5-Ethoxymethylfurfural (EMF) and ethyl levulinate (EL) have been considered as the new promising biofuels. A comparative study was conducted for the direct conversion of carbohydrates into EMF and EL in different medium containing ethanol. The distribution and formation kinetics of EL, EMF, 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) in pure ethanol and ethanol/organic solvent medium were compared, and the results showed that the addition of nhexane can improve the accumulation of EMF. When the volume ratio of ethanol to n-hexane was 6:4, 66.29% of EMF yield can be obtained from fructose at 120°C and 180 min. The total yield of the EMF and EL can reach to 83.71%, increased by 5.73% compared with that in pure ethanol medium. Moreover, water addition can suppress the etherification of HMF to EMF and promote the rehydration of HMF to LA in the process. On the basis, a putative reaction pathway for the conversion of carbohydrates in ethanol/n-hexane medium was proposed.
The one-pot production
of a promising biofuel, 5-ethoxymethylfurfural (EMF) from corn stover
with mixed acid as the catalyst, was investigated and optimized by
using the response surface methodology. Catalyzed by the mixed acids
comprised of 0.1% H2SO4 and 1.0% zeolite USY,
a high EMF yield of 23.9% at 210 °C and 125 min can be obtained
from corn stover. Meanwhile, the catalytic activity of the zeolite
USY had no obvious loss after five recycles. On the basis of the putative
reaction pathway, the kinetics modeling for the EMF production directly
from corn stover was developed, which coincided with the first-order
reaction model. This study provides a promising strategy for EMF preparation
from corn stover.
5-Ethoxymethylfurfural (EMF) can be considered as a potential biofuel because of its excellent combustion properties, such as high energy density and low carbon smoke emissions. In this study, Ultra-stable Y (USY) zeolite was modified with NH4H2PO4 and then used as an efficient solid catalyst for the catalytic synthesis of EMF via ethanolysis of glucose First, the NH4H2PO4-modified USY was characterized by FT-IR, XRD, BET, and NH3-TPD. The effect of reaction temperature, reaction time, substrate concentration, and catalyst loading on the yield of EMF was investigated. The P0.2-USY optimal EMF yield was 39.6 mol%, which increased by 20.7% compared to USY, and still had better activity after being reused for 5 cycles. Moreover, the pseudo-homogeneous first-order kinetics model was developed to elucidate the kinetics of EMF formation from glucose, and the kinetics results showed that the activation energy of EMF formation (64.2 kJ⋅mol-1) was lower than that of humins formation (73.2 kJ⋅mol-1). Finally, the ethanolysis pathway was proposed based on the product distribution.
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