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1.
Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO 2, O 2, N 2, CF 4, n-C 4H 10 and i-C 4H 10, as well as binary mixtures of CH 4/ n-C 4H 10 and N 2/CF 4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH 4/ n-C 4H 10 mixtures and higher than 8100 for the N 2/CF 4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines. 相似文献
2.
采用旋涂法在粗糙的 α-Al 2O 3载体片上制备出较完备的分子筛晶种层;以四丙基氢氧化铵(TPAOH)为有机模板剂,通过调控合成液的H 2O/Si摩尔比,实现了对分子筛晶体面内优先生长的调控;经过三次水热合成得到致密交联的 h0 h-轴取向高硅MFI分子筛膜,膜厚约为8 μm(包括~5 μm致密层和~3 μm过渡层)。采用先低温加氢裂解后低温空气氧化的两步法脱除工艺,有效脱除了分子筛膜内的有机模板剂。相比于传统高温煅烧法,该法可以避免分子筛膜因脱除模板剂而形成的较大晶间缺陷。因而采用低温两步法脱除模板剂的分子筛膜片在30 ℃时具有较好的CO 2分离效果,其CO 2/N 2分离因子达到5.2, CO 2渗透通量高达5.8 × 10 -7mol·m -2·s -11·Pa -1。 相似文献
3.
The new iodoammonium salts o-C 6H 4(NH 2) 2I +I − (1) and o-C 6H 4(NH 2) 2I + AsF 6− (2) were prepared by reaction of o-phenylene diamine with I 2 or I 3+AsF 6−, respectively. Compound 1 reacts with AlI 3 yielding quantitatively the corresponding tetraiodoaluminate o-C 6H 4(NH 2) 2I +AlI 4− (3). The species were characterized by chemical analysis, vibrational (IR and Raman) and temperature-dependent 1H NMR spectropscopy. Direct evidence for a N---I bond was found in the Raman spectra of 1, 2 and 3 (ν(NI) = 599–600 cm −1). 相似文献
4.
Rate coefficients for the reactions of cyclohexadienyl ( c-C 6H 7) radicals with O 2 and NO were measured at 296 ± 2 K. The c-C 6H 7 radicals were detected selectively by laser-induced fluorescence. The rate coefficient for the reaction of c-C 6H 7 with O 2, (4.4 ± 0.5) × 10 −14 cm 3 molecule −1 s −1, was independent of the bath-gas (He) pressure (13–80 Torr). In the reaction of c-C 6H 7 with NO, thermal equilibrium among c-C 6H 7, NO, and C 6H 7NO was observed. The forward and reverse reactions were in the falloff region, and the equilibrium constant was (1.5 ± 0.6) × 10 −15 cm 3 molecule −1. 相似文献
5.
Reaction of [Cp *TiF 3] (Cp * = (ν 5-C 5Me 5)) with Me 3SiOSO 2- p-C 6H 4CH 3, Me 3SiOPOPh 2 and 1,2-(Me 3SiOCO) 2C 6H 4 yields the dinuclear complexes [{Cp *TiF(μ-F)(μ-OSO 2- p-C 6H 4CH 4)} 2] (1), [{Cp *TiF(μ-F)(μ-OPOPh 2)} 2] (2) and [{Cp *TiF(μ-F)(μ-OCO- o-C 6H 4CO 2SiMe 3)} 2] (3). The molecular structures of 1 and 2 have been determined by single-crystal X-ray analysis. In complexes 1-3, the two titanium atoms are connected by bridging fluorine atoms as well as bridging sulfonate, phosphinate and carboxylate groups respectively. Each titanium atom is also bonded to a terminal fluorine atom. Reaction of [Cp 2*ZrF 2] with 1,2-(Me 3SiOCO) 2C 6H 4 leads to the mononuclear pentacoordinate 18-electron species [Cp 2*ZrF(μ-OCO- o-C 6H 4CO 2SiMe 3)] (4) and its structure was determined by X-ray crystallographic methods. 相似文献
6.
