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This paper describes the parallelization process of the code PROMES. The parallel code, called PROMESPAR, has been carried out under a distributed platform (cluster of PCs) and using Message Passing Interface (MPI) communication subroutines.

Propene adsorption isotherms, breakthrough curves and temperature programme desorption profiles have been obtained for six different crystalline materials with distinctive framework structures (3D and 1D) and a variety of Si/Al ratios and cations (four zeolites: Silicalite-1, BETA, ZSM-5, Mordenite; and two silicoaluminophosphate molecular sieves: SAPO-41 and SAPO-5). Moreover, for a proper evaluation of the solids in a propene trap under cold start conditions, cold start tests have been performed, carrying out four cycles (adsorption/desorption) to analyze the ageing process of the materials. A detailed analysis of the experimental results points out that materials with high equilibrium propene adsorption capacity at 30 °C, where propene is mainly chemisorbed and, which presents some kinetics restrictions, seem to be the best for a propene trap under cold start conditions. BETA and ZSM-5 zeolites and SAPO-5 silicoaluminophosphate molecular sieve are promising materials as propene traps., The authors would like to thank Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project 331/PC08/3-13.1) and Generalitat Valenciana (PROMETEO/2009/047) for financial support.

High vacuum temperature programmed desorption (HVTPD) experiments after CO2 treatment on bulk CaO and calcium-carbon samples have been performed in order to obtain information about the working mechanism of calcium as a catalyst in the CO2 gasification of carbon. The main characteristics of these HVTPD spectra are two well-defined CO2 peaks (at ≈ 675K and ≈ 800 K.) and two CO peaks (at ≈ 850 and ≈ 1125 K) of similar size, independent of the calcium content. The HVTPD experiments are interpreted on the basis of the reversibility of the bulk CaCO3 decomposition reaction and the different kinetic behaviour of the steps involved in the mechanism of carbon gasification catalyzed by calcium. TPD experiments carried out under high vacuum conditions allow the two steps corresponding to the catalysis of carbon gasification by calcium to be differentiated, under conditions in which no secondary reactions occur.

In a previous study, we investigated, at a laboratory scale, the chemical activation of two different carbon fibres (CF), their porosity characterization, and their optimization for hydrogen storage [1]. In the present work, this study is extended to: (i) a larger range of KOH activated carbon fibres, (ii) a larger range of hydrogen adsorption measurements at different temperatures and pressures (i.e. at room temperature, up to 20 MPa, and at 77 K, up to 4 MPa), and (iii) a scaling-up activation approach in which the obtained activated carbon fibres (ACF) are compared with those from laboratory-scale activation. The prepared samples cover a large range of porosities, which is found to govern their ability for hydrogen adsorption. The hydrogen uptake capacities of all the prepared samples have been analysed both in volumetric and in gravimetric bases. Thus, maximum adsorption capacities of around 5 wt% are obtained at 77 K, and 1.1 wt% at room temperature, respectively. The packing densities of the materials have been measured, turning out to play an important role in order to estimate the total storage capacity of a tank volume. Maximum values of 17.4 g/l at 298 K, and 38.6 g/l at 77 K were obtained. Osaka Gas Co., Ltd. supplied the two precursor materials. Financial help was received from the European Union (Marie Curie Research Training Network-HyTRAIN-Project reference: 512443), MEC (ENE2005-23824-E/CON), the Generalitat Valenciana (ACOMP06/089 and PROMETEO/2009/047), as well as MEC-CTQ2006-08958/PPQ.

An overview of the type of information obtained by X-ray microdiffraction and micro small-angle X-ray scattering (\(\mu\)SAXS) measurements on carbon fibres and activated carbon fibres is presented. It is shown that the use of X-ray microbeams is a unique way to know about the internal organisation of both pores and nanocrystallites in single carbon fibres. Moreover, combination of these techniques with stretching experiments allowed us to learn how the application of a mechanical load affects carbon fibres from the length scales of atomic structure to the microporosity. In addition, it is seen that accessible and non-accessible porosity can be distinguished by contrast-matching \(\mu\)SAXS experiments and that the development of isotropic and anisotropic microporosity across the fibre diameter during the activation process can be studied by \(\mu\)SAXS technique.

