Hydrotreating of bitumen-derived gas oils is essential for producing clean fuels, but the process is challenged by fines deposition, which leads to progressive pressure drop buildup and premature reactor shutdown. Pressure drop correlations can serve as valuable tools for anticipating such buildups. However, existing correlations, including the Ergun equation and its two-phase extensions, do not account for the hydrodynamic effects of fines deposition, thereby limiting their applicability. In this study, an Ergun-based model was developed to predict pressure drop during fines deposition. The model integrates a two-phase multiplier with a time-dependent fines deposition multiplier, both expressed as functions of operating conditions and packing properties. Model coefficients were estimated via non-linear regression using experimental data spanning temperatures of 350-390 °C, gas velocities of 0.03-0.10m/s, packing sizes of 2.1-2.7mm and fines sizes of 0.2-20µm. The integrated model demonstrated strong predictive capability across the examined range of conditions. Sensitivity analysis revealed that fines size had the strongest individual influence on pressure drop buildup, whereas gas velocity and temperature dominated when interaction effects were considered. The resulting framework provides a predictive tool for estimating pressure drop during fines deposition and offers valuable insights for mitigation strategies when processing fines-laden oil feeds.

Fines deposition is a persistent operational challenge in the hydrotreating of bitumen-derived gas oils, resulting in pressure drop buildup and early reactor shutdowns. Identifying the key drivers of fines deposition is crucial for understanding its mechanisms and developing targeted mitigation strategies. Recognizing temperature as a key hydrotreating process parameter, this study investigated its role in fines deposition using reactor temperature profiles representative of industrial practice. Hydrotreating tests were carried out at temperatures from 350 degrees C to 390 degrees C with fines-laden light gas oil in a three-zone trickle-bed reactor. Results showed that under uniform temperature conditions, pressure drop buildup mainly occurred in the upper reactor zones and accelerated significantly as temperature increased. This trend was linked to temperature-driven changes in the fines' surface characteristics, particularly asphaltene desorption, which reduced oleophilicity and promoted particle settling. At 350 degrees C and 370 degrees C, deposition was primarily physical, whereas at 390 degrees C, it was revealed that incipient dehydroxylation of the fines promoted chemical anchoring to the catalyst's surface, which caused deactivation. In the case of increasing and dynamic temperature profiles, the fines were distributed across all reactor zones, which delayed severe plugging and thus, these profiles offered extended run times compared to uniform temperature profiles. Overall, the results of this study provide critical insights into the influence of temperature on fines deposition and highlight practical strategies for enhancing catalyst longevity and reactor performance.

Fines deposition poses a significant challenge in the hydrotreating of bitumen-derived gas oils, leading to increased pressure drop and premature reactor shutdown. This study systematically investigated the influence of fine particle size on deposition dynamics using a three-zone trickle bed reactor loaded with NiMo/gamma-Al2O3 catalysts. Cold and hot flow pressure drop tests were performed with oil feedstocks containing 4000 ppm of kaolin clay fines with 0.2 & micro;m, 1 & micro;m and 20 & micro;m sizes. Results from both flow tests demonstrated that increasing fines size accelerated pressure drop buildup and this was consistent with mass balance analyses that showed deposition rates of 0.6 g/day, 0.8 g/day and 2.1 g/day for the respective fine particle sizes. A regression model, which was developed to estimate pressure drop buildup as a function of fine particle size and time, showed excellent fit to the experimental data (Adjusted R2 = 0.95). The model identified significant influences of fine particle size and its interaction with time on deposition behavior, with larger particles driving more rapid increases over time. Despite fines deposition occurring, the catalyst's hydrodesulfurization, hydrodenitrogenation and hydrodearomatization activities remained largely unchanged, indicating that the deposition was primarily driven by physical interactions. Altogether, the findings suggest that implementing selective feed filtration and other pretreatment strategies can effectively mitigate fines deposition, so that hydrotreating operations can be run for their full intended durations without interruption.

Abstract Hydrotreating of bitumen-derived oils is hindered by fines deposition, which causes pressure drop buildup and premature reactor shutdown. While the hydrodynamic effects of fines deposition are well established, its role in catalyst deactivation remains poorly understood. In this study, a three-zone reactor was used to investigate the mechanisms of catalyst deactivation under industrially relevant temperature gradients. Pressure drop monitoring, catalytic activity evaluation, and postreaction characterization showed that fines deposition occurred sequentially, beginning in the hottest bottom zone (390 °C) before progressing upward to the middle (370 °C) and top (350 °C) zones. At 390 °C, fines chemically interacted with the catalyst support to form linkages that caused catalyst activity loss. In contrast, deposition at 350–370 °C was primarily physical, with catalyst deactivation occurring only after prolonged accumulation produced dense deposits and external mass transfer limitations. These findings provide guidance for improving reactor operability and catalyst lifespan.

Blending biocrude with petroleum fuels can offset the mounting fossil fuel dependency and resultant environmental emissions. Co-processing such blend stocks within existing refineries offers a cost-effective pathway compared to constructing stand-alone biorefineries. That notwithstanding, the direct implementation of this approach in the refinery is limited by the poor miscibility between the highly oxygenated biocrude feedstock and the hydrocarbon-rich petroleum intermediates. This study attempts to evaluate two strategies to address this challenge using oilseed meal-derived biocrude and bitumen-derived heavy gas oil (HGO). First, hydrothermal co-liquefaction (HTCL) of biomass with HGO was performed at 300 degrees C and 10 MPa (1:1 mass ratio), producing highly uniform blends with substantially reduced oxygen content (3.4-5.4 wt%) relative to biomass-only HTL (8.2-9.5 wt%). Second, direct blending was optimized using a Central Composite Design and response surface methodology, with temperature (25-125 degrees C), blending time (10-90 min), and stirrer speed (200-600 rpm) as factors and a microscopic image-based miscibility index as the response. For the direct blending method, the quartic model achieved excellent fit (R2 = 0.999), with optimal blending conditions of 110 degrees C, 38 min, and 436 rpm; yielding a predicted miscibility index of 0.994. Temperature was the dominant parameter, and significant miscibility was achieved at biocrude loadings up to 10 wt%. Together, these approaches demonstrate practical pathways for low-level biocrude integration into existing refinery hydrotreating operations.

Fines deposition presents a significant problem during the hydrotreating of bitumen-derived gas oils. The accumulation of fines leads to reactor clogging and consequently, pressure drop buildup. At critical levels, the hydrotreating reactor must be prematurely shutdown, resulting in substantial economic losses for refineries. Hence, research into finding measures to address fines deposition is crucial and of interest to stakeholders in the refining industry. This research explored the effects of catalyst size and bed arrangement on fines deposition, with the goal of identifying strategies to obtain longer hydrotreating run times. Cold and hot flow fines deposition tests were conducted in three-zone reactors using NiMo/gamma-Al2O3 catalysts, with sizes ranging from 1.3 to 2.5 mm. Under cold flow conditions, maximum fines deposition was reached in 12, 14, and 25 days for 1.3, 1.6, and 2.5 mm catalyst sizes, respectively. For the hot flow tests, maximum fines deposition occurred in 15, 17, and 28 days for 1.3, 1.6, and 2.5 mm catalyst sizes, respectively. Thus, both flow tests suggested that reducing catalyst size accelerated fines deposition, primarily due to straining. However, when the catalyst bed was arranged with decreasing size from top to bottom of the reactor, the time to reach maximum fines deposition increased to 28 days (cold flow) and 34 days (hot flow). Therefore, configuring the catalyst bed to have a downward gradient of decreasing catalyst size is proposed as a potential strategy to extend hydrotreating run times.

Fines deposition is a perennial problem in the hydrotreating industry. It results in reactor fouling and pressure drop build-up, leading to premature reactor shutdown. This study investigated the impact of gas flux, a key hydrotreating parameter, on fines deposition. Cold and hot flow accelerated fines deposition tests were conducted using three-zone reactor units under varying gas-to-oil ratios (GOR) of 300, 600, and 900 v/v, representing low, medium, and high gas flux conditions, respectively. The hot flow tests revealed that maximum fines deposition occurred in 26, 15, and 10 days for low, medium, and high gas flux tests, respectively. Thus, increasing gas flux increased the rate of fines deposition, and this was ascribed to a combination of flocculation, sedimentation, and inertial impaction mechanisms. Based on the findings, cautiously reducing the gas flux could be a potential strategy to minimize fine deposition and enhance reactor efficiency during hydrotreating.

The reduction in conventional oil resources, coupled with the predicted increase in oil demand in the coming years, has necessitated the exploration of unconventional reserves like oil sands. However, crude oil from these unconventional sources consists of large amounts of impurities like sulfur and nitrogen, which need to be removed via upgrading processes like hydrotreating. Alumina-supported catalysts are currently the predominantly used catalysts for hydrotreating but the strong metal-support interactions present in these catalysts inhibit their activity, thereby limiting their efficiency. This paper reviews recent progress made to develop novel catalysts with different supports, which can have better hydrotreating conversions than alumina-supported catalysts. From the several literatures reviewed, it was noted that, finding the best catalysts with improved efficiency came with challenges related to getting the optimal metal-support combinations and interactions, support-addition techniques and metal-loading methods, all of which have significant impacts on the catalyst’s activity. Some supports such as mesoporous titania-alumina, zirconia-alumina, multi-walled carbon nanotubes and ethylenediamine-functionalized graphene were demonstrated to have promising potential when used as carriers for NiMo and CoMo metals. It was suggested that the feasibility of these catalysts for use in commercial operations to obtain maximum conversions should be considered.

