Orthogonal array design for optimization of additives assisted cycol-dehydration of 1,4-butanediol to tetrahydrofuran in near-critical water

Orthogonal array designs (OAD), OA25 (56), were applied for the first time to optimize cyclo-dehydration of 1,4-butanediol (BD) to tetrahydrofuran (THF)- assisted with additives in near-critical water (NCW) in which the interactions between the variables were temporarily neglected. Six parameters at five levels such as reaction time (t, min), reaction temperature (T,°C), reactant/water ratio (R/W, wt./ wt.), additive/reactant ratio (A/R, wt./wt.), sort of additives and reaction pressure (P, MPa) were investigated. The effects of these parameters were studied by using analysis of variance (ANOVA) to determine the relationship between experimental conditions and levels of yield of THF and conversion of BD. The results showed that the additives had the most significant influence on the yield of THF and conversion of BD, and the other five factors had some advantageous effects on the yield of THF and conversion of BD, however, those effects were much smaller than that of the additives. Finally, the optimal experimental conditions were proposed which could provide the highest yield with respect to the considered factors. Base on these results, a possible reaction mechanism was proposed.