Direct NO decomposition over La2−xBaxNiO4 catalysts containing BaCO3 phase

Catalytic and in situ Fourier Transform Infrared (FTIR) spectroscopic studies were conducted to investigate the adsorption and oxidation of o- and p-chlorophenol over a 3.6 wt.% V₂O₅/TiO₂ catalyst. At a space velocity of approximately 53,000 cm³ g⁻¹ h⁻¹, this catalyst was found to be active for the oxidation of o- and p-chlorophenol at temperatures as low as 200 °C, yielding CO₂ and HCl as the main products. Trace amounts of higher molecular weight products were also detected at the reactor outlet indicating the operation of additional condensation, coupling and chlorination/dechlorination side reactions in parallel to the main complete oxidation scheme. The in situ FTIR studies revealed that different phenols adsorb on the V₂O₅/TiO₂ catalyst through their hydroxyl group. Furthermore, the formation of similar surface species (i.e., maleates, acetates, formates and an aldehyde-type species) was observed. The results were compared with those of previous studies on the oxidation of m-dichlorobenzene (m-DCB) and benzene and suggest that a similar reaction mechanism is operating in all cases, although the relative kinetic significance of the different steps varies with the presence and the position of the hydroxyl and chlorine groups on the aromatic ring.     

V2O5 catalysts supported on Al2O3–SiO2 mixed oxide: V, H MAS solid-state NMR, DRIFTS and methanol oxidation studies

Alumina–silica mixed oxide, synthesized by the sol–gel technique, was used as a support for dispersing and stabilizing the active vanadia phase. The catalysts were characterized employing ⁵¹V and ¹H solid-state MAS NMR, diffuse reflectance FT-IR, BET surface area measurements. The partial oxidation activities of the catalysts were tested using methanol oxidation as a model reaction. ⁵¹V solid-state NMR studies on the calcined catalysts showed the peaks corresponding to the presence of both tetrahedral and distorted octahedral vanadia species at low vanadia loadings and with an increase in V₂O₅ content, the ⁵¹V chemical shifts corresponding to amorphous V₂O₅ like phases were observed. DRIFTS studies of the catalysts indicated the vibrations corresponding tetrahedral vanadia species at low and medium loadings and at high V₂O₅ contents the vibrations corresponding V=O bonds of V₂O₅ agglomerates were observed. The V/Al–Si catalysts exhibited high selectivity for the dehydration product dimethyl ether in the methanol partial oxidation studies showing the predominance of the acidic nature of the alumina–silica support over the redox properties of the active vanadia phase.     

Polarisation enhanced C magnetic resonance studies of the hydrogenation of pentene over Pd/Al2O3 catalysts

This paper reports the first demonstration of ¹³C distortionless enhancement by polarisation transfer (DEPT) NMR spectroscopy at natural abundance to study the hydrogenation and isomerisation of pentenes over a 1 wt% Pd/Al₂O₃ catalyst. Single component C5 hydrocarbons and binary mixtures of hydrocarbon and hydrogen have been adsorbed on both a pure alumina support and the Pd/Al₂O₃ catalyst derived from it. The pentene species studied were 1-, cis-2- and trans-2-pentene. No isomerisation or hydrogenation was observed when single component pentene isomers or binary mixtures of 1-pentene and hydrogen, and cis-2-pentene and hydrogen were adsorbed onto the pure alumina support. However, when trans-2-pentene and hydrogen were both adsorbed onto the support, partial hydrogenation to n-pentane was observed in addition to the presence of both cis-2- and trans-2-pentenes. All pentene isomers hydrogenate over the Pd/Al₂O₃ catalyst to give predominantly n-pentane and a small amount of the trans-2-pentene isomer. For the parameters chosen here these studies show that trans-2-pentene appears to be the active isomer for hydrogenation over the pure support alone.     

