Browsing by Subject "Biomass"

Now showing 1 - 20 of 23
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    Allometric Equations for Estimation of Ash-free Dry Mass from Length Measurements for Selected European Earthworm Species (Lumbricidae) in the Western Great Lakes Region
    (University of Notre Dame, 2004) Hale, Cindy M; Reich, Peter B; Frelich, Lee E
    In the last decade the invasion of European earthworms into previously worm-free glaciated areas of North America has stimulated research into their impacts on native forest ecosystems in the region. As a first approximation, the impacts of invading earthworms are related to their biomass. However, direct measurements of biomass can be significantly affected by the moisture conditions under which the earthworms are collected and their relative gut contents. Ash-free dry mass is the best standardized measure of earthworm biomass, but requires the destruction of specimens. This paper presents five allometric equations that allow for estimation of ash-free dry biomass based on length (mm) measurements for European earthworm species (Lumbricidae) commonly seen in the United States.
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    Assessing the woody biomass supply chain in the Pacific Northwest and Great Lakes regions: Investigating policy as drivers of change
    (2015-08) Kudrna, Jordan
    With the ever-increasing need for clean and accessible energy sources, woody biomass has long been entertained as a potential prospect. As energy markets and business operations are influenced by political decisions, it is essential to know the relationship between policy impacts on business innovation and investment decisions. This study looks at significant changes woody biomass business owners have implemented over the course of their operations, and how state and federal policies have affected those changes. A survey of 175 woody biomass business owners in the upper Midwest Lake States and Pacific Northwest was conducted in 2014 to gain insight into the bioenergy investment decisions of logging and transport businesses, utility companies, pellet and densified fuel producers, and institutional heat users. Failing to understand policy influence on business innovation risks investment in ineffective strategies and business uncertainty. The results of this study will help arm policy makers and energy professionals with knowledge about how current renewable energy policies are influencing business investment decisions along the wood-energy supply chain in hopes of more effective policy planning and implementation.
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    Autothermal oxidative pyrolysis of biomass feedstocks over noble metal catalysts to liquid products.
    (2011-07) Balonek, Christine Marie
    Two thermal processing technologies have emerged for processing biomass into renewable liquid products: pyrolysis and gasification/Fischer-Tropsch processing. The work presented here will demonstrate oxidative pyrolysis of biomass as an alternative process to avoid the intrinsic disadvantages of traditional pyrolysis. Additionally, work has been conducted to examine the processing of biomass derived synthesis gas to condensable products, which involves mitigating new challenges when compared with the processing of conventional coal-based feedstocks during gasification/Fischer- Tropsch. The research group of Professor Lanny D. Schmidt has pioneered autothermal partial oxidation of a variety of gas and liquid feedstocks on noble metal catalysts to synthesis gas with high selectivity, char-free operation, and on millisecond timescales at temperatures of 600 - 1000 ◦C. More recently, cellulose has been shown to decompose on the catalyst surface to also produce high selectivities to synthesis gas. Chapter 2 discusses the discovery of an intermediate liquid phase during the autothermal processing of cellulose particles over rhodium-based catalysts. Volatilization of 300 μm cellulose particles on a 700 ◦C catalytic surface were filmed using a high speed camera capable of 1000 frames per second. The cellulose particles decomposed through an intermediate liquid, which boiled to gaseous species that convected into the catalyst bed. The high heat transfer rates made possible by the intimate contact of the boiling liquid and the hot surface allowed rapid reactions without leaving char residues. This unique insight allows new processes to be designed that exploit this type of cellulose thermal decomposition. Experiments were conducted to investigate the extension of catalytic partial oxidation over noble metal catalysts to convert biomass to liquid pyrolysis products, termed ‘oxidative pyrolysis’. Model compounds were chosen to represent the lignin fraction of lignocellulosic biomass to more easily and accurately study the proposed system. Chapter 3 discusses the autothermal oxidative pyrolysis of monoaromatics over noble metal catalysts. Benzene, toluene, ethylbenzene, cumene, and styrene were independently studied over five noble metal-based catalysts (Pt, Rh, Rh/ -Al2O3, Rh-Ce, and Rh-Ce/ -Al2O3) while varying the carbon-to-oxygen feed ratio. Aromatic rings were observed to be very stable in the reactor system, while homogeneous reactions of the alkyl groups of ethylbenzene and cumene were prevalent. Chapter 4 addresses the oxidative pyrolysis of microcrystalline cellulose particles as a model for lignocellulosic biomass to yield liquid products. Cellulose was demonstrated to autothermally convert to combustion, partial oxidation, and pyrolysis products without char formation. The effects of support geometry, catalyst metal, and hydrogen addition on product selectivities were studied. Platinum-coated alumina spheres maximized the yield of pyrolysis products by favoring combustion chemistry and minimizing reforming activities, as compared with rhodium-based catalysts. Up to 60 % carbon selectivity to pyrolysis products could be achieved on a Pt catalyst with hydrogen addition. As mentioned, previous research in the Schmidt group has shown high selectivities to synthesis gas by autothermal reforming of cellulose particles. However, utilizing this biomass-derived syngas, as opposed to traditional coal-based syngas, is not well studied. Biomass-derived synthesis gas presents a new set of inorganic impurities that may affect catalyst performance during Fischer-Tropsch processing. Small quantities (ppm) of typical biomass inorganics (Na, K, Li, and Ca) were loaded onto -Al2O3- supported Co-Re powder catalysts to study the effect on product selectivities (Chapter 5). The inorganic impurities were found to affect the reduction of Co and increase CO2 and C5+ selectivities, which were largely attributed to electronic effects. Chapter 6 proposes future research utilizing gas chromatography and mass spectrometry to identify and quantify specific components within liquid pyrolysis products, generally termed ‘pyrolysis oil’. This work will build on the research presented in Chapter 4: the demonstration of oxidative pyrolysis of cellulose to produce up to 50 % carbon selectivity to pyrolysis products. Further characterization of the pyrolysis oil will involve pH and water fraction measurements. Preliminary work shows the presence of several acids, alcohols, phenols, pyrans, among other small oxygenated species in the pyrolysis oil. Levoglucosan was identified as being the largest carbon-based fraction of the oil, up to 11 wt% under certain conditions. Additional experiments extending oxidative pyrolysis to process polymer feedstocks are also proposed
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    Catalytic autothermal reforming of biomass to synthesis gas.
