Gas to Solid Synthesis

The most commonly used technique of gas to solid synthesis involves the condensation of a vapour produced by the heating of a solid or a liquid starting material. This technique is very popular in preparation of thin films and nanopartides. A model of an apparatus is shown in Figure 3.7. This comprises an... 

The biomass is first processed by thermochemical methods (gasification, pyrolysis), for example, to form synthesis gas, which can be processed further to methanol or Fischer-Tropsch (FT-) hydrocarbons. To gasify solid biomass, both circu-... 

JG Adamson, T Hoang, A Crivici, GA Lajoie. Use of Marfey s reagent to quantitate racemization upon anchoring of amino acids to solid supports for peptide synthesis. Anal Biochem 202, 210, 1992. 

Increasingly chemists are contributing to the synthesis of advanced materials with enhanced or novel properties by using colloidal assemblies as templates. Colloid chemistry is particularly well suited to this objective since nanoparticles, by definition, are colloidal and since processing of advanced materials involve reactions at solid-solid, solid-liquid or solid-gas interfaces (3-5). 

In an interesting application of a gaseous reagent to solid-phase synthesis, Takahashi and co-workers demonstrated hydroformylation of an unactivated alkene using synthetic gas (1 1 H2-CO) and a Rh(I) catalyst (Scheme 8).22 The reaction was typically performed at 40°C in toluene at a pressure of 75 atm. Conversions of 99% were obtained following careful reaction optimization. Variation in the concentration of catalyst could be used to alter the regioselectivity of the reaction. 

Matrix isolation methods of synthesis have also been used to prepare and study coordination compounds. These involve the vaporization of a metal and a potential ligand, which are then rapidly carried in a stream of inert gas to a very cold surface, where the compound which has been formed is quickly trapped in the solid matrix. It is possible to determine the type of bonding, the structure and the thermodynamic properties of the compounds formed. Only small ligand molecules have been used thus far carbon monoxide, nitric oxide, nitrogen and oxygen, for example, but molecules of great interest have been formed. Some such are [Pd(C2H4)], [Pd(N2)3], [Ni(N2)202], [Ni(N2)4] and [Ni(CO)(N2)3].41... 

Gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are widely used in the chemical and petrochemical industries for processes such as methanol synthesis, coal liquefaction, Fischer-Tropsch synthesis and separation methods such as solvent extraction and particle/gas flotation. The hydrodynamic behavior of gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are of great importance for the design and scale-up of reactors. Although the hydrodynamics of the bubble and slurry bubble columns has been a subject of intensive research through experiments and computations, the flow structure quantification of complex multi-phase flows are still not well understood, especially in the three-dimensional region. In bubble and slurry bubble columns, the presence of gas bubbles plays an important role to induce appreciable liquid/solids mixing as well as mass transfer. The flows within these systems are divided into two... 

A gasifier is used to produce synthesis gas from carbonaceous material. The solid is packed in a column, and gas is passed up through the bed, producing a mixture of combustible products, primarily methane, hydrogen and carbon monoxide, with a low to medium BTU content. 

As a strategy, the synthesis procedure should start with vapor recovery and gas separations, from which some components are sent to liquid separations. For the same reason, the solid-separation system should be placed in the second place. Note that the subsystems of gas and solid separations are largely uncoupled. As a result, the liquid-separation system should is handled the last. 

Today, solid-catalyzed gas reactions are executed to an extent of several billions of tonnes per annum. To name only a few important examples Steam reforming of methane-rich natural gas to synthesis gas (H2 + CO), conversion of CO with H20 to C02 + H2, conversion of CO with H2 to methane, ammonia synthesis, oxidation of S02 to S03 (sulphuric acid production), oxidation of NH3 to NO (nitric acid production). The world production of ammonia in 1995 amounted to 90 m tonnes and... 

Since the concept of topochemically controlled reactions was established, various approaches to asymmetric synthesis using a solid-state reaction have been attempted, most actively by the research group at the Weismann Institute. Their studies have been concerned with the bimolecular reactions of chiral crystals in the solid state. In these studies, successful absolute asymmetric synthesis has been performed by using topochemically controlled four-centered photocyclodimerizations of a series of unsymmetrically substituted diolefin crystals. Research on reactivity in the crystalline state has been extended in recent years to a variety of new systems, and many absolute asymmetric syntheses have been provided. Successful examples of absolute asymmetric synthesis using chiral crystals are listed in Tables 2 to 4, which are divided into three categories intermolecular photoreaction in the solid state (Table 2), intramolecular photoreaction in the solid state (Table 3, A-D), and asymmetric induction in the solid-gas and homogeneous reactions (Table 4). 

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