Benzyl Phenyl Ether Research Articles

Metal triflate formation of C12-C22 phenolic compounds by the simultaneous C-O breaking and C-C coupling of benzyl phenyl ether.

Catalytic pathways to produce high carbon number compounds from benzyl phenyl ether require multiple steps to break the aryl etheric carbon-oxygen bonds; these steps are followed by energy-intensive processes to remove oxygen atoms and/or carbon-carbon coupling. Here, we show an upgrading strategy to transform benzyl phenyl ether into large phenolic (C12-C22) compounds by a one-step C-O breaking and C-C coupling catalyzed by metal triflates under a mild condition (100 °C and 1 bar). Hafnium triflate was the most selective for the desired products. In addition, we measured the effect of solvent polarity on the catalytic performance. Solvents with a polarity index of less than 3.4 promoted the catalytic activity and selectivity to C12-C22 phenolic products. These C12-C22 phenolic compounds have potential applications for phenol-formaldehyde polymers, diesel/jet fuels, and liquid organic hydrogen carriers.

Solvolysis of benzyl phenyl ether in high-temperature aqueous methanol solution under high-pressure carbon dioxide

Alcoholysis of benzyl phenyl ether to various aromatic compounds was studied in high-temperature aqueous methanol solution under high-pressure carbon dioxide conditions.

The effect of carbon structure in chars on Fe migration and its catalytic activity for benzyl phenyl ether decomposition

This study aims to further understand the effect of carbon structure on the physiochemical status of metals and thus its activity during volatile-char interactions. The chars with distinctly different carbon substrates prepared from the pyrolysis of pine sawdust at 400 and 1000 °C were impregnated by different Fe contents, which were used as catalysts for benzyl phenyl ether (BPE, a typical lignin dimer) decomposition. The results demonstrated that the conversion of BPE was prominently improved with the iron addition, especially when the char prepared at the high temperature was loaded with 10% and 20% iron. The difference in carbon structure of two original chars have clearly resulted in the co-existence of various FexOy in chars at 400 °C and the dominant presence of α-Fe2O3 in chars at 1000 °C. Together with the Fe-containing active sites, the high orientation of carbon structure in the char from 1000 °C has considerably favored the high selectivity of product formation during the catalytic reforming of BPE and its derived volatile components.

Effect of kaolinites modified with Zr and transition metals on the pyrolysis behaviors of low-rank coal and its model compound

Acid treated kaolinites (KA) were successively loaded with Zr and Fe, Ni or Co component to control the product distribution and upgrade the tar quality in coal pyrolysis. The structure of the resultant catalysts was characterized and their catalytic performance in the pyrolysis of demineralized low-rank coal and benzyl phenyl ether (BPE), a model compound containing Cal-O bridge bond, were investigated. Results show that the introducing of Zr into the KA can enlarge the hysteresis loop due to the stacking of ZrO2 particles. The acidities, especially the strong ones, increase as the Zr content is below 8 wt% (KA-8Z). When adding Fe, Ni or Co metals into the KA-8Z, the number of Brønsted acid sites obviously decreases, but Lewis acid sites increase. The maximum BPE conversion of 94.0% occurs for the KA-8Z, further metal-loaded sample promotes the cleavage of Cal-O bond in BPE and the formation of active H radicals from CH3OH, leading to the increase of BPE conversion. Besides, remarkable enhancement of target monomeric aromatics is observed for the Fe, Ni and Co-loaded samples. Compared with the pyrolysis without catalyst, the tar yield as well as pitch content decrease over the KA-8Z and its metal-modified catalysts. Wherein, Ni-KA-8Z has the highest activity for tar upgrading, leading to the largest increase in the contents of light oil and phenol oil. In-situ pyrolysis by time-of-flight mass spectrometry reveals the enhanced dissociation of weak covalent bonds linked in the coal skeleton over the KA-8Z and Fe, Ni and Co-modified catalysts, resulting in a decrease in the peak temperature for product release. A marked increase in phenols and diphenols confirms a promoted dissociation of ether bond in coal.

Acid-Catalyzed α-O-4 Aryl-Ether Cleavage Mechanisms in (Aqueous) γ-Valerolactone: Catalytic Depolymerization Reactions of Lignin Model Compound During Organosolv Pretreatment.

