Catalytic Hydrogenation Of Phenol Research Articles

Highly efficient hydrogenation of phenol and lignin-derived compounds over Ru-Rh bimetallic nanoparticles supported on α-Al2O3 at room temperature

Catalytic hydrogenation of phenol and lignin-derived compounds is an important strategy to produce chemical and pharmaceutical intermediates, but it is still a challenge to achieve this process under mild conditions. Herein, the bimetallic Ru-Rh/α-Al2O3 catalyst was successfully prepared and used for the direct hydrogenation of phenol and lignin-derived compounds. The results of this study illustrate that Ru-Rh/α-Al2O3 exhibits the highest activity for the hydrogenation of phenol and diphenyl ether among these catalysts. Phenol can be completely converted to the target product of cyclohexanol over Ru-Rh/α-Al2O3 under extremely mild conditions (30 °C, 1 MPa H2, 90 min). With Ru-Rh/α-Al2O3 as the catalyst, a variety of other unsaturated substrates are also efficiently hydrogenated to the corresponding ring-saturated products with a high yield. The characterizations reveal that the strong interaction formed between Ru and Rh is mainly responsible for the enhancement of the hydrogenation activity. The construction of the bimetallic Ru-Rh/α-Al2O3 catalyst can accelerate the high value-added utilization of phenol and lignin-derived compounds.

Tuning surface properties of N-doped carbon with TiO2 nano-islands for enhanced phenol hydrogenation to cyclohexanone

Abstract ZIF-derived N-doped carbon (CN) materials were modified in this work by TiO2 nano-islands with oxygen vacancies (OV) through a sol-gel method and subsequent thermal treatment. By loading Pd nanoparticles (NPs) on CN@TiO2, Pd@CN@TiO2 catalysts were fabricated. Superior catalytic performance of Pd@CN@TiO2 was found in the selective phenol hydrogenation to cyclohexanone, with a TOF of 30.1 h−1, 2.2-fold as high as that of Pd@CN. The synergistic effect of CN and TiO2 nano-islands was responsible for the superior catalytic performance. More OV was generated due to the high specific surface area of CN. At the same time, CN could also enhance the hydrophilicity, and adsorb more phenol in non-planar fashion. The TiO2 nano-islands with OV could improve the Pd dispersion, make more Pd element on the support surface, strengthen the antioxidizability of Pd and induce electron-rich Pd NPs. Furthermore, the as-fabricated Pd@CN@TiO2 showed good recyclability in the phenol hydrogenation, and also exhibited excellent catalytic performance in the catalytic hydrogenation of phenol with diverse functional groups. These findings provide the feasibility of using the high-performance catalysts for the hydrogenation of phenol derivatives.

Interaction of Phenol and Cyclohexanol with Supercritical Water

Transformation of phenol and cyclohexanol was studied in supercritical water (SCW) in a flow reactor at 300 bar, 500–750°С, and LHSV = 1.2–2.0 h–1. At 500–600°С the only products of phenol conversion are aromatic hydrocarbons—benzene, toluene, naphthalene and polycyclic aromatic hydrocarbons. Almost complete conversion of phenol is achieved at 750°С with selectivity to gaseous products (H2, CO2, CH4, C2H4, C2H6) not higher than 30%. A preliminary catalytic hydrogenation of phenol to cyclohexanol facilitates both overall reaction with SCW and the formation of gaseous products. At temperatures as low as 600°С gaseous products are formed from cyclohexanol, and its complete conversion is achieved at 700°С. In the latter case, the yield of the gaseous products reaches 70%, including 40% of C1–C2 hydr°Carbons. The differences in the rate of conversion in SCW and in selectivity to gaseous products between phenol and cyclohexanol at 500–750°С are associated with the stability of the aromatic ring.

Comparison of Pd-UiO-66 and Pd-UiO-66-NH2 catalysts performance for phenol hydrogenation in aqueous medium

