Abstract

Catalytic hydrogenation of anthracene was studied over Ni supported on Hβ-zeolite catalyst under supercritical carbon dioxide (sc-CO2) solvent. Hydrogenation of anthracene in sc-CO2 yielded 100% conversion at 100 °C, which is attributed to the reduced mass transfer limitations, and increased solubility of H2 and substrate in the reaction medium. The total pressure of 7 MPa was found to be optimum for high selectivity of octahydroanthracene (OHA). The conversion and selectivity for OHA increased with an increase in H2 partial pressure, which is attributed to higher concentration of hydrogen atoms at higher H2 pressures. The selectivity reduced the pressure below 7 MPa because of enhanced desorption of the tetrahydro-molecules and intermediates from Ni active sites, due to higher solubility of the surface species in sc-CO2. The selectivity of OHA increased with the increase in catalyst weight and reaction time. The rate of hydrogenation of anthracene was compared with that found for napthalene and phenanthrene. The use of acetonitrile as co-solvent or expanded liquid with CO2 decreased the catalytic activity.

Highlights

  • Cyclic saturated hydrocarbons are proposed as a new mobile hydrogen storage media for proton exchange membrane fuel cells [1,2,3,4]

  • The present study aims at fine tuning reaction conditions for the catalytic hydrogenation of anthracene over nickel supported on Hβ-zeolite catalyst using supercritical carbon dioxide as solvent

  • The results indicate that using sc-CO2 as a solvent 100% hydrogenation of anthracene was achieved at 100 °C over 40 wt./% Ni/Hβ-zeolite, which is attributed to the reduced mass transfer limitations, and increased solubility of H2 and substrate in the dense CO2 medium

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Summary

Introduction

Cyclic saturated hydrocarbons are proposed as a new mobile hydrogen storage media for proton exchange membrane fuel cells [1,2,3,4]. Polycyclic aromatic compounds (PAHs) are components of coal tar, creosote and crude oil, and are formed by incomplete combustion of organic materials Because of their carcinogenic and mutagenic properties, PAHs are regarded as environmental priority pollutants [9,10]. The ability of the sc-CO2 to dissolve many of reactive gases like H2, O2 and a variety of organic compounds facilitates oxidation and hydrogenation reactions in this medium, thereby eliminating inter-phase mass transfer limitations and enhancing the reaction rate. Shirai et al [18], studied the hydrogenation of naphthalene and 1-naphthol over supported metal catalysts in sc-CO2 solvent. The present study aims at fine tuning reaction conditions for the catalytic hydrogenation of anthracene over nickel supported on Hβ-zeolite catalyst using supercritical carbon dioxide as solvent. In this study we looked at the use CO2 expanded acetonitrile for the hydrogenation of anthracene

Catalyst Characterization
Effect of Reaction Temperature on Hydrogenation of Anthracene
Effect of Nickel Loading on Hydrogenation of Anthracene
Effect of Reaction Pressure on Hydrogenation of Anthracene
Effect of Hydrogen Partial Pressure on Hydrogenation of Anthracene
Effect of Catalyst Weight on Hydrogenation of Anthracene
Effect of Reaction Time on Hydrogenation of Anthracene
Effect of Solvent on Hydrogenation of Anthracene
Reaction Mechanism of Anthracene Hydrogenation
Catalyst Preparation
Catalytic Reactions
Conclusions
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