肉桂醛催化选择加氢反应中双金属的协同效应

对既含有ＣＣ键又含有ＣＯ键的分子,ＣＣ键的选择加氢意义重大［１］．α,β不饱和醛选择加氢成饱和醛就属于此类．钯是已知的可在温和条件下将α,β不饱和醛选择加氢生成饱和醛最有效的催化剂之一．人们曾研究了不同钯化合物催化剂对α,β不饱和醛中ＣＣ的双键选择加...     

Cr bound catalytically active sol–gel siloxane polymers

Several types of Cr bound siloxane polymers were prepared by various modes of polymerization. The co-polymerization of (EtO)₃SiPhCr(CO)₃ and Si(OMe)₄ by the sol–gel process, and its subsequent curing, led to a hydrogenation reactive polymer catalyst. Its catalytic reactivity was retained throughout several cycles, contrary to siloxane polymers prepared by different methods. The hydrogenation reaction was studied with methyl sorbate, 3-nonen-2-one, and 1-octyne. Regio- and stereoselectivities were studied. Cyclohexane as solvent was found to be superior to THF in retaining the catalytic activity upon recycling of the polymeric catalyst in the hydrogenation reactions.     

固相配位化学反应研究(LXVII)─固－固相反应合成混配化合物

室温或近室温条件下,Co(acac)₂(H₂O)₂与第二配体2,2'-联吡啶、1,10-啡啰啉、8-羟基喹啉、水杨醛肟固相反应得到4个混配化合物,经XRD、IR、UV及元素分析表征了这些产物。     

抗烧结Rh-Sm_2O_3/SiO_2催化剂的制备和表征及其甲烷部分氧化制合成气性能

以乙酰丙酮铑(Rh(acac)_3)和乙酰丙酮钐(Sm(acac)_3)为前驱体,用浸渍法制备了Rh/SiO_2和Rh-Sm_2O_3/SiO_2催化剂。采用原位红外光谱、热重分析、低温N_2吸附、X射线粉末衍射、高分辨透射电子显微镜、H_2-程序升温还原和X射线光电子能谱等实验技术对催化剂的制备过程,比表面积和物相以及Rh与Sm_2O_3间的相互作用进行了表征,并以甲烷部分氧化制合成气为目标反应对催化剂的稳定性进行了考察。研究表明:以Rh(acac)_3和Sm(acac)_3为前驱体采用简单的浸渍法即可制备出Rh平均粒径为2.3 nm且具有良好抗烧结性能的Rh-Sm_2O_3/SiO_2催化剂。在浸渍过程中乙酰丙酮化合物通过与SiO_2表面羟基形成氢键而负载于载体表面。Sm(acac)_3在SiO_2表面的单层负载量(质量分数)约为31%,对应于Sm_2O_3的质量分数约为15%,只要Sm(acac)_3的质量分数低于这一阈值,均可保证分解后生成的Sm_2O_3以高分散形式负载于SiO_2上,且不会因高温(800°C)焙烧而团聚。高分散于SiO_2表面的Sm_2O_3与Rh之间存在强的相互作用,可显著提高Rh的分散度,防止其在高温反应条件下烧结,进而使低Rh负载量的催化剂表现出良好的甲烷部分氧化制合成气反应活性和稳定性。     

Self-assembly in dinuclear, cyclic homotetranuclear and cyclic heterotetranuclear complexes with a picolylhydrazone ligand

Reactions among Cu(ClO₄)₂ · 6H₂O, Cu(acac)₂/VO(acac)₂ and 3-methoxysalicylaldehyde Picoloylhydrazone in different solvents give three complexes, [Cu₂L(acac)(H₂O)₂]ClO₄ (1), [Cu₄L₂(acac)₂(py)₂](ClO₄)₂ (2) and (VO₂)₂L₂Cu₂(acac)₂ (3) (acac = acetyl acetonate and py = pyridine). There is an extended 2D structure in complex 1 constructed by hydrogen bonds between the binuclear complex cation and the ClO₄⁻ anion, and an extended 1D structure in complex 2 constructed by weak ππ stacking interactions between neighboring cyclic tetranuclear complex molecules. Complex 3 is the first oxovanadium–copper complex with a bridging oxo oxygen atom between the V atom and the Cu atom. The solid-state photoluminescent properties of the three title complexes have been studied. There is an antiferromagnetic interaction in 1.     

