19 research outputs found
Corresponding Author's Institution: Yakama Nation
No full textAbstract: Local and landscape environmental attributes have been strongly linked to community and population patterns. While landscape context appears to be complementary to local characteristics, the relative importance of local and landscape scales varies according to taxonomic groups. We examined the relative influence of both local and landscape factors on butterfly communities in montane meadows of northeastern California. The strongest patterns in the community were related to three variables. Total butterfly richness and abundance was negatively related to a single landscape variable, the cover of big sagebrush vegetation in the matrix surrounding meadows. The species richness and abundance of meadow specialist butterflies, and the abundance of a single meadow specialist species, Plebejus podarce, was positively related to a single local variable, the cover of obligate wetland plants within meadows. The abundance of Speyeria mormonia and Colias eurytheme, and the abundance of Coenonympha tullia ssp. ampelos and Satyrium behrii were respectively, positively and negatively related to elevation. Local factors explained more o
Early egg traits in Cancer setosus (Decapoda, Brachyura): effects of temperature and female size
No full textPrevious study on Cancer setosus (Molina, 1782) had shown that latitudinal changes in temperature control the number of annual egg masses. This study focused on the effects of pre-oviposition temperature and female size on egg-traits in C. setosus from Northern (Antofagasta 23ºS) and Central-Southern (Puerto Montt 41ºS) Chile. Blastula eggs produced in nature ranged in dry mass (DM) from 9.1 to 15.1 µg, in carbon (C) from 4.8 to 8.4 µg, in nitrogen (N) from 1.0 to 1.6 µg, in C:N ratio between 4.7 and 5.4, and in volume (V) between 152 and 276 mm3 x 10-4 per female. Blastula eggs from females caught early in the reproductive season in Puerto Montt (09/2006) were significantly higher in DM, C, N, and V than those of females caught two months later (11/2006), reflecting a seasonal increase in water temperature. In Puerto Montt “early” and “late” season blastula eggs were about 32% and 20% higher in DM, C, N, and V as eggs from Antofagasta, respectively. Subsequent egg masses produced in captivity in Puerto Montt followed this pattern of smaller eggs with lower DM, C, and N content at higher pre-oviposition temperatures. In Antofagasta no significant difference in DM, C, N and V between eggs produced in nature and subsequent eggs produced in captivity was found and all egg traits were significantly positively affected by maternal size. Reproductive plasticity in C. setosus helps explaining the species wide latitudinal distribution range
Hydrothermal liquefaction of microalgae: Influence of varying cell compositions on biocrude yield and quality
No full textThere is strong interest in microalgae-derived biofuel as a sustainable replacement for fossil fuels due to the numerous advantages of microalgae as a feedstock. Hydrothermal Liquefaction (HTL) is a thermochemical process that uses water as the reaction medium to convert biomass into biocrude oil under elevated temperatures and pressures (200–350°C, 5–20 MPa). While there is extensive literature on the separate processes of microalgae cultivation and HTL conversion, relationships between different biochemical compositions of a single species and HTL which contribute to the understanding of the overall system remain unexplored. This study examines the influence of varying microalgae cell composition on HTL biocrude yield and chemical composition. Nannochloropsis oculata was cultivated under depleting nitrogen levels to obtain biomass with variable cell compositions (17–59 %dw lipids; 45–17 %dw proteins; 11–22 %dw carbohydrates). HTL of harvested biomass was conducted at commonly used process conditions (80 wt% moisture, 300°C, 30 min reaction time), and conversion products were characterized to evaluate the energy yield and chemical characteristic of the biocrude phase. Results suggest for the case of lipid-accumulating biomass that biocrude yield is strongly determined by the increasing fatty acid methyl ester (FAMEs) content and not gross lipid content as previously thought. A model linking biomass composition to HTL biocrude yield is proposed based on the contributions from a baseline (non-FAMEs) fraction and FAMEs fraction of the biomass. Biocrude yields and higher heating values (HHV, MJ/kg) both increase with increasing FAMEs content, leading to higher energy recovery within the biocrude product phase. Increasing FAMEs content also leads to biocrude products with an increasing fraction of compounds with boiling points between 300–400°C, decreasing nitrogen content, and decreasing average molecular weight distribution. Results from this study contribute to the understanding of the interrelationships between biomass feedstock composition and the conversion products resulting from HTL. This information can be further linked to separate models for controlling biomass composition during upstream cultivation to enable more integrated analysis of the overall algal-HTL biofuel pathway.Item withdrawn by Laura Spradlin ([email protected]) on 2014-04-28T14:25:33Z
