Shahzad Barghi

Ionic polymerizations and related processes

Preface. Program. List of Participants. List of Contributors (Lecturers). Part I: Cationic Polymerization. Cationic Polymerizations at Elevated Temperatures by Novel Initiating Systems Having Weakly Coordinating Counteranions. 1. High Molecular Weight Polyisobutylenes Z. Pi, et al. Cationic Polymerization: Industrial Processes and Applications R.J. Pazur, H.H. Greve. New Branched Polyisobutenes and Butyl Rubbers by the Inimer Method G. Langstein, et al. Newer Aspects of Photoinitiated Cationic Polymerization J.V. Crivello. Cationic Macromolecular Design using Non(homo)polymerizable Monomers Y.C. Bae, et al. Segmented Polymer Networks by Cationic Polymerization: Design and Applications F.E. Du Prez, E.J. Goethals. Rate Constants and Reactivity Ratios in Carbocationic Polymerizations H. Mayr. Photochemically Induced Cationic Photopolymerization of Vinyl Ethers and Oxethanes O. Nuyken, M. Ruile. Kinetics of the Living Polymerization of Isobutylene J.E. Puskas, et al. Kinetics and Mechanism of Living Cataionic Polymerization of Olefins R.F. Storey, et al. Stopped-flow Technique and Cationic Polymerization Kinetics J.P. Vairon, et al. Photoinitiated Cationic Polymerization Y. Yagci. Part II: Anionic and Other Related Processes. A Forgotten Class of High Tg Thermoplastic Materials: Anionic Copolymers of Styrene and 1,1-Diphenylethylene. Synthesis, Toughening and Block Copolymerization with Butadiene K. Knoll, et al. Control of Active Centers Reactivity in the High Temperature Bulk Anionic Polymerization of Hydrocarbon Monomers A. Deffieux, et al. Arborescent Polymers: Highly Branched Homo- and Copolymers with Unusual Properties M. Gauthier. Similarities and Discrepancies between Controlled Cationic and Radical Polymerizations K. Matyjaszewski. Recent Developments in Anionic Synthesis of Model Graft Copolymers J. Mays. Kinetics of Elementary Reactions in Cyclic Ester Polymerization S. Penczek, et al. Synthesis and Properties of Amphiphilic and Functional Copolymers and Networks R. Velichkova, et al. Modeling, Simulation and Control of Polymerization Processes: Some Aspects for Tailored Synthesis A.F. Johnson, et al. Conference Photos.

Mixing and segregation of binary mixtures of particles in liquid–solid fluidized beds

Abstract The effects of size, shape, and density of tracer particles on mixing and segregation in liquid–solid fluidized beds were studied. A collision technique was used to define a new mixing index. Collisions between tracer particles and probes were found at 16 locations inside the fluidized bed simultaneously. The collision frequency of particles on probes was considered to be proportional to their local concentration inside the fluidized bed. Glass beads (3 and 5 mm in diameter) were used to study the effect of size on mixing. Graphite beads and cylindrical aluminum beads were introduced into a bed of spherical glass beads to investigate the density and shape effects, respectively. Smaller bed heights enhanced the mixing of particles lighter than the bed particles. Particle density had a greater effect on segregation than size and shape.

Defluidized zones in liquid–solid fluidized beds

Abstract Defluidized zones often appear on the distributor plates of liquid–solid fluidized beds. They can lead to hot spots, the formation of undesirable side products or the degradation of products or reactants. In some cases, a solid residue forms and plugs the distributor. Two different techniques were developed to detect defluidized zones. The first technique uses a specially designed collision probe to monitor local particle motion. The second technique is aimed at the on-line detection of defluidized zones in industrial bioreactors. It uses local bed conductivity fluctuations. Defluidized zones were measured in beds of 3 or 5 mm diameter glass beads fluidized by an aqueous saline solution. Special experiments established the importance of horizontal liquid flow and distributor plate roughness on the formation of defluidized zones. A model describes how a defluidized zone can be eliminated. It considers that a defluidized zone is broken by the drag force on its particles of downward and sideways liquid flow. This liquid flow is induced by suction from the liquid jets issuing from the distributor holes. The resulting drag force is resisted by friction between particles or between particles and the distributor surface.

