Promotional effect of Pd addition on the catalytic activity of composite Pt-Pd/AlSBA-15–β\beta catalyst for enhanced n-heptane hydroisomerization

Hierarchical AlSBA-15–zeolite materials were utilized as a supports for preparing hydroisomerization catalysts. Detailed consideration was given to: (i) the effect of the zeolite type introduced into AlSBA-15–zeolite composites (where zeolite is β, mordenite or ZSM-5) as well as (ii) the promotion effect of Pd addition. The composites showed higher activity in isomerization as compared to Pt/AlSBA-15. The enhanced isomerization efficiency were explained by the appropriate metallic and acidic function as well as suitable transport properties. The modification of the hydrogenating function by Pd incorporation increases the hydroisomerization efficiency of Pt-Pd/AlSBA-15–β catalyst. Over bimetallic Pt-Pd/AlSBA-15–β, the high yields of isomers (68 wt%) with respect to 50 wt% for a control catalyst. The most promising Pt-Pd/AlSBA-15–β catalyst allows to improve research octane number from 0 to the 74 value

Soot combustion over niobium-doped cryptomelane (K-OMS-2) nanorods : redox state of manganese and the lattice strain control the catalysts performance

A series of Nb-doped (0–23 wt%) cryptomelane catalyst (Nb-K-OMS-2) was synthesized and thoroughly characterized by XRD, TEM/EDX, XRF, XPS, XAS, UV-Vis, and Raman techniques corroborated by the work function measurements. The obtained catalysts were tested for soot oxidation (Printex U) in model tight and loose contact modes. It was shown that the catalytic properties of the Nb-K-OMS-2 are controlled by the amount of Nb dopant in a strongly non-monotonous way. The introduction of niobium gives rise to the strain in the cryptomelane lattice, accompanied by significant Mn+3/Mn+4 ratio variations and concomitant work function changes. The isotopic exchange experiments revealed that the catalytic activity of the Nb-OMS-2 catalysts in soot combustion proceeds via the pathways, where both the activated suprafacial 18O and the surface 16O2− species participate together in the reaction. The niobium doping level controls the non-monotonous changes of the catalyst work function and the lattice strain, and variations of these parameters correlate well with the observed deSoot activity. To our best knowledge, the role of the lattice strain of the cryptomelane catalysts was documented for the first time in this study