Spherical silica supported Hyflon® catalysts (SSHC) were developed to produce ethers from glycerol by etherification reaction with isobutene. SSHC allowed to obtain yields to di- and tri-ethers, suitable as additives or components for diesel fuels, higher than that obtained with A-15 commercial catalyst, and a concentration of undesired mono-ether (not soluble in diesel) lower than 3 wt%. The novel catalysts investigated were found stable and easily reusable; their low acid site density prevented the occurrence of oligomerization reaction accounting for di-isobutene formation. Engine tests performed using a blend containing 10 vol% of glycerol ethers mixture confirmed the positive role of additives in reducing emissions of particulates and unburned hydrocarbons with significant improvement of diesel combustion efficiency. 相似文献
We disclose the highly diastereoselective combination of monoamine oxidase‐catalyzed oxidation of meso‐pyrrolidines and aza‐Friedel–Crafts reactions in aqueous buffer to give valuable enantioenriched 2‐substituted pyrrolidines in a formal double C H activation process. A range of secondary as well as tertiary amines were shown to be suitable substrates for the biocatalytic oxidation and subsequent addition of a variety of C‐nucleophiles.
Triacylglycerols (TAG) are the most important group of compounds present in vegetable oils. These biomolecules, determining the physical, chemical and nutritional properties of the oils, are considered to be good fingerprints for quality and authenticity control. Therefore, TAGs characterization is a very important task in edible oil field, which has been undertaken by different analytical methods. The analysis of vegetable oils is still dominated by classic determinations, which are however laborious and time‐consuming and cannot be used routinely. More recently, advances in MS instrumentations coupled with online separation techniques and data processing have contributed to great expansion of MS in oil study, allowing the development of innovative analytical approaches that exhibit higher sensitivity, accuracy and rapidity in vegetable oils investigations. In the present contribution, a review of the most relevant applications of novel mass spectrometric techniques, such as ESI and MALDI, both alone and hyphenated with HPLC, used for analysis of the complex TAGs mixture of edible oils is illustrated. 相似文献
The design shear resistance of an existing structure can be evaluated with analytical design procedures and numerical procedures provided by non‐linear finite element analyses. The new fib Model Code 2010 proposes different calculation methods that fall into four different levels of approximation. As the level of approximation rises, so the complexity and the accuracy of the calculated shear resistance increases. Non‐linear finite element analyses belong to the highest level of approximation, but although they are more and more becoming a customary tool in the daily design process, building codes do not provide guidance on how to perform these analyses. This paper describes non‐linear finite element analyses performed on prestressed beams, which underwent shear failure during experimental loading, in order to assess and criticize the finite element approaches. The aim of this work is to propose guidelines for numerical simulations in order to reduce model and user factors. The results obtained from the non‐linear finite element analyses have been compared with the analytical results using different levels of approximation. The design shear resistance obtained with the highest level of approximation, level IV, derived from non‐linear finite element analyses, turned out to be higher than the design shear resistance obtained with analytical procedures (levels I/II/III). 相似文献
The aim of this research is to compare the predictions of the design load‐carrying capacity of slabs obtained with simplified analytical and numerical procedures which can be readily used by analysts in the current design process. The research fits into a research programme initiated by the Dutch Ministry of Infrastructure and the Environment for the re‐examination of the load‐carrying capacity of existing bridges and viaducts, and the beams and slabs they include, through the use of non‐linear finite‐element analyses. The behaviour of reinforced concrete slabs subjected to concentrated loads close to their supports is investigated in this contribution. Three tests from a series of 18 slabs with a total of 108 tests, tested at Delft University of Technology, were selected as case studies and analysed with non‐linear finite‐element analyses and analytical models either proposed by design codes or available in the literature. The research agrees well with the philosophy of the fib Model Code for Concrete Structures 2010, which offers different analytical and numerical calculation methods for evaluating the design shear resistance of reinforced concrete members according to different levels of approximation. For the three slabs investigated in this study, it indeed pays to use higher levels of approximation. The highest level (level IV) based on non‐linear finite element analysis gives the highest design load resistance, but still well below the resistance obtained experimentally. 相似文献
Sulfur-bridged polyaniline coatings are obtained onto Fe anodes by electrolyzing a basic solution of one aniline and ammonium sulfide. Their sulfur content ranges from 7% to 17%, depending on the substituents on aniline. Variously substituted anilines may be polymerized in this way and coating pollution by azobenzene formed in a side reaction is almost completely avoided. Sulfur probably enters the polymer chains through a free radical mechanism. HS? intermediates being formed by both homogeneous and anodic oxidation of HS? anions. Coatings from N-allylaniline, being thermally curable, show satisfactory physical properties. 相似文献
The development of an integrated two stage liquefaction process was traced. Initial studies involved conversion of a solvent refined coal (SRC) extract in an L.C. Fining® expanded bed catalytic hydrotreater representing the second stage of a two stage process. Favorable results prompted construction of an integrated unit which incorporated a short contact time coal extraction unit, a solvent deashing unit and an L.C. Finer second stage. High yields of high quality distillate (51.7 weight percent MF coal) with reduced hydrogen consumption (4.32 weight percent) were demonstrated under steady state conditions over extended run periods. 相似文献
