Activity For Decomposition Of Hydrogen Peroxide Research Articles

Carbon Quantum Dots/Cu2O Photocatalyst for Room Temperature Selective Oxidation of Benzyl Alcohol.

The luminescence properties and excellent carrier transfer ability of carbon quantum dots (CQDs) have attracted much attention in the field of photocatalysis. In this work, we loaded the CQDs on the surface of Cu2O to enhance the visible-light property of Cu2O. Furthermore, the composite was used for selective oxidation of benzyl alcohol to benzaldehyde. The composite catalyst achieved high selectivity (90%) for benzaldehyde at room temperature, leveraging its visible-light-induced electron transfer properties and its photocatalytic activity for hydrogen peroxide decomposition. ·OH was shown to be the main reactive oxygen species in the selective oxidation reaction of benzyl alcohol. The formation of heterostructures of CQDs/Cu2O promoted charge carrier separation and provided a fast channel for photoinduced electron transfer. This novel material exhibited enhanced levels of activity and stability for selective oxidation of benzyl alcohol. Potential applications of carbon quantum dot composites in conventional alcohol oxidation reactions are shown.

Metal ion‐mediated immobilization of catalase on poly(ε‐caprolactone)/polyethyleneimine electrospun nanofibers

AbstractA common industrial byproduct known as hydrogen peroxide, which is an essential intermediate, is associated with oxidative damage to brain cells and a number of neurodegenerative disorders. Although catalases are enzymes capable of decomposing hydrogen peroxide into water and oxygen, the low stability of free enzymes limits their industrial use. In the current study, poly(ε‐caprolactone)/polyethyleneimine nanofibers were fabricated using the electrospinning process and catalase was subsequently immobilized via coordination of Cu2+ ions. The characterization of the catalase‐immobilized nanofibers and their catalytic activity for hydrogen peroxide decomposition was evaluated by comparing the free catalase. The studies conducted in the pH range of 5.0–8.5 revealed that the catalase‐immobilized nanofibers had their highest levels of enzyme activity at pH 7.0. When compared to free catalase, it was shown that the thermal stability and storage stability of catalase‐immobilized nanofibers were significantly improved. Catalase‐immobilized nanofibers showed significant reusability, where activity was maintained by around 60% after five repeating cycles. The findings showed that catalase‐immobilized PCL/PEI‐Cu2+ nanofibers had a high potential for various industrial applications as a substitute for the existing techniques.

Colorimetric Determination of Mercury(II) by Secondary Gold Nanoparticles Formation on Primary Gold Nanoparticles as an Efficient Nanozyme

Gold nanoparticles (Au-NPs) shows promise enzyme-like activity for hydrogen peroxide decomposition and produced free electrons for metal ion reduction. Thus, we focused on the design and construction of primary Au-NPs (p-Au-NPs) for decomposition hydrogen peroxide and subsequently reduction of Au3+ to form secondary Au-NPs (s-Au-NPs). Since mercury(II) as soft metal ion can make amalgam with the Au-NPs this can be applied as a boosting idea for indirect detection of mercury(II). Therefore, s-Au-NPs preparation in presence of different concentrations of mercury(II) on surface of p-Au-NPs that cause a color change by final oxidation of 3,4-diaminotoluene while s-Au-NPs/p-Au-NPs cannot oxidize 3,4-diaminotoluene marker and no color change is achieved become as a goal. This occurrence causes a colorimetric procedure, from mauve to dark wine, which facilitates determination of mercury(II) ions in a reasonable range from 2.15 to 25.12 µM with a UV–Vis spectrometer. Sensor characterized by analysis such as UV–Vis, DLS, SEM, EDS, XRD and FT-IR. At last, accuracy of the model investigated with recovery process and observed that method could be advantageously applied as a simple method for the determination of mercury (II) in real samples have been developed to monitor the water quality by tracing different amount of analyte ions in samples. The different water sample such as lake water, tap water, and any water with the necessity of checking the quality of it to help the environment for places with the lack of high-tech technology.

A Stochastic Characterization of Hydrogen Peroxide-Induced Regulated Cell Death in Microcystis aeruginosa.