In this study, acidolysis of benzyl phenyl ether (BPE), being a representative lignin model compound with the α-O-4 linkage, was examined in γ-valerolactone (GVL) and a GVL/water mixture, each time acidified with sulfuric acid. The product distribution was strongly affected by water used as a cosolvent, which was found to be advantageous by inhibiting the formation of larger structures and introducing reactive OH groups instead. The experimental results indicate the GVL/water ratio as an important parameter to attain an optimal hydrolytic α-ether bond cleavage. Differences between the organosolv lignins (molecular weight distribution, OH group content, and structural features with reaction time), isolated under moderate reaction conditions, supported the findings obtained using BPE. A beneficial effect of the added water is reflected in the higher aliphatic OH group content and less intact structure. Analysis of the reaction mechanism represents an initial step toward kinetics and structure–activity correlation of biorefining industrial resources.

Choline Hydroxide as a Versatile Medium for Catalyst‐Free O‐Functionalization of Phenols

A versatile synthetic protocol for benzyl phenyl ether preparation via O‐alkylation of phenolic oxygen with readily available benzyl derivatives was demonstrated. The newly designed procedure was carried out using an eco‐friendly medium, room‐temperature ionic liquid (choline hydroxide), under metal‐ and base‐catalyst‐free aerobic conditions. The reaction platform was also successfully applied to phenol protection strategy.

Theoretical insight into the hydrogenolysis mechanism of lignin dimer compounds based on experiments

Deep insight of reaction mechanism in lignin model compounds is helpful to achieve the directed depolymerization of lignin or biomass to chemicals or fuels. In this study, the density functional theory (DFT) calculation was employed to investigate the cleavage mechanism of the C–O bonds in lignin dimers. Additionally, the intrinsic chemical reactivity of molecular in term of the Fukui function was applied to predict the most probable sites which react with hydrogen free radicals (H·). It was found that the O atoms in lignin dimers are the most reaction site involving H· because of the large f (0). By this method, the most rational path from a series of reaction paths was screen out. Apart from the Fukui function, the average local ionization energy (ALIE) was analyzed to prove the reliability of Fukui function. The kinetic analysis of the reaction path was performed to further understand the impact of temperature on the reaction rate constant (KTST). It is observed that benzyl phenyl ether (BPE) with higher KTST could be easily cleaved because of the relatively low energy barrier.

Hydrogenolysis of aromatic ethers under lignin-first conditions

The cleavage of the etheric CO bond in diphenyl ether (DPE), phenethyl phenyl ether (PPE) and benzyl-phenyl ether (BPE) has been investigated by using Ru/C (5% wt) and Pd/C (5% wt), as heterogeneous catalysts, under reaction conditions generally adopted for the reductive catalytic fractionalization of lignocellulosic biomasses (lignin-first approach). Catalytic tests were carried out in the presence of simple C1-C3 alcoholic H-donor solvents (methanol, ethanol and 2-propanol) used as such or in mixture with water in the temperature range of 120–240 °C both in the presence or in the absence of molecular hydrogen as reducing agent. Under transfer hydrogenolysis conditions, the Ru/C catalyst was found to be the best performing system in the cleavage of the 4–O–5 etheric CO bond (95 % DPE conversion in 2-propanol at 210 °C after 3 h of reaction) with a less pronounced tendency in hydrogenating the aromatic ring. Upon increasing the water content in the reaction medium, a decrease in the cleavage of the CO bond of DPE together with a higher production of phenolics is observed as a consequence of the reductive hydrolysis reaction occurrence. The best yield in aromatic compounds (52 %) was obtained by using as solvent a water/2-propanol (75:25, v/v) mixture in absence of added molecular hydrogen, with the alcoholic fraction being the in-situ H-source. A lower tendency to undergo to hydrolysis reaction together with a higher production of aromatics is registered in the case of phenethyl phenyl ether and benzyl-phenyl ether. Results are explained in terms of the higher steric hindrance of PPE and BPE with respect to DPE and of the competitive adsorption of arenes arising from hydrogenolysis of etheric β–O–4 and α–O–4 bonds (phenol + ethyl benzene or phenol + toluene) on the Ru/C catalyst surface.

Selective cleavage of ether C-O bond in lignin-derived compounds over Ru system under different H-sources

Selective hydrogenolysis, the aromatic ether C-O bonds under mild conditions, is crucial for the valorization of lignin. In this context, the effects of H2 and solvent on the hydrogenolysis of lignin model compounds over Ru catalysts were explored. With H2 as hydrogen donor, the Ru/AC exhibited the highest activity for converting lignin model compounds into monomeric compounds, whereas H2 led to low selectivity of aromatics. However, isopropanol was the good H-donor solvent, which could provide a large amount of active hydrogen to promote the cleavage of C-O bonds. Additionally, the yield of aromatics in isopropanol was higher than that under H2 atmosphere. It could be ascribed to the fact that isopropanol is the protic solvent which displays Lewis basicity, and is a good H-bond donor and a good H-bond acceptor. The higher electron-releasing inductive effect of isopropanol made it easier to provide active hydrogen. Based on the experiments, the mechanism of benzyl phenyl ether hydrogenolysis in H2 and isopropanol system was presented.

Catalytic performance of modified kaolinite in pyrolysis of benzyl phenyl ether: A model compound of low rank coal

A serials of modified kaolinites were prepared by calcination and further acid treatment and characterized by in-situ XRD, N2 adsorption, NH3-TPD, Py-IR and 27Al MAS-NMR. And their catalytic performance in pyrolysis of methanol/benzyl phenyl ether (MeOH-BPE), a model compound of low-rank coal, were investigated at 400 °C in a fixed-bed reactor to explore the correlation between the structure of modified samples and their catalytic performances. The results show that calcination temperature above 500 °C causes the collapse of kaolinite structure. Further acid leaching facilitates the formation of micropores and mesopores. The calcination of kaolinite leads to the transformation of six-coordinate Al atoms (AlVI) into four and five coordinate species (AlIV and AlV), while the subsequent acid treatment increases the contents of AlIV and AlVI and removes AlV. Total acid sites exhibit a first increase and then decrease tendency with the raising calcination temperature. In the presence of the modified kaolinites, BPE conversion significantly enhances and reaches the highest value of 91.41% over K-A-700 prepared by calcination at 700 °C of kaolinite and further acid leaching. Besides, the maximum content of phenol and toluene is also achieved due to the highest acid sites and AlIV content of K-A-700, which favors the generation of ·H, thus resulting in an obvious inhibition of bibenzyl formation but a significant increase of 2-benzylphenol. In-situ pyrolysis by time-of-flight mass spectrometry suggests that the cleavage of Cal-O bond of BPE to form phenol radicals and benzyl radicals is the primary way, while insufficient ·H results in the formation of dominant product of 2-benzylphenol.

Volatile–char interactions during biomass pyrolysis: Understanding the potential origin of char activity

To understand the potential origin of char activity responsible for volatile evolution during biomass pyrolysis, the interactions between benzyl phenyl ether (BPE, a typical lignin dimer) and pinewood chars prepared under a series of thermal, acidy, and steamy conditions were investigated. The results showed the activity of low-temperature char on BPE conversion was mainly attributed to the surface O-containing functional groups. The BPE conversion decreased as the temperature for char preparation raised, resulting from the elimination of char surface functional groups to a large degree at high temperature. The low activity of high-temperature char on BPE conversion could be recovered by acid-washing to release metal-occupied carbon based active sites (e.g., small aromatic rings), and further promoted by steam activation to modify the surface property and porous structure, finally achieving a full conversion of BPE and high selectivity to the products of phenol and toluene.

An alternative route for boron phenoxide preparation from arylboronic acid and its application for C[sbnd]O bond formation

An efficient synthetic route to benzyl phenyl ether preparation has been successfully developed via a one-pot synthetic protocol utilizing a combination of arylboronic acids, hydrogen peroxide (H2O2), and benzyl halides. The whole procedure consists of two consecutive reactions, formation of boron phenoxide from arylboronic acids and its nucleophilic attack. A simple operation under mild conditions such as room-temperature ionic liquid (choline hydroxide), aerobic environment, and absence of metal- and base-catalysts has been employed. Expansion to utilize benzyl surrogates was also successfully accomplished.

Monometallic Cerium Layered Double Hydroxide Supported Pd-Ni Nanoparticles as High Performance Catalysts for Lignin Hydrogenolysis.

Monometallic cerium layered double hydroxides (Ce-LDH) supports were successfully synthesized by a homogeneous alkalization route driven by hexamethylenetetramine (HMT). The formation of the Ce-LDH was confirmed and its structural and compositional properties studied by XRD, SEM, XPS, iodometric analyses and TGA. HT-XRD, N2-sorption and XRF analyses revealed that by increasing the calcination temperature from 200 to 800 °C, the Ce-LDH material transforms to ceria (CeO2) in four distinct phases, i.e., the loss of intramolecular water, dehydroxylation, removal of nitrate groups and removal of sulfate groups. When loaded with 2.5 wt% palladium (Pd) and 2.5 wt% nickel (Ni) and calcined at 500 °C, the PdNi-Ce-LDH-derived catalysts strongly outperform the PdNi-CeO2 benchmark catalyst in terms of conversion as well as selectivity for the hydrogenolysis of benzyl phenyl ether (BPE), a model compound for the α-O-4 ether linkage in lignin. The PdNi-Ce-LDH catalysts showed full selectivity towards phenol and toluene while the PdNi-CeO2 catalysts showed additional oxidation of toluene to benzoic acid. The highest BPE conversion was observed with the PdNi-Ce-LDH catalyst calcined at 600 °C, which could be related to an optimum in morphological and compositional characteristics of the support.

Hydrosilylation of Allyl Ethers in the Presence of Platinum(II) Immobilized on Polymethylene Sulfide

The reactions of allyl ethyl, allyl butyl, allyl glycidyl, allyl benzyl, and allyl phenyl ethers with 1,1,3,3-tetra-methyldisiloxane in the presence of platinum(II) immobilized on polymethylene sulfide have been studied.

Selective catalytic degradation of a lignin model compound into phenol over transition metal sulfates.

Transition metal salts were employed as the catalysts to improve the selective degradation of the α-O-4 lignin model compound (benzyl phenyl ether (BPE)) in the solvothermal system. The results concluded that most of the transition metal salts could enhance BPE degradation. Among which, NiSO4·6H2O exhibited the highest performance on BPE degradation (90.8%) for 5 h and phenol selectivity (53%) for 4 h at 200 °C. In addition, the GC-MS analysis indicated that the intermediates during BPE degradation included a series of aromatic compounds, such as phenol, benzyl methyl ether and benzyl alcohol. Furthermore, the mechanisms for BPE degradation and phenol selectivity in the NiSO4·6H2O system involved the synergetic effects between the acid catalysis and coordination catalysis, which caused the effective and selective cleavage of the C–O bonds.

Efficient hydrogenolysis of aryl ethers over Ce-MOF supported Pd NPs under mild conditions: mechanistic insight using density functional theoretical calculations

The significant Pd0 content and optimum bonding of the reactant & product (higher adsorption energy of benzyl phenyl ether and lower desorption energy for phenol) are responsible for the exceptional catalytic activity of Pd/Ce-MOF.

Pd/Fe3O4 Nanofibers for the Catalytic Conversion of Lignin-Derived Benzyl Phenyl Ether under Transfer Hydrogenolysis Conditions

Novel magnetite-supported palladium catalysts, in the form of nanofiber materials, were prepared by using the electrospinning process. Two different synthetic techniques were used to add palladium to the nanofibers: (i) the wet impregnation of palladium on the Fe3O4 electrospun support forming the Pd/Fe3O4[wnf] catalyst or (ii) the direct co-electrospinning of a solution containing both metal precursor specimens leading to a Pd/Fe3O4[cnf] sample. The obtained Pd-based Fe3O4 nanofibers were tested in the transfer hydrogenolysis of benzyl phenyl ether (BPE), one of the simplest lignin-derived aromatic ethers, by using 2-propanol as H-donor/solvent, and their performances were compared with the analogous impregnated Pd/Fe3O4 catalyst and a commercial Pd/C. A morphological and structural characterization of the investigated catalysts was performed by means of SEM-EDX, TGA-DSC, XRD, TEM, H2-TPR, and N2 isotherm at 77 K analysis. Pd/Fe3O4[wnf] was found to be the best catalytic system allowing a complete BPE conversion after 360 min at 240 °C and a good reusability in up to six consecutive recycling tests.

Selective hydrogenolysis of lignin-derived aryl ethers over Co/C@N catalysts

Low aromaticity and a large number of oxygen-bridged bonds among the aromatic structural units of lignin make it possible to obtain chemicals directly. A novel Co/C@N catalyst with high activity towards hydrogenolysis of lignin-derived aryl ethers was synthesized according to the pyrolysis process of a predesigned ZIF-67. According to the results of characterization by powder X-ray diffraction (XRD), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), Co was reduced by the carbonized organic linker of ZIF-67, and N was doped into the carbon skeleton of the catalyst. The effects of holding time, temperature, and initial H2 pressure on the catalytic performance of Co/C@N were evaluated in the selective hydrogenolysis of benzyl phenyl ether (BPE). BPE was completely converted and the selectivity of monomer reached to 98.2% under optimized reaction conditions. The Calk-O bond in BPE was first dissociated to form toluene and phenol, and then phenol was rapidly hydrogenated to form cyclohexanol. Furthermore, the Co/C@N catalyst shows high activity for hydroprocessing and selective cleavage of other lignin-derived aryl ethers, including phenylethyl phenyl, diphenyl ether, dibenzyl ether, dinaphthalene ether, guaiacol, anisole and veratrole.

Enhanced Selective Production of Arenes and Regenerating Rate in Aryl Ether Hydrogenolysis over Mesoporous Nickel in Plug-Flow Reactors

Ordered mesoporous nickel (mesoNi) was successfully synthesized with a hard templating method by using KIT-6 ordered mesoporous silica as a template. With small-angle X-ray diffraction (SAXRD), transmission electron microscopy (TEM) and N2 sorption technique, the mesoporous structures of synthesized catalysts were characterized with desired high surface area (84.2 m2·g−1) and narrow pore size distribution. MesoNi exhibited outstanding catalytic cleavage activity for lignin model compounds (benzyl phenyl ether, BPE) with high selectivity of arenes in the flow reactor system. MesoNi also showed higher regeneration rates than non-porous ones, which were confirmed from deactivation and regeneration mechanism studies in the flow reaction system with varied high temperature and pressure. The adsorbed poisoning species on the mesoporous Ni surface were analyzed and phenol could be the main poisoning species. The excellent catalytic cleavage performance of mesoNi originates from their unique mesoporous structure, which offers high surface area and Ni active sites. The outstanding catalytic performance shows that this process provides a promising candidate for improved lignin valorization with general applicability.

Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol.

The reductive cleavage of aryl ether linkages is a key step in the disassembly of lignin to its monolignol components, where selectivity is determined by the kinetics of multiple parallel and consecutive liquid-phase reactions. Triphasic hydrogenolysis of 13C-labeled benzyl phenyl ether (BPE, a model compound for the major β-O-4 linkage in lignin), catalyzed by Ni/γ-Al2O3, was observed directly at elevated temperatures (150-175 °C) and pressures (79-89 bar) using operando magic-angle spinning NMR spectroscopy. Liquid-vapor partitioning in the NMR rotor was quantified using the 13C NMR resonances for the 2-propanol solvent, whose chemical shifts report on the internal reactor temperature. At 170 °C, BPE is converted to toluene and phenol with k1 = 0.17 s-1 gcat-1 and an apparent activation barrier of (80 ± 8) kJ mol-1. Subsequent phenol hydrogenation occurs much more slowly (k2 = 0.0052 s-1 gcat-1 at 170-175 °C), such that cyclohexanol formation is significant only at higher temperatures. Toluene is stable under these reaction conditions, but its methyl group undergoes facile H/D exchange (k3 = 0.046 s-1 gcat-1 at 175 °C). While the source of the reducing equivalents for both hydrogenolysis and hydrogenation is exclusively H2/D2(g) rather than the alcohol solvent at these temperatures, the initial isotopic composition of adsorbed H/D on the catalyst surface is principally determined by the solvent isotopic composition (2-PrOH/D). All reactions are preceded by a pronounced induction period associated with catalyst activation. In air, Ni nanoparticles are passivated by a surface oxide monolayer, whose removal under H2 proceeds with an apparent activation barrier of (72 ± 13) kJ mol-1. The operando NMR spectra provide molecularly specific, time-resolved information about the multiple simultaneous and sequential processes as they occur at the solid-liquid interface.