Nonisothermal Batch Reactor Research Articles

Tunable kinetics of nanoaluminum and microaluminum powders reacting with water to produce hydrogen

This paper reports on the kinetics and reaction processes of 40-nm and 1-μm aluminum powders with water to produce hydrogen at atmospheric pressure. This reaction produces aluminum hydroxide with irregular morphologies as by-products. It was found that the nucleation and growth of the aluminum hydroxides affect the kinetics of the reaction and thus the hydrogen production. The heat release in isothermal microcalorimetry and hydrogen production in a nonisothermal batch reactor were used to determine the rate-determining steps of the reaction mechanism and the corresponding activation energies. Model and model-free methods have been implemented to describe the reaction sequence between aluminum particle and water while the phase of newly produced aluminum hydroxide in the system plays an important role. The reaction of nanoaluminum particles and water, being more sensitive to temperature, goes to completion to produce bayerite, Al (OH)3 at 30°C, and boehmite, AlOOH at 50°C, whereas the microaluminum particles do not react completely and produce only bayerite at 30°C and also low-amount boehmite at 50°C. Nevertheless, these processes exhibit two distinct and sequential stages: a kinetically controlled stage with the apparent activation energy (Ea) of 100 to 110 kJ/mol, where nucleation and growth are limited by the chemical reactions on the surface of aluminum, and a diffusion controlled stage with Ea of 44 kJ/mol for the 40-nm Al/water reaction and 86 kJ/mol for the 1-μm Al/water reaction, where growth is limited by the mass diffusion through the aluminum hydroxide by-products. The separation of these two stages is more obvious under isothermal conditions. For nonisothermal conditions, two stages are overlapped, and the one with a lower Ea dominates.

High-Pressure Acid-Catalyzed Isomerization and Hydration of Fumaric Acid in a Homogeneous Nonisothermal Batch Reactor

A set of chemical kinetic and phase-transition experiments was performed to investigate the competing conversions of fumaric acid into maleic and malic acids by isomerization and hydration, respectively. The reactions were carried out in sealed stainless steel batch reactors operated up to ∼1600 kPa and jacketed with glycerol at 398, 423, 448, and 473 K. The catalyst used was 0.97 M hydrochloric acid. To avoid excessive data near equilibrium, the reaction time was reduced from 720000 to 12600 s as the temperature of the heating fluid was increased. To ensure a homogeneous reaction, the solubility of fumaric acid in water was determined in the temperature range from 293 to 473 K using a high-pressure variable-volume sapphire view cell. The variation in the species concentration with time was determined by HPLC analysis of 12 reaction mixture samples per reaction run conducted twice under identical conditions. The parameters of the Arrhenius equation for the isomerization and hydration reactions were tuned ...

Dynamic Response Surface Models: A Data-Driven Approach for the Analysis of Time-Varying Process Outputs

In a recent publication (Ind. Eng. Chem. Res. 2013, 52 (35), 12369) we generalized the classic design of experiments (DoE) methodology by introducing the Design of Dynamic Experiments (DoDE), allowing for the systematic design of experiments involving time-varying inputs. Here, we expand the response surface model (RSM) methodology, used in DoE and DoDE problems, so that it describes the time-evolution of the process, not just the results at the end of the experiment. We apply this generalized type of RSM model, to be denoted by DRSM, to three example processes; a nonisothermal batch reactor with a simple reaction, an isothermal semibatch reactor with several reactions, and a semibatch penicillin fermentation process. Using a limited number of online measurements at prespecified equidistant time instants, we are able to quickly and accurately represent the time evolution of the process output through these simple interpolative data-driven models. The ever-increasing availability of time-resolved measureme...

Sugar Conversion Induced by the Application of Heat to Grape Must

Two lots of the grape Trebbiano cultivar were harvested from the same vineyard 15 days apart, and their musts were cooked in an open stainless steel pan directly heated by fire; the kinetics of formation or disappearance of key constituents was then monitored for at least 16 h. From an engineering standpoint, the vessel behaved like a nonisothermal batch reactor in which the volume of the grape must necessarily decreased while its composition changed profoundly as a result of chemical reactions. Brix, total titratable acids, acetic acid, malic acid, lactic acid (d and l), pH, water activity, 5-HMF, and phenolic and radical-scavenging compounds were proposed as markers of the extent of cooking for which water vaporization and sugar degradation were identified as the two main driving factors. Acid-catalyzed dehydration was hypothesized as the predominant mechanism for sugar degradation, assuming a direct role of water vaporization; however, contributions of Maillard degradation pathways and other parallel reversible reactions were also hypothesized. Fractional conversion of 5-HMF and radical-scavenging compounds were proposed as quantitative markers for the extent of sugar degradation at, respectively, the early and advanced stages of cooking. Selectivity indices were also proposed as a performance criterion to design cooking processes in relation to sugar degradation.

