Lei Yue,Guangqian Li,Guijin He,Yongsheng Guo,Li Xu,Wenjun Fang
The precise investigations on modeling properties and performance of practical fuels are usually complicated because of the multi-component nature. On the basis of hydrogen to carbon ratio (H/C), as a simple and overall characterization parameter for hydrocarbon fuels, this work provides a comprehensive insight into the study of kerosene-based hydrocarbon fuels (H/C = 1.6–2.3). The fundamental properties and supercritical cracking performance of hydrocarbon fuels are influenced intrinsically by their H/C values and molecular weights ( M ) due to the compositional and structural effects. Thus, a new combined parameter, (H/C)/ M a , is proposed to model the performance of hydrocarbon fuels. It is found that the hydrocarbon fuel with a higher H/C has a higher net heating value, and that with a higher (H/C)/ M 0.1 has a lower density. The viscosity decreases with the increase of (H/C)/ M 0.5 . The flash point shows a decreasing trend against the increase of (H/C)/ M 2 . The densities, viscosities and net heating values of 23 hydrocarbon fuels are calculated by means of the regression equations with the H/C and M data, and they are in agreement with the corresponding experimental values with the relative errors less than 2.5%, 10% and 1.5%, respectively. As investigated in an electrically heated tube reactor, the hydrocarbon fuel with a higher H/C performs thermal cracking more easily, absorb more heat and form fewer cokes. As a result, the cracking performance of hydrocarbon fuels can be predicted reasonably to a certain extent on the basis of H/C values.
Hydrothermal carbonization (HTC) has been demonstrated as an effective method for preparing hydrochar to realize efficient utilization of biomass resources. In this study, both trifluoroacetic acid (TFA) and phosphorous acid (PA) under low temperature were used as swelling solvents to disrupt the cellulose crystalline structure within 1 h with distinct physiochemical properties. After TFA and PA swelling pretreatment, by means of hydrothermal carbonization, two varieties of swollen cellulose-derived hydrochars were produced. The results showed that the TFA and PA swelling pretreatment significantly enhanced the dehydration and deoxidation of cellulose through an HTC process. The H/C value and O/C value of swelled cellulose are lower than nonswelled by more than 4% at 220 °C, which demonstrates that the dehydrogenation reaction is enhanced during the hydrothermal process of swollen cellulose. Particle size as well as microscopic arrangement of hydrochars were distinctly different due to swelling cellulose. The particle size of hydrothermal carbon microspheres increases by a swelling process at the same hydrothermal carbonazition temperature. TFA-HTC have an estimate diameter of 0.2 μm at 220 °C, which is equivalent to the size of CEL-HTC-280. This study illustrates the mechanism for hydrothermal carbonization of TFA and PA swollen cellulose and provides a novel route for directionally regulating hydrothermal carbon microspheres and developing carbon-based catalysts.
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