146 research outputs found
Tetrahydropyridinium bromide: useful synthon to functionalized pyridines
No full text1-benzyl-5-(ethoxycarbonyl)-2,3,4,5-tetrahydropyridinium bromide undergoes ring contraction with a
series of nucleophiles, getting 2,2-disubstitued pyrrolidines. Moreover, from some of the new 2,2-disubstitued
pyrrolidines were synthesized spiro-pyrrolidine
Selective and Efficient Reduction of Nitrobenzene to Aniline catalyzed by AuNPs Embedded in a Nanoporous Crystalline Polymeric Support
No full textCongresso Divisione Chimica Industriale
Salerno, Settembre 2015
Selective and Efficient Reduction of Nitrobenzene to Aniline catalyzed
by AuNPs Embedded in a Nanoporous Crystalline Polymeric Support
Annarita Noschese1*, Antonio Buonerba1, Carmine Capacchione1, Stefano Milione1, Alfonso Grassi1
1 - Dipartimento di Chimica e Biologia, Università degli Studi di Salerno, Via Giovanni Paolo II - 84084 Fisciano (SA), Italy, and CIRCC-Bari, Italy
Abstract
Supported Gold Nanoparticles (AuNPs) efficiently catalyze both oxidation and reduction reactions. E.g. aerobic oxidation of alcohols and cross coupling reactions of alcohols leading to esters, amide, imine have been widely and successfully explored [1]. On the other side the reduction of nitroarenes to anilines using NaBH4, H2, silanes, formic acid, CO/H2O is a benchmark reaction for testing their catalytic performances in reduction reactions [2].
During reaserch efforts many supports have been exploited (carbon based supports, polymers, inorganic oxides) but their role is still under discussion. A semicrystalline porous polymeric support, consisting of syndiotactic polystyrene-co-cis-1,4-polybutadiene [3] has been successfully tested in our group and the AuNPS embedded in this polymer matrix (AuNPs-sPSB) were investigated in the reduction of nitrobenzene to aniline. The polymorphic behaviour of the host polymer matrix has been studied to optimize the catalyst performances. The nanoporous crystalline forms of the sPSB matrix, namely and , allowed a total conversion of nitrobenzene in 40 min at room temperature, with 100% selectivity in aniline. On the contrary the not permeable crystalline form gave a less reactive and selective catalyst; actually azobenzene and azoxybenzene were detected as intermediates compounds providing information on the cascade of the reduction reactions and the global reaction mechanism. Among the catalysts to date reported in the literature, the AuNPs-sPSB catalyst showed the highest activity (TOF=6000 h-1). The catalyst is very stable under the reaction conditions and reusable for at least three times without loss of catalytic activity.
Keywords: Gold Nanoparticles, Polymeric Matrix, Reduction.
* Corresponding author: [email protected]
References
[1] A. Corma, H. Garcia, Chem. Soc. Rev. 37 (2008) 2096
[2] S. Fountoulaki, V. Daikopoulou, P. L. Gkizis, I. Tamiolakis, G.S. Armatas, I. N. Lykakis, ACS Catal. 4 (2014) 3504; X. Liu, S. Ye, H.-Q. Li, Y.-M. Liu, Y. Cao, K.-N. Fan, Catal. Sci. Technol. 3 (2013) 3200; L. He, L.-C. Wang, H. Sun, J. Ni, Y. Cao, H.-Y. He, K.-N. Fan, Angew. Chem. Int. Ed. 48 (2009) 9538.
[3] A. Buonerba, C. Cuomo, S. Ortega Sánchez, P. Canton, A. Grassi, Chem. Eur. J. 18 (2012) 709; A. Buonerba, A. Noschese, A. Grassi, Chem. Eur. J. 20 (2014) 5478
Differential equations for real-structured defectivity measures.
No full textLet be a real matrix with all distinct eigenvalues. We propose a new method for the computation of the distance of the matrix from the set of real defective matrices, i.e., the set of those real matrices with at least one multiple eigenvalue with algebraic multiplicity larger than its geometric multiplicity.
For 0 < \eps \le w_\R(A), this problem is closely related to the computation of the most ill-conditioned \eps-pseudoeigenvalues of , that is points in the \eps-pseudospectrum of characterized by the highest condition number.
The method we propose couples a system of differential equations on a low rank manifold which determines the \eps-pseudoeigenvalue closest to coalesce, with a fast Newton-like iteration aiming to determine the minimal value \eps such that an \eps-pseudoeigenvalue becomes defective.
The method has a local behaviour; this means that in general we find upper bounds for . However, they usually provide good approximations, in those (simple) cases where we can check this.
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The methodology can be extended to a structured matrix, where it is required that the distance is computed within some manifold defining the structure of the matrix. In this paper we extensively examine the case of real matrices. As far as we know, there do not exist methods in the literature able to compute such distance
Permittivity estimation of layers beneath the northern polar layered deposits, Mars
No full textMartian Polar Layered Deposits, most likely dusty ice
are transparent to radar waves. In the North Pole bedrock
has been detected by MARSIS up to a depth about 2 Km,
whereas in the South Pole such interface has been located
at about 3.7 Km. The reflected signal is generally above
the noise and can be used to estimate the dielectric properties
of the bedrock. Assuming the permittivity of the first layer is
known, we use a simplified inversion method to extract the
bedrock relative dielectric permittivity as 4–9 below the
North PLD’s. These values are coherent with the basalt
nature and so the approach could be used to identify the
lithology beneath the Martian Poles
Rassegna storica salernitana. A.6, n.1/4(1945)
No full textLa Società Salernitana di Storia Patria aderisce al progetto EleA e autorizza la pubblicazione del fascicolo.A.6, n. 1/2(1945): V. Panebianco, La colonia romana di Salernum , P. 3; A. Carucci, La vergine Ifigenia negli Acta di S. Matteo, P. 39; A. Sinno, Episodi ignorati della rivoluzione popolare del 1647 in Salerno, P. 65; C. Noschese, Coincidenze e contrasti nei rapporti tra Amalfi e Salerno nell'età prenormanna, P. 157; P.C. Sestieri , Scavi della necropoli preistorica presso Paestum, P. 104; V. Panebianco, A proposito della capitale della confederazione lucana. P. 109; R. Guariglia, Appunti di viaggio di un soldato spagnuolo nel sec. XVII, P. 124; M.C. Concilio Un poeta dimenticato: Luigi Conforti, P. 126.A.6, n. 3/4(1945): A. Sinno, La Confraternita di S. Antonio dei Nobili e la sua opera di pietà per i condannati a morte (continua), P. 199; M. Fiore, Del luogo ove fu sepolto Masuccio Salernitano, P. 210; R. Trifone, A proposito dell’actus Lucaniae, P.230; R. Guariglia , Sant'Angelo in Grotta, P. 235; A. Schiavo, Note sul Duomo di Salerno, P. 241; M. Fiore, La Badia di S. Pietro a Corte, P. 141; Paolo Emilio Bilotti, P. 152; G. Antionani, Don Guglielmo Colavolpe O. S.B., P. 244; A. Balducci, L'Archivio della Curia Arcivescovile di Salerno / Regesto delle pergamene (945-1727), P. 24
Ladies and Gentlemen, start your engines!" Analysis codes waiting for the first JIRAM-Juno data of Jupiter hot-spots
No full textIn this contribution, we detail the retrieval scheme that has been developed in the last few years for the analysis of the spectral data expected from the JIRAM experiment on board of the Juno NASA mission [1], beginning from the second half of 2016. Our focus is on the analysis of the thermal radiation in the 5 micron transparency window, in regions of lesser cloud opacity (namely, hot-spots).
Moving from the preliminary analysis presented in Grassi et al., 2010 [2], a retrieval scheme has been developed and implemented as a complete end-to-end processing software. Performances in terms of fit quality and retrieval errors are discussed from tests on simulated spectra. Few examples of usage on VIMS-Cassini flyby data are also presented.
Following the suggestion originally presented in Irwin et al., 1998 [3] for the analysis of the NIMS data, the state vector to be retrieved has been drastically simplified on physically sounding basis, aiming mostly to distinguish between the 'deep' content of minor gaseous component (water, ammonia, phosphine) and their relative humidity or fractional scale height in the upper troposphere. The retrieval code is based on a Bayesian scheme [4], complemented by a Metropolis algorithm plus simulated thermal annealing [5] for most problematic cases.
The key parameters retrievable from JIRAM individual spectra are the ammonia and phosphine deep content, the water vapour relative humidity as well as the total aerosol opacity.
We discuss in extent also the technical aspects related to the forward radiative transfer scheme: completeness of line databases used to generate correlated-k tables, comparison of different schemes for the treatment of aerosol scattering, assumption on clouds radiative properties and issues related to the analysis of dayside data.
This work has been funded through ASI grants: I/010/10/0 and 2014-050-R.0
Liquid water detection under the South Polar Layered Deposits of Mars-A probabilistic inversion approach
No full textLiquid water was present on the surface of Mars in the distant past; part of that water is now in the ground in the form of permafrost and heat from the molten interior of the planet could cause it to melt at depth. MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) has surveyed the Martian subsurface for more than fifteen years in search for evidence of such water buried at depth. Radar detection of liquid water can be stated as an inverse electromagnetic scattering problem, starting from the echo intensity collected by the antenna. In principle, the electromagnetic problem can be modelled as a normal plane wave that propagates through a three-layered medium made of air, ice and basal material, with the final goal of determining the dielectric permittivity of the basal material. In practice, however, two fundamental aspects make the inversion procedure of this apparent simple model rather challenging: (i) the impossibility to use the absolute value of the echo intensity in the inversion procedure; (ii) the impossibility to use a deterministic approach to retrieve the basal permittivity. In this paper, these issues are faced by assuming a priori information on the ice electromagnetic properties and adopting an inversion probabilistic approach. All the aspects that can affect the estimation of the basal permittivity below the Martian South polar cap are discussed and how detection of the presence of basal liquid water was done is described
Numerical simulations of radar echoes rule out basal CO2 ice deposits at Ultimi Scopuli, Mars
No full textThe principal objective of the radar sounder MARSIS experiment is to look for ice and water in the Martian subsurface. One particular focus of investigations, since 2005, has been the search for basal liquid water in the south polar layered deposits (SPLD). Anomalously strong basal echoes detected from four distinct areas at the base of the deposits at Ultimi Scopuli have been interpreted to indicate the presence of bodies of liquid water in this location, beneath a 1.5 km thick cover of ice and dust. Other explanations for the bright basal reflections have been proposed, however, including the possibility of constructive interference in layered media. Here, we test this mechanism through simulations of MARSIS radar signals propagating in models of CO2-H2O ice sequences. We then compare the results to real MARSIS data acquired over Ultimi Scopuli, finding that no CO2-H2O ice model sequence reproduces the set of real data. The results of our work have implications in relation to the global CO2 inventory of Mars
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