Scaleup of a Single-Mode Microwave Reactor

Abstract

Widespread use of microwave technology requires quantitative scale-up models. Currently, microwave models are typical qualitative in nature. This work focuses on rendering models quantitative and elucidating the scale-up behavior of microwave heating using numerical simulations. A commonly used bench-scale microwave reactor from the CEM Corp. (CEM Discover SP) is used for benchmarking. To enable quantitative modeling, microwave heating experiments are conducted and compared to COMSOL calculations to develop a calibration curve for the set point vs the actually delivered microwave power. Using the validated computational model, microwave-heating of various liquids in a wide range of vial sizes is investigated. The computational study shows that during the scale-up, the volumetric power absorbed passes through a maximum, whereas the energy efficiency and heating uniformity exhibit strongly nonlinear behavior. This work introduces a method for quantitative microwave models and insights into the scale-up of commercial microwave reactors.

Impact of Microwaves on Organic Synthesis and Strategies toward Flow Processes and Scaling Up

“…A monomodal MW instrument is well suited for the mechanism study of the chemical reaction, but only relatively small vial diameters may receive/adsorb significant power. 12 …”

Microwave Synthetic Routes for Shape-Controlled Catalyst Nanoparticles and Nanocomposites

“…Risk reduction (health and safety) [2] Automation [9] Scalability (experimental→batch) [10] Experimental parameters Mild reaction conditions [1] Reduced reaction times [4] Precise temperature control [11] In-situ temperature and pressure monitoring [12] Lack of thermal gradients [8] Colloidal catalyst NPs Smaller size distribution [13] Spontaneous nucleation event [14] Homogeneous nucleation and growth [14] Prevention of agglomeration [7] Catalyst nanocomposites Intricate nanocomposite production [15] Monodispersed products [16] Elucidation of formation mechanisms [6] Repeatability [17] Uniform heat distribution improves product yields [18]…”

“…From its initial limitation to extraction, digestion, and organic synthesis reactions, MW chemistry has greatly diversified in scope and specialization. As demonstrated by the systems pictured in Figure 2, commercial offerings over the past several years have dramatically expanded to allow extreme temperature and pressure conditions, use of specialized atmospheres, timed reagent addition, interchangeable reaction vessels, and in situ investigations using specialized reactors [9,10,19,21,25]. The BP-210 Processing MW (Microwave Research Association, Inc.) shown in Figure 2b is a pneumatic system with pressure and vacuum sources that can create extreme reaction environments up to 1800 • C and 2200 psig [26].…”

“…FO probes can also be used for in situ pressure monitoring. [10]. Key factors such as heating uniformity and rate can vary during scale-up via mechanisms that are poorly understood, but can substantially alter operating efficiency and product yield.…”

“…Key results of the predictive computational model designed by Goyal et al included the low MW penetration depth, especially for solvents with high tan δ, and the confinement of heat generation to a narrow surface region when vessel size exceeds penetration depth [10]. Both of these factors severely limit uniform heat distribution throughout the reaction system, which represents a major barrier to scale-up.…”