Engineering topics

Rainbolt, James E.

Publications and source records attributed to Rainbolt, James E..

10 records

DOE OSTI2017

Warm Cleanup of Coal-Derived Syngas: Multicontaminant Removal Process Demonstration

Warm cleanup of coal- or biomass-derived syngas requires sorbent and catalytic beds to protect downstream processes and catalysts from fouling. Sulfur is particularly harmful because even parts-per-million amounts are sufficient to poison downstream synthesis catalysts. Zinc oxide (ZnO) is a conventional sorbent for sulfur removal; however, its operational performance using real gasifier-derived syngas and in an integrated warm cleanup process is not well reported. In this paper, we report the optimal temperature for bulk desulfurization to be 450oC, while removal of sulfur to parts-per-billion levels requires a lower temperature of approximately 350oC. Under these conditions, we found that sulfur in the form of both hydrogen sulfide and carbonyl sulfide could be absorbed equally well using ZnO. For long-term operation, sorbent regeneration is desirable to minimize process costs. Over the course of five sulfidation and regeneration cycles, a ZnO bed lost about a third of its initial sulfur capacity, however sorbent capacity stabilized. Here, we also demonstrate, at the bench-scale, a process and materials used for warm cleanup of coal-derived syngas using five operations: 1) Na2CO3 for HCl removal, 2) regenerable ZnO beds for bulk sulfur removal, 3) a second ZnO bed for trace sulfur removal, 4) a Ni-Cu/C sorbent for multi-contaminant inorganic removal, and 5) a Ir-Ni/MgAl2O4 catalyst employed for ammonia decomposition and tar and light hydrocarbon steam reforming. Syngas cleanup was demonstrated through successful long-term performance of a poison-sensitive, Cu-based, water-gas-shift catalyst placed downstream of the cleanup process train. The tar reformer is an important and necessary operation with this particular gasification system; its inclusion was the difference between deactivating the water-gas catalyst with carbon deposition and successful 100-hour testing using 1 LPM of coal-derived syngas.

Spies, Kurt A.↗

DOE OSTI2016

Thermal Pretreatment of a High Lignin SSF Digester Residue to Increase its Softening Point

Residues high in lignin and ash generated from the simultaneous saccharification and fermentation of corn stover were thermally pretreated in an inert (N2) atmosphere to study the effect of time and temperature on its softening point. These residues are difficult to feed into gasifiers due to premature thermal degradation and formation of reactive liquids in the feed lines, leading to plugging. The untreated and treated residues were characterized by proximate and ultimate analysis, and then analyzed via TGA, DSC, 13C NMR, Py-GC-MS, CHNO/S, and TMA. Interpretation of the compositional analysis indicates that the weight loss observed during pretreatment is mainly due to the thermal decomposition and volatilization of the hemicelluloses and amorphous cellulose fractions. Fixed carbon increases in the pretreated material, mostly due to a concentration effect rather than the formation of new poly-aromatic material. The optimal processing time and temperature to minimize the production of carbonyl groups in the pretreated samples was 300°C at a time of 30 minutes. Results showed that the softening point of the material could be increased from 187°C to 250°C, and that pretreatment temperature plays a more important role than time. The increase in softening point was mainly due to the formation of covalent bonds in the lignin structures and the removal of low molecular weight volatile intermediates.

Gasification, Lignin rich feedstocks, high lignin ↗

DOE OSTI2016

System and process for capture of acid gasses at elevated pressure from gaseous process streams

A system, method, and material that enables the pressure-activated reversible chemical capture of acid gasses such as CO.sub.2 from gas volumes such as streams, flows or any other volume. Once the acid gas is chemically captured, the resulting product typically a zwitterionic salt, can be subjected to a reduced pressure whereupon the resulting product will release the captures acid gas and the capture material will be regenerated. The invention includes this process as well as the materials and systems for carrying out and enabling this process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Hierarchically structured catalysts for cascade and selective steam reforming/hydrodeoxygenation reactions

We report a hierarchically structured catalyst with steam reforming and hydrodeoxygenation functionalities being deposited in the micropores and macropores, respectively. The catalyst is highly efficient to upgrade the pyrolysis vapors of pine forest product residual, resulting in a dramatically decreased acid content and increased hydrocarbon yield without external H2 supply.