Modelling of Non-Isothermal Batch Reactor Using Fuzzy Logic

In the present work, fuzzy logic (FL) has been used to model the performance of a batch reactor system and, hence, the conversion profile at varying operating conditions. The transient temperature vs. time data of exothermic reaction was taken from open literature [1] for modelling with FL. The FL model with properly chosen fuzzy sets, type of membership function and rule base relate time with temperature very well in the reactor under experimental condition. The simulated result through FL model was compared with experimental findings, mathematical model and artificial neural network (ANN) model. The FL model predictions were found to be in very good agreement with experimental findings with average absolute error less than 1%.

Optimal policies for BMA polymerization in nonisothermal batch reactor

AbstractIn this paper, the optimal policies for bulk polymerization of n‐butyl methacrylate (BMA) are determined in a nonisothermal batch reactor. Four objectives are realized for BMA polymerization based on a detailed process model. The objectives are: (i) maximization of monomer conversion in a specified operation time, (ii) minimization of operation time for a specified, final monomer conversion, (iii) maximization of monomer conversion for a specified, final number average polymer molecular weight, and (iv) maximization of monomer conversion for a specified, final weight average polymer molecular weight. For each objective, the optimal temperature policy of heat‐exchange fluid inside reactor jacket is determined. The temperature of the heat‐exchange fluid is considered as a function of a specified variable. Necessary equations are provided to suitably transform the process model in terms of a specified variable other than time, and to evaluate the elements of Jacobian to help in the accurate solution of the process model. A genetic algorithm‐based optimal control method is applied to realize the objectives. The resulting optimal policies of this application reveal considerable improvements in the batch production of poly(BMA). © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2799–2809, 2006

Optimal control determination of MMA polymerization in non-isothermal batch reactor using bifunctional initiator

In this work, we determine the optimal control for free-radical methyl methacrylate polymerization using a bifunctional initiator in a non-isothermal batch reactor. A detailed unsteady-state model of the process is employed. Four different optimal control objectives are realized, each of which optimizes a given variable simultaneously with the specification of another. The first two objectives involve the maximization of monomer conversion in a specified operation time, and the minimization of operation time for a specified, final monomer conversion. The last two objectives involve the maximization of monomer conversion for specified, final number and weight average polymer molecular weights. The temperature of heat-exchange fluid inside reactor jacket is considered as a control function of an independent variable. To meet the specification of an optimization variable other than time, the differential model of batch process is derived in the range of specified variable. Equations are provided for Jacobian evaluations to help in the accurate solution of process model. A genetic algorithms-based optimal control method is applied to realize the four optimal control objectives. The results show that optimal control can significantly enhance the performance of the batch polymerization process.

Evaluations of kinetic parameters and critical runaway conditions in the reaction system of hexamine-nitric acid to produce RDX in a non-isothermal batch reactor

Abstract In the production process of RDX from the reaction of hexamine and nitric acid, its reaction rate was evaluated and expressed as −r A =1.234×10 6 e −5671.062 T C NO C 1.28 A , where T is the reaction temperature, CA is the concentration of hexamine and CNO is the initial concentration of added nitric acid. The critical condition of runaway reaction for the RDX production in a batch reactor is φc=20.437−4.805/[1+exp(336.7β−15.65)]. Its heat transfer coefficient at critical runaway condition was also estimated and expressed as (hS/V)cr=(RqgACNOCnAO)/(Eβ2e1/βφC).

The stability of toluene mononitration in reaction calorimeter reactor

The kinetic parameters of toluene mononitration's reaction was measured using a reaction calorimeter (RC1) with an isothermal mode. These measured kinetic parameters were used to predict the theoretical transient temperature and fractional conversion simultaneously. The formulae for the evaluation of stability criterion in the toluene mononitration's reaction system in a non-isothermal batch reactor were derived from both transient mass and heat transfer equations. These stability-predicting formulae are explicitly expressed as a function of temperature, fractional conversion, physical properties and kinetic parameters. We then evaluate its criterion of stability using the derived equations and measured kinetic parameters.

資源変換用非等温回分反応器によるイルメナイト鉱石の硫酸蒸解プロセス解析

資源変換用非等温回分反応器によるイルメナイト鉱石の硫酸蒸解プロセス解析

Polymerization of styrene with n‐butyllithium in a batch reactor. A mathematical model

AbstractSytrene was polymerized in a 0.8‐liter vessel which was operated as an isothermal and a nonisothermal batch reactor. Styrene and n‐butyllithium conversions were determined for different reaction times. Rate equations were developed by use of the isothermal data and then used to estimate the conversions for the nonisothermal experiments. The importance of using nonisothermal data in the development of rate equations is illustrated.