Results show that it is possible to activate a low softening point isotropic petroleum pitch, without intermediate pre-treatments, by chemical activation with KOH. The chemical activation is carried out by direct heat treatment of a mixture of the isotropic pitch and KOH. It produces activated carbons (ACs) with micropore volumes as high as 1.12 cm3/g, and BET surface areas around 3000 m2/g. The activating agent/precursor ratios studied (from 1/1 to 4/1; wt./wt.) show, as expected, that increasing the ratio enhances the adsorption characteristics of the resulting AC. MEC (Project CTQ2006-08958/PPQ) and Generalitat Valenciana (ARVIV/2007/063).

A new procedure to quantify the catalytic active sites (CAS) in calcium-catalyzed carbon gasification is presented. The method is based on TPD analysis after CO 2 chemisorption. The second CO 2 composite peak is related to the calcium-carbon contact and the quantification of this peak provides a measure of the CAS. Turnover frequencies based on this CAS for CO 2 and steam gasification are found constant for different calcium loading and for samples with different sintering degrees

It is widely recognized that the dispersion (presumably related to the degree of catalyst-carbon contact) of a solid catalyst in a carbonaceous matrix plays an important role in explaining its catalytic activity in gasification reactions. CaO-CO{sub 2} interactions have been studied by thermogravimetry-differential thermal analysis (TG-DTA), temperature-programmed desorption (TPD), and temperature-programmed reaction (TPR). A less classical technique termed intermittent temperature-programmed desorption (ITPD) has also been used. A mass spectrometer has been employed as a gas flow analyzer in all the temperature-programmed techniques. The temperature at which CO{sub 2}-CaO interactions take place determines whether their nature is limited to CO{sub 2} chemisorption or involves bulk carbonate formation in CaO particles as well. While only chemisorption occurs at temperatures between 323 and 573 K, bulk carbonate formation is observed at higher temperatures; the higher the temperature, the deeper the carbonate formation of CaO particles. CO{sub 2} chemisorption is interpreted by applying models commonly used for heterogeneous surfaces, with variations in the heat of adsorption and in the desorption activation energy as functions of coverage. The interpretation of the thermodynamics and kinetics of the process in the temperature range 323-1,173 K led to the proposal of a mechanism for the first steps ofmore » the reaction of CO{sub 2} with CaO particles.« less

Various “in situ” techniques, including thermogravimetry (TG), differential thermal analysis (DTA), isothermal chemisorption, temperature-programmed desorption (TPD), intermittent TPD, temperature programmed reaction (TPR) and BET surface area determination, have been used to characterize calcium as a catalyst of carbon gasification. These techniques were first established with pure CaO samples and then applied to the CaO-carbon system. These methods, and particularly TPD accompanied by internal sample gasification, proved to be an efficient means of getting new insights into the calcium-catalyzed carbon gasification.

Interpretation of the catalytic activity of calcium and its deactivation in the CO2 carbon gasification reaction has been deduced from temperature programmed desorption (TPD) with quadrupole mass spectrometer (MS) experiments after CO2 treatment. The main characteristics of these TPD spectra are two well-defined CO2 peaks (at ≈953 K and ≈1,053 K) together with a CO peak (at ≈1,053 K). TPD spectra from three sets of experiments have been analyzed and interpreted. The following variables were investigated: (1) effect of wt% calcium loading, (2) effect of catalyst sintering, and (3) effect of the CO2 treatment temperature. The lower temperature CO2 peak has been associated with the external surface of CaO without any contact with the carbon, therefore it corresponds to the inactive catalyst. The higher temperature CO2 peak together with the “net” CO peak has been associated with the CaO-carbon interface which is responsible for the catalytic activity. A novel model is proposed for CO2 chemisorption on CaO particles supported in carbon and its subsequent redistribution during TPD. The model is used to interpret TPD spectra.

In this work we focus on secure routing protocols in wireless sensor networks. Routing is a fundamental task in sensor networks and, consequently, attacks on the routing functionality can have a serious impact in the network performance. In order to deal with this problem we propose the application of an existing modelling framework for secure routing protocols which reflects the node capabilities. This framework describes an adversary model adapted to the capabilities of the sensor network. Our proposal is based on timed automata and the UPPAAL tool.

