Mesopore ZSM-5 was prepared by alkali treatment of parent ZSM-5 zeolite and applied for butene catalytic cracking. The zeolite was treated in the NaOH solutions with different concentrations at 85 °C. XRD showed that the intrinsic MFI structure of ZSM-5 zeolite was preserved and corresponding crystallinity remained unchangeableness when ZSM-5 was treated with low concentration NaOH solutions. However, excessive NaOH led to the destruction of zeolite structure. The BET surface area increased obviously after desilication, and the N2 adsorption/desorption curves indicated a number of mesopores generation. The experiment of butene catalytic cracking was carried out in a fixed-bed to investigate the influence of mesopores. The results showed that catalytic performances can be greatly improved through introducing the mesopores into parent ZSM-5 by alkali treatment. Highest yield of ethylene plus propylene were obtained when the treated concentration of NaOH solution is 0.1–0.2 M. 相似文献
1‐Hexene polymerization was conducted by [t‐BuNSiMe2(3,6‐t‐Bu2Flu)]TiMe2 ( 1 ) using trialkylaluminum‐free modified methylaluminoxane (dMMAO) as a cocatalyst in toluene. The system produced living syndiotactic poly(1‐hexene) with high turnover frequency of propagation (TOF, 98 s−1) at 0 °C. The propagation rate was increased linearly against the 1‐hexene concentration, which indicates that the first‐order dependence of the propagation rate on monomer concentration. Polymerizations of 1‐octene, 1‐decene and 1‐dodecene were also conducted for investigating the effect of chain length of 1‐alkene on propagation rate by means of the livingness of this system. The propagation rate decreased according to the chain length until 1‐decene but almost unchanged in longer 1‐alkene: TOF, 1‐octene (62 s−1)>1‐decene (32 s−1) ≈ 1‐dodecene (31 s−1).
LetΩRn be a bounded domain with a smooth boundary.We consider the longtime dynamics of a class of damped wave equations with a nonlinear memory term utt+αut-△u-∫0t 0μ(t-s)|u(s)| βu(s)ds + g(u)=f.Based on a time-uniform priori estimate method,the existence of the compact global attractor is proved for this model in the phase space H10(Ω)×L2(Ω). 相似文献
Three novel scandium-containing heteropolytungstates[Sc3(H2O)3NO3(PW9O34)2]10-(1a),[Sc8(H2O)2(GeW9O34)2(GeW6O26)2]12-(2a) and[Sc11(W6O10)2(OH)2(H2O)16(BiW9O33)6]27-(3a) were synthesized by reactions of ScIII ions with trilacunary Keggin precursors,[A-α-XW9O34]n-(X=P, Ge, n=9, 10) or[B-α-BiW9O33]9-, in NaOAc/HOAc buffer solution under conventional synthetic condition, respectively. All the three compounds were characterized by means of single-crystal X-ray diffraction(XRD), Fourier transform-infrared(FTIR) spectroscopy ultraviolet-visible(UV-Vis) spectroscopy, elemental analysis, and thermogravimetric analysis. The aqueous solution stability of the sandwich polyanion[Sc3(H2O)3NO3(PW9O34)2]10- was also verified by electrospray ionization mass spectrometry(ESI-MS) due to its good solubility in water. 相似文献
The aim of the investigation was to explore the expression patterns of VEGF and TSP2 after corneal alkali burn in vivo. After the model of corneal alkali burn was established in mice, the expression levels of VEGF and TSP2 were determined by immunohistochemistry (IHC), RT-PCR, image analysis and statistical evaluation. Compared with control group, the expression level of VEGF increased significantly at 6h after alkali burn and reached its maximum at 12h. Then, it increased again till the second peak appeared at 96h and 192h. The VEGF-positive reaction mainly gathered in the stroma of cornea. On the other hand, the expression of TSP2 enhanced at 3h and attained two peaks at 6h and 96h, respectively, with the process of wound healing. TSP2 was expressed mainly in the base of epithelial layer. The expression patterns of VEGF and TSP2 reflect the complicated interaction with many factors including promoted and inhibited vascularization in vivo. Moreover, it might provide a novel method for controlling vascular hyperplasia in future clinical work according to the data of VEGF and TSP2. 相似文献