Hydroprocessing in Aqueous Phase

Abstract

A large consumption of H 2 affects the overall economy of conventional hydroprocessing. The costs can be decreased by using water as the source of active hydrogen. This can be achieved under subcritical and supercritical water conditions providing that an active and stable catalyst is developed. Hydroprocessing in aqueous phase has been studied for potential applications in upgrading of high oxygen content feeds and heavy petroleum feeds to liquid hydrocarbons. The feeds were tested at temperatures ranging from less than 200 to 500 °C and total pressure from 1 to 30 MPa. These conditions cover subcritical and supercritical regions of water. Water takes part in hydroprocessing reactions as a free radical scavenger and a hydrogen donor. Hydrogen generated in situ via partial reforming and water−gas shift reactions is more reactive than external hydrogen. Catalyst development for hydroprocessing in aqueous phase has been receiving much attention. High performance was observed over the catalysts containing noble metals (Pt, Pd, Ru, and Rh) supported on various supports; however, the information on a long-term stability of these catalysts is limited.

A Review of Laboratory-Scale Research on Upgrading Heavy Oil in Supercritical Water

“…SCW, defined as the thermodynamic state of water above critical temperature and pressure (374.3 °C and 22.1 MPa), has aroused a great deal of interest in researchers due to its ubiquitous solvent properties and potential ability to donate hydrogen [19]. In contrast to deasphalting, upgrading heavy oil in SCW is a green process, without any auxiliary chemicals required.…”

“…However, with the decreasing demand for fuel oil, these processes will face a dilemma, as small amounts of liquid products but a great deal of coke are formed from these thermal processes [17,18]. Though the hydrogen addition processes can retard the formation of coke and convert heavy components into valuable light fraction, the cost of hydrogen is considerable [19]. Additionally, the deposition of coke and metals can easily deactivate the expensive catalysts for upgrading heavy oil [20].…”

Anthracene aquacracking using NiMo/SiO2 catalysts in supercritical water conditions

“…In addition, the presence of nickel oxidized species could not be fully discarded since some of the XRD peaks of these species could overlap with those of MoO 2 . Overall, the observed structural stability of prepared materials is already an achievement given the problematic in terms of stability displayed by other reference catalysts based on alumina or zeolites in supercritical water [23].…”

“…Later on, the same group introduced Al 2 O 3 in the catalyst formulations aiming to avoid FeO x sintering and thus improving the material stability [22]. The use of noble metal catalysts such as Pt, Pd, Ru, and Rh on a support with adequate surface activity has been reported to exhibit overall good performance [23]. A different study on the desulfurization of heavy oil in SCW considered the use of more economical catalysts like ZnO, MoO 3 and MoS 2 .…”

Kinetic and reaction pathway of upgrading asphaltene in supercritical water

“…But with the decreasing demand for fuel oil, these processes will fall into dilemma as little liquid products but much coke were formed from these thermal processes (Siskin et al, 2006;Xu et al, 2007). Although the hydrogen addition processes can retard the formation of coke and convert heavy components into valuable light fraction, the cost of hydrogen is considerable (Furimsky, 2013;Zhao and Wei, 2008). Additionally, the deposition of coke and metals can easily deactivate the expensive catalysts for upgrading heavy oil (Xu et al, 2009).…”