Challenges and Innovations in Reaction Engineering

Abstract

The importance of reaction engineering in generating a myriad of products on which developed societies depend is outlined. The challenges of a political, economic, and technical nature that need to be addressed in rendering conversion of raw materials into desired products that are more environmentally friendly and sustainable are briefly discussed. It is shown that multiphase reactors are prevalent in all applications, and improvements in the reactor material and energy efficiencies lead to more environmentally benign processes. This requires, in addition to the selection of green process chemistry, systematic implementation of the multi-scale reaction engineering methodology to accomplish proper reactor type selection and scaleup for commercial applications. It is also illustrated that recent innovations in multiphase reaction engineering basically utilize two key concepts: process intensification (e.g., enhancement in mass and heat transfer rates) and simultaneous reaction and separation. Examples of these are discussed, such as micro-reactors, reactive distillation, etc. It is also shown that commercialization of bench-scale discoveries requires either scaleup in parallel or vertical scaleup. New tools for visualization of opaque multiphase flows and development of appropriate rational phenomenological multiphase reactor models for scaleup and design are also briefly discussed.

Temperature Homogeneity under Selective and Localized Microwave Heating in Structured Flow Reactors

“…Greener chemical manufacturing technologies can combat climate change . Electromagnetic energy generated from renewable sources is one such technology that can simultaneously enable process intensification and sustainable electrified chemical manufacturing. − Electromagnetic radiation, including microwaves, can be deposited volumetrically ,− and overcome heat transfer limitations occurring when the reactor is heated by an external energy source. − Importantly, microwave heating is also selective due to difference in permittivity of materials. For example, microwave absorbing solids, such as silicon carbide (SiC), absorb and dissipate the electromagnetic energy much more efficiently than “transparent” fluids, such as air.…”

The concept of selectivity control by simultaneous distribution of the oxygen feed and wall temperature in a microstructured reactor

“…Complementary to developing more selective catalysts and process chemistry is the reactor engineering approach, using the already available reaction routes and catalysts [19,20]. Many gasphase selective oxidations are strongly exothermic and are, typically, carried out in multi-tubular packed bed reactors with external cooling.…”

Cyclic Operation Strategies in Trickle Beds and Electrical Capacitance Tomography Imaging of Filtration Dynamics

“…The ECT sensor was calibrated at drained prewetted-bed (0% reference) and at floodedbed conditions (100% reference) whose corresponding per-pixel mixture permittivities are, respectively, Similarly, in two-phase flow operation, the corresponding permittivity writes as In eqs 1-3, e, e l res , and e l fd , represent, respectively, the bed porosity, the residual liquid holdup due to capillary forces, and the free-draining liquid holdup, whereas, ε s , ε l , ε g , are, respectively, the packing (bed element), liquid, and gas electrical permittivities. Therefore, the normalized permittivity, NP, formed as [(3) -(1)]/[(2) -(1)], gives rise to the free-draining liquid holdup normalized by the "effective" void space after resting the residual liquid holdup: Drained-bed permittivity ε [0] ) (1e)ε s + e l res ε l + (ee l res )ε g (1) Flooded-bed permittivity ε [1] )…”

“…Any conversion process aims at maximizing the volumetric productivity for a target value-added product conditionally to minimization of (atom, material, and energy) resources utilization and waste production. 1 Improvements, even minute ones, targeting reactor selection and/or its operating conditions are usually dubbed as process intensification. Often, prior to opting for radical measures such as replacing an existing reactor by "a would-be better one", altering reactor operating modes by the process operators, when this is permitted, is the least troublesome of ways to seek improvements.…”