(62a) Novel Tubing Microreactor for Monitoring Chemical Reactions

There is an expanding interest in small-scale methods to evaluate catalysts and chemical reactions at a variety of conditions, ranging up to 6.9 MPa (1000 psig) and 300 °C. Multiwell parallel batch techniques are most commonly applied in high-throughput screening systems. In contrast, we describe here a rapid, serial, highly controllable method based on LC-type steel tubing rated for high pressures. The tube, containing a variety of flowing ingredients, such as carrier solvents, catalyst formulations, and reactants can be heated by either immersing in an oil bath or self-heated ohmically using electrical current from a power supply monitored and regulated with a precision of 0.01%. An array of voltage taps arranged along its length serves to sense the real-time temperature profile of the tube. Reactions are seen as temperature pulses progressing through the reactor, in zones of 200 µL each, and tracked with a temperature precision of 0.1 °C. A unique pressure controller was devised to maintain constant reactor pressures despite effluent viscosity fluctuations due to polymerization.

Several chemical reaction systems have been characterized to date, including decomposition reactions of di-tert-butyl peroxide, polymerizations of styrene, formation of polyethylene from ethylene, and copolymerization of ethylene with 1-octene. For ethylene polymerization, the amount of the mass of polymer formed is proportional to the responses observed.

Also explored were alternative modes of operation to simulate other types of reactors, for example, a semi-batch reactor. Unlike a semi-batch reactor, tubular reactors are in nature similar to batch systems where the concentration of monomer declines along the length of the tube. Operating conditions of the tubular reactor were modified from single-liquid to gas-liquid phase. This simulates semi-batch operation where the ethylene in the gas phase replenishes the ethylene consumed in the liquid. As expected, significantly higher molecular weights were obtained in the two-phase versus single-phase experiments.