Effect of Industrial Alumina Powder Particle Size on Preparation of Active α-Al2O3 Micropowder

To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al2O3 micropowder),the fine powders with...     

Design and Test of 2.5 μ m Cutoff Size Inlet Based on a Particle Cup Impactor Configuration

Based on the particle cup impactor configuration, an inlet for sampling fine particles smaller than 2.5 w m in diameter was designed for operation at a flow rate of 25 l/min. To determine the optimal dimensions of the particle cup impactor applicable to the PM 2.5 inlet, calibration experiments were carried out at wind velocities of 2 and 24 km/h in a wind tunnel. It was noted that the particle cup impactor having an impaction nozzle diameter of 3.2 mm and the nozzle-to-cup spacing of 3.6 mm yielded a sharp size cutoff. Supplementary experiments were conducted on sampling performance with the inlet having the optimally selected configuration at a near-zero wind speed in the test chamber. Results of the tests showed the inlet had a cutoff size of 2.43 w m in aerodynamic diameter, at 25 l/min, and that particles larger than 2.5 w m were trapped in the cup. Additional experiments covering a flow rate between 10 and 40 l/min with particle sizes between 0.8 and 4.3 w m were conducted in the test chamber. A field test was performed to examine the PM 2.5 inlet in real situations. The performance indicated that the inlet design met the basic requirements of fine-particle sampling.     

Catalytic Combustion of Methyl Tert-Butyl Ether on Rh/??-Al2O3 and Rh/??-Al2O3?CCeO2 Catalysts: Effects of Thermal Treatments, Cerium Oxide and Particle Size

The effects of activation pretreatments, Rh particle size and content of cerium oxide on Rh/??-Al₂O₃ catalysts for the oxidation of methyl tert-butyl ether (MTBE) were investigated. Three different conditions were used for the activation of the catalysts: (1) with air flow, (2) using a mixture of air and MTBE, and (3) by hydrogen reduction followed by oxidation with air. On Rh/??-Al₂O₃ catalyst the thermal pretreatments are of great importance for the MTBE oxidation. However, on Rh/??-Al₂O₃?CCe1 catalyst, the total combustion of MTBE was reached at a temperature of 200???C lower than that obtained with the Rh/??-Al₂O₃ catalyst at whatever thermal treatment applied. A Rho/Rh^??+ and Ce³⁺/Ce⁴⁺ species were identified by XPS suggesting that they are the responsible of the high activity showed by the Rh/??-Al₂O₃?CCe1 catalyst. A particle size effect for MTBE oxidation was observed on Rh/??-Al₂O₃ catalysts, large Rh particles are more active than the small ones.