Sensitivity of methanol-to-olefin reaction to axial gas dispersion: Determination in a vibrated-bed microreactor.

摘要

A microreactor has been developed to study the sensitivity of Methanol-To-Olefin (MTO) reaction to axial gas dispersion. It comprises a rectangular horizontal duct, 12.7 mm in height, 25.4 mm in width, variable in length, charged with a 1-mm-deep layer of HZSM-5 catalyst. The microreactor is constructed of aluminum alloy and heated with cartridge heaters. A glass reference duct with the same catalyst loading is mounted directly above the microreactor to provide visual check of the coherent-expanded vibration state achieved by vibrating the setup at 24 hertz and 4.3-mm vertical displacement. In this state, catalyst powder expands to full duct height during a portion of each vibration cycle, with intense vertical mixing of powder and little horizontal.; Axial gas dispersion coefficient varies linearly with superficial gas velocity, and axial Peclet Number (Pe{dollar}sb{lcub}rm ax{rcub}{dollar}) can be studied over a wide range of values simply by varying duct length while holding weight hourly space velocity constant.; Conducting the MTO reaction in microreactors of 7.62-, 15.24-, and 22.86-cm length (Pe{dollar}sb{lcub}rm ax{rcub}{dollar} = ca. 2, 9, and 19 respectively) revealed the reaction to be sensitive to axial gas mixing. Trend in light olefin yield versus Pe{dollar}sb{lcub}rm ax{rcub}{dollar} agrees with earlier turbulent fluid-bed data. Loss in olefins with increase in axial gas dispersion (decrease in Pe{dollar}sb{lcub}rm ax{rcub}{dollar}) suggests that a circulating fluid bed may be the preferred reactor for this reaction.; Researchers can use the microreactor to determine, quickly and inexpensively, how reaction outcomes vary with axial gas dispersion. The microreactor could help R&D managers to avoid expense of a fluid bed R&D effort where an economically significant outcome of a reaction is acutely sensitive to axial gas dispersion, and where a fixed bed is an acceptable alternative.