Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Mechanistic insights into Ga-modified hollow ZSM-5 catalyzed fast pyrolysis of cassava residue
No full textThe preparation of valuable chemicals by catalytic fast pyrolysis (CFP) is a promising and environmentallyfriendly approach for the selective upgrading of waste cassava residue (CR). This work systematically investigated the conversion mechanism and kinetic characteristics of CR pyrolysis over Ga-modified hollow ZSM-5, for the purpose of enhancing aromatics production. The hollow configuration significantly regulated the structural characteristics of ZSM-5, thus facilitating the diffusion, deoxygenation, and aromatization of pyrolysis intermediates. The incorporation of Ga species and generated Br & oslash; nsted acid sites remarkably accelerated the reaction rate and suppressed the carbonization at high temperatures, through enhancing the end scission of starch and cellulose components. With the aid of 5Ga/ZSM-H, the relative content of aromatics achieved 95.4% at 700 degrees C, and still maintained over 92.5% even after 5 cycles. The ring-opening and retro-aldol degradation were identified as crucial steps for the production of ketones and aldehydes separately, which were further transformed into hydrocarbon pools by deoxygenation and subsequently converted into aromatics via Diels-Alder reaction. Kinetic analysis demonstrated that the use of 5Ga/ZSM-H lowered the average activation energy of CR pyrolysis by 14.8%, particularly for the initial pyrolysis stage. Moreover, the plausible mechanism for aromatics formation from Ga-modified hollow ZSM-5 catalyzed CR pyrolysis was proposed
Qing Lan Project of Jiangsu Province, Science and technology plan of Zhenjiang[CQ2022002]
No full textPore-scale investigation on the morphology evolution and micro-mechanism of methane hydrate formed from free gas and dissolved gas
No full textThe distribution characteristics of gas hydrates in the pores of sediments are critical to predict the macroscopic properties of hydrate reservoirs and the efficient production of gas hydrates. In this study, the experiments of methane hydrate formation were conducted in a glass micromodel, and the morphology evolution of hydrate formed from the free gas and dissolved gas in the pores were observed through a video microscope. Observation results showed that the hydrate formed from free gas grew preferentially along the gas-water interface and subsequently toward the center of the gas phase. For the hydrate formed from dissolved gas, it was preferentially occurred on the surface of the hydrate crust formed from free gas and gradually grew toward the water phase. The hydrate formation rate was determined by the concentration of methane molecules in surroundings water. The hydrate formed from free gas was porous structure and composed of many tiny hydrate crystals, and the hydrate formed from dissolved gas was smooth and transparent polyhedral hydrate crystal. For the hydrate formed by free gas, the occurrence pattern of hydrate in the pores might change from the grain-cementing to the contact-cementing or the patchy. The occurrence pattern of the hydrate formed from dissolved gas could be the pore-filling or the load-bearing. This study could be helpful for explaining the phenomenon of macroexperiments, the model construction for the macro-properties of hydrate-bearing sediments, and the exploring of gas hydrates reservoirs
Cooperative production of monophenolic chemicals and carbon adsorption materials from cascade pyrolysis of acid hydrolysis lignin
No full textA novel cascade pyrolysis upgrading process for acid hydrolysis lignin (AHL), consisting of pyrolysis, catalytic upgrading of pyrolysis vapors, and pyrolysis char, was developed to improve the yield of value-added products (monophenolic chemicals and carbon materials). Pyrolysis of AHL at 450 degrees C and subsequent catalytic upgrading of pyrolysis vapors over Ni/H-ZSM-5 boosted the concentration of monophenolic chemicals in pyrolysis liquids by 58%. The carbon material prepared from pyrolysis char using KOH as activating agent exhibited a large specific surface area of 2902.5 m2/g and a large total pore volume of 1.45 cm3/g, thus affording good adsorption capacity for methylene blue (824.87 mg/g) and iodine (2333.17 mg/g). Moreover, the cascade pyrolysis upgrading of AHL achieved a yield of 68.52% desired products, which was much higher than the reported results (single production of monophenols and pyrolysis char). In summary, this work provides a potential reference for efficient utilization of lignin in large-scale applications
Nonempirical fractal permeability model and experimental verification of hydrate-bearing sediments based on heterogeneous distribution of particles
No full textThe one of the factors limiting production of gas-water is affected by sediments ' permeability. Evaluating the normalized permeability ( K n ) of sediments containing hydrates is necessary for analyzing the saturation (decomposition level) and flow capacity. The mistakes in K n prediction are frequently brought about by the assumption such as homogenous particles distribution and ignoring microscopic pore structure. To address the issue, a fractal-based nonempirical prediction model of K n was developed by modeling, parameter acquisition using SEM and Analyzer, experiment validation, error comparison with published data, and sensitivity analysis for evolution, respectively. Assuming that sediment skeleton particles were misaligned spherical particles of equal diameter. The heterogeneity of sediments was described by the vertical and horizontal distance ratio ( m ) and offset angle ( theta ) of the particles. This led to a novel approach for determining average tortuosity ( tau av,0 ) and tortuosity fractal dimension ( D tau,0 ). The viability of the model was confirmed by permeability measurement experiments. Additionally, using the measuring function of SEM, the maximum pore diameter of sediments was obtained. Furthermore, a comparison with earlier data demonstrated the effect. Considering heterogeneity, the average accuracy of Geometric Mean Variance in K n has increased to 9.66%. Finally, each parameter ' s impact on prediction was examined. At m = 1.357, D tau,0 grows symmetrically. K n,GC varies 15 times more with an increase in D tau,0 than K n,PF . All findings indicate that the new model is more likely to be forecasted K n for a variety of systems, including clayey-silt, sand, and silty-sand system, and especially in reflecting the heterogeneity
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