Hydrocracking reaction pathways of 1-methylnaphthalene in a continous fixed-bed reactor
File(s)
Author(s)
Sivena, Anastassia
Type
Thesis
Abstract
Trends in the crude oil supply have shown a decline in reserves of conventional oil, which has been offset by increasing volumes of heavy oil. Therefore, hydrocracking has become an increasingly attractive process for upgrading heavy oil fractions. This process, however, presents major challenges that have to be overcome.
The present work had two principal aims. The first was to develop a new continuous fixed-bed hydrocracking reactor (CFBR) to conduct long time-on-stream experiments, ranging from 180 – 360 minutes. Several challenges were faced during the design and construction caused by operating conditions constraints. Factors such as safety and effective control of the system were also taken into consideration.
The second was to study hydrocracking experiments at different operating conditions performed in the CFBR. These were carried out with a model compound, 1-methylnaphthalene (C11-1MN) and a commercial catalyst, NiMo/Al2O3. Three residence times (1, 10, 20 minutes) and four temperatures (400, 420, 430 and 450 oC) were used, while keeping pressure constant at 10 MPa. Four main groups of products prevailed: partially hydrogenated bicyclic products, hydrogenated bicyclic products, ring-opening products and cracked products. Each group was further divided in alkyl and alkenyl benzenes, alkyl cyclohexane and decalin. The reaction pathway consisted of a mixture of parallel and consecutive reactions. The activation energy for the decomposition of C11-1MN was obtained with the Arrhenius equation. The overall selectivity of partially hydrogenated products and ring-opening products were mirrored and the overall selectivity for cracked products decreased with increasing temperature. The selectivity of hydrogenated products was very low. The effect of the sulphiding agent, diheptyl disulphide (DHDS) present in the feed, was elucidated on the activation of the catalyst. A decrease in sulphur concentration in products was coupled with a noticeable increase in C11-1MN conversion. Finally, the role of DHDS decomposition products in catalyst activation was investigated.
The present work had two principal aims. The first was to develop a new continuous fixed-bed hydrocracking reactor (CFBR) to conduct long time-on-stream experiments, ranging from 180 – 360 minutes. Several challenges were faced during the design and construction caused by operating conditions constraints. Factors such as safety and effective control of the system were also taken into consideration.
The second was to study hydrocracking experiments at different operating conditions performed in the CFBR. These were carried out with a model compound, 1-methylnaphthalene (C11-1MN) and a commercial catalyst, NiMo/Al2O3. Three residence times (1, 10, 20 minutes) and four temperatures (400, 420, 430 and 450 oC) were used, while keeping pressure constant at 10 MPa. Four main groups of products prevailed: partially hydrogenated bicyclic products, hydrogenated bicyclic products, ring-opening products and cracked products. Each group was further divided in alkyl and alkenyl benzenes, alkyl cyclohexane and decalin. The reaction pathway consisted of a mixture of parallel and consecutive reactions. The activation energy for the decomposition of C11-1MN was obtained with the Arrhenius equation. The overall selectivity of partially hydrogenated products and ring-opening products were mirrored and the overall selectivity for cracked products decreased with increasing temperature. The selectivity of hydrogenated products was very low. The effect of the sulphiding agent, diheptyl disulphide (DHDS) present in the feed, was elucidated on the activation of the catalyst. A decrease in sulphur concentration in products was coupled with a noticeable increase in C11-1MN conversion. Finally, the role of DHDS decomposition products in catalyst activation was investigated.
Version
Open Access
Date Issued
2014-07
Date Awarded
2015-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
License URL
Advisor
Millan-Agorio, Marcos
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)