Dynamic Modelling and Optimisation of Large-Scale Cryogenic Separation Processes

In this work, the open loop dynamic optimisation of a large-scale natural gas processing plant is performed. A rigorous differential-algebraic equation (DAE) model has been formulated to represent main plant units, such as shell and tube heat exchangers, highpressure separator and demethanizing column. In the shell and tube heat exchangers, the hot stream partially condenses and equations to consider the partial condensation of the fluids have been included. A rigorous index one model for the demethanizing column has been developed. The DAE optimisation problem is solved with a simultaneous approach, in which both state and control variables are discretised and the original DAE optimisation model is transformed into a large-scale nonlinear problem (NLP), which is solved using Sequential Quadratic Programming (SQP) methods. Optimal profiles have been obtained for main operating variables to achieve an enhanced product recovery.Fil: Rodriguez, Mariela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Bandoni, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Díaz, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Alcohol decomposition on basic/acid lignin-derived submicron diameter carbon fibers

The use of lignin, the second most abundant polymer in nature, along with a simple and versatile technique, electrospinning, represents an advantageous and promising approach for the preparation of carbon fibers. In previous studies, we have demonstrated that the incorporation of H3PO4 to the initial lignin solution allows for shortening the carbon fibers preparation process and that the resulting carbon fibers present P-surface groups that are of great interest for heterogeneous catalysis. Different carbon fibers catalysts have been prepared by electropinning of Alcell lignin in the absence or presence of H3PO4 as chemical activating agent. Carbonization at different temperatures between 500 and 1600 ºC allows for preparing carbon fibers with a high variety of porosity and chemical surface properties. Diverse oxygen surface groups are presented on the carbon catalysts surface. The isopropanol decomposition has been used as a catalytic test to study the acid or basic character of the prepared carbon fibers. Carbon fibers without phosphorus surface groups generate acetone as the main product of the isopropanol decomposition reaction, from 400 to 600 ºC, suggesting the basic character of these catalysts. On the contrary, phosphorus-containing carbon fibers show high acid character, producing selectivity to propylene of 100 % at temperatures between 250 and 350 ºC. The most acid carbon fiber catalyst produced a high selectivity to ethylene and dimethyl ether for the decomposition of ethanol and methanol, respectively. The conversion enhancement that the presence of oxygen in the gas phase produced for all these reactions was also studied.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MINECO (PTA2015-11464-I)

Carbon materials as template for the preparation of mixed oxides with controlled morphology

Resumen del libro de actas del Congreso: 5th Czech-Italian-Spanish Conference on Molecular Sieves and Catalysis, celebrado en Segovia del 16 al 19 de junio de 2013Bulk mixed oxide catalysts are widely used for many applications, such as catalysts for selective oxidation processes, electrocatalysts for fuel cells, gas sensors, and solid oxide electrolysers for the production of hydrogen. VPO (vanadium and phosphorous oxides) are one of the bulk mixed oxide materials which are of interest nowadays since they are active catalysts for saturated hydrocarbon activation. With the conventional synthesis procedures for preparing bulk mixed oxides is really difficult to control the morphology and the porous structure of these materials. In practice, there are just a few works about the synthesis of mixed oxide materials with controlled morphology. The aim of this work was to describe new approaches for the preparation of VPO mixed oxides materials with spherical morphology. A carbon material was prepared using cellulose as starting material by hydrothermal treatment with phosphoric acid at 200ºC and carbonized at 500ºC. SEM analysis showed that carbon spheres with diameter up to 0.5 m were prepared by this procedure. These phosphorous containing carbon material was impregnated with the appropriate amount of vanadium oxide species in order to obtain a monolayer of VOx species on the surface of the carbon materials following a procedure described previously (1). By this manner, a carbon supported VOx material with spherical morphology was obtained (VPO/Csph). The calcination of this material was optimized in order to obtain VPO spheres with diameter up to 1-2 m and with BET area values close to 100 m2/g. Figure 1 shows a SEM image of this sample (VPOsph). The presence of vanadium pyrophosphate phase, which has been described as the active phase of this catalytic system, was identified by XRD and Raman spectroscopy. Thus, the chemical composition as well as the morphology and porous structure of these new spherical materials makes them quite promising as catalysts

