Cyclohexene Selectivity Research Articles

Ternary modified TiO2 as a simple and efficient photocatalyst for green organic synthesis

TiO2 ternary-modified with Fe(3+), Ni(2+), and Au nanoparticles exhibited a noticeable photocatalytic activity for selective cyclohexane oxidation with O2 under sunlight irradiation.

Characterization and catalytic properties of Ni and NiCu catalysts supported on ZrO2–SiO2 for guaiacol hydrodeoxygenation

ZrO 2 –SiO 2 complex oxides with Si/Zr mole ratio of 3 (SZ-3) were synthesized. ZrO 2 –SiO 2 supported Ni and NiCu catalysts were prepared by impregnation method. Their catalytic performances were evaluated in the hydrodeoxygenation (HDO) upgrading of model reactant guaiacol to hydrocarbons. The physicochemical properties of the support materials and catalysts were characterized by FTIR, XRD, TPD, TPR, and BET techniques. The addition of Cu significantly affected the acidity, and thus influenced their catalytic performance for product distributions. Over the Ni5Cu/SZ-3 catalyst, the cyclohexane selectivity of 80.8% and the methylcyclohexane selectivity of 12.4% were obtained with complete conversion of guaiacol under the 300 °C, 5.0 MPa H 2 pressure. Over SiO 2 –ZrO 2 supported NiCu catalysts, guaiacol was effectively converted to cyclohexane and methyl-cyclohexane through HDO reaction. ► ZrO 2 –SiO 2 mixed oxides possess amphoteric character and excellent textural properties. ► NiCu/ZrO 2 –SiO 2 catalyst possesses high catalytic activity for guaiacol HDO. ► Cu could lower the reduction temperature of NiO, and fortify the acidity of catalyst. ► The metallic and acidic functionalities of catalyst exhibit synergistic effect on guaiacol HDO.

Effect of (Zn(OH)2)3(ZnSO4)(H2O)5 on the performance of Ru–Zn catalyst for benzene selective hydrogenation to cyclohexene

A series of Ru–Zn catalysts with different Zn contents were prepared by co-precipitation. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) – Ar+ sputter, transmission electron micrographs (TEM)–energy dispersion scanning (EDS) and temperature-programmed reduction (TPR). The performances of the catalysts for benzene selective hydrogenation to cyclohexene were investigated in the presence of 0.6mol/L of ZnSO4. The results showed that the Ru and Zn in Ru–Zn catalyst were in metallic Ru and ZnO respectively and the ZnO was rich on the surface. The ZnO alone could not improve the selectivity to cyclohexene of Ru–Zn catalyst. However, the ZnO on the surface could react with ZnSO4 to form a (Zn(OH)2)3(ZnSO4)(H2O)5 salt. The (Zn(OH)2)3(ZnSO4)(H2O)5 salt chemisorbed played a key role in improving the selectivity to cyclohexene of Ru–Zn catalysts. After Ru–Zn(8.6%) catalyst was pretreated 22h in ZnSO4 solution at 140°C and 5MPa H2, a cyclohexene selectivity of 81.4% at a benzene conversion of 54.0% was achieved at 10min and a maximum cyclohexene yield of 58.9% was reached. Moreover, the activity was stable above 50% and the cyclohexene selectivity and yield were steadily above 76% and 40% on this catalyst in the first six recycles, respectively.

Preparation of Ru-[bmim]BF4 Catalyst Using NaBH4 as Reducing Agent and Its Performance in Selective Hydrogenation of Benzene

A Ru-[bmim]BF 4 catalyst was prepared in a mixture of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ) and H 2 O using NaBH 4 as a reducing agent. The Ru-[bmim]BF 4 catalyst showed higher selectivity for cyclohexene than a catalyst reduced by N 2 H 4 ·H 2 O because of the influence of boron. When Ru-[bmim]BF 4 was reused, higher activity and lower selectivity were obtained because the number of Ru active sites increased through leaching of the ionic liquid. The used catalyst also contained ZnOHF formed in the reaction between F − and ZnSO 4 , which was an additive in the reaction. Under the influence of the ionic liquid as a template, ZnOHF grew along the (001) direction and exhibited rod-like morphology. 在离子液体 1-丁基-3-甲基咪唑四氟硼酸盐 ([bmim]BF 4 )-水混合介质中, 以 NaBH 4 为还原剂制备了 Ru-[bmim]BF 4 催化剂, 并用于苯选择加氢反应. 结果表明, 相对于 N 2 H 4 ·H 2 O 还原制备的催化剂, 本催化剂具有明显较高的环己烯选择性, 当苯转化率为 49.5% 时, 环己烯选择性可达 34.1%, 这是由于硼的作用所致. 重复使用时, 由于离子液体的流失, 暴露的 Ru 活性中心增多, 因而苯转化率升高, 但环己烯选择性下降, 同时生成了 ZnOHF. 这是离子液体中 F – 与 ZnSO 4 反应而得; 并且在离子液体的模板作用下, ZnOHF 沿着 (001) 方向生长, 从而形成了一维棒状形貌. Ru-[bmim]BF 4 shows higher selectivity for cyclohexene in the hydrogenation of benzene when NaBH 4 is used as a reductant because of the significant effect of boron.

