Infrared spectroscopic study of absorption and separation of CO using copper(I)-containing ionic liquids

Absorption of carbon monoxide by copper(I)-containing ionic liquids, [Cnmim][CuX2] (Cnmim = 1-alkyl-3-methylimidazolium, n = 2, 4, 6, X = Cl, Br, I) has been investigated using in situ high pressure infrared spectroscopy. For each liquid, observation of a ν(CO) band in the region 2075–2090 cm−1 indicates the formation of copper(I) monocarbonyl complexes, assigned as [Cu(CO)X2]−. The rate of growth and equilibrium intensity of the ν(CO) absorption is dependent on applied CO pressure. Binding of CO is reversible such that complete desorption occurs rapidly on heating above 100 °C and the liquids are robust over multiple gas absorption/desorption cycles. For the series of [C6mim][CuX2] salts the CO absorption ability follows the order Cl ≥ Br ≫ I. Selective absorption of CO from CO/H2 and CO/N2 gas mixtures is demonstrated by measuring the changes in headspace CO content upon absorption and desorption of gas. For [C6mim][CuCl2], a single absorb–vent–desorb cycle yields product gas containing ∼95% CO starting from a 1 : 1 CO/N2 mixture, increasing to ∼98% CO starting from a 4 : 1 CO/N2 mixture. This is particularly promising in view of the similar boiling points of CO and N2 that hinders their separation by cryogenic distillation

A methanol-only route to acetic acid

The combination of a Pd/CeO2 catalyst for in situ generation of CO, via methanol decomposition, with a copper mordenite methanol carbonylation catalyst has been shown to be a successful strategy for the development of a methanol-only halide-free route to acetic acid. There is a pronounced dependence upon reactor bed configuration. A stacked bed, in which the Pd/CeO2 decomposition catalyst is placed upstream of the Cu-MOR carbonylation catalyst, exhibits a much greater acetyls yield than a physical mixture of the two catalysts

Skewness and kurtosis of mean transverse momentum fluctuations at the LHC energies

The first measurements of skewness and kurtosis of mean transverse momentum (〈pT〉) fluctuations are reported in Pb–Pb collisions at sNN = 5.02 TeV, Xe–Xe collisions at sNN = 5.44 TeV and pp collisions at s=5.02 TeV using the ALICE detector. The measurements are carried out as a function of system size 〈dNch/dη〉|η|<0.51/3, using charged particles with transverse momentum (pT) and pseudorapidity (η), in the range 0.2<pT<3.0 GeV/c and |η|<0.8, respectively. In Pb–Pb and Xe–Xe collisions, positive skewness is observed in the fluctuations of 〈pT〉 for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of 〈pT〉 fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb–Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb–Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions

System-size dependence of the hadronic rescattering effect at energies available at the CERN Large Hadron Collider

International audienceThe first measurements of K*(892)0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at sNN=5.44 TeV and pp collisions ats=5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity (|y| &lt; 0.5) using the hadronic decay channel K*0 →K±π∓. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of K*0, and yield ratios of resonance to stable hadron (K*0/K) are compared across different collision systems (pp, p-Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of K*0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of K*0 in Xe-Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas–partial chemical equilibrium model