Hydrogenation and Ring Opening of Aromatic and Naphthenic Hydrocarbons Over Noble Metal (Ir, Pt, Rh)/Al2O3 Catalysts

Abstract

The hydrogenation and ring opening of model hydrocarbons and of naphtha was studied over commercial noble metal (Ir, Pt, Rh)/Al 2 O 3 catalysts. The experiments were performed in a fixed bed reactor at temperatures between 220 and 350°C and pressures of 1.1 and 5.0 MPa, respectively. The product distribution was determined and the cetane number was calculated. The Pt catalyst is very active for hydrogenation of aromatics but does not catalyse the ring opening of naphthenes. The Ir and Rh catalysts are active for both hydrogenation of aromatics and ring opening of naphthenes. Experiments with toluene, mxylene, propyl-benzene, and methylcyclohexane indicate that ring opening follows a selective mechanism, where the cleavage of bisecondary carbon bonds is favoured. This results in predominant formation of branched paraffins. The product distribution as well as cracking of long-chain hydrocarbons, which increase at temperatures above 260°C, lead to an insignificant boost in the cetane number, as confirmed by experiments using real naphtha as feedstock.

Application of a Pyroprobe–Deuterium NMR System: Deuterium Tracing and Mechanistic Study of Upgrading Process for Lignin Model Compounds

“…In addition, several direct ring opening pathways for methylcyclohexane without any cyclopentane intermediates have also been proposed in the literature. 23,24 As expected, similar pathways for hydrogenation and ring opening of toluene have been proposed in the literature. 24,25 Methylcyclohexane has been reported as the most abundant intermediate, which is the direct hydrogenation product from toluene.…”

“…23,24 As expected, similar pathways for hydrogenation and ring opening of toluene have been proposed in the literature. 24,25 Methylcyclohexane has been reported as the most abundant intermediate, which is the direct hydrogenation product from toluene. The product from methyl group eliminationbenzenehas also been observed.…”

“…There are several literature reports − about the ring opening of methylcyclohexane, which indicate that ethylcyclopentane, 1,2-dimethylcyclopentane, 1,3-dimethylpentane, and 1,1-dimethylpentane are major intermediates before the ring opening process. In addition, several direct ring opening pathways for methylcyclohexane without any cyclopentane intermediates have also been proposed in the literature. , As expected, similar pathways for hydrogenation and ring opening of toluene have been proposed in the literature. , Methylcyclohexane has been reported as the most abundant intermediate, which is the direct hydrogenation product from toluene. The product from methyl group eliminationbenzenehas also been observed.…”

Size and Stoichiometry Effects on the Reactivity of MoCy Nanoparticles toward Ethylene

“…The use of catalysts is key for producing clean fuels and several commodities, particularly by means of hydrogenation reactions of CC double bonds in olefins, where Pt, Pd, Ru, Rd, Os, and Ir sometimes termed Pt-group elements are so far the most used catalyst due to their good performance . In practice, these metals are supported on oxides, zeolites, and activated carbon, and exhibit a high catalytic activity. − However, the scarcity of these metals in the Earth’s crust, together with their sensitivity to sulfur poisoning in the petrochemical industry, has motivated the search for alternative catalysts …”

Mechanistic Similarities and Differences for Hydrogenation of Aromatic Heterocycles and Aliphatic Carbonyls on Sulfided Ru Nanoparticles

“…Last, the benzene-H 2 reaction formed cyclohexane as the only hydrogenation product, at a selectivity of 74.6%, and C1–C6 hydrocarbons (except cyclohexane) from ring contraction and/or hydrocracking, at a selectivity of 25.4%. Although few studies have reported the reaction pathway of benzene hydrocracking on metallic Ru catalysts, we surmise that the hydrocracking occurs readily after the benzene hydrogenation on Ru 0 /SiO 2 , since previous studies for benzene, toluene, propylbenzene, and m -xylene hydroconversion over transition metal catalysts (Ir/Al 2 O 3 and Rh/Al 2 O 3 ) under comparable conditions (493–553 K, 1.1 MPa) have reported that the hydrogenation events, which generate cyclic alkanes, occur before the hydrogenolysis events …”