    (2010-07) Colby, Joshua Leigh
    Please see PDF abstract!
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    Catalytic partial oxidation of pyrolysis oils.
    (2009-08) Rennard, David Carl
    Pyrolysis oils, created from biomass by rapid heating in the absence of oxygen, are a promising intermediate for renewable fuels. Catalytic partial oxidation (CPO) can convert pyrolysis oils to synthesis gas, a mixture of CO and H2, which can be subsequently converted to synthetic renewable fuels: Fischer Tropsch alkanes, methanol, dimethyl ether, or H2 for fuel cells. CPO is rapid, with contact times of 10-30 ms, tunable to a select few types of products, and autothermal. The CPO of model compounds of pyrolysis oils, including acids, esters, and polyols is explored over Rh and Pt catalysts. Experiments over Rh achieve near equilibrium production of syngas. Over Pt, non-equilibrium olefins and aldehydes are observed, which give insight into the catalytic and homogeneous chemistry in CPO. Reactive Flash Volatilization (RFV), wherein liquid droplets are sprayed directly onto the catalyst surface, is also explored for both glycerol and three types of pyrolysis oil. A long-term study of RFV of glycerol explores the longevity of the noble metal catalyst in this technique.
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    Catalytic partial oxidation of renewable feedstocks.
    (2012-07) Chakrabarti, Reetam
    The current world energy and economic infrastructure is heavily reliant on fossil fuels such as coal, oil, and natural gas. The limited availability of fossil fuels along with environmental effects and economic uncertainties associated with their use has motivated the need to explore and develop other alternative sources of energy. Lignocellulosic biomass like fossil fuels is carbon-based and has the potential to partly supplant the energy supplied by fossil fuels. Lignocellulosic biomass is a complex mixture of polymers such as cellulose, hemicellulose, lignin along with small concentrations of inorganics and extractives. Recent research has shown that lignocellulosic biomass and biomass model compounds can be processed autothermally by catalytic partial oxidation in millisecond residence times over noble metal catalysts at high temperatures (600-1000 °C) to syngas (a mixture of carbon monoxide and hydrogen) [1-3]. The syngas stream can then be upgraded to fuels and chemicals. In Chapter 2, spatially resolved concentration and temperature profiles of methane and dimethyl ether, a model compound for biomass, are compared. Dimethyl ether can be produced renewably through syngas upgrading. Maximum temperature and concentration gradients were found within the oxidation zone. Most of the oxygen (∼ 95 %) was converted within the first 2.2 mm and syngas formation was observed despite the presence of oxygen. The catalytic partial oxidation process has been demonstrated using compounds which, unlike most biomass sources, contain negligible quantities of inorganics. Some of these inorganics have catalytic properties themselves and some may act as poisons for the Rh-based catalyst. The effects of common biomass-inorganics (silicon, calcium, magnesium, sodium, potassium, phosphorus, sulfur) on rhodium-based catalysts in autothermal reactors have been studied. To understand the effects of biomass inorganics on Rh catalysts, two sets of experiments surveying common inorganics were performed - in the first set, inorganics were directly deposited on the rhodium catalyst and tested using steam methane reforming as a model reaction (Chapter 3); whereas in the second set, inorganics were introduced to a clean catalyst in an ethanol feed to simulate actual inorganic-containing biomass (Chapter 4). In both sets of experiments, performance testing, catalyst characterization and regeneration were carried out to probe the mechanism of inorganic interaction with the rhodium-based catalyst. Large decreases in reforming activity were observed on phosphorus- and sulfur-doped catalysts. Deactivation due to calcium and magnesium was primarily due to blocking of active sites. Potassium and silicon were volatile at the high temperatures within the reactor. Potassium introduced alkaline chemistry promoting acetaldehyde formation from ethanol while phosphorus introduced acid chemistry promoting formation of ethylene from ethanol. The effects of potassium and phosphorus on catalytic partial oxidation of methane and ethanol at different concentrations and temperatures have been studied in Chapter 5. The synergistic effects of potassium and phosphorus were studied by distributing the inorganics together on the catalyst as monobasic potassium phosphate. The effects of both potassium and phosphorus were observed in the catalytic partial oxidation of methane on a potassium phosphate-doped catalyst at low temperatures. At high temperatures, only effects due to phosphorus were observed because of potassium volatilization. The results show that biomass-sources containing low concentrations of inorganics can be processed autothermally to a high selectivity syngas stream. The distribution and interactions of the inorganics within the catalyst can be used to design better pretreatment, processing, and regeneration strategies to minimize catalyst deactivation during biomass processing. Alcohols represent an important intermediate in different biomass upgrading routes. Chapter 6 discusses the behavior of butanol isomers, 1-butanol, isobutanol, 2-butanol, and tert-butanol over four different catalysts; Rh, Pt, RhCe, and PtCe at different fuel to oxygen (C/O) ratios. At low C/O ratios, equilibrium species such as CO, CO2, H2 and H2O were obtained while non-equilibrium species such as carbonyls and olefins were dominant at high C/O ratios. Low reforming activity was observed on Pt and PtCe catalysts. All isomers decompose primarily by dehydrogenation through a carbonyl intermediate except tert-butanol which decomposes by dehydration to isobutene; however, the reactivity of tert-butanol was unaffected. In Chapter 7, isobutanol autothermal reforming is integrated with a water gas shift stage downstream to produce hydrogen containing low concentrations of carbon monoxide for portable fuel cell applications. A RhCe-based catalyst was selected to carry out autothermal reforming of isobutanol while a PtCe catalyst was selected for the water gas shift stage. This staged reactor produced high yields of hydrogen (> 120 % selectivity) containing low concentrations of CO (< 2 mol %) in less than 100 ms making the effluent ideal for portable high temperature PEM fuel cell applications. The water gas shift stage also reduced the concentration of non-equilibrium products formed in the autothermal reforming stage by over 50 %. Thermodynamic analysis of the system showed that staged autothermal reforming of isobutanol integrated with a fuel cell can potentially lead to 2.5 times more efficient energy usage when compared to burning isobutanol in a conventional combustion engine. The results in this thesis give an insight into the mechanisms and processing challenges involved in converting renewable feedstocks to syngas by catalytic partial oxidation. Further experiments based on the conclusions of this thesis are discussed in Chapter 8. Spatial profile experiments to determine roles of mass transfer, steam reforming, and dry reforming during catalytic partial oxidation of oxygenates are proposed. Spatial profile studies for catalytic partial oxidation over inorganic-doped catalysts and feed are proposed to determine their concentrations and nature on the catalyst surface during reactor operation.
