Methyl Ethyl Ketone Research Articles

Infrared Spectra of (Z)- and (E)-•CH2C(CH3)CHI Radicals Produced upon Photodissociation of (Z)- and (E)-(CH2I)(CH3)C═CHI in Solid para-Hydrogen.

Ozonolysis of isoprene is important in atmospheric chemistry because of the abundant emission of isoprene. This process produces the Criegee intermediates CH2OO, methyl vinyl ketone oxide (MVKO, C2H3C(CH3)OO), and methacrolein oxide (MACRO, CH2C(CH3)CHOO). Gaseous MACRO was recently produced and identified in laboratories after photolysis of a mixture of 1,3-diiodo-2-methyl-prop-1-ene [(CH2I)(CH3)C═CHI] and O2, but the conformation-dependent formation mechanism remains unexplored. We report conformation-distinct IR spectra of (E)- and (Z)-(CH2I)(CH3)C═CHI isolated in solid p-H2. Upon irradiation near 300 nm of (E)- and (Z)-(CH2I)(CH3)C═CHI in solid p-H2 at 3.3 K, 3-iodo-2-methyl-prop-1-en-3-yl [•CH2C(CH3)CHI] radicals were characterized, with intense infrared absorption lines at 2991.3, 1458.7, 1434.7, 1317.4, 1190.4, 786.3, 677.9, and 467.2 cm-1 and additional 11 weaker ones assigned to (E)-•CH2C(CH3)CHI and intense lines at 3108.5, 3076.2, 3028.5, 2970.0, 1174.2, 796.0, 683.6, and 609.5 cm-1 and additional 7 weaker ones to (Z)-•CH2C(CH3)CHI. The assignments were derived according to the behaviors of secondary photolysis at 495 and 460 nm and a comparison of the vibrational wavenumbers and IR intensities of the observed lines with those calculated with the B2PLYP-D3/aug-cc-pVTZ-pp method. These observations confirm that only the allylic C-I bond, not the vinylic one, was photodissociated at 290 nm, and in solid p-H2, the excess energy upon photolysis induced no conformational change. When O2 was present in the matrix, several intense lines at 1147.5, 1025.7, 914.4, and 728.7 cm-1, and 4 weaker ones were tentatively assigned to the adduct CH2C(CH3)CHIOO; the assignments were supported by 18O2 isotopic experiments. Unlike in the gaseous phase, the remaining C-I bond of this adduct could not break to form MACRO because of the efficient quenching in a low-temperature matrix.

Dynamic modelling of removal of binary mixtures of VOCs from indoor air through a carbon-based filter

Carbon-based filters are commonly used to remove volatile organic compounds from indoor air environments. Assessing the filter performance, such as its ability to remove specific pollutants or its efficiency, is crucial to improve air quality in the indoor environment. However, conducting experiments to evaluate the performance of filters for removing volatile organic compounds from indoor air environments can be difficult and time-consuming due to their low indoor concentrations and the presence of complex mixtures of these pollutants. Dynamic models have been used to assist in evaluating the performance of filters for indoor environment applications.In this study, iterative and non-iterative methods were applied to the Dubinin-Radushkevich isotherm, and then they were incorporated into the mass transfer models to represent the adsorption behaviour of a binary mixture of volatile organic compounds (toluene-limonene and toluene- methyl ethyl ketone mixture). Experimental results of binary mixtures containing 9 parts per million volume of each compound were used to measure Dubinin-Radushkevich constants in the iterative method, whereas single-component adsorption experimental results were used in the non-iterative method. Afterwards, the model’s predictions were compared with the experimental results at 0.1 parts per million volume of each compound. The non-iterative method could predict the filter performance for the removal of the toluene and limonene mixture, but there was a systematic deviation for the binary mixture of toluene and methyl ethyl ketone. However, the iterative method, which considers the lateral interaction between the adsorbates, could predict the breakthrough of the filter for the non-ideal mixture of toluene and methyl ethyl ketone correctly. Comparative modelling confirmed the negligible significance of gas-phase diffusion. Also, the comparison between the comprehensive model (Fick’s diffusion for internal mass transfer) and two approximate solutions (linear and quadratic driving force models for internal mass transfer) exhibited the applicability of these intraparticle mass transfer approximations in specific conditions. Finally, the parametric study showed that as the particle size increases, the 100% breakthrough time and initial breakthroughs increase for each component of the binary mixture. However, increasing the air velocity leads to a reduction in 100% breakthrough times and initial efficiencies. At higher inlet concentrations, the breakthrough curves become steeper. Furthermore, the occurrence of the overshoot phenomenon was observed with increasing thickness.

