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101.
102.
锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响 总被引:3,自引:2,他引:3
考察了含锆的铜铬硅催化剂低温液相合成甲醇性能,并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明,锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用,反应活性可提高32.25 %。锆助剂能有效提高催化剂的比表面积,促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关,Zr4+、Cr3+、Cu+可形成复合中心,为价态的稳定性提供微环境,在H2活化及C O键的断裂等反应步骤中起重要作用。 相似文献
103.
IntroductionItiswellknownthatmetallocenesactivatedwithmethylaluminoxane (MAO)arehighlyactivehomogeneousZiegler Nattacatalyststhatproducepolyolefinwithcon trolledstereoregularityandnarrowmolecularweightdistri bution ,1 4 however,themolecularweightofthepolym… 相似文献
104.
Eight tris(organotin)-substituted Keggin tungstosilicate heteropolyanions have been synthesized and characterized by elemental analysis, infrared and M?ssbauer spectroscopy, multinuclear NMR, and X-ray crystallography. The new anions contain alpha- or beta-SiW(9)O(34)(10)(-) moieties and are of two structural types, [(RSn)(3)(SiW(9)O(37))](7)(-) (R, isomer: Ph, alpha-, 1; n-Bu, alpha-, 2; Ph, beta-, 3; n-Bu, beta-, 4) and [(RSnOH)(3)(SiW(9)O(34))(2)](14)(-) (Ph, alpha-, 5; n-Bu, alpha-, 6; Ph, beta-, 7; n-Bu, beta-, 8). Crystals of Cs(4)H(3)[(PhSn)(3)(SiW(9)O(37))].8H(2)O (anion 3) are monoclinic, space group C2/c, with lattice constants a = 48.91(2) ?, b = 12.111(3) ?, c = 20.334(9) ?, beta = 102.30 degrees, and Z = 8. The anion has nominal C(3)(v)() symmetry and has a structure with three corner-shared WO(6) octahedra of the beta-Keggin anion replaced by three PhSnO(5) groups. Crystals of Cs(9)H(5)[(BuSnOH)(3)(SiW(9)O(34))(2)].36H(2)O (anion 6) are tetragonal, space group P&fourmacr;2(1)m, with lattice constants a = b = 29.005(4) ?, c = 13.412(4) ?, and Z = 4. The anion has the anticipated D(3)(h)() symmetry and contains three BuSnOH groups sandwiched between A,alpha-SiW(9)O(34)(10)(-) anions. 相似文献
105.
106.
Fu A Huang X Li J Yuen T Lin CL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(10):2239-2247
Controlled synthesis of transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N3)2(4,4'-bpy)] (4,4'-bpy=4,4'- bipyridine). The compound 2D-[Fe(N3)2(4,4'-bpy)] (I) contains end-on (EO) bridging azido ligands. It crystallizes in the orthorhombic crystal system, space group Cmmm (No. 65): a=11.444(2) A, b=15.181(3) A, c=3.458(1) A, V=600.8(2) A(3), and Z=2. The compound 3D-[Fe(N3)2(4,4'-bpy)] (II) contains end-to-end (EE) azido bridges. It belongs to the tetragonal crystal system, space group P4(1)2(1)2 (No. 92): a=8.132(1) A, b=8.132(1) A, c=16.708(3) A, V=1104.9(5) A(3), and Z=4. Crystals of I and II have been grown by the diffusion method. Phase-pure samples of both compounds have been obtained by means of an optimal solution synthesis. Spontaneous long-range magnetic ordering was found in both I and II, with I being a metamagnet, and II being a ferromagnet. For I, in the low-field region, multiple transitions at TN1=20 K and TN2=5 K were observed, and these indicated the existence of Fe moment reorientation. Heat capacity measurements on II confirmed ferromagnetic transition at TC=20 K. 相似文献
107.
