Phenol Selectivity Research Articles

Bio‐Oil as a Potential Biomass‐Derived Renewable Raw Material for Bio‐Phenol Production

AbstractA route for directional conversion of bio‐oil into phenol by means of coupling the catalytic cracking of the bio‐oil with the hydroxylation of the bio‐oil‐based benzene‐rich aromatics is proposed. High selectivity for phenol in the resulting organic liquid was achieved, with an almost complete conversion of the bio‐oil. Co‐cracking of the bio‐oil with methanol over a Zn‐modified zeolite significantly enhanced the yields of aromatics and decreased the deactivation of the catalyst during the catalytic cracking of the bio‐oil. The phenol yield depended on the metal oxide catalysts, the temperature, and the reaction time during hydroxylation of the benzene‐rich aromatics. The reaction pathway of converting bio‐oil into phenol was elucidated based on the products identified and the characterization of the catalysts.

Photooxygenation of Hydrocarbons with Molecular Oxygen By Electron Transfer

Phenol is an very important bulk organic compound, having a variety of applications in industry. Phenol is commercially produced through three-step cumene process via cumene hydroperoxide, which is the key intermediate. In addition acetone is produced as a co-product and a-methylstyrene is produced as a byproduct together with phenol. Thus, phenol synthesis from benzene in a one-step reaction with high benzene conversion and high phenol selectivity is highly desired from the viewpoints of an environmentally benign green process and economical efficiency. Extensive efforts have so far been devoted to develop the one-step direct hydroxylation of benzene using various oxidants. we would like to focus on the catalytic mechanisms of selective hydroxylation of benzene to phenol. First, catalytic mechanisms of liquid phase hydroxylation of benzene with H2O2 using metal complexes are discussed by identifying the reactive intermediates, which act as strong electrophiles for the benzene hydroxylation. Next, photochemical hydroxylation of benzene with an organic oxidant via benzene radical cation produced in photoinduced electron transfer from benzene to the excited state of the organic oxidant is discussed to clarify the reason of the selective hydroxylation to phenol. The reason why phenol is not further oxidized is discussed based on the Marcus theory of electron transfer. Finally, the photocatalytic hydroxylation of benzene with O2 to phenol is made possible by using an appropriate organic photocatalyst. The photochemical hydroxylation of benzene with an organic oxidant to phenol is also combined with the catalytic reoxidation of the reduced organic oxidant by O2 to make the selective hydroxylation of benzene with O2 to phenol catalytic. How overoxidation of phenol can be avoided is discussed in both the thermal and photochemical catalytic hydroxylation of benzene. Photochemical hydroxylation of benzene with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and water occurs under visible light irradiation to yield phenol and DDQH2. The yield of phenol was 99% with 99% conversion (>99% selectivity) [1]. The mechanism of the photochemical hydroxylation of benzene with DDQ was clarified by time-resolved transient absorption spectroscopy. The photochemical reaction was initiated by the photoinduced electron transfer from benzene to 3DDQ* to produce benzene p-dimer radical cation and DDQ•−. The free energy change for electron transfer from benzene to 3DDQ* is largely negative (DG et = −0.70 eV), as determined from the one-electron oxidation potential of benzene (E ox = 2.48 V vs. SCE) and the one-electron reduction potential of 3DDQ* (E red = 3.18 V vs. SCE). Then, benzene radical cation reacts with H2O to produce an OH-adduct radical of benzene. Finally, phenol was produced by hydrogen atom transfer from the OH-adduct radical to DDQ•–. Photoinduced oxygenation of neat cyclohexane in the presence of O2 also occurred under visible light irradiation of DDQ which acts as a super photooxidant. The products detected by GC and NMR analyses were cyclohexanol, cyclohexanone and cyclohexane hydroperoxide with 70, 40, 210% yields, respectively. When cyclohexane was replaced by n-butane, n-pentane and 3-methylpentane, the oxygenation reactions also took place to form the corresponding oxygenated products under the otherwise same photochemical reaction conditions [2-5]. [1] Ohkubo, K.; Fujimoto, A.; Fukuzumi, S. J. Am. Chem. Soc. 2013, 135, 5368. [2] Ohkubo, K.; Hirose, K.; Fukuzumi, S. Chem.–Eur. J. 2015, 21, 2855. [3] Ohkubo, K.; Hirose, K.; Fukuzumi, S. Photochem. Photobiol. Sci. 2016, 15, 731. [4] Ohkubo, K.; Hirose, K.; Fukuzumi, S. Chem. Asia J. 2016, 11, 2218. [5] Fukuzumi, S.; Ohkubo, K. Asian J. Org. Chem. 2015, 4, 836 (Focus Review).

Renewable High-Purity Mono-Phenol Production from Catalytic Microwave-Induced Pyrolysis of Cellulose over Biomass-Derived Activated Carbon Catalyst

The activated carbons (ACs) enriched in P-containing functional groups were obtained through one-pot microwave-induced pyrolysis from corn stover activated with phosphoric acid and were further tested as the catalyst for selective monophenol production from cellulose pyrolysis for the first time. Maximum AC yield (44.3 wt %) was obtained with an acid to biomass ratio of 0.85. Increasing phosphoric acid to corn stover ratios could enhance the porosity and peak intensities of P-containing functional groups in obtained ACs. Attained ACs had an excellent catalytic performance in phenol production with the highest selectivity of phenol (99.02 % based on peak area) in the obtained organic compounds at the catalytic temperature of 450 °C. The catalytic performance of ACs remained highly selective for phenol after using two times. The experimental results indicated that P-containing groups such as −O–P, O═P, and −O–P–O– were the active reaction sites and more mespores promoted phenol production. The phenol can be...

A CuII‐based Metal–Organic Framework as an Efficient Photocatalyst for Direct Hydroxylation of Benzene to Phenol in Aqueous Solution

AbstractA CuII‐based metal–organic framework (MOF; 1), constructed with imidazole carboxylate ligands (5‐(1 H‐imidazol‐1‐yl)isophthalic acid) and copper(II) ions was prepared and characterized in detail by XRD, Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), and IR methods. Its catalytic performance for the direct hydroxylation of benzene to phenol has been investigated. A benzene conversion of 29 % as well as a high phenol selectivity above 95 % has been obtained at 60 °C in water. The cycling tests showed no significant decrease after five runs, indicating good stability and reuse properties of the CuII‐based MOF (1). The effect of adding the hydroxyl radical scavenger, thiourea, and the ESR spectra of the catalytic system have confirmed the existence of hydroxyl radicals, which indicates the catalytic mechanism follows a Fenton‐type route. This economically and environmentally friendly approach with CuII‐based MOFs is expected to find applications in the hydroxylation of aromatics.

In-situ and ex-situ catalytic upgrading of vapors from microwave-assisted pyrolysis of lignin

In-situ and ex-situ catalytic upgrading with HZSM-5 of vapors from microwave-assisted pyrolysis of lignin were studied. The in-situ process produced higher bio-oil and less char than ex-situ process. The gas yield was similar for both processes. The ex-situ process had higher selectivity to aromatics and produced more syngas and less CO2 than the in-situ process. Additional experiments on ex-situ process found that the bio-oil yield and coke deposition decreased while the gas yield increased at higher catalyst-to-lignin ratios and catalytic upgrading temperatures. The increased catalyst-to-lignin ratio from 0 to 0.3 reduced the selectivity of methoxy phenols from 73.7% to 22.6% while increased that of aromatics from 1.1% to 41.4%. The highest selectivity of alkyl phenols (31.9%) was obtained at 0.2 of catalyst-to-lignin ratio. Higher catalytic temperatures favored greater conversion of methoxy phenols to alkyl phenols and aromatics. Appropriate catalyst-to-lignin ratio (0.3) together with higher catalytic temperatures favored syngas formation.

Hydrothermal Glucose Modified C/V-SiO2 as a Reusable Heterogeneous Catalyst for Benzene Oxidation to Phenol by O2

The C/V-SiO2 samples were synthesized by the hydrothermal treatment of aqueous glucose and V-SiO2 that was pre-prepared by a sol–gel process. The samples were characterized by XRD, XPS, EPR, FT-IR, SEM, N2 adsorption–desorption. The results showed that in the hydrothermal process the V-SiO2 was covered by a rod-like carbonization material, and a small portion of V5+ species was reduced to V4+. The activity of the C/V-SiO2 in benzene hydroxylation with O2 was tested. The leaching of V from the C/V-SiO2 during the reaction was restrained because the surface of the V-SiO2 was covered with the carbonization material. The phenol selectivity of 100% and benzene conversion of 10.8% over C/V(3.9)-SiO2 were obtained, and the catalytic performance did not decreased after being recycled three times. The leaching of V from the C/V-SiO2 was restrained in the hydroxylation of benzene with O2 because the surface of V-SiO2 was covered with the carbonization material.

Influence of Reaction Atmosphere (N2, CO, CO2, and H2) on ZSM-5 Catalyzed Microwave-Induced Fast Pyrolysis of Medicinal Herb Residue for Biofuel Production

Microwave-induced catalytic fast pyrolysis of medicinal herb residue was implemented to produce biofuel with the use of ZSM-5 catalyst and microwave receptive material (SiC). This research aims to explore the effect of reaction atmosphere on the pyrolytic product yields and oil chemical compositions. The results demonstrate that CO atmosphere leads to the lowest total liquid and oil fraction yields and the highest water yield. The hydrocarbon relative contents in bio-oil of the four reaction atmospheres follow the order of CO > CO2 > H2 ≈ N2, while the oxygenate relative contents in bio-oil show the opposite tendency. Further, CO atmosphere gives rise to the lowest selectivity of methoxy-containing phenols in oil fraction and thus can favor the production of a more stable pyrolytic bio-oil. Additionally, CO2 atmosphere causes the highest yield of syngas (CO + H2), which can be used as high quality fuel.

Pervaporative performance of polydimethylsiloxane–graphene/polyethersolfune hybrid membrane: Effects of graphene structure and surface properties

Graphene was produced either by chemical reduction of graphene oxide (GO) using hydrazine hydrate (HG)/sodium borohydride (BG) or by straight electrochemically exfoliation of graphite (EG). The X-ray diffraction and Raman spectroscopy confirmed smaller in-plane crystalline sizes for the chemically produced graphenes, and more number of layers and therefore lower structural defects for the EG sample.The graphene samples were used to prepare polydimethylsiloxane (PDMS)–graphene (G)/polyethersulfone (PES) hybrid membranes to investigate their pervaporative performances. All three produced hybrid membranes had better separation performances for removal of phenol from water in terms of phenol flux and selectivity compared to the unfilled membrane (1.3g/m2h and 11.09, respectively). An appropriate interfacial structure for the BG- and HG-filled membranes (having lower number of layers) was achieved at 0.2wt% graphene content while for the EG-filled membrane, it was attained at 0.4wt% graphene content. PDMS–BG/PES had the highest phenol flux of 3.6g/m2h due to the lowest carboxylic functional groups and highest C/O ratio of the filler, and PDMS–HG/PES had the best selectivity of 40.02 due to the lowest C/O ratio of the filler and hence the lowest water flux.

Competitive adsorption, selectivity and separation of valuable hydroxytyrosol and toxic phenol from olive mill wastewater

Competitive adsorption and selectivity of toxic phenol and hydroxytyrosol were studied on the macroreticular aromatic polymer (FPX66) and the macroporous polystyrene cross linked with divinylbenzene (MN202). The adsorption equilibrium of phenol and hydroxytyrosol as well as other phenolic compounds in olive mill wastewater (OMW) was investigated taking into account the different affinities of these compounds towards the two above mentioned resins. The experimental results showed that the adsorption equilibrium of phenol on FPX66 can be well interpreted by the BET model, indicating a multilayer adsorption, whereas, the adsorption of hydroxytyrosol on MN202 at equilibrium is well fitted by the Sips model. At low FPX66 concentration, phenol exhibited much higher adsorption percentage than hydroxytyrosol, indicating a stronger interaction with the resin. The adsorption selectivity ratio of phenol/hydroxytyrosol was of about 3.215 at 5gL−1 of FPX66. Thanks to the large affinity of hydroxytyrosol for the MN202 resin, its adsorption and recovery were higher than 90% on this resin. Thus, under suitable operating conditions, phenol was selectively separated on FPX66, while hydroxytyrosol was largely recovered from the OMW residual solution by adsorption on MN202.