Cobalt phthalocyanine derivatives supported on TiO2 by sol–gel processing: Part 2. Activity in sulfide and ethanethiol oxidation

The catalytic activity of cobalt(II) 2,9,16,23-tetrasulphophthalocyanine and cobalt(II) 2,9,16,23-tetra(chlorosulphonyl)phthalocyanine covalently bonded to a TiO₂ matrix by sol–gel processing was investigated for sulfide and ethanethiol (CH₃CH₂SH) liquid-phase oxidation. A comparison of the kinetic data as well as the state of active component by using electron spectroscopy in dependence on precursors was carried out. Kinetic data shows that the most stable and active catalysts for ethanethiol oxidation are both CoPc(SO₃H)₄ and CoPc(SO₂Cl)₄ in TiO₂ from Ti(OⁱPr)₄, whereas in the case of Na₂S oxidation in neutral medium the activity of the former is higher.     

Effects of inorganic components on the structure and thermo-oxidative degradation of PMMA modified metal alkoxide–EAA complex

Poly(methyl methacrylate) (PMMA) modified titanium and zirconium n-butoxide–ethyl acetoacetate (EAA) complex [M5-Ti(OBuⁿ)₂(EAA)₂ and M5-Zr(OBuⁿ)₂(EAA)₂] were obtained from trialkoxysilane-functional PMMA and EAA modified titanium and zirconium alkoxide via the sol–gel method. Infrared (IR), ¹³C nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA) were used to analyze the structures and properties of the hybrids with various proportions of metal oxide species. The effect of the complex of metal oxides and EAA ligands on structure and thermo-oxidative degradation of the M5-Ti(OBuⁿ)₂(EAA)₂ and M5-Zr(OBuⁿ)₂(EAA)₂ hybrids were investigated in this study. The ¹H spin–diffusion path length of the hybrids was in a nanometer scale as estimated from the spin–lattice relaxation time in a rotating frame (T_1ρ^H). The apparent activation energies (E_a), evaluated by van Krevelen’s method, for random scission of PMMA segments in hybrids decreased with increasing metal oxide content.     

The ternary system H2O–Fe(NO3)3–Co(NO3)2 isotherms 0 and 15 °C

The solid–liquid equilibria of the ternary system H₂O–Fe(NO₃)₃–Co(NO₃)₂ were studied by using a synthetic method based on conductivity measurements.

Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), the iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), the cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O) and the cobalt nitrate trihydrate (Co(NO₃)₂·3H₂O).     

Liquid phase hydrogenation and hydrodenitrogenation of aromatic nitrogen-containing environmental pollutants

Carcinogenic aromatic nitro-compounds are hydrogenated at 80–140 °C in the presence of a silica sol–gel entrapped combined palladium-[Rh(cod)Cl]₂ catalyst to give hydroaromatic amines and nitrogen-free hydrocarbons. The process involves initial transformation of the nitro to an amino function. Further hydrogenation causes denitrogenation and saturation of the aromatic moieties. Using 1-aminonaphthalene as a model substrate reveals simultaneous formation of 1- and 5-aminotetralin. While the former amine is readily converted into tetralin and 1-aminodecalins, the 5-aminotetralin gives, in a slow process, only the aminodecalins. The latter compounds are slowly denitrogenated to decalins. The catalytic hydrogenation of the aromatic compounds is accompanied by NH₃ elimination by which secondary amines are formed in a reversible fashion. The entrapped catalyst is leach-proof and recyclable. However, its catalytic activity in the different steps changes during the recycling. The high activity of the combined catalyst results from synergism between the two different metal nuclei.     

