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Heavy Oil Reservoirs and Crude Oil Characterization
Published in Cesar Ovalles, Subsurface Upgrading of Heavy Crude Oils and Bitumen, 2019
Once we have described our current knowledge and understanding of the composition of petroleum and its fractions, we turned our attention to the asphaltenes. It is well known that this fraction is mainly responsible for the high viscosity of HO/B at room and reservoir temperatures [Henaut et al. 2001, Ovalles et al. 2011]. Also, they are considered to be the “bad actors” when heavy crude oils and bitumens are produced, transported, and upgraded. Asphaltene precipitation is a serious issue throughout the petroleum value chain (Figure 1.8). Besides the choking of the pipelines during transportation, asphaltenes can plug up well bores and decrease or stop oil production entirely. In downstream, asphaltenes are believed to be the source of sediment and coke during thermal upgrading processes, which in turn reduce and limit the yield of residue conversion. In catalytic upgrading processes, they contribute to catalyst poisoning by coke and metal deposition. Asphaltenes can also cause fouling in heat exchangers and other refinery units [Speight 2007, Ramirez-Corredores 2017].
Membrane Technology for Green Engineering
Published in Neha Kanwar Rawat, Tatiana G. Volova, A. K. Haghi, Applied Biopolymer Technology and Bioplastics, 2021
Supriya Dhume, Yogesh Chendake
The membrane reactors are working very effectively for continuous removal of water generated during process. Applications of membrane reactors for water removal during catalytic reactions in food, pharmaceutical, cosmetics, and petrochemical industries are well investigated and established. Currently, global target in this direction is design of a compact and more efficient catalytic membrane reactor. By applying water removal, two objectives have been pursued:(i) overcoming the thermodynamic limitations of the reaction; and (ii) avoiding catalyst poisoning.
Fundamental Principles
Published in Martyn V. Twigg, Catalyst Handbook, 2018
The most direct way of dealing with catalyst poisoning is the purification of reactor feeds and the catalysts themselves. Special process stages are used specifically to achieve this, e.g. hydrodesulphurization to protect nickel catalysts in steam reforming. Other process stages may also do this; for example, the methanation stage, which is designed to convert CO and CO2 to methane to prevent poisoning of ammonia catalyst, will also remove any traces of H2S reaching this stage.
Effect of temperature on deactivation models of alumina supported iron catalyst during Fischer-Tropsch synthesis
Published in Petroleum Science and Technology, 2019
Maliheh Ghofran Pakdel, Hossein Atashi, Hossein Zohdi-Fasaei, Ali Akbar Mirzaei
Increase in greenhouse gas emission is originated from fossil fuels. Production of clean fuels from hydrogen and carbon monoxide by Fischer-Tropsch synthesis (FTS) has now become a commercial procedure (Davis 2007; Riyahin, Atashi, & Mohebbi-Kalhori 2016; Riyahin, Atashi, & Mohebbi-Kalhori 2017; Rohani et al. 2010). This process is mainly carried out at the presence of iron and cobalt catalysts, which results in formation of valuable hydrocarbons (MohammadRezapour, Mirzaei, & Zohdi-Fasaei 2018; Zohdi-Fasaei et al. 2017). Iron catalysts are used for synthesis gas obtained from coal and biomass (low ratio of H2/CO)(Atashi & Rezaeian 2017), as they show proper activity for the reaction of water-gas shift. Low product selectivity, agglomeration and sintering of catalysts have limited the application of iron catalysts at high operating temperatures (Nakhaei Pour et al. 2010). There are different reasons for catalyst poisoning, among which catalyst particle sintering and carbon species deposition can be mentioned (Ermakova et al. 2001). Several agents can deactivate iron catalyst including active to inactive phase transition and carbon poisoning (Jackson et al. 1997). Iron catalysts could be quickly deactivated by adsorption of coke on catalyst surface and oxidation reactions (Maretto & Krishna 1999). One of the major challenges in iron catalysts design is to overcome their deactivation rate (de Smit & Weckhuysen 2008). Minimization of deactivating rate and enhancement of catalyst lifetime through understanding their deactivation mechanisms have been one of the important topics in recent decades. Extensive studies have been reported on deactivation of Fischer–Tropsch process catalysts since 1960 (Bambal et al. 2014; Duvenhage & Coville 2006; Ehrensperger & Wintterlin 2015; Li & Coville 2001; Ma et al. 2018; Ma et al. 2015; Ma et al. 2016; Ordomsky et al. 2016; Pendyala et al. 2016; Saib et al. 2010). Iron catalysts can lose their activity over time because of the following reasons: (1) conversion of the active phase to the neutral phase (2) Loss of active surface area due to the adsorption of carbonates (fouling) (3) Loss of activated surface area due to crystalline growth (sintering) and 4- Sulfur chemical poisoning (de Smit & Weckhuysen 2008). Among these deactivation mechanisms, FTS catalysts poisoning by impurities is one of the major causes of deactivation, increasing the operating costs. It is therefore important to determine the catalyst's sensitivity to impurities to increase its lifetime (Ma et al. 2018). Various studies have addressed the effects of calcium, magnesium and lanthanum promoters on the activity and selectivity of iron products during FTS operation (Nakhaei Pour et al. 2010; Nakhaei Pour et al. 2008). Many studies of Bukker describe the progress of activity, selectivity and stability of iron catalysts (Bukur, Lang, & Ding 1999; Bukur et al. 1990). Deactivation models are of crucial importance in design and control of chemical processes. In this regard, the present study investigates deactivation models of an alumina supported iron catalyst at different temperatures.