Efficient separation of C4 olefins is of critical importance and a challenging task in petrochemical industry. Covalent organic frameworks(COFs) could be used as promising candidates for membrane-based isobutene/1,3-butadiene( i-C 4H 8/C 4H 6) separation. Owing to large amounts of COFs appearing, however, the rapid prediction of optimal COFs is imperative before experimental efforts. In this work, we combine molecular simulation and machine learning to study COF membranes for efficient isolation of i-C 4H 8 over C 4H 6. Using molecular simulation, four potential COF membranes, which possess both high membrane performance score (MPS) value and moderate membrane selectivity were screened out and the mechanism of membrane separation further revealed is an adsorption dominated process. Further, random forest(RF) model with high prediction accuracy(R 2>0.84) was obtained and used for elucidating key factors in controlling the membrane selectivity and i-C 4H 8 permeability. Ultimately, the optimal COF features were obtained through structure-performance relationship study. Our results may trigger experimental efforts to accelerate the design of novel COFs with better i-C 4H 8/C 4H 6separation performance. 相似文献
7.
The conversion of n-C 4H 10 was undertaken on MoO 3/HZSM-5 catalyst at 773–973 K and the phases of molybdenum species were detected by XRD. The XRD results show that bulk MoO 3 on HZSM-5 can be readily reduced by n-C 4H 10 to MoO 2 at 773 K and MoO 2 can be gradually carburized to molybdenum carbide above 813 K. The molybdenum carbide formed from the carburization of MoO 2 with n-C 4H 10 below 893 K is -MoC 1−x with fcc-structure, while hcp-molybdenum carbide formed above 933 K. During the evolution of MoO 3 to MoO 2 (>773 K) or the carburization of MoO 2 to molybdenum carbide (>813 K), deep oxidation, cracking and coke deposition are serious, in particular at higher reaction temperatures, these lead to the poor selectivity to aromatics. Aromatization of n-C 4H 10 can proceed catalytically on both Mo 2C/HZSM-5 and MoO 2/HZSM-5, the distribution of the products for the two catalysts is similar below 813 K, but the activity for Mo 2C/HZSM-5 is much higher than that for MoO 2/HZSM-5. 相似文献
8.
The photodissociation dynamics of the 3s Rydberg state of three ketones (CH 3CO–R, R=C 2H 5, C 3H 7, and iso-C 4H 9) and the ensuing dissociation of the nascent acetyl radical following 195 nm excitation were investigated by ultrafast photoionization spectroscopy. The 3s state the lifetimes of these ketones are similar (2.5–2.9 ps), though lifetimes of the acetyl radical range from 8.6 ps for CH 3CO–C 2H 5, 15 ps for CH 3CO–C 3H 7, to 23 ps for CH 3CO–( iso-C 4H 9), which suggests that for larger R more vibrational degrees of freedom compete for the excess energy so that less energy is partitioned into the internal energy of the acetyl radical. 相似文献
9.
Closo-B nH n−2(CO) 2 ( n = 5–12), isolobal analogues of closo-C 2B n−2H n, have been investigated at the B3LYP/6-311+G **density functional level of theory. The most stable isomers of closo-B nH n−2(CO) 2 are similar to those of closo-C 2B n−2H n in geometric patterns apart from closo-B 6H 4(CO) 2, and closo-B nH n−2(CO) 2 is much less strained than closo-C 2B n−2H n. Energetic analysis identifies closo-B 6H 4(CO) 2, closo-B 12H 10(CO) 2 and closo-B 10H 8(CO) 2 to be most stable, of which the latter two cages have been prepared experimentally. On the basis of the negative and rather large nucleus independent chemical shifts (NICS), closo-B nH n−2(CO) 2 are aromatic. To aid further experimental study, the CO stretching frequencies have been computed. 相似文献
10.
