Renewable Energy, Sustainability and the Environment, Process Chemistry and Technology, Catalysis, Fuel Technology
19
Scopus Publications
Scopus Publications
Heat release analysis of dual-fuel direct injected ammonia and HTL fuels David Zilles, David R. Emberson, Daniele Castello, Abdenour Achour Fuel, 2026 • Dual-fuel experimental study of liquid ammonia injections combusted in a Constant Volume Combustion Chamber (40 bar, 923 K initial conditions). • Three different hydrothermal liquefaction-based biofuels and n-heptane as pilot injection. • Apparent heat release analysis for four relative injection timings, and three different ammonia energy shares (88-96%). • Evaluation of ignition delay times reveals earlier heat release for biofuels than for n-heptane. • Earlier pilot ignition improves ammonia heat release. Fastest and highest heat release observed for the least upgraded biofuel. Ammonia (NH 3 ) has the potential to decarbonize combustion engines for intercontinental long-distance shipping as a non-carbonaceous fuel, but its low reactivity necessitates the use of a combustion-promoting strategy. This study experimentally explores a dual-fuel approach using a pilot injection to enhance the ignition and combustion of liquid injected NH 3 mixtures (main injection) under conditions typical for compression ignition engines. Three grades of diesel-type biofuels produced via hydrothermal liquefaction (HTL) of food waste are utilized as high-reactivity pilot fuels. The literature shows, that physical interaction between pilot and main fuel injections is critical for controlling NH 3 heat release. To isolate and control this influence, this study utilizes a constant volume combustion chamber with two automotive direct injectors. The work presented here characterizes the relative injector position and analyses the heat release curves. A set of evaluation criteria, including ignition delay time, is used to quantify the combustion quality. Variations of ammonia energy share (AES) from 88 to 96% and relative injection timings for HTL-fuels (−2.5 ms to 7.5 ms after start of NH 3 injection) are compared to baseline experiments with n-heptane pilots under constant ambient conditions (40 bar, 853 K). Results confirm the importance of spatial and temporal interaction between pilot injection and main fuel. All three HTL-fuel samples showed good combustibility and ignition of NH 3 for AES of 90% and higher, regardless of their processing grade, but depending on relative injection timing. The ignition delay was measured to be shorter for HTL-fuels than for n-heptane. Independent of the AES, the highest combustion efficiency was observed when the pilot injection was delayed by 2.5 ms relative to start of NH 3 injection.
Understanding catalyst deactivation in an industrial green hydrotreater and its correlation with catalyst composition Elham Nejadmoghadam, Abdenour Achour, Olov Öhrman, Derek Creaser, Louise Olsson Fuel Processing Technology, 2025 Understanding and mitigating catalyst deactivation is crucial for enhancing the efficiency of hydrodeoxygenation (HDO) processes in the production of biofuels. In this study sulfided metal catalysts, NiMo/Al 2 O 3 , NiMo/SiO 2 -Al 2 O 3 , and NiW/Al 2 O 3 along with bare supports (Al 2 O 3 , SiO 2 -Al 2 O 3 , and zeolite Y) were placed in a refinery green hydrotreating unit. Potassium, phosphorus and sodium were identified as major poisons. The HDO activity of spent catalysts was assessed in a lab-scale batch reactor at 58 bar H 2 and 325 °C for deoxygenation of oleic acid. The results highlighted that the active metals, particularly NiW, had a more pronounced tendency to attract poisons compared to the supports. However, with bare supports, coking was more significant and simultaneously less poisons were trapped, which could be due to blocking of the pores with coke. In the presence of these poisons there was a significant decline in oxygenate conversion compared with fresh catalysts, with a gradual reduction in activity for both decarbonation and direct-HDO products. Solvent washing treatments with DMSO and water were employed in an attempt to recover the activity of the spent catalysts, by partially removing the poisons. However, through these treatments, the activity of the NiMo/Al 2 O 3 catalyst could not be restored.