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REMOVED: Practical Applications of Ion-exchange Membranes and Recent Developments
No full textThis article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been removed at the request of the Executive Publisher.This article has been removed because it was published without the permission of the author(s)
Deactivation and regeneration of immobilized titanium dioxide photocatalysts during treatment of pharmaceutical micropollutants in groundwater
No full textAs detection methods improve, a number of classes of emerging contaminants are being detected in natural waters, including many pharmaceuticals and personal care products (PPCPs). Many of these chemicals are recalcitrant to conventional treatment processes, so new treatment methods are being investigated. Titanium dioxide (TiO2)-based photocatalytic treatment has proven to be an effective method for degrading trace organic contaminants, including PPCPs. However, most studies on photocatalytic treatment of PPCPs to date have been conducted in short-term batch experiments using fresh catalysts in laboratory solutions devoid of non-target constituents that are often abundant in natural water matrices (e.g., Ca2+, HCO3-, natural organic matter). In this contribution, we describe the results of an investigation of the long-term stability and deactivation of immobilized TiO2 photocatalysts used to treat PPCPs in groundwater (GW). GW spiked with four model PPCPs (5 µg/L atenolol, sulfamethoxazole, carbamazepine, and 10 µg/L iopromide) was treated with immobilized thin films of TiO2 coated on glass slides under UV-A light in a serpentine plug-flow reactor. Initially, catalysts achieved 50-75% degradation of influent PPCPs using a 2-hr reactor residence time (higher removal can be achieved using longer residence times). Over one month of continuous operation, catalyst films developed visual discoloration and the extent of PPCP removal in the reactor diminished, eventually reaching complete catalyst deactivation for some of the target PPCPs. Calcite (CaCO3(s)) with smaller quantities of iron and copper were detected on the surface of deactivated catalyst films when analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Treatment of deactivated catalysts with 10 mM hydrochloric acid was able to restore catalyst activity to pre-GW levels, so introduction of recurrent acid washing stages during GW treatment were investigated to prolong catalyst activity. Pretreatment of GW using a sodium-loaded cation exchange softening resins was investigated to eliminate calcite precipitation in the reactor. Although calcite precipitation was eliminated, catalysts continued to experience a similar loss of activity observed for unsoftened GW. Analysis of catalyst surfaces after exposure to softened groundwater indicates deposits of zinc, copper, iron, and manganese. Results suggest that both physical blocking of active sites by calcite surface precipitates and adsorption of trace metals contribute to catalyst deactivation. Further work is needed to investigate other pretreatment methods such as pH modification to prevent surface deposition of catalyst-deactivating metal species on the TiO2 surface and prolong reactor activity between acid washing regeneration stages.Item withdrawn by Laura Spradlin ([email protected]) on 2014-07-21T17:57:57Z
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Salammbô as Femme Fatale
No full textUsodna ženska je motiv, ki je postal popularen v umetnosti in literaturi 19. stoletja, čeprav so se
tovrstni ženski liki pojavljali že vse od antike, razlog pa so bile v veliki meri družbene spremembe,
ki so najbolj zamajale temelje takratne meščanske družbe. Usodne ženske so najbolj prepoznavne
po svoji zapeljivi naravi, obscenem obnašanju ter pogubljanju moških. Taka je tudi kartažanska
svečenica Salammbô – literarna junakinja francoskega pisatelja Gustava Flauberta.
Salammbô je svoje mesto našla tudi v slikarski umetnosti, kjer je številne slikarje – kot so med
drugimi Jules Jean Baptiste Toulot, Gabriel Ferrier, Carl Strathmann, Alfons Mucha in Gaston
Bussière – privlačil predvsem njen odnos z ljubljenčkom pitonom. Dotični prizor v romanu sicer ne
igra pomembnejše vloge, intimna bližina med žensko in kačo pa je bila za umetnost tega obdobja
zelo zanimiva, kar se kaže tudi v drugih delih, ki upodabljajo usodne ženske s kačami.Femme fatale is a character that has been known from antiquity, however, it only become popular in
art and literature of fin-de-siècle. The main reason for popularity in 19th century were changes in
society that principally shook the foundation of bourgeoisie. Femme fatale is best known for her
flirtatious nature, salacious behavior, and condemning men. The same can also be said for the
Priestess of Carthage by the name of Salammbô – a heroine from the novel by French author
Gustave Flaubert.
Salammbô had found her place in visual art as well. Many painters such as Jules Jean Baptiste
Toulot, Gabriel Ferrier, Carl Strathmann, Alfons Mucha, and Gaston Bussière among others, were
charmed by her intimate relationship with her pet python. The scene from the novel that inspired
artists doesn’t have high significance for the plot. However, the closeness between the woman and
the snake was very alluring for portraying. This can be seen in many art works from this era, which
also depict women with snakes
Conversion of waste organic carbon and nutrient streams to renewable fuels through integrated biological funneling and catalytic hydrothermal upgrading
No full textIncreasing societal energy demands linked to growing wastewater generation and treatment costs have led to a growing impetus for wastewater treatment plants to transition into renewable resource production facilities or biorefineries, which aim to valorize the organic carbon and nutrients found in wastewater streams into valuable renewable products such as transportation-ready fuels or platform chemicals. Towards this vision, continued development of advanced methods for microbiological carbon accumulation and nutrient capture coupled with aqueous catalytic upgrading of the resultant biomass storage products presents two promising methods of advanced wastewater valorization: (i) conversion of microalgae biomass (which can be cultivated in wastewater effluent) into renewable fuel blendstocks through aqueous processing methods; and (ii) a proposed integrated process utilizing the biological polymer polyhydroxybutyrate (PHB; a storage product of mixed cultures selected from activated sludge) as feedstock to produce gasoline-grade liquid hydrocarbons.
The goal of this thesis is to advance the overall understanding of technological pathways for the production of liquid hydrocarbon fuel blendstocks from wastewater organic carbon and effluent nutrient streams by addressing critical barriers associated with either pathway using multi-disciplinary experimental and modeling approaches, thereby contributing towards the realization of the wastewater biorefinery concept. The following research objectives were pursued towards this goal: (i) develop quantitative predictive models for microalgae hydrothermal liquefaction (HTL) processing, including an improved component additivity model and a new predictive model formulation that can be more easily applied to diverse microalgae species and HTL conditions; (ii) develop a unified techno-economic analysis (TEA) modeling framework for integrated microalgae biofuel systems to understand the influence of varying biomass compositions for varying downstream aqueous processing pathways; (iii) prioritize research and development pathways for microalgae biofuel systems by identifying key system variables through sensitivity and uncertainty analysis based on the unified modeling framework; and (iv) evaluate vapor-phase continuous-flow catalysis for dehydration-decarboxylation of 3-hydroxybutyric acid (3HB; from the depolymerization product of PHB) to produce propylene, with a focus on Brønsted-Lewis acidity of amorphous silica-alumina (ASAs) heterogeneous catalysts and longer-term time-on-stream experiments to explore catalyst deactivation mechanisms.
The first research objective was addressed by developing predictive relationships for HTL biocrude yield and other conversion product characteristics based on HTL of Nannochloropsis oculata batches harvested with a wide range of compositions and a defatted batch. A component additivity model (predicting biocrude yield from lipid, protein, and carbohydrate cell composition) was more accurate predicting literature yields for diverse microalgae species than previous additivity models derived from model compounds. Fatty acid (FA) profiling of the biocrude product showed strong links to the initial feedstock FA profile of the lipid component, demonstrating that HTL acts as a water-based extraction process for FAs; the remainder non-FA structural components could be represented using the defatted batch. These findings were used to introduce a new FA-based model that predicts biocrude oil yields along with other critical parameters, and is capable of adjusting for the wide variations in HTL methodology and microalgae species through the defatted batch. The FA model was linked to an upstream cultivation model (Phototrophic Process Model), providing the basis for an integrated modeling framework to perform predictive analysis of the overall microalgal-to-biofuel process.