New method for monitoring of adsorption column saturation and regeneration I. Demonstration of the measurement principle

A new method suitable for the on-line monitoring of adsorption column saturation/regeneration cycles was developed based on the discovery that the electrical resistance of adsorbents changes dramatically upon adsorption and returns to its original value upon desorption, and that this change can be measured reliably. The phenomenon was demonstrated on four different adsorbent/adsorbate systems, on both single particles and in a packed bed between parallel plates. The observed phenomenon was studied on the carbon/CO2 system in more detail, because of the availability of extensive literature data. It was found that the resistance change in this system correlated with the amount of CO2 adsorbed. The correlation was used to construct an adsorption isotherm based on resistance change data.

Practical approach to measure the relative activity of heterogeneous catalysts

Abstract This paper introduces a simple, practical approach to measure the relative activity of various heterogeneous catalysts using electrical measurements. The applicability of this practical method was demonstrated on four commercial catalysts; a potassium-promoted iron oxide used for the dehydrogenation of ethyl benzene to produce styrene, a commercial hydrotreating catalyst used to remove sulfur and nitrogen from crude oil distillates such as gasoline or gas oil, a basic alumina that catalyzes the hydrolysis of halogenated hydrocarbons, and an unidentified catalyst from a major supplier. The electrical resistances of fresh, used and regenerated catalyst samples were measured on single particles, and specific conductivities were calculated. The difference between the conductivity of fresh and spent catalysts was found to be significant (1–5 orders of magnitude), while the conductivities of the regenerated samples were essentially identical to that of the fresh catalyst. Resistance measurements were also conducted in packed beds of the hydrotreating and basic alumina catalysts, and the concept of apparent specific conductivity was defined. The change in specific conductivity measured on single particles of fresh and regenerated catalysts, and the change in apparent specific conductivity measured in a packed bed of the same catalysts were very close. The simplicity of this new method renders it to be a potential sensitive on-line prediction method of relative catalyst activity.

N- and C-Modified TiO2 Nanotube Arrays: Enhanced Photoelectrochemical Properties and Effect of Nanotubes Length on Photoconversion Efficiency

In this investigation, a new, facile, low cost and environmental-friendly method was introduced to fabricate N- and C-modified TiO2 nanotube arrays by immersing the as-anodized TiO2 nanotube arrays (TNTAs) in a urea aqueous solution with mechanical agitation for a short time and keeping the TNTAs immersed in the solution for 6 h at room temperature. Then, the TNTAs were annealed at different temperatures. The produced N-, C-modified TNTAs were characterized using FESEM, EDX, XRD, XPS, UV-Vis diffuse reflectance spectra. Modified optical properties with narrow band gap energy, Eg, of 2.65 eV was obtained after annealing the modified TNTAs at 550 °C. Modified TNTAs showed enhanced photoelectochemical performance. Photoconversion efficiency (PCE) was increased from 4.35% for pristine (unmodified) TNTAs to 5.18% for modified TNTAs, an increase of 19%. Effect of nanotubes length of modified TNTAs on photoelectrochemical performance was also studied. Photocurrent density and PCE were increased by increasing nanotube length with a maximum PCE of 6.38% for nanotube length of 55 µm. This high PCE value was attributed to: band gap reduction due to C- and N-modification of TNTAs surface, increased surface area of long TNTAs compared with short TNTAs, investigated in previous studies.

Techno-economic Analysis of Renewable Hydrogen Production via SCWG of Biomass Using Glucose as a Model Compound

The world’s hydrogen production is around 45 million tons (500 million m3) per year, primarily derived from fossil fuels, of which about 50 % is by steam methane reforming at 800–900 °C in the presence of a catalyst (typically nickel-based). The production of hydrogen from bio-renewable sources and organic wastes is promising with respect to the environmental problems associated with fossil fuel use and reduction of dependence on the declining fossil-fuel reserves. Hydrogen can be produced by air and/or steam gasification of solid biomass or biomass-derived feedstock products or by-products (e.g. glucose, ethanol and glycerol) at temperatures above 700–800 °C with or without catalysts. Compared to conventional steam gasification or reforming processes, supercritical water gasification (SCWG) can increase the gasification efficiency, improve the hydrogen yield and reduce tar and coke formation. In addition, SCWG can utilize the wet biomass and wastes directly, eliminating the energy and capital-intensive drying process. Besides the technical challenges for SCWG of biomass in a continuous flow reactor system, e.g., the difficulty in feeding the slurry feedstock into a high-pressure system, determining economic profitability for large-scale processes is essentially needed for future commercialization of the process. This chapter presentsthe results of techno-economic analysis for production of hydrogen from glucose (a biomass model compound) and sewage sludge waste materials via SCWG. Detailed process simulation is carried out for the SCWG process evaluation with two feedstocks. Cost of hydrogen production and the revenue obtained from different feedstock are also evaluated.