SUNScholar will be down for routine maintenance from 2018-12-11 10:00 SAST.

Kinetic and Economic Potential Evaluation of Grubbs-type Precatalysts for 1-Octene Metathesis

Visser, Chaney Gene (2017-12)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH SUMMARY: The RSA olefins programme of the DST-NRF Centre of Excellence in Catalysis (c*change) aims to upgrade low-value linear 1-alkenes (also known as alpha-olefins) to high-value Guerbet-type surfactants via a proposed reaction sequence of which the initial step is the organometallic catalytic reaction of metathesis. Metathesis enables atom-efficient, green chemistry synthesis by reducing the number of synthesis steps required with current industry methods. Metathesis research has yielded a library of ruthenium carbene precatalysts, each with its own attributes and shortcomings. Previous work has designed and investigated the performance, kinetics, and industrial viability of precatalysts with the aim of improving thermal stability and efficiency for the metathesis of 1-octene, but has not compared precatalysts from an economic point of view. With the emergence of each new synthesised precatalyst, information such as the kinetic behaviour and performance is required before any economic evaluation can be made. In this study the combined catalytic, kinetic and economic performance of two chelating pyridinyl alcholato (O^N) ruthenium carbene precatalysts of the Grubbs 2nd generation type [RuCl (H2IMes) (O^N)(=CHPh) where O^N = 1-(2’-pyridinyl)-1-(cyclopentyl)-methanolato (GCYC) and O^N = 1-(2ʹ-pyridinyl)-1- (2ʹ-methyl-phenyl),1-phenyl-methanolato (GMPP) was evaluated for 1-octene metathesis. Metathesis reactions were conducted in a batch reactor with neat 1-octene (C8) while investigating the effects of temperature (40 - 100°C) and precatalyst load (C8/Ru: 5 000 - 14 000). Kinetic parameters were obtained by measuring concentration profiles for seven hours and fitting these profiles to fundamental kinetic models. The Douglas method was utilised for designing a conceptual process and estimating the economic potential of each precatalyst Peak performance was observed at 70°C for the GCYC precatalyst with turnover numbers (TONs) of 6631, 80% conversion of 1-octene (C8) and 42% selectivity towards primary metathesis products. In comparison, for the GMPP precatalyst TONs of 5888, 60% C8 conversion and 37% selectivity was obtained at peak temperatures between 70 and 90 °C. Latent thermo-switchable behaviour was observed where activation only occurred beyond the switching temperatures. Various reaction kinetic models were developed and could account for experimentally observed thermal precatalyst deactivation and competing isomerisation reactions with reasonable accuracy. Activation energies for 1-octene consumption were determined as 30.24 kcal.mol-1 and 13.10 kcal.mol-1 for the GCYC and GMPP precatalysts respectively. Similarly, the deactivation energies found for the precatalysts were 22.81 and 5.84 kcal.mol-1 respectively. The GMPP precatalyst was found to follow step-function behaviour and the Arrhenius relationship was followed where complete precatalyst deactivation did not occur. Economic evaluation over a Continuously Stirred Tank metathesis reactor – (CSTR -metathesis reactor) was found to be favourable for both precatalysts with an internal rate of return (IRR) of 73 and 53% respectively making them feasible choices for upgrading linear 1-alkenes to surfactants. The precatalyst with the best overall performance was found to be the GCYC precatalyst but the GMPP precatalyst still offers benefits of less stringent temperature control. Comparison studies with a commercial Hoveyda Grubbs 2nd generation catalyst HG2 proved the commercial catalyst to still be the best at low temperatures with an IRR of 91%. Future studies are recommended to conduct Density Functional Theory (DFT) investigations into the precatalysts, expand the scope of precatalysts for the economic potential evaluation and to consider development studies towards piloting the proposed process.