Regulated cell death (RCD) encompasses the activation of cellular pathways that initiate and execute a self-dismissal process. RCD occur over a range of stressors doses that overcome pro-survival cellular pathways, while higher doses cause excessive damage leading to passive accidental cell death (ACD). Hydrogen peroxide (HP) has been proposed as a potential tool to control harmful cyanobacterial blooms, given its capacity to remove cyanobacterial cells and oxidize cyanotoxins. HP is a source of hydroxyl radicals and is expected to induce RCD only within a limited range of concentrations. This property makes this compound very useful to better understand stress-driven RCD. In this work, we analyzed cell death in microcystin-producing Microcystis aeruginosa by means of a stochastic dose response model using a wide range of HP concentrations (0, 0.29, 1.76, 3.67, 7.35, 14.70, and 29.5 mM). We used flow cytometry and unsupervised classification to study cell viability and characterize transitional cell death phenotypes after exposing cells to HP for 48 and 72 h. Non-linear regression was used to fit experimental data to a logistic cumulative distribution function (cdf) and calculate the half maximal effective concentration (EC50). The EC50 of M. aeruginosa exposed to HP were 3.77 ± 0.26 mM and 4.26 ± 0.22 mM at 48 and 72 h, respectively. The derivative of cdf (probability density function; pdf) provided theoretical and practical demonstration that EC50 is the minimal dose required to cause RCD in 50% of cells, therefore maximizing the probability of RCD occurrence. 1.76 mM HP lead to an antioxidant stress response characterized by increased reactive oxygen species (ROS) levels and HP decomposition activity. The exposure of 3.67 mM HP induced a dose-related transition in cell death phenotype, and produced several morphological changes (a less dense stroma, distortion of the cell membrane, partial disintegration of thylakoids, extensive cytoplasmic vacuolation and highly condensed chromatin). The EC50 and the stochastic cdf and pdf together with the multidimensional transitional phenotypic analysis of single cells contribute to further characterize cell death pathways in cyanobacteria.

Au (Core)–Pt (Shell) Nanocatalysts with the Shell Thickness Controlled at a Monolayer Level: Extremely High Activity for Hydrogen Peroxide Decomposition

Au and Pt nanoparticle-loaded anatase TiO2 particles (Au/TiO2 and Pt/TiO2) were separately prepared by the deposition–precipitation method. Also, selective Pt photodeposition on the Au surface of Au/TiO2 yielded Au (core)–Pt (shell) bimetallic NP-loaded TiO2 particles. In Au (core)–Pt (shell)/TiO2, the mean Pt-shell thickness was controlled at an atomic layer level by irradiation time. The thermocatalytic activities of Au/TiO2, Pt/TiO2, and Au (core)–Pt (shell)/TiO2 for the decomposition of H2O2 were evaluated in the dark at 25 °C. Au (core)–Pt (shell)/TiO2 exhibits a much higher activity than that of Au/TiO2 and even Pt/TiO2 in spite of that Pt has the highest activity among the metals. The turnover frequency depends on the mean number of Pt layers, reaching a maximum of 1.1 × 106 around the monolayer. Density functional theory simulations were performed to analyze the potential-energy surfaces in metal-cluster-catalyzed H2O2 decomposition with Au50, Pt50, and Au14 (core)–Pt36 (shell) used as model metal...

Fabrication, characterization and catalytic activity measurements of nano-crystalline Ag-Cr-O catalysts

This research paper describes the preparation, characterization and the hydrogen peroxide decomposition activity of a series of nano-crystalline Ag-Cr-O catalysts obtained by calcining a parent mixture of silver acetate and ammonium dichromate. This parent has been calcined for 1 h, in air, at the temperature range of 200–700 °C. The characterization of the nano-crystalline Ag-Cr-O catalysts was performed using a series of physico-chemical analyses including TGA-DTA, XRD, FTIR, SEM, TEM, and XPS. The results revealed that heat treatment brought about a significant-phase formation, Ag2Cr2O7 is formed at 200 °C and a mixture of Ag2CrO4 and Cr2O3 are formed over the calcination temperature range of 300–500 °C. AgCrO2 stats to form at 500 °C and becomes a major phase at the range 600–700 °C with a noticeable segregation of metallic silver. The activity of the different nano-crystalline Ag-Cr-O catalysts was tested for hydrogen peroxide decomposition at the temperature range 35–50 °C. The kinetic data showed a direct dependence on the calcination temperature and it was correlated with the formed surface redox-couples.

