The effects of propylene stored in pressurized spherical vessel were investigated using radiation & explosion modeling using PHAST 6.7 software in one of the refinery in Malaysia. The simulations were performed for various weather conditions with different leak scenarios in deterministic approach. Modeling approach was standard with current industry practice. Resulting events such as jet fire, vapor cloud explosion, boiling liquid evaporating vapor explosion effects shown in thermal radiation and overpressure towards targeted technical buildings. The effects of resulting jet fire flame length increase with release rate and explosion overpressure effects increase with degree of confinement and volume fraction respectively. The results were reviewed, interpreted against industry standard. The sensitivity cases show that, using lower inventory with moderate operating conditions will keep the consequence in acceptable region. This consequence analysis will form a basis for layout development, safety distance and fire zone segregation during conceptual design stage. Propylene storage conditions, layout arrangements and blast protections were recommended as part of preventive and mitigative measures.
We present a novel synthesis strategy termed delayed linker addition (DLA) to synthesize hybrid zeolitic-imidazolate frameworks containing unsubstituted imidazolate linkers (Im) with SOD topology (hereafter termed Im/ZIF-8). Im linker incorporation can create larger voids and apertures, which are important properties for gas storage and separation. To date, there have been only a handful of reports of Im linkers incorporated into ZIF-8 frameworks, typically requiring arduous and complicated post synthesis approaches. DLA, as reported here, is a simple one-step synthesis strategy allowing high incorporation of Im linker into the ZIF-8 framework while still retaining its SOD topology. We fabricated mixed-matrix membranes (MMMs) with 6FDA-DAM polymer and Im/ZIF-8 obtained via DLA as a filler. The Im/ZIF-8-containing MMMs showed excellent performance for both propylene/propane and n-butane/i-butane separation, displaying permeability and ideal selectivity well above the polymer upper bound. Moreover, highly detailed molecular simulations shed light to the aperture size and flexibility response of Im/ZIF-8 and its improved diffusivity as compared to ZIF-8.
A chemical modifier (acrylic acid) was used to improve the thermal properties of polypropylene/ ethylene propylene diene terpolymer/calcium carbonate (PP/EPDM/CaCO3) composites. Treated
and untreated PP/EPDM composites were filled by CaCO3 at 0, 20 and 40% wt. The composites
were prepared using Z-blade mixer machine at 180oC and 50 rpm of rotor speed. Thermogravimetric
analysis (TGA) and differential scanning calorimetry (DSC) methods were used to analyze the thermal properties of the composites. Thermogravimetric analysis indicated that the total weight loss of PP/EPDM/CaCO3 composites decreased with the increasing filler loading for the treated and untreated composites. Meanwhile, the presence of acrylic acid was found to have increased the thermal stability and crystallinity of PP/EPDM/CaCO3
.
Herein, an efficient epoxidation of 1-nonene is described. In a simple epoxidation system, commercially available Novozym 435, an immobilized Candida antarctica lipase B, and hydrogen peroxide (H(2)O(2)) were utilized to facilitate the in situ oxidation of phenylacetic acid to the corresponding peroxy acid which then reacted with 1-nonene to give 1-nonene oxide with high yield and selectivity. The aliphatic terminal alkene was epoxidised efficiently in chloroform to give an excellent yield (97%-99%) under the optimum reaction conditions, including temperature (35 °C), initial H(2)O(2) concentration (30%), H(2)O(2) amount (4.4 mmol), H(2)O(2) addition rate (one step), acid amount (8.8 mmol), and stirring speed (250 rpm). Interestingly, the enzyme was stable under the single-step addition of H(2)O(2) with a catalytic activity of 190.0 Ug-1. The entire epoxidation process was carried out within 12 h using a conventional water bath shaker.
The first enantioselective synthesis of (-)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (-)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.
INTRODUCTION: Trikatu is composed of dried fruits of Piper nigrum L and Piper retrofractum Vahl, and dried rhizomes of Zingiber officinale R. Although this preparation has been used to relieve pruritis, pain, and inflammation for a long time, there is no clinical evidence to confirm its efficacy and safety. Therefore, we performed a double-blind, within person-randomized controlled study of 30 healthy volunteers to determine efficacy and safety of topical Trikatu on mosquito bite reactions.
METHODS: All subjects were bitten by Aedes aegypti laboratory mosquitoes on their forearms and they were randomly assigned arms to apply either Trikatu or reference product on the mosquito bite papule. The main outcome was the difference of papule size reduction at 30 min, measured by a caliper, between the Trikatu and reference arms. Pruritis, redness, pain, and patient satisfaction were assessed at 15, 30, 60, 180, and 360 min as secondary outcomes.