Kinetic study of methanol dehydration over Zro2 supported-activated carbons

The growing concerns about climate change and energy consumption have been the driving force in seek of alternative fuels such as DME, mainly produced via methanol dehydration over a solid acid catalyst. The use of activated carbons for this aim has been little studied up to date. Only a few studies can be found in the literature, reporting all of them materials with a low thermal stability of the acid surface groups, which results into a fast deactivation of the catalyst. In this work, the preparation of activated carbons via chemical activation with phosphoric acid, their modification with different ZrO2 loads, and their application as methanol dehydration catalysts have been studied. The catalytic results showed that the best methanol conversion and selectivity towards DME were achieved with the activated carbon prepared with an impregnation mass ratio value (H3PO4 /precursor) of 2 and an activation temperature of 800 ºC, loaded with a 7 % (wt) of ZrO2 . This catalyst exhibits high steady state methanol conversion values even at temperatures as high as 400 ºC (XCH3OH= 80%, 0.1 g·s/μmol, PCH3OH= 0.08 atm in helium), keeping a selectivity to DME higher than 96%. The effect of oxygen in the reaction atmosphere was also analysed. In this sense, an increase of 15 % in the DME yield was obtained when using air instead of helium as reaction atmosphere (350 ºC, 0.1 g·s/μmol, PCH3OH= 0.04 atm). A kinetic study has been carried out on this catalyst in which two mechanisms (Eley Rideal and Langmuir Hinshelwood) for methanol dehydration have been analysed. The models proposed also consider the presence of oxygen in the reaction media.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MECD (FPU13/02413)

High temperature treatments of porous activated carbon

The use of biomass waste for the preparation of activated carbon is of great industrial interest for reducing costs and increasing the sustainability, especially in the field of energy storage. A high temperature treatment is required to obtain a more ordered carbon material, thus increasing its conductivity. However, this high temperature treatment entails as a disadvantage a significant reduction in porosity. Therefore, a method to prepare activated carbons with a high porosity development as well as high conductivity could be of great interest for many applications. The aim of this work is to analyze the possible influence of phosphorus compounds on the physical-chemical properties of different carbon materials thermally treated at relatively high temperatures (1600 ºC). With this goal, it has been prepared activated carbons from different precursors (olive stone, lignin and hemp) and different conformations (powder, fibers and monoliths) by physical and chemical activation, with CO2 and H3PO4, respectively. Once the different activated carbon materials were prepared, they were thermally treated at 1600 ºC under inert atmosphere. The different samples were characterized by N2 and CO2 adsorption at 77 and 273 K, respectively, XPS, XRD and Raman techniques. The oxidation resistance was also evaluated in a thermogravimetric balance. High temperature treatments of activated carbon without the presence of P surface groups produced an important contraction of the porosity (from 900 to 150 m2 g-1). However, temperature treatments of phosphorus-activated carbon allowed for preparing carbon materials with a relatively high structural order and a well-developed porosity (c.a. 1100 m2 g-1), with a significant contribution of mesoporosity. These results suggest that these P-surface groups are responsible for the low contraction observed for the porous structure, avoiding, in a large extent, its collapse.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MINECO (PTA2015-11464-I)

Modification of the morphology, porosity and surface chemistry of lignin-based electrospun carbon materials

Lignin is a biopolymer that can be found as the main component of plants. It is obtained as a coproduct in the papermaking and biofuel industries. Owing to its high carbon and aromatic content, high availability and reduced cost, it is an excellent precursor for the preparation of highly valued carbon materials. Electrospinning is a suitable top-down technique for the preparation of polymeric fibers using high voltage electrical fields and polymer solutions of proper viscosity and conductivity. Organosolv lignins, which are extracted from lignocellulosic biomass using organic solvents, are soluble in ethanol, obtaining a solution that matches the requirement of the electrospinning process. In this way, it is possible to produce lignin-based porous carbon fibers using a coaxial electrospinning device [1]. This contribution summarizes our findings about the preparation of carbon materials with different morphologies and composition by processing lignin using electrohydrodynamic forces. Lignin spheres, beaded fibers, straight fibers, beaded tubes and straight tubes are obtained by using coaxial and triaxial spinnerets that allows the electrospinning of two or three different solutions at once [1], Fig. 1. Thermal stabilization in air is needed in order to avoid melting of lignin fibers during carbonization. Stabilization times of 48-96 hours are usually required in this step, decreasing the sustainability of the production process. Phosphoric acid can be added in small amounts in the lignin solution, shortening the time for achieve a successful thermostabilization of the fiber [2]. The carbonized materials show narrow microporosity and large surface area values (SBET from 600 to 1000 m2g-1) and additional pore size and volume can be developed by controlled gasification.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This work was supported by the Spanish Ministry of Economy and Competitiveness and FEDER (CTQ-2015-68654-R)

