Süheyda Atalay

Treatment of aniline by catalytic wet air oxidation: Comparative study over CuO/CeO2 and NiO/Al2O3

The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts.

Catalytic combustion of methylenechloride

The catalytic combustion of methylenechloride, one of the chloromethanes, was investigated on metal oxide catalysts coated on the monolith support or on the spherical alumina pellets, The prepared catalysts were tested at the different temperatures between 200 and 500°C and at varying GHSV values with an excess air of 216% The catalyst having the composition of 15% Cr2O3, 5% Ce2O3 and 80%γ-Al2O3 on the monolith was found to be ultimate due to the complete destruction of methylenechloride and to the highest mechanical stability. The operating conditions were proposed as 77778 h−1 for the GHSV, 216% for the excess air and 400–500°C for the temperature range to combust methylenechloride completely The dependency of the reaction on methylenechloride and oxygen partial pressures was searched, and it was determined that the rate was strongly dependent on oxygen partial pressure and weakly methylenechloride partial pressure. The reaction rate expression was derived using the mechanism proposed by Downie and the ...

Treatment of an Alkaloid Industry Wastewater by Biological Oxidation and/or Chemical Oxidation

The treatment of high strength alkaloid industy wastewater was carried out by biological and chemical oxidation and by the appropriate combinations of them. As a biological treatment, activated sludge, and as a chemical treatment, catalytic wet air oxidation (CWAO), processes were used. In biological process, the effects of retention time (4, 6, 8 days) and air flowrate (3, 4.5 L/min) were tested and 6 days of retention time, 4.5 L/min air flowrate were decided to be appropriate operating conditions. In CWAO process, effects of temperature (140, 150, 160°C) and catalyst loading (0.5, 1 g/L) were tested. The optimum temperature and catalyst loading were found to be 150°C and 1g/L, respectively. In combined processes, biologically treated wastewater was subjected to CWAO and also chemically oxidized wastewater was subjected to the biological treatment. Combinations of both processes seemed not so effective. Biological treatment alone was sufficient.

Catalytic combustion of carbon tetrachloride.

The catalytic combustion of carbon tetrachloride (CCl4) by metal oxide catalysts coated on the monolith support was investigated. The prepared catalysts were tested at temperatures between 300 and 800 degrees C and at varying gas hourly space velocity (GHSV) values with an excess air ratio of 3100%. The catalyst, whose composition was 18% Cr2O3, 2% Ce2O3 and 80% gamma-Al2O3, was found to almost completely oxidize CCl4. The operating conditions proposed are 5702 h(-1) for GHSV, 3100% excess air and a temperature slightly higher than 800 degrees C. The reaction rate expression was found to be independent of oxygen partial pressure but strongly dependent on CCl4 partial pressure.

Novel Catalysts in Advanced Oxidation of Organic Pollutants

This brief summarizes the role of certain catalysts and associated processes that are involved in the reduction or elimination of hazardous substances from wastewater and the exploitation of renewable raw materials. The authors begin by providing a summary of the most recent developments in catalysts used in the advanced oxidation of organic pollutants in aqueous phase. Advanced Oxidation Processes (AOPS) are described in terms of homogeneous and heterogeneous catalysts. Some emphasis is placed on the role nanocatalysts, perovskite-type catalysts, and green catalysts play in several AOPs such as Fenton Chemistry, photocatalytic oxidation, and the hybrid technologies that combine different processes. Catalyst preparation, characterization, reaction chemistry, and process technology are described. Specific wastewater case studies which illustrate the role of these catalysts in AOPs completes the brief

Comparative Study Using Chemical Wet Oxidation for Removal of Reactive Black 5 in the Presence of Activated Carbon

AbstractThe objective of this study was to assess the feasibility of various chemical wet oxidation techniques to remove azo dyes from wastewater. The performances of three different catalytic wet oxidation techniques were evaluated: catalytic wet air oxidation (CWAO), catalytic wet peroxide oxidation (CWPO), and hydrogen peroxide promoted wet air oxidation (PCWAO), using activated carbon as a catalyst to evaluate the degradation and decolorization of Reactive Black 5 in aqueous solution. The experiments were also conducted to investigate the optimum operating conditions of the processes, such as temperature, pH, activated carbon loading, H2O2 loading, and reaction time. This investigation revealed that all of the wet oxidation techniques showed similar results and rather high removal efficiencies, but at different operating conditions. At the optimized conditions, the degradation was generally approximately 85% and decolorization was nearly 95% in each case. The operating conditions were as follows: in t...

Photocatalytic and photo-Fenton-like degradation of methylparaben on monolith-supported perovskite-type catalysts

ABSTRACT Methylparaben was degraded in the presence of ABO3 perovskite catalysts (A: La, Bi, and B: Ti-Fe, Fe) synthesized on a monolithic structure using the sol–gel method. The catalysts were characterized by BET, SEM, XRD, and FTIR. The highest degradation was observed using BiFeO3 on the monolithic structure. The methylparaben degradation and iron leaching were 82.8% and 0.06 ppm, respectively, under the optimum conditions, which were pH=7, [H2O2]0=0.5 mM, and 0.1 g/L BiFeO3 loading. The toxicity tests were carried out by cress seeds and 1.09% inhibition was observed. Methylparaben degradation followed the second-order reaction kinetics, whereas the activation energy was 54 kJ/mol.

Advanced Oxidation Processes

Various organic pollutants are discharged into the aquatic environment. Most of them are not only toxic but also nonbiodegradable. Hence they cannot be treated by biological wastewater treatment plants or other conventional methods. And consequently a need arises to develop effective methods for the degradation of organic pollutants, either to less harmful compounds or to their complete mineralization. Advanced Oxidation Processes (AOPs) have attracted increasing attention due to their potential capability in the removal of recalcitrant organic pollutants. This chapter presents the general process principles on Advanced Oxidation Processes namely and discusses catalysis in Advanced Oxidation Processes. The usage and mechanism of both homogeneous and heterogeneous catalysts in Fenton Oxidation, Catalytic Wet Air Oxidation and Ozonation are discussed comprehensively.

Kinetic study of combustion of isopropanol and ethyl acetate on monolith-supported CeO2 catalyst

The complete catalytic combustion kinetics of isopropanol and ethyl acetate were investigated using a CeO2 catalyst coated on a monolith support. The combustions were carried out at low temperatures and atmospheric pressure, on a fixed-bed monolithic reactor. The Mars and van Krevelen model, power rate law model and Langmuir – Hinshelwood model were used to analyse the experimental results. The differential reactor assumption was used to fit the kinetic models. Due to the low activation energies of the reactions, both the Mars – Van Krevelen and power rate law models showed good agreement between the measured and calculated reaction rates, with the Mars – Van Krevelen model being slightly better.

Catalytic Oxidation of Methanol to Formaldehyde

Methanol is a clean burning fuel, containing no sulphur or nitrogenous materials. It produces power with very low emissions compared to those of a natural gas-fired, combined-cycle unit. Methanol can also be used as a feedstock for more sophisticated processes in the petrochemical industry. In this study, catalytic oxidation of methanol to formaldehyde was investigated. For this purpose, laboratory type, fixed bed catalytic reactor was used. For this gas-phase reaction iron-molybdate catalysts supported by silica or alumina were used. On silica and alumina supports, different Mo/Fe ratios were investigated for three different residence times (W/FA0) and six different temperatures were tried. The analysis of liquid product was performed by using gas chromatograph. From the results of GC analysis and CO2 analyzer, conversion of methanol to formaldehyde, total conversion and selectivity to formaldehyde were obtained. After the determination of optimum operating conditions for this reaction, kinetic study was performed.