AFRIKAANS OPSOMMING: Die RSA Olefiene program van die DST-NRF Sentrum vir Uitnemendheid in Katalise (c*change) beoog om lae-waarde lineêre alkene (ook bekend as alpha-olefiene) (LLA) na hoë- waarde Guerbet-surfaktante om te skakel deur ’n voorgestelde reaksienetwerk waarvan die organometaal katalisereaksie van metatese die eerste stap is. Metatese bemagtig “groen-chemie”, atoomdoeltreffende sinstese om opgradering van alkene te bewerkstelling deur die aantal stapppe wat in huidige industriële metodes gebruik word te verminder. Navorsing in metatese het gelei tot die ontwikkeling van ’n reeks ruteniumkarbeen prekatalisators, met elk sy eie kenmerke en tekortkominge. Vorige navorsing het gefokus op die ontwerp en ondersoek van ruteniumkarbeen prekatalisators se prestasievermoë, kinetika, en industriële lewensvatbaarheid om die termiese stabilitiet en effektiwitiet van die prekatalisator vir metatese met 1-okteen te verbeter, maar het nie die prekatalisators vergelyk van ’n ekonomiese oogpunt af nie. Met die opkoms van elke nuwe prekatalisator word inligting rakend die prekatalisator se kinetiese gedrag, en prestasievermoë benodig voordat ’n ekonomiese evaluering voltooi kan word. In hierdie studie is die ekonomiese en kinetiese prestasie van twee chelerende piridiniel alkoholato rutenium karbeen prekatalisators van die Grubbs 2de generasie tipe [RuCl(H2IMes)(O^N)(=CHPh) waar O^N =1-(2’-piridiniel)-1- (siklopentiel)-metanolato (GCYC) en O^N =1-(2’-piridiniell)-1-(2’-metiel-pheniel),1-phenielmetanolato (GMPP) vir 1-okteen metatese geëvalueer. Metatese reaksies was uitgevoer in ’n enkellading reaktor met skoon 1-okteen terwyl die effekte van temperatuur (40-100°C) en prekatalisator lading (C8/Ru: 5 000 - 14 000) ondersoek was. Kinetiese parameters was bepaal deur die konsentrasie profiele te meet vir 7 uur, en gevolglik die resultate te pas met fundamentele kinetiese modelle. Die Douglas metode was gebruik om ’n konseptuele proses te ontwerp en gevolglik die ekonomiese potensiaal van elke prekatalisator te beraam. Optimale gedrag was waargeneem vir die GCYC-katalisator met ’n omsettingsgetal (TON) van 6631, 80% omskakeling van 1-okteen (C8) en 41% selektiwitiet teenoor primêre produkte by 70°C. In vergelyking, het die GMPP-katalisator ’n omsettingsgetal van 5888, 60% omskakeling van C8 en 37% selektiwitiet teenoor primere metatese produkte behaal by ’n temperature tussen 70 en 90°C. Latente termo-skakelbare gedrag was waargeneem waar aktivering eers plaasgevind het bo die aktiveringstemperature. Verskeie kinetiese reaksiemodelle is ontwikkel en kon verduideliking bied (binne redelike voorspelbaarheid) vir die eksperimentele waarneming van termiese katalisatordeaktivering en kompeterende isomerisasie reaksies. Aktiveringsenergië van die GCYC-en GMPP-katalisators vir die verbruik van 1-okteen was 30.24 kcal.mol-1 en 13.10 kcal.mol-1 onderskeidelik. Deaktiverings energië vir die katalisators is as 22.81 en 5.84 kcal.mol-1 onderskeidelik bepaal. Die GMPP-katalisator het trapfunksiegedrag gevolg sowel as die Arrhenius verhouding by temperature waar volledige katalisatordeaktivering nie plaasgevind het nie. Na ’n ekonomiese evaluering met ’n gemengde deurlopende tenk reaktor (CSTR) is dit bevind dat metatese gunstig was vir beide katalisators met ’n interne opbrengskoers (IRR) van 73% en 53% onderskeidelik, dus maak dit hulle moontlik uitvoerbare keuses vir die opgradering van LLA’s na Guerbet-surfaktante. Daar is bevind dat die GCYC-katalisator die algeheel beste presastie lewer, maar die GMPP-katalisator bied steeds heelwat voordele waar minder streng temperatuur beheer benodig is. Vergelykings met ‘n kommersiële 2de generasie Hoveyda-Grubbs katalisator het getoon dat die kommersiële katalisator steeds die beste is by lae temperature met ‘n interne opbrengskoes van 91%. Daar word voorgestel dat toekomstige studies uitgevoer word met die fokus op Digtheid Funksionele Teorie (DFT)-navorsing vir die verskeie katalisators, die uitbreiding van die omvang van katalisators beskou vir die ekonomiese potensiaal evaluering asook om ontwikkelings studies te oorweeg vir die implementering van ’n proef proses.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102892
This item appears in the following collections: