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At least 199 records · Page 11

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Platinized tin oxide catalysts for CO2 lasers - Effects of pretreatment

Platinized tin oxide surfaces used for low-temperature CO oxidation in CO2 lasers have been characterized before and after reduction in CO at 125 and 250 C using ion scattering spectroscopy (ISS) and X-ray photoelectron spectroscopy (XPS). XPS indicates that the Pt is present initially as Pto2. Reduction at 125 C converts the PtO2 to Pt(OH)2 while reduction at 250 C converts the PtO2 to metallic Pt. ISS shows that the Pt in the outermost atomic layer of the catalyst is mostly covered by substrate species during the 250 C reduction. Both the ISS and XPS results are consistent with Pt/Sn alloy formation. The surface dehydration and migration of substrate species over surface Pt and Sn appear to explain why a CO pretreatment at 250 C produces inferior CO oxidation activities compared to a 125 C pretreatment.

Gardner, Steven D.↗

NASA NTRS1993

Microwave Pretreatment For Hydrolysis Of Cellulose

Microwave pretreatment enhances enzymatic hydrolysis of cellulosic wastes into soluble saccharides used as feedstocks for foods, fuels, and other products. Low consumption of energy, high yield, and low risk of proposed hydrolysis process incorporating microwave pretreatment makes process viable alternative to composting.

Cullingford, Hatice S.↗

NASA NTRS2010

Cleanser, Detergent, Personal Care Product Pretreatment Evaluation

The purpose of the Cleanser, Detergent, Personal Care Product, and Pretreatment Evaluation & Selection task is to identify the optimal combination of personal hygiene products, crew activities, and pretreatment strategies to provide the crew with sustainable life support practices and a comfortable habitat. Minimal energy, mass, and crew time inputs are desired to recycle wastewater during long duration missions. This document will provide a brief background on the work this past year supporting the ELS Distillation Comparison Test, issues regarding use of the hygiene products originally chosen for the test, methods and results used to select alternative products, and lessons learned from testing.

Adam, Niklas↗

NASA NTRS2011

Cleanser, Detergent, Personal Care Product, and Pretreatment Evaluation

Adam, Niklas↗

NASA NTRS2013

GSDO Program Hexavalent Chrome Alternatives: Final Pretreatments Test Report

Hexavalent chrome free pretreatments should be considered for use on Ground Support Equipment (OSE) and Electrical Ground Support Equipment (EOSE). Both of the hexavalent chrome free pretreatments (Metalast TCP HF and SurTec 650C) evaluated by this project met, and in some instances exceeded, the requirements ofMIL-DTL-5541 "Chemical Conversion Coatings on Aluminum and Aluminum Alloys". For DC resistance measurements, both Metalast TCP HF and SurTec (!50C met initial requirements following assembly and in many cases continued to maintain passing readings for the duration of testing.

Kessel, Kurt↗

NASA NTRS2015

Urine Pretreatment History and Perspective in NASA Human Spaceflight

Urine pretreatment is a technology that may seem to have small mass impacts in future spaceflight missions, but can have significant impacts on reliability, life, and performance of the rest of the wastewater management and recovery systems. NASA has experience with several different urine pretreatment systems, including those flow on the space shuttle, evaluated for NASA waste collection systems or used in Russian commodes on ISS, or developed by NASA or industry as alternatives. Each has had unique requirements for shelf life, operational life, and the life or conditions of the stored, treated urine. Each was evaluated under different test conditions depending on mission, and depending on testing experience developed over NASA's history. Those that were flown led to further lessons learned about hardware compatibility and control. As NASA looks forward to human spaceflight missions beyond low Earth orbit, these techniques need to be evaluated in new light. Based on published design reference missions, candidate requirements can be derived for future systems. Initial comparisons between these requirements and previous performance or test results can be performed. In many cases these comparisons reveal data gaps. Successful previous performance is not enough to address current needs.

Anderson, Molly↗

DOE OSTI2023

Unlocking High Capacity and Fast Na + Diffusion of H x CrS 2 by Proton-Exchange Pretreatment

This study presents a new material, “H x CrS 2 " (denotes approximate composition) formed by proton-exchange of NaCrS 2 which has a measured capacity of 728 mAh g -1 with significant improvements to capacity retention, sustaining over 700 mAh g -1 during cycling experiments. This is the highest reported capacity for a transition metal sulfide electrode and outperforms the most promising proposed sodium anodes to date. H x CrS 2 exhibits a biphasic structure featuring alternating crystalline and amorphous lamella on the scale of a few nanometers. This unique structural motif enables reversible access to Cr redox in the material resulting in higher capacities than seen in the parent structure which features only S redox. In conclusion, pretreatment by proton-exchange offers a route to materials such as H x CrS 2 which provide fast diffusion and high capacities for sodium-ion batteries.

25 ENERGY STORAGE↗

DOE OSTI2023

Investigation of the effects of ternary deep eutectic solvent composition on pretreatment of sorghum stover

Biomass‐derived deep eutectic solvents (DESs) have been introduced as promising pretreatment and fractionation solvents because of their mild processing conditions, easy synthesis, and green solvent components from biomass. In recent DES studies, solvent‐based third constituents like water, ethanol, and others improve the processibility of typical binary DESs. However, the impacts of these components are not well understood. Here, two solvent‐based constituents, including water and ethylene glycol, were applied to 3,4‐dihydroxybenzoic acid (DHBA)‐based DES system for improving the conversion efficiency of cellulose‐rich fraction and the properties of lignin fraction. Chemical composition, enzymatic digestibility, degree of polymerization of cellulose and physicochemical properties of lignin were used to evaluate the impact of each third constituent on biomass processing. Ternary ChCl‐DHBA DESs exhibited better performances in delignification, fermentable sugar production, and preservation of β‐O‐4 ether linkage in lignin compared with binary ChCl‐DHBA DES.

09 BIOMASS FUELS↗

DOE OSTI2020

2D HSQC Chemical Shifts of Impurities from Biomass Pretreatment

Two dimensional (2D) heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) is a powerful analytical method which can be used to elucidate the structure of biomass. During processing, biomass is typically subjected to some form of chemical treatment which can be performed with a variety of compounds. The presence of these compounds, even in trace amounts, has the potential to contaminate the sample and lead to misinterpretation of the HSQC spectra. Here we report the chemical shifts of 29 compounds commonly used in biomass processing which have the potential to contaminate the biomass samples and lead to the misinterpretation of peaks associated with biomass (Populus trichocarpa ) pretreated via autohydrolysis. The identification of these chemical shifts could serve as a valuable tool in preventing errors in characterizing biomass via HSQC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Assessing the availability of two bamboo species for fermentable sugars by alkaline hydrogen peroxide pretreatment

We report this study comprehensively investigated two bamboo species (i.e. Neosinocalamus affinis and Phyllostachys edulis) in terms of their cell wall ultrastructure, chemical compositions, enzymatic saccharification, and lignin structure before and after alkaline hydrogen peroxide pretreatment (AHP). During AHP, Neosinocalamus affinis (NAB) had higher delignification than Phyllostachys edulis (PEB), and thus showed better enzymatic digestibility (93.05% vs 53.57% for glucan). The fundamental chemical behavior of the bamboo lignins was analyzed by fluorescence microscope (FM), confocal Raman microscope (CRM), molecular weight analysis, and 2D HSQC-NMR. Results indicated that the PEB has thicker cell wall and more concentrated lignin in its compound middle lamella and cell corner middle lamella than NAB. Moreover, PEB lignin contains more G units (S/G of 0.95), in evident contrast to that of NAB lignin (S/G of 1.30), which favor the formation of C–C linkages, thus impeding its degradation during the AHP.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Modelling a compressible packed bed flow-through washing and deacetylation reactor for corn stover pretreatment

The deacetylation process is a key step in the lignocellulosic biomass pretreatment process that currently is done in batch reactors. A flow-through diffuser type reactor is a promising approach to make the process more efficient and economically favorable. A washing step before deacetylation can further reduce chemical usage and increase the process efficiency. However, the highly compacted biomass particles can cause significant pressure-drop for fluid flow through the bed, which in the worst case can cause self-enhancing pressure-drop leading to reactor blocking. Detailed understanding of the fundamentals of flow through a compressible packed bed is necessary to scale up the washing and deacetylation process. This work closely examines the classical Kozeny Carman equation and proposes modifications to accurately predict the pressure-drop at different compaction states. Here, a compressible packed bed model is further developed based on the interaction between solid mechanics and fluid dynamics. Experimental measurements of water flow through a packed bed of corn stover show good agreement with the developed model. Corn stover washing process scale up simulations show that smaller reactor diameter, higher friction lining material, lower process throughput, and higher process temperature is favorable in stabilizing the bed from extensive compression when the bed height is fixed.

09 BIOMASS FUELS↗

DOE OSTI2025

Impact of corrosion layer composition and thermal pretreatment on the radiolytic generation of molecular hydrogen from aluminum alloys

To fully evaluate the feasibility of extending the dry storage of aluminum-clad spent nuclear fuel (ASNF) in helium-backfilled cannisters, the amount of radiation-induced molecular hydrogen (H 2 ) generated and the impact of absorbed radiation dose on the ASNF corrosion layer composition must be accurately assessed. Here, in this study, we report a slowing in the rate of radiolytic H 2 generation for pre-corroded AA1100 and AA6061 aluminum alloy coupons irradiated to up to 53 MGy of absorbed cobalt-60 gamma dose. By exploring a variety of thermal pretreatment conditions for AA6061 coupons, we find that the “steady-state” yield of H 2 depends more on the aluminum alloy used than on the treatments applied prior to dry storage. Scanning electron microscopy and positron annihilation lifetime spectroscopy techniques also provided evidence for gamma radiation-induced defects in the corrosion layers of the investigated aluminum alloy coupons for high absorbed doses (~50 MGy), the consequences of which on cladding integrity and H 2 generation should be explored in future works.

38 - RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCL↗

DOE OSTI2022

High-Temperature Pretreatment Effect on Co/SiO 2 Active Sites and Ethane Dehydrogenation

Here, we report the synthesis, optimization, and characterization of Co/SiO 2 for ethane nonoxidative dehydrogenation. Co/SiO 2 is synthesized via strong electrostatic adsorption using the widely available Co(NO 3 ) 2 as the precursor. We demonstrate that high-temperature pretreatment (900 °C) in an inert atmosphere can significantly enhance the initial activity of the Co/SiO 2 catalyst. X-ray absorption near-edge spectroscopy (XANES), temperature-programmed reduction (TPR), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) suggest that highly dispersed Co(II) clusters are more active than Co 0 or CoO x nanoparticles. Fourier transform infrared (FTIR) and isopropanol (IPA) temperature-programmed desorption and density functional theory (DFT) calculations suggest that high-temperature treatment significantly increases the density of active Lewis acid sites, possibly via surface dehydroxylation of the catalyst.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Membrane Contactors for Ammonia Recovery from Anaerobic Digester Centrate: Pretreatment and Process Optimization

Haber-Bosch process allows for the production of modern fertilizers and is crucial for meeting increasing demands for agricultural production. The process requires large amounts of natural gas and contributes to global warming. An alternative to the Haber-Bosch process utilizes membrane contactors to recover nitrogen from the anaerobic digester centrate. In previous studies, high recoveries have been achieved, but membrane fouling decreased the performance and required maintenance to clean the membranes. Furthermore, this study investigated the effect of a settling and ultrafiltration system to pretreat centrate from an anaerobic digester to prevent fouling of the membrane contactor system. The system achieved high recoveries of over 90% for 10 cycles without any performance decline. Tests with increasing distillate concentrations of ammonium sulfate up to 165,000 mg/L-N could not identify a significant decline in membrane performance either. This allows for concentration up to crystallization in a single stage.

09 BIOMASS FUELS↗

DOE OSTI2020

Deacetylation and Mechanical Refining (DMR) and Deacetylation and Dilute Acid (DDA) Pretreatment of Corn Stover, Switchgrass, and a 50/50 Corn Stover/Switchgrass Blend

The most economical feedstock available to future lignocellulosic biorefineries may be a feedstock blend. Corn stover, switchgrass, and a 50:50 blend of corn stover and switchgrass were subjected to three different dilute alkali deacetylation conditions in a 90 L reactor prior to either mechanical refining (DMR) in a disc refiner followed by a Szego mill or dilute acid pretreatment (DDA) at five different conditions in a 4 L batch steam explosion reactor. The forty-five DDA and nine DMR slurries were subjected to high solids enzymatic hydrolysis at an enzyme loading of 15 mg protein per gram cellulose using Novozymes Cellic CTec3 (DDA) or a 4:1 mix of Novozymes Cellic CTec3:HTec 3 (DMR). The highest glucose yield was achieved using DMR processed corn stover from the high severity deacetylation condition (92 °C and 100 kg NaOH/ODMT) at 95.9% ± 0.8%, while the greatest monomeric glucose yields for switchgrass were between 75% to 80%. The glucose yields from saccharification of the 50:50 corn stover/switchgrass blend was approximately the average of the two individual feedstocks for both DDA and DMR processes. Statistical analysis showed that for a given feedstock type dilute alkali deacetylation severity had a significant impact (p < 0.05) on enzymatic hydrolysis yields, and for a given deacetylation severity the feedstock type had a significant effect on glucose conversion with the addition of switchgrass resulting in lower glucose yields. A blending strategy to maximize enzymatic hydrolysis sugar yields while reducing carbohydrate solubilization during the alkaline treatment step was proposed that allows deacetylation of feedstocks with different recalcitrance at optimal conditions for that feedstock, then blending prior to enzymatic hydrolysis.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗

DOE OSTI2024

Recovery of p -Hydroxybenzoic Acid from Cu-Catalyzed Alkaline Hydrogen Peroxide Pretreatment of Hybrid Poplar

p-Hydroxybenzoic acid (pHBA) is present in some hardwood biomass feedstocks as an ester attached to the polymeric lignin subunits. Here, we report the isolation and recovery of pHBA from alkaline liquor waste streams obtained from fractionation of hybrid poplar using the “Cu-AHP process”. This process features two stages: alkaline pre-extraction (AP) of the biomass and copper-catalyzed alkaline hydrogen peroxide pretreatment. On a biomass scale of 100 g, 0.5 g of pHBA with a purity of 96% was obtained after decolorization and crystallization. The scalability of the purification process was demonstrated by using liquor obtained from the first-stage AP with 900 g of poplar biomass to afford 3.5 g of crystalline pHBA with 97% purity. Altogether, these results show that pHBA may be isolated and purified from waste streams generated in the two-stage Cu-AHP process without any alteration of the process conditions or impact on carbohydrate and lignin fractionation.

09 BIOMASS FUELS↗

DOE OSTI2024

Multiscale investigation of the mechanism of biomass deconstruction in the dimethyl isosorbide/water Co-solvent pretreatment system

In the context of promoting a circular bioeconomy, the development of green and efficient lignocellulosic biomass pretreatment technologies so as to realize high value-added biomass utilization is of intense interest. We demonstrated the potential of the bio-based green solvent dimethyl isosorbide (DMI) for the fractionation of Eucalyptus biomass with excellent performance. Here, to investigate the mechanisms involved in biomass fractionation, microimaging and microspectroscopic techniques were employed together with molecular dynamics (MD) simulation and COSMO-RS quantum chemical calculations to derive multiscale information. Both the microstructure and regional chemistry of the cell wall vary significantly with the volume ratio of DMI/H 2 O. The strongest effects were found at DMI/H 2 O = 9:1 and showed visible cell wall tearing cracks and cell wall deformation and collapse as well as the lowest values of cell wall thickness and circularity. From the MD simulations, lignin exhibits collapsed-like structure in pure H 2 O with low solvent accessibility surface area (SASA) and radius of gyration (R g ). In contrast, lignin in DMI/H 2 O shows extended structure with high SASA and solvent interactions dominated by van der Waals forces, with maximal contact in the 9:1 (v/v) system. Further, the COSMO-RS calculated sigma (σ-) potential suggests the intermolecular interactions in DMI and DMI/H 2 O co-solvent are weak, leading to stronger interaction with lignin and correspondingly higher lignin dissolution. The radial distribution functions and σ-potential all show that again DMI/H 2 O at 9:1 is an optimal volume ratio for high lignin dissolution. Finally, this study provides a solvent-ratio dependent mechanism for the action of polar aprotic solvents in the deconstruction of biomass.

09 BIOMASS FUELS↗

DOE OSTI2022

Comparing Calibration Algorithms for the Rapid Characterization of Pretreated Corn Stover Using Near-Infrared Spectroscopy

Rapid characterization of biomass composition is a key enabling technology for biorefineries—the ability to measure the chemical composition of biomass materials entering the biorefinery as well as the composition of key process intermediate streams would allow real-time process control and the development of robust models to predict process performance. The utility of near-infrared (NIR) spectroscopy for rapid characterization requires multivariate algorithms for building calibration models. The most prevalent algorithm used for building calibration models using NIR spectra is the linear modeling algorithm Partial Least Squares Regression (PLS). Nonlinear regression algorithms (which are typically more computationally intensive than linear modeling approaches) have gained popularity in recent years due to their ability to solve a wide variety of classification and regression problems and the dramatic increase in available computational resources. In this work, we demonstrate that a calibration model can predict the composition of corn stover process intermediate samples pretreated with three different treatments—hot water (HW), dilute acid (DA), and deacetylation followed by dilute acid (DDA). We quantitatively compare three different algorithms for building prediction models based on near-infrared spectroscopy—partial least squares (PLS), support vector machines (SVM), and random forests (RF). We demonstrate the utility of improving model performance by accounting for instrument performance variability using repeated measurements of standard materials (e.g., the “repeatability file” strategy) and investigate its performance with nonlinear regression techniques, and we discuss methods for quantifying the uncertainties of specific predictions among the three methods.

09 BIOMASS FUELS↗