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The complexity of designing and optimizing vegetable oil hydrotreating reactors lies in describing multiple phenomena, including heat and mass transfer, hydrogen consumption, pressure drop, and a complicated network of highly exothermic reactions. This study intends to analyze the behavior of a vegetable oil hydroprocessing unit in a commercial environment via modeling and simulation techniques. In order to describe the three-phase (gas-liquid-solid) system in a detailed manner, a commercial-scale reactor model having multiple catalyst beds and inter-bed quench gas injections was constructed accounting for the heat and mass transfer between phases, the dynamic response of the system, the variation in gas phase velocity, and intraparticle effects. Based on dynamic reactor simulations, quench gas injection strategies were proposed to control the reactor temperature profile and yield of the desired products. Simulation results showed that the selection of a feed inlet temperature plays a major role in reactor overheating and quench injections must start as soon as the reactant stream reaches the inter-bed quench zone to stabilize reactor temperature more rapidly during start-up. In addition, the lengths of the catalyst beds need to be adjusted such that the heat released by chemical reactions is properly distributed along the reactor. The results overall provide useful information for the design and optimization of commercial-scale catalyst bed configurations for hydrotreating renewable feedstock. In particular, it is highlighted that by means of an appropriate gas quenching configuration, reactor temperature can be adequately controlled, allowing higher yields of green diesel. • Mathematical model predicts the behavior of reactor for vegetable oil hydroprocessing • Operating conditions and catalyst bed layout must be carefully selected • Quench injections must start once the maximum permissible temperature is reached • Quench injections avoid the overheating of vegetable oil hydrotreating reactor [ABSTRACT FROM AUTHOR]

• A review of hydroisomerization technologies for biojet fuel production is provided. • Hydroisomerization is needed for improving the cold flow properties of fuels. • Strengths and limitations were identified for various hydroisomerization catalysts. • Low cracking activity and tolerance to oxygen are critical catalyst attributes. • Biogenic feedstock pretreatment to remove catalyst poisons may be required. An overview of the recent advances in the field of catalytic hydroisomerization of hydrocarbons is presented in this article, with a particular focus on promising technologies for the production of sustainable aviation fuels or biojet fuels. Processing of biogenic feedstocks, such as waste vegetable oils and animal fats, to produce biofuels yields hydrocarbons containing linear paraffins. Abundance of these linear paraffins leads to poor cold flow properties in the resultant fuels, requiring further refining in order to meet the jet fuel specifications. Catalytic hydroisomerization is an effective approach that transforms linear paraffins into branched ones or isoparaffins, thereby improving cold flow properties. Adapting this technology from its conventional use in petroleum refineries to biorefining requires technological improvements. In principle, this technology could be modified for use in aviation biofuel refining by adjusting the catalyst's formulation based on the chemical characteristics of the unrefined biofuel and finding the optimum working conditions for such new catalysts. A major challenge in this area is the development of an efficient catalyst capable of selectively isomerizing long-chain linear paraffins without much cracking and with tolerance to impurities in the biofuel. The review presented here ultimately aims at identifying suitable catalyst candidates that can be adapted for refining a range of biogenic feedstocks into jet fuels. The desirable catalyst attributes, such as resistance to contaminants, balanced acidity to minimize cracking, and selectivity towards reactions that lead to cold flow property improvement, are examined. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Vacuum residue is represented as a continuum in molecular weight and aromaticity. • Molecular structures are formulated consistently with vacuum residue chemistry. • SARA fractions are distinguished using distinctive structural descriptors. • Island- and archipelago-type resins and asphaltenes are considered. • Visualization of detailed molecular distributions in bitumen vacuum residue is presented. Abstract Vacuum residue is the most diverse and structurally complex fraction of petroleum. In this work, we develop a representation of the molecular composition of this petroleum fraction. The underlying assumption is that vacuum residue is a continuum in molecular structure that can be described using probability distribution functions. The structural definition of SARA classes (saturates, aromatics, resins, and asphaltenes) is formulated in consistency with recent findings in petroleomics and the chemistry of thermal cracking or conversion. Island- and archipelago-type structures are considered in the representation of resins and asphaltenes. The systematic assembly of residue molecules is executed using stochastic algorithms. The model is implemented with good results in simulating a vacuum residue from oil sand bitumen. The simulation allows visualization of detailed molecular distributions in vacuum residue and its SARA fractions. The model also gives acceptable predictions for the properties of the maltene and asphaltene fractions of the residue sample. [ABSTRACT FROM AUTHOR]