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    Data and R code: Towards sustainable maize production in the U.S. upper Midwest with interseeded cover crops
    (2019-07-17) Rusch, Hannah L; Garcia y Garcia, Axel; Coulter, Jeffrey A; Johnson, Gregg A; Grossman, Julie M; Porter, Paul M; axel@umn.edu; Garcia y Garcia, Axel; Sustainable Cropping Systems Lab
    Six cover crop treatments were interseeded into maize at two distinct timings: at the four to six-leaf collar stage and at physiological maturity. The canopy cover and biomass of cover crops, soil moisture at planting maize, and maize biomass and yield were evaluated to determine the potential impacts of interseeded cover crops on maize productivity.
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    Data for Process Design and Economic Analysis of Renewable Isoprene from Biomass via Mesaconic Acid
    (2019-02-13) Dauenhauer, Paul J; Lundberg, Daniel J; Lundberg, David J; hauer@umn.edu; Dauenhauer, Paul J; Dauenhauer Research Laboratory - Chemical Engineering and Materials Science
    The data contain the process design and economic information for the design and optimization of a chemical process to manufacture isoprene from biomass via mesaconic intermediate.
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    Deciphering Biomass Fragmentation using Millisecond Microreactor Kinetics
    (2018-05) Maduskar, Saurabh
    Pyrolytic conversion of lignocellulosic biomass utilizes high temperatures to thermally fragment biopolymers to volatile organic compounds. The complexity of the degradation process includes thousands of reactions through multiple phases occurring in less than a second. The underlying chemistry of lignocellulose decomposition has been studied for decades, and numerous conflicting mechanisms and kinetic models have been proposed. The fundamental science of biomass pyrolysis is still without detailed chemical kinetics and reaction models capable of describing the chemistry and transport in industrial reactors. The primary goal of this thesis was to develop mechanistic insights of biomass pyrolysis with the focus on fragmentation of cellulose using two novel microreactor systems, a. Quantitative Carbon Detector (QCD) b. Pulse Heated Analysis of Solid Reactions (PHASR). Current research of complex chemical systems, including biomass pyrolysis, requires analysis of large analyte mixtures (>100 compounds). Quantification of each carbon-containing analyte by existing methods (flame ionization detection) requires extensive identification and calibration. An integrated microreactor system called the Quantitative Carbon Detector (QCD) for use with current gas chromatography techniques for calibration-free quantitation of analyte mixtures was designed. Combined heating, catalytic combustion, methanation and gas co-reactant mixing within a single modular reactor fully converts all analytes to methane (>99.9%) within a thermodynamic operable regime. Residence time distribution of the QCD reveals negligible loss in chromatographic resolution consistent with fine separation of complex mixtures including pyrolysis products. The requirements are established for measuring the reaction kinetics of high temperature (>400 ˚C) biomass pyrolysis in the absence of heat and mass transfer limitations. Experimental techniques must heat and cool biomass samples sufficiently fast to elucidate the evolution of reaction products with time while also eliminating substantial reaction during the heating and cooling phases, preferably by measuring the temperature of the reacting biomass sample directly. These requirements were described with the PHASR (Pulsed-Heated Analysis of Solid Reactions) technique and demonstrated by measuring the time-resolved evolution of six major chemical products from Loblolly pine pyrolysis over a temperature range of 400 ˚C to 500 ˚C. Differential kinetics of loblolly pine pyrolysis were measured to determine the apparent activation energy for the formation of six major product compounds including levoglucosan, furfural and 2-methoxyphenol. Levoglucosan (LGA), a six-carbon oxygenate, is the most abundant primary product from cellulose pyrolysis with LGA yields reported over a wide range of 5−80 percent carbon (%C). In this study, the variation of the observed yield of LGA from cellulose pyrolysis was experimentally investigated. Cellulose pyrolysis experiments were conducted in two different reactors: the Frontier micropyrolyzer (2020-iS), and the pulse heated analysis of solid reactions (PHASR) system. The reactor configuration and experimental conditions including cellulose sample size were found to have a significant effect on the yield of LGA. Four different hypotheses were proposed and tested to evaluate the relationship of cellulose sample size and the observed LGA yield including (a) thermal promotion of LGA formation, (b) the crystallinity of cellulose samples, (c) secondary and vapor-phase reactions of LGA, and (d) the catalytic effect of melt-phase hydroxyl groups. Co-pyrolysis experiments of cellulose and fructose in the PHASR reactor presented indirect experimental evidence of previously postulated catalytic effects of hydroxyl groups in glycosidic bond cleavage for LGA formation in transport-limited reactor systems. PHASR experiments were performed to measure apparent kinetic parameters of cellulose fragmentation. The LGA formation step was decoupled from the initiation reactions by identifying cellobiosan as a chemical surrogate for cellulose pyrolysis intermediate melt phase. Kinetics of LGA formation step was measured using 13C1 cellobiosan samples to track the contribution of glucose monomer in cellobiosan. The activation energy Ea calculated from the slope of the Arrhenius plot was 26.9 ± 1.9 kcal/mol and the preexponential factor k0 calculated from the intercept was 4.2 × 107 sec-1. These kinetic parameters were found to be lower than the corresponding values for the previously proposed mechanisms of LGA formation calculated from DFT studies indicating a possibility of new, catalyzed mechanism of LGA formation.
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    Describing The Catalytic Role Of Alkaline Earth Metals On The Thermal Activation Of Cellulose
    (2020-05) Facas, Gregory
    Biomass fast pyrolysis has considerable potential for the production of renewable fuels and chemicals. Despite pyrolysis being studied for more than a hundred years, only a few commercial pyrolysis processes exist as the optimal feedstock composition and reaction conditions for this process remain unknown. The lack of process optimization can be attributed to the multiscale complexity of the process. During pyrolysis the constituents of biomass are fragmented in a matter of seconds through thousands of chemical reactions, that occur in multiple phases, and are simultaneously competing with various heat and mass transfer processes. All of these fundamental phenomena are understood poorly within pyrolysis literature. Pyrolysis is further complicated by alkali and alkaline earth metals that are naturally present in lignocellulosic biomass. These metals are known to alter pyrolysis chemistry and catalyze the initial breakdown of the polymer constituents of biomass. The main objective of this thesis was to investigate the mechanistic role of alkaline earth metals on the initial fragmentation of cellulose, the main component of biomass. Fundamental knowledge into pyrolysis chemistry has been limited previously due to an inability to obtain intrinsic kinetic, a critical tool used to validate reaction mechanisms. The requirements for proper measurement of high temperature (>400 °C) biomass pyrolysis kinetics are presented. Most importantly, these requirements mandate that for proper measurement of kinetic data, experimental techniques must heat and cool reaction samples sufficiently fast to elucidate the evolution of reaction products with time, while also eliminating substantial reaction during the heating and cooling phases. The ability of the PHASR (Pulse Heated Analysis of Solid Reactions) micro-reactor technique and other common pyrolysis reactor techniques to satisfy these requirements was discussed. PHASR can thoroughly satisfy all the requirements for measuring pyrolysis kinetics unlike other conventional reactor techniques. The PHASR technique was then utilized to study the kinetics of calcium assisted activation of cellulose. Conversion of calcium doped films of α-cyclodextrin, a known cellulose surrogate, was measured over a range of reaction temperatures (370-430 °C) and calcium concentrations (0.1-0.5 mmol Ca2+/g CD). The rate of conversion of α-cyclodextrin was significantly accelerated by the presence of calcium. Activation was shown to have a second order rate dependence on calcium concentration, suggesting the involvement of two calcium ions in the mechanism. First principle density functional theory calculations were performed on calcium catalyzed glycosidic bond cleavage and depict calcium as having two catalytic roles of disrupting hydrogen bonding in the cellulose matrix and stabilizing the transition state. The energetics from experiment and computations agree closely representing the first atomistic mechanism of metal catalyzed activation utilizing both experiments and computations. Kinetics of magnesium assisted activation were then measured with PHASR experiments to discern any effects from the size of the catalytic ion on activation chemistry. PHASR experiments were performed in identical temperature and metal concentrations to the calcium experiments. Magnesium assisted activation exhibited identical behavior to the calcium case with energetics of activation matching within experimental error.
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    Development of agroforestry systems for bioenergy crop production and soil conservation.
    (2012-10) Gamble, Joshua D.
    Agroforestry systems have been proposed as a means of dedicated bioenergy crop production that can potentially satisfy a broad suite of social, economic, and environmental objectives. Strategic placement of such systems may help to maximize economic returns from marginal crop land and reduce agricultural non-point source pollution. However, little is known about the performance of perennial bioenergy crops in agroforestry systems in the North Central Region. Moreover, the effectiveness of these crops in reducing certain types of agricultural non-point source pollution relative to conventional annual cropping systems is unknown. Therefore, experiments were conducted to 1) evaluate the establishment and productivity of dedicated woody and herbaceous perennial bioenergy crops in riparian alley cropping agroforestry systems, and 2) to evaluate the effects of dedicated perennial bioenergy crops on surface runoff and sediment loss relative to conventional and alternative annual cropping practices. In the first experiment, basal area of poplar clone ‘NM6’ averaged 1,045 and 1,744 mm2 tree-1 at two sites after two seasons, while that of willow clone ‘Fish Creek’ averaged 770 and 1,609 mm2 tree-1. Prairie cordgrass and a native polyculture were among the most productive herbaceous crops at both sites, averaging between 7.1 and 11.9 Mt ha-1 by the second growing season. During the first two years following establishment, competition for resources did not reduce establishment success or productivity of woody and herbaceous crops along the tree-crop interface. These results suggest that hybrid poplar and willow along with certain herbaceous bioenergy crops may be well suited to alley cropping on riparian sites, though more research is needed to evaluate crop persistence and productivity within the alley cropping environment. In the second experiment, a native grass mixture reduced the average sediment concentration in surface runoff by 87% and 90% relative to a corn-soybean rotation and no-till corn, respectively. Sediment concentrations in surface runoff from short-rotation willow did not differ from the corn-soybean rotation, but were reduced in fall surface runoff by 51% relative to no-till corn. These results suggest that soil conservation can be improved in short-rotation willow systems, but confirm previous findings that native grasses can provide excellent sediment retention relative to annual systems.
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    Development of high biomass content hot-melt pressure-sensitive adhesives
    (2014-08) Gu, Cheng
    A new approach was introduced for incorporating renewable biomass into existing commercial pressure-sensitive adhesive (PSA) polymers in the form of acrylated macromonomers (MM). MM were prepared with L-lactide and caprolactone via a bulk ring-opening polymerization initiated by N-hydroxyethyl acrylamide (HEAA). Acrylic adhesive copolymers were synthesized by free-radical solution polymerization in presence of 2-ethylhexyl acrylate (EHA), acrylamide and macromonomers. This approach was achieved without sacrificing adhesive performance. Incorporation of the MM into the polymers was confirmed via proton NMR. Properties and adhesive performance of the new polymer were compared with its 100% acrylic commercial version. When synthesized using the same approach, the biomass-containing PSA had a lower molecular weight, higher glass transition temperature (Tg) and lower melt viscosity. Introduction of MM had little impact of tack force, shear time and shear adhesion failure temperature and peel strength increased substantially. Influence of HEAA capped L-lactide/caprolactone MM composition on acrylic hot-melts was also reviewed. A series of MMs, synthesized using catalyzed ring-opening polymerizations, were produced containing a broad range of lactic acid and caprolactone repeat units. Results indicate that the properties and performance of adhesive polymers are strongly dependent on lactide composition. In general, increasing lactide content increases polymer hardness enhancing cohesive strength, while reducing it (i.e., increasing caprolactone content) softens the polymer. Optimal adhesion is found to require a balance between these tendencies as indicated by the existence of a clear maximum in both tack and peel data. The results demonstrate that a broad range of properties is achievable through relatively minor modifications to MM composition. It is expected that these hybrid materials can be optimized for a variety of self-adhesive applications.
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    Development of Lactide-based Macromonomers for Copolymerization with Acrylates to produce Adhesives and Coatings of High Renewable Contents
    (2019-01) Gu, Cheng
    A new approach was introduced for incorporating renewable biomass into existing commercial pressure-sensitive adhesive (PSA) polymers in the form of acryloyl macromonomers (MM). MMs were prepared with L-lactide and ε caprolactone via a bulk ring-opening polymerization initiated by N-hydroxyethyl acrylamide (HEAA). Acrylic adhesive copolymers were synthesized by free-radical solution polymerization in presence of 2-ethylhexyl acrylate (EHA), acrylamide and MMs. A series of MMs, synthesized using catalyzed ring-opening polymerizations, were produced containing a broad range of lactic acid and caprolactone repeat units. Results indicate that the properties and performance of adhesive polymers are strongly dependent on lactide composition. In general, increasing lactide content increases polymer hardness enhancing cohesive strength, while reducing it (i.e., increasing caprolactone content) softens the polymer. Optimal adhesion is found to require a balance between these tendencies as indicated by the existence of a clear maximum in both tack and peel data. The results demonstrate that a broad range of properties is achievable through relatively minor modifications to MM composition. It is expected that these hybrid materials can be optimized for a variety of self-adhesive applications. With the new MM approach, the relation between the dynamic wetting behavior on a soft viscoelastic surface and the rheological properties of materials can be studied. The mechanical properties of polymers are tailored through changing MM composition to provide a broad range of viscoelastic responses. It was found the wetting of these polymers supports the existence of two distinct wetting regions as opposed to the several, one in which the wetting line and ridge propagate smoothly together, and a second in which the ridge slows propagation and is eventually dropped leaving behind a residual deformation ridge. The focus is on ridge formation and properties controlling its propagation prior in the neglected former region. Although most past experimental studies emphasize the rate dependency of this process, results presented here indicate that ridge propagation is governed to a similar extent by film thickness and the vertical surface tension force. The data is used to develop a semi-empirical model consistent with the contribution of both viscous and elastic responses to the process. The ideas presented provide a new and more comprehensive view of the wetting of soft substrates.
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    Environmental and Economic Impacts of Small-Scale Biomass Gasification
    (2017-06) Ries, Matthew
    Biomass is one of the most abundant, easily accessible energy resources on the planet. However, much of the world’s available biomass is not fully utilized because it is distributed and is often left to rot or burn in open piles. Therefore, this material is not deemed economically worthwhile to transport to a large energy facility. Unused biomass emits large quantities of greenhouse gases and health hazards into the surrounding environment. One potential use for this wasted biomass is small-scale gasification, which can produce heat and electricity while simultaneously reducing harmful pollutants and reduce operating costs compared to commercial plants. The Power Pallet, a small-scale gasifier-generator system produced by All Power Labs (Berkeley, CA), is designed to produce up to 20kWe of electricity and can be easily transported due to its compact design. The purpose of this research is to quantify emissions factors of CO2, CO, CxHy, NOx, and PM from the Power Pallet system and compare them to current biomass usage methods. Results indicate that the Power Pallet significantly reduces CO2 compared to ordinary combustion processes because of the high carbon content stored in the biochar created as a byproduct of the gasification process. CO and PM emissions are also reduced compared to open burning and wood fired stoves due to a more carefully controlled combustion process. The net greenhouse effect of the gasifier was found to be lower than the other methods. However, large-scale biomass plants still emit lower CO, NOx, and PM emissions than distributed systems like the Power Pallet because of the additional exhaust cleaning technologies found on these plants. Additionally, it became clear over the course of testing that several improvements need to be made to increase efficiency, further reduce emissions, and increase ease of use to help this technology can realistically compete with existing technologies on a widespread scale.
