Multiple components synergy of Cu-based catalysts for dehydrocyclization of 1,4-butanediol to γ-butyrolactone
Gas-phase dehydrocyclization of 1,4-butanediol (BDO) is an environmentally benign and sustainable route for γ-butyrolactone (GBL) production. In this work, a series of Cu-M (M = Zn, Cr) catalysts was synthesized via coprecipitation and evaluated in a fixed-bed reactor for GBL yield. Under the reaction conditions of 240 °C, 0.1 MPa, and a weight hourly space velocity (WHSV) of 2 mL∙g −1 ∙h −1 , 99.62% of BDO conversion, 99.72% of GBL selectivity, and 2.22 mol GBL ·g catalyst -1 ·h −1 of CBL formation rate were achieved over CuZnCr-600 catalyst, which is higher than reported studies. Long-term test proved that this catalyst could operate over 100 h without any deactivation. Combined microscopic and spectroscopic analysis showed that the calcination conditions affected the surface acidity-basicity of catalysts by changing the CuO content and the strength of the Cr-O bond. The Cu-M compositions significantly influenced the morphology and the electronic properties of Cu species. The incorporation of Cr led to the formation of CuCr 2 O 4 spinel structure, which not only enhanced Cu dispersion but also improved the catalysts’ resistance to sintering. The presence of Zn restrained the phase-transformation of CuCr 2 O 4 from cubic to tetragonal, which ensured the reducible property of CuCr 2 O 4 even under high-temperature calcination. Furthermore, modulating the calcination temperature and the Cu-M compositions maintained an optimal Cu + /Cu 0 ratio under reaction conditions. All these issues contributed to the high yield of GBL and the prolonged lifetime of catalysts.
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