Catalytic wet air oxidation of phenol using active carbon: performance of discontinuous and continuous reactors

Abstract

Catalytic wet air oxidation (CWAO) of an aqueous phenol solution using active carbon (AC) as catalytic material was compared for a slurry and trickle bed reactor. Semi-batchwise experiments were carried out in a slurry reactor in the absence of external and internal mass transfer. Trickle-bed runs were conducted under the same conditions of temperature and pressure. Experimental results from the slurry reactor study showed that the phenol removal rate signi®cantly increased with temperature and phenol concentration, whereas partial oxygen pressure had little effect. Thus, at conditions of 160°C and 0.71 MPa of oxygen partial pressure, almost complete phenol elimination was achieved within 2 h for an initial phenol concentration of 2.5 g dm À3

Catalytic Wet Air Oxidation of Aqueous Organic Mixtures

“…Large particles of AC are used to minimize fast and continuous deactivation as reported previously during phenol oxidation when using powder (Stüber et al, 2001). A steep decrease of activity is however observed between the first two oxidation runs, but afterwards the time-concentration profiles in the liquid phase are found to be stable for a large number of further runs, as verified with final ones at standard conditions (p T =20 bar, T=150°C).…”

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.…”

“…Such catalyst fouling was detected during CWAO of phenol over Ceria, CuO/ZnO and activated carbon (AC) [61][62][63][64]. Theses studies showed that the ability of catalysts to form carbonaceous deposits strongly depends on the reactor type used.…”

“…Theses studies showed that the ability of catalysts to form carbonaceous deposits strongly depends on the reactor type used. Slurry reactors with a characteristic high liquid to catalyst ratio exhibited enhanced homogeneous side reactions and thereby the build-up of such deposits [62,64] while these side-reactions were significantly reduced in TBRs [61,65,66]. During the last years considerable research efforts were focused on reducing unwanted catalyst deactivation.…”