Shaping of mesoporous AISBA-15 as cylindrical nano reactor for tertiary butylation of phenol.

Mesoporous AISBA-15 with different n(Si)/n(Al) ratios (45, 136 and 215) in the powder (P) form were synthesized by hydrothermal technique. The powder materials were shaped into cylindrical extrudates (Ex) by compounding with additives such as bentonite (binder) and methylcellulose (plasticizer). The AISBA-15 materials were characterized by XRD, N2 adsorption, AAS, 27Al MAS-NMR and thermogravimetric analysis. The orderly growth of AISBA-15 is evidenced by its XRD patterns. The surface area and pore volume of AISBA-15 catalysts were around 950 m2/g and 1.3 cm3/g respectively. A decrease in surface area and pore volume were observed for AISBA-15 (Ex) materials in comparison to AISBA-15 (P) materials. This may be due to partial blocking of pore entry and surface area coverage of additives during the shaping of extrudates. Vapor phase alkylation of phenol with tert-butanol was carried out over AISBA-15 (P) and AISBA-15 (Ex) catalysts and the results revealed that both powder and extrudate samples showed similar activity for phenol conversion. The activity of AISBA-15 catalysts follows the order: AISBA-15 (45) > AISBA-15 (136) > AISBA-15 (215) for both powder and extrudate forms. The major products were 2-tert-butylphenol (2-TBP), 4-tert-butylphenol (4-TBP) and 2,4-di-tert-butylphenol (2,4-DTBP). The selectivity to para product is much higher than other products. The catalyst exhibited steady conversion, and deactivation by coke formation of the catalyst is much reduced in AISBA-15 materials.

Immobilization of cytochrome c on the cylindrical mesoporous silica extrudates.

Siliceous and aluminum containing C12-MCM-41, C16-MCM-41 and SBA-15 mesoporous molecular sieves were synthesized in the powder (P) form by hydrothermal method. These materials were shaped into cylindrical extrudate (Ex) form by compounding with additives such as bentonite (binder), methyl cellulose and water. The adsorption of cytochrome c (cyt c) onto the extrudates of these mesoporous molecular sieves was studied at different solution pH. It was observed that maximum adsorption was found to be near the isoelectric point (pI) of the protein. The extrudates of SBA-15 showed a maximum amount of cyt c adsorption capacity and this may be due to the high pore volume and large pore diameter compared to other C12-MCM-41(Ex) and C16-MCM-41(Ex). Incorporation of aluminium in to the siliceous material showed maximum adsorption of cyt c compared to pure siliceous materials. The observed consequence may be due to the strong electrostatic interaction between the negative charges on the aluminium sites and positively charged amino acid residues of cyt c.

Controlled manipulation of rigid nanorods by atomic force microscopy.

The motion of rigid nanorods caused by the normal vibrations of a nanotip rastering a flat surface is described within an original collisional model. Provided that the friction between the nanorods and the surface is sufficiently high, the direction of motion and the orientation of the nanorods are determined by two pairs of differential equations. In the limiting case of thin nanowires, the direction of motion is precisely related to the length of the nanowire, the tip radius and the density of the scan lines. At the same time the wire oscillates perpendicularly to this direction in a characteristic wobbling motion. Similar conclusions approximately hold also when the rod thickness is not negligible (compared to its length), as shown by a comparison between numerical solutions of our model and measurements on gold nanorods manipulated on a silicon oxide surface. Our results open the path to understanding and controlling the manipulation of arbitrarily shaped nanoparticles.

Nanoporous reactor with tunable selectivity on alkylation of ethylbenzene.

As nanoporous reactor, mesoporous silicates containing aluminum acidic site with n(Si)/n(Al) ratio up to 7 (AISBA-15) were prepared through a simple one-pot synthesis, which was recently developed by parts of us. The obtained materials were satisfactorily characterized by XRD and nitrogen adsorption/desorption and have regularly arranged hexagonal structures with pore diameters in the 9.6-11.8-nm range. The density and strength of the acid sites were determined using temperature-programmed desorption (TPD) of pyridine and controlled distribution between weak, moderate, and strong acid sites was demonstrated. The alkylation of ethylbenzene in a fixed-bed flow-type reactor using the AISBA-15 nanoporous reactor was carried out under various conditions such as temperature, feed ratio, flow rate, and time on stream. Interestingly, perfect regioselectivity between the m-isomer and the o-/p-isomers of diethylbenzene was achieved, where 100% selectivity of the m-isomer or the o-/p-isomers can be obtained by simply tuning the reaction temperature by using AISBA-15 catalyst with appropriate aluminum content.