Understanding Hydrogen Peroxide Decomposition Activity of Transition Metal Oxide Catalysts in Oxygen Reduction Reaction

Energy storage is essential for large-scale integration of renewable energy such as solar and wind into the electricity grid. Fuel cells and metal-air batteries are promising technologies for grid-scale energy storage owing to their high energy densities and environmental friendliness. However, it is well known that the slow kinetics of the oxygen reduction reaction (ORR) at the cathode limits the efficiency of these fuel cells and metal-air batteries. Among transition metal oxides, calcium-doped lanthanum cobalt oxide is one of the promising catalysts for ORR because of the ability of these materials to support both oxygen evolution and oxygen reduction reactions [1]. In previous work, we demonstrated that in transition metal oxide–carbon composites catalysts, carbon is the primary electrocatalyst for the two electron electro-reduction of oxygen to hydrogen peroxide and the transition metal oxide decomposes the hydroperoxide to generate additional oxygen [2]. Therefore, we have focused on understanding the role of mixed metal oxides on decomposition of hydrogen peroxide for designing more active carbon-based catalyst systems. Specifically, we have studied the effect of manganese substitution of cobalt in calcium-doped lanthanum cobalt oxide on the hydrogen decomposition rate of the catalysts. Manganese-substituted compounds of the formula La0.6Ca0.4Co1-xMnxO3 compound with x value = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1 were synthesized by the sol-gel method using the Pechini process. As previously described [3], a two-step heat treatment was employed for the synthesis of these compounds. In the first step the material subjected to controlled combustion at 120-170 oC, then the material was collected, ground and heat-treated in a second step sintering process at 700oC for 2 hours. The decomposition characteristics of hydrogen peroxide on various transition metal oxides was measured by oxygen reduction studies on rotating-ring-disk (coated glassy carbon) electrode, and by steady state polarization studies of the oxidation and reduction of hydrogen peroxide. We have demonstrated that the mixed potential of the oxide electrode under open circuit conditions could be predicted from the kinetics of the conjugate reactions of peroxide oxidation and reduction. We also find that the higher rate of oxidation of hydroperoxide correlated directly with the improved oxygen reduction activity in the composite catalyst. The presentation will discuss these findings. Figure 1

Using a Hands-On Hydrogen Peroxide Decomposition Activity To Teach Catalysis Concepts to K–12 Students

A versatile and transportable laboratory apparatus was developed for middle and high school (6th–12th grade) students as part of a hands-on outreach activity to estimate catalytic rates of hydrogen peroxide decomposition from oxygen evolution rates measured by using a volumetric displacement method. The apparatus was constructed with inherent safety features and is compatible with different types of catalysts, catalyst and peroxide concentrations, and reaction temperatures to enable the design of various experiments. The hands-on outreach activity was created with the aim of building scientific proficiency and stimulating interest in STEM fields among students with limited chemistry background. This activity is designed to be completed in short times (45 min) by students in small groups (3–5 students), where each group measures reaction rates at various activity stations and then gathers as a larger group (∼20 total) to discuss their observations and results and to assess their scientific understanding. A...

In-vitro Anthelmintic and Antioxidant Activity of Helicteres isora Linn. Fruit Extracts

In-vitro anthelmintic activity of methanol and petroleum ether extracts of Helicteres isora fruits were determined by the evaluation of time for paralysis and death (min.) against Indian earthworms Pheretima posthuma. Various concentrations of extracts were tested in the bioassay (10, 20, and 50 mg/ml). Albendazole at concentration 20 mg/ml was included as standard reference while normal saline (0.9 % NaCl) solution as control. Antioxidant activity was determined by 2, 2-diphenyl-1-picryl hydrazyl (DPPH) and Hydrogen peroxide (H2O2) radicals scavenging assays. The both methanol and petroleum ether extracts showed dose dependent anthelmintic activity. The DPPH free radical scavenging activity was obtained with the methanol extract (IC50 42.95 µg/ml), while petroleum ether extract showed less free radical scavenging activity (IC50 89.81 μg/ml) as compared to standard ascorbic acid (IC50 23.75 µg/ml). Hydrogen peroxide decomposition activity of methanol and petroleum ether extracts were showed in a concentration dependent manner with an IC50 36.61 µg/ml and 74.40 µg/ml respectively, while IC50 value for ascorbic acid was 9.64 ìg/ml. Methanol extracts showed potent anthelmintic and antioxidant activity than petroleum ether extracts.

Chemical surface modified‐activated carbon cloth for catalytic wet peroxide oxidation of phenol

AbstractBACKGROUNDActivated carbons (AC) can be used as catalyst in advanced oxidation processes due to the potential activity for hydrogen peroxide decomposition to hydroxyl radicals. Chemical surface groups and textural properties can play a crucial role in its catalytic behaviour. The pH of the reaction medium can also affect the adsorption properties of AC and the chemistry of hydrogen peroxide in catalytic oxidation processes. The AC/H2O2 systems have been successfully used for the degradation of some organic pollutants in wastewaters over recent years.RESULTSThe influence of different modified‐activated carbon cloth (ACC) samples has been studied. Commercial ACC samples were treated under neutral (H2O), acid (H3PO4), basic (NaOH) and oxidizing (H2O2) solutions. Modified‐ACC samples were assessed in the adsorption (in absence of H2O2) and chemical advanced oxidation (in presence of H2O2) of phenol at different pH values. ACC samples hydrothermally treated showed the best adsorption properties. ACC samples treated with NaOH solutions evidenced the best catalytic performance for phenol oxidation under acidic conditions.CONCLUSIONSThe functionalization of ACC samples with basic surface groups yielded the best catalytic performance with total phenol removal and efficient use of the hydrogen peroxide at acidic conditions. © 2014 Society of Chemical Industry

A silica-silver nanocomposite obtained by sol-gel method in the presence of silver nanoparticles

Abstract Silver nanoparticles (AgNPs) were obtained by a redox reaction, using a glucose-containing cyclosiloxane as a reduction agent and stabilizer. Then the AgNPs aqueous solution was used as the reaction medium for the sol-gel process, starting from tetraethylorthosilicate (TEOS) as silica precursor. The nanocomposite material resulted (SilAg) after solvent removal, aging and calcination and was investigated by infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy coupled with energy dispersive X-ray system (SEM/EDX), transmission electron microscopy (TEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and dynamic vapor sorption (DVS). The results were compared to model silicas obtained without silver. A higher condensation degree in SilAg was obtained due to the basic medium used in the first step and was confirmed by a sorption capacity lower than for the model silicas. The solid surface area calculated with GAB analysis using DVS data for the water vapors is 210 m2 g−1. The nanocomposite showed good catalytic activity for hydrogen peroxide decomposition.

The use of cyclic voltammetry to assess the activity of carbon materials for hydrogen peroxide decomposition

It is known that carbon materials catalyze hydrogen peroxide decomposition in aqueous media. However, the catalytic activity of a particular carbon is dependent on various coupled structural, textural and chemical characteristics of the material, such that, formerly, the prediction of activity has not been possible. Here, the application of cyclic voltammetry (CV) is introduced as a rapid and conclusive technique in this respect. Three classes of carbon materials have been investigated: activated carbons, carbon blacks, and graphites, including some selected acid-washed samples which were used to examine the roles of mineral matter and surface oxygen. Characterization by electrochemical capacity measurements with CV, together with catalytic activity tests for hydrogen peroxide decomposition, reveal that the exchange current is directly proportional to the catalytic activity for hydrogen peroxide decomposition. That is, a linear dependence was found between this variable and the apparent first order catalytic decomposition rate constant. CV measurements with modified carbons also allow the elucidation of the effects of physicochemical characteristics of carbon materials on the rate of hydrogen peroxide decomposition.

A fully microfabricated carbon nanotube three-electrode system on glass substrate for miniaturized electrochemical biosensors

We present an integration process to fabricate single-walled carbon nanotube (SWCNT) three-electrode systems on glass substrate for electrochemical biosensors. Key issues involve optimization of the SWCNT working electrode to achieve high sensitivity, developing an optimal Ag/AgCl reference electrode with good stability, and process development to integrate these electrodes. Multiple spray coatings of the SWCNT film on glass substrate enabled easier integration of the SWCNT film into an electrochemical three-electrode system. O₂ plasma etching and subsequent activation of spray-coated SWCNT films were needed to pattern and functionalize the SWCNT working electrode films without serious damage to the SWCNTs, and to remove organic residues. The microfabricated three-electrode systems were characterized by microscopic and spectroscopic techniques, and the electrochemical properties were investigated using cyclic voltammetry and chrono-amperometry. The fully-integrated CNT three-electrode system showed an effective working electrode area about three times larger than its geometric surface area and an improved electrochemical activity for hydrogen peroxide decomposition. Finally, the effectiveness of miniaturized pf-SWCNT electrodes as biointerfaces was examined by applying them to immunosensors to detect Legionella(L) pneumophila, based on a direct sandwich enzyme-linked immunosorbent assay (ELISA) format with 3,3',5,5'-tetramethylbenzidine dihydrochloride/hydrogen peroxide(TMB/H₂O₂) as the substrate/mediator system. The lower detection limit of the pf-SWCNT-based immunosensors to L. pneumophila is about 1500 times lower than that of the standard ELISA assay.