Building off results and findings from work addressing the first objective, the second and third research objectives were addressed by integrating a dynamic biological cultivation model with thermo-chemical/biological unit process models for downstream biorefineries to increase modeling fidelity, to provide mechanistic links among unit operations, and to quantify minimum product selling prices of biofuels via techno-economic analysis. The unified modeling framework showed that cultivating biomass compositions to achieve the minimum biomass selling price or to maximize lipid content led to sub-optimal total fuel production costs. Furthermore, depending on biomass composition, both hydrothermal liquefaction (a whole-biomass conversion process) and a biochemical fractionation process were shown to have advantageous minimum product selling prices, which supports continued investment in multiple conversion pathways. Based on these results as well as data from sensitivity analysis, specific recommendations were made for the prioritization of research and development pathways to achieve economical biofuel production from microalgae, including a need to reduce uncertainty surrounding conversion parameters of individual compounds, which can be achieved by expanding the library of compositions and microalgae species used for model calibration and validation while also developing predictions for biocrude oil and product quality. Transitioning away from smaller-scale experimental samples towards pilot-scale or continuous-flow demonstrations, especially for microalgae biomass cultivation, would also provide higher fidelity prediction models for integrated system design.
The final research objective was addressed by evaluating a novel catalytic pathway for conversion of 3HB into propylene through aqueous vapor-phase dehydration-decarboxylation (DHYD-DCBX) over ASAs using a continuous flow reactor. Experiments focused on examining the influence of varying Brønsted-Lewis acidities of ASAs on conversion and product selectivity, as well as longer-term time-on-stream stability under steam (vapor-phase) conditions. Complete conversion of 3HB was observed with propylene yields between 50–55 %C for SiAl 3113 during initial time-on-stream (6 h) testing, but yields decreased to 40 %C after 70 h with no indication of stabilized performance. Recalcination of spent catalyst did not restore activity, and results from artificially steam-treated SiAl 3113 (i.e., 3HB absent) suggest deactivation due to long-term steam exposure, with reductions in surface area and pore volumes observed similar to the spent catalyst used to process 3HB. Propylene selectivity observed with different ASAs appeared to track with reported Brønsted acidities. In addition, Na+ blocking of Brønsted acid sites inhibited conversion to propylene, supporting the important role of Brønsted acidity in catalyzing DHYD-DCBX of 3HB over ASAs.
Overall, this thesis has addressed a number of critical barriers towards the production of renewable biofuels from wastewater organic carbon and nutrients, and in doing so has advanced the general science regarding integrated conversion of microalgal or microbial biomass to valuable products. Contributions from this thesis, in combination with opportunities for further work to expand upon the development of microalgae biofuels and renewable fuel production from waste-derived PHB/3HB as described in this thesis, will undoubtedly continue to push the envelope on wastewater energy recovery technologies.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01The student, Shijie Leow, accepted the attached license on 2018-09-10 at 12:45.The student, Shijie Leow, submitted this Dissertation for approval on 2018-09-10 at 12:56.This Dissertation was approved for publication on 2018-09-11 at 10:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #13004 on 2019-02-08 at 11:37:52Made available in DSpace on 2019-02-08T18:39:40Z (GMT). No. of bitstreams: 2
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Photochemical processes in engineered aquatic systems for remediation of per- and polyfluoroalkyl substances and algae cultivation
No full textPhotochemical processes drive many important reactions in environmental engineering applications, ranging from engineered treatment processes (e.g., micropollutant removal) to natural biogeochemical processes (e.g., nutrient cycling). This thesis investigates (1) the application of a UV-sulfite photochemical treatment process for per- and polyfluoroalkyl substances (PFASs) destruction, and (2) the generation of photochemically produced reactive species in algal cultivation systems where cells excrete light-absorbing extracellular substances.
