Polystyrene‐supported polyoxyethylene bound potassium permanganate as a heterogeneous oxidizing agent

Oxidation behavior of a 2 mol % divinylbenzene (DVB)‐crosslinked polystyrene‐supported permanganate function was investigated toward low molecular weight primary and secondary alcohols and aldehydes. The permanganate function was attached to a polystyrene support through cyclic polyoxyethylene (POE) units immobilized on the support. Contrary to the oxidations catalyzed by low molecular weight permanganate reagents, the oxidation of primary alcohol terminated in the aldehyde stage. The secondary alcohols were converted to the respective ketone and aldehyde to acid. The effect of the variable parameters similar to solvent, temperature, and reagent to substrate ratio was followed. Nonpolar cyclohexane was found to be the best solvent for the present study. Also the reactivity increased with increasing temperature. The oxidizing reagent possesses a long shelf life and could be recycled several times without reduction of capacity and mechanical stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3708–3717, 2003     

Mixed oxide supported hydrodesulfurization catalysts—a review

Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al₂O₃ containing mixed oxide supports, TiO₂ containing mixed oxide supports, ZrO₂ containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO₂ containing mixed oxides received maximum attention, especially TiO₂–Al₂O₃ supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication.     

Discrete singular convolution and its application to the analysis of plates with internal supports. Part 2: Applications

Part 2 of this series of two papers presents the applications of the discrete singular convolution (DSC) algorithm. The main purpose of this paper is to explore the utility, test the accuracy and examine the convergence of the proposed approach for the vibration analysis of rectangular plates with internal supports. Both partial internal line supports and complex internal supports are considered for 21 square plates of various combinations of edge support conditions. The effects of different size, shape and topology of the internal supports and different boundary conditions on the vibration response of plates are investigated. The partial internal line supports may vary from a central point support to a full range of cross or diagonal line supports. Several closed‐loop supports, such as ring, square and rhombus, and their combinations are studied for complex internal supports. Convergence and comparison studies are carried out to establish the correctness and accuracy of the DSC algorithm. The DSC results are compared with those in the available literature obtained by using other methods. Numerical results indicate that the DSC algorithm exhibits controllable accuracy for plate analysis and shows excellent flexibility in handling complex geometries, boundary conditions and support conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

Repair of Cracked Aluminum Overhead Sign Structures with Glass Fiber Reinforced Polymer Composites

Transportation departments have been using aluminum overhead sign structures since the 1950s. It is well documented that cracks develop in the welds between diagonal and chord members due to fatigue stresses from wind-induced vibration of the slender members. The cracks propagate to complete failure of the members, which can cause collapse of the truss and inflict injuries. The original design of overhead sign structures did not consider fatigue as a limit state. In addition, field welding of aluminum structures for any possible repairs is prohibited. A repair method for the cracked aluminum welded connections between diagonals and chord members using glass fiber reinforced polymer composites (GFRPs) is proposed. The static load carrying capacity of the welded connection, and the cracked connection repaired with GFRP composites are established. The paper describes the surface preparation of the aluminum tubular members, and the architecture and application sequence of the GFRP composite to retrofit the connection. Experimental results are presented from static tests of welded aluminum connections, welded aluminum connections retrofitted with GFRP composites, and new aluminum connections that depend only on GFRP composite elements for their strength. The results from monotonic static tests carried out on cracked welded specimens from actual sign structures show that the retrofitted connection with GFRP reinforcement achieved 1.17 to 1.25 times the capacity of the welded aluminum connection without any visible cracks. This result, and the minimal traffic disruption anticipated in the actual field application, makes this retrofit method a good candidate for implementation.     

Influence of Pt particle size on catalytic combustion of xylenes on carbon aerogel-supported Pt catalysts

Pt catalysts supported on a carbon aerogel with different Pt particle sizes were studied in the combustion of o-xylene and m-xylene. Results found show that the activity of the catalysts increased with larger Pt particle size. In addition, the catalysts were activated during consecutive combustion runs and during time on stream. This activation depends on the Pt particle size and type of xylene isomer. Activation was due to the increase in Pt particle size during reaction. The lower activity of catalysts with smaller Pt particle size was due to the stronger PtO bonds formed during xylene combustion by the smaller Pt particles.     

