Ultrasound-assisted impregnation for high temperature Fischer-Tropsch catalysts

A fraction of the petroleum extracted from oil reservoirs contains associated natural gas. Rather than building infrastructure to recover low volumes of this natural gas, the industry flares or vents it to the atmosphere, which contributes to atmospheric greenhouse gas emissions but also reduces the air quality locally because it contains gaseous sulphur and nitrogen compounds. Converting the natural gas (NG) to hydrocarbons with a small-scale two-step gas-to-liquids process, is an alternative to flaring and venting. In the first step, NG reacts with oxygen to form syngas (Catalytic Partial Oxidation) and in the second step the syngas reacts over metallic catalysts to form higher paraffins at 210 degrees C to 300 degrees C-Fischer Tropsch synthesis (FT). For the first time, we synthesize bimetallic FeCo FT catalysts with ultrasound. An ultrasonic horn agitates the solution during the entire impregnation process. The active phase dispersion of the sonicated catalysts was superior to the catalyst synthesized without ultrasound, while reducing the impregnation time by a factor of three. We tested our catalysts in a lab-scale, fixed-bed reactor at 270 degrees C and 300 degrees C, and achieved 80% conversion over 3-days on stream and a 40% yield of C2+

Sustainable manufacture of insect repellents derived from Nepeta cataria

Malaria devastates sub-Saharan Africa; the World Health Organization (WHO) estimates that 212 million people contract malaria annually and that the plasmodium virus will kill 419 000 in 2017. The disease affects rural populations who have the least economic means to fight it. Impregnated mosquito nets have reduced the mortality rate but the Anopheles mosquitoes are changing their feeding patterns and have become more active at dusk and early morning rather than after 22h00 as an adaptation to the nets. Everyone is susceptible to the Anopheles at these times but infants and pregnant women are the most vulnerable to the disease. Plant-based mosquito repellents are as effective as synthetic repellents that protect people from bites. They are sustainable preventative measures against malaria not only because of their efficacy but because the local population can produce and distribute them, which represents a source of economic growth for rural areas. Here, we extract and test the essential oil nepetalactone from Nepeta cataria via steam distillation. Families in endemic areas of Burundi found them effective against bites but commented that the odor was pungent. An epidemiological study is required to establish its clinical efficacy

Ultrasonic free fatty acids esterification in tobacco and canola oil

Ultrasound accelerates the free fatty acids esterification rate by reducing the mass transfer resistance between methanol in the liquid phase and absorbed organic species on Amberlyst\uae46 catalyst. The reaction rates of canola oil is three times greater than for tobacco seed oil but half the reaction rate of pure oleic acid as measured in a batch reactor. The beneficial effects of ultrasound vs. the conventional approach are more pronounced at lower temperatures (20 \ub0C and 40 \ub0C vs. 63 \ub0C): at 20 \ub0C, the free fatty acids conversion reaches 68% vs. 23% with conventional mechanical stirring. The increased conversion is attributed to acoustic cavitation that increases mass transfer in the vicinity of the active sites. The Eley-Rideal kinetic model in which the concentration of the reacting species is expressed taking into account the mass transfer between the phases is in excellent agreement with the experimental data. Ultrasound increases the mass transfer coefficient in the tobacco oil 6 and 4.1 fold at 20 \ub0C and 40 \ub0C, respectively

LiFePO4 spray drying scale-up and carbon-cage for improved cyclability

The growing market for electrical vehicles requires inexpensive, long-lasting batteries. LiFePO4 (LFP) melt-synthesized from ore concentrate fits this role, but the manufacturing process requires additional steps that includes grinding large ingots into a nanoparticle suspension followed by a dessication step. Spray drying, rather than tray drying, creates a mesopomus powder that enhances wettability. Adding lactose and high-Mw polyvinyl alcohol (PVA) to the suspension of nanostructures followed by pyrolysis, creates a carbon-cage that interconnects the cathode nanoparticles, imparting better capacity (LiFePO4/C: 161 mA h g(-1) at 0.1C), discharge rate (flat plateau, 145 mA h g(-1) at 5C), and cyclability (91% capacity retention after 750 cycles at 1C). Particle size affects battery stability; PVA increases the suspension's viscosity and alters the powder morphology, from spherical to hollow particles. A model describes the non-Newtonian suspension's rheology changing: shear, temperature, LFP and PVA loading. Carbon precursors prevent the nanoparticles from sintering during calcination but lactose gasifies 50% of the carbon, according to the chemical and allotropic composition measurements (CS analyzer, XPS, and Raman). The carbon-cage imparts micmporosity and we correlate the SEM and TEM powder's morphology with N2 physisorption porosimetry. Ultrasonication of the suspension fragments the PVA chain, which is detrimental to the final cathode performance

Sonochemical techniques to increase the efficiency of methyl esters production from non-food oils

Industrially practiced transesterification for biodiesel production can accept a restricted range of feedstocks, with free fatty acids (FFA) concentration and moisture content lower than 0.5 and 0.2%wt, respectively. Refined oils usually match this requirement but their use increases biodiesel production costs, besides being in competition with food production. Non-food raw oils may require several pretreatment steps before proceeding with the transesterification. The search for high efficiency transformation methods is therefore a key issue. In this work, FFA esterification, catalysed by ion exchange resins, and the homogeneously catalysed transesterification to produce fatty acids methyl esters are studied using single and combined sonochemical techniques such as ultrasound and microwaves. The results show that microwaves are able to enhance FFA esterification activity, allowing to achieve 90% of conversion in 2 hours rather than 4 hours, required by the traditional method. US increases tremendously transesterification conversions, yielding methyl esters above 96.5%wt within 30 minutes, while more than 2 hours are usually required with the traditional method. Moreover, much lower reagents and catalyst amount are requires when ultrasound are applied. The positive effect of microwaves is attributable to the re-orientation of the methanol dipole leading to the formation of a methanol-oil/emulsion with very high exchange area between the phases. The benefits brought by the use of ultrasound may be ascribed to both chemical and physical effects generated by acoustic cavitation

Caffeine versus aminophylline for the prevention of apnoea of prematurity in a teaching hospital in South Africa

Study objectives: To determine the safety and efficacy of the use of oral anhydrous caffeine and intravenous aminophylline in the neonatal population using therapeutic drug levels and clinical effects as markers for determination.Design: Prospective randomised study.Patients: Thirty-one neonates admitted (aminophylline n = 16, caffeine n = 15) with a gestational age of less than or equal to 34 weeks for prevention of apnoea of prematurity (AOP) were enrolled.Results: Oral anhydrous caffeine or intravenous aminophylline were administered using prescribed study regimens. One peak level was taken for the two drugs on day 4 of treatment 2 hours after the maintenance dose was administered. The two regimens were clinically monitored using cardiovascular, respiratory, gastro-intestinal and central nervous system parameters four hourly. The two groups did not differ significantly for gestational age (p = 0.782), birth weight (p = 1), gender (p = 0.722), and Apgar scores determined at 5 minutes (p = 0.068). Serum concentrations were within range (5–20 μg/ml) for both study groups. The median pulse rate (beats per minute) for two days; day 7: 160 vs. 148 (p = 0.019); day 9: 168 vs. 147 (p = 0.020) and median respiratory rate (breaths per minute) for five days; day 3: 68 vs. 61 (p = 0.039); day 4: 67 vs. 57 (p = 0.014); day 5: 64 vs. 58 (p = 0.045); day 7: 65 vs. 50 (p = 0.021); day 8: 66 vs. 56 p = 0.014) were significantly higher in the aminophylline study arm.Conclusion: The findings of the study indicated that caffeine is an effective alternative for intravenous aminophylline in prevention of AOP. The oral administration of caffeine may also have an advantage in a resource-poor setting