Effect of Support Acidity on Liquid-Phase Hydrogenation of Benzene to Cyclohexene over Ru–B/ZrO2Catalysts

Ru–B/ZrO2 catalysts using monoclinic, amorphous, and tetragonal ZrO2 as supports were prepared and used for liquid-phase hydrogenation of benzene to cyclohexene. It is identified that both the Lewis acid sites and the Brønsted acid sites existed on monoclinic ZrO2 (ZrO2-M), while there were only Lewis acid sites on amorphous (ZrO2-A) and tetragonal ZrO2 (ZrO2-T). The amount of acid sites on ZrO2-T was the lowest. In liquid-phase hydrogenation of benzene to cyclohexene, the Ru–B/ZrO2-T catalyst exhibited the highest selectivity and yield of cyclohexene, with the maximum yield of cyclohexene being 47%. These results suggest that for ZrO2-supported Ru–B catalysts, the lower was the amount of acid sites on ZrO2, the higher was the selectivity to cyclohexene. Also, the presence of the Brønsted acid sites on ZrO2 is probably adverse to the selectivity toward cyclohexene.

Ru–Cd/Bentonite for the Partial Hydrogenation of Benzene: A Catalyst without Additives

AbstractClays are very promising, environmentally benign catalyst supports. Herein, Ru–Cd/bentonite (BEN) catalysts were prepared and characterized by TEM, SEM, XPS, and XRD. The as‐prepared catalysts were used to catalyze the selective hydrogenation of benzene into cyclohexene with different Ru/Cd molar ratios, hydrogen pressures, and reaction temperatures. We found that the catalytic activity decreased with decreasing Ru/Cd molar ratio, whereas the selectivity was enhanced. The most‐favorable Ru/Cd molar ratio was 1 and the optimal hydrogen pressure and temperature were 5 MPa and 150 °C, respectively. The yield of cyclohexene reached 24.8 % over Ru–Cd/BEN under the optimal reaction conditions without the need for any additives in the reaction system and this catalyst could be reused several times in the reaction without a drop in the yield of cyclohexene. The Cd in the catalyst enhanced the selectivity for cyclohexene. Furthermore, Cd/BEN could be used an as effective supported additive to promote the hydrogenation of benzene into cyclohexene catalyzed by Ru/BEN or Ru/SBA‐15.

Selective Hydrogenation of Benzene to Cyclohexene over a Ru-Zn catalyst with Diethanolamine as an Additive

A Ru-Zn catalyst was prepared by co-precipitation, and the effect of adding diethanolamine on benzene selective hydrogenation to cyclohexene was investigated. The catalyst was characterized by N 2 physisorption, transmission electron microscopy, X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and temperature-programmed reduction. Diethanolamine reacted with ZnSO 4 in the slurry to form (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 and diethanolamine sulfate. The amount of (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 adsorbed on the catalyst surface increased with increasing diethanolamine amount. The synergism of (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 and diethanolamine sulfate improved the cyclohexene selectivity of the Ru-Zn(4.9%) catalyst. With a diethanolamine dosage of 0.3 g, (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 was highly dispersed on catalyst surface and the sample after hydrogenation was characterized. This catalyst exhibited the best performance with a cyclohexene selectivity and yield of 75.5% and 63.6%, respectively, at the benzene conversion of 84.3% in the third run. Moreover, the benzene conversion and cyclohexene selectivity were stable above 75% and cyclohexene yield was above 58% in the fourth run. 采用共沉淀法制备了 Ru-Zn 催化剂, 考察了二乙醇胺的添加对 Ru-Zn 催化剂上苯选择加氢制环己烯性能的影响, 并采用 N 2 物理吸附、透射电镜、X 射线衍射、X 射线荧光、傅里叶变换红外和程序升温还原等手段对催化剂进行了表征. 结果表明, 二乙醇胺可以与浆液中 ZnSO 4 反应生成 (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 和硫酸二乙醇胺盐. 随着二乙醇胺用量的增加, 化学吸附在催化剂表面的 (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 增多, 它与硫酸二乙醇胺盐的协同作用提高了 Ru-Zn(4.9%) 催化剂上苯选择加氢生成环己烯的选择性. 当二乙醇胺用量为 0.3 g 时, (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 在 Ru-Zn(4.9%) 催化剂加氢后样品的表面高度分散, 反应性能最佳, 循环使用第 3 次时苯转化率为 84.3%, 环己烯选择性和收率分别达 75.5% 和 63.6%; 使用至第 4 次时, 反应 25 min 时苯转化率和环己烯选择性仍可达 75% 以上, 环己烯收率为 58% 以上. With a diethanolamine dosage of 0.3 g, (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 was promoted to be highly dispersed on a Ru-Zn(4.9%) catalyst and ZrO 2 particles, and this gave a cyclohexene selectivity and yield of 75.5% and 63.6%, respectively, at the benzene conversion of 84.3%.

Cellulose Benzoyl Ester with Different Substitution Degree Supported Ru Nano-clusters Catalyst for Benzene Hydrogenation

Cellulose benzoyl ester (CB) was synthesized from cellulose and benzoyl chloride. Different substitution degree CBs were obtained by controlling the amount of benzoyl chloride, and the resulting CBs have different swelling degree in benzene, cyclohexene and cyclohexane. Hybrid membrane, which was used for the selective hydrogenation, was prepared by supporting Ru nano-clusters (obtained by refluxing reduction of RuCl3 with n-butyl alcohol) into CB. CBs and the hybrid membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscope (TEM), etc. Research results demonstrated that swelling behavior acts as a crucial factor to the selectivity of cyclohexene. Active evaluation results indicated that the conversion of benzene (highest, 2.8%) increased while the selectivity of cyclohexene (highest, 53.4%) decreased with the increasing of CBs substitution degree.

Preparation of Nano-Ru/[Bmim][BF4] Catalyst and its Application in the Benzene Selective Hydrogenation

The nano-Ru/[Bmim][BF4] catalyst was prepared for benzene selective hydrogenation in 1-n-butyl-3- methylimidazolium tetrafluoroborate [Bmim][BF4] by chemical reduction method. TEM analysis of these nanoparticles sho wed the monodisperse Ru0 particles which were prepared by positive dropping method dispersed in the ionic liquids with diameters less than 5nm. The Ru0 particles which were prepared by reverse dropping method agglomerated with diameters more than 10nm. KBH4 was the suitable reductant. The optimum loading of Ru was 1.5%. The hydrogenation activity of Ru/ [Bmim] [BF4] was high and the selectivity of cyclohexene was very low. Selectivity of cyclohexene was only 14.5% at 27.3 % benzene conversion.

Partial hydrogenation of benzene catalyzed by Pt/N‐n‐propyl chitosan hybrid membrane

AbstractThe partial hydrogenation of benzene by a Pt nano‐cluster/N‐n‐propyl chitosan hybrid membrane was investigated in this article. Monodispersed Pt nano‐clusters were prepared by the reduction of H2PtCl6 with ethylene glycol under microwave conditions. TEM, FTIR, XRD, 1H‐NMR, and XPS were used to characterize the structure of Pt nano‐particles, N‐n‐propyl chitosan and Pt/N‐n‐propyl chitosan hybrid membrane, respectively. Experimental results showed that Pt/N‐n‐propyl chitosan hybrid membrane catalyst gave a high selectivity for cyclohexene of 85.2% in the liquid phase hydrogenation of benzene, while the selectivity of cyclohexene was only 58.2% over the Pt/chitosan hybrid membrane catalyst. It was worth noting that there was no cyclohexene in the product when the catalyst was only Pt nano‐particles without chitosan hybrid membrane. So the chitosan or modified‐chitosan membranes played an important role in the controlling to the hydrogenation of benzene, and the relationship of the swelling degree and the catalytic activity was discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Oxidative Dehydrogenation of Cyclohexane over Mg-V-O Catalysts Prepared via Citriate Complexation

Oxidative dehydrogenation of cyclohexane was studied over three pure Mg-V-O catalysts, which are Mg3(VO4)2, Mg2V2O7 and MgV2O6, respectively. Catalysts were prepared via citric acid complexation and characterized by N2-adsorption, XRD, FT-IR, NH3-TPD and H2-TPR techniques. Among the pure magnesium vanadates, Mg3(VO4)2 has the isolated active sites, weakly basic surface and lower reducibility of the metal cations, and could be recognized as the catalytic active phase. Mg3(VO4)2 catalyst exhibited a better catalytic performance, on which a cyclohexene selectivity of 41.5% at cyclohexane conversion of 15.5% was obtained.

