查看更多>>摘要：Ag-doped ZSM-5 and SSZ-13 zeolites were prepared synergistically by hydrothermal synthesis and liquid-phase ion exchange for the trace Xe and Kr capture by physical adsorption at room temperature and atmospheric pressure. The crystalline structure and textural characteristics of the as-synthesized samples were characterized by XRD, FT-IR, XRF, N-2 physisorption and SEM in detail. Adsorption isotherms of Xe, Kr and N-2 in the asprepared zeolites were determined at 298 K to assess the adsorptive selectivities of Xe/N-2 and Xe/Kr, and GCMC simulations were employed to investigate the adsorption mechanism of Xe in the Ag-exchanged zeolites. The results showed that Xe adsorption capacity and Xe/N-2 selectivity in Ag-SSZ-13 are up to 2.22 mmol/g and 116 while those in Ag-ZSM-5 are evaluated to 1.97 mmol/g and 85 respectively, which are enhanced by the introduction of Ag+ ions greatly. The GCMC simulation revealed that the simulated isotherms are all fitted well with the experimental isotherm at the low-pressure range, and the electronic charge transfers from the Ag+ to Xe result in the adsorbed Xe mainly around Ag+ ions in zeolites, confirming that Ag+ ions are the adsorption sites to strengthen the Xe adsorption in zeolites.
查看更多>>摘要：The promotion of Fenton process in organic wastewater treatment has been hindered by the disposal of large amounts of iron sludge derived from the excess addition of ferrous salt. The operation of the Fenton reaction could be maintained using trace level Fe-II through the effective acceleration reaction of active hydrogen. However, the H-2 which is the precursor of active hydrogen is insoluble in water. Herein, the composite catalyst Pd/MOF-808(Zr) was introduced into the H-2-Fenton system to enhance the adsorption and activation of this reducing gas. In this novel improved Fenton system called MHACF-MOF-808(Zr), the hydroxyl radical would be unceasingly produced based on the unceasingly recycling of FeII/FeIII at normal temperature and pressure. 15 mg L-1 sulfamethazine could be thoroughly degraded during 2 h reaction process in the initial condition of 60 mL min(-1) H-2, 20 mu mol L-1 Fe-II, pH 3, 20 mmol L-1 H2O2 and 2 g L-1 Pd/MOF-808(Zr). And so did 10 mg L-1 2,4-Dichlorophenol. The activity and stability of Pd/MOF-808(Zr) could be maintained after at least 6 consecutive reaction cycles. It provides new insight for improving the inherent shortcoming of the Fenton reaction which will generate large amounts of iron sludge.
查看更多>>摘要：Metal-Organic Framework (MOF) is a type of coordination networks with high surface area and tunable chemistry. MOFs are utilized for molecular recognition-related applications. The interaction of MOFs with molecules of interest occurs at the internal and external surfaces of MOFs, where internal surfaces are mostly inside the MOF pores. It is important to tune this interaction by pore engineering. We reviewed pore engineering at 4 different length scales: unit cell, multi-unit cells, mesoscale and macroscale. Additionally, we also discussed practical consequences of pore engineering on mass transfer, heat transfer and mechanical stability of MOF materials.
查看更多>>摘要：Alanine-modified chiral mesoporous silica (CMS) was firstly synthesized using chiral silane coupling agent (LAla-ICPTES or D-Ala-ICPTES) deriving from L-alanine or D-alanine, which was denoted as L-Ala-MSN and D-AlaMSN, respectively. The as-prepared CMSs exhibited highly ordered mesoporous structure with spherical morphology, huge specific surface area and pore volume, successful modification of alanine and opposite chirality, which was identified by transmission electron microscope (TEM), small angle X-ray diffraction (SAXRD), nitrogen adsorption/desorption measurement, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and induced circular dichroism (ICD). We also found that the biocompatibility of alanine modified CMSs was better than that of unmodified CMSs, which was confirmed by wettability test, degradation analysis, hemolysis test, protein adsorption test and evaluation of gastrointestinal irritation. Above all, the CMSs exerted chiral-selective delivery of achiral drug carvedilol (CAR) in simulated chiral environments. Pharmacokinetic studies revealed that L-Ala-MSN and D-Ala-MSN could significantly improve oral bioavailability of carvedilol (168.43% and 230.18% respectively), and D-Ala-MSN could delivery more drugs in vivo. This work has laid a theoretical foundation for rational design of chiral nano-drug delivery systems and promoted the application and development of CMSs in medicine.
查看更多>>摘要：A new method for the formation of permanent micropores in hyper-cross-linked networks is reported. This method is based on a template approach, using small molecules (4-methylaniline and 4-methylbenzaldehyde) as templates. These molecules are covalently attached via azomethine links to parent non-porous hyper-cross-linked polyacetylene networks prepared by chain-growth homo and copolymerization of ethynylated monomers. Highly efficient and well-defined postpolymerization hydrolysis of the networks leads to (i) cleavage of azomethine links and (ii) removal of the template molecules from the networks. Although up to 40 wt % of the mass of the networks are removed via hydrolysis, the hyper-cross-linked scaffold of the networks is not collapsed and micropores are formed in the networks. In this way, the parent non-porous networks are transformed into networks with permanent micropores (diameter similar to 1 nm) and a specific surface area up to 623 m(2)/g(-1). Simultaneously with the formation of micropores, functional groups (NH2, CHO) are introduced into the networks. The prepared microporous networks adsorb the model adsorptives (up to 1.73 mmol CO2/g and up to 6.53 mmol I-2/g.). The detemplating and micropores formation is confirmed by solid state NMR spectra and N-2 adsorption/desorption isotherms. The reported method of micropores formation could find a wider application for the preparation of microporous polymers with a well-defined texture and surface functionalization. Not only azomethine links but also many other groups with cleavable bonds could potentially be used for templating with covalently attached small molecules.
查看更多>>摘要：The wirelike, rodlike and corolla-like ZSM-48 zeolites with various SiO2/Al2O3 ratios (SARs) were successfully synthesized and exploited for the hydroisomerization of n-hexadecane (n-C-16). The influences of metal-acid balance, acid sites quantity, crystal morphology and textural properties on n-C-16 hydroisomerization performance were investigated primarily, via various characterization technique such as XRD, FT-IR, SEM, TEM, N-2 physisorption, NH3-TPD, and Py-IR. The C-Pt/C-A ratios of various catalysts were calculated for the quantified expression of the metal-acid balance, and the acid sites quantity was seriously crucial for the consecutive acid-catalyzed reaction after C-Pt/C-A ratios satisfied within an ideal range. Large external surface could accelerate the conversion rate, shorten the diffusional constraints and inhibit the cracking. The superiorities of satisfied C-Pt/C-A values (0.12-0.15), high concentration of acid sites (>230 mu mol/g) and large external surface (>120 m(2)/g) persuaded the Pt/Z(P)80, Pt/Z(H)60 and Pt/Z(H)80 samples to demonstrate wonderful hydroisomerization performance with outstanding yield around 80 wt% and excellent i-C-16 selectivity over 91 wt%. Although Pt/Z (W)80 and Pt/Z(R)80 samples owned the relatively small crystal, the gloomy catalytic activity of them was observed due to their relatively low concentration of acid sites and external surface. Moreover, the presence of "key-lock" mechanism was verified by the observations of 7-methyl-pentadecane (7MC15) dominating in isomer products.
NSTL
Elsevier