Propylene/propane mixture adsorption on faujasite sorbents

The adsorption of propylene and propane on zeolite NaX with and without a saturated (36 wt%) amount of CuCl have been investigated. The single component adsorption isotherms could be well described with a Dual-Site Langmuir model. The dispersion of CuCl results in a decrease of the maximum adsorption capacity of the zeolite for both components. For propylene a strong adsorption via π-complexation with CuCl is present, increasing the adsorption selectivity of the zeolite. The binary mixture (50:50) adsorption was determined via breakthrough/desorption experiments at 318, 358 and 408 K with a partial pressure of the two components between 0.8–54 kPa. For NaX the mixture loading could be well described with the IAS-theory and the single component isotherms, both qualitatively and quantitatively. A transition from an enthalpy controlled adsorption at lower loadings to an entropy affected adsorption at higher loadings was observed. The IAS-theory could only qualitatively describe the trends in the observed mixture adsorption for the CuCl/NaX adsorbent. The dispersion of CuCl in NaX results in a modest improvement of the adsorption selectivity for propylene over propane (from 3–7 to 15–30) but at the expense of a reduced capacity.     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

One-pot catalyst preparation: combined detemplating and Fe ion-exchange of BEA through Fenton's chemistry

BEA zeolite has been simultaneously detemplated and Fe-exchanged by treating the parent zeolite with a Fenton's-type reagent (Fe3+-H2O2) at low temperature. This one-pot process simplifies and speeds up considerably the preparation route. The catalyst shows excellent performance on N2O decomposition compared to conventionally prepared Fe-BEA.     

The XPS spectra of the metathesis catalyst tungsten oxide on silica gel

XPS spectra of supported and unsupported tungsten oxides before and after use in the metathesis reaction of propene are reported. It is shown that the broad peaks, usually measured for supported materials, are due to line broadening caused by differential charging. A new sample preparation technique is described which leads to a considerable reduction of the line broadening. Both XPS and X-ray diffraction show that in fresh catalysts a well-defined phase Of WO₃ is present. The reduction of the supported trioxide by propene to W₂₀O₅₈, as concluded from X-ray diffraction measurements, results in the formation of W^v - and/or W^IV -species in used catalysts. For unsupported WO₃ these lower valencies have been observed in the valence-band spectra.     

Elucidation of the Surprising Role of NO in N2O Decomposition over FeZSM-5

The decomposition of N₂O is strongly promoted by NO over steam-activated FeZSM-5. The promoting effect of NO is catalytic, and in addition to NO₂, ₂ is formed much more extensively at lower temperatures than in the absence of NO. The promotion effect only requires low NO concentrations in the feed, with no significant improvements at molar NO/N₂O feed ratios higher than 0.25. No inhibition by NO was identified even at a molar NO/N₂O feed ratio of 10, suggesting different sites for NO adsorption and oxygen deposition by N₂O. The latter sites seem to be remote from each other. Transient experiments using in situ FT-IR/MS and Multitrack over FeZSM-5 further elucidate the mechanism of NO promotion. The release of oxygen from the catalyst surface during direct N₂O decomposition is a rate-determining step due to the slow oxygen recombination, which is favored by high reaction temperatures. NO addition promotes this oxygen desorption, acting as an oxygen transfer agent, probably via NO₂ species. Adsorbed NO may facilitate the migration of atomic oxygen to enhance their recombination. Less than 0.9% of Fe seems to participate in this promotion. A model is proposed to explain the phenomena observed in NO-assisted N₂O decomposition, including NO₂ decomposition.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.     

Room temperature detemplation of zeolites through H2O2-mediated oxidation

Detemplation of zeolite beta has been successfully achieved at low temperature by controlled oxidation of the template using H2O2 and catalyzed by traces of Fe3+. With this approach, unlike calcination, the pristine structure of the material is well preserved; no extra-framework aluminium is formed.