ABSTRACT
In this work, CAU-10-H@γ-AlOOH is prepared, and then UTSA-16 is loaded on CAU-10-H@γ-AlOOH to obtain UTSA-16@CAU-10-H@γ-AlOOH. Using the as-prepared composites as stationary materials by cryogenic gas chromatography at 77 K, while CAU-10-H@γ-AlOOH achieves the complete separation of ortho-H2 (o-H2) and D2 with a resolution R of 1.66 and a separation time t of 9.52 min, UTSA-16@CAU-10-H@γ-AlOOH achieves higher efficiency separation of hydrogen isotopes in a shorter separation time (4.56 min) with R = 1.7. Molecular simulation results show that CAU-10-H has both chemical affinity quantum sieving and kinetic sieving effects for H2/D2 at 77 K, and UTSA-16 can only exert the kinetic sieving effect. UTSA-16's load on CAU-10-H@γ-AlOOH weakens the adsorption of hydrogen isotopes, and the presence of Co2+ in UTSA-16 promotes the conversion of para-H2 to ortho-H2. In gas chromatography, H2 was preferentially desorbed from the system due to strong D2 adsorption caused by the chemical affinity quantum sieving effect and faster H2 diffusion caused by the kinetic sieving effect. These additive effects achieved efficient hydrogen isotope separation at 77 K.
ABSTRACT
In this work, Ni-4PyC was selected as the material for the separation of hydrogen isotopes H2/D2, and the mechanism of hydrogen isotope H2/D2 separation was investigated by molecular simulation. The results showed that the adsorption selectivity of Ni-4PyC for D2/H2 increased from 1.26 to 1.46 when the temperature was decreased from 77 K to 20 K, indicating that Ni-4PyC effected chemical affinity quantum sieving on D2/H2. Also, the diffusion rates of H2/D2 were different at different temperatures. At 20 K, the kinetic selectivity of D2/H2 reached 1.30, indicating that Ni-4PyC had a kinetic quantum sieving effect on D2/H2 at low temperatures. However, when the temperature was higher than 30 K, the diffusion rate of H2 was faster than that of D2, and when the temperature was 77 K, Ni-4PyC exhibited the kinetic sieving effect with a kinetic selectivity of 1.59 for H2/D2. Due to the chemical affinity quantum sieving and kinetic sieving effects of Ni-4PyC on H2/D2, the adsorption capacity of Ni-4PyC for D2 was better than that for H2 and the diffusion rate of H2 was faster than that of D2 at 77 K. Therefore, Ni-4PyC was expected to achieve the separation of H2/D2. In order to verify the accuracy of the theoretical calculation results, an Ni-4PyC@γ-Al2O3 composite material was synthesized by a liquid phase epitaxy method and was used to separate H2/D2 at 77 K in a 0.6 m × 2 mm chromatographic column. Under optimal separation conditions, the resolution R reached 1.84 with a separation time t = 7.47 min. In addition, Ni-4PyC@γ-Al2O3 showed excellent separation performances for different ratios of H2/D2 mixtures. The stationary phase was repeatable and reproducible.
ABSTRACT
The reaction of porous γ-Al2O3 particles acting as both a sacrificial template and an aluminum source with 1,4-naphthalene diacid (H2NDC) resulted in the formation of γ-AlOOH@Al(OH)(1,4-NDC) composites, in which ZIF-67 was then loaded by the in situ crystallization method, leading to the formation of γ-AlOOH@Al(OH)(1,4-NDC)@ZIF-67 composites. The deliberately designed composite was used to separate H2/D2 at 77 K in a 1 m chromatographic column. The results demonstrated that the optimized composite can achieve the effective separation of H2/D2 in gas chromatography due to the additive effects of kinetic sieving and chemical affinity quantum sieving of Al(OH)(1,4-NDC) and ZIF-67. By optimizing chromatographic separation conditions, the resolution R reached 2.02 with the separation time t = 7.72 min. The composite also showed satisfactory repeatability and reproducibility.
