Deactivation mechanism and regeneration of carbon nanocomposite catalyst for acetylene hydrochlorination

Acetylene hydrochlorination is an important coal-based technology for production of vinyl chloride, the monomer of one of the world mostly used plastics. Despite of the great potentials demonstrated for carbon-based catalysts to replace the toxic mercury chloride, the stability and the deactivation mechanism are rarely discussed, which is essential for real applications. Herein, we present a detailed study on the deactivation mechanism of nitrogen doped carbon based catalyst in acetylene hydrochlorination. The results show that the deactivation was likely caused by the carbon-like deposition over the catalyst, which can be regenerated with high temperature NH3 treatment. (C) 2017 Elsevier B.V. All rights reserved

Effect of Mining Thickness on Overburden Movement and Underground Pressure Characteristics for Extrathick Coal Seam by Sublevel Caving with High Bottom Cutting Height

Because the coal seam is particularly thick and the mining intensity is large, the mining of extremely thick coal seams often causes a wide range of disturbed fractures, which in turn induces the phenomenon of strong underground pressure such as induced support crushing and water inrush. Through theoretical analysis, laboratory similarity simulation test, and other methods, this paper studies the effect of mining thickness on overburden movement and underground pressure characteristics for extremely thick coal seams by sublevel caving with high bottom cutting height. Some conclusions can be drawn as follows: (i) under the “beam-hinged cantilever beam rocks” structure theory, the rock pillar thickness which needs to be controlled increases linearly as a function of mining thickness is achieved, and the reason of increased of support resistance in full-mechanized caving mining in extremely thick seams is explained in the theory; (ii) based on the results of the theoretical analysis and the lab simulation tests, the law of the abutment pressure peak is inverse to the full-seam mining thickness, and the distance between abutment peak and working face is proportional to the full-seam mining thickness, that is to say that the damage range of overlying strata increased; (iii) there are three working states of loading support in extrathick coal seams, such as normal circumstance, lower main roof pressure, and higher main roof pressure, meanwhile these states keep changing; (iv) under the guarantee of stope safety conditions, due to lower support strength, it will benefit the special thick seam top-coal caving under normal circumstance; (v) increasing the supporting strength can balance the impact loading under the lower main roof pressure, guaranteeing valid support for roof strata; (vi) by releasing high pressure, due to lower production, lower recovery rate of coal and other measures guarantee the stability of the stope support in the case of the higher main roof pressure

Design of foreign object recognition and positioning system for sorting robot of coal mine belt conveyor

Machine vision has a certain theoretical basis in target detection and recognition for sorting robot of coal mine belt conveyor. But current target recognition of sorting robot of coal mine belt conveyor is mainly aimed at coal-gangue recognition. There are few kinds of research on the recognition of foreign object targets causing conveyor belt penetration and tearing, and also few kinds of research on the precise positioning of target foreign object. In order to solve the above problems, a foreign object recognition and positioning system based on machine vision for sorting robots of coal mine belt conveyor is designed. The system can recognize and position different types and shapes of foreign objects on the conveyor belt. The image information of the foreign objects on the conveyor belt in real-time is obtained by adopting binocular vision, and the image is preprocessed. Image information is enhanced based on the Canny operator. The gray stretching method is used to improve image edge information to highlight the edge features of foreign objects on coal mine belt conveyor. The morphological method is used to extract foreign object shape features, and establish foreign object image feature sample library. The image feature matching method is used to solve the existing area of foreign objects to realize the detection, classification and recognition of foreign objects. On the basis of the successful recognition of foreign object type, the region of interest (ROI) of the target foreign object is established based on the edge feature value of the target foreign object. The coordinate conversion relationship is built between the camera, conveyor belt and target foreign object. The fast multi-target centroid calculation method is used to obtain the centroid coordinate of the target foreign object, so as to realize the positioning of the target foreign object. The experimental result of the system prototype shows that the foreign object recognition rate of foreign object recognition and positioning system for sorting robot of coal mine belt conveyor is not affected by the size, material, color and other factors, the system can realize the image acquisition, process, feature extraction, recognition and positioning of the target foreign object of coal mine conveyor belt. The recognition rate is above 92.5%, and the average error of the target foreign object positioning is about 3%

