Separation of homogeneous hydroformylation catalysts using organic solvent nanofiltration

Peddie, Waylin Lee (2016-03)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: The upgrade of inter alia syngas and short chain olefins to high value commodities in the surfactant and detergent range, finds relevance worldwide due to the abundance of feedstock. These commodities are manufactured systematically through an innovative network of homogeneously-catalysed reactions, i.e. metathesis, hydroformylation and hydrogenation, and forms part of the overarching theme of the RSA Olefins programme of the South African Department of Science and Technology (DST) and National Research Foundation (NRF) Centre of Excellence in Catalysis (c*change). Homogeneous catalysts are generally preferred over its heterogeneous counterpart due to inter alia superior catalytic performance, higher product selectivity and negligible diffusional problems. However, the prevalence of homogeneous catalysts is hampered by the expensive, waste generating and destructive thermal separation methods required for the recovery of these catalysts. The main aim of this study is therefore to demonstrate the non-destructive recovery of homogeneous catalysts, in a state allowing for their recycle and reuse, from hydroformylation post-reaction mixtures as well as the potential for further solvent purification using organic solvent nanofiltration (OSN). Furthermore, confirmation is afforded to the cost- and energy-efficiency of OSN for homogeneous catalyst recovery commonly alluded to in literature by performing an economic and energy evaluation between OSN and classical downstream recovery units, i.e. distillation. Focus was placed on the recovery of two well-known and commercially available hydroformylation catalysts, HRh(CO)(PPh3)3 and Co(C5H7O2)3, and the solvents considered include those representative of the hydroformylation and hydrogenation reactions (1-octene, 1-decene, 1-nonanal, 1-undecanal, 1-nonanol, 1-undecanol), using the Duramem 150 (DM-150), Duramem 200 (DM-200) and STARMEM 240 (ST-240) membranes. Parameters such as applied pressure, feed concentration, solvent type and catalyst load were varied and its effects on the ST-240 membrane’s performance investigated. The main contributions and conclusions from this study were threefold regarding, 1) the capability of OSN to recover and reuse homogeneous catalysts, 2), the characterisation of OSN performance in terms of permeance and separation, and 3) the modelling of OSN performance. 1) OSN catalyst recovery: It was found that the presence of the rhodium-based catalyst, HRh(CO)(PPh3)3, resulted in the hydroformylation reaction having a high regioselectivity toward the linear aldehyde product and produced mainly 1-nonanal with a yield of approximately 66 mol% in the case of 1-octene as substrate. Additionally, linear to branched (n/iso) product molar ratios of greater than 2 were observed. It was also found that cost and energy savings of greater than 90% can be attained upon using OSN systems for homogeneous catalyst recovery as compared to conventional distillation systems. 2) OSN permeation and separation: It was found that the ST-240 membrane was able to successfully separate homogeneous catalysts from different reaction systems with catalyst recoveries up to 99%. Moreover, the recovered catalyst was found to be in a condition suitable for reuse for at least three consecutive hydroformylation reaction cycles, thereby improving upon its overall catalytic performance in excess of 30%. Flux of pure reaction species (1-octene, 1-decene, 1-nonanal, 1-undecanal, 1-nonanol and 1-undecanol) were shown to range between 1.83 L.m-2.h-1 to 135 L.m-2.h-1. Flux was also found to be highly dependent on applied pressure, solvent viscosity and interaction parameters indicative of the solvent-membrane and solute-solvent interactions. Minimal separation was attainable between binary mixtures consisting of 1-octene/1-nonanal, 1-decene/1-undecanal and 1-nonanal/1-nonanol. 3) OSN modelling: The OSN separation process for the different solvents were described using literature-based transport models based on the pore-flow and solution-diffusion models with the latter performing relatively better than the former in terms of predictive capacity. Moreover, a newly postulated model which incorporated an additional solubility parameter term was found to improve predictive capacity of the solution-diffusion model by approximately 3%. KEYWORDS: Organic Solvent Nanofiltration, Hydroformylation, Homogeneous catalyst, Catalyst separation

AFRKAANSE OPSOMING: Die opgradering van onder andere sintese gas en kort-ketting olefiene na hoë waarde produkte in die surfaktant en skoonmaakmiddel reeks, vind relevansie wêreldwyd as gevolg van ʼn oorvloed van roumateriaal. Hierdie produkte kan sistematies vervaardig word deur ʼn innoverende netwerk van homogeen-gekataliseerde reaksies, naamlik metatese, hidroformilering en hidrogenering, en vorm deel van die oorkoepelende doel van die “RSA Olefins programme" van die Suid-Afrikaanse Departement van Wetenskap en Tegnologie (DST) en Nasionale Stigting vir Navorsing (NRF) “Centre of Excellence in Catalysis (c*change)”. Homogene katalisatore word in die algemeen verkies bo sy heterogene eweknie as gevolg van onder andere beter katalitiese vermoë, hoër selektiwiteit vir produkte en weglaatbare diffusieprobleme. Die oorheersing van homogene katalisatore is egter belemmer deur duur, afval-genererende en vernietigende termiese skeidingsmetodes benodig vir die herwinning van hierdie katalisators. Die hoofdoel van hierdie studie is om die nie-vernietigende herwinning van homogene katalisatore te demonstreer, sodat dit in ʼn toestand geskik vir hergebruik is, vanaf ʼn hidroformileringsreaksie produkmengsel sowel as die potensiaal vir verdere suiwering van die reaktiewe spesies deur organiese oplosmiddel nanofiltrasie (OSN). Verder, aandag is gegee aan die koste- en energie-effektiwiteit van OSN vir die herwinning van homogene katalisatore wat in die algemeen in literatuur na gewys word deur ʼn ekonomiese en energie evaluering tussen OSN en klassieke stroomaf skeidings prosesse, naamlik distillasie, uit te voer. Daar is gefokus op die herwinning, met behulp van die STARMEM 240 (ST-240) membraan, van twee welbekende en kommersieel beskikbare hidroformileringkatalisatore, HRh(CO)(PPh3)3 en Co(C5H7O2)3, en verbindings verteenwoordigende hidroformilerings- en hidrogeneringsreaksies (1-okteen, 1-deseen, 1-nonanaal, 1-undekanaal, 1-nonanol, 1-undekanol). Parameters soos die toegepaste druk, voerkonsentrasie, oplosmiddel en katalisatorlading is gevarieer en die effek op OSN se skeidings vermoë ondersoek. Die hoofbydraes en gevolgtrekkings van hierdie studie is drievoudig met betrekking tot, 1) die gebruik van OSN vir katalisatorherwinning, 2) die karaktarisering van OSN se skeidings vermoë en 3) die modellering van die OSN. 1) OSN katalisatorherwinning: Daar was gevind dat die teenwoordigheid van die rodium-gebaseerde katalisator, HRh(CO)(PPh3)3, ʼn hoë regioselektiwiteit van die hidroformileringsreaksie tot die lineêre aldehiedproduk het en gevolglik meestal 1-nonanaal vervaardig met ʼn opbrengs van ongeveer 66 mol% met 1-okteen as substraat. Verder was die molêre verhouding van lineêre tot vertakte (n/iso) aldehiedprodukte van groter as 2 gemeet. Daar was gevind dat kostes- en energie-besparings van meer as 90% bereik kan word met die gebruik van OSN prosesse vir die herwinning van homogene katalisatore in vergelyking met konvensionele distillasiestelsels. 2) OSN permeasietempo en skeiding: Daar was gevind dat die ST-240 membraan geskik was vir die suksesvolle herwinning van homogene katalisatore van die verskillende reaksie sisteme met katalisatorherwinning tot 99%. Verder was die katalisator geskei in ʼn vorm geskik vir hergebruik vir ten minste drie agtereenvolgende hidroformileringsreaksiesiklusse en met dit verbeter die algehele katalitiesevermoë met meer as 30%. Permeasietempo’s van suiwer reaksiespesies (1-okteen, 1-deseen, 1-nonanaal, 1-undekanaal, 1-nonanol, 1-undekanol) wissel tussen 1.83 L.m-2.h-1 en 135 L.m-2.h-1. Permeasietempo was ook waargeneem om hoogs afhanklik te wees op toegepaste druk, spesiesviskositeit en interaksieparameters verteenwoordigend van die oplosmiddel-membraan en opgeloste stof-oplosmiddel interaksies. Minimale skeiding was bereikbaar tussen binêre mengsels van 1-okteen/1-nonanaal, 1-deseen/1-undekanaal en 1-nonanaal/1-nonanol. 3) OSN modellering: Die OSN skeidingsproses vir die verskillende spesies was beskryf deur literatuur-gebaseerde modelle geskoei op die porie-vloei en oplossing-diffusie modelle. Verder was ʼn nuut-veronderstelde model insluitend met ʼn addisionele oplosbaarheidparameter gevind om voorspellende akkuraatheid met ongeveer 3% te verbeter. SLEUTELWOORDE: Organiese oplosmiddel nanofiltrasie, Hidroformilering, Homogene katalisator, katalisatorherwinning,

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