“原位”红外光谱追踪反应条件下催化体系的变化

为了观察和监测反应条件下中间产物和催化剂的变化,自行设计并安装了高温高压红外流动池。池体用不锈钢制成,窗口材料为NaCl或CaF₂。它可承受100atm和200℃。整个测量系统包括高压釜、循环泵、红外池等。用Microlab-600型红外分光光度计记录图谱。池内温度和压力与反应釜桐同,可对反应液体、气体或气液混合物进行"原位"追踪。当用铑膦络合物催化剂进行丙烯氢甲酰化反应时,在近于工业反应条件下(t=10O℃,P=17atm,正丁醛溶剂),检测到催化剂母体Rh(acac)(CO)(PPh₃)转化为活性物种RhH(CO)₂(PPh₃)₂;在合成气压力较低时,只转化为RhH(CO)(PPh₃)₃;此活性物种随催化剂失活而消失。催化剂加氧失活后,检测到配位体三苯基膦氧化为氧化三苯基膦,催化剂生成二聚物,丙烯氧化成丙酮,追踪到原料气CO氧化为CO₃的动态过程。本文对"原位"红外光谱实验方法、高温高压红外池作了介绍,并给出有关实验数据和结果。     

Homo- and hetero-bridged mixed-valence dinuclear complexes which contain the fragment ‘Rh(C6F5)3’

The reaction of the anionic mononuclear rhodium complex [Rh(C₆F₅)₃Cl(Hpz)]^t- (Hpz = pyrazole, C₃H₄N₂) with methoxo or acetylacetonate complexes of Rh or Ir led to the heterodinuclear anionic compounds [(C₆F₅)₃Rh(μ-Cl)(μ-pz)M(L₂)] [M = Rh, L₂ = cyclo-octa-1,5-diene, COD (1), tetrafluorobenzobarrelene, TFB (2) or (CO)₂ (4); M = Ir, L₂ = COD (3)]. The complex [Rh(C₆F₅)₃(Hbim)]⁻ (5) has been prepared by treating [Rh(C₆F₅)₃(acac)]⁻ with H₂bim (acac = acetylacetonate; H₂bim = 2,2′-biimidazole). Complex 5 also reacts with Rh or Ir methoxo, or with Pd acetylacetonate, complexes affording the heterodinuclear complexes [(C₆F₅)₃Rh(μ-bim)M(L₂)]⁻ [M = Rh, L₂ = COD (6) or TFB (7); M = Ir, L₂ = COD (8); M = Pd, L₂ = η³-C₃H₅ (9)]. With [Rh(acac)(CO)₂], complex 5 yields the tetranuclear complex [{(C₆F₅)₃Rh(μ-bim)Rh(CO)₂}₂]₂₋. Homodinuclear Rh^III derivatives [{Rh(C₆F₅)₃}₂(μ-L)₂]^·- [L₂ = OH, pz (11); OH, S^tBu (12); OH, SPh (13); bim (14)] have been obtained by substitution of one or both hydroxo groups of the dianion [{Rh(C₆F₅)₃(μ-OH)}₂]²⁻ by the corresponding ligands. The reaction of [Rh(C₆F₅)₃(Et₂O)_x] with [PdX₂(COD)] produces neutral heterodinuclear compounds [(C₆F₅)₃Rh(μ-X)₂Pd(COD)] [X = Cl (15); Br (16)]. The anionic complexes 1–14 have been isolated as the benzyltriphenylphosphonium (PBzPh₃⁺) salts.     

Practical dihydroxylation and C–C cleavage of unsaturated fatty acids

Unsaturated fatty acids [C₈H₁₇CH=CH(CH₂)_nCO₂H] (n=7, 11) acids are cleanly dihydroxylated by hydrogen peroxide in the presence of catalytic amounts of H₂WO₄. Under molecular oxygen, in the presence of catalytic amounts of N-hydroxyphthalimide and Co(acac)₃, the diols resulting from erucic (n=11) and oleic (n=7) acid undergo C–C cleavage.     

