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Recent progress in one-step synthesis of acrylic acid and methyl acrylate via aldol reaction: Catalyst, mechanism, kinetics and separation
No full textWith the gradual depletion of petroleum resources, the one-step synthesis of acrylic acid/ methyl acrylate from acetic acid/methyl acetate and formaldehyde via aldol reaction, instead of propylene selective oxidation, has stimulated researchers' interest. Current research in this field focus on catalyst modifica-tion, structure-activity relationships, catalytic mechanism and kinetics, and separation process design. The faced challenging problems are efficient catalyst development, mechanism-based kinetics calculation for reactor design and separation process optimization, which hinder the industrial progress, although great efforts have been made in the last decades. Therefore, it is necessary and meaningful to review the achievements as the basis for the further exploration and application in this area. This review aims to systematically summarize and analyze the catalytic performance and structure-activity relationships of developed catalysts, catalytic mechanism and kinetics, and separation process design, as well as sug-gest the prospective research. (c) 2021 Elsevier Ltd. All rights reserved
Solid polymer electrolyte with in-situ generated fast Li+ conducting network enable high voltage and dendrite-free lithium metal battery
No full textSolid polymer electrolytes (SPEs) with profound compatibility for high-voltage cathodes and reliable operation over a board temperature range are in urgent demand for the practical application of solid lithium metal batteries (SLMBs). In this study, a SPE containing interconnected fast Li+ conducting network was constructed via an in-situ hydrolysis of tetraethoxysilane (TEOS) within polyacrylonitrile (PAN) matrix to intensify the thermal stability of SLMBs. The in-situ formed interconnected inorganic network not only acts as a robust backbone for the whole SPE, but also furnishes sufficient continuous surfaces with Lewis-acidic sites, which will promote the dissociation of Li salt. As a consequence, the fabricated SPE exhibits an promising ionic conductivity of similar to 0.35 mS cm(-1), an attractive Young' modulus of 8.627 Gpa and a satisfactory lithium-ion transference number of 0.52. Solidstate nuclear magnetic resonance (S-NMR) and X-ray photoelectron spectroscopy (XPS) techniques were used to unravel the interactions among Li+ ions, PAN and as-formed SiO2. Based on the in-situ formed SPE, a Li/LiFePO4 SLMB presents an excellent cycle stability from 20 to 80 degrees C and a Li/LiNi0.6Mn0.2Co0.2O2 SLMB shows a steady discharge capacity of 173.1 mAh g(-1) with 93.8 % retention after 200 cycles at 4.3 V. Additionally, the Li/LiFePO4 pouch cell also delivers a stable cyclability and superior safety for practical applications. The design strategy of our work provides a rigid - flexible coupling dynamic strategy to fabricate SPEs for wide-temperature applicability and high energy density SLMBs
Recent progress of thermal conductive ploymer composites: Al2O3 fillers, properties and applications
No full textThermal conductive polymer composites attract lots of research due to the continuous miniaturization and multifunction of electronic equipment. As a common ceramic, Al2O3 owns relatively high thermal conductivity, high electrical resistivity and satisfactory cost performance, which is considered as the high-quality filler to prepare thermal conductive and electrical insulated composites. This paper reviews current progress in the development of Al2O3 reinforced polymer composites. We firstly summarize the preparation methods of spherical Al2O3, then heat conduction mechanisms and main factors affecting thermal conductivity are introduced. Next, we focus on the common research of Al2O3 in improving the thermal conductivity of polymers, including surface modification, filler hybridization and construction of Al2O3 network by various processing methods, and some emerging applications of thermal conductive polymer composites are introduced subsequently. After a critique of recent studies, we identify several outstanding issues must be addressed if higher thermal conductivity is fully realized
Recent progress of thermal conductive ploymer composites: Al2O3 fillers, properties and applications
No full textThermal conductive polymer composites attract lots of research due to the continuous miniaturization and multifunction of electronic equipment. As a common ceramic, Al2O3 owns relatively high thermal conductivity, high electrical resistivity and satisfactory cost performance, which is considered as the high-quality filler to prepare thermal conductive and electrical insulated composites. This paper reviews current progress in the development of Al2O3 reinforced polymer composites. We firstly summarize the preparation methods of spherical Al2O3, then heat conduction mechanisms and main factors affecting thermal conductivity are introduced. Next, we focus on the common research of Al2O3 in improving the thermal conductivity of polymers, including surface modification, filler hybridization and construction of Al2O3 network by various processing methods, and some emerging applications of thermal conductive polymer composites are introduced subsequently. After a critique of recent studies, we identify several outstanding issues must be addressed if higher thermal conductivity is fully realized
Flow behavior of granular material during funnel and mixed flow discharges: A comparative analysis
No full textThe drainage of granular assembly from a flat-bottomed silo can be in either funnel flow mode or mixed flow mode. The primary motivation of this work is to investigate whether there exist fundamental differences be-tween the rheological behavior of particles under these two discharge modes. The developments and evolutions of flowing zone and also the characteristics of particle velocity fluctuation during funnel and mixed flow dis-charges were analyzed and compared by performing 3D Discrete Element Method (DEM) simulations. For funnel flow discharge, the characteristic width of flowing zone at the early discharge state presented a clear history-dependent feature. For mixed flow discharge, the flowing zone sharply shrunk when the upper free surface of the material approached a critical height and the discharge mode then shifted to funnel flow mode. Discrete Fou-rier transform results demonstrate that resonant motion of particles appeared during both funnel and mixed flow discharges. The correlation analyses indicate that for these two flow modes, there both existed an intermediate region in the converging part of the flowing zone. Its upper boundary located at the position where the flowing zone started to converge along the vertical direction and was featured as the maximum particle compressive force. And its bottom boundary corresponded to the location of free-fall arch and acted as the source of the res-onant motion of particles. Our simulation results thus suggest that from the perspective of particle velocity fluc-tuation, there is no essential difference between granular flows under funnel and mixed discharge modes. (c) 2021 Elsevier B.V. All rights reserved
