Antioxidants and stabilizers, 117. Contribution to the transformation mechanism of 2,6-di-tert-butyl-4-methylphenol,a processing stabilizer for polyolefins

2,6-Di-tert-butyl-4-methylphenol (1) , a polyolefin processing stabilizer, is transformed during the stabilization process primarily into 2,6-di-tert-butyl-4-methyl-phenoxyl (2) . The important consecutive transformation pathway of 2 involves irreversible C? C coupling giving 4,4′-ethylenebis(2,6-di-tert-butylphenol) (8) and reversible C? C coupling accounting for formation of 2,6-di-tert-butyl-4-methyl-4-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,5-cyclohexadiene-1-one (9) . The stepwise transformation of 9 into the parent phenol 1 , the stable dimer 8 and a variety of other products was found in EPR and chromatographic studies of free radical and molecular products generated from 9 in oxidative environment. It follows that compounds 1, 8 and 9 are stepwise transformed into coloured quinoide and quinonemethinoide compounds in the ultimate phase, and the antioxidant chain-breaking character of 1 is thus lost. It is considered that most of the free radical species formed transiently during transformation of 1 and/or of derived phenolic coupling products disappear from the system via disproportionation and alkylperoxy radicals (RO₂) or oxygen trapping. Labile, cross-conjugated, peroxidic species generated by the latter process contribute to the fragmentation of coupling products.     

新型抗氧剂KY-1330合成的研究

采用两步法合成抗氧剂1,3,5-三甲基-2,4,6-三(3,5-二叔丁基-4-羟基苄基)苯(KY-1330),先以2,6-二叔丁基苯酚和多聚甲醛为原料,醚化合成3,5-二叔丁基-4-羟基苄基甲基醚,再与均三甲苯进行缩合反应得到抗氧剂KY-1330。通过正交实验优化了反应条件,醚化条件为:2,6-二叔丁基苯酚15.0 g,多聚甲醛3.5 g,催化剂二甲胺用量1.5 mL,反应温度100℃,反应时间为190 min,搅拌速度100 r/min,产率为87.2%;缩合条件为:3,5-二叔丁基-4-羟基苄基甲基醚与均三甲苯的摩尔比为4∶1,反应温度为5℃,反应时间为120 min,硫酸质量分数为80%,产率为81.5%。     

Tyrosinase-glucose dehydrogenase substrate-recycling biosensor: A highly-sensitive measurement of phenolic compounds

Mushroom tyrosinase and glucose dehydrogenase from Acinetobacter calcoaceticus were immobilized in poly(vinyl)alcohol membranes and coupled with a Clark-type oxygen electrode to give a substrate (analyte) regenerating cycle for monitoring of nanomolar concentrations of phenolic compounds. In this way the response for catechol, phenol, p-cresol, p-chlorophenol and p-acetamidophenol was amplified by a factor of 450, 300, 240, 150, and 140, respectively. The resulting detection limit for catechol and phenol is 0·6 nmol dm⁻³ and 0·9 nmol dm⁻³, respectively. The measuring linear range for phenol obtained by the amplified electrode extends from 1 to 400 nmol dm⁻³. The comparison with the chemical (ascorbic acid) regeneration of the phenolic compounds demonstrates the efficiency of the enzymatic procedure. The biosensor can be used for monitoring of phenolic compounds in environmental or industrial samples.     

Preparation of resins containing phenol derivatives from chloromethylstyrene-tetraethyleneglycol dimethacrylate copolymer beads and antibacterial activity of resins

Copolymer beads (RCCS-4G) with many chloromethyl groups were prepared by treating macroreticular chloromethylstyrene-tetraethyleneglycol dimethacrylate (4G) copolymer beads with chloromethylether. Copolymer beads (RAAS-4G) with benzylamino groups were prepared by treating RCCS-4G with potassium phthalimide. Then the copolymer beads containing phenol derivatives were prepared by treating RAAS-4G with p-hydroxybenzoic acid (pHBA), 2,4-dihydroxybenzoic acid (DHBA), and 3,4,5-trihydroxybenzoic acid (gallic acid, GA) in N,N-dimethylformamide. The antibacterial activity of the obtained resins was examined against Escherichia coli and Staphylococcus aureus. Resins containing phenolic hydroxy groups of 2.3–7.7 mequiv/g were obtained. Antibacterial activity of the resins containing various phenol derivatives against E. coli or S. aureus increased in the order of RAAS-4G-GA > RAAS-4G-DHBA > RAAS-4G-pHBA. The resins containing phenol derivatives exhibited higher antibacterial activity against E. coli than against S. aureus and high activity even against bacteria in NaCl solution. Scanning electron micrographs showed that high antibacterial activity was brought about by the phenolic hydroxyl groups in the resin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1621–1630, 1997     

