• Energy Research

The micropores present in ZSM-5 are beneficial to the production of aromatic compounds in biomass catalytic pyrolysis, although the small pore size leads to severe coke deposition on the catalyst. In this study, a micro-mesoporous structured ZSM-5 zeolite catalyst was synthesized and modified with green templates (sucrose, cellulose, and starch) to introduce additional mesopores. It was found that the catalysts modified using the sucrose and cellulose templates only exhibited a slight increase in their micropore volumes, while the mesopore volume of ZSM-ST (modified with the starch template) reached up to 0.359 cm3/g. This increase promoted the cracking of bulky oxygenates and suppressed the polymerization reaction on the ZSM-5 surface, thereby producing a greater number of aromatic products. Moreover, the benzene, toluene, and xylene (BTX) yields exhibited a positive correlation with the catalyst mesopore volume, with the highest BTX yield of 91.84 mg/g being obtained with 10% starch addition.

Abstract Solar pyrolysis process offers solution to utilize solar energy for converting biomass energy into solar fuel. A Box–Behnken design of experiments was performed to optimize a solar pyrolysis process for the production of combustible gases from beech wood. Response surface methodology (RSM) was used to study the effects of temperature, heating rate and argon flow rate on products distribution, gas LHV (lower heating value) and gas composition. The operating variables were as follows: temperature (800–2000 °C), heating rate (50–450 °C/s) and argon flow rate (4–8 NL/min). A second-order regression model was used to predict the responses. The proposed model described well the experimental values. The analysis of variance (ANOVA) was performed with Minitab 17 software and the significant effect of the factors and their interaction effects were tested at 95% confidence interval. The gas LHV was significantly influenced by temperature and heating rate. The maximum gas LHV higher than that of initial beech wood was found as 14,589 kJ/kg under process conditions as: 2000 °C temperature, 450 °C/s heating rate. The beech wood calorific value is upgraded through solar pyrolysis.

Fil: Zeng, Kuo. Centre National de la Recherche Scientifique; Francia. Processes Materials and Solar Energy Laboratory; Francia

Molten salt pyrolysis driven by concentrated solar radiation is well positioned to utilize solar energy and lignite effectively. This study focused on the effects of temperature (500, 600, 700 and 800 °C) and molten carbonate salt (Li2CO3-Na2CO3-K2CO3) on properties of char obtained from lignite pyrolysis, as well as gas and tar products for revealing their formation mechanism and transformation process. Molten salt pyrolysis of HulunBuir lignite produced more gas products and less char compared to conventional pyrolysis owing to the enhanced heat transfer and catalytic effect of molten salt. The char yield decreased from 58.4% to 43.4%, and the gas yield (especially CO2, H2 and CO) increased from 28.3% to 46.1% at 800 °C. CO2, CO and H2 production increased about 60.43%, 103.42% and 65.2% at 800 °C, respectively. Additionally, the presence of molten salt improved the tar quality with more hydrocarbon content (maximum increase of 5.8%) and less oxygenated compounds. The structure and reactivity relationship of char was characterized by XRD, BET, SEM, FTIR, Raman spectroscopy and TGA. Molten salt generated char had a higher reactivity due to the increase of disorder, surface area, microporosity (maximum of 71.74%) and active sites.

The solar pyrolysis of beech wood was investigated with the objective of determining the optimal pyrolysis parameters for maximizing the LHVs (lower heating values) of the gas products because they can be further utilized as fuel gas for power generation, heat and production of transportable fuels. The investigated variables were the pyrolysis temperature (600–2000 °C), heating rate (5–450 °C/s), argon flow rate (6–12 NL/min) and pressure (0.44–1.14 bar). The results indicate that the product yields (liquid, char and gas), gas composition (H2, CH4, CO, CO2 and C2H6) and LHV are strongly influenced by the pyrolysis parameters. The total gas LHV greatly increases with increasing temperature (from 600 to 1200 °C) and increasing heating rate (from 5 to 50 °C/s), which is mainly due to increases in the CO and H2 yields. The variation in the gas LHV with pressure and argon flow rate is slight. A maximum gas production of 62% with a LHV of 10 376 ± 218 (kJ/kg of wood) is obtained under solar pyrolysis conditions of 1200 °C, 50 °C/s, 0.85 bar and 12 NL/min. This heating value is almost identical to that of the initial beech wood, thus confirming that valuable combustible gases can be produced via the solar pyrolysis of beech wood.