Pilot-scale continuous flow hydrothermal liquefaction of mixed textile waste and subsequent bio-oil upgrading

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Development of innovative processes and catalysts for the valorisation of Bio-Oil

Hydrothermal liquefaction (HTL) is a process for converting waste biomass to bio-oil by contacting the biomass with water at high temperatures and sufficient pressures in order to keep the water in the liquid state. HTL process is energy efficient and capable of dealing with wet biomass, such as sorted domestic organic waste, sewage sludge, algae, etc. However, HTL oils contain high contents of oxygen and nitrogen because of the initial biomass composition. Therefore, the bio-oil has to be upgraded in order to produce advanced transport fuels. Information regarding the nitrogen compounds present in bio-oil is of major concern of any hydrotreatment, since the low hydrodenitrogenation rate and catalyst poisoning by nitrogen compounds make this process expensive. Therefore, the main goal of the present study is the investigation of the HTL reaction mechanism, focusing the attention on the nitrogen containing species pathways, with the goal to increase the energy yields and reduce the nitrogen content in the produced bio-oil. Due to the complexity of the biomass composition, model compounds that encompass all the biochemical components of biomass, namely proteins, lipid and carbohydrates, are emerged to unravel the main chemical reaction pathways existing between macromolecular components. Moreover, several microbial biomass types, such as oleaginous yeast and liamocins, were also treated via HTL. The whole study helps to better understand the HTL of organic waste biomass and microbial biomass/oils, providing useful insights into the reaction products, pathways, and mechanisms for the production of bio-oils and chemicals

Synergistic hydrothermal liquefaction of waste materials

Synthetic polymers constitute one of the largest fractions of solid waste worldwide. From 1950 to 2015, roughly 12 Gton of these materials were deposited either in landfills or in the environment. The absolute majority of these materials are energetically dense, fossil-derived and non-biodegradable, which causes accumulation in the environment, threatening both marine and terrestrial ecosystems. Chemical recycling of these materials can be a management strategy to alleviate pollution and to reuse otherwise wasted energy in the form of solid materials. Agricultural crop residues are composed of both wet and dry streams, summing up to 3600 Mton year-1 (2013 estimate) of wasted resources globally. Besides that, around 3120 MTon year-1 (2017 estimate) of animal manure is generated worldwide. Nowadays, these agribusiness byproducts are underutilized and their conversion to liquid biofuels may present an untapped opportunity to provide the sustainability needed in sectors dependent on liquid hydrocarbons as an energy source. This thesis focuses on understanding how synthetic polymers and agricultural waste interact under hydrothermal liquefaction (HTL) conditions, identifying opportunities and evaluating the engineering challenges to apply the technology in combined processing of waste streams. This work evaluates the possibility of recovering monomer-like structures from synergistic combined HTL (co-HTL) of synthetic materials and lignocellulosic biomasses. It also evaluates how biocrudes derived from highly synergistic co-HTL behave in downstream processing for biofuel production when compared to single-feedstock biocrudes. HTL uses the reactivity of hot-compressed water in near-critical conditions to convert carbon-based materials into useful short chain organic compounds. The interaction of different feedstock materials under this condition allows a beneficial process efficiency and enlarges the opportunities to apply this process in waste handling scenarios. Literature about HTL processing of synthetic polymers present significant achievements within the field, however the non-standardized approach for several studies lead to contradictory results, generating a knowledge gap between laboratory results and practical applications. Here, results of subcritical HTL processing are presented for the 12 most used synthetic polymers worldwide, both individually and combined with lignocellulosic materials. When evaluating synthetic polymers alone, it is found that materials containing heteroatoms in the backbone of the polymer structure are prone to hydrolysis under subcritical water, while carbon-carbon bonds are preserved. In practice, polymers derived from addition polymerization such as polyolefins and polystyrene do not depolymerize under subcritical water, while condensation polymers and others containing heteroatoms in the backbone are decomposed into molecules similar to their original monomers. When these materials are combined with lignocellulosic ones, the synthetic parts containing nitrogen heteroatoms tend to synergistically interact with the organic-derived molecules and act synergistically increasing biocrude production. The reactivity of nitrogen species in synthetic polymers was directly proportional to the intensity of the synergies verified. The largest synergy identified was for polyurethane combined processing due to the presence of highly reactive amines bonded to aromatic groups. This finding led to an improved combinedprocessing of polyurethane foam and lignocellulosic materials, reaching pilot processing carbon and energy efficiencies of 71 and 75%, respectively. The combination of wet and dry agribusiness waste fractions in HTL processing was evaluated using cow manure and wheat straw, respectively, as representatives. Their combination also leads to enhanced biocrude and carbon recovery during subcritical HTL processing through nitrogen species reactions with lignocellulosic-derived compounds. The formation of heteroatom-containing aromatics acts as a carbon carrier to the biocrude products. With this approach, pilot HTL processing carbon yields were enhanced from 40 to 60 wt%, while also providing superior total energy efficiencies (up to 50% based on organic input and output including heating utilities). This increase in carbon efficiency generates further benefits in the production of hydrotreated products, with biomass-to-hydrotreated products carbon balances increasing from 34 wt% for wheat straw in single HTL to 43 wt% in co-HTL of wheat straw and cow manure. The distillation of hydrotreated products depicts that the nitrogen-containing molecules tend to have higher concentration in heavier fractions, which may be an opportunity for more targeted processing of these fractions. Overall, production of biofuels enlarged via co-HTL mainly due to HTL superior carbon and energy yields. Both synthetic-organic and organic-organic waste combined HTL, the reactions involving nitrogen compounds generate high synergistic effects towards biocrude formation. When increasing product stability through nitrogenated species, a consequent increased difficulty for their removal in following hydrotreatment oil upgrading is also verified. Nevertheless, the enhanced carbon and energy recovery and enlarged scope of HTL technologies attainedvia combination of waste materials is an opportunity to take advantage of these sub-utilized streams

