30 years of hydroprocessing at UCT Prague: The transition from petroleum feedstocks to bio-oils from HTL and pyrolysis

Please click Additional Files below to see the full abstract

Upgrading of wheat/barley and miscanthus bio-oil over a sulphided catalyst

In recent years, the production of biofuels from non-food crops wastes and harvesting residues plays an important role in the improvement of the global environment and in the replacement of declining oil reserves1. Hydrogenation of lignocellulosic bio-oil is attracting much attention as a suitable way to produce petroleum-refinery compatible feedstock. Primarily, hydrogenation of bio-oil is carried out under severe reaction conditions in two-stage fixed-bed reactors, filled with a noble metal catalyst in the first zone and with a sulphided catalyst in the second zone2. This setup allows producing low-oxygen upgraded bio-oil, however, it is economically unviable and operationally complicated. Here, we present the results from 80 h long hydrogenation experiments of miscanthus and wheat/barley straw bio‑oils obtained by one-stage condensation (2-5 °C) or fractional condensation (75 °C) ablative fast pyrolysis (AFP). Bio-oils from fractional condensation, in contrast to those from one-stage condensation, were stable and did not separate into an aqueous and organic phase. In that case, operation with these bio-oils was much easier than with bio-oils from one-stage condensation. Upgrading of bio-oils was performed in a one-stage fixed bed reactor filled with a laboratory-made NiMo/Al2O3 catalyst under constant reaction conditions (340 °C, 4 MPa and WHSV 1 h-1), which we identified in our previous research as suitable reaction conditions. Hydrogenated products separated spontaneously into an aqueous phase, formed predominantly by water, and an organic phase. In this work, we used various analytical methods for the determination of physicochemical properties (density, viscosity, elemental analysis etc.) and chemical composition (CAN, Carbonyls by Faix, GC-MS for volatile compounds and hydrocarbons) of the organic products. In addition, we used FTIR in combination with the principle component analysis (PCA) to take a snapshot of the catalyst health and product quality. In all hydrogenated products, we have observed a drop in the quality with the increasing time-on-stream, which may be caused by catalyst deactivation and coke formation, as it shown in Figure 2. Nevertheless, the coke formation and reactor clogging, during the hydrogenation of miscanthus bio-oil, was so high that we were forced to stop the experiment after 36 hours. The observed decrease in Micro Conradson Carbon residues and CAN of the products from wheat/barley straw bio-oil indicated a significant improvement of the product stability. The laboratory-made NiMo/Al2O3 catalyst was suitable for the upgrading of straw bio-oil, from one-stage and from fractional condensation AFP, and can be further developed for the upgrading for other feedstocks. Please click Additional Files below to see the full abstract

Hydrotreating of waste plastic pyrolysis oil with increased chlorine and nitrogen content

Please click Additional Files below to see the full abstract

Carbonyl content determination in bio-oils with increased nitrogen content

Please click Additional Files below to see the full abstract

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

Fuels from reliable bio-based refinery intermediates: BioMates

The overall aim of the project “BioMates” is to develop a conversion process for agricultural residues (cereal straw) or energy crops (miscanthus) into a liquid intermediate with reliable properties for the co-processing in existing petroleum refineries. The process is divisible into two individual steps—ablative fast pyrolysis and mild hydrotreatment. Both biomass feedstocks were pyrolysed in a laboratory plant and optimal parameters leading to highest organic liquid yield were determined to be 540 °C at the hot surface, 50 bar hydraulic pressure and 80 rpm of rotational speed of the ablation plate. Different setups for condensation and catalytic vapour upgrade were tested and best results regarding highest organic yield with lowest water content could be achieved with a two-stage condensation operating at about 68 °C condensation temperature in the first stage. Here, a total yield of 41 wt% in (oxygenated) organic compounds could be achieved in the first stage condensate compared to only 36 wt% in the tarry phase of single stage condensation. Catalysts for direct upgrading of vapours were tested but found to be inappropriate in the current setup. For mild hydrotreatment conventional sulphidized catalyst and newly developed non-sulphidized catalysts were tested. The new catalysts showed high initial reactivity but fast deactivation. Currently, the commercial catalyst with NiMo-system on Al2O3-support performed best, especially at 8 MPa hydrogen supply pressure and 360 °C operating temperature. Here, water content below 1 wt%, a density of organic product below 0.9 kg dm−3 and a lower heating value above 39 MJ kg−1 was achieved. Electrochemical compression and purification can supply hydrogen at necessary pressure and flow rate with acceptable energy demand and by that can replace mechanical compression on the supply side and pressure swing adsorption system in the recycle loop. The project aims were fully achieved in TRL3-4 and will be demonstrated in TRL5 until the end of the project

Detailed characterization of sulfur compounds in fast pyrolysis bio-oils using GC × GC-SCD and GC–MS