Long JW Logan MS Rhodes CP Carpenter EE Stroud RM Rolison DR 《Journal of the American Chemical Society》2004,126(51):16879-16889
We have developed crystalline nanoarchitectures of iron oxide that exhibit superparamagnetic behavior while still retaining the desirable bicontinuous pore-solid networks and monolithic nature of an aerogel. Iron oxide aerogels are initially produced in an X-ray-amorphous, high-surface-area form, by adapting recently established sol-gel methods using Fe(III) salts and epoxide-based proton scavengers. Controlled temperature/atmosphere treatments convert the as-prepared iron oxide aerogels into nanocrystalline forms with the inverse spinel structure. As a function of the bathing gas, treatment temperature, and treatment history, these nanocrystalline forms can be reversibly tuned to predominantly exhibit either Fe(3)O(4) (magnetite) or gamma-Fe(2)O(3) (maghemite) phases, as verified by electron microscopy, X-ray and electron diffraction, microprobe Raman spectroscopy, and magnetic analysis. Peak deconvolution of the Raman-active Fe-O bands yields valuable information on the local structure and vacancy content of the various aerogel forms, and facilitates the differentiation of Fe(3)O(4) and gamma-Fe(2)O(3) components, which are difficult to assign using only diffraction methods. These nanocrystalline, magnetic forms retain the inherent characteristics of aerogels, including high surface area (>140 m(2) g(-1)), through-connected porosity concentrated in the mesopore size range (2-50 nm), and nanoscale particle sizes (7-18 nm). On the basis of this synthetic and processing protocol, we produce multifunctional nanostructured materials with effective control of the pore-solid architecture, the nanocrystalline phase, and subsequent magnetic properties. 相似文献
108.
Hydrogen storage in the dehydrated prussian blue analogues M3[Co(CN)6]2 (M = Mn, Fe, Co, Ni, Cu, Zn)
The porosity and hydrogen storage properties for the dehydrated Prussian blue analogues M3[Co(CN)6]2 (M = Mn, Fe, Co, Ni, Cu, Zn) are reported. Argon sorption isotherms measured at 87 K afford BET surface areas ranging from 560 m2/g for Ni3[Co(CN)6]2 to 870 m2/g for Mn3[Co(CN)6]2; the latter value is comparable to the highest surface area reported for any known zeolite. All six compounds show significant hydrogen sorption at 77 K and 890 Torr, varying from 1.4 wt % and 0.018 kg H2/L for Zn3[Co(CN)6]2 to 1.8 wt % and 0.025 kg H2/L for Cu3[Co(CN)6]2. Fits to the sorption data employing the Langmuir-Freundlich equation give maximum uptake quantities, resulting in a predicted storage capacity of 2.1 wt % and 0.029 kg H2/L for Cu3[Co(CN)6]2 at saturation. Enthalpies of adsorption for the frameworks were calculated from hydrogen isotherms measured at 77 and 87 K and found to increase with M varying in the order Mn < Zn < Fe < Co < Cu < Ni. In all cases, the binding enthalpies, which lie in the range of 5.3-7.4 kJ/mol, are higher than the 4.7-5.2 kJ/mol measured for Zn4O(1,4-benzenedicarboxylate)3. 相似文献
109.
Jeremy R. Lizotte Brian M. Erwin Ralph H. Colby Timothy E. Long 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):583-590
The feasibility of utilizing stable free‐radical polymerization (SFRP) in the synthesis of well‐defined poly(2‐vinylnaphthalene) homopolymers has been investigated. Efforts to control molecular weight by manipulating initiator concentration while maintaining a 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO):benzoyl peroxide (BPO) molar ratio of 1.2:1 proved unsuccessful. In addition, systematic variations of the TEMPO: BPO molar ratio did not result in narrow molecular weight distributions. In situ Fourier transform infrared spectroscopy (FTIR) indicated that the rate of monomer disappearance under SFRP and thermal conditions were identical. This observation indicated a lack of control in the presence of the stable free radical, TEMPO. The similarities in chemical structure between styrene and 2‐vinylnaphthalene suggested thermally initiated polymerization occurred via the Mayo mechanism. A kinetic analysis of the thermal polymerization of styrene and 2‐vinylnaphthalene suggested that the additional fused ring in 2‐vinylnaphthalene increased the propensity for thermal polymerization. The observed rate constant for thermal polymerization of 2‐vinylnaphthalene was determined using in situ FTIR spectroscopy and was one order of magnitude greater than styrene, assuming pseudo‐first‐order kinetics. Also, an Arrhenius analysis indicated that the activation energy for the thermal polymerization of 2‐vinylnaphthalene was 30 kJ/mol less than styrene. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 583–590, 2002; DOI 10.1002/pola.10131 相似文献
110.