Single‐Step Synthesis of Ruthenium Catalytic Nanocrystallites in a Stable Carbon Support

AbstractMetallic Ru nanoparticles have been prepared and incorporated in a protective carbon support by the decomposition of a single organometallic precursor, RuIII acetylacetonate, under autogenic conditions in a single‐step process in the absence of any solvents or stabilizers. The product structure was confirmed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, scanning transmission electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. Measurements demonstrated the exclusive presence of hexagonal metallic ruthenium nanoparticles with a homogeneous size of 2–4 nm in a carbon supporting matrix, forming a high loading Ru catalyst with a muffin cookie like structure. The mechanism of the process is explained by the nucleation of Ru crystalline nuclei before carbon deposits on the Ru nanocrystallites, in an early stage of nanoparticle growth, during the single precursor decomposition. The carbon acts as a protective support, preventing further Ru nanoparticle growth, agglomeration or sintering. The catalytic properties have been tested by the hydrogenation of benzene to cyclohexane, and show high activity, full conversion of benzene, 100 % selectivity for cyclohexane and good recyclability.

Pervaporation for separating benzene/cyclohexane mixture by P(AA-MA) copolymer membranes

P(AA-MA) copolymers composed of acrylic acid and methyl acrylate with different molecular weights and sequence structures were synthesized by combination of ATRP and selective hydrolysis. These copolymers were used as membrane materials to separate benzene/cyclohexane mixture by pervaporation. The effects of molecular weight and sequence structure of the copolymers on the pervaporation performance were investigated in detail. For the random copolymers, the permeate flux decreased rapidly with the increasing of molecular weight. The separation factor was also influenced by the molecular weight, which was changed from no selectivity to cyclohexane selectivity with increasing the molecular weight. Contrarily, the block copolymer membrane showed good benzene selectivity with separation factor of 4.3 and permeate flux of 157 g/(m2h) to 50 wt% benzene/cyclohexane mixture.

Pentacoordinated copper–sparteine complexes with chelating nitrite or nitrate ligand: Synthesis and catalytic aspects

Copper(II)–sparteine complexes, [CuII{(-)Sp}(NO2)Cl] (1) and [CuII{(−)Sp}(NO3)Cl] (2) (Sp=sparteine) with chelating nitrite and nitrate ligands, respectively, have been synthesized and structurally characterized. The penta-coordinated 1 or 2 exhibits distorted square pyramidal geometry and shows characteristic EPR spectra with g||: 2.27 and g⊥: 2.06. 1 and 2 behave similarly towards the catalytic epoxidation of alkenes as well as oxidation of alcohols. Though the epoxidation of cyclohexene using 1 or 2 as a catalyst and tertiarybutyl hydroperoxide (TBHP) as an oxidant at 298K in acetonitrile results in 100% cyclohexene oxide product, under identical reaction conditions styrene selectively transforms to benzaldehyde (∼90%) instead of any styrene oxide. However, at higher temperature (353K) the selectivity of cyclohexene to corresponding epoxide formation decreases appreciably and additional products, cyclohexanol and cyclohexanone are formed. Furthermore, 1 or 2 effectively catalyzes the oxidation of benzyl alcohol to benzoic acid and cyclohexanol to cyclohexanone in presence of molecular oxygen (O2) as an oxidant at 353K in acetonitrile.

Effect of Organic Additives on the Performance of Nano‐sized Ru‐Zn Catalyst

AbstractA novel Ru‐Zn catalyst was prepared by coprecipitation. The catalyst was characterized by XRF, XRD and TEM. The effects of organic additives on the performance of the Ru‐Zn catalyst for benzene selective hydrogenation to cyclohexene were investigated. The results showed that the catalyst was composed of Ru and Zn in molar ratio of 33.8:1, and the most probable value of the Ru crystallite size in the catalyst was 5.1 nm. The modification of Ru with Zn and the small size effect were the main cause why the catalyst exhibited the high activity and the excellent cyclohexene selectivity. When PEG (polyethylene glycol) was used as an additive, the activity of the catalyst decreased, and the cyclohexene selectivity increased with the increase of the PEG molecular weight. With the addition of PEG‐20000, a cyclohexene selectivity of 78.9% at a benzene conversion of 68.7% and a maximum cyclohexene yield of 61.4% were obtained. With diethanolamine and triethanolamine as additives, cyclohexene yields were as high as 58.9% and 58.2%, respectively.

