Synthesis of nanoparticles assisted by capping agents has been reported in the literature for the preparation of defined shapes and sizes of nanostructures, such as nanorods and nanowires. Additionally, in some cases, the yields obtained from such preparations are very low and further testing the activity of the particles prepared is not possible. Most of these methodologies do not produce nanoparticles or allow controlling the particle diameter. Preparation of MoS 2 particles has been performed by different methodologies including the sulfidation of oxides, the decomposition of precursors, ultrasonic irradiation, the use of emulsions, or using Layered Double Hydroxide (LDH) as hard template. Also, the kind of feed and the morphology of the particles could have an important effect on their activity. From the data presented it can be inferred that smaller particles possess higher specific activity but a correlation between conversion and particle size is not presented.Įven though smaller particles are expected to have higher activity, this may not always be the case. obtained particles of different diameters (2600–40 nm) by milling commercial MoS 2 and tested them in the hydrogenation of 1-methylnaphthalene. MoS 2 is the base of hydroprocessing catalysts however there are no reports on the effect of the particle size on the HDS activity for real feeds using unsupported (bulk) MoS 2. For this application the particle size of the catalyst should be as small as possible (preferably in the nanorange, i.e., <100 nm) in order to increase their efficiency and to be able to navigate in the porous media without causing any plugging or impairment of the reservoir. Also, in situ (or downhole) processing has been proposed as a way of producing synthetic oils from heavy oils and bitumen in the reservoir, thus reducing energy demands for field hydroprocessing and decreasing emissions. One alternative to avoid the problem posed by the use of supported porous catalysts is the application of ultradispersed catalysts, which are very small particles suspended in the feed to be processed. Even though catalytic hydroprocessing is a well-established process in the refining industry the conversion of such heavy oil fractions is challenging, from the catalytic point of view, due to metal sulfides and coke deposition in the pore mouth of the support in the commonly used Ni(Co)Mo(W)/alumina catalysts, which leads to the reduction of the catalysts effective life. More than half of the total world oil reserves are heavy oil, extra heavy oil, and bitumen, with vast deposits in Canada (Alberta province) and Venezuela (Orinoco region). The depletion of light oils supplies along with the expected increase in energy demand has shifted the attention to the exploitation and conversion of heavy oils and heavy petroleum fractions. It was found that particles with diameters around 13 nm show double the HDS activity compared with the material with micrometric particle sizes (diameter ≈ 10,000 nm). A correlation between particle size and activity is presented.
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The prepared particles were characterized by DLS, TEM, XRD, and XPS and tested in the hydrodesulfurization (HDS) of a vacuum gas oil (VGO).
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In the present work, molybdenum sulfide (MoS 2) particles with varying diameters (10000–10 nm) were prepared using polyvinylpyrrolidone as capping agent. The use of submicronic particles or nanoparticles of catalysts suspended in the feedstock may be a viable alternative to the conversion of heavy oils at refinery level or downhole (in situ upgrading). More than half of the total world oil reserves are heavy oil, extra heavy oil, and bitumen however their catalytic conversion to more valuable products is challenging.