(732h) Integrating Reaction and Separation in a Thin Film Evaporator for Intensified Production of Dispersants

"Specialty chemicals are to-date largely produced in large batch reactors with typical volumes of tens to hundreds of thousands of gallons. While these batch processes are simple to operate, they are also highly inefficient. We previously demonstrated that transition from batch to continuous production can result in strong improvements in energy efficiency as well as reductions in physical footprint and capital cost. The investigations used the production of succinimide dispersants as example process. These dispersants are produced by a two-step reaction between poly-isobutylene succinic anhydride (PIBSA) and polymeric amines. The first step is an addition reaction to form a succinic amide intermediate, followed by a reversible dehydration step to produce the desired polyisobutylene succinimide product and water as byproduct. In the conventional batch process, the produced water evaporates into the head space of the reactor from where it is constantly removed via a purge stream. In contrast, in the continuous reactor water remains in the reacting stream, resulting in equilibrium limitations and necessitating a downstream drying step to obtain the dehydrated dispersant product.

We had previously identified an agitated thin film evaporator (TFE) as well-suited for drying of the highly viscous product stream. Here, we are investigating the use of the TFE as a reactive separator, i.e., using the TFE as an intensified unit in which reaction and separation occur concurrently. The TFE was first modeled by integrating previously developed reaction kinetics with mass and energy balance equations. Appropriate correlations for heat and mass transfer were identified from the literature and experimentally verified for our set-up. This performance model was then used to probe the feasibility of replacing the two-step reactor-evaporator system with a single TFE as an integrated reactive separator. The model predictions were validated experimentally in the final step. The results from our study confirm that a thin film evaporator could indeed serve as a highly intensified, integrated reactor-separator unit which is particularly well-suited for reactive processing of viscous mixtures in the presence of equilibrium limitations. "