Study of fuel insolubles: Formation conditions and characterization of copper compounds

The solids formed in the systems containing copper in different oxidation states, in the presence and absence of hexanoic acid and dodecanethiol, together and separately, at room temperature, were studied. The experiments were performed in a mineral oil matrix, free of sulfur compounds and metals; a diesel oil matrix; and the reagents alone, without any matrix. The deposits formed were analyzed by elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and total copper by inductively coupled plasma-optical emission spectrometry (ICP-OES), for their identification and determination of the probable structures. In samples containing both hexanoic acid and dodecanethiol, when there is copper(I), anhydrous copper(II) hexanoate is preferentially formed, but in samples of copper(II), copper(II) mercaptate is formed first. In samples of metallic copper in mineral oil matrix, no deposit formations occur. In all cases in which deposits were formed, they were the same as in diesel oil matrix.     

Preparation of metallic silver from Ag2S slurry by direct hydrogen reduction under hydrothermal conditions

Metallic silver has been prepared by direct hydrogen reduction of Ag₂S in basic slurry under hydrothermal conditions. The XRD pattern and SEM micrographs of the reaction product are given. Metallic silver was predominant in the reduction product obtained by using ZnO as additive and PdCl₂ as catalyst at 220 °C, pH 12.0 and 2–3 MPa of partial hydrogen pressure for 4 h.     

The Cold Chain,one link in Canada’s food safety initiatives

The Cold Chain has always played an important role in food safety within the global market. The Canadian government has recognized it has an important role in the food continuum. In partnership with industry, national voluntary enhanced food safety systems, based on Codex Alimentarius (HACCP) principles, are being developed within Canada. These efforts will contribute towards food safety and will build confidence in foodstuffs grown, prepared and sold at all levels of trade and abroad.     

Efficient synthesis of benzophenone derivatives in Lewis acid ionic liquids

Benzophenone and its derivatives were prepared via Friedel–Crafts acylation reactions using ionic liquids (ILs) of BmimCl–FeCl₃, BmimCl–AlCl₃ and BmimCl–ZnCl₂ as dual catalyst–solvent. Among them, BmimCl–FeCl₃ showed much higher catalytic activity than that observed for the other two ILs, and in conventional organic solvents. In these reaction systems, good to excellent yields (up to 97%) of acylation products were obtained in a short reaction time. This method features high yield, a simple product isolation procedure, ILs reusability and reduced waste discharge, thus rendering this catalytic system both efficient and environmentally friendly.     

A QM/MM study of the catalytic mechanism of aspartate ammonia lyase

Aspartate ammonia lyase (Asp) is one of three types of ammonia lyases specific for aspartate or its derivatives as substrates, which catalyzes the reversible reaction of l-aspartate to yield fumarate and ammonia. In this paper, the catalytic mechanism of Asp has been studied by using combined quantum-mechanical/molecular-mechanical (QM/MM) approach. The calculation results indicate that the overall reaction only contains two elementary steps. The first step is the abstraction of C_β proton of l-aspartate by Ser318, which is calculated to be rate limiting. The second step is the cleavage of C_αN bond of l-aspartate to form fumarate and ammonia. Ser318 functions as the catalytic base, whereas His188 is a dispensable residue, but its protonation state can influence the active site structure and the existing form of leaving amino group, thereby influences the activity of the enzyme, which can well explain the pH dependence of enzymatic activity. Mutation of His188 to Ala only changes the active site structure and slightly elongates the distance of C_β proton of substrate with Ser318, causing the enzyme to remain significant but reduced activity.     

Synthesis and swelling properties of poly[acrylamide-co-(crotonic acid)] superabsorbents

Superabsorbent polymers of acrylamide (AAm)/crotonic acid (CA) were synthesized by foamed polymerization in an aqueous solution of AAm with CA as a comonomer, initiated by an initiator couple of ammonium persulfate and N,N,N′N′-tetramethylethylenediamine. A crosslinking agent N,N′-methylenebisacrylamide, a foaming agent sodium bicarbonate, and a foam stabilizer, a triblock copolymer of polyoxyethylene/polyoxypropylene/polyoxyethylene, were used in the polymerization. The influences of the relative contents of CA, crosslinking agent, and initiator, on the swelling properties of the superabsorbent polymer systems were examined. The superabsorbent polymer synthesized with an AAm/CA ratio of 98:2 by mole, 0.5 wt.% of N,N′-methylenebisacrylamide and 1 wt.% of ammonium persulfate at 250 rpm and 50 °C for 30 min of polymerization time produced the highest water absorption of 211 ± 9 times its dried weight and could absorb water up to 162 ± 4 g g⁻¹ of the dry copolymer within 10 min. The electrochemical reaction for acrylamide–crotonic acid polymerization was investigated by cyclic voltammetry. The anodic current indicated that acrylamide acting as an electron donor whereas crotonic acid performed as an electron receiver, then providing the cathodic current. The diffusion of water into the superabsorbent polymer was non-Fickian (case II and anomalous). Acrylamide–crotonic acid superabsorbents containing various crosslinker concentrations had a water swelling in the range of 79–289 g g⁻¹. The diffusion coefficients varied between 6.9 × 10⁻⁹ and 5.1 × 10⁻⁸ cm² s⁻¹. Adsorption of the basic dye by the superabsorbent was a monolayer evaluated by the Langmuir isotherm. The superabsorbents can thus be used to adsorb cationic dyes in textile industry.     

Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion,metal area and hydrogenation activity

A series of palladium supported on activated carbon catalysts, with Pd varying from 0.5 to 6.0 wt%, were prepared via wet impregnation method using PdCl₂ · xH₂O as a precursor salt. The dried samples were further reduced at 573 K in hydrogen and characterized by CO adsorption at room temperature in order to determine the dispersion, metal area and particle size. The catalysts were tested for vapour phase phenol hydrogenation in a fixed-bed all glass micro-reactor at a reaction temperature of 453 K under normal atmospheric pressure. The decrease in metal surface area as well as dispersion with corresponding increase in turn-over frequency (TOF) against palladium loadings suggest the unusual inverse relationship that exist between Pd dispersion and phenol hydrogenation activity over Pd/carbon catalysts. The stability of TOF at larger crystallite size indicates that phenol hydrogenation is less sensitive reaction especially beyond 3 wt% of Pd content. It is evident from the results that structural properties of the catalysts strongly influence the availability of Pd atoms on the surface for CO chemisorption and hence for phenol hydrogenation. A comparison between selectivity and product yield of the reaction against overall phenol conversion indicates that changes in reaction selectivity for cyclohexanone or cyclohexanol is independent of phenol conversion level and either of the product is not formed at the cost of another. The stability of the catalysts with reaction time suggests that coke formation on the surface of the catalyst is less significant and the formation of cyclohexanone remains almost total even at higher reaction temperatures.     

A software tool for translating deterministic model results into probabilistic assessments of water quality standard compliance

Most assessments of whether a water body will comply with pollutant standards after modification of land use, loading, or climate change are based on the results of deterministic simulation models. These models, including those used to support the United States Environmental Protection Agency (USEPA) total maximum daily load (TMDL) program, typically do not account for common sources of assessment uncertainty. Instead, model results are typically represented by a time series of predicted pollutant concentration values or the parameters of a frequency-based distribution of these values over a specified time period. The rate of exceedance of relevant pollutant limits is then assessed directly from this time series or distribution to determine standard compliance. In this way, sampling and analysis-based variability and model uncertainty are typically ignored, although they may substantially influence the probability of non-compliance. To help address this problem, we introduce ProVAsT (Probabilistic Water Quality Standard Violation Assessment Tool), a software tool encoded in the graphical model-based package Analytica^®. Here, we present a version of ProVAsT which translates model-predicted in situ fecal indicator bacteria (FIB) pollutant concentrations into the expected frequency of water quality standard violations and provides a Bayesian measure of the degree of confidence in this assessment. We call this version ProVAsT-FIB. Along with inputting their own simulation model results, users can specify the particular water quality analysis methods employed (e.g. the analytic procedure used and the number and volume of sample aliquots) as well as the numeric limits pertaining to local water quality standards. It is our hope that ProVAsT will encourage the rational consideration of uncertainty and variability in water quality assessments by reducing the burden of complex statistical calculations.     

Fabrication and characterization of direct patterning ferroelectric Sr0.9Bi2.1Ta2O9 thin films by photosensitive sol–gel solution

Photosensitive ferroelectric Sr_0.9Bi_2.1Ta₂O₉ (SBT) precursor solutions were synthesized using strontium ethoxide chelated with ethylacetoacetone, tetramethylheptanedionato bismuth and tantalum ethoxide chelated with ethylacetoacetone. SBT thin films with 200 nm thickness were prepared on Pt/TiO₂/SiO₂/Si substrates using the spin coating method. As UV light exposure time to the SBT thin film increased, the intensity of the UV absorption peak of the metal β-diketonate decreased due to metal–oxygen–metal bond formation, which led to decreased solubility of SBT thin film. The solubility difference enabled direct patterning of thin films that had ferroelectric properties. The ferroelectric properties of the UV irradiated SBT thin films were superior to those of the non-UV irradiated films. Pr/Ps and 2 Pr values (at 3 V) of SBT thin films improved approximately 8% and 5%, respectively, with UV irradiation.     

Reaction mechanism and free energy profile for acylation of Candida Antarctica lipase B with methylcaprylate and acetylcholine: Density functional theory calculations

Candida Antarctica lipase B (CALB), a specific enzyme to catalyze the hydrolysis of esters, can be a good candidate for acetylcholine (ACh) hydrolysis instead of acetylcholinesterase. The catalytic mechanism of the CALB acylation, as the first stage in the hydrolysis reaction, with ACh and methylcaprylate (MEC) has been examined by using density functional theory technique. The significant emphasis of this article is on the free energy barriers for the acylation step of hydrolysis reactions. Computed free energy barriers of the first step are 9.2 and 15.9 kcal mol⁻¹, but for the second step are 7.9 and 11.6 kcal mol⁻¹ for MEC and ACh respectively. Activation free energies are in the comparable and acceptable range and imply both of two reactions are theoretically possible. The stability role of the adjacent amino acids was examined by using two applied tools. It is exposed that the oxyanion hole residues decrease energy barriers by stabilizing the transition state structures.