Monolayer Dispersed Ru-Zn Catalyst and Its Performance in the Selective Hydrogenation of Benzene to Cyclohexene

A series of Ru-Zn catalysts with different Zn loadings were prepared by co-precipitation. X-ray diffraction and X-ray photoelectron spectroscopy results showed that a large part of the Zn in the Ru-Zn catalysts were present in the form of ZnO and the ZnO on the catalyst surface could react with ZnSO4 in the slurry to form a basic zinc sulfate salt during hydrogenation. The content of the basic salt increased with an increase in the Zn loading of the catalysts. This resulted in a decrease in catalyst activity and an increase in selectivity for cyclohexene. When the Zn loading was 8.6%, the basic salt dispersion was close to monolayer dispersion on the catalyst surface. When the catalysts were pretreated in the presence of 0.6 mol/L ZnSO4 solution at 140 °C and at 5 MPa H2, a cyclohexene selectivity of 69.8% and a benzene conversion of 84.4% was achieved after 20 min. ：采用共沉淀法制备了一系列不同 Zn 负载量的 Ru-Zn 催化剂. XRD 和 XPS 结果表明, 催化剂中的 Zn 大部分以 ZnO 形式存在, 在加氢过程中催化剂表面的 ZnO 可以与浆液中的 Zn2+形成碱式硫酸锌盐. 随催化剂中 Zn 负载量的增加, 碱式硫酸锌盐的量也增加, 这导致催化剂活性降低和环己烯选择性升高. 当 Zn 负载量为 8.6% 时, 加氢后碱式硫酸锌盐在 Ru-Zn 催化剂表面上接近单层分散态. 单层分散型 Ru-Zn 催化剂催化性能最佳, 该催化剂在 140 °C, 5 MPa H2 下和 0.6 mol/L 硫酸锌溶液中预处理 22 h 后, 反应 20 min, 苯转化率 84.4% 时, 环己烯选择性为 69.8%.

Nickel(ii) complexes of tripodal 4N ligands as catalysts for alkane oxidation using m-CPBA as oxidant: ligand stereoelectronic effects on catalysis

Several mononuclear Ni(II) complexes of the type [Ni(L)(CH(3)CN)(2)](BPh(4))(2) 1-7, where L is a tetradentate tripodal 4N ligand such as N,N-dimethyl-N',N'-bis(pyrid-2-ylmethyl)ethane-1,2-diamine (L1), N,N-diethyl-N',N'-bis(pyrid-2-ylmethyl)ethane-1,2-diamine (L2), N,N-dimethyl-N'-(1-methyl-1H-imidazol-2-ylmethyl)-N'-(pyrid-2-ylmethyl)ethane-1,2-diamine (L3), N,N-dimethyl-N',N'-bis(1-methyl-1H-imidazol-2-ylmethyl)ethane-1,2-diamine (L4), N,N-dimethyl-N',N'-bis(quinolin-2-ylmethyl)ethane-1,2-diamine (L5), tris(benzimidazol-2-ylmethyl)amine (L6) and tris(pyrid-2-ylmethyl)amine (L7), have been isolated and characterized using CHN analysis, UV-Visible spectroscopy and mass spectrometry. The single-crystal X-ray structures of the complexes [Ni(L1)(CH(3)CN)(H(2)O)](ClO(4))(2) 1a, [Ni(L2)(CH(3)CN)(2)](BPh(4))(2) 2, [Ni(L3)(CH(3)CN)(2)](BPh(4))(2) 3 and [Ni(L4)(CH(3)CN)(2)](BPh(4))(2) 4 have been determined. All these complexes possess a distorted octahedral coordination geometry in which Ni(II) is coordinated to four nitrogen atoms of the tetradentate ligands and two CH(3)CN (2, 3, 4) or one H(2)O and one CH(3)CN (1a) are located in cis positions. The Ni-N(py) bond distances (2.054(2)-2.078(3) Å) in 1a, 2 and 3 are shorter than the Ni-N(amine) bonds (2.127(2)-2.196(3) Å) because of sp(2) and sp(3) hybridizations of the pyridyl and tertiary amine nitrogens respectively. In 3 the Ni-N(im) bond (2.040(5) Å) is shorter than the Ni-N(py) bond (2.074(4) Å) due to the stronger coordination of imidazole compared with the pyridine donor. In dichloromethane/acetonitrile solvent mixture, all the Ni(ii) complexes possess an octahedral coordination geometry, as revealed by the characteristic ligand field bands in the visible region. They efficiently catalyze the hydroxylation of alkanes when m-CPBA is used as oxidant with turnover number (TON) in the range of 340-620 and good alcohol selectivity for cyclohexane (A/K, 5-9). By replacing one of the pyridyl donors in TPA by a weakly coordinating -NMe(2) or -NEt(2) donor nitrogen atom the catalytic activity decreases slightly with no change in the selectivity. In contrast, upon replacing the pyridyl nitrogen donor by the strongly σ-bonding imidazolyl or sterically demanding quinolyl/benzimidazolyl nitrogen donor, both the catalytic activity and selectivity decrease, possibly due to destabilization of the intermediate [(4N)(CH(3)CN)Ni-O˙](+) radical species. Adamantane is selectively (3°/2°, 12-17) oxidized to 1-adamantanol, 2-adamantanol and 2-adamantanone while cumene is selectively oxidized to 2-phenyl-2-propanol. In contrast to cyclohexane oxidation, the incorporation of sterically hindering quinolyl/benzimidazolyl donors around Ni(ii) leads to a high 3°/2° bond selectivity for adamantane oxidation. A linear correlation between the metal-ligand covalency parameter (β) and the turnover number has been observed.

