Integral method of analysis of fischer-tropsch synthesis reactions in a catalyst pellet

A generalized integral method is developed to analyze complex reactions in a catalyst pellet. This method is valid for any kinetics and takes into account both internal and external heat and mass transfer effects. The integral equations are solved for a Fischer-Tropsch kinetic model to obtain effectiveness factors. Isothermal multiplicities are observed for low values of the surface coverage parameter α(α = 1/K₁p_co,0), and low values of the parameter σ₂₁ (ratio of Thiele moduli for H₂ and CO). The effectiveness factor is mildly sensitive to the external resistances.     

Kinetics of reactions involved in pyrolysis of cellulose I. The three reaction model

Kinetics of reactions involved in pyrolysis of cellulose has been modeled in terms of a three reaction model. In this model it is assumed that cellulose decomposes to tars, chars and gaseous products via three competitive first-order reactions. Arrhenius parameters have been obtained to describe the rate constants of these reactions. The three reaction model predicts the weight loss data reasonably well. Product yields of tars, chars and gases predicted by the three reaction model are compared over the temperature range 250 to 360°C. In this communication a technique for analyzing experimental data of a solid state reaction is presented.     

Superior electrical,mechanical and viscoelastic properties of CNTs coated carbon textile reinforced phenolic composite for high-performance structural applications

In the present study, carbon nanotubes (CNTs) were grown up on nickel-coated carbon textiles utilizing acetylene gas as a carbon precursor in an isothermal CVD reactor. The effects of CNT coating time (0 to 25 min) in the carbon textile-phenolic composites (CPCs) prepared via conventional hand-layup technique followed by compression molding were assessed using microstructures, static and dynamic mechanical thermal analysis, density and electrical properties. Significant improvement was observed in static as well as dynamic mechanical properties and electrical properties for all the CNT coated samples. Though, 15 min coating time gives the optimum results. The results showed ~71, 74, 62, 67, 38, and 45% increment in storage modulus, loss modulus, flexural strength, flexural modulus, tensile strength, Young's modulus, respectively. Furthermore, huge improvement (707%) in electrical conductivity and significant enrichment in thermal stability mark CNTs coated carbon textile as the efficient alternative reinforcement for high-performance thermo-structural applications such as aerospace and automotive fields.     

Synthesis and characterization of modified cottonseed oil based polyesteramide for coating applications

Cottonseed oil fatty amide (CFA) was prepared in the laboratory by base catalyzed aminolysis of cottonseed oil. Further it was reacted with phthalic acid to obtain polyesteramide (CPEA) and modified by post reacting with vinyl acetate monomer in varying ratios of 4:1, 3:1 and 2:1 in the presence of t-butyl hydroperoxide as an initiator. The incorporation of vinyl acetate in CPEA was analyzed using FTIR, ¹H NMR and ¹³C NMR spectral techniques. The physico-chemical properties such as iodine value, specific gravity and refractive index were determined by standard laboratory test methods. Mechanical, chemical resistance and other coating properties of the coatings synthesized from CPEA and modified CPEA applied on mild steel substrates were also studied by standard methods. Thermal stability and curing behavior of modified CPEA were determined by thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) techniques. It was observed that modification of polyesteramide improved the curing, mechanical and chemical performance of CPEA films. It was found that among the CPEA:vinyl acetate ratios, 2:1 ratio exhibited the best results.     

Perturbation signal design for neural network based identification of multivariable nonlinear systems

The paper focuses on issues in experimental design for identification of nonlinear multivariable systems. Perturbation signal design is analyzed for a hybrid model structure consisting of linear and neural network structures. Input signals, designed to minimize the effects of nonlinearities during the linear model identification for the multivariable case, have been proposed and its properties have been theoretically established. The superiority of the proposed perturbation signal and the hybrid model has been demonstrated through extensive cross validations. The utility of the obtained models for control has also been proved through a case study involving MPC of a nonlinear multivariable neutralization plant.     

Utilization of Granite Powder as Filler in PC-Toughened Epoxy Resins: Studies on Physico-Mechanical Properties

The present study reports the possibility of using granite powder, an industrial waste with no end use, as potential filler in polycarbonate (PC)-toughened epoxy resin. Testing data for the physico-mechanical properties such as tensile, flexural, density and void content of the composites, according to the filler loading were catalogued. Incorporation of waste granite powder in toughened resin enhances the mechanical properties when compared to neat epoxy, but reduces significantly with respect to toughened resin matrix.     

Molecular Transport of Organic Esters Into Fluoropolymer Membranes

The effects of different fluorine contents of the Du Pont VITON fluoropolymers have been studied in the presence of esters such as methyl acetoacetate, ethyl acetoacetate, methyl benzoate, ethyl benzoate, and 1-butyl acetate in the temperature interval of 25°–60°C. The sorption and diffusion of these liquids into the polymer membranes tend to deviate slightly from the Fickian mechanism; however, the diffusion data have been calculated from the Fickian model. It is suggested that the hindered chain segmental motion and the structural differences in the polymer membranes contribute to the overall sorption process, in addition to strictly thermodynamic considerations. The activation parameters for the transport processes have been estimated and the results are discussed in terms of the nature of polymer-solvent interactions.     

Process Evaluation of AISI 4340 Steel Manufactured by Laser Powder Bed Fusion

Laser powder bed fusion (L-PBF) involves the consolidation of metal powder, layer by layer, through laser melting and solidification. In this study, process parameters are optimized for AISI 4340 steel to produce dense and homogeneous structures. The optimized process parameters produce mechanical properties at the center of the build plate that are comparable to wrought in the vertical and horizontal orientations after heat treatment and machining. Four subsequent builds are filled with specimens to evaluate the mechanical behavior as a function of location and orientation. Variations in the mechanical properties are likely due to recoater blade interactions with the powder and uneven gas flow. The results obtained in this study are analyzed to assess the reliability and reproducibility of the process. A different build evaluates the performance of near-net-shaped tensile specimens angled 35°-90° from the build plate surface (horizontal). Ductility measurements and surface roughness vary significantly as a function of the build angle. In the stress-relieved and as-built conditions, the mechanical behavior of vertically oriented specimens exhibits somewhat lower and more variable ductility than horizontally oriented specimens. Therefore, several process variables affect the mechanical properties of parts produced by the L-PBF process.     

Systematic generation of thermochemical cycles for water splitting

Based on the observation that a thermochemical cycle is tantamount to a reaction route (RR) we employ the well-developed concepts of response reactions (RERs) and direct reaction routes (RRs) to develop an algorithm for a systematic enumeration of thermodynamically feasible thermochemical cycles for water splitting. The input is a set of chemical species along with their thermodynamic characteristics. A unique set of reactions is next generated from a list of species using the formalism of RERs. These are further screened and reduced to a subset of thermodynamically favorable RERs. Alternatively, the reactions may be selected from a separately build database of chemical reactions. The reactions are next assembled into direct RRs (thermochemical cycles), i.e., linear combinations of reactions that produce the desired overall reaction (OR), i.e., 2H₂O = 2H₂ + O₂. Only the direct RRs that satisfy the thermodynamic feasibility condition are further retained. The proposed algorithm is a new powerful tool for automatic generation and screening of thermodynamically feasible thermochemical cycles.