Highlights • Oil sands bitumen is partially upgraded in a fixed-bed hydroprocessing reactor. • Pipeline transportation specifications are met at 52% vacuum residue conversion. • The process favors formation of light gas oil fractions (220–343 °C). • Sulfur removal exceeds 89% in on-specification products. • Hydrogen consumption is around 1005 scf/bbl when the product targets are met. Abstract Partial upgrading is an approach to processing Canadian oil sands bitumen with the objective to produce a synthetic crude oil that meets specifications for pipeline transportation (API Gravity of 19° and viscosity of 350 cSt at 7 °C). Most partial upgrading technologies under development rely predominantly on thermal conversion processes combined with additional steps such as solvent deasphalting. Owing to the chemistry of thermal conversion, the liquid product resulting from this route tends to be unstable and susceptible to potential operational issues in pipeline transportation and subsequent refining. Hydroprocessing represents another pathway for bitumen partial upgrading, with the advantage of being able to minimize product instability concerns and achieve the target product quality. The objective of this study was to evaluate the feasibility of using mild hydroprocessing in a fixed-bed reactor for the partial upgrading of Canadian bitumen. Experiments were conducted in a pilot plant that underwent various modifications to handle raw bitumen. Systematic tests at different operating conditions were completed in a time period of 1394 catalyst hours without experiencing any plugging issues. It was demonstrated that stable and pipeline-ready product can be produced at residue conversions of 52.4 wt% or above and with a hydrogen consumption level of about 1005 scf/bbl. Future research must be directed at optimizing the process to reduce hydrogen consumption and investigating catalyst deactivation patterns. [ABSTRACT FROM AUTHOR]

• Fixed-bed hydroprocessing is proposed as an approach for bitumen partial upgrading. • Pipeline specifications are met at approximately 50 wt% conversion of 525 °C+. • The process yields on-specification product over 1096 h of continuous operation. • Pressure drop buildup in the reactor is a limiting factor for long-term operation. • On-specification product shows promising characteristics for refining into fuels. Bitumen partial upgrading refers to a prospective direction in the processing of Canadian bitumen where its quality is improved just enough to meet pipeline specifications. Fixed-bed hydroprocessing is an approach with the potential to achieve this objective, outside the mainstream concept of combining visbreaking and solvent deasphalting. In continuation of previous work where we examined the fitness of purpose of fixed-bed hydroprocessing to partially upgrade oil sands bitumen, in this study we investigate the stability of the hydroprocessing catalyst system when exposed to working conditions over an extended period of operation. The trial campaign was conducted in a continuous pilot plant having a fixed-bed reactor packed with a dual catalyst system. In the first part of the experimental program, conditions were scouted to find the operating window that enabled us to meet the pipeline specifications for API gravity (19°API) and viscosity (350 cSt at 7 °C). Following completion of these tests, the stability of the catalyst over time was assessed under conditions such that the desired product quality was met. It was established that on-specification partially upgraded bitumen could be produced at conditions that permitted the attainment of residue (525 °C+) conversion levels of nearly 50%, with hydrogen consumption levels of 900–1000 scf/bbl. The catalyst system was stable over 1096 h of continuous operation (6.5 weeks), yielding on-specification product, but this was accompanied by a visible pressure drop buildup in the reactor. Characterization of the on-specification product showed increased yields of quality middle distillates and vacuum gas oil fractions. [ABSTRACT FROM AUTHOR]

• Methods to measure the mixing compatibilities of biocrude with petroleum are presented. • Analytical methods to measure biogenic carbon content in fuel blends are discussed. • Application/review/use of chromatography and spectroscopy in characterizing biocrude and their blends from co-processing is summarized. • Role and future of characterization of biocrudes and co-processing blends with HRMS techniques in discussed. Biocrudes are complex mixtures with significant amounts of oxygenates (<40 wt% oxygen) and their chemistry is different from that of petroleum. Therefore, co-processing of biocrudes with petroleum fractions in existing refineries is challenging and may require pre-treatment of biocrude. A thorough characterization can aid in understanding the chemical composition of biocrude and its blends with petroleum (i) to identify the possible problematic components for co-processing, and (ii) to identify the economically feasible route to pre-treat and co-process the biocrudes. This review provides an overview of the principles, methodology, and applications of various analytical strategies and techniques used to characterize biocrudes, their blends with petroleum, and co-processed products. The methods to test, predict and aid mixing compatibility of biocrude with petroleum were also discussed. The manuscript is organized in the following segments (i) analysis using wet chemistry, (ii) analytical instrumentation methods such as nuclear magnetic resonance (NMR), gas chromatography (GC), and Fourier transformed infra-red spectroscopy (FTIR), (iii) utilization of advanced methods including two dimensional GC, liquid chromatography (LC) and NMR, and high-resolution mass spectroscopy (HRMS) to provide the detailed composition of biocrudes and their blends at the molecular level, and (iv) methods to determine the biogenic carbon in the co-processed products. In addition, the information presented in this review will serve as a valuable resource for scientists handling complex biocrude and their co-processed products. A discussion of further research strategies and goals is also presented. [ABSTRACT FROM AUTHOR]