Continuous chemical reactors enable ultra-turbulent mixing of reactant streams continuously. Reactant mixtures are highly pressurized and subjected to high shear in microchannels. This report explores their potential
By Irwin Gruverman
Just the Facts About CCR Technology The product classes that CCR technology can address include fine chemical manufacture including APIs, catalysts, fine coatings, injectable drugs, superconductors, fine grinding media, pigments, and ceramics.
Advantages of the technology include lower capital cost, continuous operation at high efficiency, control of stoichiometry, reliable scale-up, and control of product purity, size, uniformity, and phase purity.
New microreactors address the need for examining novel fast chemistry by miniaturizing flow channels and reaction spaces, thus reducing diffusion dimensions. These units cannot be scaled up since flow path dimensions cannot be enlarged much. Thus, scale-up requires use of many parallel microreactors, an expensive equipment cost issue that demands that uniformity and reproducibility be questioned. In addition, precipitation reactions or the presence of solids in the reacting streams cause clogging. These microreactors are operated at low pressure with resultant typical residence times of a few seconds to minutes.
Operation at elevated pressures in the 5,000 to 25,000 psi range would shorten residence time, minimize clogging problems, and enable scale-up to the kilograms/minute range in a single continuous reactor. Further, the kinetic energy in liquid streams at these pressures can be utilized to form nanostructures by stopping the high velocity streams in restricted reaction spaces, resulting in ultra-turbulent mixing at the point of reaction.
Now continuous chemical reactors (CCR) are available. These enable ultra-turbulent mixing of reactant streams continuously. Reactant mixtures are highly pressurized, are subjected to high shear in microchannels, and enter a microliter size reaction chamber at a velocity of several hundred feet/second. Shear rates exceed 106 sec-1, several orders of magnitude greater than high-speed stirring in a batch reactor or 10 times that achieved in high-pressure homogenizers. Reactant-bearing liquid structures are reduced to nanometer scale, often approaching molecular size. Diffusion resistance becomes minimal, and reaction kinetics are rapid and exclude slow side reactions. Digital control of inlet streams ensures design stoichiometry and shear levels during processing.
A CCR consists of a high-pressure mixing system capable of subjecting a reaction mixture to high pressure and shear in a very restricted reaction zone. Control of flow and stoichiometry, coupled with ultra-turbulent mixing to minimize diffusion resistance to reaction, allows continuous reaction with precise control of product characteristics.
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Figure 2: Schematic of metered coaxial feed of reactants into a processor
CCR technology can be adapted to multiplex a single high-pressure stream to interact with multiple lower pressure streams of varying composition on a continuous basis. Throughputs in the gram-per-minute range are achievable. Scale-up to 20 kg per minute can be based on the multiplex experimental results. The ability to attain linear scale-up, over a 100,000-fold throughput range, has been characteristic of the technology.
Irwin Gruverman is the CEO and chairman of Microfluidics Corp. and MFIC Corp. Microfluidics, a division of MFIC Corp., pioneered the Microfluidizer high-pressure fluids processor technology, which is used in R&D laboratories as well as pilot and production manufacturing operations. Microfluidizer high-shear processors are widely used in the pharmaceutical, biotechnology, digital ink, microelectronics, food, chemical, and personal care industries. More information is available by contacting the company in Newton, MA, at 617-969-5452 or by visiting www.microfluidicscorp.com.