Fused Silica Capillary Reactor and Its Applications

Abstract

The “fused silica capillary reactor” (FSCR) was constructed from fused silica capillary (normally 0.665 mm OD, 0.3 mm ID, and about 25 mm long) with both ends sealed by fusion in an oxyhydrogen flame after the sample in solid, liquid, or gaseous form (or their mixtures) was loaded. The fused silica is stable in aqueous solutions with low pH and the FSCR can hold 100 MPa internal pressure or slightly higher. Two types of customer-designed heating-cooling stages were used to control sample temperatures between −196 and 600 °C and also the heating and cooling rates (0.1 °C/min to 50 °C/min) of the sample. The volume of the FSCR expands elastically up to 75 % when heated to about 400 °C from room temperature. The FSCR is highly permeable to hydrogen and provides the potential for developing experimental methods for redox control in reactions at room temperature or higher. Because the fused silica is stable in aqueous solutions with low pH, and inert to sulfur, FSCR is an ideal container for experiments of many chemical systems at the pressure-temperature conditions near the critical point of water. The transparency of the fused silica allows in situ optical observations of the sample under a microscope, spectroscopic analyses (e.g., Raman spectroscopy), and continuous recording of the sample during heating or cooling for later reviews and kinetic studies. Examples are given for the applications of FSCR in the studies of material in water at conditions near the critical point of water.