Gas-Phase Fructose Conversion to Furfural in a Microfluidized Bed Reactor

Specialty chemicals from sugars are destined to displace fermentation to alcohols due to their superior economic value and atom efficiency. Compared to bioethanol, retention of oxygen functional groups increases by 2-5 times the market value of specialty chemicals like furfural, 2,5-furan dicarboxylic acid, 2,5-dimethyl furan, and gamma-valerolactone. For the first time, we report a gas-phase process that converts C-6 monosaccharides to furfural in a microfluidized bed reactor. A spray nozzle inserted directly into the catalytic bed atomizes a fructose water solution to micron-sized droplets; water evaporates, and WO3/TiO2 converts fructose to furfural. Furfural yield reached 22% after 3 h time-on-stream with 15% diformyl furan as coproduct. Acetic acid yield was mostly below 10% but was as high as 27%. During the initial tests, coke and catalyst agglomerates blocked the sparger tip, and run time varied between 1 and 3 h. Insulating the nozzle leading into the bed reduced the injector wall temperature and improved reactor operability; the 15 mm i.d. reactor ran continuously for 19 h after this modification

Ultrasound and microwave assisted preparation of high Fe loaded supported catalysts for biosyngas Fischer-Tropsch conversion

Supported Fe- based catalysts have several advantages (greater surface area, better dispersion of the heat developed by the reaction and better mechanical resistance) compared to massive iron catalysts adopted in the current Fischer Tropsch (FT) industrial plants. In particular, the optimized components loading was found to correspond to 30 wt% Fe supported on silica and promoted with K (2.0 wt%) and Cu (3.75 wt%) [1]. In order to study the influence of the preparation procedure, three different kind of catalysts were synthesized according to three different methods: 1) the traditional impregnation (TR) [1]; 2) Ultrasound (US) assisted TR method; 3) Microwave (MW) assisted TR method. All the samples were fully characterized by BET, ICP/OES, XRPD, TG-DTA, FT-IR, TPR, SEM and TEM and tested in a laboratory pilot plant. FT reaction activity tests were carried out in a fixed bed tubular reactor, using 1 g of fresh catalyst mixed with 1 g of diluting material (\u3b1-Al2O3, Fluka). All the catalysts were reduced in situ by a flow of H2/CO (molar ratio of 2/1) at 350\ub0C, 500 kPa for 4 h and tested with the standard conditions of 46.8 Nml min-1 flow of syngas (molar ratio of 2/1) plus 5.0 Nml min-1 of N2 as internal standard, at 2MPa and T= 250\ub0C for 90 h, as detailed in [1, 2]. The results of the characterization of the catalysts indicated that the morphology of the samples strongly depends on the method of preparation. Moreover, the samples treated with MW and US have higher surface areas than the traditional ones (Tab. 1). FT catalytic results are displayed in Table 1. The best results in term of C2+ yield (41%), with a good value of selectivity towards heavy hydrocarbons, was obtained using MW, while in terms of CO conversion (58%), using US. The samples prepared with non-traditional methods show better FT results, probably due to a more wide and uniform distribution of Fe achieved during the synthesis. This result was verified by TEM and is in agreement with previous results [3]

FeCrAl as a Catalyst Support

The iron-chromium-aluminum alloy (FeCrAl) is an exceptional support for highly exothermic and endothermic reactions that operate above 700 \ub0C in chemically aggressive environments, where low heat and mass transfer rates limit reaction yield. FeCrAl two- and three-dimensional structured networks - monoliths, foams, and fibers - maximize mass transfer rates, while their remarkable thermal conductivity minimizes hot spots and thermal gradients. Another advantage of the open FeCrAl structure is the low pressure drop due to the high void fraction and regularity of the internal path. The surface Al2O3 layer, formed after an initial thermal oxidation, supports a wide range of metal and metal oxide active phases. The aluminum oxide that adheres to the metal surface protects it from corrosive atmospheres and carbon (carburization), thus allowing FeCrAl to operate at a higher temperature. The top applications are industrial burners, in which compact knitted metal fibers distribute heat over large surface areas, and automotive tail gas converters. Future applications include producing H2 and syngas from remote natural gas in modular units. This Review summarizes the specific preparation techniques, details process operating conditions and catalyst performance of several classes of reactions, and highlights positive and challenging aspects of FeCrAl