Biodiesel production from waste cooking oil over sulfonated catalysts

Biodiesel production from waste cooking oil with methanol was carried out in the presence of poly(vinyl alcohol) with sulfonic acid groups (PVA-SO3H) and polystyrene with sulfonic acid groups (PS-SO3H), at 60°C. The PVA-SO3H catalyst showed higher catalytic activity than the PS-SO3H one. In order to optimize the reaction conditions, different parameters were studied. An increase of waste cooking oil conversion into fatty acid methyl esters with the amount of PVA-SO3H was observed. When the transesterification and esterification of WCO was carried out with ethanol over PVA-SO3H, at 60°C, a decrease of biodiesel production was also observed. The WCO conversion into fatty acid ethyl ester increased when the temperature was increased from 60 to 80°C. When different amounts of free fatty acids were added to the reaction mixture, a slight increase on the conversion was observed. The PVASO3H catalyst was reused and recycled with negligible loss in the activity.

Composites Chitosan/SBA-15 with sulfonic acid as heterogeneous catalysts for biodiesel production

Free fatty acids (palmitic, stearic and oleic acid) were converted into biodiesel with methanol over composites catalysts consisting in SBA-15 with sulfonic acid groups (SBA-15-SO3H) immobilized in Chitosan (CH), at 60ºC. It was observed that the catalytic activity increased with the amount of SBA-15-SO3H dispersed in CH. It was also observed that the catalytic activity decreased in the series: palmitic acid > stearic acid > oleic. The catalytic stability of [SBA-15-SO3H]3/CH composites was studied. A good stability was observed.

Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

our distinct nocturnal surface ozone (NSO) enhancement events were observed, with NSO concentration exceeding 80μg/m3, at multiple ozone (O3) monitoring stations (32 sites) in January, November and December between year 2000–2010, in Portugal. The reasonable explanation for the observed bimodal pattern of surface ozone with enhanced NSO concentration during nighttime has to be transport processes, as the surface ozone production ceases at nighttime. Simultaneous measurements of O3 at multiple stations during the study period in Portugal suggest that horizontal advection alone cannot explain the observed NSO enhancement. Thus, detailed analysis of the atmospheric conditions, simulated with the Weather Research and Forecasting (WRF) model, were performed to evaluate the atmospheric mechanisms responsible for NSO enhancement in the region. Simulations revealed that each event occurred as a result of one or the combination of different atmospheric processes such as, passage of a cold front followed by a subsidence zone; passage of a moving surface trough, with associated strong horizontal wind speed and vertical shear; combination of vertical and horizontal transport at the synoptic scale; formation of a low level jet with associated vertical mixing below the jet stream. The study confirmed that large-scale flow pattern resulting in enhanced vertical mixing in the nocturnal boundary layer, plays a key role in the NSO enhancement events, which frequently occur over Portugal during winter months.