Catalysts↗

DOE OSTI2014

Coal-Derived Warm Syngas Purification and CO 2 Capture-Assisted Methane Production

Gasifier-derived syngas from coal has many applications in the area of catalytic transformation to fuels and chemicals. Raw syngas must be treated to remove a number of impurities that would otherwise poison the synthesis catalysts. Inorganic impurities include alkali salts, chloride, sulfur compounds, heavy metals, ammonia, and various P, As, Sb, and Se- containing compounds. Systems comprising multiple sorbent and catalytic beds have been developed for the removal of impurities from gasified coal using a warm cleanup approach. This approach has the potential to be more economic than the currently available acid gas removal (AGR) approaches and improves upon currently available processes that do not provide the level of impurity removal that is required for catalytic synthesis application. Gasification also lends itself much more readily to the capture of CO 2 , important in the regulation and control of greenhouse gas emissions. CO 2 capture material was developed and in this study was demonstrated to assist in methane production from the purified syngas. Simultaneous CO 2 sorption enhances the CO methanation reaction through relaxation of thermodynamic constraint, thus providing economic benefit rather than simply consisting of an add-on cost for carbon capture and release. Molten and pre-molten LiNaKCO 3 can promote MgO and MgO-based double salts to capture CO 2 with high cycling capacity. A stable cycling CO 2 capacity up to 13 mmol/g was demonstrated. This capture material was specifically developed in this study to operate in the same temperature range and therefore integrate effectively with warm gas cleanup and methane synthesis. By combining syngas methanation, water-gas-shift, and CO 2 sorption in a single reactor, single pass yield to methane of 99% was demonstrated at 10 bar and 330°C when using a 20 wt% Ni/MgAl 2 O 4 catalyst and a molten-phase promoted MgO-based sorbent. Under model feed conditions both the sorbent and catalyst exhibited favorable stability after multiple test cycles. The cleanup for warm gas cleanup of inorganics was broken down into three major steps: chloride removal, sulfur removal, and the removal for a multitude of trace metal contaminants. Na 2 CO 3 was found to optimally remove chlorides at an operating temperature of 450ºC. For sulfur removal two regenerable ZnO beds are used for bulk H 2 S removal at 450ºC (<5 ppm S) and a non-regenerable ZnO bed for H 2 S polishing at 300ºC (<40 ppb S). It was also found that sulfur from COS could be adsorbed (to levels below our detection limit of 40 ppb) in the presence of water that leads to no detectable slip of H 2 S. Finally, a sorbent material comprising of Cu and Ni was found to be effective in removing trace metal impurities such as AsH 3 and PH 3 when operating at 300ºC. Proof-of-concept of the integrated cleanup process was demonstrated with gasifier-generated syngas produced at the Western Research Institute using Wyoming Decker Coal. When operating with a ~1 SLPM feed, multiple inorganic contaminant removal sorbents and a tar-reforming bed was able to remove the vast majority of contaminants from the raw syngas. A tar-reforming catalyst was employed due to the production of tars generated from the gasifier used in this particular study. It is envisioned that in a real application a commercial scale gasifier operating at a higher temperature would produce lesser amount of tar. Continuous operation of a poison-sensitive copper-based WGS catalyst located downstream from the cleanup steps resulted in successful demonstration.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2014

CAS-NETL-PNNL CEP Program Final Report

This collaborative joint research project is in the area of advanced gasification and conversion, within the CAS-NETL-PNNL Memorandum of Understanding. The goal is the development and testing of an integrated warm syngas cleanup process. This effort is focused on an advanced, integrated system for capture and removal of alkali, sulfur, PH3, AsH3, chloride, and CO2, leading to a future process demonstration at a CAS gasification facility. Syngas produced by gasification can be used for production of fuels (Fischer-Tropsch, SNG, mixed alcohols), chemicals (MeOH, NH3), and hydrogen for fuel cells and IGCC. To employ this syngas, especially for synthesis reactions, contained impurities must be removed to sub-ppmv levels [1]. Commercially available approaches to remove contaminant species suffer from inefficiencies, employing solvents at ambient or lower temperature along with backup sacrificial sorbents, whereas syngas utilization occurs at higher temperatures. The efficiency and economics syngas utilization can be significantly improved if all the contaminants and CO2 are removed at temperatures higher than the chemical synthesis reaction temperatures (> 250 °C) [2].

alkali↗

DOE OSTI2013

Progress toward Biomass and Coal-Derived Syngas Warm Cleanup: Proof-of-Concept Process Demonstration of Multicontaminant Removal for Biomass Application

