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排序方式: 共有107条查询结果,搜索用时 15 毫秒
1.
Groothaert MH Smeets PJ Sels BF Jacobs PA Schoonheydt RA 《Journal of the American Chemical Society》2005,127(5):1394-1395
This work reports on the capability of the O2-activated Cu-ZSM-5 and Cu-MOR zeolites to selectively convert methane into methanol at a temperature of 398 K. A strong correlation between (i) the activity and (ii) the intensity of the 22 700 cm-1 UV-vis band, assigned to the bis(mu-oxo)dicopper core, is found (i) as a function of the reaction temperature, (ii) as a function of the Cu loading of the zeolite, and (iii) in comparison to other Cu materials. These three lines of evidence firmly support the key role of the bis(mu-oxo)dicopper core in this selective, low-temperature hydroxylation of methane. 相似文献
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PHOTOSENSITIZING PROPERTIES OF BACTERIOCHLOROPHYLLIN a and BACTERIOCHLORIN a, TWO DERIVATIVES OF BACTERIOCHLOROPHYLL a 总被引:2,自引:0,他引:2
Eva M. Beems Tom M. A. R. Dubbelman Johan Lugtenburg Jaap A. van Best Monique F. M. A. Smeets J. Pierre J. Boegheim 《Photochemistry and photobiology》1987,46(5):639-643
Abstract The photosensitizing properties of two water soluble derivatives of bacteriochlorophyll a , bacteriochlorophyllin a and bacteriochlorin a (lacking the central Mg-ion) were investigated and compared to those of hematoporphyrin derivatives. At physiological pH the oxygen consumption rate of histidine, tryptophan, dithiothreitol and guanosine upon illumination was 3 to 4 times higher when bacteriochlorin a was used as photosensitizer than when hematoporphyrin derivatives were used. Especially bacteriochlorin a proved to be an effective sensitizer for the killing of L929 cells. Because bacteriochlorin a has an absorption maximum at 765 nm in phosphate buffered saline (allowing a light penetration in tissue about ten times larger than at 630 nm) and a high molar absorption coefficient (32 000 M cm−1 ) it has promising possibilities for the application in photodynamic therapy. 相似文献
5.
The cyclopropanation reactions of α, β-epoxy diazomethyl ketones 1 with olefins using Pd(OAc)2 as catalyst is described. Differently substituted epoxy diazo ketones 1a-1f give with cyclohexene exo-norcarane derivatives. 3, 3-Diphenyloxiranyl-2 diazomethyl ketone 1a reacts with olefins like isobutene, E- and Z- butene-2 to give epoxy cyclopropyl ketones. 3, 3-Diphenyloxiranyl-2 cyclopropyl ketones 2a and 9 undergo two consecutive rearrangement reactions with BF3 as catalyst. In the first step an epoxide rearrangement of 9 takes place to give β-ketoaldehyde 10, which in a second step rearranges to enolester 12. The latter reaction is most likely restricted to β-ketoaldehydes which have a quaternary α-C atom. A rationale for this unusual reaction has been proposed. 相似文献
6.
Dr. Yi Luo Dr. Stef Smeets Dr. Zhendong Wang Prof. Junliang Sun Prof. Weimin Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(9):2184-2188
A new germanosilicate zeolite named SCM-15 (Sinopec Composite Material No. 15), the first zeolite containing a 3-dimensional (3D) channel system with interconnected 12-, 12-, and 10-ring channels (pore sizes: 6.1×7.2, 6.1×7.4, and 5.2×5.9 Å), has been synthesized using neutral 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs). Its structure has been determined by combining single-crystal electron diffraction (SCED) and synchrotron powder X-ray diffraction (SPXD) data. The unique open framework structure of SCM-15 is related to that of FOS-5 ( BEC ), ITQ-7 ( ISV ), PKU-16 ( POS ), ITQ-26 ( IWS ), ITQ-21, Beta polymorph B, and SU-78B, since all these framework structures can be constructed from similar chains which are connected through shared 4-ring or double 4-ring (d4r) units. Based on this relation, six topologically reasonable 3D large or extra-large pore hypothetical zeolites are predicted. 相似文献
7.
B. Smeets P. van?der Straten T. Meijer C. G. C. H. M. Fabrie K. A. H. van Leeuwen 《Applied physics. B, Lasers and optics》2010,98(4):697-705
Using direct-write atom lithography, Fe nanolines are deposited with a pitch of 186 nm, a full width at half maximum (FWHM)
of 50 nm, and a height of up to 6 nm. These values are achieved by relying on geometrical collimation of the atomic beam,
thus without using laser collimation techniques. This opens the way for applying direct-write atom lithography to a wide variety
of elements. 相似文献
8.
Subbiah Meenakshisundaram RM. Sockalingam 《Journal of molecular catalysis. A, Chemical》2000,160(2):269-275
Catalytic activity of Os(VIII) in the oxidation of some twenty organic sulfides with sodium salt of N-chlorobenzenesulfonamide (CAB) has been investigated in alkaline (pH8.7) t-butanol–water (1:1 v/v) medium. Significant retarding influence of [OH−] on the reactivity is exhibited. The catalysed reaction is strongly accelerated in the presence of Hg(II). Imperfections are observed in the linear Hammett relationship in the case of –NO2 substituents. 相似文献
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Niels M. B. Smeets Johan P. A. Heuts Jan Meuldijk Michael F. Cunningham Alex M. Van Herk 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):5078-5089
The effect the catalytic chain transfer agent, bis[(difluoroboryl) dimethylglyoximato] cobalt(II) (COBF), on the course of the ab initio emulsion polymerization of methyl methacrylate, and the product properties in terms of the molecular weight distribution were investigated. The emulsion polymerization kinetics have been studied with varying surfactant, initiator, and COBF concentrations. The experimentally determined average number of radicals per particle strongly depends on the concentration of COBF and proves to be in good agreement with the results of model calculations. The apparent chain transfer constant, determined up to high conversion, is in excellent agreement with the predicted value based on a mathematical model based on COBF partitioning and the Mayo equation. The results of this work enhance the fundamental understanding of the influence a catalytic chain transfer agent has on the course of the emulsion polymerization and the control of the molecular weight distribution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5078–5089, 2009 相似文献