The non-congruent liquid-gas phase transition (LGPT) in asymmetric nuclear matter is studied using the recently developed Quantum van der Waals model in the grand canonical ensemble. Different values of the electric-to-baryon charge ratio, Q/B, are considered. This non-congruent LGPT exhibits several features which are not present in the congruent LGPT of symmetric nuclear matter. These include a continuous phase transformation, a change in the location of the critical point, and the separation of the critical point and the endpoints. The effects which are associated with the non-congruent LGPT become negligible for the following cases: when Q/B approaches its limiting values, 0.5 or 0, or if isospin dependence of nucleon-nucleon interaction and quantum statistical effects can be neglected. The latter situation is realized when the particle degeneracy attains large values, g≳10.