Systems comprising of multiple sorbent and catalytic beds have been developed for the warm syngas cleanup of coal- and biomass-derived syngas. Tailored specifically for biomass application the process described here consists of six primary unit operations: 1) Na2CO3 bed for HCl removal, 2) two regenerable ZnO beds for bulk H2S removal, 3) ZnO bed for H2S polishing, 4) NiCu/SBA-16 sorbent for trace metal (e.g. AsH3) removal, 5) steam reforming catalyst bed for tars and light hydrocarbons reformation and NH3 decomposition, and a 6) Cu-based LT-WGS catalyst bed. Simulated biomass-derived syngas containing a multitude of inorganic contaminants (H2S, AsH3, HCl, and NH3) and hydrocarbon additives (methane, ethylene, benzene, and naphthalene) was used to demonstrate process effectiveness. The efficiency of the process was demonstrated for a period of 175 hours, during which no signs of deactivation were observed. Post-run analysis revealed small levels of sulfur slipped through the sorbent bed train to the two downstream catalytic beds. Future improvements could be made to the trace metal polishing sorbent to ensure complete inorganic contaminant removal (to low ppb level) prior to the catalytic steps. However, dual, regenerating ZnO beds were effective for continuous removal for the vast majority of the sulfur present in the feed gas. The process was effective for complete AsH3 and HCl removal. The steam reforming catalyst completely reformed all the hydrocarbons present in the feed (methane, ethylene, benzene, and naphthalene) to additional syngas. However, post-run evaluation, under kinetically-controlled conditions, indicates deactivation of the steam reforming catalyst. Spent material characterization suggests this is attributed, in part, to coke formation, likely due to the presence of benzene and/or naphthalene in the feed. Future adaptation of this technology may require dual, regenerable steam reformers. The process and materials described in this report hold promise for a warm cleanup of a variety of contaminant species within warm syngas.

Environmental Molecular Sciences Laboratory↗

DOE OSTI2013

Substituent effects on the geometric and electronic properties of tetracyano-p-quinodimethane (TCNQ): A theoretical study.

Electron acceptors are classes of molecules that are important in organic devices as they help to improve the conductivity of organic semiconducting molecules by forming p-type complexes or anion radical complexes. These molecules can be doped into hole transporting materials to provide good ohmic contact with the anode and to improve the carrier density of the hole transport layer. This results in organic light emitting devices (OLEDs) with low driving voltages and high power efficiencies. In this study we investigate a series of TCNQ derivatives with substituents expected to facilitate the electron acceptor capabilities of the quinones using density functional theory (DFT) and time-dependent density functional theory (TDDFT). As expected, the cyano substitution stabilizes both HOMO and LUMO energy levels, and increases the adiabatic electron affinity of the dopants. The stabilization effect on the LUMO levels is greater and as a result the narrowing of the HOMO-LUMO gap is seen. This fact was further confirmed by TD-DFT studies, energy of the computed S1 ← S0 transition red shifted upon CN substitution. However, perturbation to the ground state geometry is negligible and all anionic structures exhibits aromatization independent of substitution. Our study suggests that the substituted derivatives reported herein show promise as conductivity dopants

Environmental Molecular Sciences Laboratory↗

DOE OSTI2013

Near independence of OLED operating voltage on transport layer thickness

We report organic light emitting devices (OLEDs) with weak drive voltage dependence on the thickness of the hole transport layer (HTL) for thicknesses up to 1150 Å using the N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD) and N,N'-bis(3-methyl phenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'diamine (TPD), both of which have hole mobilities in the range of 2 × 10-3 cm2V-1s-1. Lower mobility HTL materials show larger operating voltage dependence on thickness. The near independence of the operating voltage for high mobility transport material thickness was only observed when the energy barrier for charge injection into the transport material was minimized. To ensure low injection barriers, a thin film of 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluorotetracyanoquinodimethane (F3TCNQ-Adl) was cast from solution onto the ITO surface. These results indicate that thick transport layers can be integrated into OLED stacks without the need for bulk conductivity doping.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2012

Characterization of solution processed, p-doped films using hole-only devices and organic field-effect transistors

We report a solution-processed approach for a p-type doped hole transport layer in organic light emitting devices (OLEDs). UV-vis-NIR absorption spectra identified the charge transfer between the donor and acceptor in the solution processed doped films. Single carrier device and field-effect transistor were utilized as test vehicles to study the charge transport property and extract important parameters such as bulk mobile carrier concentration and mobility. OLEDs with p-type doped hole transport layer showed significant improvement in power efficiency up to 30% at the optimal doping ratio. This approach has the great potential to reduce the power consumption for OLED solid state lighting while lowering the cost and boosting the throughput of its manufacturing.

Swensen, James S.↗