M/(MgO)y(CeO2)1－y(M=Ni、Co、Cu)催化剂的催化甲烷燃烧性能

采用溶胶凝胶法制备了M/(MgO)_y(CeO2)_1－y(M=Ni、Co、Cu)催化剂. 研究了催化剂Ni/(MgO)y(CeO₂)_1－y催化活性与Ce含量的关系, 当y＝0.9时, 催化剂的活性和稳定性最好. 对比研究了(MgO)_0.9(CeO2)_0.1为载体, 负载Ni、Co、Cu活性组分的催化剂催化甲烷燃烧性能. 结果表明, 负载Cu的催化剂活性最好, 但二次评价后催化剂已烧结；负载Ni的催化剂活性与负载Cu的催化剂相差不大, 且稳定性最好, 经1000 ℃焙烧的Ni/(MgO)_0.9(CeO2)_0.1催化剂比表面仍有14.32 m₂•g^－1, 具有较高的催化活性和很好的热稳定性；负载Co的催化剂活性不如前两者, 稳定性居中, 但比表面降低得最少, 抗烧结能力强.     

TPR/TPO characterization of cobalt–silicon mixed oxide nanocomposites prepared by sol–gel

Cobalt–silicon mixed oxides with Co/Si ratio of 10/90 (10Co), 20/80 (20Co) and 30/70 (30Co) were prepared by a modified sol–gel method. The materials treated in air at 400 and 600 °C were characterized by SEM and TPR/TPO techniques. TPR measurements showed that in all samples only a fraction of Co was present as Co₃O₄ and as amorphous silicate and was reducible by H₂ within 800 °C, while a part was not reducible under TPR conditions. The fraction of Co not reducible decreased with increasing Co content. A TPO/TPR cycle gave rise to an increase of the fraction of not reducible Co.     

Photocatalytic degradation and kinetics of Orange G using nano-sized Sn(IV)/TiO2/AC photocatalyst

Sn(IV) doped and nano-sized TiO₂ immobilized on active carbon (AC) (Sn(IV)/TiO₂/AC) were prepared by the sol–gel and dip-calcination method. An azo dye, Orange G (OG), was used as a model compound to study its photocatalytic activity in a fluidized bed photoreactor. The addition of Sn(IV) on TiO₂ could greatly improve the activity of TiO₂, and the optimal amount of tin was 2.5 at.%. The effects of calcination temperature, pH value, the initial hydrogen peroxide concentration ([H₂O₂]₀), the catalyst amount ([TiO₂]), the initial OG concentration ([dye]₀) and co-existing negative ions on the photocatalytic activity of Sn(IV)/TiO₂/AC were studied. The optimal conditions were as follows: pH 2.00, [H₂O₂]₀ = 1.5mL/L, [dye]₀ = 50 mg/L, [TiO₂] = 12.5 g/L, when the 300 W high pressure mercury light was used as the light source. Under these conditions, the degradation efficiency of OG reached 99.1% after 60 min reaction. The kinetics of the OG degradation was also analyzed. The results showed that the kinetics of this reaction fit the Langmiur–Hinshelwood kinetics model well and the absorption of OG on the Sn(IV)/TiO₂/AC surface was the controlling step in the whole degradation process. In addition, the catalyst, liquid and gas were separated effectively, and the integrative process of reaction and separation was achieved during the experiment.     

Development of an analytical method for beryllium in airborne dust by micellar electrokinetic chromatography

The separation of diacetylacetonato–beryllium [Be(acac)₂] from acetylacetone was achieved with micellar electrokinetic chromatography (MEKC) followed by subsequent beryllium analysis carried out using capillary electrophoresis. Analysis using a separation and absorption detector, with a 50 μm capillary cell, could detect approximately 1000 ppb of beryllium in the final sample. Be(acac)₂ is a promising reagent for absorption spectrophotometry, because its molar absorption coefficient, (32 000 l mol⁻¹ cm⁻¹) is very large. As the complex and acetylacetone have a similar absorption wavelength, the excess free ligand must removed from the sample to be measured. Acetylacetone is a weak acid with keto–enol tautomerism in aqueous solution. Acetylacetone and neutral Be(acac)₂ should be separated with capillary zone electrophoresis (CZE) using a neutral or basic buffer solution as the mobile phase. Although the pH and temperature of the mobile phase were optimized, separation with CZE was interfered with by a portion of acetylacetone. This interfering portion seems to be a neutral keto-form with the same migration time as Be(acac)₂. As a neutral species separation method, MEKC with sodium dodecyl sulfate was tried and the separation was completed. The optimum pH value and buffer temperature are pH 7.8 and 15°C, respectively.     