Modification of Jute Fiber with Vinyl Acetate and Methyl Vinyl Ketone for Textile Applications

In the present study, the bleached jute fiber was been modified with Vinyl Acetate (VA) and Methyl Vinyl Ketone (MVK) by graft co-polymerization in an aqueous medium using potassium persulphate as an initiator, under the catalytic influence of FeSO4 in the presence air to improve physicochemical properties. The maximum graft yield and grafting efficiency at the optimized condition for VA and MVK are 26.0%, 11.1% and 10.4%, 3.7% respectively. The graft yield and grafting efficiency of VA-modified fiber were higher than that of MVK-modified field fiber. The grafted fiber was characterized by FTIR, SEM and TGA. FTIR spectra of VA and MVK modified fiber have peaks at 1741cm-1 and 1714cm-1 respectively than the unmodified jute indicating the incorporation of vinyl monomer with the cellulosic jute fiber. By observing thermograms, the degradation temperature of bleached jute fiber was 318.7�C and that for VA and MVK modified fibers was 320�C and 325�C respectively. The breaking strength of bleached fiber was 16.02kg/yarn but VA and MVK modified fibers were 17.3 and 17.00kg/yarn respectively. The dye absorption by modified fiber was slightly decreased than bleached fiber due to the increased hydrophobicity. The wash fastness with soap solution decreased with the increase in washing temperature. The color fastness test of dyed bleached and modified jute fibers spotting with alkalis, and acids were satisfactory with some exceptions. Thus, the modification improves the physicochemical properties of the jute fiber for textile applications.

Atmospheric oxidation of new “green” solvents – Part 2: methyl pivalate and pinacolone

Abstract. Lab-based experimental and computational methods were used to study the atmospheric degradation of two promising “green” solvents: pinacolone, (CH3)3CC(O)CH3, and methyl pivalate, (CH3)3CC(O)OCH3. Pulsed laser photolysis coupled to pulsed laser-induced fluorescence was used to determine absolute rate coefficients (in 10−12 cm3 molec.−1 s−1) of k1(297 K) = (1.2 ± 0.2) for OH + (CH3)3CC(O)CH3 (Reaction R1) and k2(297 K) = (1.3 ± 0.2) for OH + (CH3)3CC(O)OCH3 (Reaction R2), in good agreement with one previous experimental study. Rate coefficients for both reactions were found to increase at elevated temperature, with k1(T) adequately described by k1(297–485 K) = 2.1 × 10−12 exp(-200/T) cm3 molec.−1 s−1. k2(T) exhibited more complex behaviour, with a local minimum at around 300 K. In the course of this work, k3(295–450 K) was obtained for the well-characterised reaction OH + C2H5OH (ethanol; Reaction R3), in satisfactory agreement with the evaluated literature. UV–Vis spectroscopy experiments and computational calculations were used to explore cross-sections for (CH3)3CC(O)CH3 photolysis (Reaction R4), while (CH3)3CC(O)OCH3 showed no sign of absorption over the wavelengths of interest. Absorption cross-sections for (CH3)3CC(O)CH3, σ4(λ), in the actinic region were larger, and the maximum was red-shifted compared to estimates (methyl ethyl ketone (MEK) values) used in current state-of-science models. As a consequence, we note that photolysis (Reaction R4) is likely the dominant pathway for removal of (CH3)3CC(O)CH3 from the troposphere. Nonetheless, large uncertainties remain as quantum yields φ4(λ) remain unmeasured. Lifetime estimates based upon Reactions (R1) and (R4) span the range 2–9 d and are consequently associated with a poorly constrained estimated photochemical ozone creation potential (POCPE). In accord with previous studies, (CH3)3CC(O)OCH3 did not absorb in the actinic region, allowing for straightforward calculation of an atmospheric lifetime of ≈ 9 d and a small POCPE ≈ 11.

