Effects of PEMFC operating parameters on the performance of an integrated ethanol processor

In this paper the performance of a complete fuel cell system processing ethanol fuel has been analyzed as a function of the main fuel cell operating parameters. The fuel processor is based on the steam reforming process, followed by high- and low-temperature shift reactors, and carbon monoxide preferential oxidation reactor, which are coupled to a polymeric fuel cell (PEMFC). The goal was to analyze and improve the fuel cell system performance by simulation techniques. PEMFC operation has been analyzed using an available parametric model, which was implemented within HYSYS environment software. Pinch Analysis concepts were used to investigate the process energy integration and determine the maximum efficiency minimizing ethanol consumption. The system performance was analyzed for the SR-12 Modular PEM Generator, the Ballard Mark V fuel cell and the BCS 500 W stack. The net system efficiency is dependent on the required power demand. Efficiency values higher than 50% at low loads and less than 30% at high power demands are computed. In addition, the effect of fuel cell temperature, pressure and hydrogen utilization was analyzed. The trade-off between the reformer yield and the fuel cell performance defines the optimal operation pressure. The cell temperature determines operating zones where the water, involved in the reforming reactions, can be produced or demanded.     

Isolated agenesis of the gallbladder. An intraoperative problem

Agenesis of the gallbladder and cystic duct is a rare congenital malformation. In 40-70% of cases this anomaly is associated with other gastrointestinal, skeletal, cardiovascular and genitourinary malformations. Lithiasis of the common bile duct is present in 25-50% of cases. In the majority of cases patients are asymptomatic or have symptoms compatible with a biliary disorder. A preoperative diagnosis is extremely difficult and the absence of the gallbladder is often an intraoperative finding. The authors report a case of isolated agenesis of the gallbladder. The relative embryology, development, diagnostic pitfalls, intraoperative behaviour and therapeutic strategies are discussed.     

Reaction Pathways in the Reduction of NO x Species by CO over Pt–Ba/Al2O3: Lean NO x Trap Catalytic Systems

The reduction by CO of NO _x species stored over Pt–Ba/Al₂O₃ Lean NO _x Trap systems is analysed in this work. The reaction mechanisms and pathways leading to N₂ formation both under dry and wet conditions are investigated by complementary transient dynamic experiments and FTIR analyses.     

Dominant Reaction Pathways in the Catalytic Partial Oxidation of CH4 on Rh

Reforming technologies are at the heart of converting fossil fuels and biofuels to syngas and hydrogen for novel energy applications and, among reforming technologies, catalytic partial oxidation is appealing for decentralized energy production due to the compactness of reactors. Yet, the mechanisms of these reactions are poorly understood. Here we combine fundamental surface chemistry and detailed reactor models to elucidate the pathways leading to syngas and propose strategies for optimizing the process.     

Preparation and characterisation of SrTi1−x−yZrxMnyO3 solid solution powders in relation to their use in combustion catalysis

Mixed oxides with compositions SrTi_1−x−yZr_xMn_yO₃, with 0 ≤ x ≤ 1 and 0 ≤ y ≤ 0.2 have been prepared with a conventional coprecipitation method. Some of them are constituted by very pure perovskite-type solid solution phases, with tetravalent Zr and Mn substituting for Ti in the B site. The addition of Zr to SrTiO₃ tends to increase the surface areas, while the insertion of Mn tends to decrease it. Mn-containing materials are active in the catalytic combustion of 1% methane in air at temperatures higher than 700 K and can be competitive with pure manganite perovskites like LaMnO₃ in spite of the lower Mn content. Pyridine adsorption experiments show that medium strength Lewis acid sites are located at the surface of these materials, and could be involved in the hydrocarbon CH bond activation.     

Characterization and properties of treated smectites

Two natural smectite clays named BC and AC were thermal and chemically treated. Apart from smectite, quartz and kaolinite, BC clay also contains calcite, whereas illite and higher quartz content is found in AC. Treatment at 823 K leads to a collapse of the smectite structure. Treating with H₂SO₄ or NaOH also leads to the elimination of calcite and Al and Si ions. The higher swelling capacity of BC clay is in accordance with its higher cation exchange capacity.${\gamma }_S^d$ values for both smectites decreases with the applied treatments. The surface acid–base constants determined for BC clay are higher than those obtained for AC independently of the applied treatment. This result together with the higher nanorugosity index, has been attributed to the higher quartz of the AC clay. Moreover, it has been observed that the cationic exchange capacity increases in both clays with the acidity of the surface.