Methanol dehydrogenation in a slurry reactor: evaluation of copper chromite and iron/titanium catalysts

The dehydrogenation of methanol to formaldehyde is a cornerstone in the con cept of environmentally-benign synthesis through in situ generation of form aldehyde. This reaction was studied in a slurry reactor at temperatures bet ween 598 and 673 K over four different catalysts: Raney copper, copper chro mite, 3% Mn/copper chromite and iron/titanium (FeTi) alloy. The three coppe r-based catalysts were effective at promoting methanol dehydrogenation, and the differences in activity and selectivity between these catalysts were r elatively small at 598 K, 2.75 MPa, 10/l N-2/methanol feed ratio, and 12,00 0 sL/kg-hr space velocity. At these conditions, methyl formate was the prim ary product with the copper catalysts, and the formaldehyde concentration w as near chemical equilibrium with Raney copper and 3% Mn/copper chromite. T he FeTi catalyst was ineffective on a weight basis, although its activity w as comparable to the copper catalysts on a surface area basis. Deactivation of the copper chromite catalyst was relatively slow at 673 K, after an ini tial period of stabilization. The slurry liquid, 1,2,3,4-tetrahydroquinolin e (THQ). was dehydrogenated and alkylated to some extent during the reactio n. (C) 2000 Elsevier Science B.V. All rights reserved.