Jianli Hu

Steam reforming of methanol over highly active Pd/ZnO catalyst

Abstract Pd/ZnO catalysts were investigated for steam reforming of methanol. Unlike precious metal-based catalysts, Pd/ZnO catalysts not only exhibited high activity, but more importantly very low selectivity to CO for methanol steam reforming. Under the conditions examined, the decomposition activity is minimal. The novel function is attributed to the formation of highly structured Pd–Zn alloy at moderate temperatures under mild reducing environments. The current catalytic system was characterized by TPR, transmission electron microscopy (TEM), H 2 chemisorption, and X-ray diffraction (XRD).

Catalytic Decomposition of Toxic Chemicals Over Iron Group Metals Supported on Carbon Nanotubes

This study explores catalytic decomposition of phosphine (PH3) using iron group metals (Co, Ni) and metal oxides (Fe2O3, Co(3)O4, NiO) supported on carbon nanotubes (CNTs). The catalysts are synthesized by means of a deposition-precipitation method. The morphology, structure, and composition of the catalysts are characterized using a number of analytical instrumentations, including high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurement, and inductively coupled plasma. The activity of the catalysts in the PH3 decomposition reaction is measured and correlated with their surface and structural properties. The characterization results show that phosphidation occurs on the catalyst surface, and the resulting metal phosphides act as an active phase in the PH3 decomposition reaction. Cobalt phosphide, CoP, is formed on Co/CNTs and Co(3)O4/CNTs, whereas iron phosphide, FeP, is formed on Fe2O3/CNTs. In contrast, phosphorus-rich phosphide NiP2 is formed on Ni/CNTs and NiO/CNTs. The initial activities of the catalysts are shown in the following sequence: Ni/CNTs > Co/CNTs > Co(3)O4/CNTs >NiO/CNTs > Fe2O3/CNTs, whereas activities of metal phosphides are shown in the following order: CoP > NiP2 > FeP. The catalytic activity of metal phosphides is attributed to their electronic properties. Cobalt phosphide formed on Co/CNTs and Co(3)O4/CNTs exhibits not only the highest activity, but also long-term stability in the PH3 decomposition reaction.

Miniature Fuel Processors for Portable Fuel Cell Power Supplies

Miniature and micro-scale fuel processors are discussed. The enabling technologies for these devices are the novel catalysts and the micro-technology-based designs. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher, while maintaining a carbon monoxide levels at 1% or less. The micro-technology-based designs enable the devices to be extremely compact and lightweight. The miniature fuel processors can nominally provide between 25-50 watts equivalent of hydrogen which is ample for soldier or personal portable power supplies. The integrated processors have a volume less than 50 cm3, a mass less than 150 grams, and thermal efficiencies of up to 83%. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, etc., the energy density was estimated at 1700 Whr/kg. The miniature processors have been demonstrated with a carbon monoxide clean-up method and a fuel cell stack. The micro-scale fuel processors have been designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%. They have a volume of less than 0.25 cm3 and a mass of less than 1 gram.

High-Efficiency Microscale Power Using a Fuel Processor and Fuel Cell

A microscale power device, composed of a fuel processor and a fuel cell, is described, and results of testing conducted with the fuel reformer are presented. The microscale fuel reformer strips hydrogen from a hydrocarbon fuel, such as methanol, and the hydrogen-rich stream can then be fed to a fuel cell to generate electrical power. In the tests discussed here, the fuel reformer, utilizing methanol, was able to provide up to 100 mWe of hydrogen at an efficiency of up to 4.8%. The device was able to operate independent of any additional external heating, even during start-up.

