Sindhu Seelan

Catalysis by Gold Nanoparticles: Epoxidation of Propene

Supported nano-gold catalysts have attracted rapidly growing interest due to their potential applicability to various reactions of industrial and environmental significance. In this article, we focus on the advances related to the direct vapor-phase oxidation of propene to propene oxide in the presence of molecular oxygen and hydrogen over gold catalysts supported on Ti-incorporated silica materials prepared by different methods. The importance of catalyst preparation and pretreatment method, nature of support material, Au particle size and loading amount is emphasized. Possibilities to enhance the catalyst performance by using promoters and by silylation are also discussed.

Hydrophobicity induced vapor-phase oxidation of propene over gold supported on titanium incorporated hybrid mesoporous silsesquioxane

Gold nanoparticles supported on highly hydrophobic ethane bridged Ti incorporated mesoporous organosilica are reported for enhanced vapor phase epoxidation of propene using H2 and O2.

Enhancing activity and stability of Burkholderia cepacia lipase by immobilization on surface-functionalized mesoporous silicates.

Burkholderia cepacia lipase was immobilized on various types of phenyl-functionalized mesoporous silicates (MPS). MPS, anchored with a phenyl group on the silica wall and with three dimensional (3D) mesoporosity, showed highest lipase adsorption capacity and best activities both in aqueous and organic reagents.

Vapor-phase epoxidation of propene over Au/Ti-MCM-41 catalysts: influence of Ti content and Au content

Ti-MCM-41 samples were used for propene epoxidation using H2 and O2 after Au deposition by deposition--precipitation. Au nanoparticles supported on Ti-MCM-41 with Ti incorporated hydrothermally followed by post-synthesis grafting gave higher propene oxide yields than Ti-MCM-41 with Ti incorporated hydrothermally or by grafting. Au L3-edge EXAFS spectra show the presence of metallic Au for the low Au content (0.21 wt%) catalyst which is more selective to epoxidation, while at high Au loadings (0.42 wt%) oxidic Au species are observed and the catalyst shows lower epoxide selectivity.

Catalytic activity of aryl alcohol oxidase immobilized in 3D-mesoporous silicates.

Aryl alcohol oxidase was immobilized on two mesoporous materials, MS-A and MS-B. The immobilization rate for the larger pore material MS-A (11.5 nm) was higher than for the smaller pore material MS-B (4.2 nm). Furthermore, the sol-gel silica encapsulation of MS-immobilized enzymes improved thermal stability.

Macroporous Ceramics Coated with Mesoporous Layer for Enzyme Encapsulation

Mesoporous silica with 5~10 nm pore size was coated over recycled ceramic, prepared from lake sludge, with pore size 100-200μm. The mesoporous silica coated ceramic was characterized by XRD, N2 sorption, SEM and TEM. The results clearly showed the formation of mesoporous coating on the macroporous ceramics. These ceramics with the mesoporous coating are specially suitable for stabilization of enzymes. The mesopore stabilized enzymes are recyclable catalysts and showed comparable performance with the free enzyme.

Hyperstructured Hydroxyapatite Ceramics as a Carrier for Cell and Protein

The preparation of hyperstructured hydroxyapatite (HAp) ceramics is reported. Mesoporous silica with nano size pore was coated on the bi-modal type porous HAp ceramics with pore size 100-200 µm and 1-2 µm. The mesoporous silica coating was done using two different procedures and the ceramics were characterized by XRD, N2 Sorption, SEM/EDX, and TEM. The results clearly showed the formation of mesoporous coating on the large pores of parent HAp ceramics. SEM images reveal that the mesoporous coatings consists of almost spherical particles with relatively uniform sizes of ~1 µm. Protein adsorption and release behavior on these mesoporous coated HAp ceramics was evaluated using UV-VIS spectrometry. The large pores are suitable for cell immobilization, and the mesopores several nm in size were found to enhance protein encapsulation ability.