ABSTRACT
A new optimized multicomponent composite, Na2Cr2O7/Na2CrO4/NaCl/MOF-74(Ni)@γ-Al2O3 (S1/S2/S3/MOF-74(Ni)@γ-Al2O3. Na2Cr2O7 = S1, Na2CrO4 = S2, NaCl = S3), was prepared and used as a gas chromatography stationary phase for the separation of H2 and D2 isotopes. Under the optimal chromatographic separation conditions, the resolution of the packed column for the separation of H2/D2 was 2.87, and the separation time was 7.15 min at 77 K. The control experiments showed that in the multicomponent composite, MOF-74(Ni), which has a chemical affinity quantum sieving effect, played a major role in the separation of H2/D2. As the support of MOF-74, γ-Al2O3 enhanced the mechanical strength of MOF-74 and reduced the gas resistance. The presence of Na2CrO4 in the column increased the H2/D2 separation resolution, while the presence of NaCl reduced the separation time, produced more symmetrical and narrow chromatographic peaks of Gaussian distribution. Furthermore, by optimizing the ratio of NaCl and Na2CrO4, (S2/S3/MOF-74(Ni)@γ-Al2O3) composite with a NaCl/Na2CrO4 mass ratio of 0.7:1 was synthesized and used to realize the high-resolution separation of H2/D2 (R = 2.56) with a short separation time (t = 5.91 min). Both composites also showed excellent repeatability/reproducibility for separation.
Subject(s)
Metal-Organic Frameworks , Aluminum Oxide , Hydrogen , Isotopes , Nickel , Reproducibility of ResultsABSTRACT
Attachment of MOF-5 particles on the surface of carboxymethylated non-woven chitosan cloth (denoted MOF-5@chitosan) was achieved by a layer-by-layer technique in an alternating bath of Zn(OAc)2·2H2O and terephthalic acid solutions. Afterwards, silver nanoparticles were formed/loaded within the resulting MOF-5@chitosan by irradiating at 350 nm wavelength the composite immersed in an aqueous solution of silver nitrate of different concentrations, leading to the formation of ternary composites (denoted Ag@MOF-5@chitosan) which were thoroughly characterized by various techniques. Decontamination of HD over the composites was systematically studied and the results showed that decontamination efficacy increased with the increase of silver amount. The decontamination rate constant and half-life of HD were found to be 0.011 min-1 and 63.0 min over the optimal composite, respectively. Remarkably, attachment of the silver nanoparticles and MOF-5 on the chitosan cloth surface did not interfere with chitosan's original hemostatic capability that was confirmed through the arterial hemostasis of rats. It is expected that the multifunctional composite material can find practical applications in the fields of hemostasis, sterilization and chemical war agent decontamination.
ABSTRACT
Propane/propene separation is among the most energy-intensive separation processes in the petrochemical industry. Separation based on adsorption on a nanoporous material (e.g., zeolites) has spawned new ideas for this process. Therefore, we conducted grand canonical ensemble Monte Carlo simulations to investigate the adsorption and separation of propane and propene in one-dimensional (ATS, MOR, and AWO), two-dimensional (MWW, FER, and BOG) and three-dimensional (MFI, BEA, FAU) zeolites. The computation of pure components indicates that the adsorption capacity is affected by the zeolite pore diameter, dimensionality, and isosteric heat. For a given diameter, three dimensional zeolites exhibit better adsorption properties than two or one-dimensional zeolites. Zeolites with diameters ranging from 4.8 Å to 5.4 Å show high propane and propene affinity. In binary mixture simulations, the separation capacity of propane and propene increases with elevated pressure and decreased temperature. Among these zeolites, AWO exhibits the best separation performance due to its eight-ring window channel, which is consistent with experimental results. Thus, our results provide better understanding on propane and propene adsorption and separation in different zeolites, as well as insight into how production conditions could be upgraded.