Selective Ring-Shift Isomerization in Hydroconversion of Fluorene over Supported Platinum Catalysts

Abstract

Hydroconversion of fluorene has been conducted over the zeolites and silica−alumina-supported platinum catalysts. The hydrogenation of aromatic rings, the hydroisomerization of the cycloalkanes, and the cracking reaction over the Pt/ Y zeolite catalysts are studied to give a detailed hydroconversion reaction network of fluorene through conversion of the synthesized intermediates. Compared to the β-zeolites and silica−alumina supports used, the dispersed platinum catalysts on the Y-zeolites with unique cage structure and acidic properties selectively catalyze the ring-shift isomerization of perhydrofluorene with high yields of the dodecahydrocyclopenta[a]naphthalene and dodecahydrophenalene. Such hydroisomerization reaction is enhanced above 250°C, while more cleavage of carbon−carbon bond occurs at higher temperatures (280−290°C) which lead to the great production of single-ring cycloalkanes and more loss in carbons. In the comparative study of the support effect, an examination of the product yields indicates that mild acidity and unique zeolitic structure of Y-zeolites show a major contribution to the selective ring-shift isomerization of saturated aromatic rings. In addition, the generation of mesopores in the Y-zeolite crystals by postsynthesis alkaline treatment facilitates the mass transfer of compounds and provides an improved yield of isomers.

Shape selectivity effects in the hydroconversion of perhydrophenanthrene over bifunctional catalysts

“…Still, both zeolites produced significant amounts of alkyladamantanes, whereas ASA had a much lower selectivity to these products. The low adamantane selectivity of ASA is View Article Online coherent previous work: 37 the hydroconversion fluorene over Pt/ASA produced only very little adamantane products. This result is somewhat surprising, since ASA may accommodate large molecules such as alkyladamantanes thanks to its large pore size (pore diameter of 70-80 Å).…”

“…Wang et al studied the hydroconversion of fluorene on Pt-supported catalysts. 37 Higher yields of perhydrophenalene, precursors of alkyladamantanes, and propyladamantanes were obtained over the USY zeolite, in comparison to Beta. In our case, as shown in Fig.…”

“…[22][23][24][25][26][27][28][29][30][31] The knowledge of reaction routes involved in the conversion of heavy and/or polycyclic naphthenes containing more than two cycles is scarcer. 11,[32][33][34][35][36][37][38] In a preceding study, we established hydroisomerization and hydrocracking pathways of perhydrophenanthrene (PHP), a 3-cycle naphthene, over a bifunctional Pt/USY catalyst. 39 The model molecule was first isomerized to ring-shift and ringcontraction compounds.…”

Highly Efficient Hydroisomerization of Endo-Tetrahydrodicyclopentadiene to Exo-Tetrahydrodicyclopentadiene over Pt/HY

“…In order to confirm the change in the coordination environment for the aluminum in the samples, the 27 Al magic-angle spinning (MAS) NMR spectra of HY, Pt/HY-BQ, and Pt/HY were recorded and are shown in Figure 4. In all spectra of the samples, there were two signals with chemical shifts at 60 and 0 ppm corresponding to the tetrahedral aluminum species in the framework and octahedral extraframework aluminum, respectively.…”

“…It is not yet clear whether the Ni on Ni/H-β could actually be beneficial to suppress the formation of coke and enhance the stability of the process. In general, for the isomerization of many alkanes catalyzed by acid zeolites, the unsaturated species which lead to the rapid formation of coke are intermediates or products formed during the isomerization process. , Under a H 2 atmosphere, these coke precursors could be converted to saturated hydrocarbons catalyzed by metallic sites for hydrogenation and then removed, resulting in suppressing the coke formation. − …”