Lab-scale catalytic hydrotreating of hydrothermal biocrude: Effects of temperature and space velocity on fuel upgrading and catalyst performance Abdenour Achour, Daniele Castello, Muhammad Salman Haider, Lasse Aistrup Rosendahl Chemical Engineering Journal, 2025 This study examines the continuous catalytic hydrotreating of hydrothermal liquefaction (HTL) biocrude derived from food waste (biopulp), emphasizing the effects of temperature and space velocity on catalyst stability, heteroatom removal, and product distribution. A 1911-hour operational campaign provided comprehensive insights into catalyst deactivation mechanisms. Oxygen content was reduced to 0.4 wt% at 400 °C, primarily via hydrodeoxygenation, while cyclic nitrogen species exhibited significant resistance to hydrogenation. Lower space velocities facilitated enhanced catalyst interaction, improving deoxygenation efficiency but proving insufficient for complete hydrodenitrogenation. A dynamic pathway mechanism was introduced to elucidate functional group transformations, highlighting the competing reaction pathways governing heteroatom removal and saturations of aromatics and alkenes. Additionally, volume swell optimization demonstrated a direct correlation with improved fuel yield and refinery compatibility. These findings contribute to the optimization of catalytic upgrading strategies, enhancing process efficiency and product quality for the commercialization of sustainable biofuels.
Optimizing biofuel production: Direct integration and co-hydroprocessing of hydrolysis lignin into oil refineries over an unsupported NiMoP catalyst Abdenour Achour, Anna Anttila, Derek Creaser, Louise Olsson Energy Conversion and Management, 2025 • NiMoP catalyst displayed high activity, enhancing the efficiency of lignin co-hydroprocessing. • Oil refineries’ solvents influenced hydroprocessing and synergistically impacted lignin-oil blends. • Funnel Plot analysis confirms enhanced performance of hydrolysis lignin multicycle co-processing. • Co-hydroprocessing of hydrolysis lignin yielded drop-in biofuels surpassing 10,000 Kcal/kg. Our study investigates the production of drop-in fuels by co-hydroprocessing solid hydrolysis lignin in a batch reactor operated in cycling mode. To simulate the blending potential with lignin oil, we utilized petroleum-derived intermediates like hexadecane and VGO. We demonstrate the significant production of blended lignin-oil through direct co-hydroprocessing of hydrolysis lignin and its hydroprocessed oil using a spent catalyst. The reactivity of hydrolysis lignin is influenced by its interaction with organic mediators in the lignin-oil blends. For hydrotreated lignin in hexadecane, we observed an 83.4 wt% yield of lignin monomers, predominantly isomeric alkane-derived, including cycloalkanes. Co-hydroprocessing with fresh lignin increased lignin-oil blend yield and reduced char formation. Additionally, the NiMoP loading significantly boosted naphtha and light gas oil yields. Co-hydroprocessing with VGO exhibited a slightly higher yield of 85.6 wt%, accompanied by a significantly lower char yield of 1.6 wt% compared to the uncatalyzed reaction, which yielded 33.7 wt% char. The enhanced reactivity and affinity with VGO resulted in improved selectivity towards naphthenes and aromatics. Overall, higher catalyst loadings promoted dealkylation and deoxygenation reactions while suppressing char formation, remarkably evident with VGO in multicycling. Interestingly, multicycling led to a higher bio-oil yield and lower char formation. Furthermore, our study suggests that co-hydroprocessing with intermittent feeding of hydrolysis lignin in a sequential operation mode can achieve deep deoxygenation, higher energy yield, and mass lignin-oil yields while maximizing the distillate range of jet and marine fuel fractions, as qualitatively evident using funnel plots.
