Modification of acid supports by solid-state redox reactionPart I. Preparation and characterization

Preparation of Gallium‐Containing Catalysts by Solid‐State Reaction of Acidic Zeolites with Elemental Gallium

“…The formation of 1 mol H 2 per mol gallium corresponds to an average Ga oxidation state of +II, which might be explained by the coexistence of the more stable gallium oxidation states +I and +III. Our results are at variance with those of Hagen et al [13] who observed only one signal with a maximum at ca. 420 C in the temperatureprogrammed hydrogen evolution during the solid-state reaction of H-ZSM-5 with elemental Ga. Their signal corresponds to the low-temperature signal detected in the present work.…”

“…This would suggest that the two different hydrogen signals can rather be assigned to different gallium species (Ga + und Ga 3+ ) than to different hydrogen sources. FTIR measurements on zeolite 4.3Ga/H-Beta after stopping the reaction at 500 C, however, resulted in a nearly as high amount of reacted Brùnsted acid sites than for the solid-state reaction at temperatures up to 700 C. The hydrogen signal at about 420 C observed by Hagen et al [13] in the solid-state reaction of H-ZSM-5 with Ga also supports the above-described assignment of the hydrogen signals to different gallium oxidation states. The amounts of hydrogen evolved during the reaction correspond to a Ga oxidation state of slightly more than one (n H2,total /n Ga = 0.557) [13].…”

“…The same reaction was shown to occur with NH 4 -mordenite [11] or H-ZSM-5 [12]. Very recently, Hagen et al [13,14] expanded the solidstate reaction to various kinds of proton-containing supports (zeolite ZSM-5 and zeolite Y, silica and c-alumina) and low-melting (non-noble) metals such as Zn, Mg, Mn, Fe and Ga, with a focus on the zinc-containing systems. In this work, the solid-state reaction of acidic zeolites with elemental gallium was studied.…”

Efficient Synthesis of Polyhydroquinolines via the Hantzsch Reaction Using Iron Loaded Mesoporous Materials

“…catalysis, medicine, material science etc. These iron loaded MCM-41 materials have received much attention because of their redox properties and unusual activity in organic reactions [11][12][13] which is higher compared to conventional mineral acids, 14 Lewis acids. 15 The use of iron loaded mesoporous materials as catalyst can also eliminate the hurdles like pore size constraint, recyclability, thermal and hydrothermal stability posed by other support materials.…”

Waste-free Soft Reactive Grinding Synthesis of High-Surface-Area Copper–Manganese Spinel Oxide Catalysts Highly Effective for Methanol Steam Reforming

“…The most unsatisfactory aspect of the coprecipitation routes is the need of subsequent calcination at temperatures higher than 500°C to induce the crystallization of Cu-Mn spinel phases, which however leads to undesirable sintering, grain growth, and dramatic loss of specific surface area in many cases [3,4,11,12]. Moreover, the use of vast amounts of water as well as formation of large amounts of gaseous or liquid wastes presents additional environmental problems [17,18]. In view of these circumstances, the development of new practical and environmental friendly synthetic methods for preparation of a high surface area coppermanganese spinel catalyst system is highly desirable.…”