Uncertainty Analysis of the Mercury Oxidation over a Standard SCR Catalyst through a Lab-Scale Kinetic Study

A kinetic study of the mercury oxidation across a standard composition SCR catalyst under simplified flue gas conditions (12 % CO₂, 5 % O₂, 5 % H₂O, 5 ppb Hg, 10 ppm of HCl in air) is carried out in a lab-scale packed-bed reactor. A thorough analysis is presented of the experimental error on the Hg oxidation rates, reaction orders, and activation energy propagated from the uncertainty in the measured mercury concentrations, thereby revealing several important limitations of these lab-scale experiments. The effects are investigated of flue gas composition, temperature, and space velocity on the Hg oxidation efficiency of the catalyst, and the reaction order of O₂ and Hg are derived together with the apparent activation energy. It is confirmed that O₂ is zeroth-order while Hg is first-order in terms of the Hg oxidation rate. An activation energy of 34 ± 7 kJ/mol is obtained. It is shown that the magnitude of the oxidation efficiencies increases with increasing amount of catalyst and temperature (from 150 to 350 °C)

Elasticity assessment of electrospun nanofibrous vascular grafts: a comparison with femoral ovine arteries

Development of successful small-diameter vascular grafts constitutes a real challenge to biomaterial engineering. In most cases these grafts fail in-vivo due to the presence of a mechanical mismatch between the native vessel and the vascular graft. Biomechanical characterization of real native vessels provides significant information for synthetic grafts development. Electrospun nanofibrous vascular grafts emerge as a potential tailor made solution to this problem. PLLA-electrospun nanofibrous tubular structures were prepared and selected as model bioresorbable grafts. An experimental setup, using gold standard and high resolution ultrasound techniques, was adapted to characterize in vitro the Poly(L-lactic acid) (PLLA) electrospun structures. The grafts were subjected to near physiologic pulsated pressure conditions, following the pressure-diameter loop approach and the criteria stated in the international standard for cardiovascular implants-tubular vascular prostheses. Additionally, ovine femoral arteries were subjected to a similar evaluation. Measurements of pressure and diameter variations allowed the estimation of dynamical compliance (C%, 10-2 mmHg) and the pressure-strain elastic modulus (EPe, 106 dyn cm-2) of the abovementioned vessels (grafts and arteries). Nanofibrous PLLA showed a decrease in %C (1.38 ± 0.21, 0.93 ± 0.13 and 0.76 ± 0.15) concomitant to an increase in EPe (10.57 ± 0.97, 14.31 ± 1.47 and 17.63 ± 2.61) corresponding to pressure ranges of 50 to 90 mmHg, 80 to 120 mmHg and 100 to 150 mmHg, respectively. Furthermore, femoral arteries exhibited a decrease in %C (8.52 ± 1.15 and 0.79 ± 0.20) and an increase in EPe (1.66 ± 0.30 and 15.76 ± 4.78) corresponding to pressure ranges of 50-90 mmHg (elastin zone) and 100-130 mmHg (collagen zone). Arterial mechanics framework, extensively applied in our previous works, was successfully used to characterize PLLA vascular grafts in vitro, although its application can be directly extended to in vivo experiences, in conscious and chronically instrumented animals. The specific design and construction of the electrospun nanofibrous PLLA vascular grafts assessed in this work, showed similar mechanical properties as the ones observed in femoral arteries, at the collagen pressure range.Fil: Suarez Bagnasco, D.. Universidad de la República. Facultad de Ciencias; UruguayFil: Montini Ballarin, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Cymberknop, Leandro Javier. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Balay, G.. Universidad de la República. Facultad de Ciencias; UruguayFil: Negreira, C.. Universidad de la República. Facultad de Ciencias; UruguayFil: Abraham, Gustavo Abel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Armentano, Ricardo Luis. Universidad Tecnológica Nacional; Argentina. Universidad de la República; Uruguay. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin