New pi-complexation adsorbents for propane-propylene separation

New adsorbents were prepared and tested for the separation of propane-propylene mixtures by adsorption. The ordered mesoporous material SBA-15 was used as the starting material for silver-ion deposition for pi-complexation with propylene. Two different loadings of silver were evaluated. Adsorption equilibrium and kinetic measurements of propane and propylene in the matrix (pure SBA-15) and the silver-modified adsorbents were performed at 323, 343, and 373 K. In this temperature range, the selectivity of propylene in one of the materials (Ag/SBA-15 = 0.5) is in the range 13-22 because the amount of propane adsorbed is very small, 0.095 mmol/g of propane versus 1.12 mmol/g of propylene at 100 kPa and 343 K. The diffusivity of both hydrocarbons is not seriously affected by the introduction of silver into the mesoporous structure.     

Synthesis and reactivity against Cp2TiCl of 4-isoprenyl-β-lactams. Trapping of N-titanoimidoyl radicals from cyanoformyl-2-azetidinones

A Staudinger reaction between methoxyketene and two different imines formed from citral afforded, after chemical transformation, the (E/Z)-4-alkenylepoxy-2-azetidinones 2, 3 and 4. These compounds, by reaction with Cp₂TiCl, did not cyclize to afford the expected polycyclic β-lactams, but the corresponding allylic alcohols 12, 13 and 15 were obtained instead. Unexpectedly, the treatment of cyanoepoxide (E)-3 with Cp₂TiCl also gave the hydroxyl aldehyde (E)-14 whose formation suggests to us that a possible radical reduction of the cyano group might have occurred, and we lastly succeeded in the capture of the N-titanoimidoyl radicals. The behaviour observed for the isoprenoid side chain in the Staudinger reaction, the reactions with Cp₂TiCl, as well as the trapping of N-titanoimidoyl radicals generated from benzocyanoformyl-2-azetidinones with the Ti(III) reagent, are discussed.     

Diffusion of Hf in α-Zr

The diffusion of Hf in -Zr has been studied in the temperature range 773–1115 K for the first time using the Rutherford backscattering technique. For this purpose we have used 250 Å thick Hf films, which were deposited on two types of Zr samples. Our results show that in both cases, the diffusion coefficients follow curved Arrhenius plots. For the pure Zr material the diffusion coefficients are systematically lower than for Zr samples of lower purity. These results indicate that the Hf diffusion mechanism is at least partially of extrinsic character. Finally it should be mentioned that the present data lie significatively below the values of self-diffusion in -Zr.     

VIP-2 —High-Sensitivity Tests on the Pauli Exclusion Principle for Electrons

The VIP collaboration is performing high sensitivity tests of the Pauli Exclusion Principle for electrons in the extremely low cosmic background environment of the underground Gran Sasso National Laboratory INFN (Italy). In particular, the VIP-2 Open Systems experiment was conceived to put strong constraints on those Pauli Exclusion Principle violation models which respect the so-called Messiah–Greenberg superselection rule. The experimental technique consists of introducing a direct current in a copper conductor, and searching for the X-rays emission coming from a forbidden atomic transition from the L shell to the K shell of copper when the K shell is already occupied by two electrons. The analysis of the first three months of collected data (in 2018) is presented. The obtained result represents the best bound on the Pauli Exclusion Principle violation probability which fulfills the Messiah–Greenberg rule.