Peroxide Molar Ratio Research Articles

Optimization of the reaction parameters of epoxidation of rapeseed oil with peracetic acid

AbstractBACKGROUND: The epoxidation of vegetable oils has been a subject of interest for many years; epoxidized oils are frequently used as plasticizers and as renewable materials for the manufacture of alcohols, glycols and many other complex compounds with excellent antioxidant and antifriction properties. In this work the epoxidation process of rapeseed oil (RO) with peracetic acid generated in situ by the reaction of 30 wt% hydrogen peroxide and acetic acid has been studied. Optimization studies were performed by application of a statistical experimental design method utilizing a rotatable‐uniform design.RESULTS: The significant parameters for the RO epoxidation process were established as temperature, molar ratio of hydrogen peroxide to rapeseed oil, molar ratio of acetic acid to rapeseed oil and reaction time. The process description was based on five response functions: iodine number, epoxy number, conversion, yield and selectivity. The highest values of all functions with the exception of selectivity were achieved for the same values of parameters: temperature 65 °C, molar ratio of hydrogen peroxide to RO 11.1:1 mol mol−1, molar ratio of acetic acid to RO 1.89:1 mol mol−1 and reaction time 6 h.CONCLUSION: In summary, these optimum parameters allow one to obtain epoxidized rapeseed oil with a yield of 66.2 mol% at an oil conversion of 91.0 mol% in mild and relatively safe conditions. The epoxy number of the product was 0.207 mol per 100 g, whereas the iodine number was 0.027 mol per 100 g. Copyright © 2010 Society of Chemical Industry

Removal of residual contaminants in petroleum-contaminated soil by Fenton-like oxidation

The degradation of bioremediation residues by hydrogen peroxide in petroleum-contaminated soil was investigated at circumneutral pH using a Fenton-like reagent (ferric ion chelated with EDTA). Batch tests were done on 20 g soil suspended in 60 mL aqueous solution containing hydrogen peroxide and Fe 3+–EDTA complex under constant stirring. A slurry reactor was used to treat the soil based on the optimal reactant conditions. Contaminants were characterized by Fourier transform infrared spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry. The results showed that the optimal treatment condition was: the molar ratio of hydrogen peroxide to iron = 200:1, and pH 7.0. Under the optimum condition, total dichloromethane-extractable organics were reduced from 14,800 to 2300 mg kg −1 soil when the accumulative H 2O 2 dosage was 2.45 mol kg −1 soil during the reactor treatment. Abundance of viable cells was lower in incubated Fenton-like treated soil than in untreated soil. Oxidation of contaminants produced remarkable compositional and structural modifications. A fused ring compound, identified as C 34H 38N 1, was found to exhibit the greatest resistance to oxidation.

The Influence of Reaction Parameters on the Epoxidation of Rapeseed Oil with Peracetic Acid

AbstractThe influence of reaction parameters on the epoxidation of rapeseed oil (RO) with peracetic acid obtained in situ from the reaction between 30 wt% hydrogen peroxide and glacial acetic acid (AA) has been studied. The course of the reaction was measured by changes of the iodine number (IN) and epoxy number (EN), used to estimate the degree of rapeseed oil conversion, yield, and the selectivity of transformation to epoxidized rapeseed oil in relation to the total amount of oil undergoing the transformation. The optimal conditions of epoxidation are as follows: temperature 60 °C, molar ratio of hydrogen peroxide to rapeseed oil 9.5:1 mol/mol, molar ratio of acetic acid to rapeseed oil 1.12:1 mol/mol, stirring speed 500 rpm, and reaction time of 4 h. Under these conditions the epoxy number is equal to 0.157 mol/100 g RO and iodine number reaches low values of 0.123 mol/100 g RO. The selectivity of transformation to epoxidized RO calculated from EN and IN is 82.2%, conversion of hydrogen peroxide is 100%, conversion of RO calculated from IN is 60.8%, and yield of RO calculated from EN is 50%.

