История развития математических знаний

Isosorbide is a platform chemical of considerable importance for the future replacement of fossil resource-based products. Applications as monomers and building blocks for new polymers and functional materials, new organic solvents, for medical and pharmaceutical applications, and even as fuels or fuel additives are conceivable. The conversion of isosorbide to valuable derivatives by functionalization or substitution of the hydroxyl groups is difficult because of the different configurations of the 2- and 5-positions and the resulting different reactivity and steric hindrance of the two hydroxyl groups. Although a substantial amount of work has been published using exclusively the endo or exo derivatives isomannide and isoidide, respectively, as starting material, a considerable effort is still necessary to transfer and adapt these methods for the efficient conversion of isosorbide. This Minireview deals with all aspects of isosorbide chemistry, which includes its production by catalytic processes, special properties, and chemical transformations for its utilization in biogenic polymers and other applications of interest

Isolation of a euryhaline microalgal strain, Tetraselmis sp CTP4, as a robust feedstock for biodiesel production

Bioprospecting for novel microalgal strains is key to improving the feasibility of microalgae-derived biodiesel production. Tetraselmis sp. CTP4 (Chlorophyta, Chlorodendrophyceae) was isolated using fluorescence activated cell sorting (FACS) in order to screen novel lipid-rich microalgae. CTP4 is a robust, euryhaline strain able to grow in seawater growth medium as well as in non-sterile urban wastewater. Because of its large cell size (9-22 mu m), CTP4 settles down after a six-hour sedimentation step. This leads to a medium removal efficiency of 80%, allowing a significant decrease of biomass dewatering costs. Using a two-stage system, a 3-fold increase in lipid content (up to 33% of DW) and a 2-fold enhancement in lipid productivity (up to 52.1 mg L-1 d(-1)) were observed upon exposure to nutrient depletion for 7 days. The biodiesel synthesized from the lipids of CTP4 contained high levels of oleic acid (25.67% of total fatty acids content) and minor amounts of polyunsaturated fatty acids with >= 4 double bonds (< 1%). As a result, this biofuel complies with most of the European (EN14214) and American (ASTM D6751) specifications, which commonly used microalgal feedstocks are usually unable to meet. In conclusion, Tetraselmis sp. CTP4 displays promising features as feedstock with lower downstream processing costs for biomass dewatering and biodiesel refining

Process Optimization for Biodiesel Production from Corn Oil and Its Oxidative Stability

Response surface methodology (RSM) based on central composite design (CCD) was used to optimize biodiesel production process from corn oil. The process variables, temperature and catalyst concentration were found to have significant influence on biodiesel yield. The optimum combination derived via RSM for high corn oil methyl ester yield (99.48%) was found to be 1.18% wt catalyst concentration at a reaction temperature of 55.6∘C. To determine how long biodiesel can safely be stored, it is desirable to have a measurement for the stability of the biodiesel against such oxidation. Storage time and oxygen availability have been considered as possible factors influencing oxidative instability. Biodiesel from corn oil was stored for a period of 30 months, and the physico-chemical parameters of samples were measured at regular interval of time. Results show that the acid value (AV), peroxide value (PV), and viscosity (ν) increased while the iodine value (IV) decreased. These parameters changed very significantly when the sample was stored under normal oxygen atmosphere. However, the ν, AV, and IV of the biodiesel sample which was stored under argon atmosphere were within the limit by the European specifications (EN 14214)

Solvent-free lipase-catalyzed synthesis of a novel hydroxyl-fatty acid derivative of kojic acid

The aim of this work was the synthesis of a novel hydroxyl-fatty acid derivative of kojic acid rich in kojic acid monoricinoleate (KMR) which can be widely used in the cosmetic and food industry. The synthesis of KMR was carried out by lipase-catalysed esterification of ricinoleic and kojic acids in solvent-free system. Three immobilized lipases were tested and the best KMR yields were attained with Lipozyme TL IM and Novozym 435. Since Lipozyme TL IM is the cheapest, it was selected to optimize the reaction conditions. The optimal reaction conditions were 80 °C for the temperature, 1:1 for the alcohol/acid molar ratio, 600 rpm for stirring speed and 7.8% for the catalyst concentration. Under these conditions, the reaction was scaled up in a 5 × 10−3 m3 stirred tank reactor. 1H–13C HMBC-NMR showed that the primary hydroxyl group of kojic acid was regioselectively esterified. The KMR has more lipophilicity than kojic acid and showed antioxidant activity that improves the oxidation stability of biodiesel