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991.
A two‐step synthetic procedure is designed for preparing new flame‐retardant methacrylic monomers containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as a substituent side group. DOPO and methacrylate moieties are linked by linear aliphatic hydrocarbon spacers (3 to 11 carbon atoms). Copolymerization with methyl methacrylate is carried out leading to copolymers containing between 2 and 10 wt% phosphorus. All homo‐ and copolymers exhibit a unique glass transition temperature (Tg ). A new group contribution for DOPO‐based substituent is extracted that leads to reasonable estimations of Tg s of other published polymers. The Fox equation provides a good estimation of Tg s for most copolymers and for physical blends of poly(methyl methacrylate) (PMMA) and DOPO. When using monomers having three and four carbon atoms in the hydrocarbon spacer, the Tg of copolymers remains close to that of PMMA over a wide range of composition. 相似文献
992.
François Malherbe Jean‐Pierre Besse Steven R. Wade Warren J. Smith 《Catalysis Letters》2000,67(2-4):73-79
The catalytic activity of a series of mixed oxides obtained by the thermal decomposition of hydrotalcite‐like precursors was
assessed for the alkoxylation of n-butanol with ethylene oxide. The calcination products of a decavanadate intercalated magnesium–aluminium layered double hydroxide
were shown to possess extremely high activity for the alkoxylation reaction achieving up to 100% conversion in batch reaction.
In all cases, the catalysts exhibit a much higher selectivity towards the monoglycol adduct than that obtained with the industrial
catalyst.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
Yanis Caro Pierre Villeneuve Michel Pina Max Reynes Jean Graille 《Journal of the American Oil Chemists' Society》2000,77(8):891-902
The protein contents in crude latices from various varieties of papaya (Carica papaya) and their catalytic activities in proteolysis, lipolysis, and interesterification reactions were studied with regard to
the variety, the geographic location of cultures, and the frequency of fruit tapping. Biocatalytic activities of these raw
materials were compared to several commercially available crude and purified preparations of papain. These investigations
were carried out in order to have a better physicochemical characterization of these raw materials, to select the adequate
papaya latex for protein or lipid bioconversions, and to valorize them on an industrial scale. For the purified preparations
of papain, only proteolytic activity was obtained. All crude papaya latices exhibit proteolytic, lipolytic, and interesterification
activities, and no relationship between the proteolytic and lipolytic activities was observed. The high multiple correlation
coefficient (R) on the order of R=0.93–0.99, obtained from the regression analysis for the lipolytic and interesterification activities for all crude papaya
latices investigated suggested that there was a correlation between these enzyme activities. However, for the same lipase
preparation, the interesterification activity differed substantially depending on the type of interesterification reaction. 相似文献
994.
Electrical conductivity measurements on EUROCAT V2O5–WO3/TiO2 catalyst and on its precursor without vanadia were performed at 300°C under pure oxygen to characterize the samples, under NO and under NH3 to determine the mode of reactivity of these reactants and under two reaction mixtures ((i) 2000 ppm NO + 2000 ppm NH3 without O2, and (ii) 2000 ppm NO + 2000 ppm NH3 + 500 ppm O2) to put in evidence redox processes in SCR deNOx reaction.It was first demonstrated that titania support contains certain amounts of dissolved W6+ and V5+ ions, whose dissolution in the lattice of titania creates an n-type doping effect. Electrical conductivity revealed that the so-called reference pure titania monolith was highly doped by heterovalent cations whose valency was higher than +4. Subsequent chemical analyses revealed that so-called pure titania reference catalyst was actually the WO3/TiO2 precursor of V2O5–WO3/TiO2 EUROCAT catalyst. It contained an average amount of 0.37 at.