Catalyzed slurry oxidation

We have demonstrated that supported Pd and Cu catalysts are effective in catalyzing the oxidative carbonylation at low pressure reaction condition and the supported metal catalysts can be easily separated from the product mixture in both fixed bed and slurry phase reactors (12,17). The objective of this study is to investigate the feasibility of using Al203-supported Pd catalysts for catalyzing the reductive carbonylation of nitrobenzene with ethanol. 

By incorporating the film theory into the mathematical model for the batch slurry oxidation, a mass transfer coefficient of 0.015 cm/sec was obtained by matching the model to highly catalyzed (2000 ppm Mn added) slurry oxidation data. Saturation concentration of sulfite is most important in determining mass transfer coefficient(32). A correlation is given... 

Hiatt, C.W., Haskins, W.T., Olivier, L. (1960) The action of sunlight on sodium pentachlorophenate. Am. J. Trop. Med. Hyg. 9,527-531. Hidaka, H., Nohara, K., Zhao, J., Serpone, N., Pelizzetti, E. (1992) Photo-oxidative degradation of the pesticide permethrin catalyzed by irradiated Ti02 semiconductor slurries in aqueous media. J. Photochem. Photobiol. A Chem. 64, 247-254. 

Refractory high surface area oxides are deposited from slurries onto the walls of the channels that make up monoliths in order to provide an adequate surface area to support the active catalytic species. Washcoats such as AI2O3 and TiC>2 are commonly used for pollution abatement applications (auto exhaust, stationary NO abatement, etc.) where the monolith is usually a ceramic. Metal monoliths are finding increasing use however, they represent only a small percentage of the total monoliths used. Optical microscopy enables one to see that the catalyzed washcoat follows the contour of the ceramic surface. Figure 7 shows the AI2O3 washcoat-ceramic interface for a typical auto exhaust catalyst. In this case, no evidence of loss of adhesion between washcoat and ceramic can be seen. 

The checkers discovered that the desired hydroxy acid Is sensitive to strong acid and heat. Early runs of Part B by the checkers using the original conditions recommended by the submitters involved stirring the bisulfite slurry at room temperature for 3-4 hr, simple partitioning without an aqueous backwash and drying of the bisulfite oxidation mixture, and distillation of the product at 0.8 mm reduced pressure. These runs consistently resulted in acid-catalyzed transformation, either 1n the workup... 

The oxidation and reduction steps in the RAQ/RAHQ cycle are performed in two separate reactors. A bubble column is applied for the oxidation of the RAHQ, during which HP is produced. For the Pd-catalyzed hydrogenation of the quinones, a slurry, fixed-bed or monolith reactor can be used. After the reactor and L/L settler, a diluted H P-containing water-methanol stream is finally obtained. After the epoxidation step, crude PO is separated and the water-methanol mixture is returned to the HP synthesis process, thus realizing an efficient process integration. 

The key issue in effective catalytic oxidation of organics is finding a suitable catalyst. Oxidation of aqueous phenol solutions by using different transition metal oxides as heterogeneous catalysts is already known [4-6]. On the other hand, the potential of molecular sieves to catalyze oxidative phenol destruction has not been examined yet. The objective of this contribution is to provide kinetic and mechanistic data on the catalytic liquid-phase oxidation of aqueous phenol solutions obtained in the presence of various transition metal oxides and molecular sieves. The reaction was studied in a semibatch slurry as well as two-and three-phase continuous-flow reactors. Another matter of concern was the chemical stability of catalysts under the reaction conditions. 

Oxidation of sulfite to sulfate can proceed by mechanisms other than those involving oxygen from air. The reaction kinetics and the mechanics are not yet understood, but our experiments show that oxygen-free sulfite in lime/limestone slurries, exposed to sulfur dioxide, slowly decomposes under process conditions. In fact, our experiments indicate that auto-redox reactions of sulfur oxyacids can occur in all coal desulfurization systems, including coal-gasification systems and that impurities present in commercial flue gas systems are capable of catalyzing the reaction under process conditions. 

The current model is a step closer toward a reliable working description of the sulfite oxidation rate in scrubber slurries. By incorporating a boundary layer description of the film around each particle, this model predicts the conditions at the particle surface which drive the mass transfer. The interfacial area for mass transfer was discovered to be more closely represented by a sphere than by a plate-like shape. From the model, using highly catalyzed experiments, a mass transfer coefficient of 0.015 cm sec-1 was found - quite close to literature correlation predictions. 

A considerable amount of work has been done on the oxidation of sulfite and bisulfite anions in aqueous solutions (25). In this paper the discussion is limited to oxidation of calcium sulfite (9), which has received much less attention than oxidation of sodium salts. The attention here is on the oxidation of calcium sulfite, catalyzed by metal ions in the presence of organic acid buffers, occuring in solid-liquid-gas slurry reactors. The organic acid buffers not only moderate pH changes during the reaction, but also inhibit the rate of chemical reaction (10). 

The widely investigated Phillips catalyst, which is alkyl free, can be prepared by impregnating a silica-alumina (87 13 composition [101-103] or a silica support with an aqueous solution of Cr03). High surface supports with about 400 to 600 g/m are used [104]. After the water is removed, the powdery catalyst is fluidized and activated by a stream of dry air at temperatures of 400 to 800 °C to remove the bound water. The impregnated catalysts contain 1 to 5wt% chromium oxides. When this catalyst is heated in the presence of carbon monoxide, a more active catalyst is obtained [105]. The Phillips catalyst specifically catalyzes the polymerization of ethene to high-density polyethene. To obtain poly ethene of lower crystallinity, copolymers with known amounts of an a-olefin, usually several percent of 1-butene ean be synthesized. The polymerization can be carried out by a solution, slurry, or gas-phase (vapor phase) process. 

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