Investigation of hydrogen and methane adsorption/separation on silicon nanotubes: a hierarchical multiscale method from quantum mechanics to molecular simulation

A combination of ab initio quantum mechanical (QM) calculations and canonical Monte Carlo (CMC) simulations are employed to investigate possible usage of single-walled silicon nanotubes (SWSiNTs) as a novel media for hydrogen and methane adsorption as well as their separation from each other. By fitting the force field, a Morse potential model is selected as an efficient potential to describe the binding energies between both hydrogen-SiNTs and methane-SiNTs obtained from ab initio calculations. Then CMC simulations are performed to evaluate the adsorption and separation behaviors of H₂ and CH₄ on the three different sizes of SiNTs including (5, 5), (7, 7), and (9, 9) SiNTs at ambient temperatures and pressures from 1 up to 10 MPa. As a comparison, the adsorption and separation of H₂ and CH₄ on the (8, 8) CNTs which are isodiameter with (5, 5) SiNTs are also simulated. Results are indicative of remarkable enhancement of H₂ and CH₄ adsorption capacity on the SiNTs compared to the CNTs, which arise from stronger van der Waals (VDW) attractions. In the case of methane adsorption on SiNTs, the stored volumetric energy exceeds the goal of the US Freedom CAR Partnership by 2010, which can not be achieved by methane compression at such low pressures. Moreover, simulation results indicate that SiNTs preferentially adsorb methane relative to hydrogen in their equimolar mixture, which results in efficient separation of these gases from each other at 293 K.     

Microwave-Assisted Synthesis of Quinoxalines,Benzoxazines, and Benzothiazines Under Solvent-Free Conditions

The addition of dialkyl acetylenedicarboxylate to o-phenylenediamine, o-aminophenol, and o-aminothiophenol under microwave irradiation in solventless system rapidly afforded quinoxaline, benzoxazine, and benzothiazine derivatives, respectively.     

Synthesis of Thio Analogues of Quinolone Antibacterials

A facile and rapid synthesis of thio compounds, analogues to ciprofloxacin, and norfloxacin is described.     

Acidified,Wet, Silica-Supported Tetrabutylammonium Periodate: A Convenient and Mild Reagent for Conversion of Thioamides to Their Corresponding Amides Under Solvent-Free Conditions

A series of thioamides are transformed to their corresponding oxo analogues in good to excellent yields with acidified, wet, silica-supported tetrabutylammonium periodate under solvent-free conditions.     

Al(HSO4)3 and Al2O3-SO3H as Efficient Catalysts for Modified Preparation of 3,4-Dihydropyrimidin-2 (1H)-ones/thiones

An environmentally friendly procedure for the preparation of dihydropyrimidinone derivatives or their sulfur analogues under thermal solvent-free conditions in the presence of aluminium hydrogen sulfate [Al(HSO₄)₃] and alumina sulfuric acid (Al₂O₃-SO₃H) as heterogeneous catalysts was developed.     

An efficient,expeditious, and diastereoselective one-pot pseudo-five-component reaction for the synthesis of new bis-Betti bases under catalyst-free conditions

A novel, diastereoselective, one-pot synthesis of new bis-Betti bases via condensation of dihydroxynaphthalene, two equivalents of aryl aldehydes, and two equivalents of 3-amino-5-methylisoxazole is reported. Conversion into the adducts was almost quantitative without the use of solvent or catalyst. The reaction conditions are very simple and enable easy isolation of the product.