Deactivation patterns of Mo/Al2O3, Ni–Mo/Al2O3 and Ni–MoP/Al2O3 catalysts in atmospheric residue hydrodesulphurization

In the present work, a comparative study on the deactivation behavior of three types of industrial hydrotreating catalysts, namely, Mo/Al₂O₃, Ni–Mo/Al₂O₃ and Ni–MoP/Al₂O₃, that are used to promote primarily hydrodemetallization (HDM), hydrodesulphurization (HDS) and hydrodesulphurization + hydrodenitrogenation (HDS/HDN) reactions, respectively, in the first, second and third reactor of commercial atmospheric residue desulfurization (ARDS) units was carried out. The main objective of the study was to contribute to a better understanding of the relationship between catalyst type and catalyst deactivation patterns. The used catalysts from these experiments were fully characterized to determine the extent and the cause of deactivation. Special emphasis was paid to understanding the nature of the coke and metal deposition on the used catalysts by applying chemical analysis and various advanced analytical techniques, such as solid-state carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR), temperature-programmed oxidation (TPO), electron probe micro-analysis (EPMA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The results are discussed scientifically based on the physico–chemical properties of the three catalysts.     

CoBr2-MnBr2 containing catalysts for catalytic oxidation of p-xylene to terephthalic acid

Catalytic oxidation of p-xylene (PX) to terephthalic acid (TA) was studied with catalysts containing cobalt acetate, manganese acetate, CoBr₂ and MnBr₂. The catalysts contain neither highly corrosive hydrogen bromide nor other metal ions, and have the advantage of easy catalyst recovery. The effects of Br/Co atomic ratio, reaction time and temperature, PX concentration, oxygen pressure, and catalyst concentration on PX conversion and product/intermediate yields were investigated. The catalyst system had a suitable reaction temperature of 100 °C, which was much lower than the commercial process temperature (175–225 °C). The maximum product (TA) yield was 93.5%, obtained at a Br/Co atomic ratio of three. Higher Br concentration resulted in the lower TA yield, which was ascribed to the benzylic bromide formation. The synthesis of TA could be adequately described as four reaction steps in series (PX → p-tolualdehyde → p-toluic acid → 4-carboxybenzaldehyde → TA), with a pseudo-first-order rate equation for each step, and the third step was rate-limiting. The rate constant ratios (k_j/k₃, j = 1 → 4) obtained at 100 °C were similar to the k_j/k₃ values reported earlier for cobalt acetate/manganese acetate/HBr catalysts in a range of 185–191 °C.     

Exchange and oxidation of CO on O-predosed Rh---Al2O3 and Rh---CeO2 catalysts

Exchange and oxidation of C¹⁶O were investigated at 450°C on ¹⁸O-predosed Rh and Pt catalysts supported on A1₂O₃, CeO₂ and CeO₂-Al₂O₃. In all cases, a rapid exchange of C¹⁶O with the surface can be observed. CO oxidation leads to C¹⁶O₂, C¹⁶O¹⁸O and C¹⁸O₂. Significant formation of C¹⁶O₂ is due to the relatively high ¹⁶O coverage in reaction resulting from the C¹⁶O exchange and from an exchange between O surface species and ¹⁶O internal atoms. Hydrogen is also formed via a water-gas shift reaction (CO + surface OH) in higher proportion on CeO₂-containing catalysts than on A1₂O₃. Chlorine inhibits all the reactions (exchange, oxidation and WGS) and particularly the internal exchange.     

Iodosulfuron degradation by TiO2 photocatalysis: Kinetic and reactional pathway investigations

The photocatalytic degradation of a sulfonylurea herbicide, iodosulfuron methyl ester (IOME), has been studied in TiO₂ aqueous suspensions under UV irradiation. The influence of various parameters such as initial concentration, TiO₂ concentration and light intensity on the kinetic process was investigated. Disappearance rate of iodosulfuron followed pseudo-first order kinetics. A special attention was devoted to the identification of intermediates, using a new analytical approach which consists of coupling HPLC–DAD (UV), HPLC–ESI-MS and HPLC–¹H NMR techniques after a SPE pre-concentration step. By combining UV, MS and NMR data, up to 20 degradation products were unambiguously identified. Furthermore, ¹H NMR data allowed the differentiation of several positional isomers, in particular those of hydroxylation resulting from the attack of OH radicals on the benzene ring of IOME. Kinetic evolution profiles of main intermediates, end products (NO₃⁻, NH₄⁺, SO₄²⁻) and total organic carbon (TOC) were also examined in detail. From obtained kinetic and analytical results, the presence of privileged sites for the attack of OH radicals was shown and a detailed degradation pathway was proposed.     