Methanol dehydration on carbon-based acid catalysts

Methanol dehydration to produce dimethyl ether (DME) is an interesting process for the chemical industry since DME is an important intermediate and a promising clean alternative fuel for diesel engines. Pure or modified γ-aluminas (γ-Al2O3) and zeolites are often used as catalysts for this reaction. However, these materials usually yield non desirable hydrocarbons and undergo fast deactivation. In this work, we study the catalytic conversion of methanol over an acid carbon catalyst obtained by chemical activation of olive stone with H3PO4. A significant amount of phosphorus remains over the catalyst surface after the activation process, mostly in form of C-O-PO3 and C-PO3 groups, which provide the carbon a relatively high surface acidity and oxidation resistance. Methanol decomposition on this catalyst yields selectivities to DME higher than 82% at 623K and methanol conversion of 34%, under the operating conditions studied. The activated carbon catalytic activity and stability, under inert and oxidant atmospheres, as well as different regeneration procedures, were studied. In the absence of oxygen, the catalyst suffers a progressive deactivation by coke deposition on the active acid sites (Fig. 1). The presence of oxygen modifies the carbon surface chemistry, probably through oxygen spillover on the catalyst surface, where the availability of labile oxygen avoids catalyst deactivation. A reaction mechanism has been proposed where methanol dehydration seems to proceed through an Eley-Rideal mechanism, which assumes the adsorption of water and oxygen spillover on the acid active sites, avoiding coke deposition

Oxidation of activated carbons containing surface phosphorus functionalities

Activated carbons materials have attracted considerable attention because of their interesting application in many fields, such as catalysis, gas and liquid phase adsorption and gas and energy storage. However, the use of carbon materials in catalysis is limited since they would gasify to CO2 (or CO) in the presence of oxygen at relatively low temperatures. On the other hand, it has been shown that it is possible to prepare carbon materials with a relatively large amount of phosphorus on the carbon surface by chemical activation of lignocellulosic materials with phosphoric acid [1]. This activation method leads, in certain operation conditions, to the generation of phosphorus surface complexes in form of C-O-PO3, C-PO3 and C3PO groups, which present a very high thermal stability and confer to the carbons certain surface properties of great interest in heterogeneous catalysis applications, such as high oxidation resistance and surface acidity. The main purpose of the present work is to study the role of the phosphorus surface groups of these activated carbons on the carbon surface oxidation and reduction reactions. An extensive study of the oxidation evolution of the activated carbon surface has been carried out by subjecting the carbon to thermal treatments in oxidizing and inert conditions, using different techniques including temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) for the characterization of the obtained carbons. It has been proved that phosphorus surface groups preferentially trap oxygen and are transformed from less to moreoxidized species prior to carbon gasification, even at low temperature. These experimental results evidence the role of phosphorus surface groups on the inhibition of carbon oxidation and gasification. The high capacity of these phosphorus species to be oxidized results in activated carbons with a high amount of oxygen surface groups of acidic character and relatively high thermal stability. The reduction and re-oxidation of the (phosphorus) surface groups have also been proved to be reversible through successive thermal treatments in oxidizing and inert conditions. The new surface sites generated during the reduction conditions (probably of C-PO type) may react with oxygen from air and regenerate the C–O–PO system, indicating the presence of redox sites on the surface of the activated carbon. These results open new and attractive possibilities for the use of these carbon materials as catalytic supports or as catalysts by themselves for reactions that take place under oxidizing conditions and at relatively high temperatures.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Actores económicos y desarrollo local en destinos norpatagónicos

El presente artículo es producto de un trabajo de investigación en las localidades de Aluminé y Villa Pehuenia, Provincia del Neuquén, República Argentina. Este trabajo aborda el desarrollo local y su vinculación con la actividad turística en la localidad de Aluminé. El turismo es relativamente reciente en este territorio. Se indaga sobre las características de los actores locales económicos, así como el involucramiento en políticas innovadoras relacionadas con el turismo y su rol en el proceso de producción del turismo. Se distinguen la heterogeneidad en los servicios específicos como en aquellas actividades primarias, secundarias y terciarias cuyos productos se comercializan en el sistema turístico, que da lugar a la presencia de distintos mercados en un mismo ámbito. Finalmente, desde una perspectiva de desarrollo local, se reconocen algunas experiencias de competitividad y complementariedad, como también dificultades y beneficios, para la concreción de políticas locales de coordinación interinstitucional para un desarrollo local turístico.This article is the result of a research project in the towns of Aluminè and Villa Pehuenia, Neuquén Province. This paper addresses local development and its relationship to tourism, which is relatively new in this area. It explores the characteristics of local economic actors, as well as involvement in innovative policies related to tourism and its role in the production process of tourism. We distinguish heterogeneity in specific services in those activities primary, secondary and tertiary whose products are marketed in the tourism system and depend largely on the situation in the activity. Finally, from the perspective of local development, will recognize some experiences competitiveness and complementarity, as well as difficulties and benefits realization of local coordination policies in local development towards a tourist.Fil: Bosch, Jose Luis. Universidad Nacional del Comahue. Facultad de Turismo; ArgentinaFil: Suárez, Silvana Reneé. Universidad Nacional del Comahue. Facultad de Turismo; ArgentinaFil: Rodriguez, María Daniela. Universidad Nacional del Comahue. Facultad de Turismo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin