Dehydrogenation of C3–C4 paraffin's to corresponding olefins over slit-SAPO-34 supported Pt-Sn-based novel catalyst

The objective of this work is to discuss the performance of Pt-Sn/slit-SAPO-34 novel catalyst for selective C₃–C₄ dehydrogenation to corresponding light olefins. The metallic contents, acidity, active metallic sites and metallic dispersion were determined using a number of physico-chemical techniques as it gives a justification for superior catalytic activity for dehydrogenation reaction. The Pt-Sn/slit-SAPO-34 catalyst was analyzed for dehydrogenation activity under optimized operating conditions; at atmospheric pressure, hydrogen to alkane (feed) molar ratio is 0.2, weight hourly space velocity 5 h^?1 and temperature 585 °C. Around 40% light alkane conversion and above 95% of total olefins selectivity with 94% propene, 92% n-butene and about 84% iso-butene selectivity were achieved over Pt-Sn/slit-SAPO-34 novel catalyst. The catalyst was parametrically characterized over the above said operating conditions and effects of operating conditions on product distribution were discussed. The coke formation was inherently related to catalyst activity in dehydrogenation reaction and related to surface intermetallic ensemble effects; and ultimately the prominent stakeholder in catalyst deactivation. The novel catalysts also showed very good hydrothermal stability in a continuous reaction–regeneration cycles due to silica-based acidic structure of support. The results obtained over Pt-Sn/slit-SAPO-34 novel catalyst were compared with other Pt-Sn-based ZSM-5 and SAPO-34 supported catalysts of similar active metallic content under identical operating conditions.     

Biosorption of Direct Red-31 and Direct Orange-26 dyes by rice husk: Application of factorial design analysis

The present work describes the biosorption potential of low cost and easily available rice husk for the adsorptive removal of Direct Red-31 and Direct Orange-26 textile dyes. In the present investigation a 5³ full factorial design analysis experiment was employed to optimize the process parameters for enhanced adsorptive removal of Direct Red-31 and Direct Orange-26 textile dyes from aqueous solution. Factorial experiments with three factors initial dye concentration, biosorbent dose and pH at five levels were conducted in duplicate. The biosorbent efficiency for the dyes was determined after 3 h of treatment at 30 °C using suitable size of biosorbent (0.255 mm). Analysis of variance (ANOVA), F-test and p-values were used to study the main, two ways and three ways interaction effects. The values of regression coefficients (R² = 0.999) for both dyes confirmed the good fitness of model. A maximum biosorption capacity of 57.88 and 36.14 mg/g was observed at pH 2 and 3 for Direct Red-31 and Direct Orange-26, respectively, with 125 mg/L dyes concentration. The most significant variable was found to be dyes initial concentration. Moreover, the decolorization of both direct dyes was also affected by salts, heavy metal ions and surfactants.     

Effect of uniaxial drawing on the structure and glass transition behavior of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites

The structure–property relationships of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites are being investigated under uniaxial drawing by using synchrotron wide angle X-ray diffraction, small angle X-ray scattering, transmission electron microscope and dynamic mechanical analyzer. The cold crystallization at 110 °C of PTN and nanocomposites samples under drawing induced the α-crystal form with the chain axis (c-axis) aligned along the drawing direction as well as parallel to the layered clay surface. However, the broad surfaces of the layered clay are oriented and rotated nearly perpendicular to the sample's surface, forming the house of cards type structure. Such structural formation of layered clay in the PTN matrix influenced the thermomechanical properties depending on the extent of confinement and surface interaction effects. The amorphous and crystallized structures of the nanocomposites showed the analogous tendency in which T_g decreased and increased before and after drawing, respectively, relative to the neat PTN. Despite the evolution of free volume after drawing, the nanocomposites exhibited an unusual positive shifting trend in T_g. The deviation of T_g in the PTN nanocomposites system is ascribed to the interplay of two competing effects; (i) the increase in the local free volume owing to the confining effect of intercalation (enhanced the chain mobility) and (ii) entropic constraint imposed by the stronger interfacial interaction due to the physical jamming of layered clay (retarded the chain mobility).     