The production of highly reductive hydrated electrons (eaq−; NHE = −2.9 V) in UV-sulfite treatment has shown promise in the destruction of PFASs. PFASs are a component in aqueous film-forming foam (AFFF) used in fire-training activities and have caused widespread contamination across the U.S. While recent studies have shown promise in UV-sulfite treatment of individual PFASs, little is known of treatment in PFAS mixtures found in AFFF-impacted waters. This thesis investigates the application of UV-sulfite treatment in the complex PFAS mixtures present in dilute solutions of AFFF concentrate and AFFF-impacted groundwaters. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) methods allowed for simultaneous analysis of a wide array of PFASs, including compounds for which no reference standards are available, and yielded valuable kinetic information used to establish structure-reactivity relationships. Results show that reactivity varies widely among the 15 PFASs detected by targeted analysis. While some structures, (e.g., long-chain perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs)) were readily degraded, other structures (e.g., short-chain PFSAs and fluorotelomer sulfonic acids (FTSs)) were more recalcitrant. Furthermore, results show that PFSAs, PFCAs, and FTSs can form as transient intermediates or unreactive end-products by reactions between eaq− and precursors in AFFF. Seventy-three additional PFASs were detected by suspect screening analysis. Among identified structures, sulfonamide precursors and precursors of FTSs and fluorotelomer carboxylic acids (FTCAs) were the most reactive, indicating that these may be the sources of PFSA, PFCA, and FTS generation observed early on in UV-sulfite reactions that was reported previously. While most PFSAs showed few reactivity differences among groundwaters, PFSA reactivity was enhanced in groundwaters compared to single-solute experiments conducted in laboratory buffer solutions at similar pH conditions. In contrast, PFCA reactivity varied in different groundwaters and decreased in reactivity compared to single-solute experiments. Conclusions from this work help develop UV-sulfite into a viable treatment technology and provide insight into treatment in environmentally relevant remediation scenarios.
This thesis also investigates reactive species production in algal cultivation systems where previous research has primarily focused on biofuel production and nutrient recovery. Extracellular organic matter (EOM) and growth medium in the extracellular matrix of an algal cultivation system photoproduced excited triplet state dissolved organic matter (3DOM*), hydroxyl radicals (HO•), and singlet oxygen (1O2). Comparisons with Suwannee River natural organic matter (SRNOM) showed that EOM solutions exhibited lower light absorption and reactive species production than SRNOM solutions per mg-C·L−1. However, 3DOM* quantum yield coefficients, HO• apparent quantum yields, and 1O2 apparent quantum yields in EOM solutions could be greater than or comparable to SRNOM solutions depending on algal growth phase. EOM solutions also photoproduced reactive species at levels comparable to natural waters. Conclusions from this work reveal potential opportunities for developing versatile algal technologies that combine contaminant abatement, bioenergy production, and nutrient recovery.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Raul Tenorio, accepted the attached license on 2020-11-06 at 13:45.The student, Raul Tenorio, submitted this Dissertation for approval on 2020-11-06 at 13:56.This Dissertation was approved for publication on 2020-11-09 at 09:46.DSpace SAF Submission Ingestion Package generated from Vireo submission #15863 on 2021-03-04 at 16:30:42Made available in DSpace on 2021-03-05T21:45:15Z (GMT). No. of bitstreams: 2
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Development of a sustainable water treatment technology for oxyanions using palladium-based catalysts: catalyst design, reaction mechanisms, and life cycle assessment
No full textPerchlorate and nitrate are oxyanion contaminants found in many drinking water sources, causing human health risks when consumed even at low concentrations. These oxyanions are not removed via conventional drinking water treatment processes, and require specialized treatment. One emerging technology for destroying oxyanion water contaminants is catalytic reduction using supported Pd-based catalysts and an electron donor. While the technology is promising, several challenges need to be addressed before it is adapted by water treatment utilities.
