X. Duan

A new support for the immobilization of penicillin acylase

Mesoporous MCM-41 having well ordered long-range structure, large pore diameters, narrow pore-size distribution, high pore volume and specific surface area has been synthesized. The surface of MCM-41 has an abundance of weakly acidic hydroxyl groups. Assay results show that MCM-41 is a more effective support for the immobilization of Penicillin Acylase (PA) than many of other supports due to its structural and surface characteristics. PA can be immobilized on MCM-41 through either direct immobilization or covalent coupling. The former gives higher activity of IME than the later. In the direct immobilization, PA molecules are immobilized on MCM-41 through the hydrogen-bonded interaction between hydroxyl groups of MCM-41 and carbonyl or amino groups in the PA molecule.

New methods to remove organic templates from porous materials

New methods to remove the templates from porous materials with high porosity and poor structural stability have been proposed in the light of analysis of the decomposition process of the organic templates. Microwave irradiation and two-step calcination are shown to be more favorable than conventional calcination in that the new methods have beneficial effects on both the structural order and surface acidity. Two-step calcination is particularly effective because it is more convenient and reproducible than microwave irradiation.

Some factors affecting the immobilization of penicillin G acylase on calcined layered double hydroxides

Abstract A new type of support, calcined layered double hydroxides (CLDH), has been used to immobilize penicillin G acylase. The effect of varying the composition of the layered double hydroxide precursor and the calcination temperature on the activity of the immobilized enzyme has been studied. The activity of the immobilized enzyme decreased with increasing Mg/Al molar ratio of the CLDH. Mg/Al-CLDH had a higher affinity for the enzyme than Zn/Al-CLDH, but a lower percentage expressed activity. The activity of the immobilized enzyme was a maximum when the calcination temperature was between 450 and 550°C. The amount of enzyme adsorbed by the support shows a close correlation with its surface area. Immobilization of the enzyme on the support increases the acid resistance of the former.

Improving the stability of MCM-41 by monolayer dispersion of a metal oxide

ZrO2/MCM-41, with ZrO2 dispersed as a monolayer, showing clearly ordered long-range structure and pore structure has been prepared. The changes in XRD patterns with thermal or hydrothermal treatment indicates that after the monolayer dispersion of ZrO2, the thermal and hydrothermal stability of MCM-41 are significantly improved.

In Situ Formation of a Novel Nanocomposite Structure Based on MCM-41 and Polyethylene

M41S materials are prepared by in situ assembly of inorganic precursors and organic template and can be viewed as nanocomposites of the siliceous phase and organic surfactant. Calcination of these precursors gives the M41S materials that have been used to prepare novel nanocomposite structures, in which the organic phase inside the nano-sized pores is isolated by the nano-sized inorganic pore walls. The nanocomposite structures can be formed by in situ polymerization of monomers inside the channels. Polymerization of ethylene takes place inside the nano-sized pores, producing the desired nanocomposite structure. The resulting polyethylene was found to be a mixture of crystalline and amorphous phases.

Some Factors Influencing the Morphology of α-Zirconium Phosphate and its Intercalation Reactions with a Bifunctional Thioether Amine

Crystalline samples of α-zirconium phosphate, (α-ZrP, α-Zr(HPO4)2·H2O) have been prepared by decomposition of zirconium fluoride complexes in the presence of phosphoric acid under a variety of conditions. The crystallinity and morphology have been shown to depend on a number of factors including the F−/Zr4+ ratio, the concentration of Zr4+ ions, the material of the reaction vessel and the reaction temperature. Under conditions of rapid precipitation small plate-like crystals of α-ZrP are produced whereas under conditions of slow crystallisation larger crystals with a lower aspect ratio are formed. The relative intensities of the d002, d110 and d112 reflections observed by X-ray powder diffraction show a correlation with the crystal morphology as determined by SEM.The intercalation reaction of 4-(methylmercapto)aniline with different samples of α-ZrP under a variety of conditions has been studied. Incomplete intercalation is observed in each case, with the extent of intercalation depending on both the morphology of the α-ZrP and the reaction conditions. The intercalated amine has been shown to exist as a mixture of protonated cations and neutral molecules.