Dry reforming of methane over Co–Mo/Al2O3 catalyst under low microwave power irradiation

In this work, microwave (MW) irradiation was used to activate Co/Al2O3, Mo/Al2O3, and Co-Mo/Al2O3 catalysts for dry reforming of methane (DRM) reactions. Experimental results indicate that single metallic catalysts of either Co or Mo are inactive for DRM under all the tested conditions due to their limited MW-absorbing ability. In contrast, Co-Mo bimetallic catalysts supported by Al2O3 exhibit high catalytic activity due to the formation of a magnetodielectric Co0.82Mo0.18 alloy, which plays the dual role of a good MW acceptor and the provider of active centers for the DRM reaction. The MW power level required to activate such bimetallic catalysts for DRM is significantly dependent on the molar ratio between Co and Mo. The CoMo2 catalyst (with a molar ratio of 2.0 Co to 1.0 Mo) supported on Al2O3 exhibits the best catalytic performance, converting 80% CH4 and 93% CO2 to syngas at a ratio of H2/CO of 0.80 at the total volumetric hourly space velocity (VHSV) of 10 L g-1 h-1 and MW power of 200 W. As compared to the reported C-based catalysts, the Co-Mo/Al2O3 catalyst delivers more favorable stability over 16 time-on-stream (TOS) by virtue of its intrinsic ability to absorb MW without the inclusion of auxiliary MW acceptors

Foraging behavior of Melipona rufiventris Lepeletier (Apinae; Meliponini) in Ubatuba, SP, Brazil

This study describes how the foraging activity of Melipona rufiventris is influenced by the environment and/or by the state of a colony. Two colonies were studied in Ubatuba, SP (44° 48’ W and 23° 22’ S) from July/2000 to June/2001. These colonies were classified as strong (Colony 1) and intermediate (Colony 2) according to their general conditions: population and brood comb size and number of food pots. The bees were active from dawn to dusk. The number of pollen loads presented a positive correlation with relative humidity (r s = 0.401; p <0.01) and was highest between 70 and 90%. However, it was negatively correlated with temperature (r s = -0.228; p <0.01) showing a peak between 18 and 23 °C. The number of nectar loads presented a positive correlation with temperature (r s = 0.244; p <0.01) and light intensity (r s = 0.414; p <0.01); it was greater between 50 and 90% of relative humidity and 20 and 30 °C of temperature. They collected more nectar than pollen throughout the day, and were more active between 6 and 9 hours. Workers from Colony 1 (strong) collected nectar in greater amounts and earlier than those from Colony 2 (intermediate). The number of pollen, nectar and resin loads varied considerably between the study days. Peaks of pollen collection occurred earlier in months with longer days and in a hotter and more humid climate. The foraging behavior of M. rufiventris is probably affected by the state of the colony and by environmental conditions, notably temperature, relative humidity, light intensity and length of the day