Progress in Ru-Based Amorphous Alloy Catalysts for Selective Hydrogenation of Benzene to Cyclohexene

Ru-based amorphous alloy catalysts prepared by the chemical reduction method have high activity and excellent cyclohexene selectivity due to their structure that has the merits of amorphous alloys and nano-particles. In particular, the supported catalysts have the advantages of better utilization of the Ru noble metal and ease of use in industry. The thermodynamics and kinetics for selective hydrogenation of benzene to cyclohexene over these catalysts, and the influence of the structure and composition of the catalysts were described. The reaction conditions, ability to modify the catalysts, and results of pilot tests were emphasized. Directions in this field for future research were suggested. ：化学还原法制备的非晶态合金 Ru 基催化剂融合了纳米粒子和非晶态合金的结构特征, 在苯选择加氢反应中表现出高活性和高环己烯选择性; 尤其是负载型非晶态合金 Ru 基催化剂, 具有贵金属利用率高和易于工业化等优点, 有着明显的竞争优势. 本文综述了苯选择加氢的热力学和动力学特征, 非晶态合金催化剂结构和组成及其对催化性能的影响; 总结了催化工艺条件、催化剂可调变性和中试成果, 并展望了该技术的发展趋势.

Selective hydrogenation of benzene to cyclohexene on Ru-based catalysts promoted with Mn and Zn

Abstract Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promoted with Zn or Mn alone. The optimum Mn/Zn molar ratio was determined to be 0.3. With the addition of 0.5 g NaOH, the Ru-Mn-Zn-0.3 catalyst, which was reduced at 150 °C, afforded a cyclohexene selectivity of 81.1% at a benzene conversion of 60.2% at 5 min and a maximum cyclohexene yield of 59.9% at 20 min. Based on characterizations, the excellent performance of Ru-Mn-Zn catalyst was ascribed to the suitable pore structure, the appropriate reducibility and the homogenous chemical environment of the catalyst.

Ruthenium containing hydrotalcite as a heterogeneous catalyst for hydrogenation of benzene to cyclohexane

Ruthenium containing hydrotalcite (Ru-HT) was synthesized by partial substitution of Mg 2+ or Al 3+ cations by ruthenium metal in octahedral layers of hydrotalcite and used as a catalyst for hydrogenation of benzene to cyclohexane. Effect of catalyst amount, reaction temperature, partial pressure of hydrogen and volume of solvent on conversion of benzene was studied in detail. Higher conversion of benzene in lower reaction time was observed in lower volume of solvent. Complete conversion of benzene with 100% selectivity of cyclohexane was observed at 120 °C reaction temperature and 60 atm partial pressure of H 2 in 2 h reaction time. Presence of moisture in the reaction mixture showed negligible effect on catalytic activity of Ru-HT, however, activity decreased significantly on increasing the sulfur concentration. Catalyst was recycled upto four times without significant loss in its activity. No conversion of benzene was observed in case of pristine hydrotalcite (without ruthenium) as a catalyst.