RESULTS: There were no significant differences between treatment and reference arms on any outcome at any time of measurement.
CONCLUSION: Trikatu did not show additional effects for relieving mosquito bite reaction as compared with the reference product containing camphor, menthol, and eucalyptus. For further study, it is very important to consider a proper selection of subjects, comparator product, and concentration of extract when Trikatu preparation is investigated.
KEYWORDS: Eucalyptus oil; Mosquito bite; Mosquito bite symptoms; Papule size reduction; Trikatu preparation
Geometric isomerization can expand the scope of biological activities of natural products. The observed chemical diversity among the pseurotin-type fungal secondary metabolites is in part generated by a trans to cis isomerization of an olefin. In vitro characterizations of pseurotin biosynthetic enzymes revealed that the glutathione S-transferase PsoE requires participation of the bifunctional C-methyltransferase/epoxidase PsoF to complete the trans to cis isomerization of the pathway intermediate presynerazol. The crystal structure of the PsoE/glutathione/presynerazol complex indicated stereospecific glutathione-presynerazol conjugate formation is the principal function of PsoE. Moreover, PsoF was identified to have an additional, unexpected oxidative isomerase activity, thus making it a trifunctional enzyme which is key to the complexity generation in pseurotin biosynthesis. Through the study, we identified a novel mechanism of accomplishing a seemingly simple trans to cis isomerization reaction.
The chlorine radical is a potent atmospheric oxidant, capable of perturbing tropospheric oxidative cycles normally controlled by the hydroxyl radical. Significantly faster reaction rates allow chlorine radicals to expedite oxidation of hydrocarbons, including methane, and in polluted environments, to enhance ozone production. Here we present evidence, from the CARIBIC airborne dataset, for extensive chlorine radical chemistry associated with Asian pollution outflow, from airborne observations made over the Malaysian Peninsula in winter. This region is known for persistent convection that regularly delivers surface air to higher altitudes and serves as a major transport pathway into the stratosphere. Oxidant ratios inferred from hydrocarbon relationships show that chlorine radicals were regionally more important than hydroxyl radicals for alkane oxidation and were also important for methane and alkene oxidation (>10%). Our observations reveal pollution-related chlorine chemistry that is both widespread and recurrent, and has implications for tropospheric oxidizing capacity, stratospheric composition and ozone chemistry.
The Prins cyclization of styrene (SE) with paraformaldehyde (PFCHO) was conducted with mesoporous ZnAlMCM-41 catalysts for the synthesis of 4-phenyl-1,3-dioxane (4-PDO) using a liquid phase heterogeneous catalytic method. For a comparison study, the Prins cyclization reaction was also conducted over different nanoporous catalysts, e.g. mesoporous solid acid catalysts, AlMCM-41(21) and ZnMCM-41(21), and microporous catalysts, USY, Hβ, HZSM-5, and H-mordenite. The recyclable mesoporous ZnAlMCM-41 catalysts were reused in this reaction to evaluate their catalytic stabilities. Since ZnAlMCM-41(75) has higher catalytic activity than other solid acid catalysts, washed ZnAlMCM-41(75)/W-ZnAlMCM-41(75) was prepared using an efficient chemical treatment method and used with various reaction parameters to find an optimal parameter for the highly selective synthesis of 4-PDO. W-ZnAlMCM-41(75) was also used in the Prins cyclization of olefins with PFCHO and formalin (FN, 37% aqueous solution of formaldehyde (FCHO)) under different reaction conditions to obtain 1,3-dioxanes, which are widely used as solvents or intermediates in organic synthesis. Based on the nature of catalysts used under different reaction conditions, a reasonable plausible reaction mechanism for the Prins cyclization of SE with PFCHO is proposed. Notably, it can be seen from the catalytic results of all catalysts that the W-ZnAlMCM-41(75) catalyst has higher 4-PDO selectivity with exceptional catalytic activity than other microporous and mesoporous catalysts.
