The extended Hukel theory was applied to compute molecular orbits of 17 typical components of naphtha. On this basis

a general principle of seeking the best lumping scheme was put forward by means of fuzzy analy sis. The catalytic naphtha reforming process was then studied by analysing the 17 typical components. Lumping schemes with different λ levels were obtained. Theresults of comparing these schemes with the models of catalytic naphtha reforming reported in literatures showed that the lumping schemes with different λ levels agreed well with the lumping models. According to the principle given in the paper

it can be seen that the four components lumping model of Smith corresponds to a λ level of 0.93

the 13 components lumping model of Mobil Co. corresponds to a λ level of 0.97

and the 22 components lumping model of Kmark corresponds to a λ level of 0.98.