La lesión renal aguda (LRA) es una patología frecuente en el paciente en estado crítico, aumentando la mortalidad y las comorbilidades a corto y largo plazo. Determinar la incidencia, los factores de riesgo, las causas y la clasificación de la LRA en la unidad de cuidados intensivos pediátricos. Se llevó a cabo un estudio de tipo descriptivo, observacional y de cohorte, mediante la revisión de historias clínicas con diagnóstico de LRA que ingresaron a la unidad de cuidados intensivos pediátricos desde enero hasta agosto del 2014, con un análisis univariado. La incidencia de LRA fue del 16,9%. La LRA, según la escala de KDIGO, se presentó en estadio 1 en 14 casos (37,8%), en estadio 2 en 10 casos (27%) y en estadio 3 en 13 casos (35,2%). Los factores asociados a LRA son: la hipotensión, que se presentó en 27 pacientes (73%), con una p ≤ 0,01; el uso de inotrópicos en 32 pacientes con LRA (86,5%), con una p < 0,01. La ventilación mecánica en pacientes LRA se utilizó en 29 pacientes (78,4%) (p < 0,01). La sepsis fue la primera causa de falla renal, con una mayor frecuencia (48,6%, p = 0,05). Las pacientes con LRA presentaron mayor mortalidad, con 14 casos (37,8%, p < 0,01). Este es el primer estudio en el sur del país que muestra la clasificación de KDIGO para LRA. La lesión renal en pacientes críticos aumenta la mortalidad. Acute kidney injury (AKI) is one of the most frequent conditions in the critically ill patient, with increased short and long-term mortality and comorbidities. The published data about AKI in the paediatric intensive care unit are limited in our country. To determine the incidence, risk factors, and causes of the AKI in the paediatric intensive care unit. A descriptive, observational, cohort study was conducted using the review of clinical histories of patients with a diagnosis of AKI admitted to the paediatric intensive care unit from January to August 2014. A univariate analysis was performed on the data. The incidence of AKI was 16.9%; according to the Kidney Disease Improving Global Outcomes (KDIGO) scale, stage 1 was present in 14 cases (37.8%), stage 2 in 10 cases (27%), and stage 3 in 13 cases (35.2%). The factors associated with AKI were: hypotension in 27 patients (73%) with a P ≤ .01, the use of inotropes in 32 patients with AKI (86.5%) with a P < .01. Mechanical ventilation was used in 29 patients (78.4%) with AKI (P < .01). Sepsis was the primary cause of renal failure, with 48.6% (P = .05). The patients with AKI had higher mortality, with 14 cases (37.8%, P < .01). This is the first study in the south of the country that uses the KDIGO classification for AKI. Kidney injury in critically ill patients is associated with increased mortality.

Se estudio la influencia de la adicion de Sn sobre el desempeno catalitico del Ni soportado sobre alumina en la hidrogenacion selectiva del acetileno a etileno. Se prepararon catalizadores de Ni-Sn/Al2 O3 por impregnacion secuencial de una γ-Al2 O3 con soluciones de Ni(NO3 )2 x6H2 O y SnCl2 , variando la relacion atomica Sn/Ni entre 0 y 0,30. Los catalizadores se caracterizaron mediante reduccion a temperatura programada (TPR), quimisorcion de CO y titulacion con O2 . La reaccion se llevo a cabo a 65 °C y presion atmosferica. Los perfiles de TPR mostraron la reduccion del Ni(NO3 )2 x6H2 O a 338 °C y de especies de Sn cloradas a 470 °C. La dispersion del Ni fue baja para el catalizador de Ni/Al2 O3 , atribuible a su baja reducibilidad. La adicion de Sn disminuyo la dispersion, sin embargo, a relaciones atomicas Sn/Ni < 0,05 la actividad intrinseca del Ni mejoro, asi como tambien, su estabilidad catalitica. Este efecto benefico del Sn cuando se encuentra en bajas cantidades puede atribuirse a la modificacion electronica del Ni, debido a la formacion de particulas bimetalicas Ni-Sn

Mesoporous solids were used for hydrogen sulfide removal from stream H2S-Air. These solids were synthesized from a natural montmorillonite clay (STx-1) using the template method with a non-ionic surfactant and exchanged with Fe3+, Cu2+ and Fe3+-Cu2+; additionally, MgO/surfactant-clay solids impregnated with different contents of Zn, Fe-Zn and Cu-Zn were also prepared. The solids were characterized by using XRF, XRD, surface area, TPR and TGA-DTG. An increase in the surface area, pore volume and mesoporosity of STx-1 modified with surfactant was observed. The natural clay modified with surfactant and exchanged with copper cation enhanced the H2S breakthrough capacity. The STx-1 clay impregnated with zinc improved H2S removal, which increased with increasing the zinc content.