Stabilization of fresh and aged simulated pyrolysis oil through mild hydrotreatment using noble metal catalysts Elham Nejadmoghadam, Abdenour Achour, Olov Öhrman, Muhammad Abdus Salam, Derek Creaser, Louise Olsson Energy Conversion and Management, 2024 The nature and reactivity of the oxygenates, containing different functional chemical groups, and especially carbonyl compounds, render pyrolysis oil unstable. Alterations in physical and chemical properties of pyrolysis oil during storage and the catalytic stabilization of this oil is therefore critical and is the objective of the current work. In this study, Pd/Al2O3, Pt/Al2O3, Rh/Al2O3, Re/Al2O3 and sulphided NiMo/Al2O3 catalysts were employed in the hydrotreatment (180 °C, 60 bar H2, 4 h) of simulated pyrolysis oil to examine their effect on stabilization and potential polymerization routes. Of all the catalysts used, Pd/Al2O3 with well-dispersed metal particles, and a high char-suppressing potential was the most effective catalyst. It had the highest bio-liquid yield and the highest selectivity to low molecular weight stabilized oxygenates and deoxygenated products. In addition, the acidity in the light fraction was low and a very low solid product formation was found that consisted mainly of soluble polymers composed predominantly of aliphatic compounds and sugars, whereas insoluble polymers were not fully developed char. The solid yield increased in the following order: Pd (3.3 wt%) < Rh (13.3 wt%) < NiMo (13.6 wt%) < Pt (21.5 wt%) < Re (25.8 wt%) < Blank (27.4 wt%). This trend was also accompanied by an enhanced yield of heavy oligomers in the corresponding liquid phase abundant in phenolic compounds compared to carboxylic acids and aliphatic compounds based on GPC and P-NMR analyses. The Pd loading necessary to obtain a high-quality product was also assessed, and the lower carbon loss when using catalysts with smaller contents of metal was revealed. Based on the results a detailed reaction network was proposed regarding the reactions during stabilization of sugars, aldehydes, ketones, furans, acids and phenols present in pyrolysis oil. To delve deeper into the simulated pyrolysis oil properties, it was subjected to accelerated aging. Interestingly as much as 79 % of the feed was converted during aging. According to GC/MS analysis only large oligomers were formed that could not be detected. When removing the most reactive components from the feed, i.e. the sugar and furan, the conversion was lowered to 53 %. Catalytic stabilization was conducted on the aged oil and compared with stabilization followed by aging. The results showed that the solid formation increased from 5.1 to 9.1 % when the pyrolysis oil was first aged, followed by stabilization. A suggested reason for this is the large amount of oligomers that were formed during the aging. Thus, aging before stabilization is very negative for an industrial process.
Removal of Inorganic Impurities in the Fast Pyrolysis Bio-oil Using Sorbents at Ambient Temperature Emma Olsson Månsson, Abdenour Achour, Phuoc Hoang Ho, Prakhar Arora, Olov Öhrman, Derek Creaser, Louise Olsson Energy and Fuels, 2024 High Resolution Image Download MS PowerPoint Slide Fast pyrolysis bio-oil (FPBO) sourced from residual biomass waste (such as sawdust) is a promising feedstock that may be used for biofuel production. Their inorganic elements may, however, vary and cause deactivation of the catalysts in the hydrodeoxygenation (HDO) upgrading biorefinery unit. It was found that the use of zeolite Y and strong acidic ion-exchange resins as adsorbents was almost equally efficient in lowering the concentrations of Ca from <10 to <1 ppm and of Fe, K, and Mg to <0.3 ppm in FPBO at 30 °C, atmospheric pressure, and 4 h adsorption time. The removal efficiency of zeolite and resins exceeded 85–98% (detection limit) of these particular elements. For the first time for the FPBO, phosphorus was reported as being successfully targeted by aluminum oxide, being lowered from 1 ppm to <0.1 ppm, which is a reduction of at least 90%. Characterization of the oil and sorbents suggests that the surface acidity affects the removal efficiency of these elements from FPBO. Organic compounds in the pyrolysis oil, including isopropanol, lactic acid, hydroxy acetone, furfural, guaiacol, and levoglucosan, were semiquantified using two-dimensional gas chromatography coupled with mass spectrometry (GCxGC-MS). Compared to the fresh oil, the compositions and contents of these organic compounds were not impacted significantly by the sorbents under these mild operating conditions. This research indicates that inorganic impurities present in bio-oils can be removed, and thus, they may be considered feedstocks for producing biofuels with less deactivation of HDO catalysts.