Thermodynamic chemical equilibrium analysis using, total Gibbs energy minimization method, was carried out for methane oxidation to higher hydrocarbons. For a large methane conversion and a high selectivity to higher hydrocarbons, the system temperature and oxygen concentration played a vital role, whereas, the system pressure only slightly influenced the two variables. Numerical results showed that the conversion of methane increased with the concentration of oxygen and reaction temperature, but it decreased with pressure. Nevertheless, the presence of oxygen suppressed the formation of higher hydrocarbons which mostly consisted of aromatics, but enhanced the formation of hydrogen. As the system pressure increased, the aromatics, olefins and hydrogen yields diminished, but the paraffin yield improved. Carbon monoxide seemed to be the major oxygen-containing equilibrium product from methane oxidation, whilst almost no H2O, CH3OH and HCOH were detected although traces amount of carbon dioxide were formed at relatively lower temperature and higher pressure. The total Gibbs energy minimization method is useful to theoretically analyze the feasibility of methane conversion to higher hydrocarbons and syngas at the selected temperature and pressure.
Polymeric materials such as polypropylene (PP), polyethylene (PE) and ethylene propylene diene monomer (EPDM) are widely used as insulators for cable applications. We investigated the effect of alumina trihydrate (ATH) loading on the mechanical properties of PP/EPDM blend. Preliminary study showed that PP/EPDM (60:40) was the optimum composition. ATH filled PP/EPDM composites was prepared by using twin screw extruder. In this study, the tensile properties and hardness of the composites were evaluated. The tensile modulus and hardness increased while elongation at break and tensile strength decreased with increasing ATH content. Scanning electron microscope was used to study the morphology of ATH in PP/EPDM blend.
50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO) catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future.
Propylene is one type of plastic that is widely used in our everyday life. This study focuses on the identification and justification of the optimum process parameters for polypropylene production in a novel pilot plant based fluidized bed reactor. This first-of-its-kind statistical modeling with experimental validation for the process parameters of polypropylene production was conducted by applying ANNOVA (Analysis of variance) method to Response Surface Methodology (RSM). Three important process variables i.e., reaction temperature, system pressure and hydrogen percentage were considered as the important input factors for the polypropylene production in the analysis performed. In order to examine the effect of process parameters and their interactions, the ANOVA method was utilized among a range of other statistical diagnostic tools such as the correlation between actual and predicted values, the residuals and predicted response, outlier t plot, 3D response surface and contour analysis plots. The statistical analysis showed that the proposed quadratic model had a good fit with the experimental results. At optimum conditions with temperature of 75 °C, system pressure of 25 bar and hydrogen percentage of 2%, the highest polypropylene production obtained is 5.82% per pass. Hence it is concluded that the developed experimental design and proposed model can be successfully employed with over a 95% confidence level for optimum polypropylene production in a fluidized bed catalytic reactor (FBCR).
Here, we focused on a simple enzymatic epoxidation of alkenes using lipase and phenylacetic acid. The immobilised Candida antarctica lipase B, Novozym 435 was used to catalyse the formation of peroxy acid instantly from hydrogen peroxide (H2O2) and phenylacetic acid. The peroxy phenylacetic acid generated was then utilised directly for in situ oxidation of alkenes. A variety of alkenes were oxidised with this system, resulting in 75-99% yield of the respective epoxides. On the other hand, the phenylacetic acid was recovered from the reaction media and reused for more epoxidation. Interestingly, the waste phenylacetic acid had the ability to be reused for epoxidation of the 1-nonene to 1-nonene oxide, giving an excellent yield of 90%.
Introduction: Accelerants and fabrics are commonly used to spread fire attributable to their highly flammable prop- erties. Hence, having the ability to discriminate the different types of accelerants on various types of fabrics after fire and/or arson using the non-destructive Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spec- troscopy coupled with chemometric techniques appears forensically relevant. Methods: Six types of fabrics viz. cotton, wool, silk, rayon, satin, and polyester, were burnt completely with RON95 and RON97 gasoline as well as diesel. Subsequently, the samples were analyzed by ATR-FTIR spectroscopy followed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) for discriminating the different types of accelerants on such burned fabrics. Results: RON95 showed the fastest rate of burning on all fabric types. Results also revealed that while wool had the slowest burning rate for all the three different accelerants, polyester, cotton, and satin demon- strated the highest rate of burning in RON95, RON97, and diesel, respectively. FTIR spectra revealed the presence of alkane, alcohol, alkene, alkyne, aromatic, and amine compounds for all fabrics. The two dimensional PCA (PC1 versus PC2) demonstrated 71% of variance and it was improved by cross-validation through the three dimensional LDA technique with correct classification of 77.8%. Conclusion: ATR-FTIR spectroscopy coupled with chemometric techniques had enabled identification of the functional groups, as well as statistically supported discrimination of the different accelerants, a matter of relevance in forensic fire and arson investigations.
