Special Issue Catalysis for Bitumen/Heavy Oil Upgrading and Petroleum Refining

Currently, fossil fuels continue to play a crucial role in daily life. Nevertheless, the ever-growing demand for environmentally friendly fuels has significantly reduced the proven reserves of light and medium oils. Consequently, unconventional resources such as heavy and extra-heavy oil, natural bitumen, and shale oil are now being utilized to meet the necessary fuel and energy demands. According to recent data, the reserves of these unconventional resources exceed those of light and medium oils several times over [1]. However, the primary limitations in the extraction, transportation, and processing of such heavy raw materials stem from the lack of efficient technologies.

In this Special Issue, various approaches and methods have been proposed to enhance the extraction and upgrading of heavy and extra-heavy oil from unconventional reserves [2]. These methods, known in the literature as enhanced oil recovery (EOR) techniques, are classified into different categories depending on the chosen technology: chemical methods, which involve injecting chemicals and polymers into reservoirs to alter the physicochemical properties of the oil-bearing system, thereby facilitating its extraction; the application of electromagnetic energy directed at the oil-bearing formation to reduce the viscosity of heavy oil, thereby improving its mobility and flow characteristics; and thermal enhanced oil recovery, which reduces the viscosity of the in situ raw material by injecting superheated steam or generating heat on-site by burning a portion of the oil within the formation, as seen in the in situ combustion process.

Currently, steam injection is often combined with the injection of various in situ catalysts, typically based on transition metal salts. This approach enhances the quality of the extracted oil. For instance, in the work by Mukhamatdinov et al. [3], the process of the aquathermolysis of heavy oil from the Usinsk field in the presence of an iron-based catalyst precursor was presented. The authors discovered that after treating the oil at 300 °C, the content of n-alkanes in the extracted oil increased by eight times and cycloalkanes by two times compared to the original oil. Consequently, the authors concluded that during the thermosteam treatment of oil, destruction reactions occur not only along C–N, C–S, and C–O bonds but also along C–C bonds, allowing more components of heavy oil to be involved in the upgrading process.

Nickel-containing catalysts play a pivotal role in virtually all petroleum refining processes. In this Special Issue, Urazov et al. [4] presented a study on the upgrading of heavy oil from the Zyuzeevsky field using a nickel-based catalyst precursor and hydrogen donors. Notably, the authors found that upgrading heavy oil in the presence of tetralin and a nickel catalyst precursor (nickel nitrate) increased the yield of light fractions by 36% by mass. Structural group analysis revealed that the molecular weight of average asphaltene molecules decreased significantly from 1920 to 863 a.m.u. Furthermore, using SEM, XPS, and XRD methods, the authors identified the active catalyst phases formed during the upgrading process and evaluated the influence of hydrogen donors on the formation of these phases.

In addition, the work by Zhang et al. investigated the effect of a Zn-containing catalyst and bentonite on the upgrading process of heavy oil [5]. The authors discovered that metal complexes and bentonite exhibit a co-catalytic effect; specifically, the presence of Zn reduced viscosity by more than 70%. Moreover, adding ethanol as a hydrogen donor further reduced viscosity by 84.59% compared to the original oil. This significant viscosity reduction is primarily due to the breaking of bonds in resins, asphaltenes, and high-molecular-weight hetero-organic compounds. Consequently, the study elucidated the mechanism of interaction between heavy oil components, bentonite, and the Zn-containing catalyst.

Understanding the impact of rock formations on the aquathermolysis of heavy oil is equally crucial for enhancing oil recovery efficiency and the quality of extracted oil. Minkhanov et al. conducted a study assessing the influence of carbonate porous rock on the aquathermolysis process of ultra-viscous oil using a solvent and catalyst [6]. They found that employing a catalyst with a solvent resulted in 17% greater oil displacement compared to the control experiment. The authors established that hydrothermal upgrading significantly transforms resinous and asphaltenic components, thereby generating additional amounts of saturated and aromatic hydrocarbons.

Similarly, the work by Medina et al. [7] aimed to analyze the theoretical and experimental approaches to hydrogen generation and its thermodynamic behavior during the in situ upgrading of heavy crude oil using nanoparticles. Two types of nanoparticles, cerium oxide and aluminum oxide, were evaluated for their ability to adsorb and decompose asphaltenes in a steam atmosphere. Subsequently, a nanofluid containing 500 mg/L of the most effective nanoparticles in a light oil fraction was developed and dispersed into the steam flow during steam extraction tests on two Colombian heavy crude oils. The nanoparticles enhanced oil recovery by 27% and 39% for Oil #1 and Oil #2, respectively, compared to steam injection alone. The extracted crude oil showed an increase in API gravity from 12.4° and 12.1° to 18.5° and 29.2° for Oil No. 1 and Oil No.2, respectively.