Producing upgradeable bio-oil from food bio-waste via hybrid-assisted pretreatment coupled with catalytic hydrotreatment Prabin Dhakal, Emma Olsson Månsson, Abdenour Achour Bioresource Technology Reports, 2023 Slurry food waste sourced from Renova (Gothenburg, Sweden) was investigated as a model for generating upgradeable bio-oil via a hybrid-assisted pretreatment along with a catalytic hydrotreatment process. Hybrid-assisted pretreatment has been examined for extracting and stabilizing of reactive-derived substances. For the resulting bio-crude and residual solids, the properties of the heteroatoms were also examined prior to the catalytic hydrotreatment experiments. Hybrid-assisted pretreatment is an interesting solution in that it maximizes the bio-crude yield and transfers significant amounts of the nitrogenous content (De-N ~83.3 %, dry basis) into the residual solids. Nearly 87 wt% of the oxygenated monomers were found in the obtained bio-crude, which possessed 52.0 wt% of alcohols. The highest upgradeable bio-oil of 86.0 wt% was achieved during catalytic hydrotreatment of the bio-crude and residual solids jointly: producing blends of up to 78 wt% of hydrocarbons, 14 wt% oxygenated and <6 wt% of cyclic, aromatics, N-containing components.
Stabilization of bio-oil from simulated pyrolysis oil using sulfided NiMo/Al2O3 catalyst Elham Nejadmoghadam, Abdenour Achour, Pouya Sirous-Rezaei, Muhammad Abdus Salam, Prakhar Arora, Olov Öhrman, Derek Creaser, Louise Olsson Fuel, 2023 Pyrolysis oil comprises compounds with a broad range of functional groups making its thermal/catalytic upgrading challenging due to the formation of undesired char. In this context, the current contribution addresses the thermal and catalytic hydrotreatment of a simulated pyrolysis oil containing all the representative groups of compounds under bio-oil stabilization conditions (180–300 °C, 60 bar, 4 h) using sulfided NiMo/Al2O3. The effect of reaction conditions and different oxygenated organic compounds on the yields and properties of products was compared thoroughly. Interestingly, a correlation between the presence/absence of oxygenated furan and sugar compounds was found to significantly affect the yield of liquid product containing stabilized compounds. The presence of such compound groups significantly enhances the solid formation via oligomerization and polymerization reactions. To gain further insight, the solid products were analyzed/characterized in detail to elucidate their characteristics by extracting them into a dimethyl sulfoxide (DMSO) soluble and insoluble solid fraction. It was found that in the presence of NiMo/Al2O3, increasing temperature from 180 to 300 °C enhances the formation of liquid product due to transformation of some of the soluble solids, while for experiments without the catalyst, the formation of solids was significantly higher. Oppositely, during heating up to 180 °C, no solids were found in the case without the catalyst, however the presence of the catalyst during heating resulted in solid formation due to various catalytic reactions that promoted char formation. Analysis of solids revealed that the structure of soluble solids at lower temperatures (180 °C) using the catalyst was closely related to sugar derivatives, whereas the corresponding insoluble solids with higher molecular weight were not fully char-like developed. However, at higher temperatures, the soluble and insoluble solid compositions were found to contain aliphatic compounds and fully developed char, respectively. Therefore, the stabilization of furan particularly with attached carbonyl groups and sugars derivatives in pyrolysis oil is of great importance to improve upgrading efficiency.