Preparation and characterization of lanthanum phosphate catalysts for O-methylation of phenol to anisole in gas phase

Lanthanum phosphate catalysts have been synthesized in 3 different techniques such as (i) simple co-precipitation (LaP-1), (ii) co-precipitation followed by hydrothermal treatment (LaP-2) and (iii) pH variation method (6LaP-3 the prefixed 6 denotes the flocculated pH). Lanthanum and phosphate concentration in all the catalysts is constant (La/P=1) irrespective of method of preparation. All the 3 catalysts (LaP-1, LaP-2 and 6LaP-3) prepared by different methods are used as catalysts for the O-methylation of phenol and found that the catalyst prepared by pH variation method (6LaP-3) exhibited better activity. A series of catalysts with La/P=1 by pH variation method (2LaP-3, 6LaP-3, 9LaP-3 and 12LaP-3) have been prepared and characterized by FT-IR, X-ray diffraction and BET surface area to obtain the structural and textural information. Temperature programmed desorption of NH3 and CO2 studies of LaP-3 catalysts revealed the distribution and strength of acidic and basic sites respectively. LaP-3 catalysts are in hexagonal and rhabdophane phases (XRD). The LaP-3 catalysts are highly active and selective towards formation of anisole via methylation of phenol with methanol in the vapor phase. 2LaP-3 is the best catalyst among the LaP-3 catalyst series in the catalytic activity point of view. Weak and moderate acidic sites along with basic sites might have contributed for the high conversion of phenol and good selectivity of anisole.

One-Step Benzene Hydroxylation to Phenol Using CuOx /Mesoporous Hangjin 2# clay composites

In this work, CuOx/mesoporous Hangjin 2# clay catalysts were synthesized from Cu(NO3)2 and Hangjin 2# clay in one step. The prepared catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption measurements, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDX), and UV–visible diffuse reflectance spectroscopy (DRUV). These materials were employed in photocatalytic benzene hydroxylation to phenol with H2O2 as the oxidant, and the effects of the copper loading and light source on the reaction were studied. The results show that the phenol selectivity and yield initially increased and then decreased with increasing copper content. Under the optimized reaction conditions, the phenol selectivity and yield were 91.9 % and 25.6 %, respectively. Catalyst is still active after the repeat three times.

Hydrogenation of Phenol over Pt/CNTs: The Effects of Pt Loading and Reaction Solvents

Carbon nanotubes (CNTs)-supported Pt nanoparticles were prepared with selective deposition of Pt nanoparticles inside and outside CNTs (Pt–in/CNTs and Pt–out/CNTs). The effects of Pt loading and reaction solvents on phenol hydrogenation were investigated. The Pt nanoparticles in Pt–in/CNTs versus Pt–out/CNTs are smaller and better dispersed. The catalytic activity and reuse stability toward phenol hydrogenation both improved markedly. The dichloromethane–water mixture as the reaction solvent, compared with either pure medium, decreased the catalytic activity toward phenol hydrogenation and selectivity of cyclohexanone over Pt–in/CNTs, but significantly improved the catalytic activity toward phenol hydrogenation and selectivity of cyclohexanone over Pt–out/CNTs.

Support effect and metals interactions for NiRu/Al2O3, TiO2 and ZrO2 catalysts in the hydrodeoxygenation of phenol

The bio oil of pyrolysis can be upgraded via hydrodeoxygenation to remove unfavorable characteristics related to high levels of oxygen. Sulfided NiMo and CoMo catalyst have been studied extensively in hydrodeoxygenation. However, significant deactivation may occur, due to the lack of sulfur in the charges or to coke deposition, induced by strong acidic supports. Therefore, development of new catalytic materials with alternative supports and active phases is relevant. In this work, Ni, Ru, and Ni-Ru catalysts were prepared by wet impregnation of Ni(NO3)2·6H2O and Ru(NO)(NO3)3 solutions. Al2O3, TiO2, and ZrO2 were used as supports, evidencing influence on hydrodeoxygenation (HDO) of phenol activity and selectivities. TPR and XPS characterization revealed a promoter effect of ruthenium over Ni reducibility and in some cases, a synergetic effect on catalytic activity in phenol HDO reaction was observed. The metallic ruthenium particles were reduced at low temperatures, and they enhanced reduction of Ni by H2 spillover effect, due to a close contact between metals. Furthermore, TPD-NH3 indicated a possible correlation between catalyst acidity and HDO reaction rate.

Application of Hydroxylamine Ionic Liquid Salts in Hydroxylation of Benzene to Phenol with Ammonium Molybdate–Copper Chloride–Ionic Liquid System

Several novel hydroxylamine ionic liquid salts were applied in direct hydroxylation of benzene to phenol in ammonium molybdate–copper chloride–ionic liquid system. Hydroxylamine ionic liquid salt was used as the eco-friendly hydroxylation agent, ammonium molybdate and copper chloride were used as the catalyst and additive, respectively, while the ionic liquid was used as the green cosolvent. The new system demonstrated an enhanced phenol selectivity (100%) and phenol yield (11.2%) due to the addition of Cl− and copper ions. Therefore, Cl− ions could increase the phenol selectivity and copper ions helped in improving the phenol yield. Furthermore, the ILs-Mo-Cu catalytic system could be recycled at least three times.

Catalytic fast co-pyrolysis of bamboo residual and waste lubricating oil over an ex-situ dual catalytic beds of MgO and HZSM-5: Analytical PY-GC/MS study

Catalytic fast co-pyrolysis (co-CFP) of bamboo residual (BR) and waste lubricating oil (WLO) over dual catalytic beds of MgO and HZSM-5 were carried out in an analytical PY-GC/MS. The effects of pyrolysis temperature, catalyst types, HZSM-5/MgO mass ratio and WLO percentage on products distribution and selectivities of aromatics were investigated. Experimental results revealed that 600°C promoted the total peak area of volatile matters and accelerated the yields of furans and phenols. Compared to HZSM-5, MgO exhibited pronounced deacidification via ketonization and aldol condensation reactions as the minimum yield of acids (2.116%) and the maximum yield of ketones (28.805%) could be obtained. Furthermore, given the selectivity of phenols, MgO not only spurred the increase of overall phenols yield, but also facilitated the selectivity of light phenols like phenol and 4-methyl-phenol. With respect to the co-CFP of BR and WLO, a HZSM-5/MgO mass ratio of 3:2 largely accelerated the yield of aromatics via Diels-Alder reaction. Simultaneously, the WLO percentage played a vital role in the yield of hydrocarbons (i.e. aromatics+olefins & alkanes), and the maximum yield (70.305%) could be attained at the percentage of 60% as a function of significant activation of hydrocarbon pool.

Vanadium-containing mesoporous carbon and mesoporous carbon nanoparticles as catalysts for benzene hydroxylation reaction

Highly ordered mesoporous carbon of body-centered cubic structure was synthesized by the evaporation induced self-assembly method using Pluronic F127 and phenolic resol as the template and carbon source, respectively. Vanadium species were introduced to the carbon support by both co-assembly and impregnation strategies for comparison. Ordered mesoporous carbon nanoparticles of the same body-centered cubic structure were also synthesized via a facile soft-template method, followed by the incorporation of vanadium species via impregnation. The obtained three different series of vanadium-containing carbon catalysts were tested in the direct benzene hydroxylation reaction using H2O2 as an oxidant. The vanadium supporting mesoporous carbon nanoparticles, due to the open framework and short channels for fast reactants diffusion and the easily accessible active vanadium species for reactants activation, exhibited superior catalytic activity to other series of catalysts. Particularly, the 4V/MCN-S catalyst showed the best catalytic performance among the studied catalysts with a benzene conversion of 38.2% and phenol selectivity of 96.1%, along with good stability during five recycles.

Direct synthesis of phenol by novel [FeFe]-hydrogenase model complexes as catalysts of benzene hydroxylation with H2O2

Compared the catalytic performance of complexes 1–3, the complex 2 has the highest phenol yield (24.6%) and phenol selectivity (92%), which has the highest electron densities of the catalytically active sites.

Selective phenol hydrogenation to cyclohexanone over alkali–metal-promoted Pd/TiO2 in aqueous media

High conversion of phenol and high selectivity of cyclohexanone could be achieved by using alkali–metal-promoted Pd/TiO2 catalysts under mild conditions.

VxOy@C catalyst prepared from biomass for hydroxylation of benzene to phenol with molecular oxygen

The selectivity of phenol for the hydroxylation of benzene was found to be related to the adsorption of phenol on the VxOy@C catalyst.

Effect of zeolite solid acids on the in situ hydrogenation of bio-derived phenol

The effect of zeolite solid acids on the in situ hydrogenation of bio-derived phenol over Raney Ni was investigated, which indicated that the conversion of phenol increased with the addition of zeolite solid acids and Hbeta (Si/Al=60) showed the best performance of high phenol conversion and selectivity towards the desired products and low carbon loss. In addition, the quantity of Hbeta (Si/Al=60) and Raney Ni had marked impact on the carbon loss, but little effect on both the conversion and the products distribution. And the mixed catalysts of Raney Ni and Hbeta (Si/Al=60) exhibited excellent stability.