In this work oxidation of phenol with hydrogen peroxide on Cu/ZSM-5 catalysts was studied. The catalysts samples were prepared by two different methods: by ionic exchange from the protonic form of ...commercial ZSM-5 zeolite, and by direct hydrothermal synthesis. Characterization of the catalysts extends to X-ray diffraction (XRD), while the adsorption techniques were used for the measurement of the specific surface area.
The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and the temperature range from 50 to 80
°C. The mass ratio of the active metal component on the zeolite was in the range of 1.62–3.24
wt.%. for catalyst prepared by direct hydrothermal synthesis and 2.23–3.52
wt.% for catalyst prepared by ion exchange method. The initial concentration of phenol and hydrogen peroxide was 0.01 and 0.1
mol
dm
−3, respectively. The influence of different methods of Cu/ZSM-5 preparation on their catalytic performance was monitored in terms of phenol conversion and degree of metal leached into aqueous solution.
The aim of the present work is to study the heterogeneous wet hydrogen peroxide catalytic oxidation (WHPCO) of phenol using copper bearing Silicalite-1 type zeolite, prepared by direct hydrothermal ...synthesis. The catalysts used for this study were three: one (Na)Cu-Silicalite-1 and two (H)Cu-Silicalite-1 prepared by different ion exchange methods. The results on catalytic activity for phenol abatement and hydrogen peroxide consumption of these materials are presented. The copper leaching during the reaction was evaluated for all samples. A comparison with the catalytic activity and stability of a Cu-Silicalite-1 material prepared by ionic exchange method is presented.
Katalitička oksidacija zagađivala organskog podrijetla vodikovim peroksidom u vodenom mediju, poznata kao metoda CWPO (eng. Catalytic Wet Peroxide Oxidation), jedan je od postupaka kojim je moguće ...postići smanjenje organskog opterećenja otpadnih voda u praksi. U ovom radu zeolit Y-5 izabran je za nosač u koji je kao katalitički aktivna tvar ugrađen bakar. U radu je istražen utjecaj reakcijskih parametara te postsintetske kemijske i termičke obrade katalizatora na njegove katalitičke značajke: aktivnost i stabilnost. Katalizator Cu/Y-5 pripravljen je ionskom izmjenom protoniranog oblika komercijalnog zeolita Y-5. Radi poboljšanja njegovih katalitičkih značajki provođena je postsintetska kemijska (ispiranje sa H2SO4) i termička obrada (kalciniranje). Karakterizacija katalizatora Cu/Y-5 obuhvaćala je rengdensku difrakcijsku analizu na praškastom uzorku (PXRD) i elementnu analizu na atomskom apsorpcijskom spektrometru (AAS) te određivanje specifične površine, obujma pora i raspodjele obujma pora (standardna metoda BET). Aktivnost i stabilnost pripravljenih katalizatora ispitana je u reakciji oksidacije fenola vodikovim peroksidom u vodenoj otopini. Maseni udjel bakra na zeolitu bio je 3,46 % prije postsintetske obrade, odnosno 3,97 % nakon postsintetske termičke obrade te 0,94 % nakon postsintetske kemijske obrade. Eksperimentalni podatci dobiveni provođenjem katalitičkih testova testirani su sljedećim kinetičkim modelima za oksidaciju fenola rPh = k1 cPh cHP i raspad vodikova peroksida rHP = k2 cHP. Za procjenu kinetičkih parametara primijenjena je Nelder-Meadova metoda nelinearnog optimiranja. Oba postupka postsintetske obrade značajno su poboljšala stabilnost pripravljenog Cu/Y-5 katalizatora, dok je istodobno njegova aktivnost ostala nepromijenjena ili je poboljšana.
Olive oil mill wastewater (OOMW) – the liquid waste generated in the process of olive oil extraction contains significant amounts of phenolics. Their high polluting charges that are measured in BOD5 ...and COD levels up to 35 g dm-3 and the presence in the concentrations up to 10 g dm-3 are of special concern to the environment. These compounds make OOMW biorefractory in nature and unsusceptible to a conventional biological treatment. Reducing their toxicity prior to the conventional treatment is therefore of the uttermost importance. The non-selective catalytic wet peroxide oxidation (CWPO) process is one of the methods that can be used for that purpose in practice. With the use of catalysis the process can be successfully operated under mild conditions with low energy consumption. In this work, the influence of the reaction parameters and the catalyst preparation method on the activity and stability of zeolite (13X) based catalyst in the reaction of hydrogen peroxide oxidation of phenolic compounds present in wastewater from industry for processing olives and olive oil was examined. The reaction was carried out in a batch reactor at different stirring speed, particle sizes, temperatures, catalyst loadings and initial concentrations of hydrogen peroxide. The catalyst Cu/13X was prepared by ion exchange of commercial 13X zeolite. Characterization of the catalyst included N2 physisorption, XRD, TPD-CO2 and FTIR-Pyridine desorption. In order to increase the catalyst’s stability, it was subjected to a thermal post-synthesis treatment at 1273 K. The justification for post synthesis treatment of the catalyst is reflected in the enhanced stability of the catalytically active material which is removed from the carrier, i.e. larger resistance of Cu/13X - K1273 to leaching. Examining the effect of the mixing rates and catalyst particle sizes on reaction rate it was found that the reaction is carried out in the kinetic regime, with the total phenols content diminished by more than 80 % with a 20 % decrease in wastewater’s TOC content and leaching below 3 wt. %.
Microporous, mesoporous and new hybrid materials were studied in verbenol oxide isomerization for the synthesis of biologically active substance with anti-Parkinson activity. H-Si-MCM-41, ...H-Al-MCM-41, H-Al-MCM-48, H-Beta-25 and H-Beta-300 were compared with hybrid materials. The latter with a zeolite-like micro-mesoporous structure were characterized and evaluated for their catalytic activity for the first time. The approach of dual templating for synthesis of new materials was applied in this work to combine properties of Beta-zeolites and mesoporous cellular foams. The selectivity to the target product was the highest over microporous mild acidic H-Beta-300 and hybrid ZF-100, with also mild acidity and even absence of strong acid sites. Selectivity at 97% and 99% of conversion was 61% and 59% for H-Beta-300 and hybrid ZF-100, respectively.
This work reports the results of experimental and theoretical investigation of toluene oxidation on different metal oxide based catalysts (manganese oxide, MnOx, mixed manganese-iron oxide, MnFe, ...perovskite-type manganese oxide, LaMnO3 and commercial Pt-Al2O3 catalyst). Particular attention was devoted to single and mixed manganese based oxides and ceria based materials as alternatives to conventionally used noble metal containing catalysts. Toluene oxidation was performed under steady-state conditions in an integral fixed bed reactor operating over a wider range of reaction temperatures and at various space times. The influence of reaction variables on the rate of toluene oxidation was examined using the simple first-order kinetic model and the one-dimensional (1D) pseudo-homogeneous model to describe the reaction system. The proposed model was verified comparing the theoretical predictions with the experimental laboratory results. The results of catalytic tests indicated that the mixed manganese-iron oxide (MnFe) exhibited remarkable catalytic activity for the toluene oxidation, almost comparable with the activity of the commercial Pt-Al2O3. The reaction temperature T50 corresponding to 50% of the toluene conversion was observed at 419 K for the MnFe oxide and at 405 K for the Pt-Al2O3. A very good agreement of experimental data with the proposed 1D model was obtained. Based on the shape of the light-off curve and the values of the apparent activation energies, which decreased from 120.36 kJ/mol to 16.88 kJ/mol with reaction temperature increase, it was concluded that the reaction rate was probably limited by the mass transfer, no matter the relatively small catalyst particle size fraction employed in this study (315 - 400µm).
The heterogeneous catalytic wet peroxide oxidation (CWPO), involving total oxidation of organic compounds to CO2 and H2O is a possible path for the treatment of toxic and bio‐refractory wastewater ...streams. The aim of this work was to synthesize and characterize three Cu/ZSM5 catalysts prepared by direct hydrothermal synthesis. The mass ratio of the active metal component in the zeolite ranged from 1.62–3.24 wt %. These materials were tested for CWPO of aqueous phenol in a stainless steel Parr reactor, in batch operation under mild conditions (at atmospheric pressure and a temperature of 353 K). The catalyst weight was 0.1 g dm–3 and the initial concentration of phenol and hydrogen peroxide were 0.01 mol dm–3 and 0.1 mol dm–3, respectively. The catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), AAS and ICP‐MS. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversion, hydrogen peroxide decomposition, by‐product distribution and the degree of copper leached into the aqueous solution. The experimental results indicated that within 180 min, these catalysts facilitated almost complete elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Cu ions from the zeolite. The Cu/ZSM5‐DHS3 catalyst with the highest copper loading was proven to be the best candidate. The useful fraction of hydrogen peroxide that contributed to the removal of the organic compounds quantified in terms of selectivity, S, indicated that the CWPO selectivity was always less than 100 %, which meant that there was some self‐degradation of oxidant. It was also shown that oxidation of phenol took place on the catalyst surface via a heterogeneous mechanism, and that the contribution of any homogeneous reaction mechanism was not significant.
