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A concise review of relevant experimental observations and modeling of high-pressure trickle-bed reactors, based on recent studies, is presented. The following topics are considered:  flow regime transitions, pressure drop, liquid holdup, gas−liquid interfacial area and mass-transfer coefficient, catalyst wetting efficiency, catalyst dilution with inert fines, and evaluation of trickle-bed models for liquid-limited and gas-limited reactions. The effects of high-pressure operation, which is of industrial relevance, on the physicochemical and fluid dynamic parameters are discussed. Empirical and theoretical models developed to account for the effect of high pressure on the various parameters and phenomena pertinent to the topics discussed are briefly described.

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in Wiley InterScience (www.interscience.wiley.com).The four-point optical probe is applied in a bubble column with an air-water system to investigate the bubble properties (local gas holdup, velocity, chord length, specific interfacial area, and frequency) over a range of gas superficial velocities. Both bubbles moving upward and downward are recorded and measured as opposed to only upward bubbles measured and reported in other studies involving probes. The probe worked efficiently in both bubbly flow and highly churn-turbulent flow at very high superficial gas velocities. Bubble properties at the conditions of churn-turbulent flow are obtained and investigated for the first time. The changes in the bubble velocity distribution, bubble chord length distribution, and specific interfacial area with superficial gas velocity, sparger design, and with axial and radial positions in the column are discussed.

Extrudates of Al-Fe pillared clay catalyst suitable for packed-bed operations are evaluated for wastewater treatment via a wet oxidation process employing hydrogen peroxide as the oxidant. The reaction was carried out in a semibatch basket reactor under rather mild conditions. Operational parameters were studied under the following conditions: temperature from 25 to 90°C, atmospheric pressure, initial phenol concentration from 100 to 2000 ppm of the liquid phase, catalyst loading from 0 to 10 g/L, and input H 2 O 2 concentration from 0.15 to 0.6 mol/L. Under these conditions, the Al-Fe pillared clay catalyst achieves a total elimination of phenol and significant total organic carbon (TOC) removal. This catalyst can be used several times without any change in its catalytic properties, and hence, it would be a promising catalyst for industrial wastewater treatment. The reaction takes place to a significant extent both in the liquid phase and on the catalyst surface. Hence, apparent kinetic models were developed by formulating the reaction rate in two kinetic expressions that separately consider the homogeneous and heterogeneous contributions. Using the second-order approach for the homogeneous reaction and the Langmuir-Hinshelwood approach for the heterogeneous reaction, the developed kinetic models describe well the removal of phenol and the formed intermediate carbon over the entire range of the variables studied.

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