Platinum supported on coprecipitated SnZnAl2O4

Cu/MgAl(2)O(4) as bifunctional catalyst for aldol condensation of 5-hydroxymethylfurfural and selective transfer hydrogenation

Copper supported on mesoporous magnesium aluminate has been prepared as noble-metal-free solid catalyst for aldol condensation of 5-hydroxymethylfurfural with acetone, followed by hydrogenation of the aldol condensation products. The investigated mesoporous spinels possess high activity as solid-base catalysts. Magnesium aluminate exhibits superior activity compared to zinc and cobalt-based aluminates, reaching full conversion and up to 81 % yield of the 1:1 aldol product. The high activity can be correlated to a higher concentration of basic surface sites on magnesium aluminate. Applying continuous regeneration, the catalysts can be recycled without loss of activity. Focusing on the subsequent hydrogenation of aldol condensation products, Cu/MgAl2 O4 allows a selective hydrogenation and CO bond cleavage, delivering 3-hydroxybutyl-5-methylfuran as the main product with up to 84 % selectivity avoiding ring saturation. Analysis of the hydrogenation activity reveals that the reaction proceeds in the following order: CC>CO>CO cleavage>ring hydrogenation. Comparable activity and selectivity can be also achieved utilizing 2-propanol as solvent in the transfer hydrogenation, providing the possibility for partial recycling of acetone and optimization of the hydrogen management.

As a Whole: Crystalline Zinc Aluminate Nanotube Array−Nanonet

A large-area crystalline zinc aluminate nanotube array on its own nanonet was prepared by thermal replication on an anodized aluminum oxide template and through the gas-solid reaction between Zn vapor, Al2O3, and residual O2 or produced H2O. The free-standing nanotube array plus the nanonet structure, as a whole, was at least 900 mum2 in area. Each nanotube, 70-80 nm in diameter, was seamlessly connected to an underlying pore in the nanonet and was about 800 and 15 nm in length and wall thickness, respectively. The nanonet was about 20 nm thick. Both the ZnAl2O4 nanotube and nanonet were in face-centered cubic crystal form and grew along the [12] direction.