Synthesis of Hierarchical Porous SAPO-34 and Its Catalytic Activity for 4,6-Dimethyldibenzothiophene.

Zeolite SAPO-34 has been widely used in the industry because of its special pore structure and wide distribution of acid sites in the pore channel. However, traditional SAPO-34 with a small pore size suffers from carbon deposition and deactivation in catalytic reactions, and its inability to catalytically convert bulky organic molecules limits its industrial application. Meanwhile, impurities of SAPO-5, which have weak acidity leading to rapid catalyst deactivation, appear in SAPO-34 zeolite. Therefore, it is of great significance to synthesize SAPO-34 zeolite with a mesoporous pore structure, which can significantly improve the transfer of molecules in zeolites. In this paper, SAPO-34 zeolite with a hierarchical pore structure was synthesized, and its hydrodesulfurization performance for 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied in a fixed bed reactor. The characteristic results show that BET-specific surface area, micropore volume, and mesoporous volume of synthesized SAPO-34 are 754 m2 g-1, 0.25, and 0.23 cm3 g-1 respectively, and the pore size is mainly concentrated at 4 nm. The catalytic conversion of 4,6-DMDMT with Co- and Mo-supported SAPO-34 is about 83%, which is much higher than the catalytic performance of Al2O3.

[Characteristics of Dissolved Organic Matter in Overlying Water During Algal Bloom Decay].

In this study, indoor simulation experiments were performed to elucidate the effects of migration and transformation of dissolving organic matter (DOM) during the decay of algal blooms. Based on ultraviolet-visible spectra (UV-vis) and excitation-emission matrix spectroscopy (EEMs), spectral characterizations of dissolved organic matter (DOM) in overlying water were evaluated with analyses of the physical and chemical indexes, variation in dissolved organic carbon (DOC), and variation in dissolved inorganic carbon (DIC). Results showed that at the early stage of decay, a large amount of organic matter was released, and dissolved oxygen (DO) decreased sharply. With the extension of reaction time, DOC gradually changed into DIC, which further changed the oxidation-reduction and acid-base characteristics of the water. UV-vis spectra showed that a large amount of DOM was released with high aromaticity and a high degree of humification, and the released DOM was gradually degraded. With the application of parallel factor analysis in excitation-emission matrix spectroscopy (EEM-PARAFAC), three fluorescence components were analyzed:refractory humic-like substances (C1), protein-like tryptophan substances (C2) produced by algae, and fulvic-like substances (C3) related to microbial activities. Most protein-like tryptophan substances were degraded into fulvic-like substances by microorganisms during the decaying process. Heterotrophic microorganisms promoted the release of algae-derived DOM and accelerated the degradation of DOM. The DOM born during algae blooms decaying process was eventually converted into humic-like substance, which was difficult to be degraded. We analyzed correlations of water quality, UV-vis spectrum, and EEMs parameters. Results showed that ORP was positively correlated (P<0.05) with DO. There was a significant negative correlation (P<0.05) between pH and DOC, which was consistent with the trend of the transformation to from DOC to DIC; C1 was positively correlated (P<0.05) with Fn355; and C2 was significantly positively correlated (P<0.05) with DOC and Fn280; C3 was positively correlated (P<0.05) with FI, BIX and ß:α. The variation trend of these spectral parameters was consistent with that of DOM components. In summary, with the analyses of water quality characteristics and spectral characteristics of DOM in overlying water during algae blooms decaying process, it was expected that our results could contribute to the further exploration of the dynamic migration and transformation of lake DOM and the changes of carbon cycling.

The Effect of Ni-ZSM-5 Catalysts on Catalytic Pyrolysis and Hydro-Pyrolysis of Biomass.

With the demand of energy and re-utilization of wastes, the renewable lignocellulosic biomass, has attracted increasing and significant attention for alleviating the growing energy crisis and environment problems. As main components of lignocellulosic biomass, lignin, cellulose, and hemicellulose are connected by hydrogen bond to form a compact skeleton structure, resulting the trenchant condition of biomass pyrolysis. Also, pyrolysis products of above three main constituents contain a large amount of oxygenates that cause low heating value, high corrosiveness, high viscosity, and instability. Meanwhile, zeolites are of considerable significance to the conversion of lignocellulosic biomass to desirable chemical products on account of fine shape selectivity and moderate acid sites and strength. Among numerous zeolites, ZSM-5-based catalysts have been most extensively studied, and the acidity and porosity of ZSM-5 can be tuned by changing the content of Si or Al in zeolite. Beyond that, doping of other metal elements, such as Mn, Co, Ni, Ga, Ce, Pt, into ZSM-5 is also an efficient way to regulate the strength and density of acid sites in zeolite precisely. This review focused on the recent investigation of Ni-modified microporous ZSM-5 used in catalytic pyrolysis of lignin and cellulose. The application of metal-modified hierarchical ZSM-5 is also covered.