Selective CO oxidation with real methanol reformate over monolithic Pt group catalysts: PEMFC applications

Alumina supported Pt group metal monolithic catalysts were investigated for selective oxidation of CO in hydrogen-rich methanol reforming gas for proton exchange membrane fuel cell (PEMFC) applications. The results are described and discussed in the present paper and show that Pt/γ_Al2O3$\mathrm{Pt}/\gamma {\mathrm{Al}}_2{\mathrm{O}}_3$ was the most promising candidate to selectively oxidize CO from an amount of about 1 vol% to less than 100 ppm. We have investigated the effect of the O₂ to CO feed ratio, the feed concentration of CO, the presence of H₂O and/or CO₂, and the space velocity on the activity, selectivity and stability of Pt/Al₂O₃ monolithic catalysts. Afterwards, the Pt/Al₂O₃ catalyst was scaled up and applied in 5 kW hydrogen producing systems based on methanol steam reforming and autothermal reforming. The hydrogen produced was then used as fuel for an integrated PEMFC.     

Catalytic steam reforming of acetic acid for hydrogen production

A variety of supported metal catalysts were tested under conditions of steam reforming of acetic acid (HAc), which was selected as a model compound for pyrolysis oil. The influence of several parameters on catalytic activity and selectivity were examined, including catalyst composition, i.e. nature of the metal and the carrier, reaction temperature and time on stream. The metallic phase of such catalysts was comprised of various metals, such as Pt, Pd, Rh, Ru and Ni, which were supported on metal oxides carriers, such as _Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$, _La2O3/_Al2O3${\mathrm{La}}_2{\mathrm{O}}_3/{\mathrm{Al}}_2{\mathrm{O}}_3$, MgO/_Al2O3$\mathrm{MgO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ and _CeO2/_Al2O3${\mathrm{CeO}}_2/{\mathrm{Al}}_2{\mathrm{O}}_3$. It was found that Ni-based and Ru-based catalysts present high activity and selectivity toward hydrogen production. Ru catalysts supported on _La2O3/_Al2O3${\mathrm{La}}_2{\mathrm{O}}_3/{\mathrm{Al}}_2{\mathrm{O}}_3$ and MgO/_Al2O3$\mathrm{MgO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ carriers, showed good long-term stability as a function of time on stream. However, Ni catalysts were not as stable as Ru catalysts. The amount of carbon deposited on each catalyst was estimated, and it was found that it depends strongly on the nature of the catalyst.     

Hydrogen production by autothermal reforming of LPG for PEM fuel cell applications

Indirect partial oxidation, or oxidative steam reforming, tests of a bimetallic Pt–Ni catalyst supported on δ$\delta$-alumina were conducted in propane–n  -butane mixtures (LPG) used as feed. _H2${\mathrm{H}}_2$ production activity and _H2/CO${\mathrm{H}}_2/\mathrm{CO}$ selectivity were investigated in response to different S/C, C/_O2$\mathrm{C}/{\mathrm{O}}_2$ and W/F ratios. It was confirmed that higher steam content in the reactant stream increases both the activity and the _H2/CO${\mathrm{H}}_2/\mathrm{CO}$ selectivity of the process. Low residence times created a positive impact on catalyst activity not only for hydrogen but also for carbon monoxide production due to the increased amount of fresh hydrocarbon in the feed stream. Hence, the highest selectivity level was obtained at intermediate residence times. The response of the system to C/_O2$\mathrm{C}/{\mathrm{O}}_2$ ratio was found to depend on the available steam content due to the complex nature of IPOX. The Pt–Ni catalyst was very prone to catalyst deactivation at low S/C ratios accompanied by high C/_O2$\mathrm{C}/{\mathrm{O}}_2$ ratios, but this problem was not encountered at high S/C ratios. A comparison of catalyst performance for different propane-to-n-butane ratios in the LPG feed indicated that the Pt–Ni catalyst has slightly better activity and selectivity at higher n-butane contents at the expense of becoming more sensitive to coke deposition.     

Hydrogen production by catalytic partial oxidation of methane and propane on Ni and Pt catalysts

In recent years the catalytic partial oxidation has been taken into consideration as a suitable process for hydrogen production, because of its exothermic nature which makes the process less energy and capital cost intensive with respect to steam reforming. In this paper the behaviour of three different catalyst typologies, two based on Ni–_Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$ (different in active phase composition) and one constituted by Pt supported on _CeO2${\mathrm{CeO}}_2$, is studied for partial oxidation of propane (as representative of liquefied petroleum gas). For comparison the same catalysts have been tested also in methane partial oxidation.     