Only trace amounts of sulfur (tens to thousands of ppm) are present in bio-oils produced from fast pyrolysis of lignocellulosic biomass. However, even such small amounts of sulfur-containing compounds can act as catalytic poisons during bio-oil upgrading. To improve the knowledge of sulfur speciation in bio-oils for process design and development, e.g. by hydrotreatment, comprehensive two-dimensional gas chromatography (GC x GC) coupled with selective sulfur chemiluminescence detector (SCD) and headspace gas chromatography coupled to a quadrupole mass spectrometry (GC-MS) were combined. This allowed to quantify sulfur-containing compounds present in crude bio-oils produced from different types of biomass (beech wood, miscanthus, and straw) and straw bio-oil after hydrotreatment. Hydrogen sulfide, methanethiol, dimethyl disulfide, and several thiophenes were identified and quantified as the most abundant sulfur compounds. The detailed analysis of the hydrotreated bio-oil prepared at 360 degrees C and 8 MPa showed that most GC-detectable sulfur was related to hydrogen sulfide not sufficiently removed in the product separator. Used analytical methods brought an unprecedented level of details about bio-oil sulfur speciation and acquired data can help to drive further R&D in bio-oil upgrading

Application of orbitrap mass spectrometry for analysis of model bio-oil compounds and fast pyrolysis bio-oils from different biomass sources

Pyrolysis bio-oils have great potential for the future use as biofuels and source of oxygenated chemicals. To optimize a pyrolysis process, detailed knowledge about the chemical composition of bio-oils is necessary. In recent years, high-resolution mass spectrometry (HRMS) has successfully been used to the characterization of pyrolysis bio-oils from lignocellulosic biomass. This method enabled to detect thousands of semivolatile and nonvolatile, high-molecular-weight bio-oil compounds and provided partial information about their structure. In this work, we used high-resolution orbitrap mass spectrometry to characterize semivolatile and nonvolatile, high-molecular-weight compounds of four bio-oils obtained from the ablative flash pyrolysis of different biomass sources. Before the analyses of these bio-oils, we analyzed model bio-oil compounds and commercially available bio-oil from fast pyrolysis of wood using positive-ion and negative-ion electrospray (ESI) and positive-ion and negative-ion atmospheric pressure chemical ionization (APCI) orbitrap mass spectrometry and compared the results. Based on this comparison, a combination of negative-ion ESI and APCI was found to be well suited for the characterization of pyrolysis bio-oils; these techniques were thus used for the study of bio-oils from different biomass sources and the obtained results were compared. In the studied bio-oils, mostly compounds with 1–8 oxygen atoms per molecule were detected and their degree of unsaturation (DBE) was about 1–10 (negative-ion ESI) and 1–17 (negative-ion APCI), respectively. Among the studied bio-oils, the differences were observed mostly in abundances of their major compounds (compound classes). The analyses of model bio-oil compounds brought valuable information about their behavior during the HRMS characterization of bio-oils. The presented results could help to improve the understanding of bio-oil composition and HRMS characterization of bio-oils and facilitate their further utilization

Fluid catalytic co-processing of bio-oils with petroleum intermediates : comparison of vapour phase low pressure hydrotreating and catalytic cracking as pretreatment

For co-processing of bio-oil and conventional fossil feed in existing refinery fluid catalytic cracking (FCC) units, little attention has been paid to the increased aromatics and basic nitrogen content in the feed associated with the introduction of bio-oil and how it affects FCC performance. In this contribution, the effect of blending two biooils obtained from different catalytic treatment of wheat-straw pyrolysis vapors with atmospheric residue was tested using a microactivity testing unit (MAT). The catalysts used for the pyrolysis vapor phase upgrading included i) a Na/gamma-Al2O3 deoxygenation catalyst, and ii) a Pt/TiO2 catalyst in combination with H2 atmosphere. The oxygen content of both bio-oils was similar at - 7-8 wt%, but the Na/gamma-Al2O3 bio-oil had a lower total acid number (TAN) of 5 mg KOH/g and a higher basic nitrogen (BN) content of 0.7 wt% compared to the Pt/TiO2 biooil (15 mg KOH/g, 0.4 wt% BN). The processing of the upgraded bio-oils in blends with atmospheric residue in MAT increased the yields of dry gas, CO, CO2, and coke at the expense of naphtha (decrease by 2.8 percentage points) and decreased the conversion by - 2.5 percentage points. This is attributed to the high aromaticity and basic nitrogen content of the two bio-oils. The lower basic nitrogen content and higher degree of saturation for the Pt/TiO2 bio-oil may explain its slightly higher conversion (by <= 1 percentage points) compared to the Na/gamma-Al2O3 bio-oil. This contribution provides important information for refinery operators interested in FCC co-processing of fossil oils and biomass-derived pyrolysis oils with elevated content of nitrogen and aromatics