K. Tenchev

Catalytic performance of Ni-Al layered double hydroxides in CO purification processes

Ni-Al layered double hydroxides with Ni2+/Al3+ molar ratios of 1.5 and 3.0 have been synthesized by co-precipitation and studied as catalyst precursors for purification of CO-containing gas-mixtures by means of CO oxidation to CO2 and conversion of CO by water vapor (water-gas shift reaction). The influence of the alkali additives (K+ ions) on the water-gas shift activity has been also examined. It was established that the catalytic activity of both reactions increases with the temperature and the nickel content. Hypothetic schemes are proposed about activation of the catalysts in the WGSR and CO oxidation including redox Ni2+ ↔ Ni3+ transition on the catalyst surface. The activity in WGSR is positively affected by the presence of potassium promoter, depending on its amount. The sample with higher nickel loading is the most effective catalyst as for CO oxidation as well as for WGSR at intermediate temperatures after potassium promotion.

Benzene alkylation with propane on Ga and Pt modified ZSM-5

Alkylation of benzene with pure propane under flow condition has been studied on series of monometal Ga and bimetal Ga-Pt modified H-ZSM-5 zeolite. The main reaction product is methylbenzene. The nature of Ga species has been studied and correlated with the catalytic performance of these materials. Ga in the high gallium loaded samples presents as two oxide phases: extraframework Ga 2 O 3 (phase I) and gallium oxide strongly interacting with zeolite (phase II). Ga in the low gallium loaded samples form phase II. Phase II is responsible for higher catalytic activity of this catalyst. Several Pt oxide species are formed on the support as a function of calcinations temperatures. Part of Pt remains in irreducible state even after calcinations at high temperature. Addition of Pt to the monometal Ga-ZSM-5 improves catalytic activity and the Ga/Pt ratio plays significant role. High Pt concentration provokes additional coke deposition on the zeolite support.