Studies on reduction of chromium doped iron oxide catalyst using hydrogen and various concentration of carbon monoxide

Chemical reduction behaviour of 3% chromium doped (Cr–Fe₂O₃) and undoped iron oxides (Fe₂O₃) were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction spectroscopy (XRD). The reduction processes were achieved with 10% H₂ in nitrogen (%, v/v), 10% and 20% of carbon monoxide (CO) in nitrogen (%, v/v). In hydrogen atmosphere, the TPR results indicate that the reduction of Cr–Fe₂O₃ and Fe₂O₃ proceed in three steps (Fe₂O₃ → Fe₃O₄ → FeO → Fe) with Fe₃O₄ and FeO as intermediate states. A complete reduction to metallic iron for both samples occurred at 900 °C. As for CO reductant, the profiles show the reduction of Fe₂O₃ also proceeded in three steps with a complete reduction occurs at 900 °C in 10% CO with no sign of carbide formation. Nevertheless, a 20% CO was able to reduce the completely at lower temperature at 700 °C and there is a formation of iron carbide at 500 °C but the carbide disappeared as the reduction temperature increase. Meanwhile in 10% CO atmosphere, Cr–Fe₂O₃ shows a better reducibility compared to Fe₂O₃ with a complete reduction at 700 °C, which is 200 °C lower than Fe₂O₃. A Cr dopant in the Fe₂O₃ can lead to formation of various forms of iron carbides such as F₂C, Fe₅C₂, Fe₂₃C₆ and Fe₃C as the CO concentration was increased to 20%. The transformation profile of iron phases during carburization follows the following forms, Fe₂O₃ → Fe₃O₄ → iron carbides (Fe_xC). The XRD pattern shows the diffraction peaks of Cr–Fe₂O₃ are more intense with improved crystallinity for the characteristic peaks of Fe₂O₃ compare to undoped Fe₂O₃. No visible sign of chromium particles peaks in the XRD spectrum that indicates the Cr particles loaded onto the iron oxide are well dispersed. The uniform dispersion with no sign of sintering effects of the Cr dopant on the Fe₂O₃ was confirmed by FESEM. The study shows that Cr dopant gives a better reducibility of iron oxide but promotes the formation of carbides in an excess CO concentration.     

XPS studies of radiation grafted PTFE‐g‐polystyrene sulfonic acid membranes

Structural investigations of PTFE‐g‐polystyrene sulfonic acid membranes prepared by radiation grafting of styrene onto PTFE were conducted by X‐ray photoelectron spectroscopy (XPS). The analyzed materials included original PTFE film as a reference material, grafted film, and sulfonated membrane samples having various degrees of grafting. Interest is focused on C1s, F1s, O1s, and S2p of narrow XPS spectra as the basic elemental components of the membrane. The original PTFE film was found to undergo structural changes in terms of chemical composition and shifting in binding energy induced by incorporation of sulfonated polystyrene grafts, and the amount of such changes depends on the degree of grafting. The atomic ratio of F/C was found to decrease with the increase in the degree of grafting, while that for S/C and O/C were found to increase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 336–349, 2000     

Micropolar fluid flow with temperature‐dependent transport properties

In the present article, the heat transfer rate and the fluid flow of a micropolar fluid along with temperature‐dependent transport properties are scrutinized in the presence of heat generation. The variability in transport properties leads to a rise in the heat transfer and decreases the skin friction. Furthermore, Fourier's heat flux model is implemented in the analysis of heat transfer, employing a suitable transformation to convert the flow model into nonlinear ordinary differential equations. Numerical solutions are obtained by using the shooting method/bvp4c technique. Physical quantities of interest, such as local skin friction and Nusselt number, are discussed and computed. Skin friction decreases with the micropolar parameter but the Nusselt number shows the opposite behavior for the micropolar parameter.     

Physico-chemical characteristics of palm-based oil blends for the production of reduced fat spreads

The effect of blending and interesterification on the physicochemical characteristics of fat blends containing palm oil products was studied. The characteristics of the palm-based blends were tailored to resemble oil blends extracted from commercial reduced fat spreads (RFS). The commercial products were found to contain up to 20.4% trans fatty acids, whereas the palm-based blends were free of trans fatty acids. Slip melting point of the blends varied from 26.0–32.0°C for tub, and 30.0–33.0°C for block RFS. Solid fat content at 5 and 10°C (refrigeration temperature), respectively, varied from 10.9–19.7% and 8.5–17.6% for tub, and 28.2–38.6% and 20.8–33.5% for block RFS. Melting enthalpy of the tub RFS varied from 35.0–54.3 J/g and that of block RFS varied from 58.0–75.4 J/g. To produce block RFS, 65% palm oil (PO) and 18% palm kernel olein (PKOo) could be added in a ternary blend with sunflower oil (SFO), but only 47% PO and 10% PKOo are suggested for tub RFS. Higher proportion of PO, i.e., 72% for block RFS and 65% for tub RFS, could be used after the ternary blend was interesterified. Although a ternary blend of palm olein (POo)/SFO/PKOo was not suitable for RFS formulation, after interesterification as much as 90% POo and 26% PKOo could be used in the block RFS formulation. For tub RFS a maximum of 30% POo was found suitable.     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. III. Thermal stability of the membranes

Thermal stability of cation exchange, PFA‐g‐polystyrene sulfonic acid membranes prepared by radiation‐induced graft copolymerization of styrene onto PFA films followed by sulfonation was studied by thermal gravimetric analysis (TGA) and oven heat treatment. The tested samples included original and grafted PFA films as reference materials. All the membranes showed multistep decomposition patterns due to dehydration, desulfonation, dearomatization, and decomposition of the PFA matrix. Investigations of the individual decomposition behaviors showed that the weight loss strongly depends upon the degree of grafting. However, the decomposition temperatures were found to be independent of the degree of grafting. The loss in some selected membrane properties such as ion exchange capacity and water uptake was found to be function of the degree of grafting, temperature, and the time of heat treatment. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1877–1885, 2000     

Rubberwood–high-density polyethylene composites: Effect of filler size and coupling agents on mechanical properties

Composites were made from rubberwood in the form of fibers (RWF) and powder (RWP) and high-density polyethylene (HDPE). The RWP–HDPE composites showed higher tensile strength than those of the fibers. The inferior properties of the RWF-filled composites were believed to be attributed to the agglomeration of the fibers. Two types of coupling agents, that is, 3-(trimethoxysilyl)propyl methacrylate (TPM) and 3-aminopropyltriethoxysilane (APE), were employed in an attempt to improve the mechanical properties of the composites. The former was able to significantly improve the modulus of elasticity (MOE) and impact strength of the RWF-filled composites. Treatment with TPM resulted in the reduction of the tensile modulus and increase in the elongation at break (EB) for both RWF and RWP-filled composites. APE produced RWP-filled composites with a higher tensile strength and modulus. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1993–2004, 1998     

Effect of calcium and hydroxypropylation on crystallinity and digestibility of rice starches

The digestibility of native and hydroxypropyl rice starches in the presence of calcium was investigated. Calcium interacted with native and hydroxypropyl rice starches and altered their relative crystallinity. Hydroxypropylation was measured in terms of molar substitution (MS) which in turn enhanced calcium binding. Depending upon the amount of calcium added (50–250 μg calcium per g dry starch) and levels of MS (ranging from 0·02 to 0·12), 25·4– 34·1 μg calcium was bound per g of hydroxypropyl starch. Native starch bound 25·4 μg calcium per g dry starch, which was much less than the hydroxy-propylated starches. Crystallinity decreased with the increase of MS and calcium concentration. Digestibility of ungelatinised hydroxypropyl starches increased with MS (2·5–4·1 mg reducing sugar released per g dry starch) and the trend is reversed in the gelatinised form. Calcium-induced amylolysis of the starches by porcine pancreatic α-amylase but somehow inhibited amyloglucosidase attack. © 1998 SCI.     

Graphene oxide‐ellagic acid nanocomposite as effective anticancer and antimicrobial agent

In this study, ellagic acid (ELA), a skin anticancer drug, is capped on the surface(s) of functionalised graphene oxide (GO) nano‐sheets through electrostatic and π–π staking interactions. The prepared ELA‐GO nanocomposite have been thoroughly characterised by using eight techniques: Fourier‐transform infrared spectroscopy (FTIR), zeta potential, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, atomic force microscopy (AFM) topographic imaging, transmission electron microscopy (TEM), and surface morphology via scanning electron microscopy (SEM). Furthermore, ELA drug loading and release behaviours from ELA‐GO nanocomposite were studied. The ELA‐GO nanocomposite has a uniform size distribution averaging 88 nm and high drug loading capacity of 30 wt.%. The in vitro drug release behaviour of ELA from the nanocomposite was investigated by UV–Vis spectrometry at a wavelength of λ _max 257 nm. The data confirmed prolonged ELA release over 5000 min at physiological pH (7.4). Finally, the IC ₅₀ of this ELA‐GO nanocomposite was found to be 6.16 µg/ml against B16 cell line; ELA and GO did not show any cytotoxic effects up to 50 µg/ml on the same cell lines.     

Characteristics of Microencapsulated Palm-Based Oil as Affected by Type of Wall Material

Microcapsules containing a blend of red palm olein (red POo) and refined, bleached and deodorised palm stearin (RBD POs) in the ratio of 60:40 were prepared with various wall materials using a spray-drying technique. The total oil content of the microcapsules ranged from 398 to 683·2gkg⁻¹. Surface oil and moisture content varied from 38·8 to 158·9gkg⁻¹ and 25 to 30gkg⁻¹, respectively. Carotene retention after spray-drying and after storage depended on the oil content and types of wall materials, and ranged from 194·65 to 215·28 and 158·8 to 203·1mgkg⁻¹, respectively. Microcapsules with the best characteristics were made from wall material containing proteinaceous material.     

Thermal Behaviour of Calcium-Hydroxypropyl Rice Starch Complexes

Thermal behaviour of hydroxypropyl rice starches and their calcium complexes was determined by using Differential Scanning Calorimetry (DSC) with starch: water in the ratio of 1:1. Glass transition and gelatinization temperatures were reduced by hydroxypropyl groups and enhanced by calcium treatment. Gelatinization enthalpies were reduced by both hydroxypropyl groups and calcium treatment. The interaction of hydroxypropyl groups and calcium with starch altered the two endothermic peaks observed in native starch into a single melting peak.