Using a membrane reactor for reversible transesterification reaction involves reaction and product separation within a single unit. However, a pseudohomogeneous reaction and heterogeneous separation must be maintained for successful membrane reactor operation. Present research is aimed to develop an integrated model of chemical and phase equilibrium (CPE) and modified Maxwell-Stefan equation that describes the simultaneous CPE and mass transport phenomena of biodiesel production from crude palm oil (CPO) using a membrane reactor. In the first part of this work, a systematic approach describing simultaneous CPE of CPO transesterification in the membrane reactor was developed with the reconciliation of transesterification reaction and phase equilibrium that involves six-component. The results revealed that regressed apparent equilibrium constant, Keq value of 17.557 +/- 1.51% were higher than the literatures. This indicates that forward reaction of the reversible CPO transesterification is much favored in the membrane reactor than the conventional reactor. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 1968-1980, 2015