Synergistic hydrothermal liquefaction of waste materials

Synthetic polymers constitute one of the largest fractions of solid waste worldwide. From 1950 to 2015, roughly 12 Gton of these materials were deposited either in landfills or in the environment. The absolute majority of these materials are energetically dense, fossil-derived and non-biodegradable, which causes accumulation in the environment, threatening both marine and terrestrial ecosystems. Chemical recycling of these materials can be a management strategy to alleviate pollution and to reuse otherwise wasted energy in the form of solid materials. Agricultural crop residues are composed of both wet and dry streams, summing up to 3600 Mton year-1 (2013 estimate) of wasted resources globally. Besides that, around 3120 MTon year-1 (2017 estimate) of animal manure is generated worldwide. Nowadays, these agribusiness byproducts are underutilized and their conversion to liquid biofuels may present an untapped opportunity to provide the sustainability needed in sectors dependent on liquid hydrocarbons as an energy source. This thesis focuses on understanding how synthetic polymers and agricultural waste interact under hydrothermal liquefaction (HTL) conditions, identifying opportunities and evaluating the engineering challenges to apply the technology in combined processing of waste streams. This work evaluates the possibility of recovering monomer-like structures from synergistic combined HTL (co-HTL) of synthetic materials and lignocellulosic biomasses. It also evaluates how biocrudes derived from highly synergistic co-HTL behave in downstream processing for biofuel production when compared to single-feedstock biocrudes. HTL uses the reactivity of hot-compressed water in near-critical conditions to convert carbon-based materials into useful short chain organic compounds. The interaction of different feedstock materials under this condition allows a beneficial process efficiency and enlarges the opportunities to apply this process in waste handling scenarios. Literature about HTL processing of synthetic polymers present significant achievements within the field, however the non-standardized approach for several studies lead to contradictory results, generating a knowledge gap between laboratory results and practical applications. Here, results of subcritical HTL processing are presented for the 12 most used synthetic polymers worldwide, both individually and combined with lignocellulosic materials. When evaluating synthetic polymers alone, it is found that materials containing heteroatoms in the backbone of the polymer structure are prone to hydrolysis under subcritical water, while carbon-carbon bonds are preserved. In practice, polymers derived from addition polymerization such as polyolefins and polystyrene do not depolymerize under subcritical water, while condensation polymers and others containing heteroatoms in the backbone are decomposed into molecules similar to their original monomers. When these materials are combined with lignocellulosic ones, the synthetic parts containing nitrogen heteroatoms tend to synergistically interact with the organic-derived molecules and act synergistically increasing biocrude production. The reactivity of nitrogen species in synthetic polymers was directly proportional to the intensity of the synergies verified. The largest synergy identified was for polyurethane combined processing due to the presence of highly reactive amines bonded to aromatic groups. This finding led to an improved combinedprocessing of polyurethane foam and lignocellulosic materials, reaching pilot processing carbon and energy efficiencies of 71 and 75%, respectively. The combination of wet and dry agribusiness waste fractions in HTL processing was evaluated using cow manure and wheat straw, respectively, as representatives. Their combination also leads to enhanced biocrude and carbon recovery during subcritical HTL processing through nitrogen species reactions with lignocellulosic-derived compounds. The formation of heteroatom-containing aromatics acts as a carbon carrier to the biocrude products. With this approach, pilot HTL processing carbon yields were enhanced from 40 to 60 wt%, while also providing superior total energy efficiencies (up to 50% based on organic input and output including heating utilities). This increase in carbon efficiency generates further benefits in the production