% W6+dissolved in titania, i.e. 1.07 × 1020 W6+ cations dissolved/cm3 of titania. For the fresh catalyst, the mean amounts of W6+ and V5+ ions dissolved in titania were found to be equal to 1.07 × 1020 and 4.47 × 1020 cm−3, respectively. For the used catalyst, the mean amounts of W6+ and V5+ ions dissolved were found to be equal to 1.07 × 1020 and 7.42 × 1020 cm−3, respectively. Since fresh and used catalysts have similar compositions and similar catalytic behaviours, the only manifestation of ageing was a supplementary progressive dissolution of 2.9 × 1020 additional V5+ cations in titania.After a prompt removal of oxygen, it appeared that NO alone has an electron acceptor character, linked to its possible ionosorption as NO− and to the filling of anionic vacancies, mostly present on vanadia. Ammonia had a strong reducing behaviour with the formation of singly ionized vacancies. A subsequent introduction of NO indicated a donor character of this molecule, in opposition to its first adsorption. This was ascribed to its reaction with previously adsorbed ammonia strongly bound to acidic sites. Under NO + NH3 reaction mixture in the absence of oxygen, the increase of electrical conductivity was ascribed to the formation of anionic vacancies, mainly on vanadia, created by dehydroxylation and dehydration of the surface. These anionic vacancies were initially subsequently filled by the oxygen atom of NO. No atoms, resulting from the dissociation of NO and from ammonia dehydrogenation, recombined into dinitrogen molecules. The reaction corresponded to
. In the presence of oxygen, NO did not exhibit anymore its electron acceptor character, since the filling of anionic vacancies was performed by oxygen from the gas phase. NO reacted directly with ammonia strongly bound on acidic sites. A tentative redox mechanism was proposed for both cases. 相似文献
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995.
Sbastien Bessenet Viviane Renaudin Jean‐Pierre Leclerc Jean‐Marie Hornut 《加拿大化工杂志》2000,78(3):486-494
A hydrodynamic study of a new graphite evaporator has been performed. In this exchanger the fluid flows as a thin film on a spirally wound fin which forms a spiral staircase inside a tube. The slope θm of the spirally wound fin is modifiable. The residence time distribution (RTD) of the film was measured for different fin slopes θm and several film flowrates mf. The flow pattern was then modelled thanks to the DTS software as a cascade of perfect mixed cells and the mean residence time τm was calculated. The evolution of τm as a function of θm and mf is accurately represented by a power law relation. 相似文献
996.
Xiaohong Gu Lipiin Sung Bouchra Kidah Mounira Oudina Cyril Clerici Haiqing Hu Debbie Stanley Walter E. Byrd Jerry Y. C. Jean Tinh Nguyen Jonathan W. Martin 《Journal of Coatings Technology and Research》2009,6(1):67-79
Surface topography and gloss are two related properties affecting the appearance of a polymeric coating system. Upon exposure
to ultraviolet (UV) radiation, the surface topography of a coating becomes more pronounced and, correspondingly, its gloss
generally decreases. However, the surface factors affecting gloss and appearance are difficult to ascertain. In this article,
atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) measurements have been performed on an amine-cured
epoxy coating system exposed to outdoor environments in Gaithersburg, Maryland. The formation of the protuberances is observed
at the early degradation stages, followed by the appearance of circular pits as exposure continues. At long exposure times,
the circular features enlarge and deepen, resulting in a rough surface topography and crack formation. Fourier Transform Infrared
Spectroscopy (FTIR) study indicates that the oxidation and chain scission reactions are likely the origins of the surface
morphological changes. The relationship between changes in surface roughness and gloss has been analyzed. The root mean square
(RMS) roughness of the coating is related to nanoscale and microscale morphological changes in the surface of the coating
as well as to the gloss retention. A near-linear dependence of RMS roughness with the measurement length scale (L) is found on a double logarithmic scale, i.e., RMS ∼ L
f. The scaling factor, f, decreases with exposure time. The relationship between surface topography, on nano- to microscales,
and the macroscale optical properties such as gloss retention is discussed. Moreover, a recent development in using an angle-resolved
light scattering technique for the measurement of the specular and off-specular reflectance of the UV-exposed specimens is
also demonstrated, and the optical scattering data are compared to the gloss and the roughness results.
相似文献
Xiaohong GuEmail: |
997.
