Advanced Microreactors Make Chemical Processing Safer, Faster
Until recently, chemical processing typically involved the use of conventional processing equipment that held relatively large amounts of materials in relatively large reactor vessels. If the reactions being performed were highly exothermic, the possibility of runaway reactions leading to fires or explosions was high. The primary reason for this was the inability to extract the heat generated by the reaction due to the large ratio of the material volume to surface area of the chamber walls. This could cause difficulty in controlling temperature and other process conditions, detrimentally affecting the chemical process. For example, in conventional tank reactors where temperatures at the reactor walls could be well-controlled, the portions of reactants away from the walls might experience different temperature ranges; this could negatively affect the reaction, generating undesirable by-products and waste materials and increasing the potential for dangerous adverse reactions. But if the surface area was increased dramatically in relation to the amount of material used, temperature can be more precisely controlled so that the success of the process would be increased substantially. To do this required rethinking how reactors are designed.
DuPont has tackled the problem and come up with this technology: the advanced microreactor. With an average size no larger than a hockey puck, DuPont´s microreactor is fabricated from layers of wafer-like disks with precise interior channels formed on the disk surfaces to contain the reactions. Each microreactor is an integrated system designed to perform a specific process including mixing, heat exchange, catalysis, reaction, photoreaction, electrochemical, separation, and analysis/control of reactions involving gases, liquids, as well as multiphases.
The materials used for the layers are determined by the chemical processes to be performed, but are generally from groups III, IV, and V of the Periodic Table, including ceramics, glasses, polymers, composites, and metals. The channels within these layers -- measuring a mere 10 to 5000 micrometers across and connected to the inlet and outlet ports -- are formed by any number of techniques depending on the material used: chemical etching, electrochemical machining, laser machining, electroforming, selective plating, chemical vapor deposition, photoforming, molding, casting, and stamping.
Safety, Versatility Are Major Benefits
Among the many benefits derived from microreactors, safety is a major one. Chemicals that are dangerous to manufacture, handle, ship, or store can be produced in small quantities on-site, as needed. Many processes require fast mixing of reactants, which can be difficult to achieve with large volumes of materials. Microreactors promote faster mixing through their small-diameter channels, which also prohibit flame propagation which can lead to explosions. Rapid mixing facilitates better kinetic reaction data, enabling better and faster optimization of conventional production reactors.
The very nature of the microreactors makes them versatile and relatively inexpensive to use. Their small size requires small amounts of reactants while the laminae used to construct the reactors can be held together by a variety of methods, including epoxies, soldering, welding, even clamping.
The relatively large surface areas in the reactors enables a wide range of controls to be incorporated in the devices, including temperature, pressure, and pH sensors, heating elements, flowmeters, and other instrumentation. The size and versatility of these microreactors make them ideal for lab bench processes as well as volume production in which dozens, even hundreds, of devices can be operated in parallel to produce potentially millions of pounds of chemicals a year.