Fatty acid distillation residues from rice oil bran refining as a source of phytochemicals

SummaryThe aim of this work was to develop an extraction method to recover γ‐oryzanol and tocopherols from the distillation residue of the fatty acids generated during the neutralisation step of the rice bran oil refining process. The phytochemicals extraction was performed with different solvents (chloroform, methanol, methyl ethyl ketone and acetone) at a ratio of 10:1 v/w (solvent: sample), by agitating the mixture for 10 min at room temperature (20 °C ± 2 °C), then stored at −18 °C for 15 h. The γ‐oryzanol and tocopherol content in the extracted fractions were concentrated and quantified using reverse phase high‐performance liquid chromatography coupled with UV–vis and fluorescence detector, respectively. It was observed that only one step of extraction with methanol resulted in an increased concentration of tocopherols for about six times, with a recovery of 51.50%. However, using two stages of extraction, the mixture of methanol and methyl ethyl ketone (1:1, v/v) allowed the recovery of 92.15% of tocopherols and 84.12% of γ‐oryzanol, increasing the initial concentration of these phytochemicals in about three times. These results show that there is a great possibility of these phytochemicals recovery from the distillation residue from fatty acid recovery.

Olfactory imprinting enhances associative learning and memory in C. elegans

Learning and memory are fundamental processes for an organism's normal physiological function. Learning can occur at any stage of the organism's physiological development. Imprinted memories formed during the early developmental stage, unlike learning and memory, can last a lifetime. It is not clear whether these two types of memories are interlinked. In this study, we investigated whether imprinted memory influences adult learning and memory in a C. elegans model system. We trained the worms for short-term (STAM) and long-term associated memory (LTAM) towards butanone (BT) after conditioning them for imprinted memory towards isoamyl alcohol (IAA). We observed that these worms had improved learning abilities. However, functional imaging revealed that the worms had a long-term depression in the firing pattern in the AIY interneuron, indicating that there were significant changes in neuronal excitation pattern after imprinting, which could explain the enhanced behavioural alterations in animals after imprinting.

Low-Density Unsaturated Polyester Resin with the Presence of Dual-Initiator.

Dual-initiation is a new orientation of many studies in the curing of unsaturated polyester resin and the manufacture of low-density unsaturated polyester resin (LDUPR) composite materials. In our research, two kinds of low-temperature (40-70 °C) initiators (cyclohexanone peroxide (CYHP) and methyl ethyl ketone peroxide (MEKP)), one kind of medium-temperature (70-130 °C) initiator (tert-butyl peroxy-2-ethylhexanoate (TBPO)), and three kinds of high-temperature (≥130 °C) initiators (tert-butyl benzoate peroxide (TBPB), tert-amyl carbonate peroxide-2-ethylhexanoate (TAEC), and tert-butyl carbonate peroxide-2-ethylhexanoate (TBEC)) were applied to constitute different dual-initiators. Those dual-initiators were a low-temperature dual-initiator (CYHP/MEKP), medium-low-temperature dual-initiators (CYHP/TBPO and MEKP/TBPO), and high-temperature dual-initiators (TAEC/TBPB, TAEC/TBEC, and TBEC/TBPB). In the low-temperature and medium-low-temperature ranges, the LDUPR sample displayed the highest specific compression strength (Ps) of 42.08 ± 0.26 MPa·g-1·cm3 in the presence of the MEKP/TBPO dual-initiator. In the high-temperature range, the LDUPR sample exhibited the highest specific compression strength (Ps) of 43.32 ± 0.45 MPa·g-1·cm3 for the existence of the TAEC/TBPB dual-initiator. It is pointed out that the dual-initiator released more active free radicals, accelerating the initial curing time and the peak time of UPR. More active free radicals caused both high-activity (short-chain) molecules and low-activity (long-chain or intertwined) molecules in resin to cross-link, prolonging UPR's curing process by approximately two minutes and resulting in an improvement of UPR's cross-linking. In the presence of a dual-initiator, the integrated and planar microstructure of LDUPR samples performed uniformly distributed dimples, dispersed external forces, and enhanced samples' specific compressive strength.

A signature of aged biogenic compounds detected from airborne VOC measurements in the high arctic atmosphere in March/April 2018

During the PAMARCMiP 2018 campaign (March and April 2018) a proton-transfer-reaction mass spectrometer (PTR-MS) was deployed onboard the POLAR 5 research aircraft and sampled the high Arctic atmosphere under Arctic haze conditions. More than 100 compounds exhibited levels above 1 pmol/mol in at least 25% of the measurements. We used acetone mixing ratios, ozone concentrations, and back trajectories to identify periods with and without long-range transport from continental sources. During two flights, surface ozone depletion events (ODE) were observed that coincided with enhanced levels of acetone, and methylethylketone, and ice nucleating particles (INP).Air masses with continental influence contained elevated levels of compounds associated with aged biogenic emissions and anthropogenic pollution (e.g., methanol, peroxyacetylnitrate (PAN), acetone, acetic acid, methylethylketone (MEK), proprionic acid, and pentanone). Almost half of all positively detected compounds (>100) in the high Arctic atmosphere can be associated with terpene oxidation products, likely produced from monoterpenes and sesquiterpenes emitted from boreal forests. We speculate that the transport of biogenic terpene emissions may constitute an important control of the High Arctic aerosol burden. The sum concentration of the detected aerosol forming vapours is ∼12 pmol/mol, which is of the same order than measured dimethylsulfide (DMS) mixing ratios and their mass density corresponds to approximately one fifth of the measured non-black-carbon particles.

Design of Pyrolysis Plant for Waste Methyl Ethyl Ketone from the Polarizer Manufacturing Process

The rapid growth of the semiconductor industry has made significant strides in addressing clean energy concerns. However, there are still unresolved issues related to waste solvents. One promising approach to tackle these challenges is through pyrolysis. This study selected waste methyl ethyl ketone (MEK) from the industrial sector as the feedstock for pyrolysis, resulting in various residual products such as fixed carbon (char), carbon soot, and fuel gases. Experimental results demonstrated that operating temperatures between 750 and 900 °C under anaerobic conditions yielded 5% to 10 wt% of fixed carbon, along with a small amount of tar and 80% to 90% of fuel gases. The research included lab-scale pilot experiments and field-scale system studies to develop a comprehensive concept for a thermal cracking plant. SolidWorks and Aspen Plus software were applied for calculations involving heat-transfer coefficients, residence time, and the utilization of fuel gases with a boiler or burner. A field system was constructed to scale up the pyrolysis process and effectively eliminate waste solvents, incorporating an automated procedural process.

Recovery of fuel from real waste oily sludge via a new eco-friendly surfactant material used in a digital baffle batch extraction unit

This study focused on developing a new cocktail extraction agent (CEA) composed of solvent and a new surfactant material (SM) for enhancing the efficiency of fuel recovery from real waste oil sludge (WSO). The effects of different solvents (e.g. methyl ethyl ketone (MEK), naphtha, petrol and kerosene), SMs (Dowfax and sodium thiosulfate), extraction time (10–20 min), extraction temperatures (20–60 °C) and CEA/sludge ratios (1–4) on the extraction performance were investigated. SMs and DBBE design enhanced the extraction efficiency by increasing the dispersion of solvent in WSO and enhancing the mixing and mass transfer rates. Results proved that Dowfax was the best SM for oil recovery under various conditions. The best CEA (e.g. MEK and Dowfax) provides the maximum fuel recovery rate of 97% at a period of 20 min, temperature of 60 °C and 4:1 CEA/sludge ratio. The produced fuel was analysed and fed to the distillation process to produce diesel oil. The characteristics of diesel oil were measured, and findings showed that it needs treatment processes prior its use as a finished fuel.

Production of sugars from mixed hardwoods for use in the synthesis of sugar fatty acid esters catalyzed by immobilized‐stabilized derivatives of Candida antarctica lipase B

AbstractThe synthesis of sugar fatty acid esters (SFAEs) from lignocellulosic biomass and oleic acid (C18:1) was catalyzed by immobilized‐stabilized derivatives of Candida antarctica lipase B in a methyl ethyl ketone medium. After steam‐explosion pretreatment of mixed hardwoods and enzymatic hydrolysis at 15%wt solids, xylose and glucose were purified/concentrated to a mass ratio of ~3 to 1. These lignocellulosic sugars were superior to commercial sugars as the carbohydrate source for the esterification reaction in terms of sugar conversions. The highest conversions were obtained using 1.5% w/v of Novozyme 435 (N435, uncoated) as the biocatalyst for the synthesis of SFAEs. Coating the N435 with polyethyleneimine (PEI) prevented enzyme leakage into the reaction medium and produced 35% and 50% higher xylose and glucose conversions to SFAEs, respectively, at the same enzyme loading. After six 24 h reuse cycles with the PEI‐coated N435, xylose conversion decreased by 44%, while a 65% reduction in xylose conversion was observed with the uncoated lipase. Mass spectrometry analysis confirmed the production of xylose and glucose mono‐ and di‐esters. Our purified product presented an emulsion capacity (EC) close to that of a commercial sugar ester and the ECs of the xylose oleate, laurate, and palmitate synthesized in previous studies. © 2023 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Effects of gold and platinum on the activity of catalysts for the complete oxidation reaction of hydrocarbons and carbon monoxide

