Investigation of spatially patterned catalytic reactors
The theme of this work is to enhance the performance of a primary reaction system by introducing dual-functionality into a packed-bed reactor via a spatial pattern. This paper focuses on a generic system in which the primary reaction is equilibrium-limited and an auxiliary reaction is incorporated to act as a drain-off mechanism alleviating the equilibrium constraint. It is found that patterns in which the two catalysts are spatially layered (and maintained at different temperatures) or well-mixed (and operated at a common temperature) can both offer significant improvements over an unpatterned reactor. Operating the well-mixed pattern at high temperature is generally superior to switching between high- and low-temperature layers in the segmented configuration. The exception to this rule occurs when the mixed bed is punished for being hot as either the equilibrium ceiling on the primary reaction drops sharply or a competitive reaction dominates at high temperature. The extent to which the layered pattern’s improvements are compromised by axial heat dispersion between zones is examined in terms of a backflow mixing cell model.
Coupling of steam and dry reforming of methane in catalytic fluidized bed membrane reactors
A rigorous mathematical model is used for the simulation of steam and CO2 reforming in fluidized bed membrane reactors. A well-mixed catalyst pattern is implemented to couple the reactions. It has been shown that the combined effect of the membrane and reaction coupling provides exciting opportunities to overcome the equilibrium conversion limits and to achieve complete conversion of methane. The results indicate that the complete conversion of methane at low temperature is possible. Optimal conditions are observed to exist and an effective reactor length criterion is used to evaluate the reactor performance. The influence of some key parameters on the optimal conditions and the reactor such as temperature, pressure, steam to carbon ratio and membrane thickness have been investigated.
Assessment of some agro-technological parameters of cactus pear fruit ( Opuntia ficus-indica Mill . ) in Morocco cultivars
Cactaceae had always attracted attention by their strange shapes and important adaptability supporting extreme conditions. For this reasons, Fruit traits were measured on 13 cultivars growing in different locations in Morocco. Results show significant differences between the cultivars. The source of this variation was probably genetic without excluding the geographic effects. The Tamri, Berkan, Ait Baha cultivars showed small fruit dimensions and weight. In contrast, Sidi-Ifni M, Nador, Mohammedia and Ben Guerir were greater than 100 g by fruit. Sidi-Ifni M, Hoceima, Mohammedia and Nador, although larger, contained few seeds, about 200 seeds per fruit; while Tamri, Ait Baha, Safi, Meknes and Tafraout contained over than 230 seeds per fruit. High levels of juice about 62 ml/100 g pulp were obtained with Sidi-Ifni M, Nador, Mohammedia and Ben Guerir cultivars. Total sugars of the 13 cultivars were quite similar and pH was low in Tamri and close to neutrality in the rest of cultivars. Therefore, oil extracted from Opuntia ficus-indica seeds constituted 13.6% of the whole seed. Thin-layer chromatography in conjunction with gas-liquid chromatography-mass spectrometry revealed a relatively high degree of unsaturation, 83.32% and 16% for saturated fatty acid, with a linoleic acid content of 63.66% followed by oleic 18.34%, palmitic 12.84% and stearic acid 2.81%. Based on these results, O. ficus-indica seed oil appears to be a good potential source of edible oil for human and (or) animal consumption. Our investigation describes that Tamri and Tafraout cultivars are not really a commercial viable fruit due to low total soluble solids value and highest seeds number per fruit. Against Mohammedia, Sidi Ifni M and Nador cultivars proved to have the highest fruit weight, very good total soluble solids value and low number of seeds, these cultivars can therefore be planted for both fruit production and for harvesting of cladodes for animal feed.