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 degrees 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, is 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 microL each, and tracked with a temperature precision of 0.1 degrees 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 mass of polymer formed is proportional to the responses observed.

Poly(para-phenylene-cis -benzobisoxazole), PBO, is a promising thermal and fire resistant material because of its excellent thermal stability, virtual nonflammability (limiting oxygen index = 56), high char yield, and negligible smoke generation [1]. Decomposition reaction products and kinetics were studied to further characterize this material.Chemical changes in the solid film were studied by FTIR (Fourier transform infrared spectroscopy) before and after isothermal heating in vacuum. Decomposition was detected at 600°C while little, if any, was observed at 500°C. In other studies using a constant heating rate, released volatiles were identified by FTIR and an electrochemical selective ion probe.Degradation rates in nitrogen (thermal) and air (thermo-oxidative) were determined by isothermal thermogravimetric analysis (ITGA). Activation energies for the thermal and thermo-oxidative degradations were calculated. These results are compared to other thermally resistant polymers. For example, the PBO film decomposition rate is over one hundred times slower than a hightemperature-resistant polyimide (Kapton® H film) in nitrogen, and about two times slower than the polyimide film in air. These findings suggest possible lower rates of combustion, especially in situations where the polymer is decomposed in a locally oxygen starved environment.Finally, an empirical model for the thermo-oxidation of PBO was obtained

The feasibility of using continuous-flow tubular reactors (CFTR) as an efficient research tool for polymerization reactions is investigated. This is a continuation of the extensive effort that had been made at Dow in recent years to set up and employ an electro-thermal microreactor (an ohmically-heated CFTR), which resulted in several internal and external publications and a US Patent. The main focus of this work is to investigate the effect of operating conditions and flow composition, mainly the number of existing phases, on the molecular weight of the polymer. A series of polymerization experiments were performed in single-phase (liquid) and two-phase (vapor-liquid) flow regimes. In single-phase polymerization, the ethylene concentration falls continuously along the length of the reactor. This will have a significant effect on the kinetics of polymerization, particularly the molecular weight of the produced polymer. A key advantage of operating in the two-phase region is that an almost constant ethylene concentration is maintained along the length of the reactor. In effect, the vapor phase serves as a reservoir that replenishes the ethylene consumed in the liquid phase by polymerization. The molecular weight data show that this assumption is valid provided that the rate of mass transfer is significantly higher than the rate of the polymerization reaction. IntroductionThe feasibility of using continuous-flow tubular reactors (CFTR) as an efficient research tool for polymerization reactions is investigated. The simple design and versatility of these reactors make them an attractive tool for conducting research on chemical reactions. This work is a continuation of the effort that had been made at Dow to make use of an electro-thermal microreactor (an ohmically-heated CFTR). The details of the operations and applications of this reactor have been extensively reported in several internal and external publications [1][2][3]. In summary, a tubing electro-thermal micro reactor (ETMR), which was ohmically heated, was developed and used for monitoring polymerization reactions at the milligram scale. This was a new approach based on the idea of using simple 1/16 in. steel tubing as an electrical heater, a conduit for the reactant solution mixture of interest, and the tubing wall itself as a multipoint temperature sensor array. The idea was to insulate the reactor (semi-adiabatic) and monitor the temperature profiles of the reactor's different zones, assuming that more active catalysts would result in higher observed temperature rises. Several polymerization experiments using different catalysts and reaction conditions were carried out to evaluate the performance of this reactor. Although the polymerization experiments seemed to run very well, the properties of the polymer samples produced, particularly the molecular weight, were not satisfactory. In summary, the observed low molecular weights in almost all the samples were attributed to two factors: 1) non-isothermal reaction conditions, and 2) the continuous decrease i...