Vapour phase esterification of butyric acid with 1-pentanol over Al-MCM-41 mesoporous molecular sieves

Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 & 100 were synthesized hydrothermally and characterized systematically by various analytical and spectroscopy techniques. Their catalytic activity was evaluated for the vapour phase reaction of butyric acid with 1-pentanol. Pentyl butyrate was obtained as the only product. Reaction parameters such as temperature, molar ratio and feed rate were optimized for higher butyric acid conversion. The time-on-stream study was carried out at optimum conditions resulting in gradual decrease in the activity of the catalyst.     

Characterization of microstructural changes during annealing of cold worked austenitic stainless steel using ultrasonic velocity measurements and correlation with mechanical properties

A technique that is sensitive to change in texture is more reliable than mechanical property measurements for the study of recrystallization behavior in alloys where recrystallization is coupled with precipitation. Hence, ultrasonic velocity measurements have been employed to characterize microstructural changes during annealing of cold worked Ti-modified austenitic stainless steel where precipitation of TiC is known to retard recrystallization. Mechanical property measurements, such as strength and hardness, could not distinguish the recovery and recrystallization regimes, and it was difficult to determine the exact time or temperature for onset of recrystallization. The variation of velocity with annealing time or annealing temperature exhibited a three-stage behavior. The velocity exhibited a slight increase in the recovery region followed by a sharp and continuous decrease in the recrystallization region and reached saturation on completion of recrystallization. Based on the microstructural investigations, the three stages were identified to be recovery, progress of recrystallization, and completion of recrystallization. Velocity measurements could sense the onset, progress, and completion of recrystallization more accurately compared with that of hardness and strength measurements.     

Solid-state production of esterase using fish processing wastes by Bacillus altitudinis AP-MSU

The bacterium Bacillus altitudinis AP-MSU, able to produce esterase was isolated from the gut of marine fish Sardinella longiceps. The esterase production was investigated in solid-state fermentation experiment using various fish processing waste meal. Among the tested fish processing wastes, red grouper waste emerged as the best source for higher esterase production. The suitable surfactant and triglyceride identified to increase the lipase production was neem oil. Effect of individual carbon and nitrogen sources supplementation on esterase production revealed that fructose and peptone aided the higher esterase production than the other tested carbon and nitrogen sources. The suitable concentration of sodium chloride for higher esterase production was at 5%. Effect of surfactants and trace elements on esterase production showed that Tween 20 and zinc sulphate, respectively produced maximum amount of esterase. The effect of physical parameters on lipase production revealed that 50 °C temperature and pH 7–8 were optimum for higher esterase production. Statistical optimization with Plackett–Burman design showed that neem oil, NaCl and fructose were found to be the most predictive factors for esterase production by this strain.     

Nitrogen redistribution, microstructure, and elastic constant evaluation using ultrasonics in aged 316LN stainless steels

The presence of even dilute concentrations of nitrogen (0.08 mass pct) is found to have a strong influence on the microstructure of a nuclear grade 316LN austenitic stainless steel, thermally aged at 1123 K. High-resolution transmission electron microscopy (TEM) evidence of pre-precipitation reactions involving formation of Cr-N rich clusters prior to Cr₂N precipitation has been presented. A tendency for cellular precipitation has been observed on continued aging above 500 hours. Beyond 1000 hours, chi precipitates are the most frequently seen phase. The observed microstructural variations correlate well with ultrasonic velocity and attenuation measurements. The present study reveals that nitrogen in solid solution decreases all the elastic constants, namely longitudinal modulus, elastic modulus, shear modulus, and bulk modulus in this steel but has a negligible effect on Poisson’s ratio. The stages associated with the precipitation of intragranular coherent Cr₂N are, however, associated with an increase in all the elastic constants including Poisson’s ratio.     

Ultrasonic velocity measurements for characterizing the annealing behaviour of cold worked austenitic stainless steel

Precise measurements of shear wave velocities have been made in 20% cold worked and annealed samples of alloy D9 (Ti-modified austenitic stainless steel) to characterize the microstructural changes during annealing. The variation in wave velocity with annealing time exhibited a three stage behaviour. In the first stage, a slight increase in the velocity during recovery regime has been observed. This is followed by a significant increase in the velocity in the recrystallization regime (second stage) and reaching saturation on completion of recrystallization (third stage). Microstructural observations using optical metallography confirmed these three stages. The maximum variation in velocity is observed only when the polarization or the propagation direction of the shear wave is alingned with the cold working direction. Variation in shear wave velocity during annealing process, in general, is just opposite to that of the variation in longitudinal wave velocity. A number of velocity measurements were made by changing the propagation and polarization directions of the shear waves with respect to the cold working direction. Based on these measurements, a suitable velocity ratio parameter is suggested for determining the degree of recrystallization during annealing of cold worked alloy D9.     

Kinetics of Ag(I) catalyzed oxidation of amino acids by peroxomonosulphate

Silver(I) catalyzed oxidation of amino acids such as glycine and α-alanine by peroxomonosulphate (PMS) in aqueous perchloric acid medium was found to be first order in [peroxomonosulphate] and fractional order in [amino acid] and [Ag(I)]. The rate equation was derived by assuming equilibrium formation of adduct between amino acids and Ag(I). This adduct was presumed to react with PMS in a slow step to yield (adduct)²⁺, which was self-oxidized in a fast step to give the products. The kinetic results revealed that silver catalyzed reaction occurred approximately 10⁴ times faster than the uncatalyzed reaction and this is attributed to the formation of (adduct)²⁺. The bimolecular rate constant (k) for the slow step and the activation parameters were calculated and the results are discussed.     

Synthesis and characterization of Zr4+, La3+ and Ce3+ doped mesoporous TiO2: evaluation of their photocatalytic activity

Sol-gel method was used to synthesize Zr(4+), La(3+) and Ce(3+) doped mesoporous TiO(2) materials with different weight percentage (0.5, 1.0, 2.0 and 3.0 wt%) using triblock copolymer as the structure directing template in ethanol/water medium. Characterization revealed the isomorphic substitution of Zr(4+) ion into the lattice of TiO(2), and surface binding nature of La(3+) and Ce(3+) ions on mesoporous TiO(2). Microscopic examination confirmed the surface adsorption of foreign ion which could alter the particle morphology. The size of the particles was less than 20 nm. Photocatalytic activity of metal ions doped mesoporous TiO(2) was evaluated using aqueous alachlor as a model pollutant. It was found that 1 wt% Ce(3+) doped mesoporous TiO(2) exhibited higher activity than pure and other metal ions doped mesoporous TiO(2). The change of oxidation state of Ce(3+) is suggested to be the cause for enhanced photocatalytic activity.     

Activation of ethyl acetate over metal substituted MCM-41: application to alkylation and acylation

Al-MCM-41, Fe,Al-MCM-41 and Zn,Al-MCM-41 materials with different silicon to metal ratios were synthesized hydrothermally and characterized by XRD, BET, FT-IR, Acidity measurement by pyridine adsorbed FT-IR spectroscopy, ²⁹Si and ²⁷Al MAS NMR and ESR techniques. The orderly arrangement of mesoporous materials was clearly revealed from the XRD patterns. ²⁹Si and ²⁷Al MAS NMR established the co-ordination environment of silicon and aluminium. Electron paramagnetic resonance (EPR) study confirmed the co-ordination environment of Fe in Fe,Al-MCM-41 framework. The catalytic activity of these materials was evaluated in the vapour phase alkylation and acylation of ethylbenzene with ethyl acetate in the temperature range between 250 and 400 °C. The products were found to be 1,3-diethylbenzene (1,3-DEB), 1,4-diethylbenzene (1,4-DEB), 1,2-diethylbenzene (1,2-DEB), 4-ethylacetophenone (4-EAP) and acetophenone (AP). The reaction products revealed that activation of ethyl acetate is a convenient route for both alkylation and acylation reactions. The order of the catalysts activity for the reaction is found to be Fe,Al-MCM-41 (50) > Fe,Al-MCM-41 (100) > Zn,Al-MCM-41 (50) > Zn,Al-MCM-41 (100) > Al-MCM-41 (50) > Al-MCM-41 (100). In addition to the density of acid sites, the strength of acid sites is also important for this reaction. The effects of temperature, feed ratio, WHSV and time on stream were also examined and the results are discussed.     

Selective ion-exchange in MAPO-36 and its application in toluene disproportionation

MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg²⁺ in the framework of AlPO-36 and ion-exchanged with Fe³⁺, Zn²⁺, La³⁺ and Ce³⁺ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36. The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)₂⁺ to MO⁺. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h.     

Energy efficient secured K means based unequal fuzzy clustering algorithm for efficient reprogramming in wireless sensor networks

Wireless Networks - Wireless Sensor Networks (WSNs) is a collection of tiny distributed sensor nodes that have been used to sense the physical parameters of the environment where it has been...