The palladium metal catalysed Heck reaction of 4-iodoanisole with styrene or methyl acrylate has been studied in a continuous plug flow reactor (PFR) using supercritical carbon dioxide (scCO2) as the solvent, with THF and methanol as modifiers. The catalyst was 2% palladium on silica and the base was diisopropylethylamine due to its solubility in the reaction solvent. No phosphine co-catalysts were used so the work-up procedure was simplified and the green credentials of the reaction were enhanced. The reactions were studied as a function of temperature, pressure and flow rate and in the case of the reaction with styrene compared against a standard, stirred autoclave reaction. Conversion was determined and, in the case of the reaction with styrene, the isomeric product distribution was monitored by GC. In the case of the reaction with methyl acrylate the reactor was scaled from a 1.0 mm to 3.9 mm internal diameter and the conversion and turnover frequency determined. The results show that the Heck reaction can be effectively performed in scCO2 under continuous flow conditions with a palladium metal, phosphine-free catalyst, but care must be taken when selecting the reaction temperature in order to ensure the appropriate isomer distribution is achieved. Higher reaction temperatures were found to enhance formation of the branched terminal alkene isomer as opposed to the linear trans-isomer.
Microplastics receive global attention due to its strong presence in marine and freshwater organisms. Yet, there are few studies on estuarine organisms. This baseline study evaluates the abundance and distribution of microplastics in the gastropods of a tropical estuary in Selangor, Malaysia. The abundance of microplastics ranged from 0.50 to 1.75 particles/g or from 0.25 to 0.88 particles/individual. The variation in microplastic distribution between the upper and lower estuary indicates that the microplastics originated from the urbanised area of the Klang River estuary. Microplastic sizes varied from 30 to 1850 μm, with the majority being between 300 and 1000 μm (57%). Characteristics of microplastics were dominant for fibres (91%) with black colour (50%). Polyethylene-propylene-diene (PE-PDM) and polyester were the main polymer materials. Assessing the contamination of gastropods by microplastics provides insight into the possibility of utilising gastropods as bioindicators that could be used for monitoring and baseline studies.
This study focuses on the mechanical effect of different composition of polymer blend. Polymer blend of high density polyethylene (HDPE) and ethylene propylene rubber (EPR) were selected and varied by three different compositions which are 70:30, 50:50 and 30:70. HDPE-EPR blend is believed to be the best material for sole shoe. In which, HDPE has good flexibility while, EPR can maintain optimum performance at high and low temperature as well as provide better gripping characteristic that suits for insole and outsole sport shoe. On the other hand, the time efficiency of electron beam radiation on these polymer blends helps in improving the croslinking of HDPE-EPR blend. The aim of this paper was to find the optimum composition of electron beam irradiated polymer blends for sole shoes especially in sports application. These irradiated polymer blends were produced by melt blending, underwent compression moulding and then were irradiated by electron beam at 100 kGy/s. Mechanical test of tensile and hardness test were investigated and the morphology of the failure fracture was analysed by field emission scanning electron microscopy (FESEM). The polymer blend with 70% of HDPE and 30% of EPR showed the optimum result of tensile strength, tensile modulus and hardness as well as ductile failure image.
Successful activation of the pyranonigrin biosynthetic gene cluster and gene knockout in Aspergillus niger plus in vivo and in vitro assays led to isolation of six new products, including a spiro cyclobutane-containing dimeric compound, which served as the basis for the proposed comprehensive pyranonigrin biosynthetic pathway. Two redox enzymes are key to forming the characteristic fused γ-pyrone core, and a protease homologue performs the exo-methylene formation.
Acetylmelodorinol, chrysin and polycarpol, together with benzoic acid, benzoquinone and stigmasterol were isolated from the leaves of Mitrella kentii (Bl.) Miq. The compounds were evaluated for their ability to inhibit prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) production in human whole blood using a radioimmunoassay technique. Their inhibitory effect on platelet activating factor (PAF) receptor binding to rabbit platelet was determined using ³H-PAF as a ligand. Among the compounds tested, chrysin showed a strong dose-dependent inhibitory activity on PGE(2) production (IC₅₀ value of 25.5 µM), which might be due to direct inhibition of cyclooxygenase-2 (COX-2) enzymatic activity. Polycarpol, acetylmelodorinol and stigmasterol exhibited significant and concentration-dependent inhibitory effects on TXB₂ production with IC₅₀ values of 15.6, 19.1 and 19.4 µM, respectively, suggesting that they strongly inhibited COX-1 activity. Polycarpol and acetylmelodorinol showed strong dose-dependent inhibitory effects on PAF receptor binding with IC₅₀ values of 24.3 and 24.5 µM, respectively.