Thermophilic Nucleic Acid Polymerases and Their Application in Xenobiology

Thermophilic nucleic acid polymerases, isolated from organisms that thrive in extremely hot environments, possess great DNA/RNA synthesis activities under high temperatures. These enzymes play indispensable roles in central life activities involved in DNA replication and repair, as well as RNA transcription, and have already been widely used in bioengineering, biotechnology, and biomedicine. Xeno nucleic acids (XNAs), which are analogs of DNA/RNA with unnatural moieties, have been developed as new carriers of genetic information in the past decades, which contributed to the fast development of a field called xenobiology. The broad application of these XNA molecules in the production of novel drugs, materials, and catalysts greatly relies on the capability of enzymatic synthesis, reverse transcription, and amplification of them, which have been partially achieved with natural or artificially tailored thermophilic nucleic acid polymerases. In this review, we first systematically summarize representative thermophilic and hyperthermophilic polymerases that have been extensively studied and utilized, followed by the introduction of methods and approaches in the engineering of these polymerases for the efficient synthesis, reverse transcription, and amplification of XNAs. The application of XNAs facilitated by these polymerases and their mutants is then discussed. In the end, a perspective for the future direction of further development and application of unnatural nucleic acid polymerases is provided

Tuning of Ionic Liquid–Solvent Electrolytes for High-Voltage Electrochemical Double Layer Capacitors: A Review

Electrochemical double-layer capacitors (EDLCs) possess extremely high-power density and a long cycle lifespan, but they have been long constrained by a low energy density. Since the electrochemical stability of electrolytes is essential to the operating voltage of EDLCs, and thus to their energy density, the tuning of electrolyte components towards a high-voltage window has been a research focus for a long time. Organic electrolytes based on ionic liquids (ILs) are recognized as the most commercially promising owing to their moderate operating voltage and excellent conductivity. Despite impressive progress, the working voltage of IL–solvent electrolytes needs to be improved to meet the growing demand. In this review, the recent progress in the tuning of IL- based organic electrolyte components for higher-voltage EDLCs is comprehensively summarized and the advantages and limitations of these innovative components are outlined. Furthermore, future trends of IL–solvent electrolytes in this field are highlighted

Alternative Splicing Regulation of Anthocyanin Biosynthesis in Camellia sinensis var. assamica Unveiled by PacBio Iso-Seq

Although the pathway and transcription factor regulation of anthocyanin biosynthesis in tea plants [Camellia sinensis (L.) O. Ktze] are known, post-transcriptional regulation mechanisms involved in anthocyanin accumulation have not been comprehensively studied. We obtained the full-length transcriptome of a purple cultivar (‘Zijuan’) and a normal green cultivar (‘Yunkang 10#) of C. sinensis var. asssamica (Masters) showing different accumulation of anthocyanins and catechins through PacBio isoform sequencing (Iso-Seq). In total, 577,557 mapped full-length cDNAs were obtained, and 2,600 average-length gene isoforms were identified in both cultivars. After gene annotations and pathway predictions, we found that 98 key genes in anthocyanin biosynthesis pathways could have undergone alternative splicing (AS) events, and identified a total of 238 isoforms involved in anthocyanin biosynthesis. We verified expression of the C4H, CHS, FLS, CCOM, F3′5’H, LAR, PAL, CCR, CYP73A13, UDP75L12, UDP78A15/UFGT, UDP94P1, GL3, MYB113, ANR, ANS, F3H, 4CL1, CYP98A3/C3H, CHI, DFR genes and their AS transcripts using qRT-PCR. Correlation analysis of anthocyanin biosynthesis and gene expression results revealed that C4H1, FLS1, PAL2, CCR2, UDP75L122 and MYB113-1 are crucial AS transcripts for regulating anthocyanin biosynthesis in C. sinensis var. assamica. Our results reveal post-transcriptional regulation of anthocyanin biosynthesis in tea plants, and provide more new insights into the regulation of secondary metabolism

N-doping activated defective Co3O4 as an efficient catalyst for low-temperature methane oxidation

Development of non-noble metal catalyst for low-temperature methane oxidation is extremely important yet is still a challenge. Here, we construct a defective N-doped CoO by a facial N plasma engraving method. The obtained catalyst exhibits excellent catalytic activity with methane conversion rate of 6.5 μmol g s at reaction temperature of 342 °C and space velocity of 46,800 mL g h, which is about 7.3 times that of pristine CoO, and is among the highest active non-noble metal catalyst. The catalyst also shows high stability under hydrothermal environment. By systematic characterization and theory calculations, the superior performance could be attributed to the defective structure, enhanced redox property and highly exposed active sites. Meanwhile, N doping plays significant role in activating CoO by improving the electrophilicity of surface oxygen and lowering C–H bond activation energy. The study will bring significative insight into the design of advanced CoO catalysts for methane oxidation