Enhanced bioethanol-to-ethylene performance over nanosized sheet-like M-SAPO-34 (M = Sr and K) catalysts

Two-dimensional (2D) morphology zeolites nanosheets NS-M-SAPO-34 (M = K and Sr) were developed and applied for producing ethylene (C2H4) from bioethanol. Various factors, including SAPO-34 type, temperature, bioethanol concentration, and weight hourly space velocity (WHSV) on C2H4 production were evaluated. The synthesized NS-M-SAPO-34s gave a nanosheet-like morphology with a thickness of 25–50 nm, while the commercial cube-like SAPO-34 (CC-SP34) exhibited a cubic-like morphology with a particle size of about 1.5 μm. The specific surface area of the NS-Sr-SAPO-34 was 644 m2 g−1 which was much larger than that of CC-SP34 (573 m2 g−1). The catalytic performance evaluated by bioethanol dehydration reaction showed that NS-Sr-SAPO-34 exhibited significant improvements not only in suppressed coke deposition (5.6%) and prolonged lifetime (913 min) but also in higher C2H4 yield (94.5%) compared with those (11.8%, 160 min and 82.4%, respectively) of CC-SP34, which can be attributed to the shortened diffusion path length, highly accessible active centers and suitable medium-strong acidity. Elevated temperature, high bioethanol concentration and decreased WHSV tended to enhance the C2H4 yield, while decreased bioethanol concentration was propitious to suppress coking rate. An optimal C2H4 yield of 100% was obtained at 350 °C with a bioethanol concentration from nutrient broths (15 vol%, WHSV = 0.75 h−1).