*3.3. Reaction Conditions Evaluation*

In this section, Taguchi's L16 experimental design was used for optimizing reaction conditions so as to produce HMF from glucose using the selected catalyst HPW/Nb2O5/300 ◦C. Different reaction conditions and responses are summarized in Table 4. As it can be seen, HMF yield obtained in these experiments ranged from 7.6% to 40.8%. As in the previous stage, high glucose conversion was obtained, i.e., ranging from 63.7% to 98.4%, which could also be associated with by-products formation. The highest HMF yield (40.8%) was obtained under the conditions of assay 2 (160 ◦C, 5% *w*/*v* of catalyst, 50 g/<sup>L</sup> of glucose, 1:1 *v*/*v* acetone-to-water, 300 rpm and reaction time of 30 min).

