查看更多>>摘要：? 2022 Elsevier Inc.In this study we used classical Suzuki polycondensation to prepare a pyridinyl-phenanzine (TPPQP) conjugated microporous polymer (CMP) that featured a spherical morphology with a large surface area (371 m2 g?1) and high thermal stability (Td10 = 625 °C; char yield = 81.7 wt%). The framework of the TPPQP CMP presented many dynamic pyridinic units could capture Ag+ ions from solution and facilitate their self-reduction to Ag nanoparticles, thereby forming Ag@TPPQP CMP nanocatalysts. The Ag@TPPQP CMP nanocatalysts were strong reducing agents for pollutant nitrophenols, converting them into safe amino forms at standard temperature and pressure with a high normalized rate of 19.4 mg?1 s?1. The pyridinic units in the TPPQP CMP structure played an important role in the catalytic reaction, interacting with the phenolic OH groups of p-nitrophenol to accelerate the reduction.
查看更多>>摘要：? 2022 Elsevier Inc.In order to reduce the loss of octane number during HDS process by enhancing the isomerization ability of HDS catalysts, the catalysis performance of 1-hexene isomerization on different introduced Br?nsted acid are studied based on density functional theory (DFT) and microkinetic method. The influence of acid strength and acid density on the adsorption and reaction of 1-hexene are investigated. There is obviously weaker adsorption strength of thiophene (the representation of sulfide in fluid catalytic cracking gasoline) than 1-hexene on Br?nsted acid, which indicates thiophene hardly affect the 1-hexene isomerization process. The reaction rate of 1-hexene isomerization on strong Br?nsted acid (HZSM-5/Al zeolite) is about 104 times higher than that on weak Br?nsted acid (HZSM-5/B zeolite). The increasing of Br?nsted acid density would bring the slight reduction of acid strength, which makes the 1-hexene isomerization reaction rate is slightly decreased, and the reaction rate on HZSM-5/2Al drops to about 76% of that on HZSM-5/Al. Through comparison, it is found that the reaction rate of 1-hexene isomerization at the strong Br?nsted acid reaction center is about 105 times that of 1-hexene hydrogenation saturation reaction rate at previous reported sulfur vacancy. Thus, it could be theoretically clarified that the introduction of strong Br?nsted acid active centers in the support of HDS catalysts is beneficial to the isomerization of n-olefins, which providing the theoretical guidance to design the catalysts with minimizing octane number loss during the HDS process of FCC gasoline.
查看更多>>摘要：? 2022 Elsevier Inc.To improve the capacity and energy density for Li-ion batteries, the composite of silicon and graphite has been regarded as the most promising alternative for next-generation anodes. However, the utilization of silicon has been limited by its large volume change and high manufacturing cost of nano silicon. Herein, the micron-size porous silicon is coated on the graphite and then encapsulated in carbon to form p-Si/G@C composite, in which the porosity and particle size of porous silicon are regulated by the element ratio and particle size of AlSi alloy. We find that the porous silicon with higher porosity and the smaller particle size shows better cycle stability and rate performance for p-Si/G@C electrode. Especially, by optimizing the porosity and particle size for porous silicon in the composite, the obtained p-0.8 μm Si20/G@C exhibits an initial reversible capacity of 649.4 mA h/g, the initial coulombic efficiency (ICE) of 81.85% and the outstanding cycle stability with the capacity retention of 83.1% after 500 cycles. With simple pre-lithiation, the ICE could be significantly increased to 97.16% and the cycle capacity becomes more stable. This rationally designed p-Si/G@C possesses the advantages of low production cost, simple synthesis process, which shows significant potential for practical use.
查看更多>>摘要：? 2021 Elsevier Inc.Broadband yellow-emitting phosphors are very attractive for warm white light-emitting diodes (WLEDs) used in solid-state lighting, backlight display, and related fields. In this work, we describe a room temperature, solution processable yellow-emitting phosphors for warm WLEDs using the chemically stable nanoscale hydrogen-bonded organic framework (HOF) PFC-1 as the host. By embedding the red-emitting dyes of rhodamine B (RhB), rhodamine 6G (Rh6G), 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM), and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in the green-emitting nano PFC-1, respectively, four types of single-matrix yellow-emitting nanocomposites were obtained. Due to the spectral combination of host PFC-1 and guest dyes, the obtained nanocomposites show broader emission spectra than that of the commercial yellow phosphor. Specifically, RhB@PFC-1 has a promising quantum yield of 17.8%. By coating the nanophosphors on the commercial blue LED chips (450 nm), bright sources of warm-white light were realized. It was found that the RhB@PFC-1 coated LED has an excellent color rendering index (CRI) of 85.6 and a correlated color temperature (CCT) of 4669 K at a drive current of 300 mA, while Rh6G@PFC-1 coated LED shows warm white light with a low CCT of 3100 K and a promising CRI of 75.4 K. This Dye@HOF strategy opens an avenue to developing yellow-emitting phosphors for the use in high color rendering warm WLEDs.
查看更多>>摘要：? 2022 Elsevier Inc.The organosilica membranes for gas separation have been studied for approximately ten years, but the separation performance of the membranes is restricted by the trade-off effect. Therefore, the objective of this work is to design H2-selective mixed matrix membranes by combining the good thermal stability of organosilica and remarkable H2/CO2 selectivity of ZIF-7. Herein, we synthesized ZIF-7 nanoparticles with an average size of 60 nm and investigated the effects of ZIF-7 doping content on the separation performance of organosilica membranes. Interestingly, it absolutely was found that with the doping content of ZIF-7 increased, H2 permeance of ZIF-7/BTESE (1,2-bis(triethoxysilyl)ethane) membranes remained basically unchanged, whereas the permeance of larger molecular gases displayed a dramatically drop. The membrane, when the molar ratio of ZIF-7: BTESE = 0.2, showed the remarkable H2/CO2 (22.7) and H2/N2 (159) selectivity, with a comparatively outstanding H2 permeance at 8.0 × 10?7 mol m?2 s?1·Pa?1. Our results firstly reveal that the doping of ZIFs could be strongly influenced by ZIF-7 doping contents, emphasizing the importance of doping of ZIFs for the further studies on nanoparticles-doped BTESE-derived membranes.
查看更多>>摘要：? 2022 Elsevier Inc.A direct hydrothermal synthesis strategy is developed to prepare the Cu–Fe-ZSM-5 zeolites by using the ethylenediaminetetraacetic acid disodium dihydrate (EDTA-2Na·2H2O) chelated Cu2+ and Fe3+ precursors as metal sources. During the crystallization, the metal chelates were spontaneously embedded into the ZSM-5 crystals and subsequently transformed to the zeolites encapsulated copper and iron species after removing the chelating agent via the high-temperature calcination. Rigorous characterizations indicate that the resulted Cu2+/Cu+ and Fe3+/Fe2+ species are formed ultra-small nano-composites with an average diameter of ～2.2 nm and highly dispersed in the ZSM-5 zeolite crystals. The acidity of the ZSM-5 zeolites is subtly modulated by the encapsulated Cu–Fe nano-composite. As expected, the as-prepared Cu–Fe-ZSM-5 exhibits outstanding catalytic performance for the selective catalytic reduction of NOx with ammonia (NH3-SCR) in the broad reaction temperature ranges of 220–480 °C, which is much better than the Cu–Fe/ZSM-5 prepared with the conventional wetness impregnation method. Furthermore, the resultant zeolites show high stability and good tolerance to H2O and SO2, and it is very competitive for practical application to eliminate NOx. The developed one-pot hydrothermal synthesis route by using EDTA-2Na·2H2O as chelating agent is very convenient and easily reproducible, providing a general guideline to design and fabricate the superior transition metal modified zeolite catalysts for NH3-SCR and the related reactions.
查看更多>>摘要：? 2022 Elsevier Inc.Development of economic routes for synthesis of hollow titanium silicalite-1 (TS-1) zeolite is of great importance in industry. However, there are still challenges to synthesize hollow TS-1 zeolite without anatase TiO2. In this work, a one-step strategy without mesoporogen by the solid-phase conversion method was successfully developed to synthesize anatase-free hollow TS-1. The appropriate low amount of TPAOH (TPA/SiO2 = 0.13) and the suitable crystallization temperature (170 °C) can not merely induce the formation of hollow structures, but also enable more titanium to enter the framework. Moreover, the transformation mechanism based on crystallization rate and dissolution rate was proposed according to the investigation of the transformation process. The hollow TS-1 with large cavities exhibits high catalytic activity and recycle stability in 1-hexene epoxidation. The efficient strategy reported in this paper will provide new opportunities for further promoting the industrial application of hollow TS-1.
查看更多>>摘要：? 2022 Elsevier Inc.A series of nanocrystalline ZSM-5 zeolites with abundant intercrystalline mesopores was fabricated by a hydrothermal crystallization method without any mesopore template. The ZSM-5 zeolite was characterized by XRD, XRF, N2 adsorption, NMR, SEM, TEM and NH3-TPD and used for the catalytic fast pyrolysis (CFP) of cellulose. The external surface area of the nanocrystalline ZSM-5 zeolite reached 146.6 m2/g, larger than the external surface area of conventional ZSM-5 (57.9 m2/g). The product yields of the CFP reaction were studied over different Si/Al ratios of nanocrystalline ZSM-5, and the aromatic yield of nanocrystalline ZSM-5 was generally higher than the aromatic yield of conventional ZSM-5. The relationship between the surface area, acid amounts and product yields was established by drawing a linear fitting curve. The results show that both pore structure and acidity have important effects on aromatic yield and coke yield. Aromatics are generated in micropores, and the increase in external surface area caused by reducing the particle size improves the pyrolysis of cellulose to generate bio-oil vapours, which further diffuse into micropores to generate aromatics.
查看更多>>摘要：? 2022 Elsevier Inc.In this work, several mesoporous γ-Al2O3 nanorods with high pore volume and narrow pore size distribution were controllable prepared via “gibbsite-AACH (ammonium aluminum carbonate hydroxide)” precursor route in a membrane dispersion microreactor. The effects of reaction temperature, (NH4)2CO3 concentration and calcination temperature on the samples were intensively studied. The highly uniformed morphology was assured due to the high mixing intensify in the membrane dispersion microreactor and the successful conversion of the precursor in the slurry. Under optimal conditions, these as-prepared γ-Al2O3 nanorods behaved high pore volume of 1.65 mL/g and narrow pore size distribution of 3–20 nm with a length and width of 150–200 nm and 30–60 nm, respectively. Furthermore, the adsorption experiment of the prepared samples were carried out under natural pH value, and the as-prepared sample of AACH-500 exhibited favorable adsorption performance for Congo red (CR) solution. The maximal adsorption capacity was up to 2006.7 mg/g, thus indicating that the as-prepared mesoporous γ-Al2O3 nanorods are in adsorption and other application potential of the field.
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