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The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation
Bibliography : pages 244-253.
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| Format: | Thesis |
| Language: | English |
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Department of Chemical Engineering
2016
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| _version_ | 1867613286391873536 |
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| access_status_str | Open Access |
| author | Möller, Klaus Peter |
| author2 | Kojima, Masami |
| author_browse | Kojima, Masami Möller, Klaus Peter |
| author_facet | Kojima, Masami Möller, Klaus Peter |
| author_sort | Möller, Klaus Peter |
| collection | Thesis |
| description | Bibliography : pages 244-253. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/21919 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:43.673Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Chemical Engineering |
| publisherStr | Department of Chemical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/21919 The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation Möller, Klaus Peter Kojima, Masami O'Connor, Cyril T Catalyst poisoning Chemical Engineering Bibliography : pages 244-253. The objective of this study was to determine the effect that the type of catalyst and reaction would have on the rate of deactivation, properties of coke and transport properties of the catalyst. HY and HM were chosen because of their different pore structures and acid site distributions. Hexane cracking at 1 atmosphere and high pressure propene oligomerisation provided two different reaction types. The transport properties of the catalysts were compared by measuring adsorption and diffusion using the GC technique with ancillary information obtained from ammonia TPD, mercury porosimetry and BET surface area measurements. It was confirmed that a knowledge of the crystallite size distribution was necessary to predict the adsorption and diffusion of light hydrocarbons in HY and HM. The adsorption constants and heats of sorption were found to,be much greater in HM than in HY, in agreement with the presence of a greater number of strong acid sites detected in HM by ammonia TPD. The diffusivities of the Tight hydrocarbons were too large to measure in HY. In HM only methane diffusion was too fast to measure. Diffusivities decreased and adsorption constant increased with increasing molecular size. HY had greater activity and slower deactivation than HM towards hexane cracking. The reaction as well as coking took place in the micro-pores. The graphitic coke content of HY was much greater than in HM. The introduction of the macro-pore adsorption term was necessary to predict diffusion in coked samples, emphasizing the severity of the diffusional resistance. While hydrocarbon diffusivities decreased after cracking, adsorption constants were found to increase in the presence of graphitic coke in J-IY. In HM the deactivation took place primarily by pore blockage, with strong acid sites being preferentially removed. Both diffusivities and adsorption constants decreased in the presence of coke in HM. In HY and HM deactivated by oligomerisation, macro-pore adsorption had to be taken into account, again emphasizing the severe diffusional resistance. Reaction as well as graphitic coke occurred predominantly in the micro-pores in HY. High boiling point hydrocarbons were able to migrate into the mesopores where they closed the mouths of the micro-pores in HY. Strongly adsorbed high boiling point hydrocarbons which deactivated the catalyst presented far less diffusional resistance in HY than the equivalent mass of graphitic coke. These high boiling point hydrocarbons also markedly lowered the adsorption constants. Graphitic coke was responsible for the modification of the catalyst selectivity. Temperature runaway in HY caused severe coking and hence deactivation. The inactivity of HM below 200°C was caused by strong adsorption and high diffusional resistance of reactant and product. Pore blockage was the dominant deactivation mechanism in HM, while in HY it was partial pore blockage by graphitic coke and pore mouth closure by high boiling point hydrocarbons. It was possible to restore the activity of HY for oligomerisation by flushing the high boiling point hydrocarbons in flowing nitrogen. 2016-09-25T16:49:14Z 2016-09-25T16:49:14Z 1989 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/21919 eng application/pdf Department of Chemical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Catalyst poisoning Chemical Engineering Möller, Klaus Peter The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| thesis_degree_str | Doctoral |
| title | The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| title_full | The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| title_fullStr | The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| title_full_unstemmed | The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| title_short | The deactivation of Zeolite-Y and mordenite during hexane cracking and propene oligomerisation |
| title_sort | deactivation of zeolite y and mordenite during hexane cracking and propene oligomerisation |
| topic | Catalyst poisoning Chemical Engineering |
| url | http://hdl.handle.net/11427/21919 |
| work_keys_str_mv | AT mollerklauspeter thedeactivationofzeoliteyandmordeniteduringhexanecrackingandpropeneoligomerisation AT mollerklauspeter deactivationofzeoliteyandmordeniteduringhexanecrackingandpropeneoligomerisation |