of hydrotreated products, with biomass-to-hydrotreated products carbon balances increasing from 34 wt% for wheat straw in single HTL to 43 wt% in co-HTL of wheat straw and cow manure. The distillation of hydrotreated products depicts that the nitrogen-containing molecules tend to have higher concentration in heavier fractions, which may be an opportunity for more targeted processing of these fractions. Overall, production of biofuels enlarged via co-HTL mainly due to HTL superior carbon and energy yields. Both synthetic-organic and organic-organic waste combined HTL, the reactions involving nitrogen compounds generate high synergistic effects towards biocrude formation. When increasing product stability through nitrogenated species, a consequent increased difficulty for their removal in following hydrotreatment oil upgrading is also verified. Nevertheless, the enhanced carbon and energy recovery and enlarged scope of HTL technologies attainedvia combination of waste materials is an opportunity to take advantage of these sub-utilized streams

Development of innovative processes and catalysts for the valorisation of bio-oil

Hydrothermal liquefaction (HTL) is a process for converting waste biomass to bio-oil by contacting the biomass with water at high temperatures and sufficient pressures in order to keep the water in the liquid state. HTL process has the advantage of being energy efficient and capable of dealing with wet biomass, such as sorted domestic organic waste, sewage sludge, algae, etc. Despite being a very promising technology economically and environmentally, waste to fuels via HTL has not progressed from pilot scale to industry, primarily due to the issues associated with the recycling of the aqueous phase. Moreover, waste-derived bio-oil obtained by HTL contains high contents of oxygen and nitrogen because of the initial biomass composition. Therefore, the bio-oil has to be upgraded in order to produce advanced transport fuels. Information regarding the types of nitrogen compounds present in bio-oil is of major concern of any hydrotreatment, since the low hydrodenitrogenation rate and catalyst poisoning by nitrogen compounds make this process expensive. Therefore, the main goal of the present study is the investigation of the HTL reaction mechanism, focusing the attention on the nitrogen containing species pathways, with the goal to increase the energy yields and reduce the nitrogen content in the produced bio-oil. Due to the complexity of the biomass composition, model compounds that encompass all the biochemical components of biomass, namely proteins, lipid and carbohydrates, are emerged to predict important outcomes from HTL of any wet biomass feedstock. Furthermore, several microbial biomass types, such as oleaginous yeast and liamocins, were treated via HTL to produce bio-oil and commercially attractive chemicals. This work consists of main five parts. In the first part the decomposition behavior of amino acids alone and in binary mixtures with glucose and tripalmitin as representative model compounds of proteins, lipids, carbohydrates, respectively, is investigated. Most attention is paid to the carbon and nitrogen transferring into HTL product streams. Moreover, the effect of homogenous and heterogeneous catalysts, besides the solvents on the HTL product streams is investigated. The second part includes a comprehensive model study on albumin/starch/tripalmitin mixture in order to mimic a more reliable biomass model and evaluate all the the possible interactions within biomass macromolecular components. Importantly, the effect of biomass composition on the type of nitrogen compounds in the resulting bio-oil is determined. In the third part deamination of amino acids to produce α-hydroxycarboxylic acids under hydrothermal conditions is investigated in the presence of heterogeneous catalysts. The fourth part reports a potential application of the HTL process for the production of bio-oils from oleaginous yeasts. Finally, in the fifth part hydrothermal decomposition of liamocins, another microbial biomass, to produce commodity chemicals, e.g. ð-lactones containing alkyl chains, is reported. The whole study presented in this thesis helps to better understand the HTL of organic waste biomass and microbial biomass/oils, providing useful insights into the reaction products, pathways, and mechanisms for the production of bio-oils and chemicals