Modulating the Formation of Coke to Improve the Production of Light Olefins from CO2 Hydrogenation over In2O3 and SSZ-13 Catalysts Wei Di, Abdenour Achour, Phuoc Hoang Ho, Sreetama Ghosh, Oleg Pajalic, Lars Josefsson, Louise Olsson, Derek Creaser Energy and Fuels, 2023 High Resolution Image Download MS PowerPoint Slide Moderately acidic aluminophosphates (SAPOs) are often integrated with methanol synthesis catalysts for the hydrogenation of CO 2 to olefins, but they suffer from hydrothermal decomposition. Here, an alternative SSZ-13 zeolite with high hydrothermal stability is synthesized and coupled with an In 2 O 3 catalyst in a hybrid system. Its performance regarding selectivity for olefins and coke formation was investigated for CO 2 hydrogenation under varying temperatures and pressures. Various reactions occur, producing mainly CO and different hydrocarbons. The results indicate that the hydrogenation of hydrocarbons are dominant at high temperatures (around 400 °C) over SSZ-13 zeolite with a high acid density and that the coke deposition rate is slow. Polymethylbenzenes are the main coke species, but the selectivity for light olefins is low among hydrocarbons at high temperatures. However, at low temperatures (around 325 °C), and especially under high pressure (40 bar), methanol disproportionation becomes significant. This results in an increased selectivity for light olefins; however, it also leads to a rapid coke deposition, which gives inactive adamantanes as the main coke species that block the pores and cause rapid deactivation. However, after coking at 325 °C and regeneration at 400 °C under the reaction atmosphere, the accumulated adamantanes can be decomposed into smaller coke species, which reopens the channel structure and generates modulated active sites within the zeolite, resulting in a higher yield of olefins without deactivation. The performances of acidic SSZ-13 zeolites, with varying ratios of Si/Al in transient experiments, further verified that a dynamic balance exists between the formation and degradation of coke within the SSZ-13 zeolite during a long-term CO 2 hydrogenation reaction. This balance can be achieved by optimizing the reaction conditions to match the acid density of the catalyst. Using the conditions of 20 bar and 375 °C, with a H 2 to CO 2 mole ratio of 3, the results obtained for the precoked hybrid catalysts of In 2 O 3 and SSZ-13 (Si/Al = 25) exhibited very stable activity, with the selectivity for light olefins (based on hydrocarbons formed) of max. 70% after 100 h time-on-stream. This work provides new insights into the design of stable hybrid catalysts, especially the influence of a precoking process for SSZ-13 zeolite in the production of light olefins.
CO2 hydrogenation to light olefins using In2O3 and SSZ-13 catalyst − Understanding the role of zeolite acidity in olefin production Wei Di, Phuoc Hoang Ho, Abdenour Achour, Oleg Pajalic, Lars Josefsson, Louise Olsson, Derek Creaser Journal of Co2 Utilization, 2023 With the aim to explore the effect of acidic properties of zeolites in tandem catalysts on their performance for CO2 hydrogenation, two types of SSZ-13 zeolites with similar bulk composition, but different arrangements of framework Al, were prepared. Their morphology, pore structure, distribution of framework Al, surface acid strength and density, were explored. The results showed that SSZ-13 zeolites with isolated aluminum distribution could be successfully synthesized, however, they contained structural defects. During calcination, the framework underwent dealumination, resulting in weaker Brønsted acidity and lower crystallinity. The morphologies were, however, well preserved. Compared with the SSZ-13 zeolites, synthesized conventionally, these low acidity SSZ-13 zeolites with isolated aluminum were good zeolite components in bifunctional catalysts for CO2 hydrogenation to light olefins. By combining with In2O3, they exhibited better catalytic performance for light olefin production during CO2 hydrogenation at low temperatures. Na+ cation exchange was used to adjust the Brønsted acid site (BAS) density with only minor changes to the cavity structure. Comparative experiments established that the BAS density of the zeolite, rather than the framework Al distribution (BAS distribution), overwhelmingly affected catalyst stability and product selectivity. A higher acid density reduced the selectivity for light olefins, while lower acid density tended to form inert coke species leading to rapid deactivation. The ideal amount of BAS density in the bifunctional catalyst was approximately 0.25 mmol/g, which exhibited 70% selectivity for light olefins among hydrocarbons, and 74% selectivity for CO without deactivation, after 12 h reaction at 325 ℃ and 10 bar.
