Oxidation isobutane product distribution

An interesting variation on sulfated metal oxide type catalysts was presented by Sun et al. (198), who impregnated a dealuminated zeolite BEA with titanium and iron salts and subsequently sulfated the material. The samples exhibited a better time-on-stream behavior in the isobutane/1-butene alkylation (the reaction temperature was not given) than H-BEA and a mixture of sulfated zirconia and H-BEA. The product distribution was also better for the sulfated metal oxide-impregnated BEA samples. These results were explained by the higher concentration of strong Brpnsted acid sites of the composite materials than in H-BEA. 

After activation, the catalyst is intrcxiuced into the polymerization reactor as slurry in a saturated hydrocarbon such as isobutane. The precise mechanism of initiation is not known, but is believed to involve oxidation-reduction reactions between ethylene and chromium, resulting in formation of chromium (II) which is the precursor for the active center. Polymerization is initially slow, possibly because oxidation products coordinate with (and block) active centers. Consequently, standard Phillips catalysts typically exhibit an induction period. The typical kinetic profile for a Phillips catalyst is shown in curve C of Figure 3.1. If the catalyst is pre-reduced by carbon monoxide, the induction period is not observed. Unlike Ziegler-Natta and most single site catalysts, no cocatalyst is required for standard Phillips catalysts. Molecular weight distribution of the polymer is broad because of the variety of active centers. 

A detailed kinetic study of oxidative dehydrogenation of propane, isobutane, n-butane (23 runs) and LPG (27 runs) was conducted over a wide range of partial pressures of pure and mixed hydrocarbons (0-0.3 atm), oxygen (0-0.2 atm) and steam (0.2-0.7) atm and temperature 600-670°C. Oxidation of Hj, CjHg, C H, CH and CO was also tested at 600-650°C. A set of reactions was selected based on the distribution of products ... 

The slurry reactor was developed by Hochst to make polyethylene using Ziegler catalysts. The reaction medium, called a diluent , is a hydrocarbon that is a solvent for the monomer but not for the polymer. The product is thus formed as a suspended powder. Bimodal products, i.e., products that are, in effect, blends of two polymers having distinctly different molecular weight distributions, can be made using a cascade of two reactors in which the reaction conditions are substantially different [116]. Phillips Petroleum later developed a pipe-loop slurry reactor for use with its chromium oxide catalyst, which required moderately high temperatures and pressures to accommodate the isobutane diluent used. 

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