Special issue: 2nd World Congress of Young Scientists on Hydrogen Energy Systems. Porous materials are gaining interest due to their potential for storing hydrogen via physisorption. In the present work, two carbon fibres, carbonised at 973 and 1273 K, have been chemically activated with KOH and NaOH, in order to obtain materials with optimised characteristics for hydrogen storage application. Highly microporous activated carbon fibres were obtained from both precursors, especially from the fibre carbonised at the lower carbonisation temperature, remarking its importance on its subsequent activation process. As activation agent, KOH is more effective for developing the narrow microporosity, and higher yields are obtained. H2 adsorption isotherms were measured at 298 K for pressures up to 20 MPa, and at 77 K up to 4 MPa. The maximum excess adsorption of hydrogen reached 1 wt% at 298 K and 3.8 wt% at 77 K. The total volumetric storage capacity is of 17 g/l at 298 K, and 32 g/l at 77 K. Financial help from the European Union (Marie Curie Research Training Network—HyTRAIN Project reference:512443), MEC (Accion complementaria; ENE2005-23824-E/CON), the Generalitat Valenciana (Accion complementaria; ACOMP06/089) and MEC-CTQ2006-08958PPQ. Samples supplied by Osaka gas Co., Ltd.

Activated carbon fibers (ACFs) are porous carbons with a fiber shape and a well-defined porous structure that can be prepared with a high adsorption capacity. Although the ACFs are very promising materials, they have not still a market as important as the activated carbons (ACs) due to their difference in production costs. The main characteristics and advantages of the ACFs are as follows 1. ; 2. ; 3. .

Activated carbon fibres (ACFs) have been successfully prepared with a remarkable development of porosity from four isotropic coal tar pitches and four isotropic petroleum pitches. Special care has been put to make the activation process at similar activation rate in order to have a better comparison of the different precursors used. The micropore volumes of petroleum pitches-derived ACFs are higher than those obtained from coal tar pitches under similar activation yields. The resultant ACFs present interesting textural properties: they are essentially microporous materials, with a high adsorption capacity which increases linearly with the burn-off. It has been observed, independently of the pitch precursor used, that the micropore volume is a function of the degree of activation, being, in all the cases, quite similar for a given activation degree if a comprehensive weight loss is considered (carbonization lost and degree of activation). MEC and FEDER (CTQ2006-08958) and GV (GV/2007/144 and ARVIV/2007/063).

The purpose of this study was to characterize the calcium (nature, amount of various species and state of division) in carbonaceous materials such as low-rank coal char or a model char (obtained by pyrolysis of a polymeric resin at 1273 K under an inert gas). Ca loading (

A detailed study about the synthesis, characterization and properties of poly(o-methylaniline)(PoMea)/maghnite nanocomposites has been performed. Changes in the characteristics of the nanocomposites, depending on the intercalated cation between the clay layers before the synthesis, have been observed. Intercalated morphology has been detected by TEM in nanocomposites containing copper-treated maghnite (Magh-Cu), while when maghnite treated with strong acids was used (Magh-H); an exfoliated material has been obtained. Also, remarkable differences in the properties of the polymers have been observed by TG-MS and FTIR, suggesting that the polymer produced with Magh-H has a higher degree of branching. The electrochemical behavior of the polymers extracted from the nanocomposites has been studied by cyclic voltammetry. Good electrochemical response has been observed for PoMea grown into Magh-Cu but not for the one polymerized into Magh-H. Ministerio de Educación y Ciencia (MAT2007- 60621 Project); Generalitat Valenciana (RED ARVIV2007/076); Algerian CNEPRU and FNR.

In this paper, a formal analysis of security protocols in the field of wireless sensor networks is presented. Two complementary protocols, TinySec and LEAP, are modelled using the high-level formal language HLPSL, and verified using the model checking tool Avispa, where two main security properties are checked: authenticity and confidentiality of messages. As a result of this analysis, two attacks have been found: a man-in-the-middle- attack and a type flaw attack. In both cases confidentiality is compromised and an intruder may obtain confidential data from a node in the network. Two solutions to these attacks are proposed in the paper.