A review was performed on the topic of oil sand production and processing, focusing on the sources, issues, and mitigation methods used industrially for the treatment of foulants. This involved a stepwise approach through the bitumen upgrading process, where each main process unit had types of foulants avoided, along with types of chemicals or processes used industrially for their treatment. From this approach, several chemicals were identified for reducing various types of foulants, including corrosion inhibitors, antioxidants, dispersants, or pour point depressants. Additionally, various operating conditions that can influence fouling were discussed, along with changes that can be made to those conditions to reduce fouling. It is hoped that, by further clarifying the topic of oil sands foulants, improved facility design and/or operation can lead to improved efficiency, economics, and fewer environmental impacts.

Bitumen-derived gas oils that enter hydrotreaters contain fine solids such as minerals, heavy metals, and coke. The deposition of these fines will eventually restrict the flow and result in pressure buildup across the hydrotreater, which eventually necessitate the premature shutting down of the reactor system. To determine if certain types of fine particles had a greater detriment to the hydrotreating process, a series of experiments were performed by accelerated fine deposition in a trickle bed catalytic reactor under industrial conditions using bitumen-derived light gas oil. Kaolinite, montmorillonite, pyrite, and petroleum coke fines had no significant impact on the catalyst activity and catalyst deactivation toward hydrodenitrogena-tion (HDN), hydrodesulfurization (HDS), and hydrodearomatization. Unlike the above fines, iron(III)oxide was found to convert into FeS under hydrotreating conditions, which provided a promoting effect for HDN and HDS reactions. When comparing the trends in pressure drop across the catalyst bed, there was a delayed period during the initial fine deposition where no change in pressure drop was observed, followed by an exponential increase in pressure due to the decrease in bed porosity. The difference found between these fines was the length of this delayed period, with iron(III)oxide and petroleum coke having the longest periods of no pressure growth. From inductively coupled plasma, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller analysis of the fresh and spent catalysts, it was determined that the deposition of all fines occurred within the packing material in the preheating zone, with only petroleum coke and iron(III)oxide fines being found on the surface of the catalysts.

The by-products collected during the synthesis of carbon nanohorns via the arc discharge synthesis method is comprised of other carbon particles (OCP). At a hydrotreating operating temperature of 370°C, preliminary investigations using a bimetallic catalyst with support originating from the fine fractions of other carbon particles (OCP f ) and containing 13 wt% Mo and 2.5 wt% Ni resulted in an HDS and HDN conversion of 78 and 25%, respectively. Variation of metal compositions in catalyst formulation and its impact on hydrotreating activity was therefore considered in this study to enhance the hydrotreating activity of OCP f –supported catalyst, and to determine if the best NiMo/OCP f catalyst achieved from this study could be a viable catalyst for hydrotreating applications. The co-incipient wetness impregnation was used in preparing series of hydrotreating catalysts with Ni and Mo loadings within the range of (2.5–5.0 wt%) and (13–26 wt%) respectively. Overall, the catalyst samples with maximum Ni loading of 5.0 wt% and Mo loadings of either 13 or 19 wt% showed higher dispersion and the ability to form a Type II Ni-Mo-S phase with enhanced activity. The effects of metal compositions on both HDS and HDN activities were correlated with their physicochemical properties.

Heavy gas oil feed in a packed bed reactor was used to study the influence of temperature (370-400 degrees C), pressure (1000-1400 psig), and liquid hourly space velocity (LHSV) (0.5-2 h(-1)) on the deposition of fines (asphaltene-coated kaolin) during hydrotreating. The effects of surface charge on fines deposition on the catalyst bed were also investigated. The study showed that LHSV was the only factor with an individual effect on deposition, where increasing LHSV resulted in a decrease in fines deposition. Contrastingly, pressure and temperature showed interactive effects with a combination of high temperature (>380 degrees C) and low pressure (<1250 psig) or low temperature (<390 degrees C) and high pressure (>1150 psig), resulting in minimal deposition. These combinations of temperature and pressure also coincided with the region of high hydrodesulfurization, suggesting the impact of fines deposition on catalyst activity. Opposite surface charges possessed by fines and the catalyst created an attractive force that contributed to fines deposition during hydrotreating.