Production and Characterization of Epoxidized Canola Oil

Epoxidized canola oil may be well suited to the partial replacement of petroleum products in composite matrices; however, a process is needed to obtain this material from canola oil at sufficient conversion and scale to assess product properties. Therefore, canola oil was epoxidized in a solvent-free process with a heterogeneous catalyst; a fractional factorial design was used to determine the impact of processing conditions and their two-factor interactions on epoxy group content of epoxidized canola oil. The studied parameters were: molar ratio of acetic acid to unsaturation, molar ratio of hydrogen peroxide to unsaturation, concentration of hydrogen peroxide, concentration of catalyst, and temperature. Epoxidized canola oil with up to 98.5% conversion was produced. The parameters molar ratio of acetic acid to unsaturation, concentration of hydrogen peroxide, temperature, and their interactions were found to be significant in the defined design space. Process conditions that achieved the highest conversion were scaled to 300 g to compare the conversion, production yield, and rheological and melting properties of products of the epoxidation of both canola and soybean oil with and without solvent. Epoxidized canola oil crystallized at room temperature; at 40°C it was shear-thinning with an apparent viscosity of 140 to 150 mPa·s. Elimination of solvent in the epoxidation process decreased the yield 10% but did not reduce the conversion to epoxy groups. Therefore, the scaled-up, solvent-free process is proposed as a green alternative for sufficient epoxidized canola oil to test composite applications.

Synthesis of polymer‐supported metal‐ion complexes and evaluation of their catalytic activities

AbstractPolymer‐supported transition‐metal‐ion complexes of the N,N′‐bis(o‐hydroxy acetophenone) propylenediamine (HPPn) Schiff base were prepared by the complexation of iron(III), cobalt(II), and nickel(II) ions on a polymer‐anchored N,N′‐bis(5‐amino‐o‐hydroxy acetophenone) propylenediamine Schiff base. The complexation of iron(III), cobalt(II), and nickel(II) ions on the polymer‐anchored HPPn Schiff base was 83.44, 82.92, and 89.58 wt%, respectively, whereas the unsupported HPPn Schiff base showed 82.29, 81.18, and 87.29 wt % complexation of these metal ions. The iron(III) ion complexes of the HPPn Schiff base showed octahedral geometry, whereas the cobalt(II) and nickel(II) ion complexes were square planar in shape, as suggested by spectral and magnetic measurements. The thermal stability of the HPPn Schiff base increased with the complexation of metal ions, as evidenced by thermogravimetric analysis. The HPPn Schiff base showed a weight loss of 51.0 wt % at 500°C, but its iron(III), cobalt(II), and nickel(II) ion complexes showed weight losses of 27.0, 35.0, and 44.7 wt % at the same temperature. The catalytic activity of the unsupported and supported metal‐ion complexes was analyzed by the study of the oxidation of phenol and epoxidation of cyclohexene in the presence of hydrogen peroxide. The supported HPPn Schiff base complexes of iron(III) ions showed a 73.0 wt % maximum conversion of phenol and 90.6 wt % epoxidation of cyclohexene, but unsupported complexes of iron(III) ions showed 63.8 wt % conversion of phenol and 83.2 wt % epoxidation of cyclohexene. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 93.1 wt % and 98.1 wt % with the supported HPPn Schiff base complexes of iron(III) ions, but it was low with the supported Schiff base complexes of cobalt(II) and nickel(II) ions. The selectivity for CTL and ECH varied with the molar ratio of the metal ions but remained unaffected by the molar ratio of hydrogen peroxide to the substrate. The energy of activation for the epoxidation of cyclohexene and oxidation of phenol with the polymer‐supported Schiff base complexes of iron(III) ions was 10.0 and 12.7 kJ/mol, respectively, but it was found to be higher with the supported HPPn Schiff base complexes of cobalt(II) and nickel(II) ions and with the unsupported HPPn Schiff base complexes of iron(III), cobalt(II), and nickel(II) ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Catalytic wet peroxide oxidation of phenol from industrial wastewater on activated carbon

A heterogeneous catalyst obtained from copper adsorption by an ionic exchange resin, followed by carbonization, is presented as a promising option for phenol abatement in industrial wastewater. The catalyst was characterized before and after the catalytic tests by SEM-EDS. The performance of the catalyst in industrial wastewater, with 60 mg L −1 phenol, was compared with a model stream (1000 mg L −1 phenol). Successive reactions were also carried out in order to study the catalyst deactivation. The reaction was performed at 38 °C, 1 atm, pH 6.5, using a phenol to hydrogen peroxide molar ratio of 14. The catalyst was able to remove all phenol compounds present in both streams. The catalyst did not show any deactivation in the industrial stream, but deactivated in the model stream, a fact that can be assigned to the copper leaching, as inferred by SEM-EDS. In the model stream, the high phenol concentration caused a high production of organic acids, generated by parallel reactions, which led to copper leaching. The industrial stream did not show deactivation since the amount of these acids was too low to leach copper.