In this work, we present experimental results corresponding to H2 adsorption at high pressures and different temperatures (77 and 298 K) for a wide variety of carbons materials in order to analyze the effect of the porosity on the H2 adsorption capacities in gravimetric basis. Likewise, we point out the importance of the packing density of the materials in order to obtain high H2 adsorption capacities in volumetric basis and high total storage capacities. At 298 K, the H2 adsorption capacity depends on both the total micropore volume and the micropore size distribution. At 77 K, H2 adsorption depends only on the total micropore volume of the carbon material. Packing density of the carbon materials decreases with increasing the porosity deve- lopment. Therefore, a good balance between porosity and packing density is needed. The total H2 storage on the best activated carbon at 298 K and 20 MPa is 16.7 g H2/L and 38.8 g H2/L at 77 K and 4 MPa.

In this paper, a formal analysis of a security protocol in the field of wireless sensor networks is presented. Sensor network encryption protocol (SNEP) describes basic primitives for providing confidentiality, authentication between two nodes, data integrity and weak message freshness in a wireless sensor network. It was designed as base component of security protocols for sensor networks (SPINS). SNEP is modelled in two scenarios using the high-level formal language HLPSL, and verified using the model checking tool Avispa, where two main security properties are checked: authenticity and confidentiality of relevant messages components. The first case is the communication between the base station and networks nodes in order to retrieve node confidential information. The second case is a key distribution protocol in a sensor network using SNEP for securing messages. As a result of this analysis, one attack have been found: a false request message from an intruder. In that case, the intruder impersonates the base station and creates false requests. This way, the intruder may obtain confidential data from a node in the network. A solution to this attack is proposed in the paper.

11 pages, 10 figures, 1 table.-- Available online on Nov 1, 2006., Hydrogen adsorption measurements have been carried out at different temperatures (298 K and 77 K) and high pressure on a series of chemically activated carbons with a wide range of porosities and also on other types of carbon materials, such as activated carbon fibers, carbon nanotubes and carbon nanofibers. This paper provides a useful interpretation of hydrogen adsorption data according to the porosity of the materials and to the adsorption conditions, using the fundamentals of adsorption. At 298 K, the hydrogen adsorption capacity depends on both the micropore volume and the micropore size distribution. Values of hydrogen adsorption capacities at 298 K of 1.2 wt.% and 2.7 wt.% have been obtained at 20 MPa and 50 MPa, respectively, for a chemically activated carbon. At 77 K, hydrogen adsorption depends on the surface area and the total micropore volume of the activated carbon. Hydrogen adsorption capacity of 5.6 wt.% at 4 MPa and 77 K have been reached by a chemically activated carbon. The total hydrogen storage on the best activated carbon at 298 K is 16.7 g H2/l and 37.2 g H2/l at 20 MPa and 50 MPa, respectively (which correspond to 3.2 wt.% and 6.8 wt.%, excluding the tank weight) and 38.8 g H2/l at 77 K and 4 MPa (8 wt.% excluding the tank weight)., Authors thank financial support from MCYT (Project PPQ2003-03884), Generalitat Valenciana (Project GV04A-608) and EU (HyTRAIN MC RTN-512443). F. Suárez-García thanks MCYT for his contract “Juan de la Cierva” and M. Jorda-Beneyto thanks MEC for her Ph.D. fellowship. Authors also thank Dr. F. Lamari-Darkrim for the measurement of hydrogen isotherm on sample KUA5 up to 50 MPa.

The stabilisation of pitch fibres (PFs) is the most important step for their subsequent use in the preparation of carbon fibres (CFs) and their resulting characteristics. The present work studies the influence that the stabilisation time has on the porosity of the CFs, and on the subsequent properties as carbon molecular sieve (CMS). The increase of the stabilisation time carried out at 573 K, from 2 to 8 h favours their CMS properties producing a decrease in the microposity accessible to N2, which gets completely blocked after 6 and 8 h, while the narrow microporosity (V-DR CO2) remains accessible. Adsorption kinetic studies with CH4 and CO2 were performed to assess the possibility of using these CFs as CMS by comparing them with Takeda 3A CMS. The results suggest that there is an optimal stabilisation time which allows the preparation of CFs from an abundant raw precursor with properties similar to Takeda 3A CMS. MCYT (PPQ2003-03884).

Web services secure conversation extends Web services trust to provide mechanisms for establishing security contexts. A security context is an abstract concept that refers an authenticated state where the participants have derived secure session keys for multiples request/response exchanges. In this paper we model this protocol with the HLPSL language and we analyse it with the AVISPA toolbox.

