Advanced Reaction Systems for Hydrogen Production

[EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named ���Formaci��n de Personal Investigador��� at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut f��r Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks ���renewable and non-renewable, gases and liquids��� through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using ��-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30���60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1���3 ��m) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625��C and 725��C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on ��-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using ��-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.

El��ments nutritifs et production primaire dans les lagunes du C��te d'Ivoire : cycle annuel

This paper collects most of the information gathered between October 1974 and July 1976 within the framework of a research program concerning the hydrobioclimate of ivorian lagoons and especially the Ebri�� lagoon. Monthly surveys concerning the latter were carried out during 1975. The following parameters - and their vertical distribution wherever it had a meaning - were systematically gathered in a system of fifty-five stations: Transparency (Secchi), Temperature, Salinity, Chlorophylla, Dissolved oxygen, phosphate, nitrate, nitrite. These data provide an outline of the annual cycle of nutrients and primary production of the Ivoirian lagoons

White spot syndrome virus (WSSV) transmission risk through infected cooked shrimp products assessed by polymerase chain reaction (PCR) and bio-inoculation studies

The aim of the study was to evaluate the resistance of white spot syndrome virus (WSSV) in shrimps (Penaeus monodon) to the process of cooking. The cooking was carried out at 1000C six different durations 5, 10, 15, 20, 25 and 30 min. The presence of WSSV was tested by single step and nested polymerase chain reaction (PCR). In the single step PCR, the primers 1s5 & 1a16 and IK1 & IK2 were used. While in the nested PCR, primers IK1 &IK2 ��� IK3 & IK4 were used for the detection of WSSV. WSSV was detected in the single step PCR with the primers 1s5 and 1a16 and the nested PCR with the primers IK1 and IK2 ��� IK3 & IK4 from the cooked shrimp samples. The cooked shrimps, which gave positive results for WSSV by PCR, were further confirmed for the viability of WSSV by conducting the bio-inoculation studies. Mortality (100%) was observed within 123 h of intra-muscular post injection (P.I) into the live healthy WSSV-free shrimps (P. monodon). These results show that the WSSV survive the cooking process and even infected cooked shrimp products may pose a transmission risk for WSSV to the native shrimp farming systems.

Cycle sexuel et f��condit�� du machoiron Chrysichthys nigrodigitatus en Lagune Ebri��, C��te d'Ivoire

Changes in the seasonal development of the gonads of female Chrysichthys nigrodigitatus, in Ebri�� lagoon (C��te d'Ivoire) are described over an annual reproductive cycle. Seven macroscopic stages of gonad maturity were identified. There is a major spawning period from July to November. The mature fish spawn only once during the breeding season. There was a slightly higher correlation between fecundity and fish length than between fecundity and fish weight or gonad weight. Fecundity estimates ranged from 5438 to 36257 eggs and from 4878 to 87724 eggs, respectively for the fish in captivity and those in the natural environment.

Hiperagregabilidade plaquet��ria e depress��o: �� o ��xido n��trico o mensageiro comum?