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    Fast microwave-assisted thermochemical conversion of biomass for biofuel production
    (2015-12) Xie, Qinglong
    Concerns about diminishing fossil fuels and increasing greenhouse gas emissions are driving many countries to develop renewable energy sources. In this respect, biomass provides a carbon-neutral and sustainable solution. Pyrolysis and gasification belong to thermochemical processes which are currently the most appropriate and widely used among all the biomass utilization technologies. Microwave irradiation can provide heating for biomass pyrolysis and gasification, and has many advantages over conventional heating methods. In this dissertation, microwave heating was used in biomass pyrolysis and gasification for the production of bio-oil and syngas, respectively. In addition, in order to utilize the syngas produced, a single-step process was investigated for converting syngas to dimethyl ether (DME) on various bifunctional catalysts. In Chapter 2, the microwave heating characteristics of various biomass feedstocks and microwave absorbents were examined and compared. Experimental results show that microwave absorbents absorbed the microwave irradiation more effectively than biomass. The addition of these microwave absorbents to biomass feedstock during microwave-assisted thermochemical conversion significantly improved the heating characteristics. Among the three microwave absorbents studied, silicon carbide (SiC) exhibited higher microwave absorbing ability than activated carbon (AC) and graphite (GE), which was mainly attributed to a higher dielectric loss tangent (tan ) value of silicon carbide. In addition, higher microwave absorbing ability and heating rates were achieved when more microwave absorbents were used. Finally, a fast microwave-assisted biomass conversion system was developed. In Chapter 3, fast microwave-assisted catalytic co-pyrolysis of microalgae and scum on HZSM-5 catalyst for bio-oil production was investigated. The effects of co-pyrolysis temperature, catalyst to feed ratio, and microalgae to scum ratio on bio-oil yield and composition were examined. Experimental results show that temperature had great influence on the co-pyrolysis process. The optimal temperature was 550 ºC since the maximum bio-oil yield and highest proportion of aromatic hydrocarbons in the bio-oil were obtained at this temperature. The bio-oil yield decreased when catalyst was used, but the production of aromatic hydrocarbons was significantly promoted when the catalyst to feed ratio increased from 1:1 to 2:1. Co-feeding of scum improved the bio-oil and aromatics production, with the optimal microalgae to scum ratio being 1:2 from the perspective of bio-oil quality. The synergistic effect between microalgae and scum during the co-pyrolysis process became significant only when the effective hydrogen index (EHI) of feedstock was larger than about 0.7. In addition, to better understand the fMAP of microalgae, the different roles of three major components, i.e., carbohydrates, proteins, and lipids, were investigated. Cellulose, egg whites, and canola oil were employed as the model compounds of the three components, respectively. Non-catalytic and catalytic fMAP were carried out to identify and quantify some major products, and several reaction pathways were proposed for the pyrolysis of each model compound based on the data obtained. Moreover, a two-step process of microalgae pyrolysis and downstream catalytic reforming was conducted and compared with the one-step process for bio-oil production. The results show that a lower bio-oil yield and higher bio-oil quality were achieved for the two-step process than the one-step process at the same catalyst to feed ratio. The main advantages of the two-step process lie in catalyst saving and reuse. Furthermore, fast microwave-assisted catalytic pyrolysis of sewage sludge was investigated for bio-oil production, with HZSM-5 as the catalyst. Pyrolysis temperature and catalyst to feed ratio were examined for their effects on bio-oil yield and composition. Experimental results show that microwave is an effective heating method for sewage sludge pyrolysis. Temperature has great influence on the pyrolysis process. The maximum bio-oil yield and the lowest proportions of oxygen- and nitrogen-containing compounds in the bio-oil were obtained at 550 oC. The oil yield decreased when catalyst was used, but the proportions of oxygen- and nitrogen-containing compounds were significantly reduced when the catalyst to feed ratio increased from 1:1 to 2:1. Essential mineral elements were concentrated in the biochar after pyrolysis, which could be used as a soil amendment in place of fertilizer. Results of XRD analyses demonstrated that HZSM-5 catalyst exhibited good stability during the microwave-assisted pyrolysis of sewage sludge. In Chapter 4, the microwave-assisted biomass conversion system developed in Chapter 2 was used in corn stover gasification for syngas production. Three catalysts including Fe, Co and Ni with Al2O3 support were examined and compared for their effects on syngas production and tar removal. Experimental results show that microwave is an effective heating method for biomass gasification. Ni/Al2O3 was found to be the most effective catalyst for syngas production and tar removal. The gas yield reached above 80% and the composition of tar was the simplest when Ni/Al2O3 catalyst was used. The optimal catalyst to biomass ratio was determined to be 1:5–1:3. The addition of steam was found to be able to improve the gas production and syngas quality. Results of XRD analyses demonstrate that Ni/Al2O3 catalyst had good stability during gasification process. Finally, a new concept of microwave-assisted dual fluidized bed gasifier was put forward for the first time in all studies in the literature. To further utilize the syngas produced from biomass gasification, single-step synthesis of DME from syngas on bifunctional catalysts containing Cu-ZnO-Al2O3 and seven different zeolites was investigated in Chapter 5. Various characterization techniques were used to determine the structure, reducibility, and surface acidity of the catalysts. Experimental results show that the zeolite type had great influence on the activity, selectivity and stability of the bifunctional catalyst during the syngas-to-DME process. Zeolite properties including density of weak and strong acid sites, pore structure, and Si/Al distribution were found to affect the CO conversion and DME selectivity of the bifunctional catalyst. In addition, the deactivation of the bifunctional catalyst could be attributed to the sintering of metallic Cu and a loss of the zeolite dehydration activity. In summary, microwave irradiation is an effective heating method for biomass thermochemical conversion for biofuel production. Fast microwave-assisted biomass pyrolysis and gasification, using silicon carbide as the microwave absorbent, were carried out for the production of bio-oil and syngas, respectively. In addition, single-step synthesis of DME from syngas on various bifunctional catalysts was conducted with the aim of fully utilizing the syngas produced from biomass gasification. Although there are still many challenges associated with the production of biofuels via fast microwave-assisted thermochemical conversion, this dissertation offers a valuable insight into the potential of and some basic mechanisms of the technology.
