V and Cr substitution in dicalcium silicate under oxidizing and reducing conditions - Synthesis, reactivity, and leaching behavior studies.

Dicalcium silicate (C2S) is known to incorporate potentially hazardous metals (Cr and V) in a belite-rich cementitious system. The effect of the electrovalence nature of V and Cr on C2S polymorphs' (α´, ß, γ) stability under oxidizing and reducing conditions as well as their reactivity are systematically investigated via analyzing oxidation states, phase composition, bonding system, and microstructure as well as oxide composition quantitively. It is shown that C2S can incorporate Cr (VI) and V(V) consequently leading to stabilization of α´, ß-C2S. Instead, Cr (II, III) and V < (V) tend not to substitute in C2S. Despite reactive polymorphs (α´, ß-C2S) stability due to Cr (VI) and V(V) incorporation, the early age (48-72 h) C2S reactivity is drastically reduced due to Cr (VI) and V (V) incorporation. Moreover, one batch leaching test revealed that the V (V) leaching is inversely proportional to aqueous Ca2+ ion at pH > 12 while Cr leaching is sensitive to its oxidation state, and dissolution of C2S. Even though C2S can incorporate Cr (VI) and V (V) ions, the final leaching is governed by the immobilization potential of C-S-H gel, pH as well as types of calcium chromate and vanadate complexes.

Platinum-promoted Ga/Al2O3 as highly active, selective, and stable catalyst for the dehydrogenation of propane.

A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt% Ga, and 0.25 wt% K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga(3+) species are the active species and where Pt functions as a promoter.