Selective Hydrogenation Of Benzene Research Articles

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.

Highly selective benzene hydrogenation to cyclohexene over supported Ru catalyst without additives

The Ru/ZnO–ZrOx(OH)y catalyst is very efficient for the selective hydrogenation of benzene to cyclohexene, and the yield of cyclohexene can reach 56% without using any additive. This work provides a highly efficient, cheap and clean method to produce cyclohexene.

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.

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%.

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.

The Modifiable Character of a Novel Ru‐Fe‐B/ZrO2 Catalyst for Benzene Selective Hydrogenation to Cyclohexene

AbstractA novel Ru‐Fe‐B/ZrO2 catalyst for the selective hydrogenation of benzene to cyclohexene was prepared by the chemical reduction method. A yield of cyclohexene of 57.3% was achieved at benzene conversion of 80.6% on this catalyst. The activity and yield of cyclohexene were higher than those studied previously. The structural characterizations of the catalyst were performed by TEM‐SAED, XRD, and N2‐physisorption. Moreover, cyclohexene selectivities on this catalyst increased and the activities decreased with the increase of the ZnO dosages, however, the activities increased and cyclohexene selectivities decreased with the increase of the H2SO4 dosages. Different feeding manners of H2SO4 or ZnO exerted definitely influence on the performances of this catalyst, but the degrees of influence were different due to the character of chemisorptions. Furthermore, the activity and cyclohexene selectivity on the catalysts could be reversibly modified by adding H2SO4 or ZnO into reaction slurry, which provides an easy method to recover the activity and selectivity of Ru‐Fe‐B/ZrO2 catalysts during the process of producing cyclohexene. And the modifiable mechanisms involved were speculated.

Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalyst with Nanosized Zirconia as Dispersant

Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalyst with Nanosized Zirconia as Dispersant

Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalyst with Nanosized Zirconia as Dispersant

Nanosized zirconia was prepared by hydrothermal synthesis. The effect of zirconia with the different surface areas of 34 and 87 m2/g (denoted ZrO2-34 and ZrO2-87, respectively) used as dispersants on the catalytic properties of the Ru-Zn catalyst was investigated. The crystallite sizes of ZrO2-34 and ZrO2-87 were 21.6 and 11.4 nm, respectively. They had similar purity and phases. Cyclohexene selectivity and the stability of the Ru-Zn catalyst dispersed using ZrO2-34 were better than that using ZrO2-87. This was due to the smaller surface area, bigger pore diameter, smaller particle size, narrower particle distribution, and bigger larger density of ZrO2-34.

Preparation and Characterization of Ru/Al2O3/Cordierite Monolithic Catalysts for Selective Hydrogenation of Benzene to Cyclohexene

A series of Ru/Al2O3/cordierite monolithic catalysts were prepared and characterized by BET, XRD, TPR, TEM and SEM-EDAX. The catalytic performances in selective hydrogenation of benzene to cyclohexene were investigated in a continuous fixed-bed reactor. The preparation conditions significantly influence morphology, particle size, and surface area of the catalyst, subsequently affecting the catalytic performances. It was found that higher calcination temperature of the Ru-based monolithic catalyst led to the conglomeration and crystallite growth of the t-RuO2, which will decrease the catalytic activity. The lower thickness and the larger pore size of the alumina washcoating layer are the preferential choices to obtain higher cyclohexene selectivity due to the improved internal mass transfer of cyclohexene. It was also found that high ruthenium loading resulted in deep hydrogenation of cyclohexene. Moreover, the reduction temperature was optimized to 473 K and excess high temperature led to the deterioration of both activity and cyclohexene selectivity.

