Abstract
We propose a novel method for estimating the permeability of heterogeneous sandstones based on the nuclear magnetic resonance (NMR) data with multiple echo spacings. The decaying curves and ...their corresponding spectra are obtained for different echo spacings to investigate the relaxation property, the diffusion term, and the signal loss contributed by higher echo spacing. Moreover, an empirical model is developed to correlate permeability with the differential decay rate. The result shows that the geometric transversal relaxation time is positively related to echo spacing, which disobeys the traditional cognition. Moreover, the absolute value of the differential decay rate is positively correlated with the echo spacing and exhibits a power law behavior. More interestingly, it is observed that the permeability diminishes in a power law behavior with respect to fitting parameters. This marks the first attempt to establish a relationship between the permeability and NMR data with different echo spacings, which is hopeful to be extended to other complex reservoirs with the availability of multiple echo spacing data.
The self‐assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π‐coordination of a tripodal ligand (L) with acetylene ...spacers gave an M3L2 double‐propeller motif (M=CuI or AgI), which dimerized into an M6L4 interlocked cage (M=CuI). Higher (M3L2)n oligomers were also selectively obtained: an M12L8 truncated tetrahedron (M=CuI) and an M18L12 truncated trigonal prism (M=AgI), both of which contain the same double‐propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.
Die Komplexierung eines verdrehten Triarylmethan‐Liganden mit CuI‐ oder AgI‐Ionen ergibt M6L4‐, M12L8‐ und M18L12‐Koordinationspolyeder, die als vernetzte und verknäuelte Oligomere eines hypothetischen M3L2‐Doppelpropellers betrachtet werden können, die durch schwache Acetylen‐π‐Wechselwirkungen stabilisiert werden.
A series of platinum(II) alkynyl‐based sensitizers has been synthesized and found to show light‐to‐electricity conversion properties. These dyes were developed as sensitizers for the application in ...nanocrystalline TiO2 dye‐sensitized solar cells (DSSCs). Their photophysical and electrochemical properties were studied. The excited‐state property was probed using nanosecond transient absorption spectroscopy, which showed the formation of a charge‐separated state that arises from the intramolecular photoinduced charge transfer from the platinum(II) alkynylbithienylbenzothiadiazole moiety (donor) to the polypyridyl ligand (acceptor). A lifetime of 3.4 μs was observed for the charge‐separated state. A dye‐sensitized solar cell based on one of the complexes showed a short‐circuit photocurrent of 7.12 mA cm−2, an open circuit voltage of 780 mV, and a fill factor of 0.65, thus giving an overall power conversion efficiency of 3.6 %.
Electric company: A series of platinum(II) alkynyl‐based sensitizers has been synthesized and found to show light‐to‐electricity conversion properties (see graphic). A dye‐sensitized solar cell based on one of the complexes shows a fill factor of 0.65 and a power‐conversion efficiency of 3.6 %.
Conducting polymer microelectrodes can electrochemically generate the catalyst required for their own functionalization by “click chemistry” with high spatial resolution. Interdigitated ...microelectrodes prepared from an azide‐containing conducting polymer are selectively functionalized in sequence by two alkyne‐modified fluorophores by control of the applied potentials.
Süße Kristalle: Die Synthese von Polysacchariden wird durch viele Faktoren erschwert. Die topochemische Azid‐Alkin‐Cycloadditionspolymerisation eines ungeschützten Monosaccharids umgeht diese ...Probleme und liefert regioselektiv ein kristallines Glycopolymer in quantitativer Ausbeute.
