Novel catalysis of TiO2 for the catalytic alcohols synthesis from CO and H2O

Direct synthesis of alcohols from CO and H2O was investigated using TiO2 catalyst. MeOH (about 24 mg g(-1) h(-1)) and EtOH (about 8 mg g(-1) h(-1)) could be produced under the reaction conditions of T= 573 K, P= 0.5 MPa, CO flow rate of 30 ml min(-1) and CO/H2O = 3/2 during the period of 12 to 44 h time-on-stream. Compared with PbO, TiO2 could preserve stable catalytic activity during a long time of reaction. For the same catalyst TiO2, the reaction performance of alkali carbonates increased with their solubility (K2CO3>Na2CO3>Li2CO3). The corresponding catalytic activity was found to increase with the alkalescence of solvent. The formation mechanism of alcohols was proposed as well. (C) 2004 Elsevier B.V. All rights reserved.

Catalytic alcohols synthesis from CO and H2O on TiO2 catalysts calcined at various temperatures

The reaction performance for CO hydration on a TiO2 catalyst under different calcination temperatures was investigated. Under reaction conditions of T = 573 K, P = 0.5 MPa, CO flow rate of 30 ml min(-1), TOS = 12 h, and CO/H2O (g) = 3/2 (mol), the TiO2 catalyst with a futile content of 18% shows a maximum alcohols STY of 1.81 Mg m(-2) h(-1). In addition, the catalyst deactivation and regeneration were discussed.

Cyclopropanation on a highly active heterogeneous catalyst: CuO/TiO2-Al2O3

Some heterogeneous catalysts, cupric oxide supported on different supports, were prepared and employed to catalyze the cyclopropanation of styrene and 2,5-dimethyl-2,4-hexadiene with ethyl diazoacetate (EDA). The catalytic performance for cyclopropanation strongly depends on the nature of the support. A novel catalyst, CUO/TiO2-Al2O3, in which Al2O3 is modified with a monolayer TiO2, is found to be most active and selective for the cyclopropanation reaction. The yields of 93 and 94% cyclopropanes are obtained for styrene and 2,5-dimethyl-2,4-hexadiene at 40 degreesC as the substrates, respectively. The activity and selectivity in cyclopropanes are optimized with a monolayer dispersion of cupric oxide on the corresponding supports. (C) 2002 Elsevier Science B.V. All rights reserved.

The enhancement of TiO2 photocatalytic activity by hydrogen thermal treatment

In this study, conventional TiO2 powder was heated in hydrogen (H-2) gas at a high temperature as pretreatment. The photoactivity of the treated TiO2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H-2-treated TiO2 catalysts and an optimum temperature for the H-2 treatment was found to be of 500-600 degreesC. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti3+) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti3+ in the lattice of the H2-treated TiO2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti3+ in the H-2-treated TiO2 samples after 10 months storage was still significant higher than that in the untreated TiO2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H-2-treated TiO2. (C) 2002 Elsevier Science Ltd. All rights reserved.

An alternative approach to ascertain the rate-determining steps of TiO2 photoelectrocatalytic reaction by electrochemical impedance spectroscopy

In an attempt to ascertain the rate-determining steps (RDS) of TiO2 photoelectrocatalytic (PEC) reaction, the PEC oxidation of sulfosalicylic acid (SSA) solution in a TiO2-coated electrode reactor system was monitored by applying the electrochemical impedance spectroscopy (EIS) method. In the meantime, an EIS mathematical model was first established to theoretically simulate the PEC reaction. Based on the EIS model, the theoretical simulation indicates three typical reactions in a PEC oxidation process, which include the charge-transfer-dominated reaction, both the charge-transfer- and adsorption-dominated reaction, and the adsorption-dominated reaction. The experimental results of EIS measurement showed that there was only one arc/semicircle on the EIS plane display when the external bias applied was below 200 mV (vs SCE) in the SSA PEC degradation whereas there were two arcs/semicircles when the externally applied bias exceeded 200 mV (vs SCE). The experimental results have a good agreement with the model simulation. The EIS method in this study provides an easier way to determine the RDS in a PEC oxidation process, which would be helpful to better control the reaction in practice.

Novel activity of TiO2 for catalytic conversion of CO and H2O to alcohols in the presence of K2CO3

In the presence of K2CO3, TiO2 shows good catalytic activity and stability for the alcohols synthesis from CO and H2O. CO conversion of 7.6% and the STY of MeOH (about 24 mg g(-1) h(-1)) and EtOH (about 8 mg g(-1) h(-1)) are obtained under reaction conditions of T = 573 K, P = 0.5 MPa, CO flow rate of 30 ml min(-1) and CO/H2O = 3/2 during the period of 12 h to 44 h time-on-stream.

Enhance the optical absorptivity of nanocrystalline TiO2 film with high molar extinction coefficient ruthenium sensitizers for high performance dye-sensitized solar cells

We report two new heteroleptic polypyridyl ruthenium complexes, coded C101 and C102, with high molar extinction coefficients by extending the pi-conjugation of spectator ligands, with a motivation to enhance the optical absorptivity of mesoporous titania film and charge collection yield in a dye-sensitized solar cell. On the basis of this C101 sensitizer, several DSC benchmarks measured under the air mass 1.5 global sunlight have been reached.

Excellent antimicrobial properties of mesoporous anatase TiO2 and Ag/TiO2 composite films

Optically transparent, crack-free, mesoporous anatase TiO2 thin films were fabricated. The Ag/TiO2 composite films were prepared by incorporating Ag in the pores of TiO2 films with an impregnation method via photoreduction. The as-prepared composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectronic spectra (XPS) and N-2 adsorption. The release behavior of silver ions in the mesoporous composite film was also studied. Moreover, the antimicrobial behaviors of the mesoporous film were also investigated by confocal laser scanning microscopy.

Synthesis of Titania in Ethanol/Acetic Acid Mixture Solvents: Phase and Morphology Variations

The phase and morphology variations of titania prepared in ethanol/acetic acid mixture solvents have been systematically investigated. X-ray diffraction results and microscopy observations reveal that pure anatase aggregates consisted of small nanoparticles, pure rutile microspheres comprised of nanofibers, and their mixtures could be obtained by varying ratios of ethanol to acetic acid under solvothermal conditions. The contents of anatase and rutile in the mixed phases also vary with the ratios of ethanol to acetic acid. Field emission scanning electron microscopy and high resolution transmission electron microscopy results show that the two phases are separated from each other in final products and form aggregates with morphologies resembling to their pure phase products obtained under favorable conditions. The as-produced rutile nanofibers, either in pure phase or in mixed phases, tend to grow into hollow microspheres.