The separation of highly alkylated polycyclic aromatic compounds according to the size of their aromatic system is investigated using the polycyclic aromatic sulfur heterocycles in vacuum gas oil. A large number of reference compounds containing several parent ring systems and different alkylation patterns were first investigated to characterize the retention of polycyclic aromatic compounds likely to occur in high-boiling petroleum samples. A beta-cyclodextrin phase, Merck ChiraDex, was found to be more suitable than chemically bonded aminopropanosilane and tetrachlorophthalimide in normal-phase HPLC with respect to a combination of selectivity towards the number of aromatic double bonds and degree of influence of the alkyl groups of the aromatic compounds. Finally the preseparated polycyclic aromatic sulfur heterocycles from a vacuum gas oil were fractionated according to the number of condensed aromatic rings on the ChiraDex phase and were characterized by Fourier transform ion cyclotron resonance mass spectrometry. 相似文献
Physochlaina praealta samples were studied macromorphologically and cytomorphologically along with their detailed phytochemical investigation. The concentration of phytoconstituents showed a strong positive correlation with the ploidy level and altitudinal gradients. The total phenol content was detected maximum in the methanolic extract of leaves and stem of higher altitudinal plants in both cytotypes (2x, 4x). The maximum content of flavonoids was detected in the methanolic extract of root and leaves. Root organ from higher elevation possessed the highest DPPH radical scavenging activity, with the maximum percentage of inhibition being obtained in methanolic extracts. The plants of both cytotypes from higher elevations accumulate an abundant quantity of secondary metabolites. The two cytotypes differ from each other with respect to various morphometric characters thereby depicting the drastic affect of polyploidy.
This study investigates the effect of additives in the nonsolvent water in terms of cloud point during the phase inversion of Polysulfone (PS) in dimethyl formamide (DMF). The exponential pattern is observed with PS concentration (0.2 to 0.6% (w/w)). It needs a low amount of water to get the cloud point at low temperature. The cloud point varied with the nature of water matrix and depended on the amount of salt, as well as the PS amount. The presence of salts (sodium chloride and sodium sulfate) lowers the cloud point of the solution. The network distribution of the particles at the cloud point is disturbed in the presence of salt. The requirement is more for Sodium lauryl sulfate (SLS) added water to reach the cloud point in the low range of PS solution up to 0.3% PS (w/w). The morphological and distribution pattern of PS particles are very different compared to PS particles produced from pure water. XRD study of PS particles produced from the mixed water system reflects relatively more amorphous character with respect to PS particles from pure water. The presence of both surfactant and salts in water systems also influences the cloud point in synergistic manner. 相似文献
Induced acoustic wave to bare fiber through various types of horn are examined. The center wavelength and extinction ratio of the notch filter are dynamically tunable and dependent on the RF signals. 相似文献
In the present study a new low cost, easily available and environmentally friendly adsorbent was used for removal of Cr (VI).
The Cr (VI) removal efficiency of the adsorbent was studied as a function of contact time, pH, adsorbent dose, adsorbate concentration,
temperature and stirring speed. Different adsorption model equations for kinetics, isotherm and rate mechanism of the process
were used to find the best model, which fit well to the experimental data. A full factorial design of nk type was used to find a mathematical relation between the percentage of adsorption and variables affecting the adsorption
process such as time, pH, adsorbate concentration and temperature. Using the Students ‘t’ test, the significance of each term
of the derived equation was tested. The insignificant terms were removed from the derived equation. The adequacy of the equation
after removing the insignificant terms was tested using the Fisher adequacy test. From the factorial design analysis it is
found that pH has the most pronounced effect followed by time, temperature and the adsorbate concentration. A column study
was performed using the optimum operating conditions. 相似文献
The reactions of two isomers of 3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (differing in the orientation of the methyl groups on the chiral carbon atoms), designated as L(B) and L(C), with CH(3)I in the ratio of 1:4 resulted in the substitution of the N(4) and N(11) protons by CH(3) groups, forming the dimethyl derivatives L(BZ) and L(CZ), respectively. These ligands, on interaction with nickel(II) acetate tetrahydrate and subsequent addition of lithium perchlorate, produce square-planar yellow [NiL(BZ)][ClO(4)](2) and orange [NiL(C'Z)][ClO(4)](2). These nickel complexes undergo axial ligand addition reactions with NCS(-), Cl(-), Br(-), and I(-) as X(-) to form six-coordinate trans-diisothiocyanato, -dichloro, -dibromo, and -diiodo complexes of formula [NiLX(2)], where L = L(BZ) or L(C'Z), and X = SCN, Cl, Br, or I. All these compounds have been characterized on the basis of analytical, spectroscopic, conductometric, and magnetochemical data. The structures of L(BZ) and two variants of [Ni"L(BZ)"][ClO(4)](2) (crystallizing in the space group P2(1)/n and Pn, respectively; "L(BZ)" symbolizes partially methylated ligand) have been determined by single-crystal X-ray analyses. The antifungal and antibacterial activities of these compounds have been studied against some phytopathogenic fungi and bacteria. 相似文献
DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a general method for the synthesis of 3-substituted phthalides. This method, in combination with mercuric acetate mediated oxidative aromatization has been utilized for the regiospecific synthesis of isopestacin (9) and cryphonectric acid (10). 相似文献