Nowadays, the success of the manufacturing industry is largely determined by its ability to respond to the rapidly changing market and customer needs. This has resulted in an increasing deployment of automated manufacturing equipment and systems that provide the agility to cope with these new demands. Flexible Manufacturing Systems (FMS) are the most widely used technology to cover these needs. Of course, these FMS must be studied in a formal frame, but the complexity and the dimension of real FMS has prevented from developing efficient control techniques and several challenges are still left. We face up these challenges and present a language that is able to specify nearly any type of real FMS. We use a timed process algebra called BTC (for Bounded True Concurrency) that we have developed from CSP and which takes into account that the available resources in a system have to be shared by all the processes. It is able to consider heterogeneous resources of any type (preemptable and non-preemptable) which makes it suitable for specifying FMS. We show by means of an example that the specifications obtained suit the real systems quite well and are straightforward. To the best of our knowledge, this is the first attempt to do this with process algebras, and we think that it is a good way, mainly, because we are able to split up the system into subsystems which will be easier analyzed.

Chemical and electrochemical techniques have been used in order to asses surface functionalities of porous carbon materials. An anthracite has been chemically activated using both KOH and NaOH as activating agents. As a result, activated carbons with high micropore volume (higher than 1 cm3/g) have been obtained. These samples were oxidized with HNO3 and thermally treated in N2 flow at different temperatures in order to obtain porous carbon materials with different amounts of surface oxygen complexes. Thermal treatment in H2 was also carried out. The sample treated with H2 was subsequently treated in air flow at 450 ºC. Thus, materials with very similar porous texture and widely different surface chemistry have been compared. The surface chemistry of the resulting materials was systematically characterized by TPD experiments and XPS measurements. Galvanostatic and voltammetric techniques were used to deepen into the characterization of the surface oxygen complexes. The combination of both, chemical and electrochemical methods provide unique information, regarding the key role of surface chemistry in improving carbon wettability in aqueous solution and the redox processes undergone by the surface oxygen groups. Both contributions are of relevance to understand the use of porous carbons as electrochemical capacitors. Ministerio de Ciencia y Tecnología (PPQ2003-03884).

A method using iodine has been developed for the stabilisation of low softening point (SP) pitch fibres that avoids air stabilisation in the production of carbon fibres (CF). The interaction between iodine and petroleum pitches has been studied by following the changes in the hydrogen content, aromatic or aliphatic, during the heat treatment of iodine-treated pitch fibres. Two low SP petroleum pitches were used and the iodine-treated pitch fibres were analysed by TGA, DSC, DRIFT, XPS and SEM. The results confirm that using this novel method pitches with low SP can be used to prepare CF with two advantages, compared with conventional methods. The stabilisation time is considerably reduced and treatments to increase the SP, usually required when low SP pitches are used to prepare CF, can be avoided. Spanish Government (project PPQ2003-03884).

This paper deals with the specification and analysis of Flexible Manufacturing Systems (FMS). We use a timed process algebra called BTC (for Bounded True Concurrency) that we have developed from CSP and which takes into account that the available resources in a system have to be shared by all the processes. It is able to consider heterogeneous resources of any type (preemptable and non- preemptable) which makes it suitable for specifying FMS. We show by means of an example that the specifications obtained suit the real systems quite well, are straightforward and deadlock-free. Due to the great interest (and need) in obtaining shorter manufacturing lead times, we also carry out a performance evaluation using an algorithm which allows us to estimate the time required to evolve between states. To the best of our knowledge, this is the first attempt to do this with process algebras, and we think that it is a good way to be able to split up the system into subsystems, which will be easily analyzed without the deadlock problems that researchers in Petri Nets have encountered.

In this paper we consider a timed process algebra based on classical LOTOS operators in order to specify the behaviour of concurrent systems and, concretely, those systems for which time becomes an important factor to take into account, such as real-time systems. One of the main goals of this paper is to define a translation into a kind of dynamic state graph, which is currently supported by a tool (TPAL), which allows it to simulate the execution of a specification by means of these dynamic state graphs.

