Process Development for Dimethylacetal Synthesis: Thermodynamics and Reaction Kinetics

The synthesis of acetaldehyde dimethylacetal was studied in a batch reactor by the acetaldehyde and methanol reaction in the liquid phase, using the acid resin Amberlyst-15 as the catalyst. Acetal synthesis was also performed with Y-type zeolite in order to compare the results for both catalysts. The reaction equilibrium constant was determined experimentally in the temperature range 293.15-333.15 K at 1.0 MPa: Keq = 0.014 3 exp[2 142.5/T(K)]. The standard molar reaction properties were obtained at 298.15 K: (delta)S(degree) = -35.34 J mol^-1 K^-1, (delta)H(degree) = -17.81 kJ mol^-1, and (delta)G(degree) = -7.28 kJ mol^-1. Kinetic experiments were carried out in the temperature range 293.15-313.15 K at 0.6 MPa. A twoparameter model based on a Langmnir-Hinshelwood rate expression was considered, using activity coefficients from the UNIFAC method, which can describe the experimental kinetic results. The kinetic law is R = kC[aAaB aCaD/(KeqaA)]/(1 + Ks,DaD)^2, and the parameters are kC = 6.91 * 10^13 exp[8 702.6/T(K)] mol g^-1 min^-1 and KD = 2.37 * 10^32 exp[-22 713/T(K)]. The activation energy of reaction for the synthesis of acetal is 72.35 kJ mol^-1. The relationship between the effectiveness factor and the Thiele modulus was determined.