Dongyuan Zhao

Strongly Acidic and High-Temperature Hydrothermally Stable Mesoporous Aluminosilicates with Ordered Hexagonal Structure

Publisher Summary This chapter discusses strong acidic and high-temperature hydrothermally stable mesoporous aluminosilicates with well-ordered hexagonal structure. These mesoporous aluminosilicates have been successfully synthesized from the assembly of preformed aluminosilicate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The MAS-5 shows extraordinary stability both in boiling water and in steam. Temperature-programmed desorption of ammonia (NH3) shows that the acidic strength of MAS-5 is much higher than that of MCM-41.

A new class of hybrid mesoporous materials with functionalized organic monolayers for selective adsorption of heavy metal ions

Thiol- and amino-functionalized SBA-15 silicas with uniform mesoporosities were prepared and employed for removing heavy metal ions from waste water; the thiolated SBA-15 adsorbent exhibited a higher complexation affinity for Hg2+, while the other metal ions (Cu2+, Zn2+, Cr3+ and Ni2+) showed exceptional binding ability with its aminated analogue.

Highly ordered large caged cubic mesoporous silica structures templated by triblock PEO–PBO–PEO copolymer

Highly ordered, hydrothermally stable, caged cubic mesoporous silica structures (Imm) with unusually large pore size (120 A) have been synthesized by using hydrophobic poly(butylene oxide) containing triblock PEO–PBO–PEO copolymer as a structure-directing agent.

Performance of Pt/Al-SBA-15 catalysts in hydroisomerization of n-dodecane

A series of Al-SBA-15 materials with different Si/Al ratios have been prepared via a post-alumination procedure. The results show that Al species can be introduced into the SBA-15 framework. Only the medium acid sites can be observed on the Al-SBA-15 samples, and the number of acid sites decreases with the increase of the Si/Al ratio. The hydroisomerization activities of n-dodecane over 1% Pt/Al-SBA-15-n catalysts increase with the number of acid sites, and the largest isomers yield reaches to 51%. It suggests that the Al-SBA-15 material is a suitable acid component for bifunctional catalysts for hydroisomerization of long chain n-paraffins.

Hierarchical porous structures by using zeolite nanocrystals as building blocks

Hierarchical porous structures have been fabricated using colloidal zeolite silicalite nanocrystals as building blocks. Continuous, uniform, optically transparent and self-standing silicalite membranes with well-defined shapes and controlled mesoporosity were obtained by self-assembly of zeolite nanocrystals followed by high-pressure compression and controlled secondary crystal growth via microwave treatment. The thickness of the compact self-standing membranes is tunable from 20 μm to several millimeters by simply using different surface weight densities. Controlled secondary growth via microwave treatment leads to a stronger self-standing membrane with controlled mesoporosity and has little effect on its thickness, crystallinity, micropore surface area and micropore volume.

Highly ordered mesoporous silica structures templated by poly(butylene oxide) segment di- and tri-block copolymers

Highly ordered mesoporous silica structures including body-centered cubic (Im (3) over barm), two-dimensional hexagonal (p6mm) and lamellar (L-chi) symmetries have been synthesized by using hydrophobic poly(butylene oxide) moiety diblock and triblock copolymers as structure-directing agents. Under acidic condition, highly ordered, caged cubic mesoporous silica structures (FDU-1, Im (3) over barm) with a large cell parameter (a = 220 Angstrom) can be formed in the presence of triblock poly(ethylene oxide)-poly(butylene oxide)-poly(ethylene oxide) (PEO-PBO-PEO) copolymer such as EO39BO47EO39. Calcined FDU-1 has a largest pore size of 120 Angstrom among all known cubic silica mesostructures, a pore volume of 0.77 cm(3)/g, and a BET surface area of 740 m(2)/g. Diblock poly(butylene oxide)-poly (ethylene oxide) (PBO-PEO) copolymer such as BO10EO16 favors to yield highly ordered two-dimensional hexagonal (p6mm) silica mesostructures with a well-uniformed pore size of 60 Angstrom and a large BET surface area of 902 m(2)/g. Lamellar (L-chi) mesostructures can also be obtained when high concentration diblock copolymer is used as the structure-directing agent. The calcined cubic mesostructured silica FDU-1 is hydrothermally stable in boiling water for at least nine days

Salt effect in the synthesis of mesoporous silica templated by non-ionic block copolymers

The use of inorganic salts during the synthesis of mesoporous materials with block copolymers can dramatically widen the syntheses domain (in temperature, surfactant concentration, etc.) and broaden the range of surfactants that can be utilized to produce highly ordered mesostructures.

Doped mesoporous silica fibers: the internal structure

The optical properties of mesoporous silica fibers grown in an acid synthesis have been analyzed by birefringence measurements. Comparison with the theoretical models for the internal structure of these fibers allows the conclusion that the hexagonally ordered pores are running in a circular direction around the fiber axis.

Directed growth of multiwalled carbon nanotubes from ordered porous silica structures

Ordered meso- and macroporous silica films can direct the growth of multiwalled carbon nanotubes from perpendicular to parallel to the substrate surface through control of the distribution of catalysts.