The effect of catalyst acidity on fines deposition during hydrotreating of bitumen-derived heavy gas oil (HGO) was investigated in a batch reactor using a series of mesoporous NiMo/Ti-Al2O3 catalysts. Experimental design based on a three-factor optimal (custom) response surface methodology was performed and analyzed, considering temperature, catalyst acidity (Ti/Al), and asphaltene coatings in the ranges of 360-380 degrees C, 0-0.05, and 0-1084 ppm, respectively. The results of the experiments indicated that fines deposition was independent of the hydrotreating reaction temperature range of 360-380 degrees C. Additionally, lower deposition of fines was recorded with increasing catalyst acidity. In terms of asphaltene coating, fines with higher asphaltene coating showed higher deposition in the catalyst bed. Analysis of the spent catalyst showed a decrease in the weak acidic sites after hydrotreating. Finally, within the range of process parameters evaluated, a mathematical model with a correlation accuracy of 85% was developed to predict the extent of fines deposition with variable catalyst acidity. Models for hydrodesulfurization and hydrodenitrogenation with R-2 values of 0.93 and 0.82, respectively, were also developed.

Carbon nanohorns (CNH), other carbon particles (OCP), fine fractions of other carbon particles (OCPf), carbon nanotubes (CNT), and gamma-alumina (gamma-Al2O3) were utilized as support materials for the Ni-Mo catalyst in this study to test the influence of the support on hydrotreating efficiency using light gas oil (LGO) and identify the cause of disparity in activity from these various catalyst supports. OCP and OCPf are the main byproducts obtained during the production of CNH. The influence of the support on the hydrotreating catalyst is significant and includes enhancement of textural properties, active phase dispersion, and catalyst reducibility. The hydrodenitrogenation activities of all of the different supported catalysts with light gas oil are presented and correlated with their physicochemical properties. Among all of the carbon-supported catalysts used, the NiMo/ CNH catalyst exhibited outstanding physicochemical properties, and as such, its hydrodesulfurization activity of 89% dominated that of NiMo/OCPf (78%), NiMo/OCP (67%), and NiMo/CNT (73%) catalysts. The pore volume, pore diameter, and surface area of the NiMo/CNH catalyst was 0.42 cm(3)/g, 10.9 nm, and 350 m(2)/g, respectively. The percentage metal dispersion of the NiMo/CNH catalyst was 8.0% and was about twice that of the NiMo/OCP f and NiMo/CNT catalysts. X-ray absorption spectroscopy (XAS) analysis confirmed that the carbon-supported catalysts exhibited a distorted octahedral Mo coordination environment, whereas the NiMo/gamma-Al2O3 catalyst exhibited a mixture of octahedral and tetrahedral Mo environment. From XAS results, it was apparent that the possession of a Mo octahedral coordination environment does not always translate to attainment of highest hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities.

Mesoporous supports with a T-acceptor were developed for adsorptive desulfurization of petroleum distillates. Pristine mesoporous Al2O3 and Ti-substituted mesoporous Al2O3 were synthesized and used as supports along with commercial gamma-Al2O3 for immobilizing ethylenediamine (EDA) linker followed by the pi-acceptor, 2, 7-Dinitro-9-fluorenone (DNF). The adsorbents and supports were characterized using BET, FTIR, TGA techniques to ascertain their physicochemical properties. The extent of pi-acceptor functionalization on supports was characterized using XRD, TGA and XPS techniques. Adsorbents were examined for the desulfurization of a model oil feed with 500 ppm of sulfur. The commercial gamma-Al2O3-EDA-DNF adsorbent successfully removed 90.4 wt% of sulfur. The substitution of Ti in the framework of mesoporous Al2O3 did not promote its desulfurization efficiency. The higher desulfurization activity of the commercial Al2O3 based adsorbent than that of others is attributed to its textural properties.

A new multiphase fluid dynamics model for a commercial ebullated bed hydroprocessor was developed. The impact of the gas-liquid distribution system is now explicitly included through new submodels for bubble size distribution and drag coefficients. The size distribution submodel is coupled with the existing gas-liquid separation submodel to better predict recycled gas and liquid flow rates. Either the mass of the catalyst inventory or recycle pump curve can be specified as inputs to converge the model; the former is not always well known during operation in which case the latter can be used after making a few assumptions. A sensitivity analysis was performed to study the impact of fresh treat gas velocity, catalyst mass, phase properties, and reactor internals on recycled gas and liquid flow rates, bubble size distribution, and bed liquid holdup. A 0.2 mm shift in bubble size distribution toward larger sizes was found to significantly increase bed liquid holdup, suggesting that distributor modification/redesign could help improve the capacity of the hydroprocessor.

