Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

Garba, Mustapha D.; Jackson, S. David

doi:10.1007/s13203-016-0173-y

Cited by 17 publications

(11 citation statements)

References 36 publications

(46 reference statements)

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“…The absence of cyclohexanone formed from anisole is surprising as it implies that the 4-methoxyphenol is influencing the reactivity of the anisole even though it is not reacting. This type of behaviour has been seen in transhydrogenation [38] but is not commonly reported. It is clear that the demethoxylation reaction of anisole was occurring giving cyclohexane but that the demethylation reaction was inhibited.…”

Section: Competitive Reactionsmentioning

confidence: 57%

Low temperature hydrogenation and hydrodeoxygenation of oxygen-substituted aromatics over Rh/silica: part 1: phenol, anisole and 4-methoxyphenol

Alshehri

Feral

Kirkwood

et al. 2019

Reac Kinet Mech Cat

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The hydrogenation and competitive hydrogenation of anisole, phenol and 4-methoxyphenol was studied in the liquid phase over a Rh/silica catalyst at 323 K and 3 barg hydrogen pressure. The rate of conversion of the reactants to products gave an order of anisole ≫ phenol > 4-methoxyphenol with hydrogenation and hydrodeoxygenation products being produced. Anisole, the most reactive substrate, was rapidly converted to methoxycyclohexane, cyclohexane, cyclohexanone and cyclohexanol, while phenol was hydrogenated to cyclohexanone, cyclohexanol and cyclohexane. In both cases cyclohexanol was produced as a secondary product from cyclohexanone hydrogenation. The yield of cyclohexane, the hydrodeoxygenation (HDO) product was > 20% from both reactants and was formed as a primary product from the aromatic species. Hydrogenation of 4-methoxyphenol was selective to 4-methoxycyclohexanone with no alcohol formation, while the hydrogenolysis products revealed that the catalyst was more active for demethoxylation than dehydroxylation. A comparative strength of adsorption was determined from competitive hydrogenation and gave an order of anisole > phenol > 4-methoxyphenol. Competitive, pair hydrogenation inhibited HDO and stopped cyclohexane from being produced from phenol and 4-methoxyphenol, although it was still produced from anisole. An increased rate of hydrogenation for 4-methoxyphenol was observed for competitive reactions with phenol and anisole but not when all three reactants were present. In contrast to the pair reactions, when all three reactants were present HDO occurred with all aromatics producing cyclohexane. Replacing hydrogen with deuterium revealed an inverse kinetic isotope effect for ring hydrogenation of 4-methoxyphenol but not phenol or anisole, which both had a positive KIE.

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Section: Competitive Reactionsmentioning

confidence: 57%

Low temperature hydrogenation and hydrodeoxygenation of oxygen-substituted aromatics over Rh/silica: part 1: phenol, anisole and 4-methoxyphenol

Alshehri

Feral

Kirkwood

et al. 2019

Reac Kinet Mech Cat

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“…Hence, transhydrogenation combines the two processes (alkane dehydrogenation and alkyne hydrogenation) over a catalyst to form two alkenes. Alkane dehydrogenation is endothermic (typically around + 125 kJ mol −1 ) while alkyne/alkadiene hydrogenation is exothermic (typically around − 165 kJ mol −1 ); therefore, by coupling the endothermic dehydrogenation process with the exothermic hydrogenation process it is possible to generate a process, where the reaction conditions may be adjusted in order to produce a reaction that is net endothermic, net exothermic or thermally stable, which can simplify and reduce the cost involved in the process [11,15]. For example, the transhydrogenation process between pentane and 1-hexyne is thermodynamically favoured at most temperatures.…”

Section: Introductionmentioning

confidence: 99%

Transhydrogenation of pentane and 1-hexyne over CrOx/Al2O3 and potassium-doped CrOx/Al2O3 catalysts

Garba

Jackson

2019

Appl Petrochem Res

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The transhydrogenation of pentane (P) and 1-hexyne (1HY) was investigated over 4% CrO x /Al 2 O 3 and potassium-doped 4% CrO x /Al 2 O 3 catalysts over a range of temperatures (523-773 K) with a 5:1 P:1HY ratio. Over the CrO x /Al 2 O 3 catalyst, transhydrogenation clearly occurred at temperatures below 625 K where the yield of alkenes was higher for the co-fed system than for a combination of the individual yields. Due to the acidic nature of the alumina, many of the products were alkylated olefins and alkylated hydrocarbons formed by coincident alkylation and isomerisation. When pentane was added to a feed containing 1-hexyne, the extent of carbon deposition was reduced. By comparing transhydrogenation to limited hydrogen 1-hexyne hydrogenation at 623 K, it was shown that the processes of hydrogenation and transhydrogenation were different, with hydrogenation favouring alkanes, while transhydrogenation favoured alkenes. This may be because pentane dehydrogenation only releases two hydrogen atoms, which only allows 1-hexyne to hydrogenate to 1-hexene. Therefore, if the rate of alkene isomerisation and desorption is faster than that of pentane dehydrogenation, only alkenes will be observed. The latter proposal would suggest that the dehydrogenation/hydrogenation process is closely coupled and would be consistent with pentane influencing 1-hexyne surface chemistry. The effect of the potassium doping was to increase the yield of alkenes. The reason for this may be related to changes in the nature of the surface chromia species. The potassium also neutralised the acid sites on the alumina, reducing the extent of alkylation and hydrogenolysis, which suppressed the formation of other alkynes in the product mix.

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“…42 However, alkynes are thermodynamically less stable than the respective alkene due to the nature of their bonding and strongly adsorb catalyst surfaces. Highly unsaturated hydrocarbons are sometimes hydrogenated into corresponding olefin depending on demands.…”

Section: Hydrogenation Of Unsaturated C4-c8 To Alkanesmentioning

confidence: 99%

Catalytic Hydrogenation of Hydrocarbons for Gasoline Production

Garba¹,

Galadima²

2018

JPS

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Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

Cited by 17 publications

References 36 publications

Low temperature hydrogenation and hydrodeoxygenation of oxygen-substituted aromatics over Rh/silica: part 1: phenol, anisole and 4-methoxyphenol

Low temperature hydrogenation and hydrodeoxygenation of oxygen-substituted aromatics over Rh/silica: part 1: phenol, anisole and 4-methoxyphenol

Transhydrogenation of pentane and 1-hexyne over CrOx/Al2O3 and potassium-doped CrOx/Al2O3 catalysts

Catalytic Hydrogenation of Hydrocarbons for Gasoline Production

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