Catalytic oxidation of naphthalene using a Pt/Al2O3 catalyst

Polycylic aromatic hydrocarbons (PAHs) are listed as carcinogenic and mutagenic priority pollutants, belonging to the environmental endocrine disrupters. Most PAHs in the environment stem from the atmospheric deposition and diesel emission. Consequently, the elimination of PAHs in the off-gases is one of the priority and emerging challenges. Catalytic oxidation has been widely used in the destruction of organic compounds due to its high efficiency (or conversion of reactants), its economic benefits and good applicability.

This study investigates the application of the catalytic oxidation using Pt/γ-Al₂O₃ catalysts to decompose PAHs and taking naphthalene (the simplest and least toxic PAH) as a target compound. It studies the relationships between conversion, operating parameters and relevant factors such as treatment temperatures, catalyst sizes and space velocities. Also, a related reaction kinetic expression is proposed to provide a simplified expression of the relevant kinetic parameters.

The results indicate that the Pt/γ-Al₂O₃ catalyst used accelerates the reaction rate of the decomposition of naphthalene and decreases the reaction temperature. A high conversion (over 95%) can be achieved at a moderate reaction temperature of 480 K and space velocity below 35,000 h⁻¹. Non-catalytic (thermal) oxidation achieves the same conversion at a temperature beyond 1000 K. The results also indicate that Rideal–Eley mechanism and Arrhenius equation can be reasonably applied to describe the data by using the pseudo-first-order reaction kinetic equation with activation energy of 149.97 kJ/mol and frequency factor equal to 3.26 × 10¹⁷ s⁻¹.     

Water-induced bulk Ba(NO3)2 formation from NO2 exposed thermally aged BaO/Al2O3

Phase changes in high temperature treated (>900 °C) 8 or 20 wt% BaO supported on γ-Al₂O₃ model lean NO_x trap (LNT) catalysts, induced by NO₂ and/or H₂O adsorption, were investigated with powder X-ray diffraction (XRD), solid state ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and NO₂ temperature programmed desorption (TPD) experiments. After calcination in dry air at 1000 °C, the XRD and solid state ²⁷Al MAS NMR results confirm that stable surface BaO and bulk BaAl₂O₄ phases are formed for 8 and 20 wt% BaO/Al₂O₃, respectively. Following NO₂ adsorption over these thermally treated samples, some evidence for nanosized Ba(NO₃)₂ particles are observed in the XRD results, although this may represent a minority phase. However, when water was added to the thermally aged samples after NO₂ exposure, the formation of bulk crystalline Ba(NO₃)₂ particles was observed in both samples. Solid state ²⁷Al MAS NMR is shown to be a good technique for identifying the various Al species present in the materials during the processes studied here. NO₂ TPD results demonstrate a significant loss of uptake for the 20 wt% model catalysts upon thermal treatment. However, the described phase transformations upon subsequent water treatment gave rise to the partial recovery of NO_x uptake, demonstrating that such a water treatment of thermally aged catalysts can provide a potential method to regenerate LNT materials.     

The selective catalytic oxidation of NH3 over Fe-ZSM-5

The abatement of NH₃ from waste streams has become an important environmental issue. Selective catalytic oxidation (SCO) of NH₃ to N₂ has emerged as a potential technology for taking care of NH₃ slips and NH₃ in waste streams. In this work, we describe the catalytic activity of Fe-zeolite catalysts prepared by incipient wetness technique, ion exchange and hydrothermal synthesis in the SCO of NH₃ to N₂ using a fixed bed flow reactor. Selective catalytic oxidation was carried out at 573–723 K and 10⁵ Pa with gas hourly space velocities (GHSV) between 24 000 and 240 000 h⁻¹. Results obtained showed that Fe-ZSM-5 catalysts prepared by incipient wetness technique were active for NH₃ conversion (77–100%) and selectivity to N₂ (65–100%). Fe-ASA and Fe-Beta showed good catalytic activity and selectivity, but their activity and selectivity were less than that of Fe-ZSM-5. The effects of water vapour, Fe loading, and activation method on the performance of these catalysts was also investigated.     

Kinetics of propylene epoxidation using H2 and O2 over a gold/mesoporous titanosilicate catalyst

The oxidation of propylene to propylene oxide (PO) with hydrogen–oxygen mixtures was studied on gold supported on the mesoporous titanium silicate, Ti-TUD. The catalyst gave stable activity at low conversions of propylene (<6%) and high selectivity to PO (>95%). Kinetic data were fit to a power-rate law and gave the following expression: r_PO = k(H₂)^0.54(O₂)^0.24(C₃H₆)^0.36. The fractional orders in hydrogen, oxygen, and propylene indicated that these reactants interacted with the catalyst to form species that led to the final PO product. The catalyst likely operated by the commonly accepted mechanism of hydrogen peroxide production on gold sites, and epoxidation on titanium centers. Carbon dioxide was formed primarily from further oxidation of PO rather than the oxidation of propylene, while water was produced from the reaction of hydrogen and oxygen.     

A study of the abatement of VOC over V2O5–WO3–TiO2 and alternative SCR catalysts

The conversion of C3 organic compounds (propane, propene, 1- and 2-propanol, allyl alcohol, propanal, acrolein, acetone and 1- and 2-chloropropane) in the presence of excess oxygen has been investigated over two V–W–TiO₂ commercial SCR catalysts differing in the V content and over Mn–TiO₂ alternative SCR catalysts. V–W–Ti catalysts show poor activity in the oxidation of hydrocarbons and oxygenates and give significant amounts of partial oxidation products. Moreover they give rise to CO in excess of CO₂. The sample higher in V is more active. Mn–TiO₂ is definitely more active in oxidation of hydrocarbons and oxygenates, and produces, at total conversion, CO₂ as the only detectable product.

V–W–Ti catalysts are very active in dehydrochlorination of the two 2-chloropropane isomers and retain the same oxidation activity also in the presence of HCl. On the contrary, Mn-based catalysts in the presence of chlorocarbons convert into dehydrochlorination catalysts but lose their catalytic activity in oxidation. V–W–Ti catalysts can be used in Cl-containing atmospheres while Mn–TiO₂ can be proposed for DeNO_x and VOC abatement in Cl-free atmospheres such as for diesel engine exhaust gas purification.     

Thermal behaviour, redox properties, and catalytic performance of alkali-promoted V2O5 catalysts in the selective oxidation of p-methoxytoluene: a comparative study

Alkali-promoted V₂O₅ catalysts M–V₂O₅ (M=Li, K, Cs) were synthesised by impregnation of V₂O₅ with alkali sulphate solution. Pure V₂O₅ was used for comparison. X-ray diffraction, spectroscopic (FTIR), and thermoanalytical methods (STA/MS) have been used to characterise the phase composition, the adsorption properties, and the reducibility of the catalysts. The catalytic performance was proved using the oxidation of p-methoxytoluene (PMT) to p-methoxybenzaldehyde (PMBA) as test reaction. The surface acidity is lowered, but the reducibility is enhanced with increasing size and basic properties of the alkali cation. This leads to an increased adduct (PMT) adsorption and decreased product (PMBA) adsorption in the order V₂O₅2O₅K–V₂O₅2O₅. Consequently, the catalytic performance is improved in the same way. The formation of bronze phases at relative low temperatures in the case of K– and Cs–V₂O₅ stabilise V⁴⁺ oxidation state and improve the redox properties and consequently the catalytic results. The admixture of the non-reactive pyridine enhances the aldehyde selectivity by further lowering of the surface acidity. Additionally, pyridinium cations generated during catalytic reaction and incorporated into the formed alkali bronze phases stabilise these structures.     

Degradation of olive oil mill effluents by catalytic wet air oxidation: 2-Oxidation of p-hydroxyphenylacetic and p-hydroxybenzoic acids over Pt and Ru supported catalysts

Catalytic wet air oxidation of p-hydroxyphenylacetic acid and p-hydroxybenzoic acid, two important pollutants present in the olive oil mill wastewaters, was studied in a batch reactor using platinum and ruthenium catalysts supported on titanium and zirconium oxides at 140 °C and 50 bar of total air pressure. Reaction pathways for the oxidation of these two substrates were proposed, with formation of different aromatic compounds and short-chain organic acids through hydroxylation and decarboxylation reactions.

It was observed that the conversion and the mineralization of these two substrates were markedly affected by the nature of the ruthenium precursor (RuCl₃ or Ru(NO)(NO₃)₃), with the non-chlorine containing salt giving the best performances. Calcination of the catalyst precursor before reduction was detrimental. The nature of the metallic precursor (H₂PtCl₆ or Pt(NH₃)₄(NO₃)₂) had little influence on the catalytic properties of platinum catalysts, whereas the textural properties of the support were an important factor.     

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

Co₃O₄/CeO₂ composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co₃O₄) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co₃O₄ and CeO₂ were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out.

An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co₃O₄ in correspondence of Co₃O₄–CeO₂ containing 30% by weight of Co₃O₄. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co₃O₄ phase and promoting the efficiency of the Co³⁺–Co²⁺ redox couple. The presence in the sample Co₃O₄(30 wt.%)–CeO₂ of a high relative amount of Ce³⁺/(Ce⁴⁺ + Ce³⁺) as detected by XPS confirms the enhanced oxygen mobility.

The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co₃O₄ phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co₃O₄ and Co₃O₄(30 wt.%)–CeO₂, performing the tests in the presence of 5 vol.% H₂O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H₂O + 5 vol.%O₂ in He) of the Co₃O₄(30 wt.%)–CeO₂ sample was also performed. All the results confirm the superiority of this composite oxide.     

Deactivation studies over NiO/γ-Al2O3 catalysts for partial oxidation of methane to syngas

Two types of NiO/γ-Al₂O₃ catalysts prepared by the impregnation and the sol–gel method were used for the partial oxidation of methane to syngas at 850°C (GHSV1.8×10⁵ lkg⁻¹ h⁻¹). The effects of the carbon deposition, the loss and sintering of nickel and the phase transformation of γ-Al₂O₃ support on the catalytic performance during 80 h POM reaction were investigated with a series of characterization such as XRD, BET, AAS, TG, and XPS. The results indicated that the carbon deposition and the loss and sintering of nickel could not cause the serious decrease of catalytic performance over NiO/γ-Al₂O₃ catalyst during the short-time reaction. However, the slow process of the support γ-Al₂O₃ phase transforming into -Al₂O₃ could slowly decrease the performance of NiO/γ-Al₂O₃ catalysts. Aimed at the reasons of the deactivation, an improved catalyst was obtained by the complexing agent-assisted sol–gel method.     

Synthesis and crystal structure of carbonate cancrinite Na8[AlSiO4]6CO3(H2O)3.4, grown under low-temperature hydrothermal conditions

The synthesis of cancrinite in the system Na₂O–SiO₂–Al₂O₃–Na₂CO₃–H₂O was studied under low-temperature hydrothermal conditions in the 353 K<T<473 K interval. The aim was to reveal the suitable range for the crystallization of pure-phase carbonate cancrinite with the ideal composition Na₈[AlSiO₄]₆CO₃(H₂O)₂ without cocrystallization of sodalite or intermediate disordered phases between cancrinite and sodalite. It was found that cancrinite formation reacts very sensitive on the temperature within the autoclaves whereas the concentration of reactants and the alkalinity of the hydrothermal solution have a much lower influence on the phase formation. Thus the temperature of crystallization of carbonate cancrinite without any by-products should not remain below 473 K. At the lower reaction temperature of 353 K the formation of a disordered intermediate phase between the cancrinite and the sodalite structure has been obtained in every case, independent of the template concentrations and the base. Some problems to detect this in a typical powder product mixture are discussed. Besides the ²⁹Si and ²⁷Al MAS NMR characterization of the products, the crystal structure refinement of pure carbonate cancrinite of ideal composition Na₈[AlSiO₄]₆CO₃(H₂O)_3.4, has been carried out from X-ray powder data using the Rietveld method: P6₃, a=1271.3(1) pm, c=518.6(1) pm, R_WP=0.073, R_F=0.016 for 347 structure factors and 45 variable positional parameters.     

Zeolite synthesis in the presence of flexible diquaternary alkylammonium ions (C2H5)3N(CH2)nN(C2H5)3 with n=3–10 as structure-directing agents

The use of flexible diquaternary alkylammonium ions (C₂H₅)₃N⁺(CH₂)_nN⁺(C₂H₅)₃ (Et₆-diquat-n with n=3–10) as structure-directing agents for zeolite synthesis in the presence of alkali metal cation is described. Among the organic structure-directing agents studied here, a considerable diversity in the phase selectivity was observed only for the Et₆-diquat-5 ion: this cation can produce five different zeolite structures (i.e., P1, SSZ-16, SUZ-4, ZSM-57, and mordenite), depending on the oxide composition of synthesis mixtures. Analysis of the variable-temperature ¹H CRAMPS NMR spectra obtained from the Et₆-diquat-5 molecules in these five zeolites reveals that the host–guest interactions occurring within the respective materials maintain in a manner different from one another even at 160 °C at which the zeolite hosts crystallize.     

The role of acidity in the decomposition of 1,2-dichlorobenzene over TiO2-based V2O5/WO3 catalysts

The influence of Lewis and Brønsted acid sites on the performance of V₂O₅/TiO₂ and V₂O₅–WO₃/TiO₂ catalysts in the total oxidation of o-dichlorobenzene was investigated. Catalytic activity of these materials resulted strongly affected by their acidic properties. The presence of Brønsted acid sites significantly increases the o-DCB conversion but also leads to the uncompleted degradation of chlorinated compounds, promoting the formation of partial oxidation products, as dichloromaleic anhydride. On the contrary, Lewis acid sites, acting as absorbing sites, promote the further oxidation of intermediates to CO and CO₂, without any by-products desorption.

Furthermore, the presence of water in the feed-stream was proven to decrease o-DCB conversion but also to play a positive role on process selectivity, increasing COx production. Plausible reasons for this effect are the reduction of Brønsted acid sites and the hydrolysis of anhydride during wet tests.     

Electrocatalytic oxidation of p-nitrophenol from aqueous solutions at Pb/PbO2 anodes

In this work, the elimination of p-nitrophenol (p-NPh) from aqueous solutions by electrochemical oxidation at Pb/PbO₂ anodes was investigated. The process was studied under galvanostatic polarization mode in acidic and alkaline media, as a function of the temperature (20, 40 and 60 °C) and of the anodic current density (J = 10, 20 and 30 mA cm⁻²). In acidic media (0.5 M H₂SO₄), the oxidation process allowed a 94% p-NPh conversion in 7 h, at 20 °C and with J = 20 mA cm⁻², with a wide distribution of degradation products (in particular: 39% p-benzoquinone and 26% hydroquinone, as given by a mass balance at the above electrolysis time). Under these conditions, the current efficiency for the substrate oxidation was 15.4% ([Ah L⁻¹]_exp = 7 versus [Ah L⁻¹]_theo = 1.08 Ah L⁻¹). In alkaline media (0.1 M NaOH, pH 8.5), the most effective p-NPh elimination (97%) was obtained at 60 °C, 20 mA cm⁻² and 420 min of electrolysis time, again with the production of p-benzoquinone and hydroquinone (52.7 and 15.1%, respectively). Under the latter conditions, an almost complete chemical oxygen demand (COD) abatement was attained, with a high level of p-NPh mineralization (>80%), a yield of p-NPh conversion greater than 95% and a scarce formation of aliphatic acids (most probably maleic acid). From the degradation curves ([p-NPh] versus t), in both acidic and alkaline media, the UV analyses and/or COD measurements, a complete oxidation of aliphatic acids to form CO₂ could be predicted for electrolysis time >420 min, according to a suggested oxidation pathway.