Juan A. Reyes-Labarta

Catalytic pyrolysis of polypropylene using MCM-41: kinetic model

The kinetics of the thermal and catalytic decomposition of PP using different contents of an acid catalyst such as MCM-41 has been studied using dynamic thermogravimetry (TG) at a heating rate of 10 K/min, under atmospheric pressure and inert atmosphere (N2). Clear differences have been observed in the thermogravimetric behaviour of the different samples. Results obtained have shown a remarkable effect of the catalyst in accelerating the degradation processes, especially at low concentrations, and catalyst loads higher than 16 wt.% show no apparent additional effect. A quantitative kinetic model has been developed and applied and the corresponding kinetic constants have been obtained by correlating the experimental thermogravimetric data. The kinetic parameters obtained have revealed a reduction in the activation energy of the catalytic decomposition as compared to the thermal process.

Kinetic study of polypropylene pyrolysis using ZSM-5 and an equilibrium fluid catalytic cracking catalyst

Abstract The effect of the addition of ZSM-5 zeolite and an equilibrium fluid catalytic cracking (FCC) catalyst in the pyrolysis of polypropylene has been studied, using dynamic thermogravimetry at a heating rate of 10 K min −1 , with N 2 at 1 atm and using different contents of catalyst. Results obtained have shown the important effect of the presence of these catalysts—especially for the equilibrium FCC catalyst (E-cat)—in reducing the temperature of the complete degradation process as compared to the non-catalysed process. The saturating effect observed when using other catalysts such as MCM-41 was not observed when using E-cat or ZSM-5, which shows a linear tendency, with a higher decrease of decomposition temperature at higher catalyst loads. The differences between both catalysts indicate the important role of the selective matrix of the active alumina and other oxides of the FCC catalyst. A quantitative mechanistic kinetic model has been applied and the corresponding kinetic constants have been obtained by simultaneously correlating all the thermogravimetric experiments with different contents of catalyst. The kinetic parameters obtained have revealed a reduction in the activation energy of the catalytic decomposition as compared to the thermal process.

PVC modification with new functional groups. influence of hydrogen bonds on reactivity, stiffness and specific volume

Abstract The chemical modification of PVC with new bifunctional thiol compounds is reported. Aliphatic as well as aromatic reactives were tested and the influence of protic and non-protic functionalities on reactivity was studied. The chemical structure of the polymers was analyzed using 1 H NMR spectroscopy. The structural changes in the modified samples were monitored by means of density and T g determinations, which are a measure of interchain spacing and chain stiffness. While protic functionalities lead to polymers with strongly enhanced T g values indicating a considerable stiffening of the system due to physical interaction by hydrogen bonds, the softening-point temperature of PVC modified with non-protic substituents does not change very much. The interchain spacing of the polymer is not significantly altered by the presence of mobile hydrogen in the polymer.

Artificial neural network for modelling thermal decompositions

Abstract This paper introduces a new approach based on artificial neural network (ANN) to study the kinetics of thermal decomposition reactions of different polymeric materials, using dynamic thermogravimetry analysis (TGA) at several heating rates. A multilayer neural network model was trained and tested using published experimental data, allowing the proposed model a very good correlation of the weight-loss data. As an example, the same kinetic model has been applied to simultaneously fit runs performed at different heating rates, with different polymeric materials such as polyethylene, cellulose and lignin.

GE models and algorithms for condensed phase equilibrium data regression in ternary systems: limitations and proposals

Phase equilibrium data regression is an unavoidable task necessary to obtain the appropriate values for any model to be used in separation equipment design for chemical process simulation and optimization. The accuracy of this process depends on different factors such as the experimental data quality, the selected model and the calculation algorithm. The present paper summarizes the results and conclusions achieved in our research on the capabilities and limitations of the existing G E models and about strategies that can be included in the correlation algorithms to improve the convergence and avoid inconsistencies. The NRTL model has been selected as a representative local composition model. New capabilities of this model, but also several relevant limitations, have been identified and some examples of the application of a modified NRTL equation have been discussed. Furthermore, a regression algorithm has been developed that allows for the advisable simultaneous regression of all the condensed phase equilibrium regions that are present in ternary systems at constant T and P. It includes specific strategies designed to avoid some of the pitfalls frequently found in commercial regression tools for phase equilibrium calculations. Most of the proposed strategies are based on the geometrical interpretation of the lowest common tangent plane equilibrium criterion, which allows an unambiguous comprehension of the behavior of the mixtures. The paper aims to show all the work as a whole in order to reveal the necessary efforts that must be devoted to overcome the difficulties that still exist in the phase equilibrium data regression problem.

Synthesis of integrated distillation systems

Abstract The paper presents a novel superstructure based optimization procedure for design a sequence of distillation columns for separating a non azeotropic n component mixture. The separation can be performed using from conventional to fully thermally coupled distillation sequences going through all the intermediate possibilities of partial thermal integration. A two stage procedure is proposed, in the first a feasible sequence of tasks is selected, with an approximation to the total annualized cost that, under some considerations, produces a lower bound to the total annualized cost. In the second stage the configuration in actual columns is selected among all the thermodynamically equivalent configurations. A case study is presented in order to illustrate the procedure.

A Novel Hybrid Simulation-Optimization Approach for the Optimal Design of Multicomponent Distillation Columns

Poster presentado en Escape 22, European Symposium on Computer Aided Process Engineering, University College London, UK, 17-20 June 2012.

Multistage Membrane Distillation for the Treatment of Shale Gas Flowback Water: Multi-Objective Optimization under Uncertainty

Abstract In this work, we analyze the effect of shale gas well data uncertainty on the multi-objective optimization of a multistage direct contact membrane distillation (DCMD) model. The uncertain parameters, flowrate and salt concentration of the flowback water, are modelled by a set of correlated scenarios. A bi-criterion stochastic MINLP was formulated to minimize the expected total annual cost (TAC) and its variability, controlled by the worst case (WC) risk management metric. The model was solved using a modified version of the sample average approximation (SAA) algorithm, which decomposes the original problem into two: a deterministic MINLP model and a stochastic NLP model. The solution is a set of Pareto curves, where the two global extreme solutions provide the DCMD designs that achieve the minimum expected TAC and the minimum WC, respectively. Furthermore, both designs are able to satisfy the zero liquid discharge (ZLD) requirement imposed in the outflow stream.

Mathematical Programming Approach for the Design of Intensified Thermally Coupled Distillation Sequences.

Abstract In this work we present a methodology that transform insights from the conceptual design of intensified thermally coupled distillation in a set of logical expressions and mathematical models that can be integrated in a mathematical programming environment with the objective of systematically generate column sequences with a reduced number of actual columns (lower than N-1 columns, where N is the number of components). Some of the alternatives considered are Divided Wall Columns (DWC); Columns with vertical partitions, Kaibel like configurations, Elimination of transfer blocks, Extended DWC (including columns with vertical partitions) with external liquid transfer. The combination of all these alternatives provides a new rich space of alternatives, some of them not known before that should be taken into account in the design of distillation based separation systems. Some examples illustrate the procedure.

Numerical determination of distillation boundaries for multicomponent homogeneous and heterogeneous azeotropic systems

Vicepresidency of Research (University of Alicante), Generalitat Valenciana (GV/2007/125) and Ministry of Science & Innovation (PHB2008-0090-PC).