In Situ Upgrading of Athabasca Bitumen Using Multimetallic Ultradispersed Nanocatalysts in an Oil Sands Packed-Bed Column: Part 2. Solid Analysis and Gaseous Product Distribution

摘要

Thermal cracking of Athabasca bitumen was carried out in an oilsand packed-bed column, in the presence and absence of in situ prepared trimetallic nanocatalysts at a pressure of 3.5 MPa, residence time of 36 h, and temperatures of 320 and 340 ℃. In this part of the study, the effects of reaction severity (time and temperature) as well as the presence of nanocatalysts in packed media on solid and gaseous products were investigated. Results showed that the presence of trimetallic nanocatalysts enhanced the hydrogenation reactions and, consequently, led to significant reduction of coke formation (51.3%) and CO_2 emission reduction. Further, the analysis of the gaseous products and deposited solids confirmed the previous findings reported in part 1 (10.1021/ef401716h) of this study. The accumulative volume of coke precursor gases, such as ethylene and propylene, increased with the reaction severity. However, reaction severity has no significant effect on the atomic metallic ratios (metal/total metal) of the employed trimetallic nanocatalysts, which clearly demonstrates the stability of injected ultradispersed (UD) nanocatalysts (metal/total metal: Mo, 0.6267; Ni, 0.1808; and W, 0.1924) in the porous media at high pressure and temperature. Nonetheless, aggregation of nanocatalysts inside the porous media was observed and graphically demonstrated by environmental scanning electron microscopy (ESEM) images. Overall, the presence of trimetallic nanocatalysts in porous media not just enhanced bitumen upgrading but also improved the produced liquid quality and reduced the coke content as well as CO_2 emission by 50%.