Rotating foam stirrer reactors have a promising application in multiphase reactions. In this reactor, highly porous open-celled materials, solid foams, are used both as a catalyst support and as ...stirrer blades. One of the advantages of such a foam stirrer is easy catalyst handling. This paper presents a preparation method for catalysts on solid foam supports. The performance of the alumina foam catalysts is tested in the hydrogenation of a functionalized alkyne. A stable and homogeneous catalytic coating was deposited on aluminum foams by a combination of anodization and wash coating using the slurry method. Anodization produced a rough and porous material that improved the adhesion of the catalytic coating. The use of a slurry with a bimodal particle size distribution increased the catalytic coating stability. The mass loss of the catalytic coating after applying ultrasonic vibrations was less than 10 wt %, which indicates a good adhesion. A high specific surface area was achieved by increasing the foam cell density, that is, the number of pores per linear inch (ppi), and the catalytic coating thickness. With the wash-coating method, catalytic coatings were produced having a thickness between 10 and 40 μm, a porosity of around 50%, and a specific surface area up to 28.5 m2/gfoam. The hydrogenation of 3-methyl-1-pentyn-3-ol was chosen as the test reaction. Internal and external mass transfers limit the reaction rate of this fast reaction. High activity and selectivity were reached by combining a high specific surface area with a thin catalytic coating on the foam. Increasing the foam cell density up to 20 ppi led to enhanced liquid−solid mass transfer because of the high specific surface area combined with the fast refreshment of the catalyst surface. Coating thicknesses of less than 20 μm led to improved internal mass transfer due to shorter diffusion paths.
Pd-catalyzed oxidation of alkynes Muzart, Jacques
Journal of molecular catalysis. A, Chemical,
03/2011, Letnik:
338, Številka:
1
Journal Article
Recenzirano
The different Pd-catalyzed procedures leading to the oxidation of the C
C bonds are reviewed.
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► This review highlights the Pd-catalyzed procedures leading to the oxidation of C
C ...bonds. ► The procedures are exemplified using 19 equations and 8 tables. ► Plausible mechanisms and reactive intermediates are depicted in 5 schemes.
This review surveys the different Pd-catalyzed procedures leading to the oxidation of the C
C bonds. The reactivity and selectivity depend on the substitution of the triple bond, 1,2-diarylethynes being the most reactive. The main oxidation product, an 1,2-diketone, an ester or a furan, depends on both the used procedure and the substrate. Plausible mechanisms are, as far as possible, provided.
Eine einfache Gold‐katalysierte Methode für die Synthese von substituierten und modifizierbaren Azulenen wurde entwickelt. Die Azulene werden entweder über die Dimerisierung von ...Push‐Pull‐Diarylalkinen mit Fluor‐Substituenten in ortho‐ oder para‐Position, oder über die Dimerisierung eines symmetrischen elektronenreichen Diarylalkins gebildet. In Anwesenheit eines kationischen Gold‐Katalysators bilden die zwei Alkine ein hoch reaktives Vinyl‐Kation. Diese energiereiche Zwischenstufe wird durch eine passende Aryl‐Einheit abgefangen, sodass liefert in einem einzigen, perfekt atomökonomischen Schritt substituierte Azulene erhalten werden.
Auf perfekt atomökonomische Weise ermöglicht ein einfaches Gold‐katalysiertes Protokoll einen direkten Zugang zu substituierten Azulenen aus leicht zugänglichen Ausgangsverbindungen. Ein Fluor‐Substituent als starker +M‐Donor initiiert diese Reaktion. Die erhaltenen Gerüste können am siebengliedrigen Ring leicht und selektiv weiter modifiziert werden.
The smallest spherical carbon nanocage so far, 2.2.2carbon nanocage, has been synthesized by the cationic rhodium(I)/H8‐binap complex‐catalyzed regioselective intermolecular cyclotrimerization of a ...cis‐1‐ethynyl‐4‐arylcyclohexadiene derivative followed by the triple Suzuki–Miyaura cross‐couplings with 1,3,5‐triborylbenzene and reductive aromatization. This cage molecule is highly strained, and its ring strain is between those of 6 and 5cycloparaphenylenes. A significant red‐shift of an emission maximum was observed, compared with that of known 4.4.4carbon nanocage. The sequential cyclotrimerizations of a cis‐1,4‐diethynylcyclohexadiene derivative with the same rhodium(I) catalyst followed by reductive aromatization failed to afford 1.1.1carbon nanocage; instead, a β‐graph‐shaped cage molecule was generated.
Der kleinste sphärische Kohlenstoff‐Nanokäfig (2.2.2‐Nanokäfig) wurde durch regioselektive intermolekulare Homocyclotrimerisierung eines cis‐1‐Ethinyl‐4‐bromphenylcyclohexadien‐Derivats, dreifache Suzuki‐Miyaura‐Kreuzkupplung mit 1,3,5‐Triborylbenzol und reduktive Aromatisierung in Gegenwart des kationischen Rhodium(I)/H8‐binap‐Komplexes synthetisiert.
Membrane gas separation technologies (air separation, hydrogen recovery from dehydrogenation processes, etc.) use traditionally the glassy polymer membranes with dominating permeability of “small” ...gas molecules. For this purposes the membranes based on the low free volume glassy polymers (e.g., polysulfone, tetrabromopolycarbonate and polyimides) are used. On the other hand, an application of membrane methods for VOCs and some toxic gas recovery from air, separation of the lower hydrocarbons containing mixtures (in petrochemistry and oil refining) needs the membranes with preferable penetration of components with relatively larger molecular sizes. In general, this kind of permeability is characterized for rubbers and for the high free volume glassy polymers. Data files accumulated (more than 1500 polymeric materials) represent the region of parameters “inside” of these “boundaries.” Two main approaches to the prediction of gas permeability of polymers are considered in this paper: (1) the statistical treatment of published transport parameters of polymers and (2) the prediction using model of ≪diffusion jump≫ with consideration of the key properties of the diffusing molecule and polymeric matrix. In the frames of (1) the paper presents N-dimensional methods of the gas permeability estimation of polymers using the correlations “selectivity/permeability.” It is found that the optimal accuracy of prediction is provided at
n
=
4. In the frames of the solution–diffusion mechanism (2) the key properties include the effective molecular cross-section of penetrating species to be responsible for molecular transportation in polymeric matrix and the well known force constant
(ε/k)
eff i
of {6–12} potential for gas–gas interaction. Set of corrected effective molecular cross-section of penetrant including noble gases (He, Ne, Ar, Kr, Xe), permanent gases (H
2, O
2, N
2, CO), ballast and toxic gases (CO
2, NO
, NO
2, SO
2, H
2S) and linear lower hydrocarbons (CH
4, C
2H
6, C
3H
8, C
4H
10, C
2H
4, C
3H
6, C
4H
8 - 1, C
2H
2, C
3H
4–m (methylacetylene) and C
3H
4–a (allen) is determined by using two above mentioned approaches. All of this allows calculating preliminary the permeability parameters of above mentioned gases for most part of known polymers based on limited experimental data.
The new correlations suggested demonstrate that the available free volume of polymeric matrix plays an important role in providing of rate and selectivity of gas diffusion for glassy-like polymers; the rate and selectivity of gas diffusion in rubbers is affected mainly by cohesion energy density (CED) the both polymer parameters being calculated by traditional additive group contributions technique.
Results of present study are demonstrated by calculation of expected permeability parameters in relation to lower hydrocarbons and some toxic gases for polynorbornene based polymers, PIM and PTMSP outlining potential of practical application for new membrane polymers.
General equations
lg
(
P
i
)
=
K
1
+
K
2
(
d
2
i
)
+
K
3
(
ε
i
/
k
)
,
…
lg
P
n
=
K
1
+
K
2
d
2
n
+
K
3
(
ε
n
/
k
)
,
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►New N-dimensional approach for prediction of gas permeability parameters of polymers ►Corrected Stuart's diameters of penetrant's molecules can be used for calculation of permanent gases, linear lower hydrocarbons and some toxic gas permeability for polymers when these data are even unavailable. ►Expected gas permeability for set of modern polymers is calculated.
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