0002] Conventional cigarettes have filter elements that can incorporate materials such as carbon. Certain commercially available filter cigarettes have particles or granules of carbon (e.g., an activated carbon material or an activated charcoal material) incorporated with the cellulose acetate tow or in cavities of a cellulose acetate material. [0003] Activated carbon has strong physical adsorption forces, and high volumes of adsorbing porosity. Traditionally, activated carbon is formed by activation and carbonization of coconut husk, coal, wood, pitch, cellulose fibers, or polymer fibers, for example. Carbonization can be carried out at high temperatures, i.e., about 200.degree. C. to about 800.degree. C., in an inert atmosphere, followed by activation in an oxidization environment. [0004] As a result of using single composition precursors, single modal pore distributions are attained in activated carbon because of the pore sizes of activated carbon being dependent upon the single composition precursors, and the carbonization and activation processes. Thus, the activated carbon has been provided with a single modal pore distribution, which in turn has only provided predictable, single function adsorption properties. SUMMARY [0005] Accordingly, a method of forming a multi-modal pore distribution activated carbon is provided herein. The multi-modal pore distribution activated carbon is formed by combining pore size forming properties from multiple materials. For example, multiple carbonizable precursors can be combined in a single carbonizable precursor composite, and then the composite can be carbonized and activated to form multi-modal pore distribution activated carbon. Alternatively, a carbonizable precursor can be combined with a carbon structure, such as a nanotube wherein upon activation and carbonization, a multi-modal pore distribution activated carbon can be formed. Thus, activated carbon can be formed to have a multi-modal pore distribution based upon the pore forming properties of the starting materials. [0006] Additionally, a multi-modal pore distribution activated carbon is also provided herein. The multi-modal pore distribution activated carbon includes a multi-modal distribution of pore sizes with larger and smaller pores. By providing larger pores in a multi-modal pore distribution activated carbon, transporting constituents into the body of an adsorbing carbon particle can be expedited. On the other hand, by providing smaller pores, constituents can be trapped and held by the smaller pores within the body of the adsorbing carbon particle. In an exemplary embodiment, larger pores are provided to aid in the kinetics of adsorption of constituents by speeding up the constituents' diffusion/transport into an adsorbing carbon particle, while smaller pores are provided that are more energetic and thus adsorb and hold the constituents within the activated carbon particle. [0007] Also provided is a multi-modal pore distribution activated carbon comprising activated carbon with a first set of pores with a single mode pore distribution formed by a first carbonizable precursor and a second set of pores formed by a second carbonizable precursor, carbonized structures, zeolites, or combinations thereof, wherein the first carbonizable precursor and the second carbonizable precursor, carbonized structures, zeolites, or combinations thereof, are mixed and heat treated to form the multi-modal pore distribution activated carbon, and wherein the first set of pores has smaller pore size than the second set of pores. [0008] Also provided is a method of producing a multi-modal pore distribution activated carbon comprising the steps of (i) preparing a solution comprising a polymer precursor; (ii) mixing an additional precursor material with the polymer precursor in the solution; (iii) cross-linking the polymer precursor with the additional precursor material mixed therein; (iv) carbonizing the mixture of the polymer precursor and the additional precursor material; and (v) activating the carbonized mixture to form a multi-modal pore distribution activated carbon. [0009] Also provided is a method of making different shape adsorbents by immobilizing and stabilizing precursors in polysaccharide media. By employing this method, precursors usually treated by less desirable process conditions, i.e., slow stabilization below the melting point of the carbon precursor and often requiring the use of solvents, can be immobilized and converted to adsorbent media. BRIEF DESCRIPTION OF THE DRAWING FIGURES [0010] FIG. 1. A multi-modal pore distribution activated carbon particle is illustrated, wherein the multi-modal pore distribution activated carbon particle is formed from a pectin-nanotube mixture prepared according to Example 1. [0011] FIG. 2. A cross-section of a multi-modal pore distribution activated carbon particle from a pectin-nanotube mixture prepared as described in Example 1. [0012] FIG. 3. A cross-section of an exemplary pectin precursor activated carbon. [0013] FIG. 4. A graph of a pore size distribution for an exemplary pectin precursor activated carbon. DETAILED DESCRIPTION [0014] Methods are disclosed for forming a multi-modal pore distribution activated carbon (multi-modal pore distribution activated carbon). The multi-modal pore distribution allows for tailoring of the adsorption properties of the activated carbon. This can be accomplished by using a single composite, which includes more than one pore size determinant material. [0015] By using a combination of more than one pore size determinant material, such as carbonizable precursors, carbon structures, zeolites, in a composite, a multi-modal pore distribution activated carbon can be formed with a predetermined pore size distribution. [0016] For example, activated carbon can be formed from a mixture or composite including a first pore forming composition and a second pore forming material. By providing the mixture or composite, activated carbon made from the mixture or composite can have a primarily bimodal pore distribution with the first mode from the first pore forming material and the second mode from the second pore forming material. In other words, activated carbon with two highly uniform bimodal pore sizes (i.e., a highly uniform set of large pores formed from the first composition and a highly uniform set of small pores formed from the second composition) can be formed. [0017] By providing a set of larger pores in a multi-modal pore distribution activated carbon, the kinetics or speed of adsorption by the activated carbon can be increased. The larger pores allow for a larger flux of constituents, as well as larger constituents, as an adsorbate molecule smaller than a pore can pass through the pore entrance and into an inner part of the pore. [0018] The term "constituent kinetic behavior" as used herein is intended to denote flow through surfaces of the activated carbon (i.e., passing gaseous constituents through pores and/or channels in the activated carbon with adsorption or absorption). Thus, depending upon the constituent kinetic behavior of the activated carbon, gaseous constituents can flow through pores of the activated carbon in predetermined amounts as tailored by the pore sizes within the activated carbon. For example, larger gaseous constituents can be trapped in smaller pores and passed through larger pores, thus the constituent kinetic behavior of the activated carbon can be predetermined by the number and sizes of the pores and their pore entrances in the activated carbon. Thus, by providing more numerous and larger sized pores, increased levels of gaseous constituents, both larger and smaller ones, can kinetically flow through the activated carbon. [0019] Larger sized pores, such as macropores, can be used to provide a path for gaseous constituents or molecules to reach interior regions or pores of activated carbon, which as mentioned above, can lead to improved constituent kinetic behavior. Larger pores mainly act to admit adsorbate molecules into an inner part of the activated carbon. The geometry, size, and amount of macropores can significantly affect sorption, especially in filtration processes in which adsorbate molecules move rapidly through a sorbent. Continue reading... Full patent description for Carbon beads with multimodal pore size distribution Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Carbon beads with multimodal pore size distribution patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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