Polymer Supported Schiff Base Complexes of Iron(III), Cobalt(II) and Nickel(II) Ions and their Catalytic Activity in Oxidation of Phenol and Cyclohexene

The polymer supported transition metal complexes of N,N′‐bis (o‐hydroxy acetophenone) hydrazine (HPHZ) Schiff base were prepared by immobilization of N,N′‐bis(4‐amino‐o‐hydroxyacetophenone)hydrazine (AHPHZ) Schiff base on chloromethylated polystyrene beads of a constant degree of crosslinking and then loading iron(III), cobalt(II) and nickel(II) ions in methanol. The complexation of polymer anchored HPHZ Schiff base with iron(III), cobalt(II) and nickel(II) ions was 83.30%, 84.20% and 87.80%, respectively, whereas with unsupported HPHZ Schiff base, the complexation of these metal ions was 80.3%, 79.90% and 85.63%. The unsupported and polymer supported metal complexes were characterized for their structures using I.R, UV and elemental analysis. The iron(III) complexes of HPHZ Schiff base were octahedral in geometry, whereas cobalt(II) and nickel(II) complexes showed square planar structures as supported by UV and magnetic measurements. The thermogravimetric analysis (TGA) of HPHZ Schiff base and its metal complexes was used to analyze the variation in thermal stability of HPHZ Schiff base on complexation with metal ions. The HPHZ Schiff base showed a weight loss of 58% at 500°C, but its iron(III), cobalt(II) and nickel(II) ions complexes have shown a weight loss of 30%, 52% and 45% at same temperature. The catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in presence of hydrogen peroxide as an oxidant. The supported HPHZ Schiff base complexes of iron(III) ions showed 64.0% conversion for phenol and 81.3% conversion for cyclohexene at a molar ratio of 1∶1∶1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 55.5% conversion for phenol and 66.4% conversion for cyclohexene at 1∶1∶1 molar ratio of substrate to catalyst and hydrogen peroxide. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 90.5% and 96.5% with supported HPHZ Schiff base complexes of iron(III) ions, but was found to be low with cobalt(II) and nickel(II) ions complexes of Schiff base. The selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was different with studied metal ions and varied with molar ratio of metal ions in the reaction mixture. The selectivity was constant on varying the molar ratio of hydrogen peroxide and substrate. The energy of activation for epoxidation of cyclohexene and phenol conversion in presence of polymer supported HPHZ Schiff base complexes of iron(III) ions was 8.9 kJ mol−1 and 22.8 kJ mol−1, respectively, but was high with Schiff base complexes of cobalt(II) and nickel(II) ions and with unsupported Schiff base complexes.

Styrene oxidation by H2O2 using Ni–Gd ferrites prepared by co-precipitation method

Abstract Gadolinium substituted nickel ferrites were prepared by co-precipitation method using NaOH at pH 14 at room temperature. Spinel phase formation was identified by taking the XRD pattern. DRIFT, TG, BET surface area and pore volume measurements, SEM and EDAX were the other characterization techniques used. Mossbauer analysis was performed to find out the site distribution of iron. Under optimized conditions, the prepared spinels were selectively forming benzaldehyde by the oxidation of styrene. Hydrogen peroxide was used as the oxidant. Effect of reaction temperature, reaction time, styrene to hydrogen peroxide molar ratio and effect of solvent medium were also studied.

Products of Cu(II)-catalyzed oxidation of the N-terminal fragments of α-synuclein in the presence of hydrogen peroxide

Reactive oxygen species (ROS) may provide the covalent modifications of amino acid residues in proteins, formation of protein–protein cross-linkages, and oxidation of the protein backbone resulting in protein fragmentation. In an attempt to elucidate the products of the copper(II)-catalyzed oxidation of the (1–17), (1–28), (1–39) and (1–39)(A30P) fragments of α-synuclein, the high performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) methods and Cu(II) /hydrogen peroxide as a model oxidizing system were employed. Peptide solution (0.50 mM) was incubated at 37 °C for 24 h with metal:peptide:hydrogen peroxide molar ratio 1:1:4 in phosphate buffer, pH 7.4. Oxidation targets for all peptide studied are the methionine residues (M 1, M 5). Incubation 24 h of the (1–28), (1–39) and (1–39)(A30P) fragments in aerobic conditions lead to the oxidation of one methionine residue to methionine sulfoxide. Reaction of hydrogen peroxide with all fragments of α-synuclein resulted in oxidation of two methionine residues (M 1, M 5) to methionine sulfoxides. For the Cu(II):peptide:hydrogen peroxide 1:1:4 molar ratio systems the further oxidation of methionine residues to sulfone was observed. The cleavage of the peptide bond M 1–D 2 for all peptides studied was observed as metal binding residues. For the (1–39) and (1–39)(A30P) fragments of α-synuclein the molecular ions with lower molecular masses (A 11–Y 39, E 13–Y 39) were also detected.

