The development of dependable, environmentally benign processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In the present study, we report one-pot biogenic fabrication of palladium nanoparticles by a simple procedure using broth of Cinnamomum camphora leaf without extra surfactant, capping agent, and/or template. The mean size of palladium nanoparticles, ranging from 3.2 to 6.0 nm, could be facilely controlled by merely varying the initial concentration of the palladium ions. The polyols components and the heterocyclic components were believed to be responsible for the reduction of palladium ions and the stabilization of palladium nanoparticles, respectively.National Natural Science Foundation of China [20776120, 20576109]; National High Technology Research and Development Program of China [2007AA03Z347]; Natural Science Foundation of Fujian Province of China [2008J0169

Role of pentahedrally coordinated titanium in titanium silicalite-1 in propene epoxidationA new pentahedrally coordinated Ti was discovered in TS-1 and showed a higher catalytic activity than the tetrahedrally coordinated one.Two titanium silicalite-1 samples with different crystal sizes were synthesized in the tetrapropylammonium bromide (TPABr) and tetrapropylammonium hydroxide (TPAOH) hydrothermal systems. The small-crystal TS-1 with a size of 600 nm was then treated with different organic bases. These TS-1 samples were evaluated in the epoxidation of propene, and characterized by ultraviolet-visible diffuse reflectance (UV-vis), X-ray absorption near edge structure (XANES) and Raman spectroscopies. The Ti L-edge absorption spectra show that a new Ti species, pentahedrally coordinated Ti, appears in some of the samples. This pentahedrally coordinated Ti species is correlated with the catalytic oxidation activity of TS-1, closely. Tetrahedrally coordinated Ti in TS-1 is the primary active center for selective oxidation reactions, but the existence of a small amount of pentahedrally coordinated Ti can further improve the catalytic activity. A high molar ratio of Si/Ti (n(Si/Ti)) in the synthesis process (n(Si/Ti)=92.78) was beneficial for the generation of pentahedrally coordinated Ti. The improved catalytic activity of the TPAOH treated TS-1 is mainly due to the increasing amount of pentahedrally coordinated Ti, besides the elimination of diffusion limitation. Slowing down the crystallization rate can also increase the content of pentahedrally coordinated Ti.

Titanium silicalite-1 (TS-1) was extruded with silica and alumina supports, and then the extrudates were treated with dilute tetrapropylammonium hydroxide (TPAOH) solution. The treated TS-1 extrudates were characterized and evaluated in the epoxidation of propene. The two supports exhibited different properties after the treatment. The dissolution of silicon, forming hollows in the TS-1 crystals, preferably occurred when alumina support was used. The inhibition of generation of hollows in the silica supported TS-1 arose from the dissolution and recrystallization of silica support. The crystallization of support also led to the unblocking of inherent micropores, which was beneficial for improving the catalytic performance. Alumina support showed a different result. A very small amount of aluminum was inserted into the framework of TS-1, but the small amount of framework Al caused a sharp increase of the acid amount, and thus a low selectivity of propene oxide and poor catalyst stability in propene epoxidation.