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    Finding the Chemistry in Biomass Pyrolysis: Millisecond Chemical Kinetics and Visualization
    (2016-06) Krumm, Christoph
    Biomass pyrolysis is a promising thermochemical method for producing fuels and chemicals from renewable sources. Development of a fundamental understanding of biomass pyrolysis chemistry is difficult due to the multi-scale and multi-phase nature of the process; biomass length scales span 11 orders of magnitude and pyrolysis phenomena include solid, liquid, and gas phase chemistry in addition to heat and mass transfer. These complexities have a significant effect on chemical product distributions and lead to variability between reactor technologies. A major challenge in the study of biomass pyrolysis is the development of kinetic models capable of describing hundreds of millisecond-scale reactions of biomass into lower molecular weight products. In this work, a novel technique for studying biomass pyrolysis provides the first- ever experimental determination of kinetics and rates of formation of the primary products from cellulose pyrolysis, providing insight into the millisecond-scale chemical reaction mechanisms. These findings highlight the importance of heat and mass transport limitations for cellulose pyrolysis chemistry and are used to identify the length scales at which transport limitations become relevant during pyrolysis. Through this technique, a transition is identified, known as the reactive melting point, between low and high temperature depolymerization. The transition between two mechanisms of cellulose decompositions unifies the mechanisms that govern low temperature char formation, intermediate pyrolysis conditions, and high temperature gas formation. The conditions under which biomass undergoes pyrolysis, including modes of heat transfer, have been shown to significantly affect the distribution of biorenewable chemical and fuel products. High-speed photography is used to observe the liftoff of initially crystalline cellulose particles when impinged on a heated surface, known as the Leidenfrost effect for room-temperature liquids. Order-of-magnitude changes in the lifetime of cellulose particles are observed as a result of changing modes in heat transfer as cellulose intermediate liquid droplets wet and de-wet polished ceramic surfaces. Introduction of surface macroporosity is shown to completely inhibit the cellulose Leidenfrost effect, providing avenues for surface modification and reactor design to control particle heat transfer in industrial pyrolysis applications. Cellulosic particles on surfaces consisting of microstructured, asymmetric ratchets were observed to spontaneously move orthogonal to ratchet wells above the cellulose reactive Leidenfrost temperature (>750 °C). Evaluation of the accelerating particles supported the mechanism of propelling viscous forces (50-200 nN) from rectified pyrolysis vapors, thus providing the first example of biomass conveyors with no moving parts driven by high temperature for biofuel reactors. Combined knowledge of pyrolysis chemistry, kinetics, and heat and mass transport effects direct the design of the next generation pyrolysis reactors for tuning bio- oil quality and design of improved catalytic upgrading technology.
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    Grasslands and Brushlands of the Oak Savanna Region of Minnesota as Biomass Feedstock Sources
    (2010-01) Gillitzer, Peter Andrew
    Abstract summary not available.
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    Kinetics and mechanism of deoxygenation reactions over proton-form and molybdenum-modified zeolite catalysts
    (2014-07) Bedard, Jeremy William
    The depletion of fossil fuel resources and the environmental consequences of their use have dictated the development of new sources of energy that are both sustainable and economical. Biomass has emerged as a renewable carbon feedstock that can be used to produce chemicals and fuels traditionally obtained from petroleum. The oxygen content of biomass prohibits its use without modification because oxygenated hydrocarbons are non-volatile and have lower energy content. Chemical processes that eliminate oxygen and keep the carbon backbone intact are required for the development of biomass as a viable chemical feedstock. This dissertation reports on the kinetic and mechanistic studies conducted on high and low temperature catalytic processes for deoxygenation of biomass precursors to produce high-value chemicals and fuels. Low temperature, steady state reaction studies of acetic acid and ethanol were used to identify co-adsorbed acetic acid/ethanol dimers as surface intermediates within specific elementary steps involved in the esterification of acetic acid with ethanol on zeolites. A reaction mechanism involving two dominating surface species, an inactive ethanol dimeric species adsorbed on Brønsted sites inhibiting ester formation and a co-adsorbed complex of acetic acid and ethanol on the active site reacting to produce ethyl acetate, is shown to describe the reaction rate as a function of temperature (323 - 383 K), acetic acid (0.5 - 6.0 kPa), and ethanol (5.0 - 13.0 kPa) partial pressure on proton-form BEA, FER, MFI, and MOR zeolites. Measured differences in rates as a function of zeolite structure and the rigorous interpretation of these differences in terms of esterification rate and equilibrium constants is presented to show that the intrinsic rate constant for the activation of the co-adsorbed complex increases in the order FER < MOR < MFI < BEA. High temperature co-processing of acetic acid, formic acid, or carbon dioxide with methane (CH3COOH/CH4 = 0.04-0.10, HCOOH/CH4 = 0.01-0.03, CO2/CH4 = 0.01-0.03) on Mo/H-ZSM-5 formulations at 950 K and atmospheric pressure in an effort to couple deoxygenation and dehydrogenation reaction sequences results instead in a two-zone, stratified bed reactor configuration consisting of upstream oxygenate/CH4 reforming and downstream CH4 dehydroaromatization. X-ray absorption spectroscopy and chemical transient experiments show that molybdenum carbide is formed inside zeolite micropores during CH4 reactions. The addition of an oxygenate co-feed causes oxidation of the active molybdenum carbide catalyst while producing CO and H2 until completely converted. Forward rates of C6H6 synthesis are unperturbed by the introduction of an oxygenate co-feed after rigorously accounting for the thermodynamic reversibility caused by the H2 produced in oxygenate reforming reactions and the fraction of the active catalyst deemed unavailable for CH4 dehydroaromatization. All effects of co-processing C1-2 oxygenates and molecular H2 with CH4 can be interpreted in terms of an approach to equilibrium. Co-processing H2O, CO2, or light (C1-2, C/Heff < 0.25) oxygenates with CH4 at 950 K over Mo/H-ZSM-5 catalysts results in complete fragmentation of the oxygenate and CO as the sole oxygen-containing product. The C/Heff accounts for removal of O as CO and describes the net C6H6 and total hydrocarbon synthesis rates at varying (0.0-0.10) C1-2 oxygenate and H2 to CH4 co-feed ratios. Co-processing larger (C3-5, C/Heff ≥ 0.25) oxygenates with CH4 results in incomplete fragmentation of the co-fed oxygenate and preferential pathways of C6H6 synthesis that exclude CH4 incorporation. This results in greater net C6H6 synthesis rates than would be predicted from observations made when co-processing C1-2 oxygenates. Catalytic technologies have served a crucial role in processing petroleum feedstocks and are faced with new challenges as the feedstock shifts to chemically diverse but renewable biomass sources. This research addresses these challenges at fundamental and applied levels as it offers the potential to convert readily available biomass to commodity chemicals and fuels while simultaneously examining the elementary concepts of deoxygenation reactions on catalytic surfaces.
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    Managing conservation grasslands for bioenergy and wildlife
    (2014-02) Jungers, Jacob Michael
    Greenhouse gas emissions continue to rise while native grassland habitat continues to decline. A potential solution to both of these conservation priorities may exist in bioenergy. Various state and federal agencies maintain tracts of conservation grasslands, usually native perennial plants, for recreation and habitat. If biomass from conservation grasslands can be harvested without harming habitat and wildlife, then sales of grassland biomass to bioenergy producers may be the economic catalyst to expand conservation grassland acreage. This dissertation reports the bioenergy potential of conservation grasslands, how that potential can be improved, and possible effects of biomass harvest on grassland plants, ducks, and pheasants. Chapter one quantifies the bioenergy potential of biomass from conservation grasslands and identifies environmental characteristics that influence that potential. Chapter two reports an agronomically optimum nitrogen fertilization rate to increase bioenergy yields from switchgrass (Panicum virgatum) and mixed-species grasslands. Chapter three summarizes the effects of biomass harvest on plant diversity and species composition. Chapter four relates plant diversity and composition to duck and pheasant nest density and survival, and measures the effect of biomass harvest on both metrics of reproduction. Some major conclusion include: (1) Estimates of bioenergy potential suggest that 50% of the conservation grassland acreage within an 80 km radius of southwestern Minnesota could produce 75,700,000 liters of ethanol annually. (2) On average, bioenergy yields are predicted to increase by 52% when fertilized with agronomically optimum nitrogen rates ranging from 61 to 87 kg N ha-1. (3) Biomass harvest did not affect plant species richness, species or functional group diversity, nor change the relative abundance of the main plant functional groups in conservation grasslands. (4) Pheasant and duck nest success rates were similar in harvested and unharvested regions of conservation grasslands, but nest density was greater in unharvested regions. Overall, a substantial amount of renewable energy can be produced from harvested conservation grassland biomass without detrimental effects on plant communities or nesting pheasants and ducks.
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    Resource assessment and analysis of aspen-dominated ecosystems in the Lake States.
    (2010-08) Domke, Grant Michael
    Utilization of renewable resources for energy in the United States has increased substantially over the past decade. These increases have been driven by energy policy aimed at reducing dependence on foreign oil, boosting economic development, and curbing fossil fuel emissions. In recent years, state governments have passed laws mandating further reductions in energy consumption and greenhouse gas emissions, and increases in energy conservation and use of renewables. Such legislation and pending federal action has led to renewed interest in the use of forest-derived biomass for energy production. There are a variety of sources of forest-derived biomass in the Lake States and much debate over the carbon costs or benefits associated with the utilization of this material for energy. The aspen forest type is dominated by the most commercially utilized tree species in the region (Populus tremuloides and to a much lesser extent, P. grandidentata and P. balsamifera) and occupies more than 10 million acres of timberland in Michigan, Minnesota, and Wisconsin. Aspen is a short-lived, fast-growing tree species, which typically regenerates from adventitious suckers following harvest or stand-replacing disturbance, making it ideally suited for biomass production. This dissertation describes: 1) the status and trends of aspen-dominated ecosystems in the Lake States, 2) an analysis of biomass production potential in native and hybrid aspen communities in northern Minnesota, 3) a model framework for the estimation of carbon flows associated with the procurement and utilization of harvest residues for energy, and 4) the development of a spreadsheet-based model for rapid estimation of biomass availability.