Mass transfer‐limited wet oxidation of phenol

Abstract

Catalytic wet oxidation carried out in a continual three-phase trickle-bed reactor contributes to the sustainability of chemical technology. It was found that the hydrodynamics and the masstransfer of reactants could have a signi®cant impact on the performance of the trickle-bed reactor. An aqueous phenol oxidation was tested at different temperatures and liquid feed rates and the activities of both the CuO-supported catalyst and the extruded active carbon were compared. To avoid the impact of liquid maldistribution, a bed of catalyst particles diluted with ®ne glass spheres was also used. Ratelimited conditions of both liquid-and gas-phase presented reactants were determined. Under the conditions of gas component transfer limitation, a better wetting of the diluted catalyst bed can lead to a worsening in the reactor performance due to the lower overall reaction rates.

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

“…30 years later, the use of carbon as catalyst for environmental oxidation processes is starting to develop. Excluding the patent and scientific literature on AC regeneration via WAO, about 25 papers were published during the last 10 years on catalytic wet oxidation using carbons as direct catalyst [26][27][28][29]35,61,[79][80][81][82][160][161][162][163][164][165][166][167][168][169][170][171][172][173]. Strictly, half of these studies was devoted either to low temperature oxidation employing AC and H 2 O 2 or O 3 oxidants [166][167][168][169][170][171][172][173] or partial oxidation for fine chemical synthesis [80][81][82] rather than to CWAO.…”

“…Most research dealing with the wet oxidation of phenolic compounds [26][27][28][29]35,61,79,118,124,[160][161][162][163][164][165] only considered total carbon surface area, given by the manufacturer or measured by N 2 -adsorption isotherms. As indicated in table 8, the total surface area of activated carbons used ranged from 600 to 1400 m 2 /g, but no clear correlation of catalytic activity and surface area was observed.…”

“…The mode preferred in industry is the TBR [196] allowing for a variety of flow regimes depending on the gas and liquid flow rates employed. The same situation holds for CWAO, however only a few of the available studies attempted to experimentally assess the impact of gasliquid hydrodynamics and mass transfer on reactor performance under CWAO conditions [28,29,56,191,197]. Non-idealities in TBR operation during CWAO were detected by various researchers.…”

“…Examples of such new concepts are the simultaneous adsorption and oxidation [26][27][28][29] or sequential adsorption-oxidation [30] of pollutants as well as adsorptionregeneration cycles in the same reactor unit [31][32][33][34]. Better performance of a continuous trickle bed reactor (TBR) for the phenol CWAO was also achieved by applying forced periodic operation of liquid flow [35].…”

“…Recently, activated carbon was proved to render encouraging conversions in the oxidation of phenol [26][27][28][29][79][80][81][82]. ACs are versatile materials that entail not only excellent properties for numerous pollutant adsorption and catalyst support applications, but also catalytic activity for many reactions including hydrogenation, oxidation, halogenation, hydration isomerisation and polymerisation reactions [83][84][85].…”