Study of pyrolysis kinetic of green corn husk

In this paper, it was suggested the use of green corn husk, which is a biomass from agro-industry, as an alternative source of energy through its pyrolysis. Green corn husk characterization was done through immediate and elemental analysis of its components: cellulose, hemicelluloses, and lignin. It was also measured its higher calorific value. The pyrolysis study of green corn husk was done by the isoconversion and the Master plots method. Thermogravimetric plots were obtained at heating rates of 5, 10, 15, and 20 °C min^?1. The pyrolysis kinetics parameters were studied through the Flynn–Wall–Ozawa (FWO), Kissinger, and Friedman models. The Master plots method was used to determine the pyrolysis reaction order. The results of the reaction energy activation were found to be in the range 105.21–157.46 kJ mol^?1 by the FWO method, 150.50 kJ mol^?1 by the Kissinger method, and ranged 120.66–163.81 kJ mol^?1 by the Friedman method. The Master plots method showed a three-way-transport diffusional kinetics for the biomass de-volatilization process. The higher calorific value found for green corn husk was 16.14 MJ kg^?1. The simulation showed correlation between the experimental data and the proposed model for conversion values up to 0.8.

     

Electrochemical and associated techniques for the study of the inclusion complexes of thymol and β-cyclodextrin and its interaction with DNA

Journal of Solid State Electrochemistry - Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging...     

Photocatalyzed Intramolecular [2+2] Cycloaddition of N-Alkyl-N-(2-(1-arylvinyl)aryl)cinnamamides

N-Alkyl-N-(2-(1-arylvinyl)aryl)cinnamamides are converted into natural product inspired scaffolds via iridium photocatalyzed intramolecular [2+2] photocycloaddition. The protocol has a broad substrate scope, whilst operating under mild reaction conditions. Tethering four components forming a trisubstituted cyclobutane core builds rapidly high molecular complexity. Our approach allows the design and synthesis of a variety of tetrahydrocyclobuta[c]quinolin-3(1H)-ones, in yields ranging between 20–99 %, and with excellent regio- and diastereoselectivity. Moreover, it was demonstrated that the intramolecular [2+2]-cycloaddition of 1,7-enynes—after fragmentation of the cyclobutane ring—leads to enyne-metathesis-like products.     

Selective Transformation of Norbornadiene into Functionalized Azaheterocycles and β-Amino Esters with Stereo- and Regiocontrol

Novel functionalized azaheterocycles with multiple chiral centers have been accessed from readily available norbornene β-amino acids or β-lactams across a stereocontrolled synthetic route, based on ring-opening metathesis (ROM) of the staring unsaturated bicyclic amino esters, followed by selective cyclization through ring-closing metathesis (RCM). The RCM transformations have been studied under various experimental conditions to assess the scope of conversion, catalyst, yield, and substrate influence. The structure of the starting norbornene β-amino acids predetermined the structure of the new azaheterocycles, and the developed synthetic route took place with the conservation of the configuration of the chiral centers.     

Study of the cyclen derivative 2-[1,4,7,10-tetraazacyclododecan-1-yl]-ethanethiol and its complexation behaviour towards d-transition metal ions

The compound 2-[1,4,7,10-tetraazacyclododecan-1-yl]-ethanethiol (L2) has been synthesized and characterized by multinuclear NMR spectroscopy and mass spectrometry. Its thiol-protected precursor L1 has also been isolated and characterized, including by X-ray structural analysis. The protonation constants of L2 were determined by potentiometric methods at 25.0 °C and 0.10 mol dm⁻³ KNO₃ ionic strength. ¹³C NMR studies and 2D NMR spectra recorded at different pD values have been used to analyse its protonation scheme. Stability constants of L2 with Cu²⁺, Zn²⁺ and Cd²⁺ were also determined by potentiometry, and the Zn(II) and Cu(II) complexes were studied in solution by NMR, UV–Vis, and EPR spectroscopies. The pM values (pH 7.4) calculated for the metal complexes of L2 are higher than the corresponding values found for cyclen and cyclam, but the selectivity of L2 for Cu²⁺ is low.     