This study presents synthesis results of catalysts made of perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) using the citrate method and crystallisation at 800°C. The structure of the catalysts was characterised by X-ray diffraction (XRD). The perovskite-like oxide catalyst activity was enhanced with gold (Au) and platinum (Pt). Au was mounted on the perovskite-like oxide catalysts by the sol-gel method. The activity of the perovskite-like oxide La2-xSrxCuO4 (x=0.0, 0.5, 1.0) and the perovskite catalyst LaMnO3/LaCuO3 was evaluated by complete oxidation of volatile hydrocarbons (HCs) in a mixture of toluene and methyl ethyl ketone (MEK) and carbon monoxide (CO) in a microflow analysis system combined with gas chromatography. The results showed that the light-off temperature (the 50% conversion temperature of the catalysts) of the Pt, Au/perovskite catalyst samples decreased significantly. The light-off temperature of the Au/LaSrCuO4 Au nanoparticle catalysts in the complete CO oxidation reaction reached a temperature of 150°C, lower than the Pt/LaSrCuO4 catalyst (170°C), allowing replacement of previous Pt catalysts with Au nanoparticle catalysts. The LaSrCuO4 catalyst had better oxidising activities than the La2CuO4 catalyst, indicating that the addition of strontium (Sr) has increased the catalyst activity, and demonstrates the potential for application in catalytic converters in motorcycles.

Performance of Polyalkyl Acrylate Additives of Various Compositions in Low-Temperature Dewaxing of Oil Raffinates

The performance of polyalkyl acrylate additives of various compositions in low-temperature dewaxing of 11 oil fractions differing in the viscosity and content of waxes, aromatic hydrocarbons, and resins was studied. The dewaxing was performed in a methyl ethyl ketone–toluene mixed solvent. For polyalkyl acrylate with pendant C16–10 alkyl chains, the raffinates can be subdivided into three groups with respect to an increase in the yield of dewaxed oils (relative to the process without additives): increase by 12–13, 5–8, and 3–4%. In most cases, introduction into such polymer of 5–30% polar groups (amino ester, amino amide, amide, oligoethylene glycol) allowed the oil yield to be additionally increased.

Pyrolysis behaviors of di-tert-butyl peroxide in gas and liquid phases: A ReaxFF molecular dynamics simulation

Di-tert-butyl peroxide (DTBP) is widely used for various purposes, including as an initiator, vulcanizator, and fuel additive, but is susceptible to triggering fires and explosions owing to its high thermal risk. Therefore, understanding its atomistic pyrolysis mechanisms is of great importance. In this work, the pyrolysis of DTBP is investigated using ReaxFF molecular dynamics simulations with a validated reactive force field. The effect of temperature on the pyrolysis of DTBP is first investigated, followed by the product and intermediate distributions. The results reveal that the system density is crucial in the pyrolysis behaviors of DTBP. The pyrolysis products of gaseous DTBP are found to be acetone, ethane, and methyl tert-butyl ether, while those of liquid DTBP include acetone, tert-butanol, methyl tert-butyl ether, methane, 2-methoxypropene, isobutene, and methyl ethyl ketone, which is in reasonable agreement with the results of previously reported experiments. The detailed reaction pathways are then analyzed. In the initial reactions, the tert-butoxy radical ((CH3)3CO⋅) is generated by the homolysis of the O–O bond in all cases. In comparison to the gaseous phase, where the majority of subsequent reactions involve the decomposition of (CH3)3CO⋅, the liquid phase exhibits additional H-abstraction reactions leading to the formation of tert-butanol. This can be attributed to a stronger interplay between the radicals in the liquid environment. The findings from this work are anticipated to contribute valuable data for enhancing the process safety of DTBP.

