CATALYST EFFECTIVENESS FOR MULTICOMPONENT REACTIONS WITH CONCENTRATION-DEPENDENT DIFFUSIVITIES

The diffusion coefficient,D_i has been formulated of the reacting species in the transition region of diffusion for a stoichiometricly simple isothermal reaction in a porous catalyst and its concentration dependence has been determined. The concentration dependence of D_i incorporated into the mass balance of the catalyst pellet introduces a new parameter, A (Eq. 11). The effect is demonstrated of this parameter on predicted values of effectiveness factors for three kinetic equations of the Langmuir-Hinshelwood type (Eq. 36-38). If the effectiveness factor is a monotonously decreasing function of the Thiele Modulus, or if the concentration dependence of D_i is not too strong, the effectiveness factor can be predicted from the solution of mass balance with concentration independent diffusivity. This prediction can be improved by using a mean diffusion coefficient D_i.     

Epoxydationen mit Peressigsäure I: Zur Kenntnis der Peressigsäure und vergleichende Epoxydationen von Sojabohnenöl

Epoxidations with Peracetic Acid I: The Peracetic Acid and Related Epoxidations of Soybean Oil Progressive formation of peracetic acid by the action of hydrogen peroxide on acetic acid was studied. In the presence of ethyl acetate and by employing acetic anhydride, water free peracetic acid was obtained. In the epoxidation of soybean oil the maximum epoxide content of the same is dependent on the reaction conditions, especially on the degree of homogeneity of the reaction partners and the acidic catalyst.     

Ca15(CBN)6(C2)2O- a new cubic structure type containing CBN-anions together with acetylide and oxo anions

Ca₁₅(CBN)₆(C₂)₂O contains CBN⁴⁻ anions as well as C₂⁻ units and isolated O²⁻ anions. The compound is obtained by heating a stoichiometric mixture of CaO, C and BN with an excess of Ca in sealed niobium ampoules to 1270 K. It crystallizes in the space group Ia d with a = 1656.84(9) pm. Preparation, crystal structure, NMR and IR-spectroscopic properties are discussed.     

Living dispersion polymerization of styrene in the presence of polystyrene-block-poly(4-trimethylsilylstyrene)

Summary Living polystyrene microparticles with average particle diameters varying between 0.5 and 3.8 m were obtained via sec-butyl lithium-initated anionic polymerization of styrene in n-hexane diluent when polystyrene-block-poly(4-trimethyl-silylstyrene) was added as dispersing agent. The influence of block copolymer molecular architecture and concentration as well as polymerization temperature, monomer concentration and THF addition on polystyrene particle size, molecular weight and molecular weight distribution were investigated. In comparison to anionic styrene polymerization in cyclohexane solution, the anionic styrene dispersion polymerization in n-hexane was markedly slower.