Amine Barkallah Johana Mörée Jose Sanchez Stephanie Druon Bocquet Jean Rivenc 《American Institute of Chemical Engineers》2009,55(2):294-311
Experimental and theoretical approaches based on a mathematical model, have been developed to study the evolution of environmental parameters (temperature, total pressure, relative humidity, and water vapor partial pressure) inside a housing of an electronic device with a window containing a macroporous membrane. The model was based on the coupling of mass and heat transfer taking into account the effects of polarization of concentration in boundary layers. Membranes have been characterized by mercury porosimetry, liquid entry pressure measurements, scanning electron microscopy, and gas permeation. Once the model was experimentally validated, it was applied to investigate the influence of membranes on heat and mass transfer and to study the impact of the boundary layers on the global mass transport. The results demonstrated the importance of the membrane choice and dimensions to get the best temperature regulation and avoid water condensation inside an automotive electronic control unit (ECU). © 2008 American Institute of Chemical Engineers AIChE J, 2009 相似文献
998.
Sophie L. Pirard Jean‐Paul Pirard Christophe Bossuot 《American Institute of Chemical Engineers》2009,55(3):675-686
The modeling of carbon nanotube production by the CCVD process in a continuous rotary reactor with mobile bed was performed according to a rigorous chemical reaction engineering approach. The geometric, hydrodynamic, physical and physicochemical factors governing the process were analyzed in order to establish the reactor equations. While the study of the hydrodynamic factor suggests a co‐current plug‐flow approximation, the physical factor mainly deals with the phenomena of transport and the transfer of mass, which can be neglected. Concerning the physicochemical factor, the modeling is based on knowledge of the expression of the initial reaction rate, and takes into account catalytic deactivation as a function of time, according to a sigmoid decreasing law. The reactor modeling allows obtaining the evolution of partial pressure, carbon nanotube production and catalytic deactivation along the reactor for given initial operating conditions. The comparison between experimental and calculated production highlights a very good fit of data. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
999.
Jean‐Louis Reymond 《Chembiochem : a European journal of chemical biology》2009,10(9):1569-1570
Wiley, Hoboken 2009, 3188 pp., hardcover $ 1200.00.—ISBN 978‐0‐471‐75477‐0
1000.
Jozsef M. Berty Sunggyu Lee Ferenc Szeifert Jean B. Cropley 《Chemical Engineering Communications》1989,76(1):9-33
Testing kinetic models against a “true” and detailed kinetic expression was the aim of the Workshop on Kinetic Model Development at the Denver AIChE Meeting in August, 1983. For this purpose an artificial reaction mechanism was created, based on the known thermodynamics of the methanol synthesis as a framework. The kinetic rate laws, that were derived from this mechanism, were made thermodynamically consistent by achieving agreement between equilibrium constants calculated at various temperatures from the given, real original thermodynamic relationship and those calculated from the detailed reversible kinetic expressions.
Using the artificial kinetics as the "true" one, CSTR experiments were simulated. The results of a statistically designed set of experiments were published after 5% random error was added to the data. Participation was invited for all interested to correlate the data, develop kinetic models and to calculate the performance of the specified reactor.
The results of 19 submitted entries are summarized with the conclusion that the models had more differences than were expected, but their predictive values were not as different as was anticipated, if the extreme high production rates due to thermal runaways are not considered. This in turn points out the necessity to check models experimentally, in pilot plant, not only for predicted optimum, but also for calculated runaway conditions. Models which did not capture the true character of this reaction failed to predict the onset of runaway reactions. 相似文献
Using the artificial kinetics as the "true" one, CSTR experiments were simulated. The results of a statistically designed set of experiments were published after 5% random error was added to the data. Participation was invited for all interested to correlate the data, develop kinetic models and to calculate the performance of the specified reactor.
The results of 19 submitted entries are summarized with the conclusion that the models had more differences than were expected, but their predictive values were not as different as was anticipated, if the extreme high production rates due to thermal runaways are not considered. This in turn points out the necessity to check models experimentally, in pilot plant, not only for predicted optimum, but also for calculated runaway conditions. Models which did not capture the true character of this reaction failed to predict the onset of runaway reactions. 相似文献