Selective oxidation of n-butane to maleic anhydride under oxygen-deficient conditions over V-P-O mixed oxides

The selective oxidation of n-butane to maleic anhydride over V-P-O mixed oxides was studied under oxygen deficient conditions. The mixed oxides were prepared with P/V atomic ratios ranging from 0.7 to 1.0. Catalysts with P/V <1.0 did not show any selectivity to maleic anhydride formation, regardless of whether or not (VO)2P2O7 was present. For catalysts with P/V = 1.0, containing (VO)2P2O7 and/or the so-called. β-phase, the selectivity was strongly influenced by the actual surface V5+/V4+ ratio. This ratio is determined by the temperature, the crystal phases present in the catalyst and the composition of the gas mixture. Optimal selectivity was obtained at 425°C with 15% butane in air and a butane/oxygen ratio of 0.9

Gas-liquid mass transfer with parallel reversible reactions—I. Absorption of CO2 into solutions of sterically hindered amines

A numerical method developed by Verteeg (1989, Chem. Engng Sci.44, 2295–2310; 1990, Chem Engng Sci.45, in press) is applied to some specific problems in gas—liquid mass transfer. The experimental results of Chakraborty (1986, Chem. Engng Sci.41, 997–1003) and Zioudas and Dadach (1986, Chem. Engng Sci.41, 405–408) on the absorption of Co2 into aqueous solutions of sterically hindered amines are evaluated with the numerical model. It is shown that studying the absorption of CO2 into aqueous solutions of sterically hindered amines requires a rigorous numerical solution of the differential equations describing the mass transfer instead of analytical and numerical approximations based on a reduction of the number of reactions by neglecting or lumping reactions. It is demonstrated that the absorption rates of CO2 into sterically hindered amine solutions can be explained in terms of the established reactions rates of CO2 in amine solutions alone, and no new reaction paths are necessary to explain the observed behaviour

Gas-liquid mass transfer with parallel reversible reactions—II. Absorption of CO2 into amine-promoted carbonate solutions

A numerical method developed by Verteeg (1989, Chem. Engng Sci.44, 2295–2310; 1990, Chem. Engng Sci.45, in press) is applied to the absorption of CO2 into amine-promoted carbonate solutions. The experimental results of Savage (1984, Faraday Discuss. Chem. Soc.77, 17–31) are evaluated with the numerical model. It is shown that a rigorous numerical solutions of the differential equations describing the mass transfer gives more insight into the actual process than analytical and numerical approximations based on a reduction of the number of reactions by neglecting or lumping reactions

Gas-liquid mass transfer with parallel reversible reactions—III. Absorption of CO2 into solutions of blends of amines

A numerical method developed by Versteeg (1989, Chem. Engng Sci.44, 2295–2310; 1990, Chem. Engng Sci.45, in press) is applied to the absorption of Co2 into solutions of blends amines. The experimental results of Critchfield and Rochelle (1987) are evaluated with the numerical model. It is shown that a rigorous numerical solution of the differential equations describing the mass transfer gives more insight into the actual process than analytical approximations based on a reduction of the number of reactions by neglecting or lumping reactions

Studies on tableting properties of lactose. Part III. The consolidation behaviour of sieve fractions of crystalline a-lactose\ud monohydrate

The consolidation and compaction behaviour of sieve fractions of crystalline α-lactose monohydrate were studied. From mercury porosimetry measurements tablet pore surface areas were derived. At a certain compaction load it appeared that tablets compressed from small particles were generally stronger and showed a larger surface area than compacts prepared from coarse sieve fractions. By plotting compact strength against pore surface area, a unique linear relationship was obtained. From these results it can be concluded that the actual tablet surface area, being a function of both the initial particle size and applied compaction pressure, is responsible for the compact strength