The gas-phase epoxidation of 2-butene (trans or cis) has been conducted in a flow-through reactor at a pressure of 0.5 bar and a temperature of 325 °C using a N2/O2 mixture as the carrier gas. The primary oxidizing agent in the feed gas is ozone. Selectivity to epoxide (trans- and cis-epoxide in total) of about 90% is observed. Investigations using mixtures of trans-2-butene with 1-butene or n-butane revealed a clearly preferred reaction of trans-2-butene. Kinetic analysis of the overall process yielded ratios for the corresponding rate coefficients of k(trans-2-butene)/k(1-butene) = 5.4−7.2 and k(trans-2-butene)/k(n-butane) ∼ 67. A few experiments showed a similar behavior for cis-2-butene. Using raffinate 2 (1-butene, 2-butene, n-butane, and iso-butane) as the feedstock for epoxidation, a selective production of 2-butene oxide (trans/cis mixture) is feasible. Additions of methane (1.7−12.5 vol %), H2O vapor (1.7−4.2 vol %), or CO2 (1.7−25 vol %) in the carrier gas do not influence the epoxidation reaction.
Drying porous asymmetric ultrafiltration membranes can be accomplished either through the dense skin or the porous bottom side. In both cases the opposite side of the membranes is made tight by a flat plate. When the water is transported through the dense skin only one constant drying period and one period of falling rate can be observed, whereas for the drying through the porous sublayer two constant and two falling rate periods can be seen. Using a modified two capillary model for the drying behavior the water transport through both sides of the membranes and the surface porosity can be estimated.
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