Biosorption of phenolic compounds from aqueous solutions onto chitosan–abrus precatorius blended beads

BACKGROUND: This research focuses on understanding the biosorption process and developing a cost‐effective technology for the treatment of water contaminated with phenolic compounds (phenol, 2‐chlorophenol and 4‐chlorophenol), which are discharged into the aquatic environment from a variety of sources and are highly toxic. In order to remove phenolic compounds from water, a new biobased sorbent is developed, blending chitosan with abrus precatorius, both naturally occurring biopolymers. The resulting chitosan–abrus precatorius blended beads (CS/Ab) were characterized by Brunauer, Emmett and Teller (BET) analysis, Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques under batch equilibrium and column flow experimental conditions. The binding capacity of the biosorbent was investigated as a function of initial pH, contact time, initial concentration of adsorbate and dosage of adsorbent. RESULTS: The percentage removal of phenol, 2‐CP and 4‐CP increased with increasing adsorbent dose, while the adsorption capacity at equilibrium, q_e (mg g^?1) (amount of phenol, 2‐CP and 4‐CP loaded per unit weight of adsorbent) decreased. The equilibrium time was found to be 240 min for full equilibration of all adsorbates. Adsorption kinetic and isotherm studies showed that the pseudo‐first‐order model and the Langmuir isotherm were the best choices to describe the adsorption behaviors. The maximum monolayer adsorption capacity of phenol, 2‐CP and 4‐CP on to the (CS/Ab) beads was found to be 156 mg g^?1, 204 mg g^?1 and 278 mg g^?1, respectively. CONCLUSION: The experimental results suggested that (CS/Ab) blended beads are effective in the removal of phenolic compounds from aqueous medium. Copyright © 2009 Society of Chemical Industry     

Processability and properties of phenoxy resin toughened phenolic resin composites

A novel method has been developed to toughen phenolic resin using phenoxy resin. Phenoxy resin was dissolved in phenol to form a glutinous mixture at 110°C, and an acid catalyst (p-toluene sulfonic acid, PTSA) was utilized to reduce the viscosity of mixture. The mixture was blended with resole-type phenolic resin. IR spectra confirmed that the amount and strength of hydrogen bonds increased with PTSA content, and the viscosity decreased with PTSA content in the polymer blends. The wet-out of glass fiber by modified resin was improved. The flexural and notched Izod impact strength of the polymer-blend composites increased significantly. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 911–917, 1997     

Synthesis of novolac‐type phenolic resins using glucose as the substitute for formaldehyde

Novel Novolac type phenolic resins were prepared using glucose as the substitute for toxic formaldehyde (a carcinogenic chemical). The resins were synthesized with varying molar ratios of phenol to glucose, catalyzed by strong acid (such as sulfuric acid) at 120–150°C. Analysis of the resins using gel permeation chromatography (GPC) and proton nuclear magnetic resonance (¹H‐NMR) showed that they were broadly distributed oligomers derived from the Fridel‐Crafts condensation of phenol and glucose. Using hexamethylenetetramine (HMTA) as the curing agent, the phenol‐glucose resins could be thermally cured and exhibited exothermic peaks at 130–180°C, typical of thermosetting phenolic resins. The cured resins showed satisfactory thermal stability, e.g., they started to decompose at >280°C with residual carbon yields of above 58% at 600°C. Based on the thermal properties, phenol‐glucose resin with a molar ratio of 1 : 0.5 is promising as it could be cured at a lower temperature (147°C) and exhibited a satisfactorily good thermal stability: it started to decompose at >300°C with a residual carbon yield of >64% at 600°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Separation of aqueous phenol through polyurethane membranes by pervaporation

