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dc.contributor.advisorTakanabe, Kazuhiro
dc.contributor.authorShaikh Ali, Anaam
dc.date.accessioned2016-12-05T05:18:59Z
dc.date.available2017-12-05T00:00:00Z
dc.date.issued2016-11-30
dc.identifier.citationShaikh Ali, A. (2016). Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane. KAUST Research Repository. https://doi.org/10.25781/KAUST-71W2X
dc.identifier.doi10.25781/KAUST-71W2X
dc.identifier.urihttp://hdl.handle.net/10754/621931
dc.description.abstractLiquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation of strongly chemisorbed intermediate originating from TOL. DFT calculation indicated that Zn metal prefers to occupy the step sites of Ni where unselective C–C bond breaking was considered to preferentially occur, explaining suppression of hydrogenolysis activity. Additionally, it confirmed that the H-deficient species at methyl position group (C6H5CH2) was stable on the surface, making its hydrogenation being rate determining step, consistent with positive order in H2 pressure on TOL formation rate. This may explain the conclusive role by H2 in facilitating desorption of the H-deficient surface species that was produced through further dehydrogenation of TOL.
dc.language.isoen
dc.subjectNon-noble metal
dc.subjectNi-based
dc.subjectDehydrogenation
dc.subjectMethylcyclohexane
dc.subjectToluene
dc.titleDevelopment of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane
dc.typeDissertation
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.rights.embargodate2017-12-05
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberCavallo, Luigi
dc.contributor.committeememberDa Costa, Pedro M. F. J.
dc.contributor.committeememberSeshan, Kulathuiyer
thesis.degree.disciplineChemical Science
thesis.degree.nameDoctor of Philosophy
dc.rights.accessrightsAt the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2017-12-05.
refterms.dateFOA2017-12-05T00:00:00Z


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