Cu/ZSM5 zeolites with varying Si/Cu ratios are prepared by direct hydrothermal synthesis and tested for phenol oxidation with hydrogen peroxide at atmospheric pressure and 353 K. The best suitable catalyst shows the highest copper load. It is demonstrated that the oxidation of phenol takes place on the catalyst surface via a heterogeneous mechanism.
The necessity to remove organic pollutants from the industrial wastewater streams has forced the development of new technologies that can produce better results in terms of pollutant removal and ...process efficiency in combination with low investment and operating costs. One of the new emerging processes with a potential to fulfil these demands is catalytic wet peroxide oxidation, commonly known as the CWPO process. The oxidative effect of the hydrogen peroxide is intensified by the addition of a heterogeneous catalyst that can reduce the operating conditions to atmospheric pressure and temperatures below 383 K. Zeolites, among others, are especially appealing as catalysts for selective oxidation processes due to their unique characteristics such as shape selectivity, thermal and chemical stability, and benign effect on nature and the living world. In this work, catalytic activity, selectivity and stability of Cu/Y-5 zeolite in phenol oxidation with hydrogen peroxide was examined. Catalyst samples were prepared by ion exchange method of the protonic form of commercial zeolite. The catalysts were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and AAS elemental analysis, while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and in the temperature range from 323 to 353 K. The catalyst was prepared in powdered form and the mass fraction of the active metal component on the zeolite was 3.46 %. The initial concentration of phenol solution was equal to 0.01 mol dm−3 and the concentration of hydrogen peroxide ranged from 0.01 to 0.10 mol dm−3. The obtained experimental data was tested to a proposed kinetic model for phenol oxidation r = k1 cF cVP and hydrogen peroxide decomposition rHP = k2 cHP. The kinetic parameters were estimated using the Nelder-Mead method of nonlinear regression. On the basis of the obtained results of characterization process and conducted catalytic tests, the following can be observed. Zeolite structure of the prepared catalyst was confirmed through powder X-ray diffraction, scanning electron microscopy and adsorption techniques. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions, hydrogen peroxide decomposition, by-product distribution and degree of copper leached into the aqueous solution. The obtained experimental results indicate that in the space of 180 minutes, the use of these catalysts allows almost total elimination of phenol and significant removal of total organic carbon content with the use of small amounts of catalyst (0.1 g dm–3) and substoichiometric level (71.4 %) of oxidant required for complete oxidation of organic pollutant. The main product among aromatics was catechol, followed by hydroquinone and benzoquinone, which exhibited the typical pattern for a series reaction scheme. The distribution of carboxylic acids was as follows: maleic, fumaric, acetic and oxalic acids. These low-molecular carboxylic acids and aromatic compounds were responsible for the TOC that remained after almost complete removal of phenol. Moreover, one of the most interesting options was to use CWPO as a pre-treatment prior to biological treatment, for simple organic acids that are highly biodegradable. During the reactions, destabilization of the catalyst was observed in terms of leaching of copper from zeolite into the reaction mixture, but the previous investigations of similar catalytic systems showed that the activity of the solid catalyst was not due to the homogeneous contribution of the copper leached from the catalyst, but was more likely due to the activity of the heterogeneous catalyst. Further investigations on the mechanism of catalyst destabilization and methods of stabilization are the subject of the following article in the series. The proposed kinetic model adequately fits the experimental data. The rate of phenol oxidation and hydrogen peroxide decomposition increases with the increase in reaction temperature and decrease in initial concentration of hydrogen peroxide. The rate of phenol oxidation is first order toward the concentration of phenol and first order toward the concentration of H2O2. The rate of H2O2 decomposition is first order toward the concentration of H2O2. Activation energy in phenol oxidation was 86.0 kJ mol−1 for phenol oxidation, and 107.6 kJ mol−1 for hydrogen peroxide decomposition, which is in accordance with previously published results.
In the present work, a Cu-13X zeolite sample was ceramized and used as a catalyst for the wet oxidation of phenol solutions and olive oil mill wastewaters (OOMW). The material showed good catalytic ...activity for the abatement of phenol and poly-phenols, excellent stability and no leaching of the active species. In this way a real heterogeneously catalyzed reaction was performed. Moreover, the catalyst was reused without special reactivation treatments for different consecutive reaction cycles.
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