The separation of a phenol-water mixture using a polyurethane membrane by a pervaporation method was investigated. Polyurethane was selected as a membrane material because its affinity for phenol was considered to be high. Polyurethane was prepared by the polyaddition of 1,6-diisocyanatohexane and polytetramethyleneglycol. The polyurethane layer was sandwiched with a porous polypropylene membrane (Celgard® 2500). Pervaporation measurement was carried out under vacuum on the permeate side, and the permeate vapor was collected with a liquid nitrogen trap. The phenol concentration in the permeate solution increased from 0 to 65 wt % with increasing feed concentration of phenol from 0 to 7 wt %. The total flux also increased up to 930 g m^-2 h^-1 with increasing phenol partial flux. In the sorption measurement at 60°C, the concentration of phenol in the membrane was 68 wt %, which was higher than that of the permeate solution. Therefore, it was considered that the phenol selectivity was based on high solubility in the polyurethane membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:469–479, 1997     

Synthesis and characterization of the dihydrosalpren ligand (H2L1) and of its trinuclear Ni(II) complex

The synthesis of the new unsymmetrical tetradendate Schiff ligand N-(2-hydroxybenzyl)-N′-(2-hydroxybenzylidene)-1,3-diaminopropane (H₂L¹) is reported. The ligand comprises two different coordination moieties: a rigid salicylaldimmine unit and a more flexible (2-hydroxybenzyl)-amino (hydrogenated salicylaldimmine) unit. The reaction of H₂L¹ with Ni(OAc)₂·4H₂O (1:1 molar ratio) leads to the spontaneous formation of a trinuclear complex with composition {[Ni(L¹)OH₂]₂(OAc)₂Ni}·2H₂O, characterized by X-ray crystallography, where two [Ni(L¹)] units act as O,O-bidentate chelate to a Ni(II) ion.     

Novel phosphorus‐containing dicyclopentadiene‐modified phenolic resins for flame‐retardancy applications

2‐[4‐(2‐hydroxyphenyl)tricyclo[5.2.1.0^2,6]dec‐8‐yl]phenol (HPTCDP) were prepared from dicyclopentadiene (DCPD) and phenol via Friedel‐Crafts alkylation. DCPD‐containing phenolic resin (DPR) was also synthesized by incorporating the DCPD‐containing monomer HPTCDP with formaldehyde. DPR was further modified by grafting the phosphate group. The phosphorylation was confirmed by a Fourier transform infrared, ³¹P‐NMR spectroscopy, and an element analysis. The phosphorus content in the DPR could be successfully tailored to give values of 3.46 to 7.79 wt % by varying the feeding ratios of the phosphorus group. The thermal stabilities of the phosphorus‐containing polymers were identified by differential scanning calorimeter and thermogravimetric analysis. The glass transition temperature values were decreased as the content of phosphorus increased. High char yield 39–47 wt % in thermogravimetric analysis evaluation and limiting oxygen index values of 27 to 34 were found for all the phosphorylated phenolic resins. Such properties make these polymers highly promising for flame‐retardant applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 342–349, 2001     

Synthesis of novel poly(phthalazinone ether sulfone ketone)s and improvement of their melt flow properties

A series of novel poly(phthalazinone ether sulfone ketone)s was synthesized from bis(4-fluorophenyl) ketone, bis(4-chlorophenyl)sulfone, and 4-(4-hydroxybenzyl)-2,3-phthalazin-1-one through nucleophilic substitution polycondensation. The synthesized polymers exhibited surprisingly high glass transition temperatures and had excellent thermooxidative properties. The melt viscosities of these synthesized polymers are generally too high to be processed by common processing methods because of their very high glass transition temperatures and amorphous microstructure. An attempt was made to reduce their melt viscosities by solution blending the synthesized polymer with two kinds of oligomers: low molecular weight poly(phthalazinone ether sulfone ketone) and commercial poly(ether sulfone). The results proved that the addition of the oligomers to the polymers led to a marked decrease in melt viscosities. Furthermore, no obvious changes were observed in the thermal and mechanical properties of these blends after oligomer additions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1425–1432, 1997     

Sensitive molecular determination of polycyclic aromatic hydrocarbons based on thiolated Calix[4]arene and CdSe quantum dots (QDs)