This paper reports the formal specification and performance evaluation of a phase in the Secure Electronic Transaction (SET), an e-commerce protocol by Visa and MasterCard. We focus on the purchase phase which is modelled by means of a True Concurrency Timed Process Algebra (BTC), which takes into account the number of resources that the system has at its disposal. Here, we extend its syntax with the intention of representing what actions use the shared resources and how many resources the system has at its disposal. We then give a performance evaluation of this model where some interesting results are presented.

Web Services technologies have introduced a new challenge for security protocols. Traditional security protocols cannot handle intermediaries and the flexibility of Web Services bindings. Thus, several proposals for introducing security in Web Services have been presented. One of these is Web Services Security. In this paper we illustrate how this protocol works, with an example, and analyse whether it is a good option guaranteeing the security of Web Services.

A True Concurrency Timed Process Algebra which takes into account the number of resources/processors that processes have at disposal is presented. Both its syntax and its operational semantics are defined. An algorithm which allows us to estimate the required time to evolve between states and which allows us to evaluate the performance of a system is also presented. A simple example is used to illustrate how a system can be specified by means of our language and how the performance evaluation algorithm works.

The main goal of this paper is to extend sPBC with the iteration operator, providing an operational semantics for the language, as well as a denotational semantics, which is based on stochastic Petri nets. With this new operator we can model some repetitive behaviours, and then we obtain a formal method that can be easily used for the design of communication protocols and distributed systems.

We present an algebraic language for the description of probabilistic and non-deterministic processes, which allows us to evaluate performance indexes as well as to check some temporal requirements: ROSA (Reasoning On Stochastic Algebras). As an application, we analyse the Alternating Bit Protocol obtaining the average time to send a message, considering that channels may fail with a known probability.

Activated carbon fibre monoliths were prepared by physical activation of carbon fibre monoliths derived from two kinds of pitch-based carbon fibre (CF) (carbon fibres from a coal tar pitch and carbon fibres derived from a petroleum pitch). The monoliths were conformed using a coal tar pitch binder. The carbon fibre monoliths and the activated carbon fibre monoliths were studied by scanning electron microscopy (SEM) and gas adsorption (i.e. N2 at 77 K and CO2 at 273 K). The results obtained reveal that monoliths perform a good activation process that produce a quite high development of microporosity (BET surface areas around 2600 m2/g and N2 micropore volume of 1.23 cm3/g). On the other hand, it is remarkable that the activation process used allow to easily control the degree of activation and hence to select the adsorption capacities of the activated carbon fibre monoliths. EU (Project BRITE, BRPR97-4935).

Small angle X-ray scattering (SAXS) technique offers a number of advantages for the characterization of porous materials. At the microfocus beamline (ID13) in the “European Synchrotron Radiation Facility” (Grenoble) there are available X-ray microbeams with sizes down to 2 μm and a position-resolved scattering set-up (Microfocus Beamline, ID13). This experimental technique (μSAXS) has allowed to study single activated carbon fibers by Small angle X-ray scattering, instead of fiber bundles, and to analyze the porosity development across the fiber diameter. In addition, the use of an area detector (MAR-CCD) permits to obtain the two-dimensional scattering patterns, which have been used to detect anisotropic features related to the porosity development. In the present work, some examples corresponding to the first μSAXS experiments done with single activated carbon fibers (ACFs) are presented to show the usefulness of this technique.

This paper deals with the stabilisation of low softening point pitch fibres obtained from petroleum pitches using HNO3 as oxidising agent. This method presents some advantages compared with conventional methods: pitches with low softening point (SP) can be used to prepare carbon fibres (CF), the stabilisation time has been reduced, the CF yields are similar to those obtained after general methods of stabilisation, and the initial treatments to increase SP when low SP pitches are used to prepare CF, are avoided. The parent pitches were characterised by different techniques such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), elemental analysis and solvent extraction with toluene and quinoline. The interaction between HNO3 and the pitch fibres, as well as the changes occurring during the heat treatment, have been followed by DRIFTS. MCYT (Project MAT2000-0621 and PB98-0983).

