Topological Criteria to Safely Optimize Hazardous Chemical Processes Involving Consecutive Reactions

Abstract

Safe operating conditions, for strongly exothermic chemical systems involving multiple reactions, are particularly critical to be obtained, because of the complex interactions between selectivity and safety constraints. In this work, new criteria, which are useful for isoperibolic semibatch processes involving consecutive reactions and based on the topology of a particular phase space, are presented. Such criteria are able to detect both the runaway boundary and the so-called "quick onset, fair conversion, smooth temperature profile" (QFS) operating region by performing a topological analysis of the phase space of the system of ordinary differential equations (ODEs) that describe the analyzed process. Moreover, a safe optimization procedure, the objective of which is to obtain the optimum values both of the dosing time of the dosed reactant and the initial reactor temperature, based on such criteria, has been developed. Finally, such a set of optimum operating parameters has been validated through a comparison with experimental data from published literature.

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

“…On this basis, a number of safety criteria have been developed in the last 30 years, through which safe and productive operating conditions of an exothermic semibatch reactor (in the following referred to as SBR) can be determined, without solving the mathematical model of the reactor [1][2][3][4][5][6][7]9,[11][12][13][14][15][16][17][18][19] . However, since they are based on the aforementioned comparison between coreactant dosing time and reaction characteristic time, a previous kinetic characterization of the system is required, which is often difficult to perform when dealing with multipurpose processes of the fine chemical and pharmaceutical industry 10 .…”

Safe and Selective Monitoring of Consecutive Side Reactions

“…As expected, under safe and selective operating conditions (Figure 2) both conversion and yield time profiles are close to each other and the SBR temperature quickly approaches the target C profile expressed by Eq. (16). In this case the X parameter (shown in Figure 2C) quickly approaches the required value equal to 100.…”

Emulsion polymerization of vinyl acetate: Safe optimization of a hazardous complex process

“…The topological criterion theory [8,9] states that, for a semibatch process carried out under the isoperibolic control mode, the boundary between runaway and "Quick onset, Fair conversion, Smooth temperature profile" conditions with respect to a desired product (QFS [10,11]) is identified by an inversion of the topological curve showing a concavity towards right. Particularly, this curve shows all the possible thermal behavior regions of an isoperibolic SBR obtainable by varying one system constitutive parameter (in the polymerization case, the dosing time) in a suitable range.…”

“…for isoperibolic processes a lower solids content, usually 30-35%, is preferred). In this work, the topological criterion theory [8,9] has been used to safely optimize the free radical emulsion homopolymerization of vinyl acetate (VA) thermally initiated by potassium persulphate (KPS). Particularly, an indirectly cooled semibatch reactor (RC1, 1 L, Mettler Toledo) operated in the isoperibolic control mode (which is simpler to realize in an industrial plant than the isothermal one) has been chosen for the laboratory experiments.…”