Deactivation of Catalysts and Reaction Kinetics for Upgrading of Renewable Oils
Doctoral thesis, 2019
Renewable oils can be sourced from varied streams like tall oil (paper industry residue), animal fats, used cooking oil etc. due to which their composition and innate contaminants can vary significantly. Phosphorus, alkali metals like potassium or sodium, iron, silicon, chlorides etc. are some of the common poisons present in renewable feedstocks which can cause catalyst deactivation during the upgrading process. In the first section of this thesis, the influence of iron (Fe), phosphorus (from phospholipid) and potassium (K) as poisons during HDO of fatty acids over molybdenum based sulfided catalysts was investigated. A range of concentration of poisons was evaluated to show that these poisons severely impacted the activity of catalysts. A change in selectivity was also seen, which is an important parameter to consider during the industrial production of biofuels. Different characterization techniques were employed to study the poison distribution on catalyst samples from lab experiments as well as from a refinery. It was suggested that Fe deposits preferentially near Ni-rich sites which deteriorated the ability of these catalysts to create active sites i.e. via sulfur vacancies. However, phosphorus resulted in irreversible phase transformation of the support to aluminum phosphate (AlPO4) which resulted in catalyst deactivation via pore blockage. In the comparative experiments, with spherical catalyst particles (1.8 mm), the Fe caused the strongest deactivation among P and K, based on the quantity added to feed oil. Although, considering the decrease in surface area per unit of deposited element after the experiment, then P caused the most deactivation. It was concluded that Fe deposited mostly near to the outer surface irrespective of concentration while P and K penetrated deeper in catalyst particles such that the distribution profile was dependent on the concentration.
Reaction kinetics of HDO of fatty acids provides critical knowledge which could be applied at the refining scale in process design and optimization. The activity and selectivity of NiMo catalyst during HDO of stearic acid was studied by varying reaction conditions like temperature, pressure, feed concentration and batch-reactor stirring rate and using intermediates like octadecanal and octadecanol. A deeper understanding of the reaction scheme and selectivities was developed based on the experimental results. A Langmuir–Hinshelwood-type mechanism was used to develop a kinetic model which well-predicted the changes in selectivities at varying reaction conditions.
Chalmers, Chemistry and Chemical Engineering, Chemical Technology
Investigating the effect of Fe as a poison for catalytic HDO over sulfided NiMo alumina catalysts
Applied Catalysis B: Environmental,; Vol. 227(2018)p. 240-251
Influence of bio-oil phospholipid on the hydrodeoxygenation activity of NiMoS/Al2O3 catalyst
Catalysts,; Vol. 8(2018)
The role of catalyst poisons during hydrodeoxygenation of renewable oils - Prakhar Arora, Hoda Abdolahi, You Wayne Cheah, Muhammad Abdus Salam, Eva Lind Grennfelt, Henrik Rådberg, Derek Creaser, Louise Olsson
NiMoS on alumina-USY zeolites for hydrotreating lignin dimers: Effect of support acidity and cleavage of C-C bonds
Sustainable Energy and Fuels,; Vol. 4(2019)p. 149-163
Effect of Dimethyl Disulfide on Activity of NiMo Based Catalysts Used in Hydrodeoxygenation of Oleic Acid
Industrial & Engineering Chemistry Research,; Vol. 56(2017)p. 5547-5557
Fossil fuels like petrol, diesel, kerosene etc. are made up of different molecules containing carbon and hydrogen while biomass contains – carbon, hydrogen and oxygen. It is critical to remove the oxygen from these feedstocks before they can be used as fuels in the transportation sector. During a biofuel production process, via hydrodeoxygenation (HDO) reactions, these oxygen molecules are selectively removed while carbon and hydrogen remain. This is carried out in refineries using a catalyst to enable these reactions. These catalysts become deactivated which means their performance decreases with time during the production process. In this work, we studied how and what factors cause the deactivation of catalysts. We developed an understanding of deactivation mechanisms resulting from impurities present in renewable feedstocks. This knowledge could be beneficial for industry to prevent or delay catalyst deactivation and lead to biofuel production becoming even more efficient.
Alternative fuel production using bio-oils from the forest sector -Fundamental studies of catalyst deactivation
Formas (2014-164), 2014-01-01 -- 2018-12-31.
Areas of Advance
Chemical Process Engineering
Other Chemical Engineering
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4681