Fuel xxx (xxxx) xxx Please cite this article as: Alcides Simão, Fuel, https://doi.org/10.1016/j.fuel.2021.122677 0016-2361/© 2021 Elsevier Ltd. All rights reserved. Full Length Article On the use of metallic nanoparticulated catalysts for in-situ oil upgrading Alcides Sim˜ ao a, b , Enrique Domínguez- ´ Alvarez a, c , Chengdong Yuan a, d, * , Muneer A. Suwaid a, d , Mikhail A. Varfolomeev a, d, * , Jorge Ancheyta a, e , Omar F. Al-mishaal a , Sergey I. Kudryashov f , Igor S. Afanasiev f , Dmitry A. Antonenko f , Oleg V. Petrashov f , Kirill A. Dubrovin f a Department of Petroleum Engineering, Kazan Federal University, Kazan 420008, Russia b Deutsches Elektronen-Synchrotron DESY, Hamburg 22607, Germany c Instituto de Química Org´ anica General, Consejo Superior de Investigaciones Científcas (IQOG-CSIC), Madrid 28006, Spain d Department of Physical Chemistry, Kazan Federal University, Kazan 420008, Russia e Instituto Mexicano del Petr´ oleo, Eje Central L´ azaro C´ ardenas 152, Mexico City 07730, Mexico f JSC Zarubezhneft, Moscow 101990, Russian Federation A R T I C L E INFO Keywords: Heavy oil In-situ upgrading Catalyst Nanoparticle ABSTRACT An exhaustive review on the application of different metal-based nanoparticles for the upgrading of heavy oils has been performed. Particular emphasis has been put on those catalysts used for in-situ upgrading using various thermal treatment methods aiming at extracting heavy oils in a more effective manner. Different types of cat- alysts have been identifed, such as monometallic (Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Ce, and W), non-supported bimetallic (Ti/Zr), non-supported polymetallic (various mixtures of Co, Mo, Ni, W, Al, Zn, Cu), and supported (various metals on silica, alumina, carbon, zeolite, biogenic particles, complex inorganic and organic). Due to the great diversity of nanoparticulated catalysts (type, metal content, synthesis procedure, particle size) and evaluation conditions (experimental setup, reaction conditions, type of feed), it is not possible to make a direct comparison on their performance. Some results are highlighted on the effectiveness of the catalysts for heavy oil upgrading in terms of asphaltene adsorption, viscosity reduction, increase of API gravity, and coke formation. The reviewed literature indicates the need for more research on this topic as to develop more effective catalysts not only for increasing the recovery factor but also for permanent upgrading of the quality of heavy and extra-heavy oil. 1. Introduction Growth in the world economy requires an increase in global energy demand. Oil remains the world’s leading fuel for now and it remains needed for at least decades despite the fact that renewables together with nuclear and hydroelectric power has boosted a fast increase in recent years [1]. Even though it is predicted that the oil demand will fall soon, the faster decline in the existing production (mostly conventional light oil resources) indicates that signifcant investment is still required to increase new oil production from alternative unconventional sources (BP Energy Outlook 2020 edition) [2]. Heavy oil, as one of the unconventional sources, accounts for a large portion of the global oil reserves (about 60–70 % of the total proved oil reserves). It is considered as an important alternative and perhaps the most readily available oil resource to complement the conventional fossil fuels and meet near- and longer-term demands [2-4]. Nevertheless, heavy oil is well-known for its high viscosity and density that lead to its poor fow ability [5]. Therefore, it is not easy to extract this type of heavy oil. Those common recovery methods widely used for conven- tional light oils (i.e. water fooding and gas injection) are less effective for the extraction of heavy oil. Currently, the main technologies for heavy oil recovery are thermal methods, including in-situ combustion (ISC) and steam injection (steam-assisted gravity drainage (SAGD), cy- clic steam injection (CSC), steam fooding, etc.) [4,6,7], where “thermal effect” generated by combustion or steam is expected to reduce the viscosity, which consequently improves the mobility of heavy oil [8-11]. In the earliest thoughts, the role of temperature increase played in vis- cosity reduction was given more emphasis [3]. However, after some feld application and laboratory studies, other technical and economic challenges were exposed. For example, in ISC processes, the oxidation of * Corresponding authors at: Department of Petroleum Engineering, Kazan Federal University, Kazan 420008, Russia. E-mail addresses: megycd@163.com (C. Yuan), mikhail.varfolomeev@kpfu.ru (M.A. Varfolomeev). Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel https://doi.org/10.1016/j.fuel.2021.122677 Received 13 August 2021; Received in revised form 9 November 2021; Accepted 19 November 2021