Preparation and characterization of a supported Si3N4 membrane via a non-aqueous sol–gel process

We report a novel fabrication process of a mesoporous Si₃N₄ membrane on an Al₂O₃ support via a non-aqueous sol–gel technique. The membrane was prepared by dipping an -Al₂O₃ support disk into a silicon diimide sol that was synthesized by catalytic ammonolysis of tris(dimethylamino)silylamine, H₂NSi(NMe₂)₃. The SEM image and nitrogen adsorption analysis indicate that amorphous Si₃N₄ layers with nano-sized pores have formed on the surface and also inside the pores of the Al₂O₃ support disk. The new membrane demonstrates high selective absorption of NO₂, suggesting a potential application as a selective filter for gas sensors.     

UV stabilizers bonded to transition metals: Synthesis and X-ray structure of 2-(2′-hydroxyphenyl)benzotriazole-oxovanadium(IV) and -dioxomolybdenum(VI) complexes

The UV-stabilizer 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (Tinuvin P, LH) has been used as a monoanionic bidentate ligand for complexing oxocations. Displacement of acacH from [VO(acac)₂] and [MoO₂(acac)₂] gave [*VO(acac)₂*(μ-L)] (2) and [cis-O₂Mo(acac)L] (3) respectively, as crystalline compounds. Their structure has been determined by an X-ray analysis showing the structural changes occurring upon coordination. The UV spectrum of Tinuvin P is significantly affected by complexation.     

Supported transition-metal catalysts for the C---C coupling reaction between ethene and diazoalkanes

The preparation of a series of immobilized transition-metal catalysts are reported. The catalysts were obtained by chemisorption of either rhodium(I) or iridium(I) complexes [MX(C₂H₄)₂]_n (M = Rh, Ir; X = Cl, OAc, acac, f₃-acac, f₆-acac) on SiO₂ or MgO supports. The oxides were also activated by SiCl₄ or TiCl₄ to give support materials in which the acidic nature of the surface is substantially increased. The activity of the immobilized catalysts was tested, particularly in the reaction of ethene with diphenyldiazomethane which yields a mixture of 1.1-diphenylpropene (8) and 1.1-diphenylcyclopropane (9). It was found that the most active and most selective (highest ratio 8:9) catalyst B1 was formed support material B (SiO₂ activated by SiCl₄) and [RhCl(C₂H₄)₂]₂ (1) and that both the activity and selectivity of B1 was comparable with that of complex 1 in solution. In contrast, the supported catalysts A2, D2 and A3, D3 obtained from [Rh(OAc)(C₂H₄)₂]₂ (2) and [Rh(acac)(C₂H₄)₂] (3) were less active than compounds 2 and 3 in solution. The immobilized catalysts A6, A7, D7 and E7, which were generated from the chloro- and acetatoiridium(I) complexes [IrCl(C₂H₄)₂]₂ (6) and [Ir(OAc)(C₂H₄)₂]₂ (7), possessed a lower activity than the rhodium counterparts. With diazoalkanes other than Ph₂CN₂, the activity of the supported catalyst B1 was partly higher and partly lower than that of complex 1 in the homogeneous phase.     

Copper(II), nickel(II) and cobalt(II) complexes of 4-cyanobenzonic acid: syntheses, crystal structures and spectral properties

Three new metal complexes, Cu(4-Hcba)₂(4-cba)₂(Py)₂ (4-Hcba=4-cyanobenzoic acid) 1 and M[H(4-cba)₂]₂(Py)₂ (M=Ni 2, Co 3), have been prepared by the treatment of 4-Hcba with the respective metal nitrate M(NO₃)₂ (M=Cu, Ni, Co) in the presence of pyridine (Py). Single-crystal X-ray diffraction analyses (3 is isostructural to 2) show that the obtained complexes are of isolated mononuclear and the metal atoms have distorted octahedral coordination environment. Two different types of intramolecular hydrogen bonds exist: asymmetrical O–HO for 1 and symmetrical OHO for 2 and 3. The crystal packing between the molecular complexes is controlled mainly by T-shaped C–Hπ interactions between pyridine and phenyl rings. Preliminary discussions on IR, UV–VIS and fluorescent spectra have also been carried out.