To improve the selectivity and yield of multiphase reactions, an attempt to intensify gas–liquid mass-transfer operations was undertaken in which screen/grid static mixers were used to promote interphase mass transfer. A modified technique was used to enhance the reproducibility of the results and to account for the depletion effect which becomes critical at high mass-transfer rates. The volumetric mass transfer coefficient, k L a, was found to increase with increasing liquid superficial velocity and gas volume fraction and reached values as high as 4.08 s–1 at low specific energy consumption rates, particularly for slowly coalescent systems, a situation that is encountered in most industrially relevant systems. The gas–liquid reactor/contactor presently investigated takes advantage of the coalescence retardation characteristics of most industrially relevant streams to achieve k L a values that surpassed those of most conventional reactor/contactors by more than an order of magnitude while maintaining a high energy utilization efficiency (up to 0.63 kg O2/kWh). The ability to reach 98% equilibrium within residence times of less than 800 ms, achieved without significantly increasing the power consumption rates, allows for the use of static mixing reactor volumes that are several orders of magnitude smaller than conventional units such as mechanically agitated tanks and bubble columns.

No abstract

No abstract

No abstract

Nine compounds have been isolated for the first time from Celtis africana, namely trans-N-coumaroyltyramine (1), trans-N-feruloyltyramine (2), trans-N-caffeoyltyramine (3), lauric acid (4), oleic acid (5), palmitic acid (6), lupeol (7), β-sitosterol (8) and oleanolic acid (9), respectively. Their structures have been elucidated by different spectroscopic techniques. The isolated compounds were screened for their antioxidant, anti-inflammatory and acetylcholinestrease enzyme inhibitory activities. Compounds 1-3 showed significant antioxidant and anti-inflammatory activities and weak to moderate acetylcholinestrease enzyme inhibition activity.