Secondary refining processes are critically important today. Catalytic cracking and hydrocracking enable the production of products with specified properties and compositions from straight-run petroleum fractions [8,9]. Consequently, the number of catalytic cracking and especially hydrocracking/hydrotreating units at refineries increases each year. This growth drives the active study and development of new catalytic systems essential for upgrading various petroleum fractions.

For instance, in the work by Tuktin B. et al. [10], the creation of catalysts with enhanced characteristics for producing high-octane gasoline with reduced sulfur content is explored. The researchers synthesized new catalytic systems based on aluminum oxide and other carriers modified with transition metals, lanthanum, and phosphorus. As a result, hydrodesulfurization of straight-run gasoline on a NiO-MoO₃-La-P-HZSM-HY-Al₂O₃ catalyst increased the octane number of the final product to 88.6 while reducing the sulfur content from 0.0088% to 0.001%. Moreover, the minimum sulfur content in the hydrotreated gasoline product, 0.0005%, was achieved with a CoO-WO₃-La-P-HZSM-HY-Al₂O₃ catalyst, which is significantly lower than other catalytic systems studied. The obtained sulfur content in the hydrotreated products fully complies with the Euro-5 standard. Furthermore, the synthesized catalysts demonstrated high activity and selectivity, resulting in the production of high-octane gasoline with a low sulfur content, compliant with international quality standards.

In the work by Moreira Ferreira J.M. et al. [11], a comprehensive review of catalysts for fluid catalytic cracking (FCC) is provided, covering their availability and characteristics over the past three decades through technical articles and patent literature. Patent literature reveals methods for introducing mesopores while preserving the internal properties of zeolites. This family of inventions claims to have increased the specific surface area of mesopores through successive acidic and basic treatments using surfactants. Nevertheless, while effective, these additional steps can complicate the process and increase production costs. Therefore, a potentially more efficient and flexible approach might involve incorporating pore-regulating agents during the compounding stage. Furthermore, there is a need to develop methods and techniques for evaluating catalyst availability in FCC, particularly those that calculate diffusion and mass transfer parameters.

In parallel with petroleum feedstocks, there is a growing focus on processes for obtaining hydrocarbon feedstocks from various food and solid waste materials [12,13]. This approach not only facilitates waste disposal but also produces additional quantities of various petrochemical products.

The research by Almuhayawi M.S. et al. [14] focuses on assessing the potential of hydrolyzing potato waste with fungi that produce amylase to enhance biogas production from potato peels through anaerobic digestion. Various fungal isolates were tested for amylase production on potato waste, with the highest amylase-producing strain selected for optimizing amylase production at large scales. This optimization aims to effectively convert potato organic matter into fermentable sugars used in anaerobic digestion. Among the tested strains, those derived from Rhizopus stolonifer were the most effective amylase producers. The highest cumulative methane yield from hydrolyzed potato peel was 65.23 ± 3.9 mL CH₄/g, with a methane production rate of 0.39 mL CH₄/h. In contrast, the highest biogas yield from non-hydrolyzed potato waste was 41.32 ± 2.15 mL CH₄/g, and the biogas production rate was 0.25 mL CH₄/h. The findings of this study could enhance the feasibility of bioprocessing potato peels using environmentally friendly enzymes through biological hydrolysis.

In the concluding article by Wang B. et al. [15], a review of homogeneous and heterogeneous catalysts for biodiesel production is presented. The article discusses the advantages and limitations of current homogeneous acid and base catalysts, as well as heteropolyacid heterogeneous catalysts and base catalysts derived from biomass. The review also covers the applications of homogeneous and heterogeneous catalytic derivatives, ionic liquids/deep eutectic solvents, and nanocatalysts/magnetic catalysts in biodiesel production. Additionally, the mechanisms and economic considerations of contemporary homogeneous acid and base catalysts are analyzed. Furthermore, the paper summarizes some challenges faced by current biodiesel catalysts and outlines future research directions.

The findings presented in this Special Issue both complement and broaden our knowledge of heavy oil upgrading with various transition metal-based catalyst precursors and the underlying mechanisms of this process. Furthermore, several contributions examine secondary processes in oil refining. Additionally, the issue delves into methods for extracting valuable petrochemical products from diverse waste materials. Consequently, these subjects require further exploration, development, and support. We would like to express our heartfelt thanks to all the anonymous reviewers, editors, and assistants who have contributed to the production of this Special Issue.