In this work the alkylation isotripper tower of Amuay Refinery (Falcón, Venezuela) was studied by means of simulation with PRO-II, Version 3.3 (Simulation Sciences lnc). The Hexamer algorithm was used to calculate the thermodynamic properties of hydrocarbon mixtures with hydrogen fluoaride. Simulations of the isostripper tower were done with design data from Universal Oil Products (UOP), up to date operational data and data for expanding capacity. A comparison of the simulation results with the design and operational data shows that in all cases product purity, temperature profiles and liquid and vapor compositions in each tray, as well as the values other operational variables, were very similar. From the simulation of the isostripper tower for higher loads, it was found that the feed could be increased up to 10615 kmol/h without hydraulic limitations in the main isostripper tower nor process limitations in the main equipment (pumps, condenser, reboiler, etc). This feed increase produce 730 kmol/h alkylate and $60.000 a day.

Se utilizó la hidrogenación de etileno como una reacción sonda para caracterizar catalizadores de PtSn/A12 0 3. Se estudió el efecto de la cantidad de Sn y el orden de impregnación de Pt y Sn en el Número de hidrógeno (NH), la cantidad de hidrógeno quimisorbido (HC) y la relación entre la cantidad de hidrógeno consumido (HT) y la cantidad de etano formado (E2 ) en la titulación con hidrógeno de etileno adsorbido (HT/E2). Los catalizadores se prepararon por impregnación húmeda incipiente de alúmina gamma con soluciones de h2PtC16 y SnC12 y contenían 0.5% en peso de Pt y cantidades de Sn. entre O y 0.45% en peso (relaciones atómicas entre O y 1.5). Se prepararon dos series de catalizadores variando el orden impregnación. En la primera serie, Pt-Sn/A1203, se impregnó primero con la solución de H2PtC16 y luego con SnC12; en la segunda serie, Sn-Pt/A1203, se impregnó primero con la solución de SnC12 y luego con la solución de H2PtCl6. Las nuestras fueron secadas a 393 K entre las impregnaciones. Se observó que el valor de NH para ambas series de catalizadores disminuyó con el aumento del contenido de estaño. La relación HT/E2 disminuyó con la adición de Sn para la serie Pt-Sn, mientras que para la serie Sn-Pt se mantuvo constante. La cantidad de hidrógeno quimisorbido (HC) en la serie de catalizadores Pt-Sn/Al 2 O 3 disminuyó con la cantidad de estaño agregado, mientras que para la serie de catalizadores Sn-Pt/A1203 aumentó con el Sn. Estos resultados son consistentes con una modificación química del Pt causada por la presencia de Sn, a través de la formación de agregados de Pt-Sn o .de la interacción con iones de Sn(II) en la superficie de la alúmina, tal como se ha reportado en la literatura.

Pl supported on a1umina and sWca was studied by ca adsorption using a FTIR. The effects on the metal stale of the type of Impregnation complex and treatment were studied . The ca adsorpUon was carried out by pulses allncreastng cataIyst coverage, The eo saluratlon of !he catalysl was compleled by passlng a ca flow. The adsorptlon and specu-a were done al room temperature under Ar flow. The catalyst were trealed in sUIi', The H2 trealmenl was carned oul al 673 K. The spectra show bands at 2123.2083. -2060 (main band). 1840 y 1800 cm'l. These bands are usually assigned to e -o stretching vibraUons of the Unear and bridge forms of adsorbed ca. The band at 2123 cm' } Is only observed Lo lhe spectra ofplaUnum supported 011 alumina prepared by impregnaUon wi!h H2Ptcls solutions . Il suggesls 1 A quien se debe enviar loda correspondenda referente a este articulo.

Interactions between chemisorbed carbon monoxide molecules and surface hydroxyl groups of the support in Pt/ Al2O3 and Pt/SiO2 catalysts were studied by using FTIR spectroscopy. Infrared spectra of the catalysts were measured both before and after the adsorption of CO. Due to the adsorption of CO, the intense 3700-3000 cm-1 band, corresponding to O-H stretching vibration of hydroxyl groups which are involved in hydrogen-bonding, was broadened towards lower frequencies and decreased in its intensity. The 1630 cm-1 band assigned to bending vibration of H-O-H angle decreased in its intensity for the hydrogen saturate catalysts and increased for the catalysts without hydrogen. These changes depend on the amount of adsorbed carbon monoxide. The 3743 cm-1 band, attributed to O-H stretching vibration of isolated silanol groups, was not modifed by chemisorbed CO. The spectral changes observed in the absorption bands of the bonded hydroxyl groups can be explained by a strong interaction through hydrogen bonding between the chemisorbed carbon monoxide and these hydroxyl groups. In the hydrogen-saturated samples, this interaction takes place mainly with the adsorbed water on the support, and in the hydrogen-depleted samples, with the structural hydroxyl groups. The chemisorbed CO molecules that interact with the surface hydroxyl groups vibrates at lower frecuency, causing the assymetry of the CO linear band.

