Optimization of the Metal Phase Composition of Ir–Pd/SiO2–Al2O3 Catalysts to Increase Thiotolerance in Selective Ring Opening of Decalin

Thioresistant PdPt/Al/SBA-15 for Naphthalene Hydrogenation

“…Very interestingly, after S addition, trans- decalin was the only identified isomer over bimetallic NM formulations (Figure a,b and Table S3). That suggested weaker tetralin adsorption over strongly diminished adsorbing sites (due to S-poisoning) over NM alloyed particles . Although debilitated T adsorption could originate from electron transfer at this point, it was not possible to clearly discern if that phenomenon was related to either NM-protonic site (on support surface) interaction or Pt electronic transfer to Pd (or even to both phenomena).…”

“…In full agreement, the augmented Stolerance of Ir−Pd catalysts (in the selective decalin ring opening, 10−20 ppm of S, as thiophene) was related to both modifications of the electronic properties of NM particles provoked by component alloying and their interaction with surface Brønsted acid sites on the silica−alumina carrier. 73 In the same line, from their studies on Pt−Pd/silica−alumina formulations in the tetralin saturation, Lercher at al. 71,74 concluded that under S-and N-poisoning conditions (100 ppm of S as DBT and 20 ppm of N as quinoline, respectively), carrier surface protonic acidity could be determining the hydrogenation rate by providing sites where aromatic molecules (tetralin in this case) could be adsorbed.…”

“…That suggested weaker tetralin adsorption over strongly diminished adsorbing sites (due to S-poisoning) over NM alloyed particles. 73 Although debilitated T adsorption could originate from electron transfer at this point, it was not possible to clearly discern if that phenomenon was related to either NM-protonic site (on support surface) interaction or Pt electronic transfer to Pd (or even to both phenomena). However, an important clue was that trans-decalin formation was similar regardless of the support, thus pointing out to the electron transfer from Pt to Pd as the main cause, considering the absence of protonic sites on the alumina surface.…”

“…76 Indeed. under S-free decalin ring opening on Ir−Pd/SiO 2 −Al 2 O 3 , it was found 73 that the metallic phase dictated the reaction mechanism followed; meanwhile, after thiophene addition, that surface became poisoned (by strongly adsorbed S). Thus, the acid function was dominant under those circumstances providing the necessary decalin adsorption sites.…”

“…Conversely, because of its increased thermodynamical stability, the trans-one could be converted (under more demanding operating conditions) to lighter cracked species. 73,80 It is worth mentioning that the Pt/Al/SBA-15 formulation highly active under S-free conditions (Table 3) could possibly be an attractive candidate to be applied in N saturation focused in obtaining enhanced T yields at low consecutive conversion to D. Indeed, in other schemes (as hydrogen storage material, for example, due to its stronger dehydrogenation capability compared to that of decalin), tetralin commercial value could be higher than that of D. 81,82 Superior properties of platinumalone catalysts have been found, compared to those of other noble metals, in such reaction schemes. 83 The great potential of NM-based catalysts supported on SBA-15 mesoporous silica modified by grafted aluminum at the concentrations studied in the present work was clearly demonstrated; meanwhile, deep insight on the reason for those outstanding properties in aromatic hydrogenation has been gained.…”