UiO-66, a kind of Metal-organic framework materials (MOFs) was used as a support for nano-palladium particles (i.e., Pd-UiO-66) which was used in the catalytic hydrogenation of phenol in aqueous media in this work. The performance of Pd-UiO-66 was compared with Pd-UiO-66-NH2, in which the UiO-66 support had been modified through the introduction of NH2 groups. Pd-UiO-66 and Pd-UiO-66-NH2 were characterized by BET, XRD, XPS and TEM. The results indicated that the Pd particles are embedded in Pd-UiO-66 and fixed on Pd-UiO-66-NH2. With NH2 groups, the crystalline structure of UiO-66-NH2 is somewhat damaged and the interaction between Zr and Pd in Pd-UiO-66-NH2 is rather weaker than in Pd-UiO-66. Pd-UiO-66 has high activity for aqueous phenol hydrogenation, with 100% conversion of phenol being achieved within 2h at 120°C, which is much higher than with the Pd-UiO-66-NH2 catalyst. Pd-UiO-66 has higher selectivity for cyclohexanol, and Pd-UiO-66-NH2 has higher selectivity for cyclohexanone under the same conditions. The study of the chemical kinetics portion revealed that the hydrogenation reaction rates with the Pd-UiO-66 catalyst are over 10 times higher than those with Pd-UiO-66-NH2 under the same conditions. The phenol hydrogenation catalyzed by Pd-UiO-66 is more sensitive to the reaction temperature than when catalyzed by the Pd-UiO-66-NH2 catalyst. Thus, it has been shown that modifications of an MOF support for a catalyst can result in structural changes that lead to different catalytic activities and selectivities in aqueous phenol hydrogenation.

A facile surfactant-free synthesis of Rh flower-like nanostructures constructed from ultrathin nanosheets and their enhanced catalytic properties

Rh is an important catalyst that is widely used in a variety of organic reactions. In recent years, many efforts have focused on improving its catalytic efficiency by fabricating catalyst nanoparticles with controlled size and morphology. However, the frequently employed synthesis route using organic compounds either as the reaction medium or capping agent often results in residual molecules on the catalyst surface, which in turn drastically diminishes the catalytic performance. Herein, we report a facile, aqueous, surfactant-free synthesis of a novel Rh flowerlike structure obtained via hydrothermal reduction of Rh(acac)3 by formaldehyde. The unique Rh nanoflowers were constructed from ultrathin nanosheets, whose basal surfaces comprised {111} facets with an average thickness of ~1.1 nm. The specific surface area measured by CO stripping was 79.3 m2·g−1, which was much larger than that of commercial Rh black. More importantly, the Rh nanoflower catalyst exhibited excellent catalytic performance in the catalytic hydrogenation of phenol and cyclohexene, in contrast to the commercial Rh black and polyvinyl pyrrolidone (PVP)-capped Rh nanosheets exposed by similar {111} basal surfaces.

Synthesis of SBA-15 Supported Rh Nanoparticles with High Loading Density and its Catalytic Hydrogenation of Phenol in Supercritical Carbon Dioxide

Rhodium (Rh) metal is used in a variety of organic reactions, especially in the hydrogenation of arenes which is an important chemical process in the synthesis of fine chemicals. Among diverse hydrogenations, the ring hydrogenation of phenol is considered as an important industrial reaction as its products, cyclohenxanol and cyclohexanone, are key intermediates for the manufacture of Nylon-6,6. 1 Although various liquid solvent systems have been mainly employed for such hydrogenation reaction of arenes catalyzed by Rh catalysts, the supercritical carbon dioxide (scCO2) can be an environmentally benign alternative in chemical technology to avoid the use of organic solvents. 2 Most of previous hydrogenations of phenol in scCO2 have been carried out with carbon or alumina supported Rh catalysts which have poor size distribution and dispersion of particles.

Study on the Catalytic Activities of Raney Nickel Catalysts. III. Activity in the Catalytic Hydrogenation of Phenol.

アルミニウム-ニッケル合金を展開し単位重量あたりの活牲が強いニッケル触媒をつくるためには,ニッケル含量が50wt%の合金を50℃ で約90分,60℃ ではほぼ1時間の展開処理がよく,その前後の展開温度では強力な活性の触媒をつくることは難かしい。しかし比表面積あたりの触媒活性は展開温度が低いほどよく,温度の上昇とともに活性は低下する。組成の異なるアルミニウム-ニッケル合金を展開したときは,合金のニッケル含量の減少につれて両種単位による活性はともに低下する。前報ニトロペンゼンおよびシクロヘキセンの還元において認められたように,ある温度において展開された触媒にはかならず極大活性の状態が存在し,本還元反応においてはたとえば40℃ では約2時間,50℃ においては約60分の展開によって実現される。2元触媒は一般に微量の第二金属添加によって極大活性となり以後添加量の増加につれて活性は低減する。すなわち微量の添加金属は助触媒として作用する。

Studies on the Catalytic Hydrogenation of Phenol and Naphthalene under High Pressure

還元ニッケルを觸媒としてフェノールを高壓水素下に還元するに90°より水素添加行はれてシクロヘキサノールを生じ,ナフタリンは75°Cより水素を吸收してデカリンを生ず.然るにフェノールとナフタリンの混合物の水素添加を行ふに75°Cより水素吸收始まリフェノールは變化せずしてナフタリンのみテトラリンに變化し,反應温度を高めて270°とすればフェノールもナフタリンも共に還元せらるる事を認めたり.