Synthesis and Shape-Selective Catalytic Application of Ordered Cubic Ia3̅d Supermicroporous Materials Templated by Rosin-Derived Quaternary Ammonium Salt with a Hydroxyl Radical in the Headgroup

We described the comprehensive synthesis, characterization, and catalytic performance of a novel type of the ordered cubic Ia3̅d supermicroporous silicas by using tetraethyl orthosilicate as a silicon source and a hydroxyl-functionalized quaternary ammonium salt as a template under alkali conditions. The effects of various reaction conditions on the pore structure and morphology of the silica materials were thoroughly investigated. Our results showed that under a wide range of reaction conditions, supermicroporous silicas with a highly ordered cubic Ia3̅d structure can be produced with a large BET specific surface area of 1741 m²/g, high pore volume of 0.91 cm³/g, concentrated pore size at 19.1 Å, and crystalline morphology. After Al doping, the obtained aluminosilicates preserved a highly ordered cubic supermicroporous structure. By using the H-form aluminosilicates as catalysts, we selectively dimerized β-pinene. The catalysts exhibited an excellent catalytic activity for β-pinene dimerization with a conversion yield up to 100%. Compared with conventional mesoporous H-form Al-MCM-48 catalysts, the prepared supermicroporous catalysts exhibited superior catalytic performance due to their excellent shape-selective properties, producing the β-pinene dimer in a yield up to 72.4% with dimer/oligomer ratios in the range of 7.5-10.1. This study featured a detailed preparation and characterization of supermicroporous silica with novel microstructures and showed its utility in catalytic dimerization.

Synthesis of ordered lamellar supermicroporous silica with rigid neutral and long-chain cationic composite templating route

Using a mixture of neutral primary amine dehydroabietylamine (DHAA) and long-chain cetyltrimethyl ammonium bromide (CTAB) as the template, ordered lamellar supermicroporous silicas were synthesized with NaOH as the base source and tetraethylorthosilicate (TEOS) as the silica source. The concentrations of DHAA, CTAB, and NaOH in the synthesis system had great effects on the structural properties of the samples. When the molar ratio of components was nTEOS:nCTAB:nDHAA:nNaOH:nH₂O = 1:0.114:0.00457:0.5:60, the material showed a lamellar phase with the highest ordering degree. By adding only a trace amount of DHAA into the synthesis system, the structure of the samples could be transformed from cubic phase to lamellar phase, since the added DHAA solubilized in CTAB micelles to change the effective surfactant ion pair packing parameter. The dosage of CTAB should be moderate; too high or too low will decay the ordering degree of the lamellar structure.A much higher concentration of NaOH resulted in an ethanol-rich solvent in which the DHAA did not solubilize in the micelles of CTAB, but adsorbed at the hydrophilic headgroup–solvent interface. Accordingly, a structural transformation from lamellar phase to hexagonal phase occurred.

Bifunctional Cage-Type Cubic Mesoporous Silica SBA-1 Nanoparticles for Selective Adsorption of Dyes

Bifunctional SBA-1 mesoporous silica nanoparticles (MSNs) with carboxylic acid and amino groups (denoted as CNS-10-10) have been successfully synthesized, characterized, and employed as adsorbents for dye removal. Adsorbent CNS-10-10 shows high affinity towards cationic and anionic dyes in a wide pH range, and exhibits selective dye removal of a two-dye mixture system of cationic methylene blue and anionic eosin Y. By changing the pH of the medium, the selectivity of the adsorption behavior can be easily modulated. For comparison purposes, the counterparts, that is, pure silica SBA-1 MSNs (CS-0) and those with either carboxylic acid or amino functional groups (denoted as CS-10 and NS-10, respectively) were also prepared to evaluate their dye-adsorption behaviors. As revealed by the zeta-potential measurements, the electrostatic interaction between the adsorbent surface and the dye molecule plays an important role in the adsorption mechanism. Adsorbent CNS-10-10 can be easily regenerated and reused, and maintains its adsorption efficiency up to 80 % after four cycles.

Preparation of hierarchically structured Y zeolite with low Si/Al ratio and its applications in acetalization reactions

Hierarchically structured Y zeolites were prepared by a post-synthetic strategy, where the as-made NaY zeolite was sequentially treated by a lactic acid solution and an alkaline solution containing cetyltrimethyl ammonium bromide (CTAB).