This study investigated the effect of pressure on individual bubble drag for a contaminated polydisperse swarm. Bubble size distributions and individual bubble drag coefficients were experimentally determined at four different pressures (0.14, 0.46, 2.00, 4.00 MPa) to establish if there is a relationship between bubble size distribution and individual drag coefficient and quantify the effect of pressure on bubble drag. The analysis is limited to bubbles with diameters between 0.4 and 6 mm. Individual bubble drag coefficients were found to decrease with pressure at constant gas hold-up. This effect is attributed to changes in bubble size distribution driven by pressure. As pressure increased, the bubble size distribution shifted towards smaller sizes. Relatively speaking, these smaller bubbles induce marginal liquid perturbations and could potentially dampen turbulence from other sources, resulting in reduced drag. A new drag model has been proposed to improve CFD simulation of bubble columns at elevated pressures. (c) 2020 Elsevier Ltd. All rights reserved.

Mesoporous alumina-based adsorbents consisting of a π-electron acceptor complexing agent (2,7-dinitro-9-fluorenone) were synthesized and characterized. Adsorbents were screened for the removal of sulfur compounds from a model ultra-low-sulfur diesel fuel via a charge transfer complex (CTC) mechanism. The sulfur adsorption isotherms and kinetics were examined. The kinetics of sulfur adsorption followed a pseudo-second-order model with the CTC adsorbents. Among the three adsorbents screened, a commercial γ-Al2O3 CTC adsorbent showed the highest desulfurization in a short-run period. The regeneration of spent adsorbent was studied with three different polar solvents, namely chloroform, dichloromethane, and carbon tetrachloride. Dichloromethane was found to be the most suitable solvent for extracting a major portion of sulfur compounds occupied in the pores of the spent adsorbent. γ-Al2O3 CTC adsorbent can be reused after regeneration. Thermodynamic parameters such as Ea, ΔG, ΔH, and ΔS provided a better insight into the adsorption process.

Depleting conventional oil sources make the exploration of the unconventional ones significant. The term "hydrotreating" is used to describe the process of the removal of impurities such as nitrogen and sulfur from light gas oil and heavy gas oil streams at high pressure and temperature and in the presence of a catalyst. However, there are several hindrances in the process due to the inherent nature of bitumen-derived gas oil. This review, particularly, focuses on significant concepts in the hydrotreating of gas oil with special emphasis on the nature of fine particles present in bitumen-derived gas oil and the behavior of these particles during hydrotreating. A possibility of addressing the problem of fine particle deposition can significantly influence the efficiency of the industrial hydrotreating of bitumen-derived gas oils and this is the major motive behind the compilation of this chapter. Several technical challenges encountered in the hydrotreating of bitumen-derived gas oil due to fine particle accumulation are comprehensively discussed. The significant impact of fines on the process of industrial hydrotreating brings relevance to a review that focuses on this topic along with the details of all the research contributions made to this field.

A study has been carried out in detail to measure the effects of the removal of nitrogen compounds on the hydrotreatment of light gas oil (LGO) using a synthesized polymer consisting of a polymer support, copolymer of glycidyl methacrylate and ethylene glycol dimethacrylate (PGMA-co-EDGMA), a pi-acceptor moiety (2,4,5,7-tetranitrofluorenone, TENF), and a three-carbon linker (diaminopropane, DAP (3)). The primary focus of this paper is first to study the effects of selectively removing nitrogen compounds on the hydrotreatment of LGOs. Removal of these catalyst inhibiting and poisoning compounds prior to hydrotreatment will help in improving the hydroprocessing efficiency as well as in reducing the chemical fouling, thus improving the catalyst life. Second, the effectiveness on the reusability of bulk polymer after regeneration was studied. To achieve this, nitrogen compounds from LGO were adsorbed on the synthesized polymer by mixing polymer and LGO. The polymer was regenerated by washing with toluene in a Soxhlet apparatus. Hydrotreating experiments were performed in a pilot scale trickle-bed reactor. To create a baseline for monitoring the hydrotreatment activity, untreated LGO (without polymer adsorption) was hydrotreated with a commercial NiMo/gamma-Al2O3 catalyst and analyzed for nitrogen, sulfur, and aromatics content. The pretreated feed (with polymer adsorption) was also hydrotreated, and the results were compared. The results show that prior selective removal of nitrogen compounds improved overall hydrotreatment activity and resulted in additional decrease of 18.7%, 8.3%, and 9.4% in total nitrogen, sulfur, and aromatics content, respectively.