The in Vivo Toxicity of Hydroxyurea Depends on Its Direct Target Catalase

Hydroxyurea (HU) is a well tolerated ribonucleotide reductase inhibitor effective in HIV, sickle cell disease, and blood cancer therapy. Despite a positive initial response, however, most treated cancers eventually progress due to development of HU resistance. Although RNR properties influence HU resistance in cell lines, the mechanisms underlying cancer HU resistance in vivo remain unclear. To address this issue, we screened for HU resistance in the plant Arabidopsis thaliana and identified seventeen unique catalase mutants, thereby establishing that HU toxicity depends on catalase in vivo. We further demonstrated that catalase is a direct HU target by showing that HU acts as a competitive inhibitor of catalase-mediated hydrogen peroxide decomposition. Considering also that catalase can accelerate HU decomposition in vitro and that co-treatment with another catalase inhibitor alleviates HU effects in vivo, our findings suggests that HU could act as a catalase-activated pro-drug. Clinically, we found high catalase activity in circulating cells from untreated chronic myeloid leukemia, offering a possible explanation for the efficacy of HU against this malignancy.

Color inhibition of phenolic antioxidants in Ziegler‐Natta polyethylene. I. In‐situ polymer studies

AbstractAlthough the level of transition‐metal catalyst residues in polyethylene (PE) has been drastically reduced over the years, they can still give rise to discoloration, particularly when associated with other additives such as antioxidants. This first of this series of papers screens a variety of candidate color suppressants featuring a range of functional groups, including alcohols, amine/sulfur compounds, and acid‐containing species. These candidate color suppressants were melt‐blended into a Ziegler‐Natta linear low‐density PE in combination with 2,2′‐isobutylidenebis(4,6‐dimethylphenol) (a highly discoloring hindered bisphenol antioxidant) and zinc stearate antacid. Yellowness index measurements made after multiple extruder passes indicated that dipentaerythritol (DPE) and triisopropylamine (TIPA) gave good color inhibition and, in some cases, outperformed established phosphites. The DPE and TIPA were found (via melt flow rate measurement) not to affect melt stability, and hydroperoxide determination revealed that DPE had no peroxide decomposition activity. The latter results indicate that the color‐suppression mechanism of DPE and TIPA is different from that associated with phosphites. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers

Oxygen evolution over Ag/FexAl2−xO3 (0.0≤x≤2.0) catalysts via N2O and H2O2 decomposition

Abstract In this paper, a comparative study between nitrous oxide and hydrogen peroxide decomposition over a series of catalysts prepared via the combustion of silver, aluminum, and iron nitrates (with different aluminum: iron ratios). Urea was used as a combustion fuel. The calcinations were affected at the 400–700 °C temperature range. The produced catalysts were characterized by using XRD and SEM analyses. The obtained results revealed that silver metal supported on Al 2 O 3 and/or Fe 2 O 3 represent the major constituents of all the calcinations products, i.e. Ag/Fe x Al 2− x O 3 . However, two different interfaces are involved in the two test reactions, all the catalysts were able to decompose both reactants yielding oxygen as a joint product. Meanwhile, it was found nitrous oxide destruction activity increases with decreasing both silver particles size and iron content in the catalysts substrate. On the contrary, increasing iron content in the different catalyst was found to enhance hydrogen peroxide decomposition activity. Moreover, a synergic effect was observed for the catalysts having Al:Fe ratio of 0.5:1.5.

Antioxidant potential of Anogeissus latifolia.

