Safe and Productive Operation of Homogeneous Semibatch Reactors. I. Development of a General Procedure

2016

Ind. Eng. Chem. Res.

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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

Ind. Eng. Chem. Res.

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“…For these reasons, in order to make the mass balance approach of general application, a number of boundary diagrams should be developed, along the line presented elsewhere in the literature for the safe operation of SBRs in which exothermic reactions are performed (see for example Maestri and Rota (2005a, 2005b, 2006). …”

Section: Reactor Optimizationmentioning

confidence: 99%

“…t/t dos , dimensionless time, -κ k/k R , dimensionless reaction rate constant, -ρ molar density, kmol/m 3 σ molar selectivity, -τ V r /Q, average residence time in the reactor, s χ (n B0 À n B )/n A1 , normalized conversion, -of the reactions involved and the development of a number of boundary diagrams for different reaction order kinetics as well as the identification of rules of thumb for their simplified and safe use, along the line presented elsewhere in the literature (Maestri and Rota, 2005a, 2005b, 2006. However, in this case such an approach is rather complicated, since more than one reaction occurs in the system (at least, the main one and an undesired one) and different combinations of the involved kinetic parameters should be considered.…”

Section: Introductionmentioning

confidence: 99%

Kinetic-free selectivity control of chemical reactions leading to nonvolatile products

Chemical Engineering Science

2015

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A number of reaction processes of the fine chemical and pharma industry undergo selectivity losses, since the target product (often a low volatility compound) can be further consumed by a nonselective reactant, according to a mixed series/parallel kinetic scheme.\ud \ud In these cases, performing the reaction in a semibatch recycle reactor (SBRR) allows achieving both a high process selectivity and productivity even in a noncontinuous plant, since the target product concentration in the reactor can be limited adopting a relatively low excess of the selective reactant.\ud \ud In the literature, on the basis of a mass balance approach, a number of boundary diagrams have been developed that allow to predict selective and productive operating conditions for SBRRs in which (1,1) order reactions occur.\ud \ud However, when dealing with fine chemical and pharma reaction processes, the estimation of the kinetic parameters is often not practicable, due to the huge variety of productions encountered.\ud \ud In this work a criterion has been developed that allows for identifying the optimal operating conditions of SBRRs without knowing the kinetics of the reactions involved.\ud \ud The criterion has been applied to a reaction process of industrial interest performed in a SBRR, that is the production of ethylene glycol from ethylene oxide, with further ethoxylation of the desired product to diethylene glycol

“…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

Ind. Eng. Chem. Res.

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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.