Carbon nanotube supported catalyst

Carbon nanotube supported catalyst is a novel supported catalyst, using carbon nanotubes as the support instead of the conventional alumina or silicon support. For carbon nanotubes (CNTs), the exceptional physical properties, such as large specific surface areas, excellent electron conductivity incorporated with the good chemical inertness and relatively high oxidation stability, makes it a promising support material for heterogeneous catalysis. Carbon nanotube supported catalyst is a novel supported catalyst, using carbon nanotubes as the support instead of the conventional alumina or silicon support. For carbon nanotubes (CNTs), the exceptional physical properties, such as large specific surface areas, excellent electron conductivity incorporated with the good chemical inertness and relatively high oxidation stability, makes it a promising support material for heterogeneous catalysis. The catalyst is a substance, usually used in small amounts relative to the reactants, that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. One or more kinds of catalysts can be loaded on another material with a high surface area, which serves as the support, to form a supported catalyst as a whole system. In a supported catalyst system, the significance of using the support are to increase the dispersion of the active phases, to have a better control of the porous structure, to improve mechanical strength, to prevent sintering and to assist catalysis. There is a wide spectrum of supports ranging from conventional and most commonly alumina to novel various kinds of activated carbon. Synthesis methods and functions vary greatly due to different kinds of support and catalytic materials. The challenge in making a supported nanoparticulate catalyst is to avoid agglomeration. This can be achieved by using a poly-functional anchoring agent, and drying under a relatively low temperature. Relative research are deposition of palladium and platinum particles on activated carbon, using a poly-acrylate anchor. To unveil more molecular details of the extensive interactions between precursors and supports in an aqueous environment, studies of adsorption and precipitation chemistry must be taken into account. Progress is being made in the use of chemical vapor deposition for the synthesis of supported catalysts. Combinatorial techniques have seen their contributions to solid catalyst synthesis. Catalysts are widely used in various chemical reactions. The activity, stability, selectivity, and regeneration ability are the most important properties to be considered in catalyst design. The catalyst supports can improve specific properties such as mechanical strength, distribution, stability, catalytical reactivity and selectivity of catalysts. The definition of the support is broad: the shape of support varies, including granular, powdered, colloidal, coprecipitated, extruded, pelleted, spherical, wires, honeycombs, and skeletal supports. Catalyst supports can be either inert or active in reactions. The ensemble of the catalyst and its support can be regarded as an entirety: supported catalyst. In pre-1940 publications, the supports were only considered as physical carriers on which the catalytic metal or oxide was disposed as broadly and uniformly as possible. But over the years, a better understanding of the cofunctioning of catalysts and their supports has been achieved. It was recognized that the support was actually a promoter in many cases. In Catalysis (Berkman et al. 1940), the difference between a promoter and a support is described as the difference in quantity: when the support exceeds the quantity of the catalyst, it is a support; otherwise it is a promoter. This view was more or less simplistic, but implied the recognition that even at this early year the support was a catalytic component in the broadly construed catalytic composition. An early purpose of the support was to obtain a solid granular material coated with catalytic component, providing a hard and stable structure to withstand disintegration under gas or liquid flows. Another purpose to load catalytical noble metal on supports is to dilute noble metals in a larger volume. Some supports act as a stabilizer to prevent lower-melting-point materials from agglomeration. Another use of the support was to serve as a reservoir for semimolten salts. Many experiments about alumina were conducted at the early period, which helped people to realize that catalysts supported on different species of alumina have different catalytic properties. During the same time frame, it was noticed that the catalyst and the support were cooperating in some cases to produce two simultaneous and mutually beneficial reactions. This was called the dual-functioning catalyst and was observed in those hydrodenitrogenation, hydrodesulfurization, and reforming catalysts reactions. Carbon is a ubiquitous element that forms millions of compounds, ranging from simple carbon monoxide to highly complex enzymes. Regarding to its elemental form, although there is no catalytic properties ascribed to diamond, graphite is known to be an active catalyst in some oxidation reactions. Graphitic carbon is also used as a support material where other catalytic components may be dispersed, resulting in an increase of the surface area they expose to the chemical reactants.