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991.
Wonjin Jeon Chunghyeon Ban Geonu Park Jeong Eun Kim Hee Chul Woo Do Heui Kim 《Catalysis Surveys from Asia》2016,20(4):195-209
Alginate, a main carbohydrate compound of macroalgae, can be hydrothermally converted to valuable organic products, such as furfural and organic acids, over various types of catalysts. In this review, alginate is evaluated as a renewable biomass feedstock for the production of the useful chemicals, based on the structural differences between alginate and conventional lignocellulosic biomass feedstocks. The influence of different catalysts and reaction conditions on the alginate depolymerization and the product distribution is discussed. Finally, future research direction for the catalytic conversion of alginate is suggested. 相似文献
992.
The chiral oxazaborolidinium salts 1 and 2 are excellent catalysts for the enantioselective cyanosilylation of a wide variety of aldehydes (see Table 1) using trimethylsilyl (TMS) cyanide and triphenylphosphine oxide as the source of a new reactive cyanide donor. This donor appears to be the isocyanophosphorane Ph3P(OTMS)(N=C:) (4). The novel process described herein has several advantages: predictability of absolute configuration of cyanohydrin products from a mechanistic model (3), high yields and very good enantiomeric purity of products (>/=90%), and, finally, easy and efficient recovery of the catalytic ligand. 相似文献
993.
Phospholipids derived from egg yolk are readily separated by DEAE-silica gel column chromatography using stepwise gradient elution. The overall recovery of phospholipids from the column is 85-95% at a loading capacity of 120 mg of lipids per 10 g of DEAE-silica gel. The complete separation of eight phospholipids (phosphatidylcholine, sphingomyelin, lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine and lysophosphatidylserine; 5 micrograms each) is also achieved by one-dimensional DEAE-silica gel thin-layer chromatography with the solvent system chloroform-methanol-water-pyridine-58% ammonia solution (130:55:8:4:4, v/v). 相似文献
994.
Central composite designs (CCDs) were used in the study of the ion-pair chromatographic separation of arsenic and selenium species in tap water: monomethylarsonate, dimethylarsinate, selenomethionine and selenite. The ternary eluent consisted of tetrabutylammonium phosphate (TBA), sodium hydrogenphosphate (Na2HPO4) and 1% acetonitrile. CCD allowed the investigation of the influence of the eluent parameters, which varied from 0.5 to 4.2 mmol l-1 Na2HPO4, 0.5 to 4.2 mmol l-1 TBA and pH 4.9 to 8.2, on the capacity factors (k') of arsenic and selenium compounds. Furthermore, another mathematical model that permitted the variation of the chromatographic selectivity of species, computed from their retention data to be followed, was investigated. This showed the ability to locate the optimum conditions within the experimental design, so that arsenic and selenium species could be simultaneously quantified with good efficiency and resolution. A comparison between the predicted and the experimental response values was made in order to assess the prediction quality of the model. Response surfaces and isoresponse curves obtained from the mathematical models allowed the determination of the optimum chromatographic conditions and the robustness of the method. The predicted optimum zone allowing satisfactory determination of both arsenic and selenium compounds was pH 5.5-6.5, 2.5 mmol l-1 Na2HPO4 and 3.0-4.0 mmol l-1 TBA. 相似文献
995.
Adsorption equilibria and dynamics ofn-butane on two activated carbon samples prepared from the physical activation of nutshell are studied in this paper. The micropore size distribution (MPSD) is considered as the main source of solid heterogeneity. Lennard-Jones' potential theory and Dubinin's theory (TVFM) are used in the equilibria data to derive the MPSD, which is well fitted by a Gamma distribution function. The adsorption energy distribution derived from the MPSD is very asymmetric for both the samples studied, and this energy distribution used in the HMSD/HMSMD kinetics models for the study of adsorption dynamics ofn-butane. 相似文献
996.
Hong Le Khiem Nguyen Van Do Pham Duc Khue 《Journal of Radioanalytical and Nuclear Chemistry》1998,231(1-2):157-161
The (n,2n) threshold reaction cross-sections, available in the literature are analysed for nuclei with 20≤Z≤92 in the neutron energy range of about 14.5 MeV. An empirical formula based on multiple regression technique is proposed
for quick estimation of the (n,2n) reaction cross sections. The results obtained are compared with experimental data and those
from other empirical formulae as long as byN-Z systematic. The validity of this formula is discussed. 相似文献
997.
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1000.
Vinh-Thang H Huang Q Eić M Trong-On D Kaliaguine S 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):5094-5101
In our recent studies (Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Langmuir 2005, 21, 2051-2057; Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Stud. Surf. Sci. Catal. 2005, in press), a series of synthesized SBA-15 materials were characterized using nitrogen adsorption/desorption isotherms at 77 K and SEM images. In the present paper, four of them (MMS-1-RT, MMS-1-60, MMS-1-80, and MMS-5-80) were further investigated with regard to their equilibrium characteristics using n-heptane and toluene as sorbates by the standard gravimetric technique. SBA-15 materials proved to have a broad pore size distribution within the micropore/small-mesopore range in the walls of their main mesoporous channels. The adsorption capacities for toluene were found to be higher than for n-heptane. The isosteric heats of adsorption, estimated by the Clausius-Clapeyron equation, are also higher for toluene compared to n-heptane. They were found to depend on framework microporosity of the relevant SBA-15 samples. The isosteric heats of adsorption for all sorbates decrease with increased loading and approach the heats of evaporation of the respective sorbate. The adsorption capacities of SBA-15 samples are significantly higher than those of silicalite, i.e., the MFI zeolite silica analogue. In contrast to that, the isosteric heats of adsorption in the mesopore channels of SBA-15 were found to be much smaller. This result also suggests that SBA-15 can potentially be a good candidate for separation of C(7) hydrocarbons. 相似文献