Increasing carbon utilization in Fischer-Tropsch synthesis using H2-deficient or CO2-rich syngas feeds

Fischer-Tropsch technology has become a topical issue in the energy industry in recent times. The synthesis of linear hydrocarbon that has high cetane number diesel fuel through the Fischer-Tropsch reaction requires syngas with high H₂/CO ratio. Nevertheless, the production of syngas from biomass and coal, which have low H₂/CO ratios or are CO₂ rich may be desirable for environmental and socio-political reasons. Efficient carbon utilization in such H₂-deficient and CO₂-rich syngas feeds has not been given the required attention. It is desirable to improve carbon utilization using such syngas feeds in the Fischer-Tropsch synthesis not only for process economy but also for sustainable development. Previous catalyst and process development efforts were directed toward maximising C₅₊ selectivity; they are not for achieving high carbon utilization with H₂-deficient and CO₂-rich syngas feeds. However, current trends in FTS catalyst design hold the potential of achieving high carbon utilization with wide option of selectivities. Highlights of the current trends in FTS catalyst design are presented and their prospect for achieving high carbon utilization in FTS using H₂-deficient and CO₂-rich syngas feeds is discussed.     

Effect of Processing Under Ultraviolet Light on the Shelf Life of Fresh-Cut Cantaloupe Melon

ABSTRACT: The effect of processing cantaloupe melon under ultraviolet-C (UV-C) radiation on storage properties of the cut fruit at 10 °C was compared with post-cut UV-C fruit treatment and the untreated control. Cutting fruit under UV-C light induced a hypersensitive defense response that resulted in increased accumulation of ascorbate peroxidase relative to the other 2 treatments. Fruit processed under UV-C radiation had the lowest esterase activity throughout the storage period. Lipase activity was higher in post-cut treated fruit than fruit processed under UV-C light and the control fruit. Lipase activity, however, decreased rapidly in fruit processed under UV-C and was undetectable after 7 d of storage. Human sensory aroma evaluation indicates reduced rancidity, and instrumental texture measurements suggested improved firmness retention in fruit cut under UV-C radiation. The treatment also reduced respiration during cut fruit storage. UV-C was effective in reducing yeast, mold, and Pseudomonas spp populations in both treatments. Fresh-cut pieces from whole melon cut under UV light had lower populations of aerobic mesophilic and lactic acid bacteria relative to the control and post-cut treated pieces. Results indicate that while post-cut application of UV improved shelf life of cut cantaloupe melon, cutting fruit under UV-C radiation further improves product quality.     

Lactic fermented foods in Africa and their benefits

Lactic acid fermentation is an important food processing technology in Africa. This technology is indigenous and is adaptable to the culture of the people. This paper reviews the different raw materials and microorganisms which are used in producing lactic fermented food products in Africa. The beneficial aspects of this technology for improving food safety in Africa as a low-cost method of food preservation and in improving the nutritional quality of the food raw materials are discussed. Areas of research needs to enhance further the benefits of this technology are highlighted.     

Influence of process conditions on the sulfonation of methyl ester synthesized from used cooking oil: Optimization by Taguchi approach

Developing a robust and facile process route for fatty acid methyl ester sulfonate (MES) synthesis is of importance for industrial applications. Herein, Taguchi orthogonal array (OA) approach was used for the first time to establish the optimum process condition for the sulfonation of methyl esters (ME) with chlorosulfonic acid (CSA). According to the experimental design, the most significant parameter was sulfonation temperature, followed by CSA/ME molar ratio. Under the optimum sulfonation conditions (that is, 70°C sulfonation temperature, 2.0 h sulfonation time, 1.5:1 mol/mol CSA/ME molar ratio and 2.0 h aging time), the MES yield and the corresponding signal/noise ratio were 92.08 ± 0.28% and 39.28, respectively. The obtained FTIR and ¹H NMR data revealed spectra associated with methyl (CH₂ asymmetric and CH₂ symmetric stretching vibrations), esters (CO, C O, and O CH₃), and sulfonate (SO) groups in the MES sample synthesized under optimal conditions, thus confirming the target MES product. Surface tension measurements revealed that the optimal MES sample had a low critical miscelle concentration of 0.082 g/L at a surface tension of 51.2 mN/m, implying the possibility of better performance.     

Kinetics and neuro-fuzzy soft computing modelling of river turbid water coag-flocculation using mango (Mangifera indica) kernel coagulant

This study investigates kinetics and Adaptive Neuro-Fuzzy Modeling (ANFM) of river turbid water coagulation-flocculation (CF) process using mango kernel coagulant (MKC). CF experiments were performed using jar test apparatus and the process kinetic-transport parameters (coagulation rate constant, half-life time, and particle diffusivity) were determined using kinetic-transport models. Grid-partitioning neuro-fuzzy programming codes were written and implemented in Matlab 9.2 software environment for the development of neuro-fuzzy architecture. The ANFM input data include initial water pH, initial water turbidity, biocoagulant dosage, CF time, and turbidity removal percentage (TRP) as output data. Generalized bell membership function was optimally selected for fuzzification of input variables and a hybrid algorithm was considered for the learning method of input-output data with constant output membership type. The minimum turbidity (0.51 NTU) of treated water was achieved at pH 12 and coagulant dosage of 2.5?mg/L with coagulation rate constant, half-life (t_1/2) and particle diffusivity 0.0194?s^?1, 10.01?min, and 7.267?×?10^?14 m²/s, respectively. The correlation coefficient (R²) between the experimental and neuro-fuzzy predicted values was 0.9924 and the ratio (K) of training error to testing error was 0.68. Thus, this study shows that ANFM can be used as a reliable tool for modeling river water CF and kinetic-transport parameter results are useful in process design, optimization, and control.     

Genetic and Environmental Variation for Seed Yield,Protein, Lipid and Amino Acid Composition in Cowpea (Vigna unguiculata (L) Walp)

The genetic and environmental variability for seed yield (kg ha^-1), protein content (g kg^-1 DM), lipid content (mg g^-1 DM) and essential amino acid composition (g per 16 gN) of cowpea seeds using 15 cultivars grown in three locations (Kano (12°00′ N 8°31′ E), Mokwa (9°17′ N 5°04′ E) and Ago-Iwoye (6°58′ N 4°00′ E)) that differ markedly in climate was studied. The environmental effect accounted largely for the variability observed in yield (93%), protein (71%), lipid (100%), threonine (96%), cystine (80%) and arginine (81%) while the genotypic effect accounted largely for the variability observed in methionine (56%) and lysine (51%) contents. Correlation coefficients (pooled data) from the three locations indicated that yield was negatively correlated to protein content (r=-0·87, P<0·001) and positively correlated to lipid content (r=0·73, P<0·001). Protein content was negatively correlated to lipid content (r=-0·67, P<0·001) and positively correlated to threonine (r=0·66, P<0·01), cystine (r=0·69, P<0·001) and methionine (r=0·88, P<0·001) contents. Similarly, yield was positively correlated to threonine (r=0·22, 0·01<P<0·05), cystine (r=0·38, 0·001<P<0·01) and methionine (r=0·67, 0·001<P<0·01). Yield showed a strong negative correlation with protein content (r=-0·81) and a strong positive correlation with lipid content (r=0·97) at the environmental level. Cystine, methionine and to some extent, threonine were the limiting amino acids in the three environments. This research established the degree of variability for these characters in cowpea and indicated that concurrent selection for yield, lipid content, threonine and sulphur amino acids compositions is feasible. © 1997 SCI.