Silica reactor

Specimens were placed in a silica reactor that was equipped with two side tubes for XPS and ESR measurements and connected to a circulation apparatus, described elsewhere [25, 26]. The catalysts, dried at 383 K, were characterized as prepared (a.p.), after heating in dry oxygen at 773 K (s.o.), or after reduction with CO. In some experiments, as specified, samples were exposed to NO, NH3, or various mixtures NO-O2-NH3. Electrons per V atom (e/V) were determined from the CO consumed. The average oxidation number of vanadium was calculated as 5 - eA/. 

Atmospheric pressure apparatus. Isomerization experiments at atmospheric pressure were carried out in an all-glass system equipped with greaseless values, a flow meter, a U-shaped silica reactor, a double TCD system recording the pressure of reactant (provided by a saturator) before the reactor and the pressure of the products after the reactor, a system to extract the products for GC analysis and a needle valve to regulate gas flow. The catalyst was placed on a silica fritted disc and the reactor was operated as a fixed bed at constant pressure and temperature. Hydrocarbons were introduced at a set pressure and hydrogen was used as complement to the atmospheric pressure on the catalyst. 

Syathesis of Perfluoro Aromatic Radical Cation Salts. Hexafluoro-benzeae Hexafluoroiridate(V). Hexafluorobenzene (2.6 mmol) was dissolved in tungsten hexafluoride (2 mL) in a fused silica reactor to give a yellow-green solution. Iridium hexafluoride (2 mmol) was condensed into the reactor at 77 K. At about 273 K, the reaction mixture melted, and a bright orange solid rose to the surface of the WFg. The solvent and excess CgF were removed under vacuum at 298 K. The dry orange solid decomposed rapidly, producing volatile carbon fluorides. Some of the iridium was reduced to the metal. 

An early example by Reetz and co-workers [79] demonstrated the evaluation of a series of biocatalysts for the hydrolytic kinetic resolution of chiral glycidyl phenyl ethers. Employing a fused-silica reactor, the authors developed an integrated reaction system capable of performing biocatalytic hydrolysis, along with separation and detection of the reaction products. Using the enantioselective hydrolysis of 2-phenoxymethyloxirane (136) to 3-phenoxypropane-l,2-diol (137) as a model reaction (Table 6.14), the authors evaluated the biocatalytic activity of a series of epoxide... 

In the absence of significant electronic interactions with the support, a justifiable assumption for Pt/silica catalysts, a further potential influence of the catalyst support on the reaction kinetics is hydrogen spillover and diffusion on silica. In order to develop a model for the spillover and diffusion of hydrogen on silica a temperature programmed desorption (TPD) study of deuterium desorption from silica was conducted. The TPD experiments were conducted using a narrow bore silica reactor in a small furnace. The catalysts were first reduced in-situ in deuterium at the reduction temperature for 1 hour and then cooled to ambient temperature, again in deuterium. The reactor was then evacuated and heated at 20°C/min. Analysis of the desorbed gases was mass-spectrometer. 

Redox experiments and ESR determination of Cu2+ were performed with a circulation all-glass apparatus equipped with a magnetically driven pump. The sample (0.2 to 1.0 g) was placed in a silica reactor equipped with a side ESR tube. All the samples before the redox cycles were treated in O2 at 773 K. The redox cycles consisted of (i) heating in He flow at 823 K for 2h, followed by evacuation at 773 K and heating in O2 at 773 K (ii) evacuation at RT followed by reduction with CO at 773 K (iii) evacuation at 773 K followed by a second treatment with O2 at 773 K. During the treatments (i) to (iii), the pressure of O2 or CO was monitored with a pressure transducer (MKS Baratron, sensitivity 1 Pa) until a nearly constant pressure was reached. All these measurements allowed the variation of the average oxidation number of copper to be followed. The acquisition or loss of electrons are expressed as e/Cu (number of electrons/total number of Cu atoms). At the end of treatments (i) to (iii), ESR spectra of Cu2+ species were recorded at RT. ESR measurements were carried out on a Varian E-9 spectrometer equipped with an on line computer. Absolute concentrations of... 

The synthesis of the patterned macroscopic shape consists in the growth of carbon nanotubes in a parallel direction from a fiat substrate surface. This was achieved using a mixture of toluene containing ferrocene compounds or directly with ethylene and steam etching [46-49]. The carbon nanotubes were formed as a thick layer covering the silica reactor wall. The sample could easily be recovered by scratching the dark deposit with a razor blade. 

Fiber optics, silica reactors, = 1450°C Solid electrolyte... 

For glass or silica reactors, the filament temperature is measured by means of an optical pyrometer and the current is increased as the rare metal... 

Osmieri L, Videla AHAM, Armandi M, Specchia S (2015) A micro-silica reactor (pSi02-R) able to produce highly porous non-noble catalysts for oxygen reduction reaction under alkaline conditions. In challenges towards zero platinum for oxygen reduction. La Grande Motte (France) 14-16/09/2015... 

Figure 8.16 shows a methanol/water vaporiser, followed by a catalytic steam reformer operating at about 250°C, in which the catalyst is a thin film of Cu/ZnO coated onto the silica reactor, and finally a membrane shift reactor consisting of a palladium diffusion layer mounted on top of a perforated copper-based shift catalyst. Built onto the chip are integrated resistive heaters for getting the reformer and vaporiser up to temperature, together with micro-scale sensors and control electronics. Whilst such systems are a long... 

Lupetti, K. O., I. C. Vieira, and O. Fatibello-Filho. 2002. Flow injection spectrophoto-metric determination of isoproterenol using an avocado (Persea americana) crude extract immobilized on controlled-pore silica reactor. Talanta 57 135-143. 