Co-current and counter-current modes for methanol steam reforming membrane reactor

In this simulation study, methanol steam reforming reaction to produce synthesis gas has been studied in a membrane reactor when shell side and lumen side streams are in co-current mode or in counter-current mode. The simulation results for both co-current and counter-current modes are presented in terms of methanol conversion and molar fraction versus temperature, pressure, _H2O/_CH3OH${\mathrm{H}}_2\mathrm{O}/{\mathrm{CH}}_3\mathrm{OH}$ molar feed flow rate ratio and axial co-ordinate.     

Experimental investigation on the effect of natural gas composition on performance of autothermal reforming

This paper presents experimental study on catalytic autothermal reforming (ATR) of natural gas (NG) for hydrogen (_H2${\mathrm{H}}_2$) production over sulfide nickel catalyst supported on gamma alumina. The experiments are conducted on a cylindrical reactor of 30 mm in diameter and 200 mm in length with “simulated” NG of different composition under thermal-neutral conditions and fed with different molar air to fuel ratio (A/F$A/F$) and molar water to fuel ratio (W/F)$(W/F)$. The results showed that reforming performance is significantly dependent on A/F$A/F$, W/F$W/F$ and concentration of _C2+${\mathrm{C}}_{2+}$ hydrocarbons in inlet fuel. Fuels containing higher _C2+${\mathrm{C}}_{2+}$ hydrocarbons concentration have optimum performance in terms of more _H2${\mathrm{H}}_2$ at higher A/F$A/F$ and W/F$W/F$ but lower conversion efficiency. Good performance for ATR of fuel containing 15%–20% _C2H6${\mathrm{C}}_2{\mathrm{H}}_6$ can be achieved at A/F=5–7$A/F=5–7$ and W/F=4–6$W/F=4–6$, much higher than that for optimum performance of ATR of methane (A/F=3,W/F=2–2.5$A/F=3,W/F=2–2.5$). _CO2${\mathrm{CO}}_2$ in the inlet fuel does not have significant effect on the reversed water–gas shift reaction. Its effect on reforming performance is mainly due to the dilution of inlet fuel and products.     

Effect of Al and Ce substitutions of the electrochemical properties of amorphous MgNi-based alloy electrodes

Mg-based hydrogen storage alloys _{Mg0.9Al0.1-xCex}Ni${\mathrm{Mg}}_{0.9}{\mathrm{Al}}_{0.1-x}{\mathrm{Ce}}_x\mathrm{Ni}$(x=0.00,0.01,0.02,0.025,0.075)$(x=0.00,0.01,0.02,0.025,0.075)$ were successfully prepared by means of mechanical alloying (MA). The structure and the electrochemical characteristics of these Mg-based electrodes were also studied. The result of X-ray diffraction (XRD) shows that the main phases of the alloys exhibit amorphous structures. The charge–discharge cycle tests indicate these alloys have good electrochemical active characteristics. Among these alloys, the _{Mg0.9Al0.08Ce0.02}Ni${\mathrm{Mg}}_{0.9}{\mathrm{Al}}_{0.08}{\mathrm{Ce}}_{0.02}\mathrm{Ni}$ has the best cycle stability. After 50 cycles charge–discharge, the discharge capacity of _{Mg0.9Al0.08Ce0.02}Ni${\mathrm{Mg}}_{0.9}{\mathrm{Al}}_{0.08}{\mathrm{Ce}}_{0.02}\mathrm{Ni}$ alloy is 66.67% higher than MgNi alloy. The cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS) and anticorruption test (potentiodynamic polarization) were also studied, and the results show that the electrochemical cycle stability of these alloys was improved by Al and Ce substitutions.     

H2 production with ultra-low CO selectivity via photocatalytic reforming of methanol on Au/TiO2 catalyst

_H2${\mathrm{H}}_2$ with ultra-low CO concentration was produced via photocatalytic reforming of methanol on Au/_TiO2$\mathrm{Au}/{\mathrm{TiO}}_2$ catalyst. The rate of _H2${\mathrm{H}}_2$ production is greatly increased when the gold particle size is reduced from 10 to smaller than 3 nm. The concentration of CO in _H2${\mathrm{H}}_2$ decreases with reducing the gold particle size of the catalyst. It is suggested that the by-product CO is mostly produced via decomposition of the intermediate formic acid species derived from methanol. The smaller gold particles possibly switch the HCOOH decomposition reaction mainly to _H2${\mathrm{H}}_2$ and _CO2${\mathrm{CO}}_2$ products while suppress the CO and _H2${\mathrm{H}}_2$O products. In addition, some CO may be oxidized to _CO2${\mathrm{CO}}_2$ by photogenerated oxidizing species at the perimeter interface between the small gold particles and _TiO2${\mathrm{TiO}}_2$ under photocatalytic condition.