Kinetic simulations of methanol synthesis and its major impurity formation were studied over a commercial unmodified Cu/ZnO/Al2O3 catalyst using an isothermal micro reactor. The experimental data for MeOH, DME, and EtOH have been evaluated based on the well-established rate expressions from the literature. The kinetic models can be used to estimate both methanol and major impurity formation with sufficient accuracy. These models can serve as a base for methanol synthesis quality analysis and provide critical information for the downstream distillation unit. In addition, the behavior of methyl formate formation under various temperatures was studied. A quick decay under high temperature can be attributed to the sequential decomposition of formic acid which plays a detrimental role in induction time shortening of the D1363 test.