Activation of waste tire char by cyclic liquid-phase oxidation

Activation of waste tire char was performed by successive cycles of liquid-phase oxidation followed by desorption in inert atmosphere at 650 °C. Significant differences in porosity development were found for the three oxidizing agents evaluated: nitric acid > hydrogen peroxide > ammonium persulfate. A linear increase of burn-off with the number of cycles was observed, reaching values between 63 and 90% after 15 activation cycles. Within the range tested, a higher concentration of the oxidizing agent (15 vs 30% v) led to higher burn-off, especially in the case of H2O2, however no differences were observed in terms of BET surface area (S BET) developed per unit of burn-off. SBET values around 750-400 m2/g were obtained by activation with HNO3 and H2O2, respectively. The activated carbons prepared by activation with HNO3 showed much higher mesopore volume (0.47-0.60 cm3/g) and some contribution of microporosity (0.03-15 cm 3/g). The mesopore size distribution in the samples activated with HNO3 (2-7 nm) was displaced to lower values than in the case of H2O2 (4-10 nm). The comparison with cyclic activation with air shows that liquid-phase oxidation provides higher porosity development, especially in the mesopore region but at the expense of higher burn-offThe authors greatly appreciate financial support from the Spanish Ministerio de Ciencia e Innovación (CTQ2009-09983) and the Ministerio de Economía y Competitividad (CTQ2012-32821

Platinum and N-doped carbon nanostructures as catalysts in hydrodechlorination reactions

Novel Pt catalysts supported on undoped and N-doped (1% N, w) carbons with well interconnected and nanostructured mesoporosity (Vmesopore = 0.65 cm3 g−1, SEXT = 730 m2 g−1) were prepared and tested in the hydrodechlorination of 4-chlorophenol in water at 30–70 °C. The growth of Pt nanoparticles was achieved using incipient wetness impregnation and a modified colloidal synthesis. Total conversion of 4chlorophenol and 100% selectivity to cyclohexanol was achieved. The remarkable activity in the hydrogenation of the phenol resulting from hydrodechlorination has not been reported before with Pt catalysts and it is of high interest because it maximizes detoxification. When the Pt NPs were synthesized by incipient wetness impregnation some influence of the N-doping of the support was observed in the size and electronic state of the NPs. However, highly reproducible Pt NPs were prepared by in situ colloidal synthesis regardless the nature of the support. In this last case similar activity was observed for the catalysts with undoped and N-doped carbon support, although the activity increased more with temperature for the later. Apparent activation energies of 15–25 kJ mol−1 were obtained for the disappearance of 4-chlorophenolThe authors also thank to Hexion Speciality Chemicals Iberica S.A. for providing the resol resin Bakelite®PF9934 FL. The authors thank financial support (CTQ2012-32821, CTQ2015-65491_R) and C. Ruiz-García for PhD grant (BES-2013-066085) to MINEC

Improving the activity in hydrodechlorination of Pd/C catalysts by nitrogen doping of activated carbon supports

Aqueous phase 4-chlorophenol hydrodechlorination reaction was used to study the effect of N-doping of activated carbon support on the catalytic activity of Pd catalysts. Activated carbon was doped using pyridine and 1,10-phenantroline, reaching nitrogen contents of 0.42-1.22 and 1.35-4.19 % (w), respectively. All catalysts (0.75 % Pd w, carbon basis) showed relatively large Pd nanoparticles (35-55nm), but they exhibited fast and complete 4-chlorophenol disappearance in batch experiments. In runs at 30°C 4-chlorophenol disappearance was mainly ascribed to hydrodechlorination, although N-doping of the support also increased adsorption. Catalysts with supports doped with pyridine yielded higher 4-chlorophenol disappearance rate in spite of lower bulk nitrogen content, however they showed higher concentration of nitrogen species at the external surface and lower loss of surface area during the doping. 4-chlorophenol disappearance rate was boosted at 60°C, with minor differences between catalysts with undoped and N-doped supports, but generation of cyclohexanone was only observed for the ones with doped support. Phenol generation simultaneous to 4-chlorophenol disappearance was observed with all the catalysts. However, subsequent hydrogenation to cyclohexanone ocurred only with the catalysts supported on N-doped activated carbonThe authors greatly appreciate the financial support of this research from the Spanish Ministry of Economy and Competitiveness through the project CTQ2012-3282

Characterization of Mycobacterium tuberculosis Beijing isolates from the Mediterranean area

<p>Abstract</p> <p>Background</p> <p>The Beijing lineage of <it>Mycobacterium tuberculosis </it>is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases.</p> <p>Results</p> <p>Only 1% (N = 26) of the isolates from two population-based studies in Spain corresponded to Beijing strains, most of which were pan-susceptible and from Peruvian and Ecuadorian patients. Restriction fragment length polymorphism typing with the insertion sequence IS<it>6110 </it>identified three small clusters (2-3 cases). Mycobacterial interspersed repetitive unit-variable number tandem repeat typing (MIRU-15) offered low discriminatory power, requiring the introduction of five additional loci. A selection of the Beijing isolates identified in the Spanish sample, together with a sample of Beijing strains from Italy, to broaden the analysis context in the Mediterranean area, were assayed in an infection model with THP-1 cells. A wide range of intracellular growth rates was observed with only two isolates showing an increased intracellular replication, in both cases associated with contained production of TNF-α. No correlation was observed between virulence and the Beijing phylogenetic group, clustered/orphan status, or resistance. The Beijing strain responsible for extensive spread on Gran Canaria Island was also identified in Madrid, but did not lead to secondary cases and did not show high infectivity in the infection model.</p> <p>Conclusions</p> <p>The Beijing lineage in our area is a non-homogeneous family, with only certain highly virulent representatives. The specific characterization of Beijing isolates in different settings could help us to accurately identify the virulent representatives before making general assumptions about this lineage.</p

Near-Infrared Polarimetric Adaptive Optics Observations of NGC 1068: A torus created by a hydromagnetic outflow wind

We present J' and K' imaging linear polarimetric adaptive optics observations of NGC 1068 using MMT-Pol on the 6.5-m MMT. These observations allow us to study the torus from a magnetohydrodynamical (MHD) framework. In a 0.5" (30 pc) aperture at K', we find that polarisation arising from the passage of radiation from the inner edge of the torus through magnetically aligned dust grains in the clumps is the dominant polarisation mechanism, with an intrinsic polarisation of 7.0%$\pm$2.2%. This result yields a torus magnetic field strength in the range of 4$-$82 mG through paramagnetic alignment, and 139$^{+11}_{-20}$ mG through the Chandrasekhar-Fermi method. The measured position angle (P.A.) of polarisation at K$'$ is found to be similar to the P.A. of the obscuring dusty component at few parsec scales using infrared interferometric techniques. We show that the constant component of the magnetic field is responsible for the alignment of the dust grains, and aligned with the torus axis onto the plane of the sky. Adopting this magnetic field configuration and the physical conditions of the clumps in the MHD outflow wind model, we estimate a mass outflow rate $\le$0.17 M$_{\odot}$ yr$^{-1}$ at 0.4 pc from the central engine for those clumps showing near-infrared dichroism. The models used were able to create the torus in a timescale of $\geq$10$^{5}$ yr with a rotational velocity of $\leq$1228 km s$^{-1}$ at 0.4 pc. We conclude that the evolution, morphology and kinematics of the torus in NGC 1068 can be explained within a MHD framework.Comment: 14 pages, 4 figures, Accepted by MNRA