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Scalable Palladium-Catalyzed Alkoxycarbonylation of Conjugated Dienes
No full textThe Pd(cod)Cl2-catalyzed alkoxycarbonylation of conjugated dienes to beta,gamma-unsaturated esters was approached by both intramolecular phosphinesulfonate L1 and intermolecular PPh3/PTSA in this study. However, the poor solubility of the Pd/ L1 complex and the labile monodentate Pd/PPh3 structure restricts the system efficiency, especially for the scale-up application. By contrast, the stable and well-soluble bidentate Xantphos system allows for the quantitative formation of 3-pentenoate (96%) on a gram scale within 6 h in weakly alkaline N-methylpyrrolidone (NMP), which also functions as a basic site to promote the rate-limiting alcoholysis step while reducing the dosage of ligand to a theoretical value
Migration and emission characteristics of trace elements in coal-fired power plant under deep peak load regulation
No full textThe trace elements (TEs) have caused great harm to the environment due to the large consumption of coal, and their emission from the coal-fired power plant (CFPP) has become a hot issue. The deep peak load regulation (DPLR) become a trend in the CFPP, which will affect the migration and emission of TEs. To explore the effect of the DLPR on the migration and emission characteristics of typical TEs in a 330 MW CFPP, the TEs field tests were carried out during the regulation period. Results showed that a higher load enhanced the migration of Pb, Mn, and Cr from bottom ash to fly ash, while it had little effect on the other TEs. More importantly, >99 % of TEs (93 % of Se) could be captured by air pollution control devices (APCDs), and the emission risk of Se and Mn increased with the load. Compared with the other TEs, it is particularly noteworthy that Se has a higher gaseous proportion in the flue gas, and the emission factor sharply increased from 165 MW to 297 MW. In addition, part of the particulate selenium transformed into a gaseous state across the ESP. This work contributes to understanding the migration characteristic of TEs during the DPLR process of CFPP and provides guidance for TEs control in the CFPP
Selective Separation of Lithium, Magnesium and Calcium using 4-Phosphoryl Pyrazolones as pH-Regulated Receptors
No full textEnsuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li+ from Ca2+, Mg2+, Na+ and K+. The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li+ at pH 6.0 was 94 % when Mg2+ and Ca2+ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner
CFD simulation for reduction of pyrolusite in fluidized beds
No full textIn this study, a CFD model coupled with heterogeneous flow structure, mass transfer equations, and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction behavior. Compared with the previous studies which ignore the volume change of solids phase, the influence of volume shrinkage on reaction and flow behavior is explored in this research. Volume shrinkage of pyrolusite is proved to be non-negligible in predicting the conversion rate. The negligence of volume shrinkage leads to the overestimation of conversion rate for its inaccurate estimation of surface area for reaction. Besides, the influence of volume shrinkage on the reaction is found smaller in the scaled-up reactor. (c) 2022 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved
Responses of microbial community to geochemical parameters on vertical depth in bioheap system of low-grade copper sulfide
No full textMonitoring of the microbial community in bioleaching system is essential for control process parameters and enhance the leaching efficiency. Due to the difficulty of sampling, microbial distribution, community succession and bioleaching activity along the vertical depth of bioleaching heaps remain unresolved. This study investigated the geo-chemical parameters and microbial community structure along a depth profile in a bioleaching heap and leachate. 80 ore samples at different heap depths and 9 leaching solution samples from three bioheaps of Zijin Copper Mine were collected. Microbial composition, mineral types and geochemical parameters of these samples were analyzed by 16S rRNA high-throughput sequencing and a series of chemical measurement technologies. The results revealed that the pH, Cu, Fe and the total sulfur contents were the major factors shaping the composition of the microbial communities in the bioleaching system. The extent of mineral oxidation increased as the sample depth increases, followed by the increasing of sulfur oxidizers. The abundance of sulfur and iron oxidizers including members of Acidithiobacillus, Sulfobacillus and Acidiferrobacter were significantly higher in the leaching heap than in the leaching solution, mean-while, they showed strong positive interactions with other members within the same genera and iron oxidizer Leptospirillum and Ferroplasma. Besides, Acidithiobacillus negatively interacted with heterotrophs such as Sphingobium, Exiguobacterium, Brevundimonas and so on. On the contrast, members of Leptospirillum and unclassified Archaea were significantly abundant in the leaching solution and revealed strong interactions with members of Thermoplasmatales. The main conclusion of this study, especially the leaching potential of microorganisms prevailing in bioheaps and their relationships with geochemical factors, provides theoretical guidance for future process design such as the control of processing parameters and microbial community in heap leaching