A depress��o �� uma doen��a grave que vem se tornando mais prevalente na popula����o mundial e no Brasil. Segundo a Organiza����o Mundial de Sa��de (OMS), �� a quarta doen��a mais incapacitante e estima-se que em 2020 ocupe o segundo lugar, ficando atr��s apenas das doen��as cardiovasculares (DCV), que s��o a principal causa de morte no mundo. O Transtorno depressivo maior (TDM) se caracteriza por humor deprimido, tristeza intensa ou des��nimo ou perda de interesse ou de prazer por quase todas as atividades por, pelo menos, duas semanas. Al��m disso, tem um elevado ��ndice de mortalidade cardiovascular, e esta associa����o parece ser multifatorial e altamente complexa, e ainda n��o est�� completamente elucidada. Recentes estudos sugerem que a ocorr��ncia de aterotrombose e eventos cardiovasculares no TDM est�� associada a uma diminui����o na biodisponibilidade do ��xido n��trico (NO), um potente vasodilatador, anti-agregante plaquet��rio e neurotransmissor. O NO �� um g��s formado a partir da L-arginina, pela a����o da fam��lia de enzimas NO sintases (NOS), e vai ocasionar um aumento de guanosina monofosfato c��clica (GMPc), que �� posteriormente degradada pelas fosfodiesterases (PDE). A L-arginina participa em outras vias al��m da produ����o de NO, como a arginase. O estresse oxidativo tamb��m tem uma participa����o no desenvolvimento dos transtornos psiqui��tricos e nas DCV, e pode reduzir a meia-vida do NO. O objetivo deste estudo �� investigar a via NO-GMPc, o ciclo da ur��ia, marcadores de estresse oxidativo e de inflama����o em plaquetas e a sua associa����o com a fun����o plaquet��ria no TDM. Participaram da pesquisa nove pacientes com diagn��stico de depress��o leve a moderada do Servi��o de Psicologia Aplicada (SPA/UERJ) e onze indiv��duos saud��veis pareados por idade como controles. Este projeto foi aprovado pelo Comit�� de ��tica e Pesquisa do Hospital Universit��rio Pedro Ernesto (1436-CEP/HUPE). A agrega����o plaquet��ria, a express��o e atividade da arginase II, a express��o da PDE 5, marcadores de estresse oxidativo (n��veis de TBARS, carbonila����o de prote��nas, express��o da NADPH oxidase e da glutationa peroxidase (GPx) e atividade desta e da catalase (CAT), ambas enzimas anti-oxidantes) nas plaquetas e no soro, e o fibrinog��nio sist��mico foram investigados. No presente estudo observou-se um aumento da agrega����o plaquet��ria induzida por ADP em pacientes com TDM comparados aos controles. Uma ativa����o da arginase II em plaquetas sem qualquer altera����o na sua express��o foi demonstrada em pacientes com TDM. Al��m disso, um aumento na carbonila����o de prote��nas e na express��o de GPx, de NADPH e de PDE5 foi observado em plaquetas de pacientes com TDM. A produ����o de TBARS, a atividade de GPx e CAT nas plaquetas e no soro n��o foram afetados pelo TDM. N��o houve diferen��a nos n��veis de fibrinog��nio entre pacientes com TDM e controles. A ativa����o da arginase, somada ao estresse oxidativo, reduziria a biodisponibilidade de NO levando �� disfun����o plaquet��ria nos pacientes com TDM. O presente estudo acrescenta dados importantes para a compreens��o dos mecanismos celulares envolvidos na rela����o TDM e DCV. Al��m disso, abre caminho para a utiliza����o de novas ferramentas farmacol��gicas, como os antioxidantes, para o tratamento do TDM.

��tude histologique du cycle sexuel de l'albacore (Thunnus albacares) Bonnaterre 1788

The evolution of the general microscopic structure of the ovary of Thunnus albacares related to the gonad index, and the ovocyte maturation process were studied. Some stages of the males sexual maturation were characterized.

A via L-arginina��xido n��trico, estresse oxidativo e ciclo da ur��ia na obesidade

A obesidade �� um dist��rbio metab��lico de etiologia multifatorial e elevada preval��ncia no Brasil, que pode ser definida por um ��ndice de massa corporal (peso em quilogramas dividido pela altura em metros ao quadrado) maior ou igual a 30 kg/m2, e que est�� associada de forma independente a um elevado risco de morbidade e mortalidade cardiovascular devido aos eventos aterotromb��ticos. O ��xido n��trico (NO), uma pequena mol��cula gasosa, �� produzido atrav��s da convers��o do amino��cido cati��nico L-arginina em L-citrulina e NO em uma rea����o catalisada por uma fam��lia de enzimas denominadas NO-sintases (NOS), e funciona como um protetor cardiovascular modulando por exemplo o relaxamento do m��sculo liso vascular e a fun����o plaquet��ria. O objetivo desta tese foi avaliar a via L-arginina-NO, bem como investigar a fun����o plaquet��ria, o estresse oxidativo, e a atividade da arginase em pacientes com obesidade. O transporte de L-arginina, a produ����o de guanosina monofosfato c��clica (GMPc), a atividade e a express��o das isoformas da NOS (iNOS e eNOS), a atividade da arginase, o estresse oxidativo (produ����o de esp��cies reativas de oxig��nio EROs; atividade da super��xido dismutase SOD; e atividade da catalase), bem como a fun����o plaquet��ria foram medidos nas plaquetas dos pacientes com obesidade. Nas hem��cias, foram medidos o transporte de L-arginina e a atividade da NOS e da arginase. Os n��veis de amino��cidos e de marcadores inflamat��rios (fibrinog��nio e prote��na C reativa) tamb��m foram medidos sistemicamente. Os resultados demonstram que o influxo de L-arginina via sistema y+L, a atividade da NOS e a produ����o de GMPc est��o diminu��dos nas plaquetas dos pacientes obesos em rela����o aos controles saud��veis, enquanto que n��o houve diferen��a na atividade da arginase. Al��m disso, a express��o das isoformas da NOS bem como a agrega����o plaquet��ria em plaquetas de pacientes com obesidade mostrou-se aumentada em rela����o aos controles. Nas hem��cias destes pacientes, observou-se elevado influxo de L-arginina via sistema y+ e y+L e atividade da NOS, e nenhuma diferen��a na fun����o da arginase. A concentra����o plasm��tica de L-arginina n��o foi afetada pela obesidade, mas j�� os marcadores inflamat��rios estavam significativamente aumentados. A produ����o de EROs e a atividade da catalase nas plaquetas n��o estava alterada em pacientes com obesidade, enquanto que a atividade da SOD mostrou-se diminuida. Assim, apesar do aumento da produ����o de NO pelas hem��cias, �� poss��vel que a baixa produ����o plaquet��ria de NO, al��m do estado inflamat��rio e um poss��vel estresse oxidativo, estejam contribuindo para a elevada atividade plaquet��ria observada na obesidade. As descobertas aqui apresentadas contribuem para uma melhor compreens��o dos eventos cardiovasculares presentes na obesidade.

Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (Cnidoglanis macrocephalus) after heavy fishing

The hypothesis that heavy fishing pressure has led to changes in the biological characteristics of the estuary cobbler (Cnidoglanis macrocephalus) was tested in a large seasonally open estuary in southwestern Australia, where this species completes its life cycle and is the most valuable commercial fish species. Comparisons were made between seasonal data collected for this plotosid (eeltail catfish) in Wilson Inlet during 2005���08 and those recorded with the same fishery-independent sampling regime during 1987���89. These comparisons show that the proportions of larger and older individuals and the catch rates in the more recent period were far lower, i.e., they constituted reductions of 40% for fish ���430 mm total length, 62% for fish ���4 years of age, and 80% for catch rate. In addition, total mortality and fishing-induced mortality estimates increased by factors of ~2 and 2.5, respectively. The indications that the abundance and proportion of older C. macrocephalus declined between the two periods are consistent with the perception of long-term commercial fishermen and their shift toward using a smaller maximum gill net mesh to target this species. The sustained heavy fishing pressure on C. macrocephalus between 1987���89 and 2005���08 was accompanied by a marked reduction in length and age at maturity of this species. The shift in probabilistic maturation reaction norms toward smaller fish in 2005���08 and the lack of a conspicuous change in growth between the two periods indicate that the maturity changes were related to fishery-induced evolution rather than to compensatory responses to reduced fish densities.

Regional variation in the annual feeding cycle of juvenile walleye pollock (Theragra chalcogramma) in the western Gulf of Alaska

Juvenile fish in temperate coastal oceans exhibit an annual cycle of feeding, and within this cycle, poor wintertime feeding can reduce body growth, condition, and perhaps survival, especially in food-poor areas. We examined the stomach contents of juvenile walleye pollock (Theragra chalcogramma) to explain previously observed seasonal and regional variation in juvenile body condition. Juvenile walleye pollock (1732 fish, 37���250 mm standard length) of the 2000 year class were collected from three regions in the Gulf of Alaska (Kodiak, Semidi, and Shumagin) representing an area of the continental shelf of ca. 100,000 km2 during four seasons (August 2000 to September 2001). Mean stomach content weight (SCW, 0.72% somatic body weight) decreased with fish body length except from winter to summer 2001. Euphausiids composed 61% of SCW and were the main determinant of seasonal change in the diets of fish in the Kodiak and Semidi regions. Before and during winter, SCW and the euphausiid dietary component were highest in the Kodiak region. Bioenergetics modeling indicated a relatively high growth rate for Kodiak juveniles during winter (0.33 mm standard length/d). After winter, Shumagin juveniles had relatively high SCW and, unlike the Kodiak and Semidi juveniles, exhibited no reduction in the euphausiid dietary component. These patterns explain previous seasonal and regional differences in body condition. We hypothesize that high-quality feeding locations (and perhaps nursery areas) shift seasonally in response to the availability of euphausiid