Safe operating conditions for semibatch processes involving consecutive reactions with autocatalytic behavior

2016

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In this work the general Ψ number criterion for the safe operation of semibatch runaway reactions has been applied to the optimization of a nitration process of primary importance in the agrochemical industry, that is the nitration through mixed acids of 4-chloro benzotrifluoride to produce a widely employed class of fluorinated herbicides. Such a reaction, as almost all the organic nitrations, belongs to the most critical class of exothermic reaction processes, for which the maximum temperature of the synthesis reaction under adiabatic conditions overcomes the decomposition temperature of the system, without any tempering effect due to a solvent evaporation. It has been verified that higher productivity operating conditions can be easily implemented through the general Ψ number criterion, even without a kinetic characterization of the system, but just elaborating information already available at the laboratory scale, where the chemical recipe is developed. The results obtained have been further validated through the boundary and temperature diagrams criterion, which however requires a previous estimation of the reaction kinetic parameters, with a much higher experimental effort.

Section: Introductionmentioning

confidence: 99%

Kinetic-Free Safe Optimization of a Semibatch Runaway Reaction: Nitration of 4-Chloro Benzotrifluoride

2016

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“…Along the same line presented in the literature [3][4][5][6][7][8][9]28 , a weighted average coolant temperature can be defined as:…”

Section: Mathematical Modelmentioning

confidence: 99%

Enhanced Heat Transfer for Isoperibolic Semibatch Reactors: A Kinetic Free Sizing Criterion

Rossi

2019

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Whenever the productivity of an indirectly cooled, isoperibolic semibatch reactor (SBR) must be enhanced keeping the reaction temperature nearly constant, an additional heat transfer surface with respect to that provided by the reactor jacket only must be installed. In these cases, internal coils are normally adopted, which additional surface is however intrinsically limited and not fully available since from the beginning of the supply period. However, a suitable fraction of the overall heat transfer surface can be installed on an external reactor recycle loop: this allows also for a simpler monitoring of the reaction system by comparing the measured temperature to a nearly constant target value. In this work a kinetic-free sizing criterion has been developed for isoperibolic SBRs (both homogeneous and heterogeneous), through which the required external heat transfer surface can be easily estimated.

“…Since a chemical reaction is the result of collisions between the reactant molecules of sufficiently high energy and effective orientation, a reaction rate equation can be expressed as the product of a probability factor, of an energy factor and of a concentration factor 28 . Comparing Equations (10) and (11) it can be noticed that:…”

Section: Reaction System Characterizationmentioning

confidence: 99%

“…In the process safety literature of the last decades several short-cut criteria have been developed to identify safe and productive operating conditions of exothermic semi-batch reactors (SBRs) without solving the mathematical model of the system, therefore saving a considerable amount of time [3][4][5][6][7][8][9][10][11] .…”

Section: Introductionmentioning

confidence: 99%

Simple Monitoring of Fine Chemical Runaway Reactions in Multipurpose Plants: Nitration of 2,4-Dichloro Benzotrifluoride

Curti

2018

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In the fine chemical industry new production processes are often implemented in multipurpose existing plants with minimum adaptation investments. When the new process involves a potential runaway reaction, a full thermodynamic and kinetic characterization of the system should be performed to evaluate whether the reaction can be safely scaled-up in the selected plant. However, a detailed kinetic characterization is often unsuited because of the huge development rate of new products. In this work a potential runaway reaction of the agrochemical industry, that is, the nitration of 2,4-dichloro benzotrifluoride through mixed acids, is investigated with the aim of implementing it with a minimum experimental effort in an existing plant already dedicated to a similar reaction, that is, the nitration of 4-chloro benzotrifluoride. It has been shown that, even performing very similar reactions, the Ψ number criterion cannot be implemented in a univocal way to monitor the multipurpose SBR operation. Such a goal can instead be reached through the general procedure based on the Ψ, X and MTSRad set of process indicators, which was previously applied to the monitoring of polymerization processes.