Activated carbon route

Selected metal oxides prepared by the activated carbon route. For further information see... 

Schwickardi, M Johann, T., Schmidt, W., and Schuth, F. (2002) High-surfece-area oxides obtained by an activated carbon route. Chem. Mater., 14 (9), 3913-3919. 

Figure 5.16 Photoactivation of a phenyl azide group with UV light results in the formation of a short-lived nitrene. Nitrenes may undergo a number of reactions, including insertion into active carbon-hydrogen or nitrogen-hydrogen bonds and addition to points of unsaturation in carbon chains. The most likely route of reaction, however, is to ring-expand to a dehydroazepine intermediate. This group is highly reactive toward nucleophiles, especially amines.

Which has been studied on supported Ni catalysts and on Ni films . Studies such as those described here show that methane can be catalytically synthesized over Ni by an active (carbidic) carbon formed via the Boudouard reaction and its subsequent hydrogenation to methane. However, to demonstrate that this surface carbon route is the major reaction pathway, kinetic measurements of both carbon formation from CO and its removal by H2 were carried out . 

It was found that a nickel-activated carbon catalyst was effective for vapor phase carbonylation of dimethyl ether and methyl acetate under pressurized conditions in the presence of an iodide promoter. Methyl acetate was formed from dimethyl ether with a yield of 34% and a selectivity of 80% at 250 C and 40 atm, while acetic anhydride was synthesized from methyl acetate with a yield of 12% and a selectivity of 64% at 250 C and 51 atm. In both reactions, high pressure and high CO partial pressure favored the formation of the desired product. In spite of the reaction occurring under water-free conditions, a fairly large amount of acetic acid was formed in the carbonylation of methyl acetate. The route of acetic acid formation is discussed. A molybdenum-activated carbon catalyst was found to catalyze the carbonylation of dimethyl ether and methyl acetate. 

Groppi and co-workers46,26 investigated the catalytic activity of Mn- and Fe-substituted hexaaluminates prepared via the carbonate route for CO and H2 combustion. These species are the main components of fuels from gasification of carbon and biomasses that represent an alternative to natural gas in gas turbine applications. 

C02, at concentrations to effect the Boudoir equilibrium, cleaner surfaces were obtained. Ledoux et al., recently prepared carbides by depositing metal oxide vapors at 1373 K under vacuum over high surface area, 1200 m2 g-1, activated carbon. Carbides with Sg between 100-400 m2 g 1 were claimed.6 A comparison of several W03-based synthetic routes was made by Iglesia et al.1... 

Foul-smelling fumes from the crude sulfate turpentine escaped the tanks both during tank fillings and during the daytime, when the sun increased the tank temperature. Malodorous tank vapors were routine. Company personnel planned to solve the problem by routing these offensive fumes to drums with activated carbon. [11,12]... 

A large number of intermediate pathways arc possible when catalytic reactions interfere with the polymerization-dehydrogenation steps. A common scenario is the catalytic dehydrogenation of hydrocarbons on nickel surfaces followed by dissolution of the activated carbon atoms and exsolution of graphene layers after exceeding the solubility limit of carbon in nickel. Such processes have been observed experimentally [40] and used to explain the shapes of carbon filaments. In the most recent synthetic routes to nanotubes [41] the catalytic action of in situ-prepared iron metal particles was applied to create a catalyst for the dehydrogenation of cither ethylene or benzene. 

A unique active carbon having very high surface areas over 2500 m / gm, and extraordinary adsorptive capacities was developed in our laboratories. (1) This paper will describe its development, manufacture, properties, and uses. Until recently, samples of this carbon, which were provided worldwide for research and evaluation, were identified as Amoco Grades PX-21, 22, 23, and 24 in the powdered form and Amoco GX-31 and 32 in granular form. The carbon is made (Figure 1) by a direct chemical activation route in which petroleum coke or other carbonaceous sources are reacted with excess potassium hydroxide, KOH, at 400° to 500°C to an intermediate product that is subsequently pyrolyzed at 800°-900°C to active carbon and potassium salts. The salts are removed by water washing. 

An exceptional active carbon has been developed with a high effective surface area and high adsorptive capacity. It is prepared by a controlled chemical activation route using potassium hydroxide and a carbonaceous source, usually petroleum coke, to give a consistent quality product. It has been tested in a gamut of conventional and new uses with performance ratios averaging 2 to 4 times better than other grades of active carbon. Because of its unique structure and properties, it is likely that many new uses will be developed as it now becomes commercially available. 

These easily-made carbonates have become useful intermediates for (i) the direct synthesis of cyclic carbonates via the Heck reaction [82] (ii) optically active carbonates by enantioselective hydrogenation [83] and (iii) to oxazolidinones [84, 85] as an alternative route to the Evans reagent [86-88]. 

Relatedly, there has been a corresponding increase in research and development, as reflected by the large number of papers that are presented at the various carbon conferences. Advances in activated carbons are expected to emanate from using alternative synthesis routes and precursors, from the development of new forms, and through techniques to modify surface chemistry. Some examples are given in the following sections. 

The selectivity of activated carbons for adsorption and catalysis is dependent upon their surface chemistry, as well as upon their pore size distribution. Normally, the adsorptive surface of activated carbons is approximately neutral, such that polar and ionic species are less readily adsorbed than organic molecules. For many applications it would be advantageous to be able to tailor the surface chemistry of activated carbons in order to improve their effectiveness. The approaches that have been taken to modify the type and distribution of surface functional groups have mostly involved the posttreatment of activated carbons or modification of the precursor composition, although the synthesis route and conditions can also be employed to control the properties of the end product. Posttreatment methods include heating in a controlled atmosphere and chemical reaction in the liquid or vapor phase. It has been shown that through appropriate chemical reaction, the surface can be rendered more acidic, basic, polar, or completely neutral [11]. However, chemical treatment can add considerably to the product cost. The chemical composition of the precursor also influences the surface chemistry and offers a potentially lower cost method for adjusting the properties of activated... 

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