2.1. Bimetallic catalystsThe first formulation of the naphtha reforming catalyst, whichwas introduced in 1949 by UOP, consisted of monometallic platinumsupported over chloride alumina (Pt/Al2O3–Cl) [16,17]. In orderto slow down the coking of this kind of catalyst, high hydrogenpressures were used, which are thermodynamically not favorable.The development of bimetallic catalysts permitted this hydrogenexcess to decrease considerably and improved the catalyst efficiencyof metal [18–22]. Some of the added metals have catalyticproperties on their own (Ir, Rh, Re), while others, such as Sn, Geare catalytically inactive. The addition of second metal to Pt wasstarted in 1968 by adding Re to the metal function [23], which contributedto reduction in the catalyst deactivation rate and improvementin catalytic properties such as hydrogen uptake andenhancement in aromatic yields [24,25]. In 1969, the effect of additionof Sn to the metal function was examined [26]. Addition of tinprevents coke deposition on the Pt metal particles and support, andalso enhances the selectivity to aromatics and the stability of Pt/Al2O3 [27–31]. Pt–Sn catalysts are regenerate easily, thus theyare used in the systems in which the catalyst is regenerated continuously[32,33]. Addition of germanium to monometallic platinumsupportedcatalysts was studied in 1971 [34]. This practice contributesto improvement in the catalyst selectivity and stability, aswell as enhancement of the thioresistance of platinum at reactionconditions [18]. In 1976, addition of Ir and In were considered[35,36]. Pt–Ir catalysts had a strong hydrogenolytic capacity andsulfiding pretreatments had to be incorporated in the industrialpractice to prevent the dangerous exothermal runaway producedby massive C–C bond cleavage of the feedstock in the early stagesof the reaction [37]. Indium improves the resistance to deactivationby coke formation and enhance the aromatization/cracking ratio of the reforming reaction and increases the production of gasoline[38,39].
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