Zoran Gomzi

Polydispersity index and molecular weight distributions of polymers

The polydispersity index as a measure of the width of molecular weight distributions (MWD) is theoretically very important. However, considering MWDs of real polymers, its importance is partly lost. Consequently, several problems arise. The most common one is the misinterpretation of polydispersity index as a single and unique measure of the MWD width. In this work, the origin and solutions of the problem are clearly described via several theoretical distribution functions, i.e. those which are most widely applied for the description of polymer MWDs. The conclusions are confirmed by the analysis of MWDs of real samples, namely styrene-acrylonitrile copolymers. In addition, a complete procedure for the MWD data analysis is presented. Such a procedure is necessary for the correct interpretation and comparison of different, experimentally obtained, molecular weight distributions of polymers.

Catalytic reduction of NOx over Cu/ZSM-5 catalyst

Catalytic decomposition of NO on Cu/ZSM-5 catalyst was carried out in tubular fixed-bed reactor at atmospheric pressure. The influence of temperature and flow rate on the reaction rate was investigated. The kinetic model of reaction was proposed and compared with the literature results. The formation of NO2 during the catalytic decomposition of NO was also monitored. Therefore, additional experiments were performed aimed at examining the kinetics of NO oxidation under the same reaction conditions. Both kinetic models were used to develop the reactor model and to describe quantitatively the behavior of the overall reaction system. Satisfactory degree of correlation between experimental data and values predicted by reactor model has been achieved.

Experimental and theoretical study of NO decomposition in a catalytic monolith reactor

Abstract The objective of this study was to prepare zeolite-based monoliths (Cu/ZSM-5 on cordierite), to test their catalytic activity in the direct decomposition of nitrogen monoxide and to develop mathematical model of the monolith reactor. Reaction of NO decomposition was performed over the monolith catalysts with various thickness of the catalytic washcoat, in temperature range from 573 to 773 K, under atmospheric pressure and at various space times. Two-dimensional heterogeneous model is applied to describe a single channel of the monolith reactor. Langmuir–Hinshelwood type of kinetic model is considered. The influence of both inter- and intraphase diffusion on the performance of the monolith reactor is quantitatively described by means of the governing effectiveness factors. The mean and local gas–solid mass transfer coefficients are derived from the concentration gradients using the proposed model. The proposed model is verified by comparing computer simulation data with experimental laboratory results.

Swelling kinetics of polymer-solvent systems

Abstract Swelling of poly(ethylene-co-vinyl acetate) (ESCORENE UL 00218, EXXON Chemicals, Belgium) in solvents of different types has been carried out by the volumetric method at three temperatures. The swelling kinetics are related to the swelling rate constants. A new variable, α′, is introduced and defined for comparing kinetic parameters in various polymer-solvent systems. A kinetic model of a reversible first order process was taken as a theoretical model because of the best fitting of experimental data to this model. The solvents are considered from the kinetic (swelling rate constants as indicators) and thermodynamic (equilibrium swelling degree as indicator) points of view. Poly(ethylene-co-vinyl acetate) interacts with solvents mainly by dispersive forces, but the kinetics of swelling may also be affected by other factors, such as the viscosity and molar volume of the solvent.

Modelling of Composting of Food Waste in a Column Reactor

The composting of organic solid waste, the mixture of fruit and vegetable leftovers enriched with night soil, was investigated in a closed thermally insulated reactor. It was found that 80.9 % of the original substrate biodegraded after 14 days. A mathematical model of the column reactor was proposed where the biodegradation rate of the organic solid waste was described using simple n-thorder kinetics. A good prediction of process performance was obtained using the proposed kinetics and experimentally obtained reaction heat.

Reaction and Mass Transfer Effects in a catalytic monolith reactor

Zeolite-based monoliths (Cu/ZSM-5 on cordierite) are prepared and used to catalyze direct decomposition of nitrogen monoxide. Two-dimensional heterogeneous model is applied to describe the behavior of the monolith reactor, with the emphasis on the features introduced due to coupling of flow, mass transfer and chemical reaction. The proposed model has been verified by comparing computer simulation data with laboratory experimental data. It is shown that both inter- and intraphase diffusion limitations have to be considered when modeling complex reactor configuration, such as monolith reactors, especially when monolith with thicker catalytic layer are used at higher temperatures.

Esterification of sorbitol and lauric acid with catalystp-TSA

Kinetics of the esterification of sorbitol with lauric acid in the presence ofp-TSA as a catalyst has been studied. A kinetic model of reversible second order reaction was proposed for the esterification. Parameters in the model (kinetic constants) were estimated by non-linear regression. The temperature dependence of the rate was calculated from the experimental constants estimated at various temperatures, using the Arrhenius equation. Experimental results are in good accordance with the proposed theoretical model.

Software sensors for monitoring of a solid waste composting process

Process identification for composting of tobacco solid waste in an aerobic, adiabatic batch reactor was carried out using neural network-based models which utilized the nonlinear finite impulse response and nonlinear autoregressive model with exogenous inputs identification methods. Two soft sensors were developed for the estimation of conversion. The neural networks were trained by the adaptive gradient method using cascade learning. The developed models showed that the neural networks could be applied as intelligent software sensors giving a possibility of continuous process monitoring. The models have a potential to be used for inferential control of composting process in batch reactors.

Cure modeling of polyester thermosets in the copper mold

Abstract The cure of unsaturated polyester was studied experimentally and by using a model of the process. The kinetic parameters were calculated from the heat flow–time curves obtained by differential scanning calorimetry (DSC, Netzsch—Simultaneous Thermal Analyzer DSC 200), working in DSC (dynamic) mode. The temperature–time histories were studied in a cylindrically shaped copper mold. Taking into account the heat transferred due to conduction through the resin, as well as the kinetics of heat generated in the cure reaction, a numerical model was constructed. The contributions to the rise in temperature from heat conduction and chemical reaction are different in different parts of the composite, which can explain the temperature–time, or conversion–time histories. Introduction of a carbon-base filler reduced the amount of heat released in the composite and, as a result, lowered the temperatures through the resin. Finally, a good agreement between experimental data and the predicted mathematical model of the curing process in the mold was observed.

Kinetics of no decomposition over Cu/ZSM-5 catalyst

AbstractThe kinetics of catalytic decomposition of NO over Cu/ZSM-5 catalyst has been studied in an integral flow reactor at atmospheric pressure. Kinetic analysis is based on the assumption that the surface reaction represents the rate-determining step. On the basis of theoretical considerations of different interactions between reactants and catalyst, and experimental evidences, three different mechanistic kinetic models were chosen. Also a power-law model was tested. The best agreement has been achieved with the model