Liquid/catalyst interactions in slurry reactors: methanol synthesis over zinc chromite

Abstract

The performance of a `zinc chromite' catalyst was studied in a continuous slurry reactor using three different liquids: decahydronaphthalene, tetrahydronaphthalene, and tetrahydroquinoline. The reactor feed was a mixture of hydrogen and carbon monoxide with a H 2/CO ratio of either 0.5 or 2. The reactor was operated over a temperature range of 598–698 K and at a total pressure of about 14 MPa. The characteristics of the slurry liquid had a major influence on both the overall reaction rate and the product distribution. The rate of methanol synthesis was much higher when tetrahydroquinoline was used than with the other two liquids. The product distribution was shifted away from oxygenates and towards hydrocarbons when tetrahydronaphthalene was used. The slurry liquid was analyzed by GC/MS (gas chromatography/mass spectrometry) during and after the reaction. There was no evidence of significant cracking or hydrocracking of any of the liquids. However, tetrahydroquinoline was alkylated during the reaction, and tetrahydronaphthalene was dehydrogenated to some extent. Tetrahydroquinoline, and perhaps tetrahydronaphthalene, may have participated in the catalytic cycle.