Carbon dioxide conversion to valuable chemical products over composite catalytic systems

Abstract This paper reports an experimental study on catalytic conversion of carbon dioxide to methanol, ethanol and acetic acid. Catalysts having different catalytic functions were synthesized and combined in different ways to enhance the selectivity to desired products. The combined catalyst system possessed the following functions: methanol synthesis, Fischer-Tropsch synthesis, water-gas-shift and hydrogenation. Results showed that the methods of integrating these catalytic functions played an important role in achieving the desired product selectivity. We speculate that if methanol synthesis sites were located adjacent to the C–C chain growth sites, the formation rate of C2 oxygenates would be enhanced. The advantage of using a high temperature methanol catalyst PdZnAl in the combined catalyst system was demonstrated. In the presence of PdZnAl catalyst, the combined catalyst system was stable at 380 °C. It was observed that, at high temperature, kinetics favored oxygenate formation. The results implied that the process can be intensified by operating at high temperature using Pd-based methanol synthesis catalyst. Steam reforming of the byproduct organics was demonstrated as a means to provide supplemental hydrogen. Preliminary process design, simulation, and economic analysis of the proposed CO2 conversion process were carried out. Economic analysis indicates how ethanol production cost was affected by the price of CO2 and hydrogen.

Compact Reverse Water-Gas-Shift Reactor for Extraterrestrial In Situ Resource Utilization

A compact reverse water-gas-shift reactor suitable for extraterrestrial use as part of the in situ propellant production system is reported. The reactor is less than 15 cm 3 in volume and weighs less than 50 g. With an Ru/ZrO 2 -CeO catalyst it produces over 150 g H 2 O/h operating at 800°C. This is near equilibrium conversion at about half-scale of a Mars sample-return mission. Even at these high processing rates, the pressure drop remains low (from 1.6 to 7.6 kPa).

Fuel processor development for a soldierportable fuel cell system

The remarkable recent advances in wireless and portable communications devices (e.g., laptop computers, cellular phones, portable digital assistants) have fueled a need for high-energy-density portable power sources for consumer use. Similarly, interest in portable power sources has increased in the military and intelligence communities. Currently, portable military electronics are dependent on batteries to supply electrical power for long-duration missions. This poses two major problems which result from the low energy density of current battery systems: excessive weight/bulk, and reduced mission duration.

Catalytic Fast Pyrolysis of Cellulose by Integrating Dispersed Nickel Catalyst with HZSM-5 Zeolite

The effect of integrating dispersed nickel catalyst with HZSM-5 zeolite on upgrading of vapors produced from pyrolysis of lignocellulosic biomass was investigated. The active component nickel nitrate was introduced onto the cellulose substrate by impregnation technique. Based on TGA experimental results, we discovered that nickel nitrate first released crystallization water, and then successively decomposed into nickel oxide which was reduced in-situ to metallic nickel through carbothermal reduction reaction. In-situ generated nickel nanoparticles were found highly dispersed over carbon substrate, which were responsible for catalyzing reforming and cracking of tars. In catalytic fast pyrolysis of cellulose, the addition of nickel nitrate caused more char formation at the expense of the yield of the condensable liquid products. In addition, the selectivity of linear oxygenates was increased whereas the yield of laevoglucose was reduced. Oxygen-containing compounds in pyrolysis vapors were deoxygenated into aromatics using HZSM-5. Moreover, the amount of condensable liquid products was decreased with the addition of HZSM-5.

Deoxygenation of methyl laurate over Ni based catalysts: Influence of supports

The use of a series of nickel based catalysts supported over HZSM-5, Al2O3, C and ZrO2 in the deoxygenation of methyl laurate shows that the deoxygenation activity and deoxygenation pathway of nickel based catalysts can be affected by properties of catalysts. In the absence of H2, β−elimination of methyl laurate is the dominant reaction and a small amount of laurate acid is converted into undecane by direct decarboxylation. At the same time, the highly acidic support HZSM-5 gave higher conversion and C11 alkane selectivity. In the presence of H2, Ni/HZSM-5 catalyst showed a significantly high deoxygenation activity, producing 71% alkanes by methyl laurate conversion at 280 °C and 4MPa H2. While as on mildly acidic (Al2O3) and neutral (C) supports, a restricted hydrodeoxygenation activity was achieved but more oxygenate products were yielded. According to the analysis of intermediate product, the deoxygenation reaction of methyl laurate follows three distinct pathways: in the absence of H2, decarboxylation...