Anogeissus latifolia is widely used in the Indian indigenous system of medicine and is reported to contain leucocyanidins and tannoid principles like ellagic acid and its derivatives. In view of its wide use and its chemical composition, this study was aimed at examining the antioxidant activity of the extract of A. latifolia. The extract was studied for total antioxidant capacity, hydrogen-donating ability, nitric oxide, superoxide scavenging activity, hydrogen peroxide decomposition activity along with lipid peroxidation. Integral antioxidative capacity was determined by chemiluminescence assay. The extract was also studied for lipid peroxidation assay by thiobarbituric acid-reactive substances (TBARS) method using rat liver homogenate. The results indicate that A. latifolia extract has potent antioxidant activity. Also to ascertain the possible reason for the potent activity, percentage of gallic acid was estimated and was found to be 0.95%, which could be one of the reasons for potent antioxidant activity exhibited by the plant.

The Effect of Calcium Doping on the Surface and Catalytic Properties of Cobaltic Oxide Catalysts

The effects of calcium oxide doping (0.75, 1.5 and 3 mol% CaO) and calcination temperature (400, 500, 600 and 700°C) on different surface properties of Co3O4 were investigated. The structural properties of pure and doped oxide samples were determined by XRD methods, the textural properties were investigated via the adsorption of nitrogen at −196°C while the hydrogen peroxide decomposition activity of the investigated solids was determined by oxygen gasometric measurement of the reaction kinetics at 20–40°C. The dissolution of calcium ions in the Co3O4 lattice at temperatures in the range 400–600°C was accompanied by a marked decrease in the mean hydraulic radii (rh) and an increase in the surface area (SBET) and total pore volume (Vp) of the prepared oxide samples. In contrast, doping at 700°C brought about a decrease in the SBET and Vp values of the investigated solids. The catalytic activity for H2O2 decomposition on cobaltic oxide calcined at 400–700°C was found to decrease considerably on doping with CaO. The activation energy for sintering (ΔEs) of the pure and doped solids was determined from the variation in their SBET values as a function of the calcination temperature of these solids. Calcium oxide treatment resulted in a 50% increase in the activation energy of sintering of cobaltic oxide solid calcined at 400–600°C. This increase reflects the role of CaO doping in hindering the sintering of cobaltic oxide.

Catalytic decomposition of H 2O 2 on promoted cobaltic oxide catalysts

Pure and ZnO-doped cobaltic oxide catalyst were prepared by thermal decomposition in air at 400–700 °C of pure basic cobalt carbonate and that treated with different amounts of zinc nitrate (0.46–2.25 w% ZnO). X-ray powder diffractometry and BET analysis of nitrogen adsorption isotherms investigated the crystalline bulk structure and the surface area of pure and doped samples, respectively. The hydrogen peroxide decomposition activity was determined by oxygen gasometry of the reaction kinetics at 20–40 °C. The results revealed that the treatment of Co 3O 4 with ZnO at 400–700 °C brought about a significant increase in the specific surface area of cobaltic oxide. However, the catalytic activity of H 2O 2 decompositon on cobaltic oxide calcined at different temperatures was found to show a considerable increase by doping with ZnO. In addition, the catalytic decomposition of H 2O 2 on ZnO-doped cobaltic oxide catalysts required much lower activation energies as compared to that necessary for the reaction on the pure catalysts. The calculated activation energies for the catalytic reaction over both the pure and ZnO-treated catalysts reflected the role of ZnO treatment in modifying the concentration of catalytically active constituents. In other words, the doping process increased the concentration of Co 3+–Co 2+ ion pairs and created Co 3+–Zn 2+ ion pairs increasing thus the number of the active constituents involved in the catalytic decomposition of H 2O 2.

The influence of lithium on the hydrogen peroxide decomposition activity of manganese–alumina catalysts

Addition of small quantities of Li 2O to Al 2O 3 was studied with respect to its influence on the catalytic decomposition of H 2O 2 over Mn/Al mixed oxide catalysts calcined at 400, 700 and 1000 °C for 6 h. The specific surface areas of pure and doped solids were determined by BET analysis of nitrogen adsorption isotherms. The catalytic activities and the values of S BET of pure and doped mixed oxides were found to decrease by increasing the amount of Li 2O present. The activation energy of sintering, Δ E, of various solids decreased considerably by increasing the amount of Li 2O added. The maximum decrease in Δ E due to the doping with 6 mol% Li 2O attained 50%. In other words, Li 2O doping facilitates the sinterability of the treated solids to an extent proportional to the amount of lithia present. This treatment did not modify the activation energy of the catalyzed reaction, i.e. doping of Mn/Al mixed oxides did not alter the mechanism of the catalytic reaction but changed the concentration of catalytically active sites taking part in the catalytic process without altering their energetic nature.