Blending of Hydrothermal Liquefaction Biocrude with Residual Marine Fuel: An Experimental Assessment

As with all transport modes, the maritime sector is undergoing a drastic transition towards net zero, similar to the path in which Aviation is already engaged through global decarbonization programs such as CORSIA for the International Civil Aviation Organization, or the Emission trading Scheme of the European Union). Maritime indeed shares with Aviation a common element: the difficulty of shifting to electric in the short to medium term. Therefore, the use of sustainable fuels represents the main and only relevant option in this timeframe. As sustainable biofuels will be used as blend components in the case of large-scale deployment, it is necessary to investigate the behavior of bio- and fossil-based fuels when mixed in various percentages, in particular for low quality products such as HTL (HydroThermal Liquefaction) and fast pyrolysis oils from lignocellulosic biomass and waste. Biocrude from subcritical hydrothermal liquefaction of undigested sewage sludge, produced at reaction conditions of 350 °C and 200 bar in a continuous HTL pilot scale unit, was manually mixed at 70 °C with residual marine fuel (low-sulphur type F-RMG-380 per ISO 8217) at two different nominal biocrude shares, respectively 10 wt.% and 20 wt.% in the mixture. While the former blend resulted in the technically complete dissolution of biocrude in the fossil component, the latter sample formed biocrude agglomerates and only partial dissolution of the biocrude aliquot in marine fuel could be achieved (calculated between 14–16 wt.%). The blend with 10 wt.% of SS biocrude in the mixture resulted in compliance with limits of total acid number (TAN), inorganics (in particular vanadium, sodium, silicon and aluminum) and sulphur content, while only the ash content was slightly above the limit.

Development of a Mesoporous Silica-Supported Layered Double Hydroxide Catalyst for the Reduction of Oxygenated Compounds in E. grandis Fast Pyrolysis Oils

Biomass fast pyrolysis oil is a potential renewable alternative to fossil fuels, but its viability is constrained by its corrosiveness, low higher heating value and instability, caused by high oxygenate concentrations. A few studies have outlined layered double hydroxides (LDHs) as possible catalysts for the improvement of biomass pyrolysis oil characteristics. In this study, the goal was to reduce the concentration of oxygen-rich compounds in E. grandis fast pyrolysis oils using CaAl- and MgAl- LDHs. The LDHs were supported by mesoporous silica, synthesised at different pHs to obtain different pore sizes (3.3 to 4.8 nm) and surface areas (up to 600 m2/g). The effects of the support pore sizes and use of LDHs were investigated. GC/MS results revealed that MgAl-LDH significantly reduced the concentrations of ketones and oxygenated aromatics in the electrostatic precipitator oils and increased the concentration of aliphatics. CaAl-LDH had the opposite effect. There was little effect on the oxygenate concentrations of the heat exchanger oils, suggesting that there was a greater extent of conversion of the lighter oil compounds. Bomb calorimetry also showed a marked increase in higher heating values (16.2 to 22.5 MJ/kg) in the electrostatic precipitator oils when using MgAl-LDH. It was also found that the mesoporous silica support synthesised at a pH of 7 was the most effective, likely due to the intermediate average pore width (4 nm).

Gasoline like fuel from plastic waste pyrolysis and hydrotreatment

Recycling of plastic waste is desirable to lower environmental pollution and fulfil the requirements of circular economy. Energetic utilization is another possibility, however, municipal solid waste containing plastics is usually combusted to generate heat and electricity. An attractive way of dealing with plastic waste is pyrolysis, which has the potential of producing liquid hydrocarbons suitable as a transportation fuel. The pyrolysis results of three plastics produced in the largest amount globally, namely polyethylene, polypropylene and polystyrene as well as their mixtures are presented. The experiments were performed in a laboratory scale batch reactor. The pyrolysis oils were further processed by distillation to provide gasoline and diesel like (distillation cuts at 210 and 350 °C) hydrocarbons. The gasoline fractions were analysed by GC-MS and the composition was compared with the EU gasoline standard. It was found that the oils from PE, PP and PS contain compounds present in standard gasoline. Mixing PS with PE and PP before the pyrolysis, or the oils afterward produces much closer results to standard requirements as PS pyrolysis generates mostly aromatic content. As standard maximizes the olefin content of gasoline to 18 Vol%, hydrogenation was also performed using Pd based catalyst. The hydrogenation process significantly reduced the number of double bonds resulting in low olefin content. Results show that the pyrolysis of plastic waste mixtures containing PE, PP and PS is a viable method to produce pyrolysis oil suitable for gasoline-like fuel extraction and further hydrogenation of the product can provide gasoline fuels with low olefin content.

Co-feeding of vacuum gas oil and pinewood-derived hydrogenated pyrolysis oils in a fluid catalytic cracking pilot plant to generate olefins and gasoline

Background: The Waste2Road project exploits new sustainable pathways to generate biogenic fuels from waste materials, deploying existing industrial scale processes. One such pathway is through pyrolysis of wood wastes. Methods: The hereby generated pyrolysis liquids were hydrogenated prior to co-feeding in a fluid catalytic cracking (FCC) pilot plant. So-called stabilized pyrolysis oil (SPO) underwent one mild hydrogenation step (max. 200 °C) whereas the stabilized and deoxygenated pyrolysis oil (SDPO) was produced in two steps, a mild one (maximum 250 °C) prior to a more severe process step (350 °C). These liquids were co-fed with vacuum gas oil (VGO) in an FCC pilot plant under varying riser temperatures (530 and 550 °C). The results of the produced hydrocarbon gases and gasoline were benchmarked to feeding pure VGO. Results: It was proven that co-feeding up to 10 wt% SPO and SDPO is feasible. However, further experiments are recommended for SPO due to operational instabilities originating from pipe clogging. SPO led to an increase in the hydrocarbon gas production from 45.0 to 46.3 wt% at 550 °C and no significant changes at 530 °C. SDPO led to a rise in gasoline yield at both riser temperatures. The highest amount of gasoline was produced when SDPO was co-fed at a 530 °C riser temperature, with values around 44.8 wt%. Co-feeding hydrogenated pyrolysis oils did not lead to a rise in sulfur content in the gasoline fractions. The highest values were around 18 ppm sulfur content. Instead, higher amounts of nitrogen were observed in the gasoline. Conclusions: SPO and SDPO proved to be valuable co-refining options which led to no significant decreases in product quality. Further experiments are encouraged to determine the maximum possible co-feeding rates. As a first step, 20-30 wt% for SPO are recommended, whereas for SDPO 100 wt% could be achievable.

Influence of WPO (Waste Plastic Oil) - gasoline mixtures for emission characteristics on working spark-ignition engine

The utilization of liquid products as transportation fuel derived from the thermal decomposition of different plastic waste mixtures was investigated. The production of pyrolysis oils was performed in a laboratory-scale batch reactor utilizing polystyrene (PS), polypropylene (PP), and high-density polyethylene (HDPE) waste blends. Two different mixtures (10% PS – 60% PP – 30% HDPE; 10% PS – 30% PP – 60% HDPE) were prepared, and the influence of reflux was also studied. The pyrolysis oils were blended to commercial gasoline in the 0-100% range. It was found that each blend could be successfully used as an alternative fuel in a traditional spark-ignition engine without any prior modifications or fuel additive. However, based on the engine tests, the presence of the reflux is vital as the composition of the pyrolysis oil is closer to the commercial gasoline. The emission measurements showed increasing NOx emissions compared to neat gasoline, but, on the other side, a decrease in CO was noticed. These changes were much smaller in cases when reflux was used during oil production. Based on the obtained results, the utilization of reflux-cooling is an effective method to enhance the gasoline range hydrocarbons in the plastic waste pyrolysis oils, and therefore blending these oils to commercial gasoline might be viable.

Rheological Properties of Aged Crude Hard Wood Pyrolysis Oil

Upon storage of the pyrolysis oil, aging reactions may initiate phase separation and change of the rheological properties. These changes lead to unfavourable fuel characteristics in handling, transportation and applications. Efforts have been made for alleviation including methods on how to avoid these aging effects and development of equipment capable of handling aged pyrolysis liquids with unfavourable fuel characteristics. Therefore, the aim of this study was to explore the rheological properties of phase separated pyrolysis liquid fuel. Two batches of a well – stored poplar wood pyrolysis oils were used for the investigation; one batch was diluted with water to represent the oils undergoing severe phase separation (forced phase separation), and another batch was not diluted. Steady and dynamic rheological tests were conducted at various temperatures. Homogeneous (whole oil) and the bottom phases of pyrolysis oils were used. Results revealed that the whole oils of both diluted and undiluted oils exhibited low viscosity Newtonian behaviours at higher temperatures and high viscosity non-Newtonian behaviours at low temperatures. The bottom phases of both diluted and undiluted oils exhibited nonNewtonian behaviours with significant higher viscosity than the whole oils. The strain and frequency sweep dynamic tests showed existence of weak structures in the whole oils and strong network structures in the bottom phases. This study suggests that the handling, transportation and application of the pyrolysis oils undergoing phase separation are possible when the oils are treated with higher temperatures predominantly in turbulent state.

Detailed Group-Type Characterization of Plastic-Waste Pyrolysis Oils: By Comprehensive Two-Dimensional Gas Chromatography Including Linear, Branched, and Di-Olefins

Plastic-waste pyrolysis oils contain large amounts of linear, branched, and di-olefinic compounds. This makes it not obvious to determine the detailed group-type composition in particular to the presence of substantial amounts of N-, S-, and O-containing heteroatomic compounds. The thorough evaluation of different column combinations for two-dimensional gas chromatography (GC × GC), i.e., non-polar × polar and polar × non-polar, revealed that the second combination had the best performance, as indicated by the bi-dimensional resolution of the selected key compounds. By coupling the GC × GC to multiple detectors, such as the flame ionization detector (FID), a sulfur chemiluminescence detector (SCD), a nitrogen chemiluminescence detector (NCD), and a mass spectrometer (MS), the identification and quantification were possible of hydrocarbon, oxygen-, sulfur-, and nitrogen-containing compounds in both naphtha (C5–C11) and diesel fractions (C7–C23) originating from plastic-waste pyrolysis oils. Group-type quantification showed that large amounts of α-olefins (36.39 wt%, 35.08 wt%), iso-olefins (8.77 wt%, 9.06 wt%), and diolefins (4.21 wt%, 4.20 wt%) were present. Furthermore, oxygen-containing compounds (alcohols, ketones, and ethers) could be distinguished from abundant hydrocarbon matrix, by employing Stabilwax as the first column and Rxi-5ms as the second column. Ppm levels of sulfides, thiophenes, and pyridines could also be quantified by the use of selective SCD and NCD detectors.