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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Summertime partitioning and budget of NO(y) compounds in the troposphere over Alaska and Canada: ABLE 3B

As part of NASA's Arctic Boundary Layer Expedition 3A and 3B field measurement programs, measurements of NO(x), HNO3, PAN, PPN, and NO(y) were made in the middle to lower troposphere over Alaska and Canada during the summers of 1988 and 1990. These measurements are used to assess the degree of closure within the reactive odd nitrogen (N(x)O(y)) budget through the comparison of the values of NO(y) measured with a catalytic convertor to the sum of individually measured NO(y) (i) compounds (i.e., sigmaNO(y)(i) = NO(x) + HNO3 + PAN + PPN). Significant differences were observed between the various study regions. In the lower 6 km of the troposphere over Alaska and the Hudson Bay lowlands of Canada a significant fraction of the NO(y) budget (30 to 60%) could not be accounted for by the measured sigmaNO(y)i. This deficit in the NO(y) budget is about 100 to 200 parts per trillion by volume (pptv) in the lower troposphere (0.15 to 3 km) and about 200 to 400 pptv in the middle free troposphere (3 to 6.2 km). Conversely, the NO(y) budget in the northern Labrador and Quebec regions of Canada is almost totally accounted for within the combined measurement uncertainties of NO(y) and the various NO(y)(i) compounds. A substantial portion of the NO(y) budget's 'missing compounds' appears to be coupled to the photochemical and/or dynamical parameters influencing the tropospheric oxidative potential over these regions. A combination of factors are suggested as the causes for the variability observed in the NO(y) budget. In addition, the apparent stability of compounds represented by the NO(y) budget deficit in the lower-altitude range questions the ability of these compounds to participate as reversible reservoirs for 'active' odd nitrogen and suggest that some portion of the NO(y) budget may consist of relatively unreactive nitrogen-containing compounds.

Sandholm, S.↗
DOE OSTI2020

Improved Value of the Gasoline and Fuel Oil Co-Product Fractions Generated by the PNNL/LanzaTech Alcohol-to-Jet Process (Final Report)

The BETO-funded PNNL collaboration with LanzaTech, Inc. utilizes patented technology to address the need for low aromatic jet fuel blendstocks. The PNNL/LanzaTech alcohol-to-jet (ATJ) process converts ethanol from LanzaTech’s syngas fermentation process to jet-range isoparaffins. The aim of this Cooperative Research Development Agreement (CRADA) project was to improve the commercial viability of the LanzaTech/ PNNL ATJ process by developing two new co-product options. Two Focus Areas (FA) were explored: FA1) Increasing the RON of the lighter-than-jet gasoline fraction above 98; and FA2) Creating a synthetic lubricant base oil from the heavier-than-jet fraction. For FA 1, multiple processing approaches were evaluated, and RONs ranging from 96-100 were obtained, each comprising different processing costs. The most cost effective approach identified was a single-step process and yielded a liquid product of 97. Thus, additional development is required to obtain a RON > 98. We will continue work on this focus area with separate Direct Funding Opportunity (DFO) funding within the DOE-BETO Co-Optima Consortium (expected to begin Q2-FY21). Experimental work will focus on i) increasing single pass conversion to > 50%, and ii) obtaining a > 98 RON product. Technoeconomic analysis performed in this project suggests cost competitiveness provided these technical targets can be met. For FA2, multiple approaches were evaluated for increasing the viscosity index (VI) of the heavier-than-jet fraction to at least 120 in order to meet ASTM specifications for a Group III Base Oil (ASTM D6074). All other ASTM specifications are already met. A viscosity index of 115 was obtained, and with minimal undesirable cracking products. We believe a VI of 115 is about the highest possible from a catalytic approach, per review of the patent literature. In order to further increase the VI to > 120 we believe additives and/or liquid-liquid extraction is required. TEA performed earlier in the project suggests cost competitiveness with market prices assuming cracking byproducts are kept < 10 wt.%. If TEA updated with this additional processing still projects economic feasibility next steps could be taken in a subsequent effort.

02 PETROLEUM↗
DOE OSTI2027

A multi-region approach for the analysis of porous materials and gas-solid reactions using USAXS-SAXS-WAXS: application to CaO carbonation

The reaction rate of gas-solid non-catalytic reactions is typically investigated using reactant conversion data over time and ex-situ measurements of the porous solid reactant textural properties; these data enable the experimental estimation of the initial intrinsic reaction rate, whereas the evolution of the textural properties and the reaction rate over time are evaluated theoretically using reaction models. In this work, a different methodology is presented, based on: a) in-situ time-resolved USAXS-SAXS-WAXS measurements of the solid sample, and b) a multi-region modeling approach; this methodology allows for the estimation of the textural properties and the intrinsic reaction rate at any time during the reaction. Referring to a reaction in which a solid product is obtained from a solid reactant and a gaseous reactant, the porous particle is described as consisting of several distinct regions with different microstructural properties, and both a gas-solid reaction model and a SAXS model are derived and applied to the carbonation of porous CaO. The proposed reaction model highlights the role of the inaccessible reactant and accurately predicts the solid reactant conversion versus time profile. The SAXS model accurately predicts the measured linear trends of the Porod invariant and of the pre-factor of the power law scattering profile versus CaO mass fraction; in the absence of chemical reactions, the proposed equations extend classical SAXS theory to porous materials containing macropores and nonporous solid phases in addition to standard nanoscale inhomogeneous regions.

CO2 solid sorbents↗
DOE OSTI2020

Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

Abstract A new concept of single fuel reactivity-controlled compression ignition (RCCI) has been proposed through the catalytic partial oxidation (CPOX) reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two reformate mixtures from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivity fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before top dead center (TDC), whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and coefficient of variance (COV) of net indicated mean effective pressure (IMEPn) and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.

Engineering↗
DOE OSTI2020

Parallelized Screening of Characterized and DFT-Modeled Bimetallic Colloidal Cocatalysts for Photocatalytic Hydrogen Evolution

Using a newly designed and developed parallelized photoreactor and colorimetric detection method, a large sampling of bimetallic co-catalysts (Pd/Sn, Pd/Mo, Pd/Ru, Pd/Pb, Pd/Ni, Ni/Sn, Mo/Sn and Pt/Sn) for photocatalytic water reduction have been tested in this work. Of these co-catalysts, the combination of palladium and tin showed the highest synergistic behavior and peak hydrogen gas production at a low relative fraction of palladium. The resulting Pd/Sn bimetallic co-catalysts were characterized using high-angle annular dark-field (HAADF) and scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDS), and specifically, investigation of the palladium/tin mixture indicated that palladium and tin elements reside within the same particle. The experimental catalytic activity for the palladium/tin mixture was compared to density functional theory-derived energy values associated with the adsorption of hydrogen onto a surface. This comparison demonstrated that the typical peak found in electrochemical Sabatier volcano plots at ΔG H* = ~0 eV was replicated in the experimental photocatalytic system with a peak activity observed at ΔG H* = -0.036 eV. Computational confirmation of the results expressed here demonstrates the efficacy of colorimetric detection of hydrogen in parallel and presents a model for increasingly rapid catalyst screening.

08 HYDROGEN↗
DOE OSTI2022

Thermodynamic modeling of the Pd–Zn system with uncertainty quantification and its implication to tailor catalysts

Pd–Zn intermetallic catalysts show encouraging combinations of activity and selectivity on well-defined active site ensembles. Thermodynamic description of the Pd–Zn system, delineating phase boundaries and enumerating site occupancies within intermediate alloy phases, is essential to determining the ensembles of Pd–Zn atoms as a function of composition and temperature. Combining the present extensive first-principles calculations based on density functional theory (DFT) and available experimental data, the Pd–Zn system was remodeled using the CALculation of PHAse Diagrams (CALPHAD) approach. High throughput modeling tools with uncertainty quantification, i.e., ESPEI and PyCalphad, were incorporated in the phase analysis. Here, the site occupancies across the γ phase composition region were given special attention. A four-sublattice model was used for the γ phase owing to its four Wyckoff positions, i.e., the outer tetrahedral (OT) site 8c, the inner tetrahedral (IT) site 8c, the octahedral (OH) site 12e, and the cuboctahedral (CO) site 24g. The site fractions of Pd and Zn calculated from the present thermodynamic model show the occupancy preference of Pd in the OT and OH sublattices in agreement with experimental observations. The force constants obtained from DFT-based phonon calculations further supports the tendency of Pd occupying the OH sublattice compared with the IT and CO sublattice. The catalytic ensembles changing from Pd monomers (Pd 1 ) to trimers (Pd 3 ) on the surface of γ phase are attributed to the increase of Pd occupancy in the OH sublattice.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Diversification of aminoacyl-tRNA synthetase activities via genomic duplication

Intricate evolutionary events enabled the emergence of the full set of aminoacyl-tRNA synthetase (aaRS) families that define the genetic code. The diversification of aaRSs has continued in organisms from all domains of life, yielding aaRSs with unique characteristics as well as aaRS-like proteins with innovative functions outside translation. Recent bioinformatic analyses have revealed the extensive occurrence and phylogenetic diversity of aaRS gene duplication involving every synthetase family. However, only a fraction of these duplicated genes has been characterized, leaving many with biological functions yet to be discovered. Here we discuss how genomic duplication is associated with the occurrence of novel aaRSs and aaRS-like proteins that provide adaptive advantages to their hosts. We illustrate the variety of activities that have evolved from the primordial aaRS catalytic sites. This precedent underscores the need to investigate currently unexplored aaRS genomic duplications as they may hold a key to the discovery of exciting biological processes, new drug targets, important bioactive molecules, and tools for synthetic biology applications.

noncanonical functions↗
DOE OSTI2020

Macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite with the effects of dissolved carbonates under anoxic conditions

Manganese and its compounds have been extensively researched because of their far-reaching roles in a wide range of biogeochemical processes in natural systems. The (ad)sorption behavior of Mn(II), however, is poorly understood despite its important role as the primary reaction step for surface-catalyzed Mn(II) oxidation that is the principal abiotic process forming various Mn (oxyhydr)oxides in nature. Here, we systematically examined Mn(II) (ad)sorption to one of the most common natural sorbents, goethite, in oxygen- and carbonate-free systems. Traditional sorption edge and isotherm experiments were conducted by varying sorbate-to-sorbent ratio (0.027–15 μmol∙m -2 ) and solution pH (pH 5.0–9.0). The effects of dissolved carbonates on Mn(II) sorption were also assessed in a range of naturally prevalent concentrations (0.5–10 mM NaHCO 3 ). The Mn(II) uptake on goethite followed a typical Langmuir isotherm in the absence of dissolved carbonates, with increasing maximum adsorption capacities (Γ max ) from 0.19 at pH 6.5 to 3.4 μmol∙m -2 at pH 9.0. The presence of dissolved carbonates raised the extent of Mn(II) adsorption, which appeared to be directly correspondent to that of the adsorption of dissolved carbonates. Extended X-ray absorption fine structure (EXAFS) analysis indicated that Mn(II) predominantly formed inner-sphere binuclear bidentate surface complexes. Mn(II) uptake became deviated from the Langmuir model and showed a clear indication of surface precipitation when the Mn(II) sorption density (Γ) exceeded a threshold value in a given solution composition. This secondary Mn(II) phase was identified as rhodochrosite using X-ray diffraction (XRD) and transmission electron microscope (TEM). Furthermore, it would be plausible that a minor fraction of adsorbed Mn(II) coexisted with the secondary rhodochrosite according to a linear combination fitting (LCF) of the X-ray absorption near edge structure (XANES) spectra of Mn reference and samples. These systematic investigations of the macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite provide a critical avenue for disentangling surface-catalytic Mn(II) oxidation processes, which ultimately lead to the formation of diverse Mn (oxyhydr)oxides in the environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Simultaneous suppression of lignin, tricin and wall‐bound phenolic biosynthesis via the expression of monolignol 4‐ O ‐methyltransferases in rice

Summary Grass lignocelluloses feature complex compositions and structures. In addition to the presence of conventional lignin units from monolignols, acylated monolignols and flavonoid tricin also incorporate into lignin polymer; moreover, hydroxycinnamates, particularly ferulate, cross‐link arabinoxylan chains with each other and/or with lignin polymers. These structural complexities make grass lignocellulosics difficult to optimize for effective agro‐industrial applications. In the present study, we assess the applications of two engineered monolignol 4‐ O ‐methyltransferases (MOMTs) in modifying rice lignocellulosic properties. Two MOMTs confer regiospecific para ‐methylation of monolignols but with different catalytic preferences. The expression of MOMTs in rice resulted in differential but drastic suppression of lignin deposition, showing more than 50% decrease in guaiacyl lignin and up to an 90% reduction in syringyl lignin in transgenic lines. Moreover, the levels of arabinoxylan‐bound ferulate were reduced by up to 50%, and the levels of tricin in lignin fraction were also substantially reduced. Concomitantly, up to 11 μmol/g of the methanol‐extractable 4‐ O ‐methylated ferulic acid and 5–7 μmol/g 4‐ O ‐methylated sinapic acid were accumulated in MOMT transgenic lines. Both MOMTs in vitro displayed discernible substrate promiscuity towards a range of phenolics in addition to the dominant substrate monolignols, which partially explains their broad effects on grass phenolic biosynthesis. The cell wall structural and compositional changes resulted in up to 30% increase in saccharification yield of the de‐starched rice straw biomass after diluted acid‐pretreatment. These results demonstrate an effective strategy to tailor complex grass cell walls to generate improved cellulosic feedstocks for the fermentable sugar‐based production of biofuel and bio‐chemicals.

4-O-methylated↗
DOE OSTI2022

Thermal Hydroquinone Oxidation on Co/N-doped Carbon Proceeds by a Band-Mediated Electrochemical Mechanism

Molecules catalyze aerobic oxidation reactions via redox cycling at the metal center to effect sequential activation of O 2 and the substrate. Metal surfaces can catalyze the same transformations by coupling independent half-reactions for oxygen reduction and substrate oxidation mediated via the exchange of band-electrons. Metal/nitrogen-doped carbons (MNCs) are promising catalysts for aerobic oxidation that consist of molecule-like active sites embedded in a conductive carbon host. Owing to their combining molecular and metallic features, it remains unclear whether they proceed via the sequential redox cycling pathways of molecules or the band-mediated pathways of metals. Herein, we simultaneously track the potential of the catalyst and the rate of the turnover of aerobic hydroquinone oxidation on a cobalt-based MNC catalyst contacted to a catalytically inactive carbon electrode. By comparing operando measurements of rate and potential with the current-voltage behavior of each constituent half-reaction under identical conditions, we show that these molecular materials can display the band-mediated reaction mechanisms of extended metallic solids. Further, we show that the action of these band-mediated mechanisms explains fractional reaction orders in both oxygen and hydroquinone, the time evolution of catalyst potential and rate, and the dependence of rate on overall reaction free energy. Selective poisoning experiments suggest that oxygen reduction proceeds at cobalt sites, whereas quinone oxidation proceeds at native oxidic defects on the carbon. These findings highlight that molecule-like active sites can take advantage of band-mediated mechanisms when coupled to conductive hosts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Data for Simultaneous Suppression of Lignin, Tricin and Wall-Bound Phenolic Biosynthesis via the Expression of Monolignol 4- O -Methyltransferases in Rice

Grass lignocelluloses feature complex compositions and structures. In addition to the presence of conventional lignin units from monolignols, acylated monolignols and flavonoid tricin also incorporate into lignin polymer; moreover, hydroxycinnamates, particularly ferulate, cross-link arabinoxylan chains with each other and/or with lignin polymers. These structural complexities make grass lignocellulosics difficult to optimize for effective agro-industrial applications. In the present study, we assess the applications of two engineered monolignol 4- O -methyltransferases (MOMTs) in modifying rice lignocellulosic properties. Two MOMTs confer regiospecific para-methylation of monolignols but with different catalytic preferences. The expression of MOMTs in rice resulted in differential but drastic suppression of lignin deposition, showing more than 50% decrease in guaiacyl lignin and up to an 90% reduction in syringyl lignin in transgenic lines. Moreover, the levels of arabinoxylan-bound ferulate were reduced by up to 50%, and the levels of tricin in lignin fraction were also substantially reduced. Concomitantly, up to 11 μmol/g of the methanol-extractable 4- O -methylated ferulic acid and 5–7 μmol/g 4- O -methylated sinapic acid were accumulated in MOMT transgenic lines. Both MOMTs in vitro displayed discernible substrate promiscuity towards a range of phenolics in addition to the dominant substrate monolignols, which partially explains their broad effects on grass phenolic biosynthesis. The cell wall structural and compositional changes resulted in up to 30% increase in saccharification yield of the de-starched rice straw biomass after diluted acid-pretreatment. These results demonstrate an effective strategy to tailor complex grass cell walls to generate improved cellulosic feedstocks for the fermentable sugar-based production of biofuel and bio-chemicals.

Biomass Analytics↗
DOE OSTI2023

Renewable Diesel Production through Stand-Alone and Co-Hydrotreating of Catalytic Fast Pyrolysis Oil

Catalytic Fast Pyrolysis (CFP) of biomass followed by hydrotreating can be used for the production of renewable transportation fuels, such as sustainable aviation fuel and renewable diesel, which can reduce the dependence on fossil fuels and help achieve greenhouse gas reduction goals. Stand-alone hydrotreating of CFP oil and co-hydrotreating of the CFP oil with straight-run diesel (SRD) showed potential to produce high-quality diesel products in this study. Stand-alone hydrotreating of CFP oil produced a diesel fraction with oxygen content < 0.1 wt.% and an indicated cetane number (ICN) of 45. Co-hydrotreating of CFP oil and SRD using a 1:4 volumetric ratio produced diesel products with 0.1 wt.% of oxygen and ICNs of 42-45. Compared to CoMo/Al2O3, NiMo/Al2O3 was a more attractive catalyst for co-hydrotreating of two streams, leading to a higher carbon efficiency, a higher selectivity of cycloalkanes, a higher ICN, and enhanced desulfurization. Compared to stand-alone hydrotreating of CFP oil, co-hydrotreating with SRD could be achieved at a less severe operating condition and it produced hydrotreated products with a higher carbon efficiency. Synergy between CFP oil and SRD during co-hydrotreating process was suggested by the better experimental results in comparison with theoretical interpolation results. Co-hydrotreating gave high biogenic carbon incorporations of 91%-97% as determined by C-14 analysis.

biomass↗
DOE OSTI2022

Production and Catalytic Upgrading of 2,3-Butanediol Fermentation Broth into Sustainable Aviation Fuel Blendstock and Fuel Properties Measurement

With the increasing demand for sustainable supplies of aviation fuel and need to address climate change, new conversion technologies are needed to efficiently process biomass, produce high quality jet fuel blendstock, and meet carbon emission targets. This study demonstrates the synthesis, conditioning, and catalytic upgrading of 2,3-butanediol (BDO) fermentation broth into a jet fuel blendstock candidate. A high-titer 2,3-BDO fermentation broth (i.e., ~90 g/L) was produced at a 100-L scale and pretreated via nanofiltration to decrease the impurities level in the broth from 4.6 to 0.6 wt%. A novel process for catalytic upgrading of aqueous 2,3-BDO into a jet fuel blendstock candidate was developed, and each step was efficiently demonstrated. The catalytic steps include 1) 2,3-BDO dehydration into methyl ethyl ketone (MEK) over AlPO4, 2) MEK conversion into olefins over Zn1Zr10Ox, 3) oligomerization of olefins over a zeolite beta, and 4) hydrogenation over platinum/carbon. Both the model feed and real 2,3-BDO fermentation broth were tested for upgrading 2,3-BDO to MEK. With the real feed, a continuous loss of conversion (i.e., >50% loss over ~140 h time-on-stream [TOS]) was partly attributed to reversible deactivation from coking species. However, the conversion remained stable with the model feed, which demonstrates the efficiency of the first step for converting aqueous 2,3-BDO (10 wt% in water). For upgrading MEK to olefins, high selectivity to olefins (i.e., 82.5%) was obtained at high conversion levels (i.e., 93-98%) with stable conditions being achieved for > 70-hours TOS. Oligomerization of light olefins, which was demonstrated for > 270 h TOS, mainly led to the formation of dimers (C8-10) and trimers (C13-14). The oligomerized product was hydrogenated and distilled to recover the jet fraction (35 mass% or 40.9% carbon based yield), which consists mostly of desired isoalkanes (31.7 wt%), n-alkanes (24.5 wt%), and cycloalkanes (29.6 wt%). While some improvement is still needed to meet ASTM D7566 specifications for viscosity and final boiling point temperature, freezing point, density, aromatics content, and sulfur content of the jet blendstock candidate were within acceptable ranges, thus highlighting the potential of this process for production of jet fuel blendstock.

ADVANCED PROPULSION SYSTEMS,BIOMASS FUELS↗
DOE OSTI2020

Enhancing Four-Carbon Olefin Production from Acetylene over Copper Nanoparticles in Metal–Organic Frameworks

Four-carbon olefins, such as 1-butene and 1,3-butadiene, are important chemical feedstocks for the production of adhesives and synthetic rubber. These compounds are found in the C 4 fraction of “green oil” products that can arise during the hydrogenation of acetylene. Here, we demonstrate that control of the catalyst structure increases the yield and productivity of these important olefins with a family of catalyst materials comprising Cu nanoparticles (CuNPs) bound within the pores of Zr-based metal–organic frameworks. Using carbon monoxide as a probe molecule, we characterize the surfaces of these catalytic CuNPs with diffuse reflectance infrared Fourier transform spectroscopy, revealing that the electronic structure of the CuNP surfaces is size-dependent. Furthermore, we find that as the CuNP diameter decreases, the selectivity for C 4 products increases and that lowering the stoichiometric ratio of H 2 /acetylene improves the selectivity and productivity of the catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

A preliminary sensitivity analysis of the coupled diffusion and chemistry model

The sensitivity of the coupled chemistry/diffusion model's outputs to a wide range of variation of the model's independent variables has been investigated. It is shown that the efficiency with which the now catalytic cycle destroys ambient O3 is extremely sensitive to the amount of NO emitted and to the relative rates of turbulent diffusion and chemical reactions. For representative conditions in the stratosphere, a tenfold variation of either the turbulence intensity or the reaction rate constant or the source strength can vary the efficiency from 1% to 50%. If the duration of Phase 3 is a significant fraction of the total residence time of the plume, then these efficiency variations can alter O3 depletion rates by more than a factor of two. These results, therefore, point toward those variables which must be accurately defined or measured if one is to adequately predict the effect of SST operations on the ambient inventory of O3 in the lower stratosphere.

Hilst, G. R.↗
DOE OSTI2024

Influence of Domain Size and Support Composition on the Reducibility of SiO 2 and TiO 2 Supported Tungsten Oxide Clusters

Supported tungsten oxides are widely used in a variety of catalytic reactions. Depending on the support, the cluster size, oxidation state, reducibility and speciation of the tungsten oxides can widely differ. When promoted with a platinum group metal, the resulting spillover of hydrogen may facilitate the reduction of supported tungsten oxide species, depending on the support. High resolution scanning transmission electron microscopy imaging showed nanometer scale WO x clusters were synthesized on SiO 2 whereas highly dispersed species were formed on TiO 2 . Results from H 2 -temperature-programmed reduction showed the presence of Pd lowered the initial reduction temperature of SiO 2 -supported WO x species but interestingly did not affect that of TiO 2 -supported WO x . X-ray photoelectron and absorption spectroscopies showed the W atoms in SiO 2 -supported WO x species reduce from a +6 oxidation state to primarily +5 after thermal treatment in 5% H 2 , while the fraction of W in the +5 oxidation state was relatively unaffected by reduction treatment of TiO 2 -supported WO x . The unusual behavior of TiO 2 -supported WO x was explained by quantum chemical calculations that reveal the lack of change in the oxidation state of W is attributed to charge delocalization on the surface atoms of the titania support, which does not occur on silica. Moreover, modeling results at <600 K in the presence of H 2 suggest the formation of Brønsted acid sites, and the absence of Lewis acid sites, on larger aggregates of WO x on silica and all cluster sizes on titania. These results provide experimental and theoretical insights into the nature of supported tungsten oxide clusters under conditions relevant to various catalytic reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1978

Correlations of catalytic combustor performance parameters

Correlations for combustion efficiency percentage drop and the minimum required adiabatic reaction temperature necessary to meet emissions goals of 13.6 g CO/kg fuel and 1.64 g HC/kg fuel are presented. Combustion efficiency was found to be a function of the cell density, cell circumference, reactor length, reference velocity, and adiabatic reaction temperature. The percentage pressure drop at an adiabatic reaction temperature of 1450 K was found to be proportional to the reference velocity to the 1.5 power and to the reactor length. It is inversely proportional to the pressure, cell hydraulic diameter, and fractional open area. The minimum required adiabatic reaction temperature was found to increase with reference velocity and decrease with cell circumference, cell density and reactor length. A catalyst factor was introduced into the correlations to account for differences between catalysts. Combustion efficiency, the percentage pressure drop, and the minimum required adiabatic reaction temperature were found to be a function of the catalyst factor. The data was from a 12 cm-diameter test rig with noble metal reactors using propane fuel at an inlet temperature of 800 K.

Bulzan, D. L.↗
DOE OSTI2023

Direct catalytic conversion of alcohols to olefins of higher carbon number with reduced ethylene production

A catalyst composition for converting an alcohol to olefins, the catalyst composition comprising the following components: (a) a support (e.g., particles) comprising silicon and oxygen; (b) at least one of copper and silver residing on and/or incorporated into said support; and (c) at least one lanthanide element residing on and/or incorporated into said support. The catalyst may also further include component (d), which is zinc. Also described herein is a method for converting an alcohol to one or more olefinic compounds (an olefin fraction) by contacting the alcohol with a catalyst at a temperature of at least 100° C. and up to 500° C. to result in direct conversion of the alcohol to an olefin fraction containing one or more olefinic compounds containing at least three carbon atoms; wherein ethylene and propylene are produced in a minor proportion of the olefin fraction, and butenes and higher olefins are produced in major proportion.

Li, Zhenglong↗