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Hierarchical HZSM-5 zeolites were prepared by desilication of commercial HZSM-5 in aqueous NaOH solutions with the assistance of tetrapropylammonium hydroxides (TPAOH), and applied for the catalytic upgrading of bio-oil derived from the fast pyrolysis of sunflower stalk. The hierarchical HZSM-5 by using 0.2 M NaOH with 0.25 M TPAOH for the desilication exhibited the best catalytic performance and the relative total peak area related to the aromatic hydrocarbons reached 65.8% with a yield of the detected aromatic hydrocarbons up to 45.2 mg/g-bio-oil. With the assistance of 0.25 M TPAOH for the desilication, the formation of mesopores became highly controllable, resulting in the increase in the surface area and maintainment of enough acid amounts, however, the coking on the surface of catalyst was not hindered. To solve the coking problem and increase the aromatic hydrocarbons production, the hierarchical HZSM-5 with the best performance was modified by various metals. It is found that 0.25 wt% Cu loaded hierarchical HZSM-5 increased the yield of the detected aromatic hydrocarbons up to 54.5 mg/g-bio-oil with a decrease in the coke formation.

Co-pyrolysis of two different types of biomass among apple tree branch (ATB), knotweed stem (KWS), seaweed (SW) and rice straw (RSt) was conducted to obtain co-pyrolysis char (co-char), and then the steam gasification of those co-chars was compared with the steam co-gasification of the physically mixed individual biochars to investigate the synergetic effect resulted from alkali and alkali earth metal (AAEM) in each biomass involved. It is found that the silica species in the RSt had negative effect on the activity of co-char due to the formation of alkali silicate compounds. However, combination of RSt with some non-woody biomass such as SW also showed promoting effect. In particular, the gasification of the co-char from the combination of various biomass with low or no silica content showed improved gasification efficiencies due to the synergetic effect AAEM species in the co-char from the different biomass. Therefore, the biomass selection should play a significant role in the co-pyrolysis of different biomass in the two-stage gasification system.

A transport bed flash calcination (TBFC) process applied to magnesite is systematically investigated through process simulation to optimize the energy-saving strategy. The high-temperature calciner flue gas is used to preheat the fed magnesite, while the sensible heat with the caustic calcined magnesia (CCM) product is cooled by air sent to the calciner. Pre-decomposition of magnesite during preheating is considered on basis of the kinetics measured using a micro fluidized bed reaction analyzer that allows the minimized effect of external diffusion on reaction. With staged fuel gas supply the TBFC process allows the equivalence ratios around 1.2 for combustion. The preferred arrangement of stages for magnesite preheating and CCM cooling are respectively 4 and 2, leading to the energy consumption of 4100 kJ/kg-CCM and the energy efficiency of 66.8%, which is almost doubly higher than the 33.9% of the conventional reverberatory furnaces (RF). The pre-decomposition occurs mainly in the 1st-stage preheater, and the maximal conversion is about 13%. Varying the stages of preheating appears more influential on the energy saving than varying the cooling stages, while residence time above 1 s in the preheaters has limited effect.

In this study, the gas production behavior from the steam gasification of the biochar derived from the pruned apple brunch was investigated using a fixed-bed reactor. The optimal biochar obtained at the pyrolysis temperature of 550 °C was gasified under different operating conditions for the hydrogen rich gas production. The experimental results indicated that high reaction temperature and high water flow rate were both beneficial to the hydrogen gas yield, but excess steam had a negative impact contrarily. Besides, the small size particles (0.5–1.0 mm) showed better performance in the hydrogen gas production at the low water flow rates (0.05–0.20 g/min); while the large size particles (1.0–2.8 mm) showed better performance at the high water flow rates (0.25–0.30 g/min). The suitable operating conditions for the gasification of the biochar were determined as the reaction temperature of 850 °C, water flow rate of 0.25 g/min, and particle size of 1.0–2.8 mm.

Dealkaline lignin (DAL) was used as a carbon and sulfur source to prepare MoS2/Mo2C-based catalysts (Mo-DAL) with a facile impregnation-pyrolysis two-step process for the hydrogen production from the formic acid decomposition. Comparison of the catalytic performance of the Mo-DAL catalyst with the carbon black-based one (Mo2C-CB) revealed that the Mo-DAL catalyst exhibited superior activity to the Mo2C-CB catalyst. When 20 wt % of Mo was loaded on DAL, the catalyst produced hydrogen quite selectively (99.2%) with almost complete conversion of formic acid (97.4%) at 220 °C. In addition, the catalyst showed stable activity for at least 50 h in these conditions. This catalytic activity and hydrogen selectivity are superior to the other reported nonprecious metal catalysts. Since DAL contains not only carbon but also sodium and sulfur species, multiple kinds of active sites such as Na-intercalated MoS2, MoS2, and β-Mo2C were formed on the Mo-DAL catalysts. Investigation of additional effects of sulfur and sod...

In this study, steam gasifications of a kind of marine biomass, i.e., Zostera marina (eelgrass), and the biochars derived from pyrolysis of it were carried out for the biohydrogen production in a fixed-bed reactor. The effects of reaction temperature and water injection rate on the hydrogen production were investigated. In order to understand the effect of sea salts attached on the surface of eelgrass for the hydrogen production, the eelgrass washed by water (washed-eelgrass) was also used as the feedstock. It was observed that hydrogen productions from the gasification of washed-eelgrass as well as its biochar were higher than those of raw eelgrass and its biochar, indicating that the impurities of raw eelgrass had a negative effect on the hydrogen production. The biochar derived from the pyrolysis of washed eelgrass at 550 °C had the largest amount of hydrogen yield at the gasification temperature of 850 °C with a water injection rate of 0.15 g/min. It was found that both the hydrogen production and reaction rates were enhanced by mixing washed-eelgrass biochar obtained at 350 °C with the calcined seashells at a weight ratio of 1 to 2, especially at the gasification temperature of 650 °C. Meanwhile, in the presence of the calcined seashell, CO2 content decreased sharply whereas the hydrogen yield had no obvious increase.

Biomass to hydrogen is becoming a promising way to produce clean energy with zero or even negative carbon emission. In this study, a novel system containing a biomass pyrolysis process, a catalytic steam reforming of bio-oil process, a chemical looping unit using biochar as the reducing agent and other auxiliary processes including H2 separation and thermal energy circulation processes for hydrogen production is proposed and simulated based on the previous studies. While, a waste heat recovery system is recommended for energy recuperation to make the entire system become auto-thermal. The effects of steam to carbon ratio in the catalytic steam reforming reaction and temperatures at reducing and steam reactors in the chemical looping unit on the system performance are analyzed in details. Under the optimum condition in the proposed system, about 6.9 kg/h of hydrogen could be produced from 100 kg/h of wood biomass with 58.3 kW of net power. Compared with the biomass direct chemical looping process for H2 production, separating the bio-oil and biochar after the pyrolysis process and combining the steam bio-oil reforming process with the chemical looping unit using biochar for H2 production can increase H2 production efficiency from biomass by more than 50%. It is expected that this proposed system could be implemented in a practical application.