Two organogold derivatives of diphenylmethane and diphenylethane, Ph 3PAu( o-C 6H 4)CH 2(C 6H 4- o)AuPPh 3 (1) and Ph 3PAu( o-C 6H 4)(CH 2) 2(C 6H 4- o)AuPPh 3 (2), have been synthesized by the reaction of ClAuPPh 3 with Li( o-C 6H 4)CH 2(C 6H 4- o)Li and Li( o-C 6H 4)(CH 2) 2(C 6H 4- o)Li respectively. The interaction of 1 with dppe results in the replacement of the two PPh 3 groups to give a macrocyclic compound (3) that includes an Au Au bond. Compounds 1 and 2 react with one or two equivalents of [Ph 3PAu]BF 4 to form new types of cationic complex [CH 2(C 6H 4- o) 2(AuPPh 3) 3]BF 4 (4), [CH 2(C 6H 4- o) 2(AuPPh 3) 4](BF 4) 2 (5), and [(CH 2) 2(C 6H 4- o) 2(AuPPh 3) 4](BF 4) 2 (6). Complexes 1–6 have been characterized by X-ray diffraction studies, FAB MS, and IR as well as by 1H and 31P NMR spectroscopy. A complicated system of Au H-C agostic interactions, involving the bridging alkyl groups (—CH 2— and CH 2-CH 2—) of diphenylmethane and diphenylethane ligands, has been found to occur in complexes 1–3 and 6. 相似文献
11.
MFI-type zeolite membranes prepared by liquid phase hydrothermal synthesis on tubular commercial supports were used to remove model pollutants n-hexane, formaldehyde and benzene present at very low concentration levels (2–230 ppmv) in indoor air. The influence of several operating parameters was studied both in batch and continuous separation experiments. Depending on the operation conditions, permeation fluxes of the organic compound up to 3300, 130 and 30 mg/(m 2 h) and organic/air separation factors of 250, 6.3 and 38 were achieved for n-hexane, formaldehyde and benzene, respectively. 相似文献
12.
The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and e aq− react with NIPAAm with rate coefficient of (6.9±1.2)×10 9, (6.6±1)×10 9, and (1.0±0.2)×10 10 mol −1 dm 3 s −1. In OH and H radical addition to the double bond mainly -carboxyalkyl type radicals form, (OHCH 2CH √C(N- i-C 3H 7)O and CH 3CH √C(N- i-C 3H 7)O). In reaction of e aq− oxygen atom centered radical anion is produced (CH 2CHC √(N- i-C 3H 7)O −), the anion undergoes reversible protonation with p Ka=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH 3CH √C(N- i-C 3H 7)O). The -carboxyalkyl type radicals at low NIPAAm concentration (0.1–1 mmol dm −3) mainly disappear in self-termination reactions, 2 kt,m=8.4×10 8 mol −1 dm 3 s −1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2 kt≈2×10 8 mol −1 dm 3 s 1. 相似文献
13.
The reaction of the labelled carborane ligand [3-Et-7,8-Ph 2-7,8- nido-C 2B 9H 8] 2− with a source of {Pt(PMe 2Ph) 2} 2+ affords non-isomerised 1,2-Ph 2-3,3-(PMe 2Ph) 2-6-Et-3,1,2- closo-PtC 2B 9H 8 (1). The analogous reaction between [3-F-7,8-Ph 2-7,8- nido-C 2B 9H 8] 2− and {Pt(PMe 2Ph) 2} 2+ yields 1,8-Ph 2-2,2-(PMe 2Ph) 2-4-F-2,1,8- closo-PtC 2B 9H 8 (3). Compound 1 has a heavily slipped structure ( Δ 0.72 Å), which to some degree obviates the need for C atom isomerisation. However, that it is a kinetic product of the reaction is evident from the fact that it reverts to isomerised 1,8-Ph 2-2,2-(PMe 2Ph) 2-4-Et-2,1,8- closo-PtC 2B 9H 8 (2) slowly at room temperature but more rapidly with gentle warming. The heteroatom and labelled-B atom positions in the isomerised compounds 2 and 3 may be explained most simply by the rotation of a CB 2 face of an intermediate based on the structure of 1. Compounds 1–3 were characterised by a combination of spectroscopic and crystallographic techniques. 相似文献
14.
