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The effects of the newly improvised catalyst preparation technique, namely ultrasonic spray precipitation (USP), on the physicochemical properties as well as the catalytic performance of Cu-Zn-Al-Zr catalyst in CO 2 hydrogenation reaction were studied. Spraying technique is advantageous in generating micro-droplets of catalyst precursors by providing high surface area contact during precipitation, while the incorporation of an ultrasonic irradiation can physically alter the surface morphology of the catalyst. In this study, Cu-Zn-Al-Zr catalysts were prepared using both USP and conventional precipitation (CP) techniques for comparison purposes. Structural analysis showed that USP technique dictated the formation of finer Cu crystallites with better particle uniformity. Meanwhile, TPR results revealed a good interaction between different elements in the catalyst with the formation of single form of oxide species. In terms of reactivity, USP-prepared catalyst outperformed CP catalyst for CO 2 conversion by 20.9% and also improved methanol selectivity and yield by 2.7 and 27%, respectively, while reducing noticeably the unwanted CO. It is believed that the improved surface basicity of USP catalyst, which has a great influence on reaction pathways of intermediate species, contributed significantly to the enhanced catalytic performance, and hence justifying the superiority of this new preparation technique over the conventional ones. [ABSTRACT FROM AUTHOR]

Biomass pellet is a popular fuel, and pyrolytic char can be a promised carbon material, further understanding char structural evolution can promote its utilization. To deeply investigate the evolution of char chemical structure and its heterogeneity during biomass pellet pyrolysis process, a new method was developed to fragment the char in space, and the chemical structures of the fragmented sections were analyzed by a micro-Raman spectroscopy (equipped with a 532 nm laser). The first-order Raman spectra (800–1800 cm−1) of varied positions of sawdust pellet pyrolytic char were curve-fitted with 10 Gaussian bands to reveal the temporal and spatial evolutions. The results indicate that pyrolysis of sawdust pellet can be divided into two stages: i) the decomposition of raw biomass (temperature heterogeneity in pellet remains); ii) the condensation reactions of aromatic ring systems (temperature in pellet becomes uniform). The axial and radial heterogeneity of char chemical structure is mainly caused by heat transfer when the whole pellet temperature is uniform during heating. While mass transfer, in accordance with volatile diffusion, can eliminate the heterogeneity of char chemical structure by volatile-char interaction. The combined effects of heat and mass transfer lead to a heterogeneity in pellet char chemical structure. • An expanded Raman method by combining micro positioning and analysis was developed. • Chemical structure heterogeneity of sawdust pellet pyrolytic char was quantified. • Temporal and spatial evolutions of pyrolytic char chemical structure were revealed. • Combined effects of heat and mass transfer on char chemical structure were found. [ABSTRACT FROM AUTHOR]

Heavy components affect conversion behaviors of sludge-derived pyrolytic liquids during their utilization and contribute significantly to the formation of the notorious tar and soot during sludge gasification and combustion. Understanding the evolution of heavy components during pyrolysis is vital for developing a reliable sewage sludge utilization technology. This study investigates the compositions of oils from the pyrolysis of sewage sludge using an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT ICR-MS). Hundreds of compounds with molecular mass higher than 400 Da were detected from the pyrolytic oil obtained at 450 and 650 °C. Higher pyrolysis temperatures promoted decomposition and polycondensation of large molecules and increased the amount of nitrogen-containing compounds in the liquid. Aromatic structured molecules consisting of carbon, hydrogen and nitrogen were the predominant compounds at 850 °C. From the results of this study, the evolution routes of heavy components in the pyrolytic liquid are proposed. [ABSTRACT FROM AUTHOR]

Microwave-assisted extractions (MAEs) were carried out on Shenfu (SF) low-rank coal using four types of solvent, namely tetrahydrofuran, methanol, dichloromethane and ethyl acetate. Comparison with the traditional thermal extractions (TEs) indicated that MAEs were much more efficient in extracting organic components of SF coal. A large amount of aromatic compounds with 2–3 rings and rich branched alkanes could be extracted from coal by MAE. The results also showed that solvent polarity and the interaction between solvent and functional groups abundant in the extracts were the two main factors leading to differences of their MAE. Among the studied solvents, tetrahydrofuran could extract much more amount of polar compounds and its solution was rich in highly-condensed polycyclic aromatic compounds (PACs) with ≥ 4 rings. And this feature had relationship with its strongest interaction with the C O bond. Ethyl acetate, in contrast, showed strong interaction with the C O bonds and had good potential for the extraction of low-polarity compounds especially PACs with two aromatic rings and aliphatic compounds with long alkane chains. And for methanol and dichloromethane, their solvent polarity played dominant roles during the MAE procedures. The results provided more detailed mechanistic influences of different solvents on MAE of coal, and would help for the identification of a suitable solvent for efficient detection of components in organic substances, especially the extraordinary complex compounds in coal. [ABSTRACT FROM AUTHOR]