A deactivation model for the dehydration of 2,3-butanediol (2,3-BDO) to 1,3-butadiene (1,3-BD) and methyl ethyl ketone (MEK) on an amorphous calcium phosphate (a-CP) catalyst is herein proposed. The deactivation of a-CP catalyst can be explained by the following steps: (i) 1,3-BD selectivity is increased sharply as the temperature increases; (ii) the high 1,3-BD selectivity and temperature raise a possibility of the polymerization of 1,3-BD; and (iii) heavy compounds made by polymerization cover the active surface of the catalyst and block the pores of the catalyst. Deactivation data for around 86 h obtained from a laboratory-scale fixed bed reactor operated under isothermal conditions were found to be modeled well using the simplified concentration independent generalized power law expression of the form d alpha/dt = -K-d (alpha - alpha(eq))(m). The values of deactivation order m, the limiting activity at infinite time alpha(eq), and the activation energy for deactivation E-d are found to be 1.32, 0.33, and 1.00 X 10(06) J/mol, respectively. Also, it was confirmed that the activity of a-CP catalyst is constant after the regeneration through the same experiment conducted with the regenerated a-CP catalyst.