Daniel R. Palo

Synthesis of methanol and dimethyl ether from syngas over Pd/ZnO/Al2O3 catalysts

A Pd/ZnO/Al2O3 catalyst was developed for the synthesis of methanol and dimethyl ether (DME) from syngas with temperatures of operation ranging from 250 °C to 380 °C. High temperatures (e.g. 380 °C) are of interest when combining methanol and DME synthesis with a methanol to gasoline (MTG) process in a single reactor bed. A commercial Cu/ZnO/Al2O3 catalyst, utilized industrially for the synthesis of methanol at 220–280 °C, suffers from a rapid deactivation when the reaction is conducted at high temperature (> 320 °C). On the contrary, a Pd/ZnO/Al2O3 catalyst was found to be highly stable for methanol and DME synthesis at 375 °C. The Pd/ZnO/Al2O3 catalyst was thus further investigated for methanol and DME synthesis at P = 34–69 bar, T = 250–380 °C, GHSV = 5000–18 000 h−1, and molar feeds H2/CO = 1, 2, and 3. Selectivity to DME increased with decreasing operating temperature, and increasing operating pressure. Higher space velocity and H2/CO syngas feed ratios also enhanced DME selectivity. Undesirable CH4 formation was observed, however, it could be lessen through choice of process conditions and by catalyst design. By studying the effect of the Pd loading and the Pd : Zn molar ratio the formulation of the Pd/ZnO/Al2O3 catalyst was optimized. A catalyst with 5% Pd and a Pd : Zn molar ratio of 0.25 : 1 has been identified as the preferred catalyst. Results indicate that PdZn particles are more active than Pdo particles for the synthesis of methanol and less active for CH4 formation. A correlation between DME selectivity and concentration of acid sites has been established. Hence, two types of sites are required for the direct conversion of syngas to DME: (1) PdZn particles are active for the synthesis of methanol from syngas, and (2) acid sites which are active for the conversion of methanol to DME. Additionally, CO2 formation was problematic as PdZn was found to be active for the water-gas-shift (WGS) reaction, under all the conditions evaluated.

Single-step syngas-to-distillates (S2D) process based on biomass-derived syngas – A techno-economic analysis

This study compared biomass gasification based syngas-to-distillate (S2D) systems using techno-economic analysis (TEA). Three cases, state of technology (SOT), goal, and conventional, were compared in terms of performance and cost. The SOT case represented the best available experimental results for a process starting with syngas using a single-step dual-catalyst reactor for distillate generation. The conventional case mirrored a conventional two-step S2D process consisting of separate syngas-to-methanol and methanol-to-gasoline (MTG) processes. The goal case assumed the same performance as the conventional, but with a single-step S2D technology. TEA results revealed that the SOT was more expensive than the conventional and goal cases. The SOT case suffers from low one-pass yield and high selectivity to light hydrocarbons, both of which drive up production cost. Sensitivity analysis indicated that light hydrocarbon yield and single pass conversion efficiency were the key factors driving the high cost for the SOT case.

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.

Development and Demonstration of a Prototype Solar Methane Reforming System for Thermochemical Energy Storage - Including Preliminary Shakedown Testing Results

12 Infinia Corporation This paper reports on the design, fabrication and preliminary testing of a solar steam- methane reforming system including a parabolic dish solar concentrator, the endothermic chemical reactor and associated heat exchangers. During shakedown testing, methane conversions exceeded 90% and solar-to-chemical energy conversions of about 63 ± 4% were obtained, based on the change in the higher heating value of the stream. Potential applications include thermochemical energy storage for concentrating solar power generation facilities and solar augments of fossil and biomass fuels for power generation and/or synthetic fuel production.

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.