Liquid-phase selective hydrogenation of benzene to cyclohexene on Ru/Al 2O 3–ZrO 2/cordierite monolithic catalysts

Monolithic catalysts, Ru/Al 2O 3–ZrO 2/cordierite, were prepared by dipcoating and impregnation for liquid-phase selective hydrogenation of benzene to cyclohexene in a continuous fixed bed reactor. Ru/Al 2O 3–ZrO 2/cordierite showed excellent catalytic performance due to the high specific surface area and the large pores of Al 2O 3–ZrO 2 support. The Zr/Al ratio was optimized to be 0.116 and the excessive amount of ZrO 2 resulted in a decreased specific surface area of the Al 2O 3–ZrO 2 washcoating layer. The preferable calcination temperature is 1373 K for Al 2O 3–ZrO 2 support, at which suitable BET surface area and pore size distribution could be obtained. It was also found that appropriate ratio of Zn/Ru was essential to obtain high selectivity. Additionally, compared to the powder catalysts used in the slurry reactor, the monolithic catalysts exhibited much higher activity regarding the yield of cyclohexene and cyclohexane.

Pd/Al 2O 3 catalyst for selective hydrogenation of benzene in benzene–toluene mixture

Pd/Al2O3 demonstrates (in comparison with Pt/Al2O3 and Ni/Al2O3) higher selectivity toward benzene hydrogenation in competitive hydrogenation of a benzene–toluene mixture, which can be enhanced (up to 76%) by the increase of overall reaction pressure up to 37 atm.

Ce-promoted Ru/SBA-15 catalysts prepared by a “two solvents” impregnation method for selective hydrogenation of benzene to cyclohexene

Abstract Ce-promoted Ru/SBA-15 catalysts were prepared by a “two solvents” impregnation method. In liquid-phase hydrogenation of benzene, the Ce-promoted Ru/SBA-15 catalysts exhibited superior catalytic performance to the un-promoted catalyst. The optimum bulk Ce/Ru molar ratio was determined to be 0.25, at which a cyclohexene yield of 53.8% was obtained. Based on characterizations, the beneficial effect of the Ce promoter on the selectivity to cyclohexene was ascribed to the enhancement of the hydrophilicity of the catalyst and to the electron transfer between the Ce(III) species and metallic Ru.

Selective hydrogenation of benzene to cyclohexene over RuCoB/γ-Al2O3 without additive

Abstract Catalyst RuCoB/γ-Al 2 O 3 was prepared by the reduction impregnation method and characterized by ICP, TEM, XRD, XPS, and TPR. The catalyst showed a high selectivity to cyclohexene for the partial hydrogenation of benzene without any additive. The high selectivity possibly results from that cobalt and boron cause the formation of electron-deficient ruthenium species. Under the optimum conditions, the maximum yield of cyclohexene reached 28.8%.

Selective Hydrogenation of Benzene to Cyclohexene on a Ru/Al2O3/Cordierite Monolithic Catalyst: Effect of Mass Transfer on the Catalytic Performance

A Ru/Al2O3/cordierite monolithic catalyst was prepared, characterized, and examined in selective hydrogenation of benzene to cyclohexene in a monolithic fixed-bed reactor with an aqueous solution of ZnSO4. The Carberry number and Wheeler−Weisz group were calculated to analyze the effects of external and internal diffusions of H2, benzene, and cyclohexene. According to the results of calculations, the water film, solubility, and diffusion coefficients of the three reactants (H2, benzene, and cyclohexene) play important roles in the mass-transfer rate. Under proper reaction conditions, the effects of the external mass transfer of H2 and benzene on the reaction rate are negligible. For the hydrogenation of cyclohexene, the diffusion of cyclohexene from the organic phase to the catalyst is the limiting step in the presence of water, which is the most important factor for obtaining high cyclohexene selectivity. The absence of pore diffusion of the three reactants, which is attributed to the thin eggshell distr...

Effect of organic additives on partial hydrogenation of benzene

A new RuCoB/γ-Al2O3 catalyst was prepared by reduction impregnation method and was used for the partial hydrogenation of benzene. Its composition and structure were determined by ICP, XRD, and XPS. The performance of the catalyst for the selective hydrogenation of benzene to cyclohexene was investigated in liquid catalytic system. The hydrogenation results showed that in the presence of ZnSO4, the addition of amines and alcohols could significantly enhance the yield of cycylohexene. The maximum cyclohexene yield of 34.8% was achieved with ethylenediamine as an additive.

Characterization and study on performance of the Ru–La–B/ZrO2 amorphous alloy catalysts for benzene selective hydrogenation to cyclohexene under pilot conditions

Various characterizations of Ru–La–B/ZrO2 catalysts were carried out by means of XRD, TEM, SEAD, XPS and N2-physisorption, and the activity and selectivity of the catalysts were measured. XRD results showed that Ru–La–B/ZrO2 catalysts were considerable stable and no significant peaks corresponding to Ru crystal were observed for the catalysts treated below 673 K and ran for 500 h under pilot conditions. The study on N2-physisorption showed that with extending of the reaction time the most probable pore diameters, specific surface areas and pore volumes became smaller supposed to be relative to the adsorption of substances in the reaction mixture and to be one of the reasons for decreasing of the activity and selectivity of the catalysts. XPS showed that ruthenium exists in metallic state; lanthanum exists in La3+ or in metallic state. One of the most remarkable features of Ru–La–B/ZrO2 catalysts is the high activity and good selectivity for benzene selective hydrogenation to cyclohexene. On the other hand, the catalysts can be regenerated and have a long life under pilot conditions.

Monolithic Ru-based catalyst for selective hydrogenation of benzene to cyclohexene

A novel Ru-based cordierite monolithic catalyst was prepared for the selective hydrogenation of benzene to cyclohexene. The catalyst was characterized by elemental analysis, XRD, SEM-EDX and physisorption measurements. The performance of the catalyst was tested in a continuous monolithic fixed bed reactor (MFBR). Compared with particulate catalyst, the monolithic catalyst gave much higher selectivity. Monolithic catalyst with ZrO2-Al2O3 as washcoating was found to be more active than that with Al2O3 as washcoating and a high cyclohexene yield of about 30% was achieved at a relatively lower LHSV. The egg-shell distribution of the active component, the large pores in the walls of cordierite monolith and the Taylor flow pattern formed in the monolith channels were considered to be the crucial reasons. (C) 2007 Elsevier B.V. All rights reserved.

Study on the Nanosized Amorphous Ru-Fe-B/ZrO 2 Alloy Catalyst for Benzene Selective Hydrogenation to Cyclohexene

A novel nanosized amorphous Ru-Fe-B/ZrO 2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize and the amorphous character as well as to its textural character. In addition, the concentration of zinc ions, the content of ZrO 2 in the slurry, and the pretreatment of the catalyst were found to be effective in improving the activity and the selectivity of the catalyst.

A novel amorphous alloy Ru–La–B/ZrO 2 catalyst with high activity and selectivity for benzene selective hydrogenation

A novel amorphous alloy Ru–La–B/ZrO 2 catalyst with high activity and good selectivity to cyclohexene was prepared by a chemical reduction method. Various characterizations on the catalyst were carried out by means of XRD, TEM-SAED, XPS, ICP-AES, PSD and N 2-physisorption. The performance of the catalysts was examined under pilot conditions. The results showed that the bulk composition of the catalyst was Ru 18.14La 0.08B 18.86/ZrO 2, that almost all ruthenium species existed in the elemental state, and that La existed in the La 3+ state. The most probable pore diameter is about 32 nm, and the most probable particle size was ca. 5 μm. The performance and stability of the Ru–La–B/ZrO 2 catalyst is superior to that of the Ru–B/ZrO 2 due to the promoting effect of La. The slurry comprising zirconia and zinc sulfate is very important for benzene selective hydrogenation over the Ru–La–B/ZrO 2 catalysts in order to obtain high yield to cyclohexene. Under the pilot conditions, the performance of the Ru–La–B/ZrO 2 catalysts can be improved by changing the pH value of the slurry and by adding zirconia into the slurry.

Effect of Lanthanum on Performance of RuB Amorphous Alloy Catalyst for Benzene Selective Hydrogenation

The effect of La on the performance of a supported RuB amorphous alloy catalyst for benzene selective hydrogenation was studied by means of activity and selectivity tests, such as HRTEM, SAED, XPS, and XRD. The results show that the addition of La to RuB amorphous alloy catalyst can evidently increase the activity and improve the thermal stability of RuB amorphous alloy to refrain its crystallization. The promoting effect of La on the activity of RuB amorphous alloy catalyst is because of the high dispersion of the active components.