A real-coding jumping gene genetic algorithm (RJGGA) for multiobjective optimization

This paper presents a real jumping gene genetic algorithm (RJGGA) as an enhancement of the jumping gene genetic algorithm (JGGA) [T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, A jumping gene algorithm for multiobjective resource management in wideband CDMA systems, The Computer Journal 48 (6) (2005) 749-768; T.M. Chan, K.F. Man, K.S. Tang, S. Kwong, Multiobjective optimization of radio-to-fiber repeater placement using a jumping gene algorithm, in: Proceedings of the IEEE International Conference on Industrial Technology (ICIT 2005), Hong Kong, 2005, pp. 291-296; K.F. Man, T.M. Chan, K.S. Tang, S. Kwong, Jumping-genes in evolutionary computing, in: Proceedings of the IEEE IECON’2004, Busan, 2004, pp. 1268-1272]. JGGA is a relatively new multiobjective evolutionary algorithm (MOEA) that imitates a jumping gene phenomenon discovered by Nobel Laureate McClintock during her work on the corn plants. The main feature of JGGA is that it only has a simple operation in which a transposition of gene(s) is induced within the same or another chromosome in the genetic algorithm (GA) framework. In its initial formulation, the search space solutions are binary-coded and it inherits the customary problems of conventional binary-coded GA (BCGA). This issue motivated us to remodel the JGGA into RJGGA. The performance of RJGGA has been compared to other MOEAs using some carefully chosen benchmark test functions. It has been observed that RJGGA is able to generate non-dominated solutions with a wider spread along the Pareto-optimal front and better address the issues regarding convergence and diversity in multiobjective optimization.     

Cd transfer across water/1,2-dichloroethane microinterfaces facilitated by complex formation with 1,10-Phenanthroline

The transfer of Cd²⁺ facilitated by 1,10-Phenanthroline (phen) was investigated at the microinterface of two immiscible electrolyte solutions, hosted by a 25 μm diameter orifice of a micropipette. Cyclic voltammetry (CV) was employed to examine the transfer in the conditions of the ligand (organic phase) in excess and Cd²⁺ (aqueous phase) in excess. In these conditions, asymmetric (peak-shaped in the forward scan and steady state in the backward scan), and reversible steady state (for the two scan directions) voltammograms were observed. The dependence of half-wave potential on the ligand concentration suggested that the equilibrium was effectively displaced towards a 1:3 (Cd²⁺:ligand) stoichiometry, with a formation constant, β₃ = 3.9 × 10²⁹. The diffusion coefficients of Cd²⁺ in the aqueous solution and those of phen, Cd(phen)₃²⁺ in organic phase were evaluated to be 6.5 × 10⁻⁶, 5.8 × 10⁻⁶, and 5.1 × 10⁻⁶ cm² s⁻¹ respectively, using CV.     

Failure Analysis of a Threaded Pipe Ruptured During Hydraulic Testing

In the present case study, failure analysis of a piping system that ruptured during hydraulic testing has been carried out to find the root cause and determine the mode and mechanism of failure. Chemical composition of the pipe was found to be in compliance with the standard composition of AISI4130. The failure cause of the pipe has been investigated through visual examination, microstructural observation, hardenability analysis, and fractography. Threaded grooves were produced through machining after heat treatment. Variation in hardness and strength through thickness (from case to core) was evaluated using standard hardenability graph. Hardenability analysis showed that the strength of the pipe after machining was still well above the calculated maximum stress at any point of piping system. This finding was further supported by the microstructural study. The actual cause of pipe failure during hydraulic test was found to be due to the stress concentration factor being developed by some notch from improper thread machining which lead brittle failure and was also revealed by fractography analysis.