EQUILIBRIUM-CONSTANTS FOR METHYL TERT-BUTYL ETHER AND ETHYL TERT-BUTYL ETHER LIQUID-PHASE SYNTHESIS USING C(4) OLEFINIC CUT

Equilibrium constants for the liquid-phase syntheses of methyl tert-bu tyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined exp erimentally in the temperature range 313-353 K and at 1.6 MPa, using a s source of 2-methylpropene (isobutylene) a C4 olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as the catalys t. The thermodynamic equilibrium constants and the enthalpy, free ener gy, and entropy changes of reactions were given as a temperature funct ion. At 298 K, the standard molar reaction enthalpy DELTA(r)H(m)-degre e(298 K, 1.6 MPa) for MTBE and ETBE are -(37.3 +/- 2) and -(34.8 +/- 1 .3) kJ.mol-1, respectively, and are compared with literature data. A c omparison of the equilibrium constant values with those obtained using pure reactants with and without small initial amounts of water (< 5 w t %) is also included. The UNIFAC estimates of activity coefficients w ere used to describe the liquid-phase nonideality. The standard molar enthalpies of formation DELTA(f)H(m)-degree(1,298.2 K) of MTBE and ETB E are -313.5 and -349.9 kJ.mol-1, respectively.