Abstract
We report the thermal stability of spherically shaped cobalt-promoted molybdenum disulfide (Co/MoS2) nano-catalysts from in-situ heating under electron irradiation in the scanning transmission electron microscope (STEM) from room temperature to 550 °C ± 50 °C with aid of Fusion® holder (Protochip©, Inc.). The catalytic nanoparticles were synthesized via a hydrothermal method using sodium molybdate (Na2MoO4·2H2O) with thioacetamide (CH3CSNH2) and cobalt chloride (CoCl2) as promoter agent. The results indicate that the layered molybdenum disulfide structure with interplanar distance of ~0.62 nm remains stable even at temperatures of 550 °C, as observed in STEM mode. Subsequently, the samples were subjected to catalytic tests in a Robinson Mahoney Reactor using 30 g of Heavy Crude Oil (AGT-72) from the golden lane (Mexico’s east coast) at 50 atm using (ultrahigh purity) UHP hydrogen under 1000 rpm stirring at 350 °C for 8 h. It was found that there is no damage on the laminar stacking of Co/MoS2 with temperature, with interlayer spacing remaining at 0.62 nm; these sulfided catalytic materials led to aromatics rise of 22.65% and diminution of asphaltenes and resins by 15.87 and 3.53%, respectively.
Highlights
Layered metal sulfides such as molybdenum disulfide (MoS2 ) have been extensively used as catalytic materials in oil refineries for removal of noxious impurities including sulfur, nitrogen compounds and metals like Ni and V, mainly by means of hydrodesulfurization (HDS)and hydroprocessing (HDP) [1]
The location of metals that are promoters responsible for enhancing metallic “brim” or “edge” sites have been discussed in the literature [6,7] and some studies were made by X-ray absorption near edge structure (XANES) [8], scanning tunneling microscopy (STM) [9] as well as high-resolution transmission electron microscopy (HRTEM) [10]
For the present case a stable and less viscous crude oil remains hydrotreatment with CoMoS2 ; the instability index (CII) developed by Yet et al [27] was used by after the hydrotreatment with CoMoS2; the instability index (CII) developed by Yet et al [27] was means of the Equation (1), for measuring the asphaltenes deposition potential of hydrotreated AGT-72
Summary
Layered metal sulfides such as molybdenum disulfide (MoS2 ) have been extensively used as catalytic materials in oil refineries for removal of noxious impurities including sulfur, nitrogen compounds and metals like Ni and V, mainly by means of hydrodesulfurization (HDS)and hydroprocessing (HDP) [1]. Catalysts 2020, 10, 1239 of MoS2 is characterized by a sandwich-like stacking of layers with van der Waals-type chemical bonds between S-Mo-S along the c-direction, with an interlayer distance of 0.62 nm, which makes this particular material ideal for high temperature and tribology engineering applications. It has been considered as a semiconductor electron transport material for electronic devices [4,5]. The “in-situ” operando HRTEM techniques made it possible to achieve experimental observations that relate it to crystal growth as described by Hansen et al.; these authors directly imaged laminar
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