The overall goal of my thesis is to contribute to the development of catalytic treatment processes for removing oxyanion contaminants, specifically perchlorate and nitrate, from drinking water, either as a stand-alone system or in combination with ion exchange (IX), and to compare the overall costs and environmental sustainability of the technology with other available oxyanion treatment technologies. My thesis work specifically contributed to three areas of study: 1) elucidation of perchlorate reduction mechanisms using X-ray spectroscopic characterization to identify the chemical states and coordination of Re species in carbon supported Re-Pd catalysts (Re-Pd/C), 2) comparative assessment of environmental sustainability of the catalytic treatment technology with alternative perchlorate treatment technologies such as IX and biological reduction, and 3) evaluation of the applicability and environmental benefits of recycling spent IX brines via catalytic reduction using pelletized carbon supported Pd-In catalysts for removal of nitrate in drinking water. Results from the 1st study showed that Re in Re-Pd/C catalyst exists as ReVII species under oxic conditions and transforms to a mixture of two Re species under reducing solution conditions induced by H2 sparging. These Re species support a revised mechanism for catalytic reduction of perchlorate involving a series of oxygen atom transfer reactions between rhenium species and perchlorate. Results from the 2nd study showed catalytic treatment using Re-
ii
Pd/C catalyst has a higher (ca. 4,600 times) environmental impact than other perchlorate treatment technologies, but is within 0.9-30 times the impact of IX with a newly developed ligand-complexed Re-Pd catalyst suggesting catalytic reduction can be competitive with increased activity. Results from the 3rd study indicated the hybrid IX/catalyst system is more environmentally sustainable than the conventional IX for nitrate removal in drinking water, but the environmental impacts of the system are sensitive to brine conditions (e.g., presence of sulfate and bicarbonate) that influence catalyst activity. Overall, catalytic treatment technology showed the promise as an environmentally sustainable oxyanion treatment technology option for drinking water.Item withdrawn by Laura Spradlin ([email protected]) on 2013-11-04T15:03:21Z
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Integrated catalysis for upgrading microbial derived carboxylic acids to renewable fuels and value-added chemicals
No full textMade available in DSpace on 2016-03-02T20:57:09Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-09-09Embargo set by: Seth Robbins for item 91368
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Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 91368 on 2018-03-03T10:15:14Z.In order to transition to a renewable carbon society, economically and environmentally sustainable technologies are needed to displace our dependence on petroleum. Carboxylic acids are a diverse class of biological metabolites that can be converted to renewable fuels and chemicals to offset our consumption of petroleum. However, significant challenges occur when integrating catalysis with biological processes, which include: (1) biological conversion produces carboxylic acids at relatively dilute levels (<20 wt%) in broth that can contain residual impurities, creating separation and downstream process challenges, (2) microbial acids can contain unique chemical moieties (e.g., polyunsaturated bonds, hydroxyl groups, ester linkages) compared to aliphatic petroleum, requiring tailored catalytic upgrading strategies to produce fuels and chemicals, and (3) carboxylic acid valorization can occur through a multitude of unit process schemes, necessitating early-stage techno-economic analysis to identify key bottlenecks for further development. To address these challenges, this thesis investigates integrated catalysis for upgrading microbial derived acids to renewable fuels and value-added chemicals.
To target both renewable fuels and value-added chemicals from microbial acids, the following research objectives were pursued: (1) hydrothermal catalysis was investigated for deoxygenating monocarboxylic acids to diesel-grade hydrocarbons with in situ hydrogen production from renewable organic donors, (2) separation and catalysis was examined for recovering and cis,cis-muconic acid from culture broth and converting it to adipic acid, the latter compound being a high-value polymer precursor for nylon-6,6 production, and (3) key economic drivers and technical targets were identified for the downstream processing of muconic acid to adipic acid using preliminary techno-economic analysis.
Initially, hydrothermal catalysis was investigated for converting long chain saturated and unsaturated carboxylic acids to hydrocarbon fuels using a Pt-Re catalyst supported on activated carbon (AC). The addition of Re as a secondary metal was shown to enhance the rate of carboxylic acid deoxygenation and modify the chemisorption behavior of Pt, suggesting alloy formation. Decarboxylation/decarbonylation of the carboxylate group was observed as the primary reaction pathway, and characterization of the Pt-Re/AC catalyst by x-ray photoelectron spectroscopy determined that hydrogen in the headspace resulted in a reduced oxidation state of the metals after exposure to hydrothermal conditions. Lastly, the addition of glycerol as an in situ hydrogen donor proved effective at meeting process hydrogen demands through aqueous phase reforming reactions.
The application of the Pt-Re/AC catalyst system was then evaluated using a complex monocarboxylic acid feedstock derived biologically from lignin. The microorganism Pseudomonas putida KT2440 was initially used to biologically “funnel” lignin derived monomers to intracellular medium chain length polyhydroxyalkanoates (mcl-PHAs). Shake flask studies demonstrated that P. putida produces mcl-PHAs from both mixed model compounds and complex lignin derived monomers derived from corn stover. Extraction and characterization of lignin derived mcl-PHAs showed similar physicochemical properties compared to mcl-PHAs produced from clean glucose, and thermal depolymerization readily converted mcl-PHAs to alkenoic acid monomers. Subsequent catalytic processing of alkenoic acids in hydrothermal media with Pt-Re/AC produced linear hydrocarbons, similar to the model compound fatty acid study, demonstrating the integrated biological and catalytic conversion of lignin to hydrocarbon fuel.
