Evaluation of Multipoint Dosing Strategy in a Miniaturized Tubular Reactor: Nitration of Salicylic Acid

Abstract

A 2D non-isothermal reaction engineering model for a tubular reactor was developed for a complex reaction network of salicylic acid nitration. The influence of different operating and design parameters was studied to minimize the amount of secondary nitration products and limit the maximum temperature inside the reactor. Critical temperature effects were observed for larger reaction tubes, whereas close to isothermal conditions were perceived in smaller tubes. With single-point dosing of both reactants, complete conversion can be achieved but formation of secondary nitration products cannot be avoided. For a given number of dosing points, a suitable combination of the operating parameters allowed to achieve complete conversion and better yield of the desired product.

Hydrodynamics and Selectivity Engineering of a Multipoint Dosing Flow Reactor

“…The conversion at the outlet was lower for the reactor with eight NIs than three NIs. These observations are analogous to our previous analysis a very exothermic reaction of nitration of salicylic acid . For MRs 1.4 and 1.8, the yield obtained from the reactor with eight inlets was relatively lower (14.04 and 18.07%, respectively) than the yield obtained from the three inlet scenario (23.86 and 24.42%, respectively).…”

“…The yield of such intermediates (if i.e., the desired product) depends on the relative rates of the reactions, which further depends on the concentration and the reaction temperature. A few important examples include organometallic reactions, halogenations, oxidation, nitration, and so forth. − Usually, the excess amount of one of the reagents or higher reactivity of the desired intermediate leads to side reactions. Higher conversion results in the formation of both undesired and desired products, thereby reducing the selectivity and yield of the desired product.…”

“…Distributed dosing is one of the popular ways to address this problem, where the limiting concentration of one of the reagents helps in getting better control over the selectivity of the desired product. In recent times, few such examples are reported in the literature. ,, A multipoint injection system can help to overcome this issue, where one of the reagents is dosed at multiple locations along the reactor length, leading to the membrane reactor as an extreme case . One of the main reaction parameters driving selectivity is the temperature of reactants.…”

“…Kulkarni et al demonstrated that the use of multipoint dosing of the oxidizing agent helped to minimize the possibility of over-oxidation. Similarly, the multipoint injection microreactor was used to significantly reduce secondary nitration product formation in nitration of salicylic acid …”

Kinetic Study and Intensification of Acetyl Guaiacol Nitration with Nitric Acid-Acetic Acid System in a Microreactor

“…On the other hand, the fast mixing, better control of temperature, and continuousflow mode can improve the selectivity to product and decrease the residence time to realize the intensification of nitration process [18,19]. Over the last decade, a series of nitration of aromatics have been investigated in microreactors such as phenol, salicylic acid, toluene, and benzene [20][21][22][23]. The performance is much superior to those in the traditional batch reactors.…”