Cold model of a vibrated-bed microreactor capable of varying Peclet number at fixed weight hourly space velocity providing a tool for simulating an important feature of the reaction kinetic scene in large catalytic fluid beds

Abstract

A cold-flow model of a vibrated-bed microreactor has been designed and tested with capability for varying the level of gas dispersion (characterized by axial Peclet number) at a fixed weight hourly space velocity (WHSV). A tool has thus been provided whereby an important feature (viz., gas dispersion) of the reaction kinetic scene in large catalytic fluid beds can be simulated on a microscale, using approximately 5 grams of catalyst.

Realization of a hot design of the microreactor (a task for another student) should permit the industrial chemist or chemical engineer, working at laboratory bench scale, quickly and inexpensively, to determine the sensitivity of a cataly1ic reaction to fluid-bed gas dispersion.

The new microreactor exploits the coherent-expanded (C-E) vibrated-bed state, and is perhaps the first technical use of this state. The C-E state is achieved by subjecting a shallow layer of a fine powder to vertical sinusoidal vibration. The microreactor comprises a rectangular horizontal duct, 12.7 mm in height, 25.4 mm in width, variable in length, and with nonporous floor and walls. The microreactor is charged with a powder, such as fluid cataly1ic cracking (FCC) catalyst, at a compacted depth of I mm, and is vibrated at ~15 Hertz and amplitude of ~3 mm. Under influence of this vibration, the powder expands, displaying the C-E state. Between a phase angle of ~50° and an angle of ~150°, the powder assumes a depth of ~4 mm (i.e., expanded 4-fold from its compacted depth). Later, in each vibration cycle, the powder expands further. At ~300° phase angle, the powder reaches ~12.7 mm (i.e., collides with the roof of the microreactor duct).