Emission Ratios and Diurnal Variability of Volatile Organic Compounds and Influence of Industrial Emissions in Two Texas Cities

Changing urban emission landscapes and increasing population make it imperative to understand the driving forces for air quality in growing urban areas. Recent field studies in an industrial area in Houston and a semiurban area in San Antonio reveal unique emission signatures for these two growing Texas cities. A comparison of benzene, toluene, xylenes, isoprene, and methyl ethyl ketone (MEK) was conducted for these two Texas locations and previous studies in other megacities. It was found that San Antonio had similar emission ratios as these megacities for benzene, toluene, and xylenes (1.10, 4.57, and 3.60 pptv ppbv−1 of CO, respectively), likely indicating a similar traffic emission source. Isoprene and MEK were of biogenic origin in San Antonio. However, analysis of emission ratios, diurnal trends, and comparison with emission inventories indicated that benzene, toluene, and MEK were likely associated with fugitive and stack emissions in the industrial corridor in Houston. Isoprene in Houston appeared to have mixed fugitive and biogenic sources in Houston, based on diurnal trends and emission ratio. The peak nighttime concentrations for benzene, toluene, xylene, isoprene, and MEK observed during the campaign were 66, 533, 21, 138, and 731 ppbv, respectively, in the Houston site. The emission ratio for xylenes (3.37 pptv ppbv−1 of CO) for the Houston site was similar to Paris, London, and Mexico City, despite emission inventories indicating high fugitive and stack emissions. The conditional probability function (CPF) analysis closely matched the direction of the industrial sources with the highest recorded emission levels as listed in the emission inventory for the Houston site. The estimated ozone production efficiency (OPE) for the industrial area in Houston indicated volatile organic compound (VOC)–limited conditions in the morning, which transitioned to nitrogen oxide (NOx)–limited conditions in the afternoon. Texas cities have complex emission scenarios, and future efforts to mitigate ozone and particulate matter may have to consider a variety of emission reduction strategies.

Cover Feature: Synthesis and Computational Investigation of Antioxidants Prepared by Oxidative Depolymerization of Lignin and Aldol Condensation of Aromatic Aldehydes (ChemSusChem 12/2023)

The Cover Feature shows novel antioxidants synthesized by oxidative depolymerization of lignin to form aromatic aldehydes followed by aldol condensation with methyl ethyl ketone (MEK). Aldol condensation was found to greatly improve the antioxidation ability of lignin depolymerized products. p-Hydroxybenzaldehyde, vanillin, and syringaldehyde as representative aromatic aldehydes were further employed for aldol condensation with MEK, resulting in successful synthesis of new antioxidants. The newly synthesized antioxidants could be used as a green additive of biodiesel to increase its oxidation stability. Density functional theoretical calculations confirmed that electron-donating groups such as methoxyl and conjugated side chains could effectively improve the antioxidation ability of the obtained antioxidants. More information can be found in the Research Article by D. Gao et al.

Liquid-Phase Oxidation of Butene–Butane Mixtures with N2O to Ketones and Aldehydes

Conventional methods for the production of ketones and aldehydes are usually quite complicated and require the use of specific catalysts. Thus, methyl ethyl ketone (MEK) is currently manufactured through a two-step catalytic process involving the hydration of n-butenes and dehydration of the formed alcohol. The non-catalytic oxidation of olefins with nitrous oxide (N2O) via the 1,3-dipolar cycloaddition mechanism opens a potential route for the direct synthesis of carbonyl compounds. In this work, the oxidation of the commercial butene–butane mixture (BBM) with N2O in the liquid phase at 220–260 °C and elevated pressure was studied using the gas chromatography, gas chromatography–mass spectrometry, and nuclear magnetic resonance analytical methods. It was shown that only butene isomers in BBM are selectively oxidized by N2O to yield ketones and aldehydes with a total selectivity of up to 86.6%, including MEK as the major product. During oxidation, alkyl-substituted cyclopropanes are also formed from butenes with a selectivity of up to 15%.