Methane, chlorine, and recycled chloromethanes are fed to a tubular reactor at a reactor temperature of 490—530°C to yield all four chlorinated methane derivatives (14). Similarly, chlorination of ethane produces ethyl chloride and higher chlorinated ethanes. The process is employed commercially to produce l,l,l-trichloroethane. l,l,l-Trichloroethane is also produced via chlorination of 1,1-dichloroethane with l,l,2-trichloroethane as a coproduct (15). Hexachlorocyclopentadiene is formed by a complex series of chlorination, cyclization, and dechlorination reactions. First, substitutive chlorination of pentanes is carried out by either photochemical or thermal methods to give a product with 6—7 atoms of chlorine per mole of pentane. The polychloropentane product mixed with excess chlorine is then passed through a porous bed of Fuller s earth or silica at 350—500°C to give hexachlorocyclopentadiene. Cyclopentadiene is another possible feedstock for the production of hexachlorocyclopentadiene. 

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

Cells used for high-temperature measurements in furnaces often consist of silica sample tubes, supported by thin vanadium sleeves. The key to the analysis is whether it is possible to have a container that scatters in a sufficiently predictable way, so that its background contribution can be subtracted. With the current neutron flux available from both pulsed and reactor sources, sample volumes of... 

Other catalyst systems such as iron V2O5-P2O5 over silica alumina are used for the oxidation. In the Monsanto process (Figure 6-4), n-butane and air are fed to a multitube fixed-bed reactor, which is cooled with molten salt. The catalyst used is a proprietary modified vanadium oxide. The exit gas stream is cooled, and crude maleic anhydride is absorbed then recovered from the solvent in the stripper. Maleic anhydride is further purified using a proprietary solvent purification system. ... 

Monochlorohenzene is also produced in a vapor-phase process at approximately 300°C. The hy-product HCl goes into a regenerative oxychlorination reactor. The catalyst is a promoted copper oxide on a silica carrier ... 

High-density polyethylene (HDPE) is produced by a low-pressure process in a fluid-bed reactor. Catalysts used for HDPE are either of the Zieglar-type (a complex of A1(C2H5)3 and a-TiCl4) or silica-alumina impregnated with a metal oxide such as chromium oxide or molybdenum oxide. 

A conventional FCC unit can be an olefin machine with proper operating conditions and hardware. Catalysts with a low unit cell size and a high silica/alumina ratio favor olefins. Additionally, the addition of ZSM-5, with its lower acid site density and very high framework silica-alumina ratio, converts gasoline into olefins. A high reactor temperature and elimination of the post-riser residence time will also produce more olefins. Mechanical modification of the FCC riser for millisecond cracking has shown potential for maximizing olefin yield. 

A platinum on silica gel catalyst was prepared by impregnation of silica gel (BDH, for chromatographic adsorption) by a solution containing 0.5% (wt.) of sodium hydroxide and 0.5% (wt.) of chloroplatinic acid (both of analytical grade). The dried catalyst contained 1% (wt.) of platinum and a corresponding amount of the alkaline component. The BET surface area of the catalyst was 40 m2/g, the mean pore radius 150 A. The catalyst was always reduced directly in the reactor in a stream of hydrogen at 200°C for 2 hr. 

A three-step nitration process of toluene is described. The advantages of the modified process are reduced waste, less hazardous operation, reduced oleum requirement, partial replacement of coned HN03 with dil HN03, and higher rate of toluene flow into the reactor (Ref 86) The continuous process of H.C. Prime (Ref 73) for preparing TNT was studied by thin-layer chromatography on silica gel with a starch binder and a fluorescent indicator. The nitration... 

Epoxides such as ethylene oxide and higher olefin oxides may be produced by the catalytic oxidation of olefins in gas-liquid-particle operations of the slurry type (S7). The finely divided catalyst (for example, silver oxide on silica gel carrier) is suspended in a chemically inactive liquid, such as dibutyl-phthalate. The liquid functions as a heat sink and a heat-transfer medium, as in the three-phase Fischer-Tropsch processes. It is claimed that the process, because of the superior heat-transfer properties of the slurry reactor, may be operated at high olefin concentrations in the gaseous process stream without loss with respect to yield and selectivity, and that propylene oxide and higher... 

The synthesis of imidazoles is another reaction where the assistance of microwaves has been intensely investigated. Apart from the first synthesis described since 1995 [40-42], recently a combinatorial synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles has been described on inorganic solid support imder solvent-free conditions [43]. Different aldehydes and 1,2 dicarbonyl compounds 42 (mainly benzil and analogues) were reacted in the presence of ammonium acetate to give the trisubstituted ring 43. When a primary amine was added to the mixture, the tetrasubstituted imidazoles were obtained (Scheme 13). The reaction was done by adsorption of the reagent on a solid support, such as silica gel, alumina, montmorillonite KIO, bentonite or alumina followed by microwave irradiation for 20 min in an open vial (multimode reactor). The authors observed that when a non-acid support was used, addition of acetic acid was necessary to obtain good yields of the products. 

An alternative route to phthalic anhydride is the partial oxidation of naphthalene. The heat of reaction is — 430 kcal/mol. This reaction can be performed using a promoted V2O5 catalyst on silica, much like that considered in Example 9.1. Suppose In(fik) = 31.6800—19,100/T for the naphthalene oxidation reaction and that the subsequent, complete oxidation of phthalic anhydride follows the kinetics of Problem 9.3. Suppose it is desired to use the same reactor as in Example 9.1 but with a,>, = 53g/ m. Determine values for and T aii that maximize the output of phthalic anhydride from naphthalene. 

---