Abstract
Abstract Equilibrium adsorption isotherms were obtained experimentally by a static method for a binary component hydrogen-methane mixture on activated carbon and 5A molecular sieve adsorbents. The temperature range 303-333 K and pressure range 0 - 4 MPa were examined. Methods for predicting gas-mixture equilibrium adsorption data from the pure-component isotherms were evaluated. Extended Langmuir model correlated the adsorption of binary mixtures fairly well. In all cases mutual interference was found, that is, the amount of a given gas adsorbed at a given partial pressure was always less in the mixture than it would have been if the other gaseous component had not been present. It was found that the amount adsorbed of gases per unit bulk volume for 5A molecular sieve was higher than for activated carbon. Furthermore, 5A molecular sieve showed better adsorption characteristics than activated carbon in mass transfer properties, affinity, selectivity and heat of adsorption.
Highlights
Off-gas of Iraqi north refineries usually contains large amounts of hydrogen and heavier hydrocarbons and sometimes impurities, such as sulfur compounds, water vapor and carbon dioxide
BET and other equations that represent multi-layer adsorption were excluded because it is unlikely that multi-layer adsorption could have occurred in this study where all temperatures were above the critical (Wu et al, 2007; Dąbrowski, 2001)
Equilibrium adsorption data for hydrogen - methane mixtures on activated carbon and 5A molecular sieve are presented in the form of x - y diagrams at four different temperatures and shown in Figures 7 and 8, respectively
Summary
Off-gas of Iraqi north refineries usually contains large amounts of hydrogen and heavier hydrocarbons and sometimes impurities, such as sulfur compounds, water vapor and carbon dioxide. A large spectrum of inorganic (silica gels, alumina, zeolites), organic (activated carbons) and polymeric adsorbents is commercially available to carry out many separations of practical interest These adsorbents offer a wide range of physical (micro- and macro-porosity, particle shape, size and strength) and chemical (hydrophobicity, surface polarity and ion exchangeability) characteristics to choose from. Activated carbon and 5A molecular sieves were selected as the best adsorbents for hydrogen recovery by adsorption processes (Teiseh and Capareda, 2010). The average equivalent particle diameters were found to be equal to 3.971 and 3.789 mm for activated carbon and 5A molecular sieve, respectively Both adsorbents were regenerated with a vacuum oven (Gallenkamp) which was operated at 10 kPa pressure and 373 K temperature overnight, in order to remove previously adsorbed gases from the adsorbent surfaces. Brazilian Journal of Chemical Engineering Vol 35, No 02, pp. 795 - 804, April - June, 2018
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