A novel and sensitive electrochemical sensor based on the cone conformation of the supramolecule 25, 27-(3-thiopropoxy)-p-tert-butyl calix[4]arene has been developed for quantitative determination of polycyclic aromatic hydrocarbons (PAHs). The method works effectively by immobilizing calix[4]arenes on Fe₃O₄ magnetic nanoparticles. CdSe quantum dots were used as electrochemical labels. CdSe quantum dots (QDs) modified PAHs in competition with the sample PAHs were intercalated into calix[4]arenes supramolecules via a host–guest interaction through individual bowl-shaped calix[4]arenes. The stripping analysis of the cadmium dissolved from CdSe nanoparticles provided a sensitive method for the detection of PAHs in the samples. The signal decrease of the QDs was proportional to the increase in the concentration of the PAHs. Under optimal conditions, among the five PAHs, the square wave voltammetry (SWV) response of QDs decreased linearly for anthracene and naphthalene in the range of 2.1 × 10^?7–1.4 × 10^?5 and 1.5 × 10^?6–2.5 × 10^?5 M, respectively. The calculated detection limits (3δ) were 20.1 ng mL^?1 for anthracene and 105.5 ng mL^?1 for naphthalene.     

Utilization of Raw and Activated Date Pits for the Removal of Phenol from Aqueous Solutions

Activated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N₂ atmosphere and activation at 900 °C in CO₂ atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.     

Polyallylamine-conjugated thermo-responsive polymers for the rapid removal of phenolic compounds from water

Polyallylamine-conjugated thermo-responsive polymer (PNIPAAm-PAA) was readily prepared by the condensation of polyallylamine and poly(N-isopropylacrylamide-co-acrylic acid) with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The synthesized polymer was water-soluble below the lower critical solution temperature (LCST, ca. 34 °C) but deposited to form a condensed coagulate by heating the solution above the LCST. In the presence of phenol oxidation enzymes, phenolic compounds was oxidized and spontaneously bound to the amino group of PNIPAAm-PAA. Almost complete removal of 300 mg l⁻¹ phenol was achieved by the use of 1 g l⁻¹ PNIPAAm-PAA. However, long time was required for the oxidation of phenol by using mushroom tyrosinase. On the other hand, combined use of horseradish peroxidase and hydrogen peroxidase allowed rapid phenol removal. Furthermore, the proposed method was applicable to the removal of a wide range of phenolic compounds including estrogenic hormones. The applicability to wastewater treatment was successfully demonstrated using spiked effluents.     

Landfill co-disposal of phenol-bearing wastewaters: Organic load considerations

A multi-stage model, operated with single elution, was used to investigate the effects of organic loadings on the attenuation of a model phenolic wastewater in domestic refuse. Although 100% dissimilation of influent phenol (2–5 mmol dm^?3) was recorded at a dilution rate of 0.007 h^?1, partial inhibition of both phenol degradation and species competing with methanogens for a common electron donor(s) was apparent at concentrations ±4 mmol dm^?3. On extended perfusion with 8 mmol phenol dm^?3, the progressive inhibition of phenol dissimilation was not obviated by nutrient supplementation. Simultaneous degradation of the catabolic intermediate, hexanoic acid, and elevated methane release rates suggested that the transformation of phenol to hexanoate was rate limiting.     

Fiberboards Based on Sugarcane Bagasse Lignin and Fibers

Summary: Fiberboards were prepared using phenolic type resins (phenol‐formaldehyde) and sugarcane bagasse fibers. Lignin extracted through an organosolv process from sugarcane bagasse was used as substitute of phenol in phenolic resins from 40 (lignin‐phenol‐formaldehyde) to 100 wt.‐% (lignin‐formaldehyde) substitution. Some of the fibers were chemically modified by oxidation with chlorine dioxide and treatment with furfuryl alcohol (FA), leading to fibers coated with polyfurfuryl alcohol. Thermal analysis (DSC and TGA) of the prepolymers allowed setting up an efficient curing to prepare fiberboards. Impact strength and water absorption were measured showing the importance of the curing pressure to obtain good performance. When chemically modified fibers were used to prepare board samples, enhanced durability against white root fungi is observed, and to a less degree against brown root fungi. Sugarcane bagasse fiberboards were prepared from prepolymers where lignin substituted phenol up to 100%. This replaces these materials in advantageous position, relating to those prepared from phenol‐formaldehyde resins, due to their high content of renewable raw materials. The results obtained are promising for the utilization of sugarcane bagasse as raw materials for preparing fiberboards to be used in tropical areas.

