High-pressure liquid phase hydroconversion of heptane/nonane mixtures on Pt/H-Y zeolite catalyst

Abstract

The competitive hydroconversion of heptane and nonane molecules in their mixture was studied in a continuous flow, fixed-bed reactor filled with Pt/HY zeolite catalyst. Liquid-phase reaction conditions were established at reaction temperatures of 230, 250, and 270 • C by pressurizing the reactor at 100 bar. Hydrogen was supplied in an absorbed state with the liquid hydrocarbon feed. Under these liquidphase reaction conditions, the apparent reaction rates of heptane and nonane were almost identical. In a similar experiment under vaporphase conditions, nonane was much more reactive than heptane. The conversion data under liquid-phase conditions were analyzed with an adsorption-reaction model based on intrinsic kinetic parameters obtained from vapor-phase experiments. The model revealed that the enhanced reactivity of heptane in the liquid phase was due to its preferential adsorption. Simulation of the adsorption of the heptane/nonane mixture in the pores of zeolite Y with the configurational-bias Monte Carlo method confirmed the preferential adsorption of heptane in zeolite Y at high pressure. Under such conditions, in zeolite Y supercages the packing of the smaller heptane molecules is more favorable than that of the larger nonane molecules.

A Two-Phase Reactor Model for the Hydrocracking of Fischer−Tropsch-Derived Wax

“…These observations are further supported by Denayer et al, 21 in which it was shown that the reaction in the liquid phase was essentially unaffected by the differences in adsorption, in contrast to that observed in similar experiments in the gas phase. The assumption of equal molar loadings for all hydrocarbons is inherent in the LH approach.…”

“…21,30,31,34 Thus, the competition between isomerization, dehydrogenation, and -scission is severe. For medium-pore zeolites, the isomerization remains constrained and is faster than -scission.…”

“…These patterns in the hydrocracking were recognized by Archibald et al 14 and formulated into a semilumped model by Stangeland. 15 The single events concept [10][11][12][13][16][17][18][19][20][21][22][23][24] has been developed extensively to represent the elementary steps in the reaction pathway, including adsorption and Langmuir-Hinshelwood (LH)-type kinetics. This elegant technique leads to millions of reaction steps (e.g., C 15 and C 25 have 4347 and 30 million paraffinic isomers, respectively) and soon becomes impractical for even moderately sized hydrocarbon molecules, without some form of lumping.…”

Adsorption and Reaction in Confined Spaces

“…For example, it is well accepted that in gas phase conditions at low degree of pore occupancy, longer hydrocarbon chains are adsorbed more selectively than their shorter homologues on most zeolites because of the larger interaction energy [3][4][5][6]. This results in the selective catalytic conversion of the longer chains from mixtures of short and long chains, which already demonstrates the link between adsorption and catalysis on microporous solids [7].…”

Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

“…Recently, it was shown that in hydroconversion of alkane mixtures the molecular competitions in the liquid phase are very different from those in the vapor phase (83,84). The competitive hydroconversion of n-heptane and n-nonane in their mixture at vapor-and liquid-phase reaction conditions was studied on Pt loaded USY and HY zeolite catalysts.…”