As the major component of plant biomass and inedible feedstock, cellulose is extensively considered as an ideal raw material for the sustainable supply of biofuels and chemicals in the future.1 Hyperbranched polymers have attracted considerable attention during the past decade. Compared with linear analogs, they show low viscosity, high solubility and well exposed terminal groups which can be readily functionalized for catalytic application.2 We previously reported the synthesis of hyperbranched poly(arylene oxindole)s (HPAOs) in a one-step A2 + B3 polycondensation via superelectrophilic arylation of isatin. Further functionalization of HPAOs by controlled sulfonation in oleum offers a new class of acid catalysts, combining the advantages of homogeneous and heterogeneous catalysts, namely sulfonated hyperbranched poly(arylene oxindole)s (SHPAOs). The previous studies of SHPAOs on catalytic applications revealed that it is an efficient catalyst for the degradation of cellulose to LA (29.5% yield). More importantly, it can be readily recycled by ultrafiltration.3 In this contribution, various modified SHPAOs were studied in the catalytic conversion of cellulose to LA. Interestingly, we found that the catalytic efficiency of conversion of cellulose to LA can be improved significantly by introducing chloro groups on SHPAOs. This improvement results from the effect of chlorines on facilitating breakdown of cellulose to glucose through forming hydrogen bond between catalyst and cellulose. Moreover, it was observed that the existence of chlorines is beneficial to the isomerization process from glucose to fructose, which is widely considered as an important step for the degradation of cellulose to LA. References: (1) Huber, G. W.; Iborra, S.; Corma, A. Chem. Rev. 2006, 106, 4044 – 4098.   (2) Higashihara, T.; Segawa, Y.; Sinananwanich, W.; Ueda, M. Polym. J. 2011, 44, 14-29. (3) Van de Vyver, S.; Thomas, J.; Geboers, J.; Keyzer, S.; Smet, M.; Dehaen, W.; Jacobs, P. A.; Sels, B. F. Energy Environ. Sci. 2011, 4, 3601-3610.

Efficient catalytic conversion of cellulose into levulinic acid by sulfonated hyperbranched poly(arylene oxindole)s with chloro substituents

249th National Meeting (2015)

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