La eficacia de las arcillas comerciales utilizadas en procesos de purificacion y decoloracion las ha hecho objeto de estudios para establecer el origen de su gran capacidad de adsorcion. En este trabajo se utilizan dos arcillas comerciales similares que difieren solamente en su acidez superficial medida por el procedimiento normalizado de titulacion acuosa con KOH. Sin embargo su comportamiento en presencia de olefinas. cicloolefinas y cicloparafinas es totalmente analogo, lo cual indica que este procedimiento no es adecuado para caracterizar su actividad. Los resultados obtenidos muestran que a las temperaturas de 273K y 298K las parafinas se adsorben solamente por fisisorcion, mientras las olefinas y cicloolefinas lo hacen fisica y quimicamente. Dado el papel que juegan los hidroxilos superficiales en el comportamiento de las arcillas y que las moleculas de hidrocarburo irreversiblemente adsorbidas exceden en decenas de veces el numero de posibles protones activos, se sugiere un proceso de polimerizacion cationica que se inicia con la formacion de un ion carbonio adsorbido. Se informa la formacion de coque a temperatura ambiente.

En este trabajo se estudió la hidrogenólisis del metilmercaptano utilizando la técnica de pulso como posible método de caracterización de catalizadores de hidrotratamiento del tipo CoMo/A1O3. Las experiencias se realizaron sobre un catalizador industrial de HDS y sobre una serie de catalizadores preparados en el laboratorio (r = Co/Co+Mo entre 0 y 1). Los catalizadores fueron activados con una mezcla de H2S/H2 (15%v/v) durante 2 h, y la reacción se realizó en un microreactor a 300º C y presión atmosférica. Con el catalizador industrial se estudió la influencia de la temperatura de activación (de 400 a 800º C) para la reacción de HDS del metilmercaptano. Se observó un ligero aumento de la actividad para la HDS entre 400 y 530º C. pero ésta disminuyó dráticamante cuando la temperatura de activación se aumentó hasta 800º C. Estos resultados concuerdan con los obtenidos por otros investigadores que estudiaron la actividad del catalizador para la HDS del tiofeno en condiciones de operación similares a las usadas en un reactor industrial. La serie de catalizadores preparados en el laboratorio, se activó a 400º C. Una curva tipo volcan fue obtenida cuando se representó la conversión para la HDS del metilmercaptano contra la relación atómica r, con un máximo de actividad para r = 0.2-0.3. A muy bajo contenido de cobalto (r = 0.022) se encontró una fuerte disminución de la actividad. La influencia del contenido de cobalto sobre la reacción de hidrogenólisis del metilmercaptano es similar a la observada por diferentes investigadores para la hidrogenólisis del tiofeno estudiada en diferentes condiciones experimentales sobre catalizadores de CoMo y NiMo soportados y no soportados. De nuestros resultados podemos concluir que la reacción de HDS del metilmercaptano puede ser utilizada como una reacción sonda para la caracterización de catalizadores CoMo/Al2O3.

The cooling water system of the Amuay refinery consists of two induced draft and cross flow cooling water towers, seven pumps and four supply pipes and their returns. This system supplies cooling water to the hydrotreatment complex, to the pipestill N° 5 and to the surface condensers of the power plant turbogenerators. This cooling water system showed constraints in the tower's cooling capacity to meet the design conditions, due mainly to a biological growth inside the towers, also increasing the need for cleaning more frequently the surface condensers of the power plant turbogenerators, indicating that the microbiological control was not suitable. In this study a thermal evaluation was performed to the towers, before and after the application of a biological control program by means of biocides and biodispersants, to decrease the growth of microorganisms. The towers were operating at 83% of their design cooling capacity, mainly because of the growth of algae inside them. After implementing the microbiological program, the cooling efficiency increased to 91%. Likewise, the heat transfer in the surface condensers of the power plant turbogenerators also increased.

