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Synthesis of micro-mesoporous molecular sieve ZSM-5/SBA-15: tuning aluminium content for tert-butylation of phenol
No full textMicro-mesoporous ZSM-5/SBA-15 molecular sieve was derived from mesoporous molecular sieves SBA-15 by hydrothermal crystallization approach. The silica-alumina ratio significantly affects the structure and catalytic performance of ZSM-5/SBA-15. When the nSi/nAl is less than 25, the two-dimensional hexagonal pore structure of SBA-15 keeps intact with relatively low crystallinity of the pore wall. However, when the nSi/nAl is larger than 50, the SBA-15 pores are severely damaged. When nSi/nAl is 25, the catalyst ZSM-5/SBA-15 retains relatively good pore structure and shows excellent catalytic performance with 96.2% phenol conversion and 53.5% selectivity to 2,4-ditert-butyl phenol in the tert-butylation of phenol.Graphical Abstract SYNOPSIS Micro-mesoporous ZSM-5/SBA-15 molecular sieve was derived from mesoporous molecular sieve SBA-15 by hydrothermal crystallization approach. ZSM-5/SBA-15 (nSi/nAl=25) retains relatively good pore structure and shows excellent catalytic performance with 96.2% phenol conversion and 53.5% selectivity to 2,4-ditert-butyl phenol in the tert-butylation of phenol
Constructing Connected Paths between UiO-66 and PIM-1 to Improve Membrane CO2 Separation with Crystal-Like Gas Selectivity
No full textMost metal-organic-framework- (MOF-) based hybrid membranes face the challenge of low gas permeability in CO2 separation. This study presents a new strategy of interweaving UiO-66 and PIM-1 to build freeways in UiO-66-CN@sPIM-1 membranes for fast CO2 transport. In this strategy, sPIM-1 is rigidified via thermal treatment to make polymer voids permanent, and concurrently polymer chains are mutually linked onto UiO-66-CN crystals to minimize interfacial defects. The pore chemistry of UiO-66-CN is kept intact in hybrid membranes, allowing full utilization of MOF pores and selective adsorption for CO2. Separation results show that UiO-66-CN@sPIM-1 membranes possess exceptionally high CO2 permeability (15433.4-22665 Barrer), approaching to that of UiO-66-NH2 crystal (65-75% of crystal-derived permeability). Additionally, the CO2/N-2 permeation selectivity for a representative membrane (23.9-28.6) moves toward that of single crystal (24.6-29.6). The unique structure and superior CO2/N-2 separation performance make UiO-66-CN@sPIM-1 membranes promising in practical CO2 separations
Free-standing integrated cathode derived from 3D graphene/carbon nanotube aerogels serving as binder-free sulfur host and interlayer for ultrahigh volumetric-energy-density lithium-sulfur batteries
No full textThe actual applications of lithium sulfur (Li-S) batteries are significantly obstructed by limited cyclability and low volumetric-energy-density due to the shuttling effect of polysulfides and low mass density of sulfur cathode. Herein, we report a free-standing, compact, conductive and integrated cathode (G/CNT-S//G/CNT), constructed by compressing graphene/carbon nanotubes (G/CNT) aerogels, simultaneously serving as bi-functionalities of binder- and metal-current-collector-free sulfur host (G/CNT-S) and interlayer (G/CNT), for high volumetricenergy-density Li-S batteries. The G/CNT aerogels display three-dimensional interconnected porous network, large surface area (363 m(2) g(-1)) and high electrical conductivity (67 S m(-1)), which can endow the cathode with ultrahigh volumetric mass density (1.64 g cm(-3)) and superior electron-ion transport network. Meanwhile, the compressed ultralight G/CNT film can act as flexible interlayer for synergistically suppressing the polysulfide shuttling via both chemical interaction and physical restriction. Consequently, the compact cathodes, achieve high capacity of 1286 mAh g(-1) at 0.2 C and long-term cyclability with an extremely low decay rate of 0.06% over 500 cycles at 2 C. Most importantly, our compact cathodes represent unprecedented volumetric capacity of 1841 Ah L-1 and volumetric-energy-density of 2482 Wh L-1, both of which are the highest values of Li-S batteries reported to date. Therefore, this proposed strategy will open a new avenue for developing high volumetric-energy-density Li-S batteries
The synergistic effect between Ni sites and Ni-Fe alloy sites on hydrodeoxygenation of lignin-derived phenols
No full textThe catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds is a critical step in the upgrading of bio-oil. Here, bimetallic Ni-Fe nanoparticles supported on mesoporous carbon spheres (MCSs) were fabricated and applied in HDO of phenol. In comparison with monometallic Ni and Fe catalysts, the bimetallic Ni-Fe catalyst exhibited better performance for phenol HDO due to the formation of Ni-Fe alloy phase identified by X-ray powder diffraction (XRD) and Mossbauer spectroscopy techniques. Among several explored ratios, the catalysts with Ni/Fe ratio of 3/1 presented the highest cyclohexane yield. The reaction occurred in two consecutive steps: the hydrogenation of phenol to cyclohexanol and the further hydrogenolysis of cyclohexanol to cyclohexane. Kinetic studies showed that the hydrogenolysis of cyclohexanol controlled the overall reaction rate of phenol HDO due to the lower reaction rate of this step. Indeed, the turnover frequency (TOF) values of cyclohexanol normalized by surface metallic Ni sites exhibited a linear correlation with Ni-Fe alloy sites. The alloying of iron in the bimetallic Ni-Fe catalysts significantly enhanced the adsorption strength of cyclohexanol, which is the reason of the high activity of the Ni-Fe alloy particles. Thus, Fe-containing sites adsorb the hydroxyl species while Ni sites perform the H-2 activation, their synergistic effect plays a key role in phenol HDO process
Amphiphilic sodium alginate-vinyl acetate microparticles for drug delivery
No full textTo overcome the fast or burst release of hydrophilic drugs from hydrophilic alginate-based carriers, hydrophobic molecule (vinyl acetate, VAc) was grafted on alginate (Alg), which was further used to prepare drug carriers. Amphiphilic Alg-g-PVAc hydrogel beads were firstly prepared by emulsification/internal gelation technique for the loading of bovine serum albumin (BSA). Then, chitosan was coated on the surface of beads to form novel amphiphilic Alg-g-PVAc/chitosan (Alg-g-PVAc/CS) microcapsules. The BSA-loading amphiphilic Alg-g-PVAc/chitosan (Alg-g-PVAc/CS) microcapsules display similar morphology and size to the hydrophilic alginate/chitosan (AC) microcapsules. However, the drug loading and loading efficiency of BSA in Alg-g-PVAc/CS microcapsules are higher, and the release rate of BSA from Alg-g-PVAc/CS microcapsules is slower. The results demonstrate that the introduction of hydrophobic PVAc on alginate can effectively help retard the release of BSA, and the higher degree of substitution is, the slower the release rate is. In addition, the complex membrane can also be adjusted to delay the release of BSA. As a whole, amphiphilic sodium alginate-vinyl acetate/CS microparticles could be developed for macromolecular drug delivery