Bimetallic PtSn/C catalysts, prepared on two activated carbon supports of different surface chemistry by two different preparation procedures, have been analyzed by XAFS spectroscopy. The main goal is to identify the effect of the support surface oxidation and the preparation procedure (coimpregnation or successive impregnations) in the interaction of platinum with the support and/or with tin atoms. XAFS results reveal the effect of the mentioned variables in the structure of the supported phase. It has been found in dried samples that the interaction of the platinum species with the support is stronger if the carbon surface is oxidized. The two-step impregnation, compared with the coimpregnation method, renders samples with a stronger platinum-support interaction. Such an interaction determines the distribution of the active phase on the support particles. The structure of the metallic phase after reduction is quite different for samples prepared with the oxidized and nonoxidized carbon support and is also dependent on the preparation procedure. From the XAFS data, the presence of the following platinum containing structures is suggested: PtSn alloy, Pt-O-Sn2+ species and pure Pt clusters. The relative proportion of these structures in the catalysts and their distribution on the support determine the catalytic activity for cyclohexane dehydrogenation. Fil: Román Martínez, M. C.. Universidad de Alicante; España Fil: Cazorla Amorós, Diego. Universidad de Alicante; España Fil: Yamashita, H.. University of Osaka Prefecture; Japón Fil: de Miguel, Sergio Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina Fil: Scelza, Osvaldo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentina

The use of Positron Annihilation Lifetime Spectroscopy (PALS) technique to characterize porous carbon materials has been analyzed. Positron annihilation lifetimes have been measured in two series of petroleum pitch-based activated carbon fibers (ACF) prepared by CO2 and steam activation. Two lifetime components were found: a short-lived component, σ1 from 375 to 393 ps and a long-lived component, σ2 from 1247 to 1898 ps. The results have been compared to those obtained by Small Angle X-Ray scattering (SAXS) and N2 and CO2 adsorption at 77K and 273K respectively. The correlation found demonstrates the usefulness of PALS to get complementary information on the porous structure of microporous carbons.

Small-Angle X-Ray Scattering (SAXS) studies have been carried out over a wide range of Q-values (5 x 10 −3 -0.5 A −1 ) permitting analysis of structural features for a spatial regime of 0.5-200 nm. Experimental and analysis procedures are described and results presented for a series of activated carbons. It is found that the pore size distribution has a complex form that varies according to the degree of activation (burn-off). Additional measurements have been made by neutron diffraction. The results demonstrate the basic graphitic structure of the carbons but show that there is considerable distortion of lattice planes.

This paper is a summary of the work undertaken on fundamental aspects of the calcium catalyzed carbon gasification. The purpose is to obtain an an insight into the mechanism of the calcium catalyzed carbon gasification, by understanding the activity of calcium as a function of the calcium content and the preparation method. A pure polymer carbon with a well developed porosity has been used. Calcium has been ion-exchanged and, also, loaded by impregnation to cover a wide range of calcium loadings. Simultaneous TG-DTA system and MS have been used to carry out the reactivity, chemisorption and TPD experiments. Reactivities in CO2 and steam show an increase with calcium loading up to a “loading saturation level” (LSL). A set of TPD experiments have been performed to explain this LSL and to obtain information about Ca-carbon contact. TPD experiments after CO2 treatment on CaO and CaO-carbon samples have been performed. The following variables have been investigated: 1) calcium loading, 2)calcium sintering and 3) CO2 treatment temperature. These results allow to propose an approach to the mechanism of the CO2-carbon gasification catalyzed by calcium, by considering the catalyst as a transport medium of CO2 to the Ca-carbon interface.

Activated carbon/polyaniline composites have been prepared using different electrochemical methods: single-step potentiostatic polymerization, multiple-step potentiostatic polymerization, and potentiodynamic polymerization with the anodic potential limits being fixed at either 0.75 or 1 V (vs Ag/AgCl). The prepared composite samples were characterized by cyclic voltammetry, galvanostatic charge-discharge tests, electrochemical impedance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The synthesis conditions were found to strongly affect the electrochemical behavior of the samples. High capacitance was achieved by the potentiostatic polymerization methods. As a general trend, higher capacitance and lower resistance were observed in the composites than the sum of these parameters of the individual components. This benefit is attributed to the enhanced electron delocalization along the polymer chains in the composites resulting from the influence of the activated carbon, as evidenced by the FTIR. However, an influence of the polyaniline morphology induced by the porous carbon cannot be discarded. MEC (project no. CTQ2006-08958/PPQ and no. MAT2007-60621) and Generalitat Valenciana-Feder (FTIR Microscopy equipment).