The catalytic cracking unit in Lagoven's Amuay Refinery (Falcón, Venezuela) was started up in May 1991 after a revamping project to increase the unit capacity to 645 t/h (108 KBD). Signs of flooding were noticed in the fractionator, trays, such as sudden increases in pressure drops and variations in product flow. On several occasions, feeding had to be reduced to 615 t/h. The fractionator was simulated in order to study the cause of these problems and identify the process and hydraulic limitations that cause such unstabilities when 645 t/h are fed to the fractionator. PRO II, Version 3.3, was used to simulate the fractionator and standard correlations were used for hydraulic evaluation. It was found that the fractionator is hydraulically limited by high vapor loads. As a result, there is no flexibility to accommodate operational peeding changes. Some adjustments of the operation conditions and replacement of some trays with structured packing are recommended to improve fractionator operation.

Effects of the calcination and oxychirination on cyclohexane dehydrogenation activity of Ni/Al2O3 and Ni-SnAl2O3 catalysis were studied. Four Cl-free catalysts were prepared, two monometallic catalysts with 1.0 and 5.0% Ni by impregnation, and two bimetallic catalysts with 1.0%Ni-0.5%Sn and 5.0%Ni-2.5%Sn by step impregnation, both with Sn/Ni atomic ratio = 0.25. Calcination (in air) and oxychlorination (in air + CHCl3) treatments were carried out at 500°C for 1 h. The catalysts were characterized by temperature-programmed reduction (TPR). CO chemisorption al 22°C and oxygen titration at 400°C. The reaction was performed using a flow reactor al 300°C. All the catalysts presented very low Ni dispersions. The thermal Treatments, particularly the oxychlorination, caused a decrease in the dispersion and variations in the degree of reduction. These effects were dependent on the Ni content and the presence of Sn. The TPR profiles suggest the formation of bimetallic particles of Ni and Sn in the 5.ONi-2.5Sn catalyst subjected to calcination or oxychlorination. This catalyst showed a low activity, which was independent of the treatment. For the remaining catalysts. the oxychlorination produced more active catalysts than the calcination. E1ectronic effects of Sn on Ni explain the lower activity of bimetallic ensemblcs.

A natural smectite clay (STx-1, USA), was ion-exchanged with Al, Cr and Fe or pillared with the same cations. Samples combining these two treatments were also obtained. The prepared solids were characterized by X-ray fluorescence diffraction (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and N2 adsorption. The catalytic activity was evaluated by using the alkylation of benzene with 1-dodecene. XRF results showed an increase in the metal content, giving evidence that the metal was effectively exchanged or deposited over the starting material. Al- and Fe-pillared clays showed a significant increase of the surface area, but this was not ob served for the Cr-pillared one. Ion exchanged clays showed similar surface areas to that of the starting clay. From XRD results, only the Al-pillared clay gave an increase of the d-spacing. All catalysts showed low conversions to wards the product of interest, and this is perhaps attributed to lack of molecular accessibility in the clay gallery or that there are no strong acid sites able to catalyze the alkylation, but strong enough to induce 1-dodecene isomerization. Moderate conversions were observed (27% for the most active catalyst, Cr/ST-P-Al).

Dehydrogenation of n-butane over alumina-supported Pd and Pd-Ga catalysts was studied. Catalysts were prepared by incipient wetness impregnation with a Pd content of 0.66 wt% and atomic Ga/Pd ratios from 0 to infinity, using aqueous solutions of PdCl2 and Ga(NO3)(3). Fresh (uncalcined) and calcined catalysts were characterized by X-ray fluorescence spectroscopy (XRF), N-2 adsorption, temperature programmed reduction (TPR), CO and H-2 chemisorptions and O-2/H-2 titrations. n-Butane dehydrogenation reaction was carried out at 500 degrees C, atmospheric pressure and a H-2/C4H10 ratio of 10. An increase in the Pd dispersion with increasing Ga content was observed for the fresh catalysts, according to CO chemisorption results. H-2 chemisorption and H-2/O-2 titrations were not reliable methods to determine the Pd dispersion in the fresh catalysts. For the calcined catalysts with low Ga contents, the CO/Pd, H/Pd and O/Pd values were very similar, but different for those with the higher Ga contents. These differences were explained based on the presence of chlorine. Coke deposition produced the deactivation of the catalysts and inhibited hydrogenolysis reactions on Pd, favoring the dehydrogenation selectivity. In the fresh catalysts, the Ga addition caused an effect similar to that produced by coke, reducing the activity and increasing the dehydrogenation selectivity. In the calcined catalysts, the effect of Ga addition on activity was diminished by the calcination treatment. The combination of calcination and high Ga content led to a catalyst with enhanced activity and very high dehydrogenation selectivity. (C) 2009 Elsevier B.V. All rights reserved.