Jianhua Zhu

The direct synthesis of mesoporous structured MnO2/TiO2 nanocomposite : a novel visible-light active photocatalyst with large pore size

A series of visible-light-driven mesoporous structured MnO(2)/TiO(2) nanocrystal photocatalysts have been synthesized through a modified sol-gel method, and the N(2) adsorption-desorption isotherm confirms that the mesoporous materials possess large pore size (up to 9.2xa0nm) and a narrow pore size distribution. X-ray powder diffraction (XRD) analyses and complementary x-ray photoelectron spectroscopy (XPS) measurements reveal that the doping of the transition metal Mn inhibits the growth of TiO(2) anatase nanocrystals and the Mn species are highly dispersed on the surface of TiO(2). The ultraviolet (UV)-vis spectrum demonstrates the excellent adsorption properties of MnO(2)/TiO(2) over the whole region of visible light, which enables this novel photocatalysis material to possess remarkable activity in the photocatalytic degradation of methylene blue under visible light radiation. Moreover, a coating mechanism based on the nucleation of titania nanocrystals along with the interaction between the dopant precursors and titania clusters has been suggested.

Attempts to create new shape-selective solid strong base catalysts

Abstract Loading of KF on zeolite NaY leads to a similar basicity to that of KOH/NaY, but no strongly basic sites formed on the composite due to the negative effect of SiO 4 tetrahedra in NaY which form species with low base strength. Using AlPO 4 -5 or NaY coated with Al 2 O 3 to support KF could avoid the effect of SiO 4 tetrahedra and increased the base strength of the sample. KNO 3 loaded on NaY created basic sites after decomposition at 673xa0K with a redox method, and KNO 3 /KL was found to have superbasicity. For preparation of strongly basic zeolites, microwave irradiation was employed to disperse MgO on zeolites, and the resulting materials showed high activities in the decomposition of isopropanol or the isomerization of cis -but-2-ene at 273xa0K.

Catalytic Performance of Supported KNO3 Solid Bases for Methylation of Cyclopentadiene

The catalytic performance of a series of supported KNO3 solid bases for the synthesis of methylcyclopentadiene via cyclopentadiene methylation with methanol was investigated. X-ray diffraction and N2 adsorption were applied to study the characteristics of different supports and the decomposition of KNO3 on them. The base strength of the samples was measured using a Hammett indicator. A significant difference in base strength of different oxides-supported KNO3 was observed. A base strength (H−) of 27.0 was detected in KNO3 supported on ZrO2, γ-Al2O3, hydrotalcite (HT), and MgO, which showed the characteristics of the solid superbases, whereas a base strength (H−) of only 9.3 was examined in SiO2- and TiO2-supported KNO3. Such a difference in the base strength can be ascribed to the differences in the surface nature of the supports. A suitable basicity is necessary for catalyzing the methylation of cyclopentadiene with methanol because only small amounts of cyclopentadiene molecules were converted over catalysts with low basicities, such as KNO3/SiO2 and KNO3/TiO2 as well as most oxide supports. However, the acidity and the surface area of the catalysts also have certain effects on the reaction. The conversion of cyclopentadiene and the selectivity for methylcyclopentadienes were around 32% and 86% over KNO3/γ-Al2O3 and KNO3/HT, respectively, at 450°C, which is higher than that on MgO.

Strong selective adsorption ofN-nitrosamines on zeolites

With the functional group of -N-N=O, N-ni-trosamines are well known to constitute a serious health risk[1]. These toxicant chemicals not only give rise to poisoning sometimes[2], but also play an important role in causing cancer in almost all organs of experimental animals and are therefore likely to be related to human beings, since they have the similar metabolism and meta-balin to those animals[3]. Gaseous nitrogen oxides like NO2, N2O3 and N2O4 are reportedly to react with-secondary amines and form N-nitrosamines in environment[4], and some foods, such as beer and salted fish, contain a high concentration of N-nitrosamines and their precursors. However, tobacco and cigarette smoke are believed to be the largest N-nitrosamines pollution for human beings besides the industrial working place. N-nitrosamines are considered important contributors to the total burden of carcinogens resulting from tobacco, especially tobacco smoke, because they can be deposited directly into the blood following inhalation t

Preparing strong basic zeolite molecular sieve catalytic materials

Progress on preparing strong basic and superbasic zeolites, mainly obtained in China during last decade has been reviewed. Strong basic sites are difficult to be generated on zeolite by common way, e.g. adjusting the chemical composition of frameworks or loading alkali metal oxides/hydroxides owing to the special structure of zeolite. Through some novel methods such as modification with neutral salt of potassium or dispersion of MgO combined microwave irradiation, however, strong basic zeolites can be obtained, and the relationship between formation of superbasic sites and structure of support is discussed. Finally the research on strong basic zeolites is prospected.

Preparation of Mesostructured Lamellar Zirconia

Mesostructured lamellar zirconia was synthesized in the hydrothermal systems using Cetyltrimethyl Ammonium Bromide (CTAB) as a template and zirconyl chloride as zirconium precursor. The as-prepared composites were characterized by X-ray diffraction (XRD), TG-DTA, and DR-UV techniques. The influences of hydrothermal aging time, total concentration of solution, different mole ratio of zirconyl chloride/surfactant, and post treatment on the structure of mesostructured lamellar zirconia were discussed in this article.

Microwave radiation: A novel way to prepare new Al2O3-Nay shape-selective catalytic materials

Owing to the existence of silicon component in zeolite framework, it is difficult to generate strong basicity on zeolite in the case of loading alkali metal......

Modification of Structure of Pore Wall of Mesoporous Aluminosilicate to Increase Its Adsorptive Capability for Nitrosamine

A method to control the structure of the silica wall of mesoporous silica materials was proposed for trapping trace amounts of small pollutant molecules. The mesoporous silica materials containing pore wall defect voids were synthesized by controlling the pH of the synthesis system and the concentration of the organic surfactant and adding an inorganic salt to control the assembling rate of silica species on the surfactant micelle or change the form of the surfactant-aluminosilicate liquid crystal. X-ray diffraction, N2 adsorption-desorption, 29Si MAS nuclear magnetic resonance, and transmission electron microscopy were used to characterize the pore structure of the samples. Volatile nitrosamine N-nitrosopyrrolidine (NPYR) was selected as the probe to assess the adsorptive capacity of the composites. The introduction of aluminum species and the creation of structural defects in the mesoporous silica wall greatly improved the adsorption of NPYR. The material is useful for environmental protection.