Morphology, microstructure evolution and properties of resin-bonded palm kernel and coconut shell grain-based abrasive grinding

This study examined the morphology and microstructural evolution of resin-bonded palm kernel and coconut shell grain-based abrasive grinding wheels and their physico-mechanical and tribological properties. Raw palm kernel shell (PKS) and coconut shell (CNS) samples were obtained, sorted, sun- and oven-dried, pulverised, and screened into fines of 250, 500 and 850 μm grain sizes, and blended at PKS to CNS mixing ratios of 1:0, 0:1, 1:2, 1:1 and 2:1, respectively. The blended grains, on a weight basis of the total aggregates, were bonded with 25 wt.% polyester resin and hardened and catalysed with 1.5 wt.% cobalt compound and methyl-ethyl ketone peroxide. The aggregates were moulded and compressed at a constant pressure of 18 MPa, ejected, and room-cured before being oven-cured to produce the wheels. The microstructural, water absorption, impact, flexural, hardness, and wear rate properties of the produced samples were evaluated. The properties studied were significantly influenced by grain sizes and mixing ratios of the PKS and CNS in the wheels. The least hardness value, 6.42 HRB, and wear rate, 0.44 mg/m were found in wheels produced from aggregates with pure PKS content with 850 and 250 μm grain sizes, respectively. The wheels' durability qualities suggest they could be used as abrasive grinding wheels, in particular, for wood cutting and finishing processes.

Structure and ferroelectric properties of P(VDF-TrFE) films prepared under different conditions — Effect of filtration of the copolymer solution

Vinylidene fluoride-trifluoroethylene copolymer films of molar ratio 70/30 with thickness of about 1 [Formula: see text]m have been deposited from solution in ethyl methyl ketone to a glass substrate with an aluminum electrode by spin coating. The solution has been filtrated through a PTFE membrane filter with pore size 0.2 [Formula: see text]m directly before spin coating or it has been used as is (unfiltrated). After deposition of a top electrode, the samples have been polarized by hysteresis loops with an electric field amplitude of about 100 V/[Formula: see text]m. In samples, annealed at temperature 145[Formula: see text]C for 3 h, a high remanent polarization of about 7.5 [Formula: see text]C/cm2has been achieved, without significant differences between samples fabricated of filtrated or unfiltrated solution. Spherulitic lamella are growing in films fabricated of filtrated solution when they are heated above the melting temperature to 159[Formula: see text]C for 3 min before the further annealing process at 145[Formula: see text]C. These films show substantially lower remanent polarization below 4 [Formula: see text]C/cm2. Pyroelectric images recorded with a pyroelectric laser scanning microscope show that the spherulites have very small pyroelectric activity, i.e., the spherulites consist of flat-on lamella. In contrast, no spherulitic lamella are growing in films fabricated of unfiltrated solution heated above the melting temperature, melted and annealed under the same conditions. An explanation for this observation is that filtrating changes the structure of the copolymer in solution from polymer coil to rod. Copolymer rods deposited on a substrate will crystallize in flat-on lamella when heated above the melting temperature, in contrast to copolymer coils which crystallize in edge-on lamella.

Synthesis and computational investigation of novel antioxidants prepared by oxidative depolymerization of lignin and aldol condensation of aromatic aldehydes.

Novel antioxidants were synthesized by CuSO4 catalyzed oxidative depolymerization of lignin to form aromatic aldehydes followed by aldol condensation with methyl ethyl ketone (MEK). Aldol condensation was found to greatly improve the antioxidation ability of lignin depolymerized products. Three lignin monomeric aromatic aldehydes, i.e. p-hydroxybenzaldehyde, vanillin, and syringaldehyde were further employed for aldol condensation with MEK, resulting in successful synthesis of new antioxidants, 1-(4-hydroxyphenyl)pent-1-en-3-one (HPPEO), 1-(4-hydroxy-3-methoxyphenyl)pent-1-en-3-one (HMPPEO) and 1-(4-hydroxy-3,5-dimethoxyphenyl)pent-1-en-3-one (HDMPPEO), respectively. Kinetic modeling illustrated that p-hydroxybenzaldehyde had the largest rate to react with MEK, followed by vanillin and then syringaldehyde, which was probably affected by the presence of methoxyl groups. Syringaldehyde derived product (HDMPPEO) displayed the best antioxidation ability. As revealed by density functional theoretical calculation, electron-donating group such as methoxyl group and conjugated side chain could effectively improve the antioxidation ability. Hydrogen atom transfer (HAT) mechanism was prone to occur in non-polar solvents while the sequential proton loss electron transfer (SPLET) mechanism was favored in polar solvents. This work thus can inspire new pathways for valorization of lignin to produce high value-added products.