Optimization of the chemoenzymatic epoxidation of soybean oil

AbstractThe lipase Candida antarctica (Novozyme 435) immobilized on acrylic resin was used as an unconventional catalyst for in situ epoxidation of soybean oil. The reactions were carried out in toluene. The peracid used for converting TG double bonds to oxirane groups was formed by reaction of FFA and hydrogen peroxide. The reaction conditions were optimized by varying the lipase concentration, solvent concentration, molar ratio of hydrogen peroxide to double bond, oleic acid concentration, and reaction temperature. The kinetic study showed that 100% conversion of double bonds to epoxides can be obtained after 4 h. The addition of free acids was not required for the reaction to proceed to conversions exceeding 80%, presumably owing to generation of FFA by hydrolysis of soybean oil. The enzyme catalyst was found to deteriorate after repeated runs.

Toluene oxidization to benzaldehyde in subcritical water

Effects of reaction parameter on yield of benzaldehyde produced from toluene oxidization using hydrogen peroxide in subcritical water are investigated. The experimental results show that if the molar ratio of hydrogen peroxide to toluene is controlled within a reasonable range, the by-products may be neglected. The optimum technology of toluene oxidization to benzaldehyde is reaction time 60 min,reaction temperature 350 °C, molar ratio of hydrogen peroxide to toluene 3.5. The yield of benzaldehyde can reach 17.2% under the optimum condition. Research results of chemical reaction kinetics show that the consecutive reaction consists of two first-order reaction, and activation energy of these two reactions are 89 kj·mol−1 and 76 kJ·mor−1 respectively.

Liquid-Phase Oxidation of Carvacrol Using Zeolite-Encapsulated Metal Complexes

We report here the use of zeolite-encapsulated metal (salpn) complexes as catalysts in the oxidation reaction of the natural compound carvacrol in acetonitrile with hydrogen peroxide as the oxidant. No previous studies on the oxidation of carvacrol in the presence of metal salpn complexes have been reported. By using a general flexible ligand method, Cr(III), Fe(III), Bi(III), Ni(II), and Zn(II) complexes of N,N'-bis(salicylidene)propane-1,3-diamine (H 2 salpn) encapsulated in NaY zeolite were prepared. All catalysts were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses to confirm the complex encapsulation. The activities of all prepared catalysts for the oxidation of carvacrol and hydrogen peroxide were tested. The performances of all catalysts were compared on the basis of the leaching test results and carvacrol conversions. Thymohydroquinone and benzoquinones were observed as byproducts at high conversions of carvacrol. No product was formed in the absence of a catalyst. Fe(salpn)-NaY catalyst exhibited the highest carvacrol conversion of 27.6% with a yield of 22.0%, followed by Cr(salpn)-NaY catalyst with 23.5% carvacrol conversion and a yield of 17.6%. Other catalysts have shown relatively lower performances in terms of carvacrol conversion and leaching. The Cr(salpn)-NaY catalyst was found to be a more efficient catalyst than others on the basis of leaching and activity tests. With the selected catalyst Cr (salpn)-NaY, the effects of temperature and carvacrol/hydrogen peroxide molar ratio on carvacrol oxidation reactions were investigated. Increasing the temperature from 40 to 60 °C caused an increase in the thymoquinone yield from 6.2% to 16.0%. An increase in carvacrol/hydrogen peroxide molar ratio from 1 to 3 resulted in a decrease in the thymoquinone yield.

Effect of hydroxyl radical on the structure of multi-walled carbon nanotubes

In this research, we present the systematic investigation of the effect of hydroxyl radical (HO ) on the structure of multi-walled carbon nanotubes (MWNTs) via Fenton oxidation treatment in given conditions: molar ratio of hydrogen peroxide (H 2O 2) and ferrous ion (Fe 2+) is approximately equal to 10 and pH value is controlled at 3 ± 0.5. Fenton oxidation process was followed and characterized by using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The experimental results showed that the original graphene structure was disordered/destroyed by the newly generated oxygen-containing functional groups including OH, COOH and quinone groups, which were introduced while MWNTs was treated by Fenton reagents (Fe 2+–H 2O 2). Moreover, two attackable routes for possible mechanism of interactions between HO and MWNTs were assumed by spectral changes and properties of reactive species, which were described as follows: (l) a preferred attack on defect sites existing in the purified MWNTs sample (2) a synchronous or succedent attack on unsaturated bonds of C C on the sidewalls of MWNTs by electrophilic addition reaction. The possible mechanism indicated that introduction of those functional groups into the structure of MWNTs could be regarded as the results of attacks of HO with double properties of oxidizability and electrophilic addition on defect sites and unsaturated bonds of C C in the MWNTs sample, which were consistent with spectral changes in infrared spectroscopy and Raman spectroscopy.

Epoxidation of 1,4-bis(allyloxy)butane by hydrogen peroxide using phase transfer catalysis

Epoxidation of 1,4-bis(allyloxy)butane by hydrogen peroxide under phase transfer catalysis and transition metal salts was investigated. The most advantageous conditions for the epoxidation were determined (temperature, reaction time, the type and amount of phase transfer catalyst, molar ratio of hydrogen peroxide to 1,4-bis(allyloxy)butane, the amount and molar ratio of H 3PO 4:Na 2WO 4·2H 2O). The process was evaluated in terms of the conversion of 1,4-bis(allyloxy)butane, hydrogen peroxide and the yields of monoepoxide and diepoxide.

A simple chemical synthesis of nanocrystalline AFe 2O 4 (A = Fe, Ni, Zn): An efficient catalyst for selective oxidation of styrene

Nanosized spinel ferrite (AFe 2O 4, A = Ni, Fe, Zn) catalysts are prepared by ‘bottom-up’ approach, i.e. first forming the nanostructured building blocks and then assembling them into the final material with average particle size of 7–12 nm and surface area of 80–100 m 2/g. The synthesized nanocrystallites were characterized by thermal analysis, powder X-ray diffraction, transmission electron microscopy and inductively coupled plasma (atomic emission spectroscopy) technique for evaluating phase, structure and morphology and stoichiometry. These materials were found to be very good catalysts for the oxidation of styrene to benzaldehyde in the presence of hydrogen peroxide. Of the several catalysts tried, magnetite (Fe 3O 4) has shown to have the best catalytic activity for the above reaction. The effects of solvent medium used, styrene:hydrogen peroxide molar ratio, reaction temperature, time and reaction atmosphere required for the complete conversion of styrene to benzaldehyde were also studied. Based on our findings, a plausible mechanism involved in the catalytic reaction is proposed.

Role of apoplastic ascorbate and hydrogen peroxide in the control of cell growth in pine hypocotyls.

The growth cessation of plant axis has been related with the formation of diphenyl bridges among the pectic components of the cell wall caused by the action of apoplastic peroxidases using hydrogen peroxide as electron acceptor. The formation of diphenyl bridges is prevented by the presence of ascorbate in the apoplastic fluid which acts as a hydrogen peroxide scavenger. The current work focuses on the role of the apoplastic ascorbate and hydrogen peroxide in the cell growth. The addition of hydrogen peroxide caused an inhibition of the auxin-induced growth as well as a significant decrease in the cell wall creep induced by acid-pH solutions. The hydrogen peroxide content in apoplastic fluid increased with the hypocotyl age and along the hypocotyl axis of 10-day-old pine seedlings, as the growth capacity decreased. On the other hand, the ascorbate content in the apoplastic fluid decreased with the hypocotyl age and along the hypocotyl axis of 10-day-old seedlings. A very significant correlation between the hydrogen peroxide apoplastic level and the growth rate as well as between the ascorbate/hydrogen peroxide molar ratio and the growth rate of hypocotyls have been found suggesting that the redox state is the main factor controlling the cell wall stiffening mechanism and thus growth in pine hypocotyls.

Peroxone Process for RO-16 and RB-19 Dye Solutions Treatment

To obtain a better treatment efficiency for dye or textile wastewater, a semi-batch and a continuous peroxone process using a new gas-inducing reactor were investigated in this study. In the semi-batch peroxone process, the results show that the peroxone process does not improve the color value (ADMI) removal rate, regardless of the pH value. However, the chemical oxygen demand (COD) removal rate could be enhanced in this peroxone process at higher pH value, but the extent of improvement is only slight. The optimal molar ratio of hydrogen peroxide to ozone (H2 O2 O3) is 1.0, and at this condition, the mass ratio of removed COD to consumed ozone (ΔCOD ΔO3) is twice as high as that in the ozone alone process. In the continuous peroxone process, the hydrogen peroxide addition also does not improve the ADMI removal. However, the COD removal is improved more significantly in the continuous peroxone process. The optimal H2 O2 O3 molar ratio for the continuous peroxone process varies with the input liquid flow rate (Q L ). For liquid flow rate of 0.5 L/min, the optimal H2 O2 /O3 molar ratio is 3.0 and the COD removal percentage (R COD) reaches 50.0˜55.8%, providing about 15 min oxidation time, for the two kinds of dye solutions that were investigated in this study. The optimal residual hydrogen peroxide concentration in the working solution ([H2O2]res.) is about 1.7 × 10−2 mol/L, providing an input rate of ozone at 8.8 × 10−2 mol/h.

Treatment of aqueous chlorophenol by phthalic anhydride-modified horseradish peroxidase

The reaction conditions of removal of chlorophenols from aqueous solution catalysed by phthalic anhydride (PA)-modified horseradish peroxidase were investigated. The optimal pH for chlorophenol removal decreased with increase in substituent number and it was not related to substituent position on aromatic ring. The optimum molar ratio of hydrogen peroxide to chlorophenol was 1.25. The effects of different substrates on phenolics removal were also investigated. The mixed phenolics were more easily removed. PA-modified horseradish peroxidase was more efficient in chlorophenol removal than native horseradish peroxidase either at low temperature or at high temperature. Aromatics with electron-withdrawing substituents (e.g. Cl) at the p-position favour removal over those with substituents at the o- or m-positions. The removal efficiency of 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol was almost equal and it was all lower than that of 4-chlorophenol. The kinetic constants for chlorophenol oxidation with native and PA-modified horseradish peroxidase were also determined. The kinetic data also proved the trend of removal of different chlorophenols with native or PA-modified horseradish peroxidase.

Increased thermostability and phenol removal efficiency by chemical modified horseradish peroxidase

Horseradish peroxidase was modified by phthalic anhydride and glucosamine hydrochloride. The thermostabilities and removal efficiencies of phenolics by native and modified HRP were assayed. The chemical modification of horseradish peroxidase increased their thermostability (about 10- and 9-fold, respectively) and in turn also increased the removal efficiency of phenolics. The quantitative relationships between removal efficiency of phenol and reaction conditions were also investigated using modified enzyme. The optimum pH for phenol removal is 9.0 for both native and modified forms of the enzyme. Both modified enzyme could suffer from higher temperature than native enzyme in phenol removal reaction. The optimum molar ratio of hydrogen peroxide to phenol was 2.0. The phthalic anhydride modified enzyme required lower dose of enzyme than native horseradish peroxidase to obtain the same removal efficiency. Both modified horseradish peroxidase show greater affinity and specificity of phenol.

Investigations of thermal polymerization in the stable free-radical polymerization of 2-vinylnaphthalene

The feasibility of utilizing stable free-radical polymerization (SFRP) in the synthesis of well-defined poly(2-vinylnaphthalene) homopolymers has been investigated. Efforts to control molecular weight by manipulating initiator concentration while maintaining a 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO):benzoyl peroxide (BPO) molar ratio of 1.2:1 proved unsuccessful. In addition, systematic variations of the TEMPO: BPO molar ratio did not result in narrow molecular weight distributions. In situ Fourier transform infrared spectroscopy (FTIR) indicated that the rate of monomer disappearance under SFRP and thermal conditions were identical. This observation indicated a lack of control in the presence of the stable free radical, TEMPO. The similarities in chemical structure between styrene and 2-vinylnaphthalene suggested thermally initiated polymerization occurred via the Mayo mechanism. A kinetic analysis of the thermal polymerization of styrene and 2-vinylnaphthalene suggested that the additional fused ring in 2-vinylnaphthalene increased the propensity for thermal polymerization. The observed rate constant for thermal polymerization of 2-vinylnaphthalene was determined using in situ FTIR spectroscopy and was one order of magnitude greater than styrene, assuming pseudo-first-order kinetics. Also, an Arrhenius analysis indicated that the activation energy for the thermal polymerization of 2-vinylnaphthalene was 30 kJ/mol less than styrene.