Methanol dehydrogenation to formaldehyde could become a key step in the environmentally benign synthesis of several important chemicals. This reaction was studied in a slurry reactor using Raney copper as the catalyst and 1,2,3,4-tetrahydroquinoline as the slurry liquid under pressures up to 2.75 MPa and at temperatures between 573 and 648 K. The dehydrogenation of methanol to formaldehyde was found to be near equilibrium at 598 K. There was no evidence of significant catalyst deactivation at 598 K, but deactivation occurred at higher temperatures. Methyl formate was the main product, presumably due to formaldehyde dimerization. Some formation of carbon monoxide was also observed. There was considerable alkylation of the slurry liquid.