Evaluation of three ionisation modes for the analysis of chlorinated paraffins by gas chromatography/ion-trap mass spectrometry

The applicability of three ionisation modes to the analysis of short-chain chlorinated paraffins (SCCPs) using gas chromatography coupled with mass spectrometry (GC/MS) was evaluated. MS conditions for electron ionisation (EI), positive chemical ionisation (PCI) and electron-capture negative ionisation (ECNI) were optimised using commercially available individual tetra-, penta- and hexachlorodecanes. In addition, mass spectra were studied and fragmentation pathways were proposed for each individual congener. Different fragment ions were evaluated for quantification, and ECNI-MS using [HCl2](-) and [Cl2](-*) ions was selected for the determination of SCCPs. Quality parameters (repeatability, limits of detection and calibration range) were established for the proposed method, which was then applied to the analysis of SCCPs in river sediments.     

Nonlinear Couette Flow in a Low Density Granular Gas

A model kinetic equation is solved exactly for a special stationary state describing nonlinear Couette flow in a low density system of inelastic spheres. The hydrodynamic fields, heat and momentum fluxes, and the phase space distribution function are determined explicitly. The results apply for conditions such that viscous heating dominates collisional cooling, including large gradients far from the reference homogeneous cooling state. Explicit expressions for the generalized transport coefficients (e.g., viscosity and thermal conductivity) are obtained as nonlinear functions of the coefficient of normal restitution and the shear rate. These exact results for the model kinetic equation are also shown to be good approximations to the corresponding state for the Boltzmann equation via comparison with direct Monte Carlo simulation for the latter.     

New versatile organyltellurium(IV) halides: Synthesis and X-ray structural features of the telluronium tellurolate salts [PhTe(CH3)2]2[TeX6] (X = Cl, Br) and [Ph3Te][PhTeX4] (X = Cl, Br, I)

TeX₄ (X = Cl, Br) react in HCl/HBr with [Ph(CH₃)₂Te]X (X = Cl, Br) to give [PhTe(CH₃)₂]₂[TeCl₆] (1) and [PhTe(CH₃)₂]₂[TeBr₆] (2). The reaction of PhTeX₃ (X = Cl, Br, I) in cooled methanol with [(Ph)₃Te]X (X = Cl, Br, I) leads to [Ph₃Te][PhTeCl₄] (3), [Ph₃Te][PhTeBr₄] (4) and [Ph₃Te][PhTeI₄] (5). In the lattices of the telluronium tellurolate salts 1 and 2, octahedral TeCl₆ and TeBr₆ dianions are linked by telluronium cations through Te?Cl and Te?Br secondary bonds, attaining bidimensional (1) and three-dimensional (2) assemblies. The complexes 3, 4 and 5 show two kinds of Te?halogen secondary interactions: the anion-anion interactions, which form centrosymmetric dimers, and two identical sets of three telluronium-tellurolate interactions, which accomplish the centrosymmetric fundamental moiety of the supramolecular arrays of the three compounds, with the tellurium atoms attaining distorted octahedral geometries. Also phenyl C-H?halogen secondary interactions are structure forming forces in the crystalline structures of compounds 3, 4 and 5.     

Preparation of PMMA Nanoparticles Loaded with Benzophenone-3 through Miniemulsion Polymerization

Summary: The present paper analyzes the production of poly(methyl methacrylate) – PMMA – nanoparticles loaded with benzophenone-3 through miniemulsion polymerization. The obtained product is homogeneous and stable, allowing for preparation of photo-protective formulations. It is observed in particular that bezophenone-3 interacts with the reacting system, promoting the growth of the PMMA chains produced in miniemulsion.     

Application of high temperature high resolution gas chromatography to paraffinic deposits in petroleum production pipelines

HTHRGC was found essential for optimizing representative preparation of high molecular weight samples and enabling fingerprinting of heavy fractions of crude oils and associated paraffinic deposits in production pipelines. Laboratory experiments aimed at simulating the process of paraffin deposition could also be easily evaluated. A comparative investigation of the performance of cold on-column and SPI (PTV type) injectors, in conjunction with high temperature capillary columns, for analysis of high molecular weight fractions, was also conducted during the course of this work.