Elucidation of reaction pathways of nitrogenous species by hydrothermal liquefaction process of model compounds

The reaction pathway of nitrogen containing compounds under hydrothermal liquefaction (HTL) conditions was investigated by using amino acids as protein model compounds. The effect of organic acids and alkaline catalysts was also investigated by determining the structure and the partition of nitrogen containing species between the resulting solid, aqueous and bio-oil phases.Representative results showed that operating in a water-acetic acid (95/5% v/v) binary solvent system resulted in a dramatic improvement in carbon recovery in the oil phase due to the transformation of water soluble hydrophilic products into oil soluble derivatives by acylation of the amino moiety.The conclusions of this study provide a useful tool to improve the HTL process applied to nitrogen rich biomass, such as the organic fraction of urban waste, sewage sludge, and aquatic biomass (microalgae)

Influence of catalytic systems on process of model object hydrogenation

Abstract On the basis of β-FeOOH, Fe(OA)3, Fe3O4 iron and spherical catalysts NiO/SiO2, Fe2O3/SiO2 derived from slag waste coals of heating electrical stations, the hydrogenation of model polycyclic hydrocarbon at presence of nanodimensioned catalysts antracene was studied. On the example of conversion of anthracene, it was shown that upon release of hydrogenation of the product yield and degradation of polycyclic hydrocarbons in the hydrogenation, the mentioned catalyst systems appeared to be in the following order: nanoparticles β-FeOOH, Fe(OA)3 and Fe3O4>spherical catalysts NiO/SiO2, Fe2O3/SiO2>commercial cobalt-molybdenum catalyst. The results showed that the catalysts studied are promising catalysts for the hydrogenation of polycyclic hydrocarbons and may be used for direct coal liquefaction

MCM-41 Supported Co-Based Bimetallic Catalysts for Aqueous Phase Transformation of Glucose to Biochemicals

The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using N2 physisorption, Temperature Programmed Reduction (TPR), Raman, X-ray Diffraction (XRD) and Temperature Programmed Desorption (TPD) techniques. According to the N2-physisorption results, a high surface area and mesoporous structure of the support were appropriate for metal dispersion, reactant diffusion and the formation of bioproducts. Reaction conditions, bimetals synergetic effects and the amount and strength of catalyst acid sites were the key factors affecting the catalytic activity and biochemical selectivity. Sever reaction conditions including high temperature and high catalyst acidity led to the formation mainly of solid humins. The NH3-TPD results demonstrated the alteration of acidity in different bimetallic catalysts. The 10Fe10CoSiO2 catalyst (MCM-41 supported 10 wt.%Fe, 10 wt.%Co) possessing weak acid sites displayed the best catalytic activity with the highest carbon balance and desired product selectivity in mild reaction condition. Valuable biochemicals such as fructose, levulinic acid, ethanol and hydroxyacetone were formed over this catalyst