Immobilized lipase-catalysed esterification and transesterification reactions in non-aqueous media for the synthesis of tetrahydrofurfuryl butyrate: comparison and kinetic modeling

Immobilized lipase-catalyzed synthesis of tetrahydrofurfuryl butyrate is reported in this paper. Esterification and transesterification of tetrahydrofurfuryl alcohol (THFA) with butyric acid (BA) and transesterification with ethyl butyrate (EB) to prepare tetrahydrofurfuryl butyrate (THFB) were studied systematically including kinetic modeling. A series of immobilized lipases such as Novozym 435, Lipozyme IM 20, Pseudomonas species lipase on toyonite (PSL/Toyo), Candida rugosa lipase (CRL) on polypropylene, CRL on egg shells and CRL on celite were screened to establish that Novozym 435 was the best catalyst for both esterification and transesterification at 30°C. The effects of various parameters on reaction rates were studied in detail for both reactions with Novozym 435. The ping-pong bi-bi mechanism with inhibition by the substrate THFA fits the data for esterification whereas the ping-pong bi-bi mechanism with inhibition by both the reactants (THFA and EB) and both the products (THFB and ethanol) is valid for the transesterification reaction. The kinetic parameters deduced from these models were used to simulate the conversions, which are in good agreement with the experimental values. Since transesterification suffers inhibition by both the substrates and products, esterification is a better method compared to transesterification.     

Structural Transformation in Cubic Zirconia

The structure of CaO-stabilized cubic zirconia has been investigated by X-ray diffraction at high temperatures and pressures up to 1000°C and ∼35 GPa, using a diamond-anvil cell interfaced with aYAG laser heating system. At ∼1000°C and 15 GPa, the cubic phase transforms directly into an orthorhombic phase with the PbCl₂ structure. This high-pressure phase is quenchable. The zero-pressure lattice parameters are a=0.3327±0.0004 nm, b=0.5566±0.0003 nm, and c =0.6487±0.0005 nm, the volume change being 10.5%.     

Effect of environmental stress on the mechanical properties of surface treated fly‐ash/polyester particulate composite

Fly‐ash (FA) was surface treated with silane coupling agents (CA) vinyltriethoxy silane and aminopropyltrimethoxysilane. Fly‐ash/polyester (FA/GPR) and surface treated fly‐ash/polyester (FA/CA/GPR) particulate composites were made. The composites were exposed to various adverse environmental conditions such as water, boiling water, salt water, acid, alkali, toluene, weather and freezing–thawing cycles for 30 days. The mechanical properties, ie tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus, compressive strength, impact strength and hardness of FA/GPR and FA/CA/GPR were studied before and after exposure to adverse environmental conditions. The results indicate that the mechanical properties of FA/GPR composites are improved by surface treatment of FA and that their resistance to the various environmental stresses is also enhanced substantially by surface treatment. © 2002 Society of Chemical Industry     

Vertical motion of a sphere in an electrically conducting,stratified, diffusive medium

Summary The vertical (upwards) flow of an incompressible, Newtonian, viscous, stratified, diffusive, electrically conducting fluid embedded with a uniform magnetic field that is applied in the vertical direction, past a non-conducting sphere is considered. Quasisteady approximation is made allowing for a time dependent buoyancy force. Method of matched asymptotic expansions is employed to obtain the drag exerted on the sphere, for small values of a stratification parameter such that 1,R _e ^1/3, ^–1/3,P _e ^2/3 andR _m =O(^2/3). The drag is computed for certain typical values of the magnetic interaction parameter and diffusivity parameter. The results reveal the fact that while the stratification and magnetic field have the enhancing effect over the drag, the effect of diffusivity is to decrease it.With 3 Figures     

Golden Coded GFDM for 5G Communication

Wireless Personal Communications - The 5th Generation (5G) of wireless communication will be heterogeneous to support various traffic types and applications. Generalized Frequency Division...     

Synthesis,crystal structure,optical and third order nonlinear optical properties of phosphoric acid pyridine-1-ium-2-carboxylate

A semi-organic nonlinear optical material phosphoric acid pyridine-1-ium-2-carboxylate (PAPC) crystal has been synthesized and grown. Vibrational spectral analysis and NMR spectral analysis has been carried out. Mechanical studies on the grown crystal has been performed which disclose the material belongs to soft materials category. The thermal behaviour of the grown crystal has been investigated by thermogravimetric and differential thermal analysis. UV–Visible spectral analysis has been carried out which reveals that the grown crystal is transparent in the entire visible region with the lower cut-off wavelength of 298 nm and the derived optical constant attests the suitability of this material for non-linear optical applications. The third order nonlinearity has been studied by z-scan method and the enhanced third-order nonlinearity shows PAPC is a potential material for device applications. Second harmonic generation efficiency has been studied by Kurtz and Perry powder test and is found as 0.14 times greater than the KDP.     

Velocity Modulated Bacterial Foraging Optimization Technique (VMBFO)

In this paper, a Velocity Modulated Bacterial Foraging Optimization Technique is proposed. The Bacterial Foraging algorithm is hybridized with Particle Swarm Optimization technique to reduce the convergence time while maintaining high accuracy. The hybridized optimization technique is tested on various benchmark functions like Sphere, Rosenbrock, Generalized Rastrigin, Griewank and Ackley. In addition to these, the proposed algorithm is also tested to calculate the resonant frequency of Rectangular Microstrip Antenna. The results are compared with the existing algorithms and that of experimental results and are found to be in good agreement.     

A novel microencapsulation of neem (Azadirachta Indica A. Juss.) seed oil (NSO) in polyelectrolyte complex of κ‐carrageenan and chitosan

Microcapsules containing neem (Azadirachta Indica A. Juss.) seed oil (NSO) were prepared by encapsulation of natural liquid pesticide NSO in a polyelectrolyte complex of κ‐carrageenan and chitosan. The optimum ratio between carrageenan and chitosan to form a stable polyelectrolyte complex was found as 1 : 0.36. The microencapsulation method for NSO loading was also optimized. SEM study demonstrated that the surface of the microcapsules became more irregular as oil loading increased. The release rates of NSO were studied by varying the percentage of oil loading, concentration of cross‐linking agent, and polymer concentration. Fourier transform infrared spectroscopy (FTIR) study confirmed the complex formation between κ‐carrageenan and chitosan. Differential scanning calorimetry (DSC) and FTIR study indicated the absence of any significant interaction between polyelectrolyte complex of κ‐carrageenan ‐chitosan and NSO. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physicochemical characterization of the filler–matrix interface in elastomer‐encapsulated fly ash/polyester particulate composites

An attempt was made to improve the toughness of fly ash (FA)/general‐purpose unsaturated polyester resin (GPR) composites. Elastomer [styrene–butadiene rubber (SBR) or acrylic copolymer (AC)]‐encapsulated fillers (FA or CaCO₃) were made through the coagulation of the emulsified elastomer containing the filler with constant stirring. The elastomer‐encapsulated fillers were added to GPR at concentrations as high as 15 wt % to make FA/SBR or AC/GPR composites. The mechanical properties (i.e., the tensile strength, tensile modulus, tensile elongation, flexural strength, flexural modulus, impact strength, and hardness) of FA/GPR, FA/SBR/GPR, and FA/AC/GPR composites were studied. The tensile‐fractured surfaces of all the composites were studied with scanning electron microscopy. The thermal stability was studied with thermogravimetric analysis. An analysis of the results indicate that this modification technique is rather easy and more economical than the chemical modification of filler surfaces with functional silane coupling agents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 171–184, 2005