Stabilization of sugarcane bagasse fiberboards made with unmodified and modified (ClO₂ + furfuryl alcohol) fibers and phenolic resin after 8 weeks exposure against fungi.     

Influence of carbonization conditions and wood species on carbon dioxide reactivity of resultant wood char powder

Carbon dioxide reactivities of powdered samples of Acacia and Eucalyptus wood chars were measured thermogravimetrically at 900°C and the effects of carbonization conditions (temperature, heating rate and soaking time) and wood species were determined. The results showed that the reactivity decreased with increasing carbonization temperature and soaking time. Chars prepared under rapid carbonization (heating rate: 30°C min⁻¹) were found to be more reactive than the chars produced by slow carbonization (heating rate: 4°C min⁻¹). In comparison to Eucalyptus wood chars, the Acacia wood chars exhibited higher reactivity.     

Profile of enzyme in drupe of oueslati's cv. olives during ripening phases: A support method implementation in the production of extra virgin olive oil

Quality of virgin olive oil (VOO) depends on phenolic molecules content, which depends on the biochemical characteristics of olive fruits, namely endogenous enzymes. In order to ascertain the influence of olive fruit ripening degree on the phenol content, enzyme activities in olive fruits, and the quality of the corresponding oils were studied during Oueslati olive ripening. In fact, three enzymes were studied: peroxidase (POX) in olive seeds, polyphenoloxidase (PPO), and β-glucosidase (β-GL) in olive fruits mesocarp. Each enzyme showed specific trend: POX activity increased gradually until reaching a maximum (17.061 ± 0.101 U g⁻¹ FW) at ripening index (RI) 3.6 and then decreased slowly at advanced ripening stage. However, the maximum of PPO activity (240.421 ± 0.949 U g⁻¹ FW) was observed earlier at RI of 0.7. Concerning β-glucosidase activity, its maximal was 60.857 ± 1.105 U g⁻¹ FW at RI 2.8, then, it decreased sharply to reach 17.096 ± 0.865 U g⁻¹ FW at RI 3.9. A significant increase of total phenol content as well as the antioxidant activity were observed during Oueslati olive ripening. Moreover, phenolic profile indicated that appropriate harvesting date of Oueslati olives coincided with RI 3.9 given that highest content of most important individuals phenolic compounds responsible for the main VOO biological properties achieved on this date. Furthermore, phenols amount of Oueslati VOO was principally due to PPO enzyme activity as the increase in total phenols coincides with the decrease in PPO activity.     

Tri-n-butyltin hydride reduction of the end group of a polyphenylene ether

Summary A method using tri-n-butyltin hydride to reduce the 2-methyl-6-(N,N-di-n-butylamino)methyl phenol end group on PPO^®(4) was developed. It generated a polyphenylene ether (PPE) with 2,6-xylenol as the only phenolic end group without causing any significant increase in molecular weight.     

Degradation Pathway of Ozone Oxidation of Phenols and Chlorophenols as Followed by LC-MS-TOF

ABSTRACT

This contribution summarizes the temporal intermediates produced during the ozonation of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, as followed by liquid chromatography coupled to a time of flight mass spectrometer (LC-MS-TOF). A 2 × 10^?3 M solution of the phenolic compounds was ozonated in a sintered glass reactor at an ozone dose of 0.14 mg/min (O₂/O₃ flow 10 mL/min). Identified intermediates showed that catechol pathway was the predominant route for phenol oxidation with acrylic acid being the end product. Hydroxylative dechlorination of 2-chlorophenol also gave catechol, and the reaction products were similar to that of phenol. Hydroxylation and ring opening via the 4-chlorocatechol pathways were the predominant route for the ozonation of 4-chlorophenol, while 2,4-dichlorophenol followed both hydroxylation and hydroxylative dechlorination mechanism. Several novel intermediates and coupling products were identified and reaction schemes leading to breakdown products are provided for each phenolic compound.