In order to target value-added chemicals from microbial acids, the downstream separation and catalytic upgrading of cis,cis-muconic was evaluated for the production of adipic acid, the latter molecule being a high-value polymer precursor for nylon-6,6 production. Expanding on previous work, a metabolically engineered strain of P. putida KT2440 was used to produce muconic acid extracellularly from both model and lignin derived monomers. Following fed-batch biological conversion of p-coumaric acid, activated carbon purification was shown to effectively remove broth non-target upstream metabolites, color compounds, and unconverted substrate. Muconic acid was then recovered from culture broth by pH/temperature shift crystallization in high purity (>97%) and yield. Catalyst batch screening studies of commercial Pd, Pt, Ru identified Pd as a highly active metal for muconic acid hydrogenation, although leaching was observed.
As a follow-up, the downstream separation and catalysis of muconic acid was further examined to improve the separation purity, evaluate catalyst stability, and demonstrate bio-adipic acid polymerization to nylon-6,6. Following crystallization, dissolution of muconic acid crystals in ethanol with membrane filtration removed insoluble inorganic salts, producing muconic acid at 99.8% purity. In house catalysts were synthesized on both carbon and silica supports and tested in batch hydrogenation screening reactions. Pd and Rh were identified as highly active on both carbon and silica supports when compared to Ru and Pt, although Pd leached significantly, with a greater extent on silica. To further evaluate the stability of Rh/AC, continuous trickle bed hydrogenation demonstrated steady state partial conversion for 48 h, followed by complete conversion until 96 h, with a return to partial steady state conversion for 120 h of time on stream. Characterization of the post reaction Rh/AC catalyst showed a modest increase in support surface area and pore volume, moderate loss in active metal surface area, and minor increase in metal crystallite size. Bio-adipic acid derived catalytically from muconic acid was then polymerized to nylon-6,6, and characterization of the polymer confirmed properties comparable to nylon produced from adipic acid of petrochemical origin.
Lastly, preliminary techno-economic analysis was conducted to evaluate key economic drivers and technical targets for the downstream processing of muconic acid to adipic acid. An nth-generation downstream plant was modeled to produce 75 million kg of adipic acid per year. For the base-case process model, the following technical parameters were employed: cell free culture broth containing 50 g/L muconate and 2 g/L of non-target aromatic compounds was purified continuously with activated carbon. Muconic acid was then recovered by pH/temperature shift crystallization, dissolved in ethanol, and filtered to provide a condensed phase for catalytic processing. Muconic acid in ethanol was catalytically converted to adipic acid over a packed bed reactor containing 2%Rh/AC, and a second train of evaporative crystallization with rotary filtration and drying recovered adipic acid as the final product. The largest capital costs for the base case model were activated carbon regeneration kilns and the packed bed hydrogenation reactor. Variable operating costs were comparable throughout, excluding the cost of incoming muconate broth which was the largest variable expense by far. Economic analysis of the base case model determined a minimum selling price of bio-based adipic acid of \$1.90/kg, within the 5-year historical range (\$1.75-2.50/kg) for petroleum derived adipic acid. Lastly, single point sensitivity analysis determined that the broth ratio of muconate to non-target aromatic compounds was a major non-linear cost driver, as well as the required reactor throughput for the 2%Rh/AC catalyst.
Overall, this thesis demonstrated that integrated catalysis can convert both model and complex microbial acids derived from lignocellulosic feedstocks to renewable fuels and value-added chemicals. Upstream biological funneling is uniquely suited to address the heterogeneity of complex biomass monomer streams, while tailored separation schemes have potential to produce carboxylate feedstocks of suitable purity for value-added chemical production. The unique functional moieties of microbial acids will require tuned reaction conditions and catalytic formulations depending when targeting renewable fuels and chemicals, while the challenges of substrate acidity, residual impurities, and potentially harsh reactions conditions will require robust catalyst development.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-12-01The student, Derek Vardon, accepted the attached license on 2015-08-26 at 17:35.The student, Derek Vardon, submitted this Dissertation for approval on 2015-08-26 at 17:41.This Dissertation was approved for publication on 2015-09-09 at 09:03.DSpace SAF Submission Ingestion Package generated from Vireo submission #8657 on 2016-03-02 at 14:11:4
