Showing papers by "M. Douglas LeVan published in 2014"
TL;DR: Compared to the zeolite NaX and Norit activated carbon, NU-125 has an increased excess capacity for oxygen of 237% and 98%, respectively, and could ultimately prove useful for oxygen storage in medical, military, and aerospace applications.
Abstract: We present a systematic study of metal–organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST-1 (Cu-BTC) and NU-125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST-1 and NU-125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU-125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications.
98 citations
TL;DR: Experiments and molecular simulations show that the pyridine modification reduces H2O adsorption while retaining substantial CO2 capacity under the conditions of interest for carbon capture from flue gas.
49 citations
TL;DR: In this article, a volumetric method was used to measure surface excess isotherms of oxygen and argon on a carbon molecular sieve, Shirasagi MSC-3R Type 172.
13 citations
TL;DR: The novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies with excellent crystallinity and enhanced photocatalytic activity compared with commercialTiO2 is reported.
Abstract: We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation.
10 citations
TL;DR: In this paper, a new method for developing adsorption equilibrium relations for gas mixtures is presented, where pure component isotherms are measured and described by appropriate isotherm equations, and binary measurements are performed with one component at a trace level and the other at a substantial loading.
Abstract: A new method for developing adsorption equilibrium relations for gas mixtures is presented. First, pure component isotherms are measured and described by appropriate isotherm equations. Then, binary measurements are performed with one component at a trace level and the other at a substantial loading, a condition we refer to as Henry’s law behavior with a second component in excess. The virial excess mixture coefficient method is used to obtain correction terms to the ideal adsorbed solution theory, with the coefficients determined solely from the Henry’s law data. Then, for data measured over the full composition space, the theory provides simple and accurate improvements to predictions of the ideal adsorbed solution theory. The method is implemented for the system of nitrogen and oxygen adsorbed on LiLSX zeolite.
9 citations
TL;DR: In this paper, the authors studied the transport of binary O2/Ar gas mixtures in a carbon molecular sieve (CMS) using concentration-swing frequency response and found that the O2 and Ar isotherms on this CMS were observed to be linear in the region over which frequency response experiments were performed.
Abstract: Transport of binary O2/Ar gas mixtures in a carbon molecular sieve (CMS) has been studied using concentration-swing frequency response. The rate data for this binary gas system are described well by the transport models (surface barrier for Ar and surface barrier plus micropore diffusion for O2) and parameters that were found to govern transport of the respective pure gases on the same CMS. These results suggest that transport of O2 is not impeded by the presence of Ar. However, the experimental data do not rule out the possibility of some enhancement of the O2 transport rate. Furthermore, O2 and Ar isotherms on this CMS were observed to be linear in the region over which frequency response experiments were performed, suggesting that the micropore diffusion component of O2 transport behavior is unaffected by the presence of Ar. Because transport of Ar in this CMS is much slower than O2, the dynamic response of this system owes the majority of its character to O2 adsorption, and the effect of O2 on Ar tran...
7 citations
TL;DR: The porosity and mechanical strength of the fabrics could be modified via compaction and/or exposure to alcohol vapor, and the SO2 sorption capacity was relatively independent of the sample pretreatment, unlike the capacity of pristine nanoparticles, which decreased when the powder was stored in a low relative humidity atmosphere.
Abstract: Good quality adsorbent fabrics were electrospun from slurries of zirconium hydroxide nanoparticles and polyvinyl butyral (PVB) in alcohols. The as-spun fabrics had very high porosity, about 80 vol%, and high zirconium hydroxide content, 50–95 wt%. The porosity and mechanical strength of the fabrics could be modified via compaction and/or exposure to alcohol vapor. SO2 sorption capacity of the fabrics was high at 1.6–1.9 mol/kg and was relatively independent of the sample pretreatment, unlike the capacity of the pristine nanoparticles, which decreased when the powder was stored in a low relative humidity atmosphere. The as-purchased zirconium hydroxide nanoparticles contained about 45 wt% of water, equivalent to the formula ZrO2·5.6H2O. In contrast, the electrospun composite fabrics contained only 25 wt% of mostly coordinated water, leading to the formula ZrO2·2.2H2O. The presence of PVB binder inhibited the rehydration/dehydration processes and stabilized the SO2 sorption capacity of the composite fibers. The electrospun fabrics could find applications as conformable, flexible filters in civilian and military applications.
4 citations
TL;DR: In this paper, two models for the interpretation of adsorption rate data measured using frequency response techniques are presented for the shell and core interpretation of the carbon molecular sieve (CMS) surface barrier with different levels of complexity.
3 citations