Distibines of the type R 2SbSbR′ 2 with R = CH 3, R′ = C 2H 5 (1), R = CH 3, R′= n-C 3H 7 (2), R = CH 3, R′= C 6H 5 (3), R = C 2H 5, R′= C 6H 5 (4), R = n-C 3H 7, R′ = C 6H 5 (5), and R = CH 3, R′ = 2,4,6-(CH 3) 2C 6H 2 (6) are formed in equilibria by exchange reactions of the respective distibines of the type R 4Sb 2 and R′ 4Sb 2. 相似文献
15.
Excess molar enthalpies HE and excess molar volumes VE have been measured, as a function of mole fraction x1, at 298.15 K and atmospheric pressure for the five liquid mixtures ( x11,4-C 6H 4F 2 + x2n-C lH 2l+2), l = 7, 8, 10, 12 and 16. In addition, HE and excess molar heat capacities CPE at constant pressure have been determined for the two liquid mixtures ( x1C 6F 6 + x2n-C lH 2l+2), l = 7 and 14, at the same temperature and pressure. The instruments used were flow microcalorimeters of the Picker design (the HE version was equipped with separators) and a vibrating-tube densimeter, respectively. The excess enthalpies of the five difluorobenzene mixtures are all positive and quite large; they increase with increasing chain length l of the n-alkane from HE(x1 = 0.5)/(J mol−1) = 1050 for l = 7 to 1359 for l = 16. The corresponding excess volumes VE are all positive and also increase with increasing l: VE(x1 = 0.5)/(cm3 mol−1) = 0.650 for l = 7 and 1.080 for l = 16. Interestingly, the excess enthalphies of the corresponding mixtures with hexafluorobenzene are only about 5% larger, whereas the excess volumes of (x1C6F6 + x2n-ClH2l+2) are roughly twice as large as those of their counterparts in the series containing 1,4-C6H4F2. Specifically, at 298.15 K HE(x1 = 0.5)/(J mol−1) = 1119 for (x1C6F6 + x2n-C7H16) and 1324 for (x1C6F6 + x2n-C14H30), and for the same mixtures VE(x1 = 0.5)/(cm3 mol−1) = 1.882 and 2.093, respectively. The excess heat capacities for both systems are negative and of about the same magnitude as the excess heat capacities of mixtures of fluorobenzene with the same n-alkanes (Roux et al., 1984): CPE(x1 = 0.5)/(J K−1 mol−1) = −1.18 for (x1C6F6 + x2n-C7H16), and −2.25 for (x1C6F6 + x2n-C14H30). The curve CPE vs. (x1 for x1C6F6 + x2n-C14H30) shows a sort of “hump” for x1 0.5, which is presumed to indicate emerging W-shape composition dependence at lower temperatures. 相似文献
16.
An investigation of the frontier molecular orbitais of o- and p-RC 6H 4NC (R=H, CH 3, NO 2, F, Cl, CF 3, OCH 3) was carried out so that a thorough understanding of the intricacies of σ donation and π acceptance could be developed and used to modify subtly the electron density on metal centers. The results of this study-Indicate that the substituent position (ortho vs. para ) does alter the electron density in the ligand appreciably and that substitution of the phenyl ring with the groups indicated has a smaller effect on the σ-donating ability than it does on the π-accepting ability of the isonitrile ligand. The π-accepting abilities of the isonitrile ligands increase in the order o-, p-CH3OC6H4NC, o-, p-CH3C6H4NC, o-, p-C6H5NC, o-, p-FC6H4NC, o-, p-CF3C6NC, o-, p-ClC6H4NC, o-, p-NO2C6H4NC while the σ-donating ability decreases in this order. The energies of the σ-donor and π-acceptor orbitais are shown to correlate well with observed E
values of Cr(RC6H4NC)6 and Mn(RC6H4NC)6+1 complexes. This demonstrates how the theoretical results can be useful in understanding the observed physical properties of isonitrile-metal complexes. 相似文献
17.
We show that thermal desorption kinetics clearly resolve adsorbates bound in different sites on single walled carbon nanotube bundles. The molecules n-C 9H 20 and CCl 4 were compared and it was found that the nanotube internal sites exhibited the highest desorption temperature, whereas external groove sites exhibited the next highest desorption temperature for both molecules. When n-C 9H 20 and CCl 4 coadsorb, the more strongly bound n-C 9H 20 quantitatively displaces CCl 4 from internal sites to groove sites. Molecular shape governs the capacity of the different sites for the two molecules. 相似文献
18.
采用二次生长法在多孔α-Al 2O 3载体上制备MFI型(ZSM-5和silicate-1)分子筛膜;通过XRD和SEM检测,证明所合成的分子筛膜为致密、交联和无取向的MFI型分子筛膜,厚度为5 μm;单组分气体渗透实验检测中,所制备样品膜的N 2渗透量均小于10 -11 mol/(m 2·s·Pa),可认为其无缺陷;同时,考察了样品分子筛膜对H 2S/CH 4混合气的分离效果,在渗透压分别为0.3和0.5 MPa时,silicate-1分子筛膜的H 2S/CH 4的分离因子分别为1.99和4.44,而ZSM-5分子筛膜的CH 4/H 2S的分离因子分别为6.71和12.85。 相似文献
19.
Using velocity map ion imaging technique, the photodissociation of n-C 4H 9Br in the wavelength range 231–267 nm was studied. The results and our ab initio calculations indicated that the absorption of n-C 4H 9Br in the investigated region originated from the excitations to the lowest three repulsive states, as assigned as 1A″, 2A′ and 3A′ in C s symmetry. Dissociations occurred on the PES surfaces of the three states, terminating in C 4H 9+Br ( 2P 3/2) or C 4H 9 + Br * ( 2P 1/2) as two channels, and being impacted by an avoided crossing between the PES surfaces of the 2A′ and 3A′ states. The transition dipole to the 1A″ state was perpendicular to the symmetry plane, so perpendicular to the C–Br bond. The transitions to the 3A′ state was polarized parallel to the symmetry plane, and also parallel to the C–Br bond. While the transition dipole to the 2A′ state was in the symmetry plane, but formed an angle of about 53.1° with the C–Br bond. We have also determined the avoided crossing probabilities, which affected the relative fractions of the individual pathways, for the photolysis of n-C 4H 9Br near 234 nm and 267 nm. 相似文献
20.
A thin, gas-tight palladium (Pd) membrane was prepared by the counter-diffusion chemical vapor deposition (CVD) process employing palladium chloride (PdCl 2) vapor and H 2 as Pd precursors. A disk-shaped, two-layer porous ceramic membrane consisting of a fine-pore γ-Al 2O 3 top layer and a coarse-pore -Al 2O 3 substrate was used as Pd membrane support. A 0.5–1 μm thick metallic membrane was deposited in the γ-Al 2O 3 top layer very close to its surface, as verified by XRD and SEM with a backscattered electron detector. The most important parameters that affected the CVD process were reaction temperature, reactants concentrations and top layer quality. Deposition of Pd in the γ-Al 2O 3 top layer resulted in a 100- to 1000-fold reduction in He permeance of the porous substrate. The H 2 permeation flux of these membranes was in the range 0.5–1.0 × 10 −6 mol m −2 s −1 Pa −1 at 350–450°C. The H 2 permeation data suggest that surface reaction steps are rate-limiting for H 2 transport through such thin membranes in the temperature range studied. 相似文献
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