The effects of reaction conditions on the synthesis of isobutanol and methanol from syngas over Zr-K and Zr-Mn-K catalysts have been investigated, with the reactions carried out at pressures between 8 and 16 MPa, temperatures between 380 and 440 degrees C, and gas hourly space velocity (GHSV) between 3000 and 8000 h(-1). It was Found that the Zr-K catalyst exhibited the highest activity and selectivity at 420 degrees C, 10.0 MPa, and 5000 h(-1), and that the Mn-promoted catalyst increased the yield of isobutanol with the corresponding optimum temperature being 400 degrees C. Moreover, the higher pressure and GHSV favored isobutanol synthesis. At 16, 0 MPa, 400 OC, 5000 h(-1), the space time yield of isobutanol was about 21.5 mi per mi cat. h(-1), and selectivity reached 98% over the Zr-Mn-K catalyst.