No abstract

Dehydrogenation of methanol on copper catalysts supported on SiO, and modified by Cr,03 was studied in the temperature range of 200 to 270°C. The chief product of reaction was methyl formate together with carbon monoxide and traces of formaldehyde.It was found that very high and sustained activity could be achieved by the method adopted for preparation of the catalysts. The unused catalyst was completely amorphous, but in catalyst samples used for Eng periods of time the presence of crystallites in the size runge 50 to 65 A was observed.Nearly 80 % of theoretically obtainable conversion of methanol to methyl formate was achieved in laboratory scale tubular reactor. A catalyst containing Cu: Cr,03:Si0, = 54:5.90: 7.0 prepared by the method described proved to be very active at low temperatures, giving 41 % conversion to methyl formate at 230°C for long periods of use. N o interaction between the active component and the support was noticeable.Addition of chromia improved the catalyst texture and stability. When nickel was present in quantities less than 1.25 %, it acted as a promoter and gave improved performance.

No abstract

Polycrystalline Bi36Fe2O57 (BFO) ceramic was prepared by an economical chemical route. The X-ray powder diffraction analysis shows the formation of single-phase BFO ceramic. Nanosized formation of BFO ceramic particles was characterized by XRD as well as TEM and had particle size 76 ± 10 nm range. The sillenite type Bi36Fe2O57 shows better photocatalytic activity for the methylene blue (MB) dye degradation under visible light exposure than the perovskite-based BiFeO3 due to the low band gap(1.8eV) of the former. The photocatalytic mechanism of MB degradation over Bi36Fe2O57 ceramic can be explained by the Langmuir-Hinshelwood model which reflects the adsorption-controlled photocatalytic process.

In this manuscript, We have reported the synthesis and characterization of Mg-doped and undoped BCTO ceramic (Bi2/3Cu3-xMgxTi4O12, x=0,0.05,0.1,0.2) sintered at 1173 K for 8 h, which have been prepared by the semi-wet path. Single-phase formation of ceramic was approved by the XRD pattern. The Microstructural properties were studied by TEM and AFM. The samples were characterized by dielectric and impedance spectroscopic properties. The dielectric constant (εr) was calculated to be 3024 for BCTO ceramics at 423 K and 100 Hz. The tangent loss (tan δ) value was calculated to be 0.45 for BCTO ceramic at 423 K and 10 kHz. The internal Barrier Layer Capacitance (IBLC) mechanism was responsible for the high value of dielectric constant. XPS spectroscopy confirmed the oxidation state of the ceramic. It was observed from Impedance and modulus studies that there was the existence of the Maxwell-Wagner form of relaxation in the ceramics.