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- Arora, Prakhar, 1987
(författare)
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Catalytic Upgrading of Waste Oils to Advanced Biofuels – Deactivation and Kinetic Modelling Study
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for liquid hydrocarbons as transportation fuels is enormous and ever growing. Advanced biofuels is one of the promising solutions to keep pace with the global transition to cleaner energy by reducing greenhouse gas emissions from the transport sector. It is possible to selectively remove oxygen from waste oils like tall oil, used cooking oil etc. via a catalytic hydrodeoxygenation (HDO) process to produce advanced biofuels. These biofuels have similar molecules as in the traditional fossil-based fuels and exhibit improved performance. This thesis focuses on aspects of catalyst deactivation and kinetic modelling of HDO reactions. In the first study, the influence of iron (Fe) as a poison during HDO of a model compound for renewable feeds (Oleic acid) over molybdenum based sulfided catalysts was investigated. Fe is a potential contaminant in renewable feeds due to corrosion during transportation and storage in iron vessels. A series of experiments with varying Fe-oleate concentration in the feed over MoS2/Al2O3 and NiMoS/Al2O3 catalysts. There was a salient drop in the activity of the catalysts. At higher Fe concentration, for the NiMoS catalyst, the selectivity for the direct hydrodeoxygenation product (C18 hydrocarbons) increased. However, it was opposite for the MoS2 catalyst. There was a decrease in the yield of direct hydrodeoxygenation products and an increase in yield of decarbonated products. It was proposed that Fe interacted with these two catalyst systems differently. Fe influenced the critical step of creation of sulfur vacancies in a negative way which resulted in lower activity. Microscopic analysis indicated that Fe was preferentially deposited close or around the nickel promoted phase, which explained why the role of Ni as a promoter for the decarbonation route was subdued for the NiMoS catalyst. In the second study, the kinetics during HDO of stearic acid (SA) over a sulfided NiMo/Al2O3 catalyst were explored to investigate the reaction scheme. Model compounds like octadecanal (C18=O) and octadecanol (C18-OH) were employed to understand the reaction steps and quantify the selectivity. A Langmuir–Hinshelwood-type kinetic model was used to investigate the kinetics. The results from the proposed kinetic model were found to be in good agreement with experimental results. In addition, the model could effectively reproduce the observed experimental profiles of different intermediates like C18=O and C18-OH and illustrate phenomena like inhibiting effects of the fatty acid.
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| 2. |
- Arora, Prakhar, 1987, et al.
(författare)
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Investigating the effect of Fe as a poison for catalytic HDO over sulfided NiMo alumina catalysts
- 2018
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 227, s. 240-251
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Tidskriftsartikel (refereegranskat)abstract
- The effect of iron (Fe) as poison present in renewable feeds was studied during hydrodeoxygenation (HDO) overmolybdenum based sulfided catalysts. The study was carried out at 6 MPa and 325 °C in batch reaction conditions. Different concentrations of Fe in the feed were tested over MoS2/Al2O3 and NiMoS/Al2O3. A notable drop in activity for the conversion of oxygenates was observed for both catalyst systems with an increased concentration of Fe in the feed. However, the changes in selectivity of products was opposite for unpromoted and Nipromoted catalysts. In the case of the NiMoS catalyst, at higher Fe concentration, the decarbonated product (C17 hydrocarbons) decreased while the direct hydrodeoxygenation product (C18 hydrocarbons)increased. On the contrary, for the base catalyst (MoS2), there was a decrease in the yield of direct hydrodeoxygenation (C18 hydrocarbons) products and an increase in yield of decarbonated products (C17 hydrocarbons). These sulfided catalysts have different sites for these two different reaction routes and they interacted differently with Fe during the deactivation process. With surface deposition of Fe, the ability of these catalysts to create active sites i.e. via sulfur vacancies deteriorated. TEM-EDX results suggested that the effect of Ni as a promoter for the decarbonation route was nullified and a resultant FeMo phase explains the drop in activity and change in selectivity.
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| 3. |
- Salam, Muhammad Abdus, 1983, et al.
(författare)
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Influence of bio-oil phospholipid on the hydrodeoxygenation activity of NiMoS/Al2O3 catalyst
- 2018
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodeoxygenation (HDO) activity of a typical hydrotreating catalyst, sulfided NiMo/γ-Al2O3for deoxygenation of a fatty acid has been explored in a batch reactor at 54 bar and 320°C in the presence of contaminants, like phospholipids, which are known to be present in renewable feeds. Oleic acid was used for the investigation. Freshly sulfided catalyst showed a high degree of deoxygenation activity; products were predominantly composed of alkanes (C17 and C18). Experiments with a major phospholipid showed that activity for C17 was greatly reduced while activity to C18 was not altered significantly in the studied conditions. Characterization of the spent catalyst revealed the formation of aluminum phosphate (AlPO4), which affects the active phase dispersion, blocks the active sites, and causes pore blockage. In addition, choline, formed from the decomposition of phospholipid, partially contributes to the observed deactivation. Furthermore, a direct correlation was observed in the accumulation of coke on the catalyst and the amount of phospholipid introduced in the feed. We therefore propose that the reason for the increased deactivation is due to the dual effects of an irreversible change in phase to aluminum phosphate and the formation of choline.
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