Cycle Evaluations of Reversible Chemical Reactions for Solar Thermochemical Energy Storage in Support of Concentrating Solar Power Generation Systems

The production and storage of thermochemical energy is a possible route to increase capacity factors and reduce the Levelized Cost of Electricity from concentrated solar power generation systems. In this paper, we present the results of cycle evaluations for various thermochemical cycles, including a well-documented ammonia closed-cycle along with open- and closed-cycle versions of hydrocarbon chemical reactions. Among the available reversible hydrocarbon chemical reactions, catalytic reforming-methanation cycles are considered; specifically, various methane-steam reforming cycles are compared to the ammonia cycle. In some cases, the production of an intermediate chemical, methanol, is also included with some benefit being realized. The best case, based on overall power generation efficiency and overall plant capacity factor, was found to be an open cycle including methane-steam reforming, using concentrated solar energy to increase the chemical energy content of the reacting stream, followed by combustion to generate heat for the heat engine.

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

The objective of the work was to enhance price-competitive, synthesis gas (syngas)-based production of transportation fuels that are directly compatible with the existing vehicle fleet (i.e., vehicles fueled by gasoline, diesel, jet fuel, etc.). To accomplish this, modifications to the traditional methanol-to-gasoline (MTG) process were investigated. In this study, we investigated direct conversion of syngas to distillates using methanol and dimethyl ether intermediates. For this application, a Pd/ZnO/Al2O3 (PdZnAl) catalyst previously developed for methanol steam reforming was evaluated. The PdZnAl catalyst was shown to be far superior to a conventional copper-based methanol catalyst when operated at relatively high temperatures (i.e., >300°C), which is necessary for MTG-type applications. Catalytic performance was evaluated through parametric studies. Process conditions such as temperature, pressure, gas-hour-space velocity, and syngas feed ratio (i.e., hydrogen:carbon monoxide) were investigated. PdZnAl catalyst formulation also was optimized to maximize conversion and selectivity to methanol and dimethyl ether while suppressing methane formation. Thus, a PdZn/Al2O3 catalyst optimized for methanol and dimethyl ether formation was developed through combined catalytic material and process parameter exploration. However, even after compositional optimization, a significant amount of undesirable carbon dioxide was produced (formed via the water-gas-shift reaction), and some degree of methane formation could not be completely avoided. Pd/ZnO/Al2O3 used in combination with ZSM-5 was investigated for direct syngas-to-distillates conversion. High conversion was achieved as thermodynamic constraints are alleviated when methanol and dimethyl are intermediates for hydrocarbon formation. When methanol and/or dimethyl ether are products formed separately, equilibrium restrictions occur. Thermodynamic relaxation also enables the use of lower operating pressures than what would be allowed for methanol synthesis alone. Aromatic-rich hydrocarbon liquid (C5+), containing a significant amount of methylated benzenes, was produced under these conditions. However, selectivity control to liquid hydrocarbons was difficult to achieve. Carbon dioxide and methane formation was problematic. Furthermore, saturation of the olefinic intermediates formed in the zeolite, and necessary for gasoline production, occurred over PdZnAl. Thus, yield to desirable hydrocarbon liquid product was limited. Evaluation of other oxygenate-producing catalysts could possibly lead to future advances. Potential exists with discovery of other types of catalysts that suppress carbon dioxide and light hydrocarbon formation. Comparative techno-economics for a single-step syngas-to-distillates process and a more conventional MTG-type process were investigated. Results suggest operating and capital cost savings could only modestly be achieved, given future improvements to catalyst performance. Sensitivity analysis indicated that increased single-pass yield to hydrocarbon liquid is a primary need for this process to achieve cost competiveness.

Copper nanoparticle synthesis in continuous mode by the polyol method - Progress towards Nanomanufacturing

Transition of batchwise nanoparticle production routes to large-scale manufacturing processes is vital for commercialization of such materials. This paper reports the comparison studies from batch and continuous mode for the synthesis of copper nanoparticles by the polyol method. The copper nanoparticles synthesized in continuous mode utilizing a novel microchannel mixer were found to be comparable to the nanoparticles developed in batch mode. Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), and Selected Area Electron Diffraction (SAED) techniques were used for characterization of the copper nanoparticles produced.