Potentiometric studies of oxidation–reduction reactions with redox copolymers

Polymeric oxidants in the bead form that were macroporous styrene/divinylbenzene copolymers containing N‐chlorosulfonamide functional groups (in sodium or hydrogen form) or N‐bromosulfonamide groups (in sodium form) were synthesized and investigated to determine their oxidizing powers. The redox potentials of the N‐chlorosulfonamide/sulfonamide and N‐bromosulfonamide/sulfonamide systems were determined by potentiometric studies at different pH values with aqueous solutions of Na₂SO₃, KCN, and KSCN as reducers. The formal redox potentials of the N‐chlorosulfonamide copolymers were 0.79, 0.44, and ?0.12 V at pH's of 1.8, 8.45, and 13.6, respectively. The formal redox potential of the N‐bromosulfonamide copolymer was about 100 mV higher in comparable conditions and in solutions over pH = 5 (e.g., 0.56 V at pH = 8.56). The comparatively higher oxidizing power of the N‐bromosulfonamide copolymer was particularly evident in a strong alkaline medium (in which the N‐chlorosulfonamide copolymer was not reactive). In contrast, the N‐chlorosulfonamide copolymer showed strong oxidative properties in acidic media (in which the N‐bromosulfonamide copolymer decomposed itself). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Partial oxidation of methane towards hydrogen production over a promising class of catalysts: Rh supported on Ti-modified MgO

The partial oxidation of methane over the supported Rh (0.8 wt.%) catalysts was investigated. Two kinds of supports were used, MgO and Ti-modified MgO (prepared by grafting technique). Among the Ti-modified MgO supports, two different compounds were used as source of Ti: inorganic (chloride) and organic (alkoxide). The catalytic performance of Rh-supported catalysts depends on the support and varies in the sequence: Ti-MgO/I > Ti-MgO/O > MgO. Ti-containing catalysts exhibited higher activity and selectivity compared to MgO, which is especially noticeable at low temperature. Possible explanations for the phenomena observed were proposed on the basis of characterization results.     

Maximizing learning without sacrificing the fun: Stealth assessment,adaptivity and learning supports in educational games

In this study, we investigated the validity of a stealth assessment of physics understanding in an educational game, as well as the effectiveness of different game-level delivery methods and various in-game supports on learning. Using a game called Physics Playground, we randomly assigned 263 ninth- to eleventh-grade students into four groups: adaptive, linear, free choice and no-treatment control. Each condition had access to the same in-game learning supports during gameplay. Results showed that: (a) the stealth assessment estimates of physics understanding were valid—significantly correlating with the external physics test scores; (b) there was no significant effect of game-level delivery method on students' learning; and (c) physics animations were the most effective (among eight supports tested) in predicting both learning outcome and in-game performance (e.g. number of game levels solved). We included student enjoyment, gender and ethnicity in our analyses as moderators to further investigate the research questions.     

开孔剂对多孔氧化铝支撑体的影响

研究了开孔剂对a-Al2O3多孔道氧化铝支撑体的影响,发现开孔剂的种类及质量分数对支撑体的性能有重要影响,选择合适的开孔剂种类及质量分数可使氧化铝支撑体的纯水通量提高2～3倍。     

Effect of the nature and degree of crosslinking on the Rose Bengal uptake by DVB‐, NNMBA‐, HDODA‐, and TTEGDA‐crosslinked aminopolyacrylamides

Polyacrylamides with 2–20 mol % divinyl benzene (DVB), N,N′‐methylene‐bisacrylamide (NNMBA), 1,6‐hexanediol diacrylate (HDODA), and tetraethyleneglycol diacrylate (TTEGDA) crosslinking and without crosslinking were prepared by free radical solution polymerization. Amino functions were incorporated into these polymers by transamidation with excess ethylenediamine. The dye uptake of nonprotonated and protonated aminopolyacrylamides was followed by batch equilibration method towards Rose Bengal (RB), Methyl Orange (MO), Methyl Red (MR), and Methylene Blue (MB). RB uptake by the polyacrylamide‐supported systems is higher than other dyes. Generally the dye uptake by the protonated systems is higher than the nonprotonated systems. To optimize the conditions of dye uptake, the effect of the concentration of RB solutions, temperature, and pH were followed. Kinetic studies showed that the uptake of RB by both nonprotonated and protonated crosslinked aminopolyacrylamides is a phase boundary process followed by three‐dimensional diffusion. The extent of RB uptake by the various systems depends on the nature and degree of crosslinking, and the relative rigidity/flexibility ofthe polyacrylamide support. Thus, the dye uptake followed the order: linear > NNMBA‐ > DVB‐ > TTEGDA‐ > HDODA‐crosslinked system. The dye uptake followed the same trend as the variation of amino capacity with degree of crosslinking in the respective crosslinked system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007