Conversion Of Benzyl Phenyl Ether Research Articles

ZnIn2S4-Catalyzed Anodic Direct Electrochemical Oxidative Cleavage of C-O Bonds in Alpha-O-4 Linkage in an Aqueous Environment

Electrochemical selective oxidative cleavage of biomass-derived lignin feedstocks, such as C-O bond, into high-value oxygenated fine chemicals and pharmaceutical products offers an emerging route for biomass valorization. Here, we developed an efficient anodic valorization of α-O-4 lignin model compound benzyl phenyl ether (BPE) to the desirable monoaromatics products via the C-O bond direct cleavage at ZnIn2S4 anode under +1.6-2VAg/AgCl supply. A series of carbon-supported ZnIn2S4 electrodes with different hexagonal and rhombohedral phase distributions were carefully controlled and exhibited over 99% BPE conversion with specific C-O bond selectivity. We then studied substrate competition to compare the electrocatalytic performance of different ZnIn2S4 crystal phases. The experimental results were supported by density functional theory calculations. The substrate scope study revealed the suitability of the R-ZIS induced electrocatalytic system for a variety of substituted lignin α-O-4/β-O-4 model dimers. Overall, this work provides an efficient electrode and approach for enabling atom-efficient electro-refinery of diverse lignin-derived oxygenated chemicals.

Mechanocatalytic Hydrogenolysis of the Lignin Model Dimer Benzyl Phenyl Ether over Supported Palladium Catalysts.

This work demonstrates the mechanocatalytic hydrogenolysis of the ether bond in the lignin model compound benzyl phenyl ether (BPE) and hardwood lignin isolated by hydrolysis with supercritical water. Pd catalysts with 4 wt % loading on Al2O3 and SiO2 supports achieve 100% conversion of BPE with a toluene production rate of (2.6-2.9) × 10-5 mol·min-1. The formation of palladium hydrides under H2 gas flow contributes to an increase in the turnover frequency by a factor of up to 300 compared to Ni on silica-alumina. While a near-quantitative toluene yield is obtained, some of the phenolic products remain adsorbed on the catalyst.

Mild hydrogenolysis of lignin model compound and organosolv lignin over non-noble bimetallic Ni–Fe/TiN catalyst

Lignin is one of the most promising feedstocks for renewable aromatics production. Conversion of such feedstock into aromatics can be attained through catalytic hydrogenolysis. In this work, NixFey/TiN bimetallic catalysts were evaluated in the hydrogenolysis of both: (i) benzyl phenyl ether (BPE) as a model compound for lignin and (ii) real organosolv lignin feedstock under low temperature (150 °C) and low H2 pressure (12 bar). All bimetallic catalysts exhibited superior performance over single-component materials and were shown to compose of uniformly/highly dispersed and intimately mixed Ni and Fe nanoparticles. Among bimetallic materials, Ni5Fe2/TiN possesses the highest activity in BPE hydrogenolysis, which is comparable to that of a 5% Pd/C commercial catalyst while showing significantly higher aromatic selectivity. Ni5Fe2/TiN catalyst also outperformed Pd/C in hydrogenolysis of organosolv lignin, shown by its higher oil yield, greater content of phenolic monomers, and lower content of dimers. This material exhibited good stability in BPE conversion with no noticeable deactivation over 5 recycling cycles. XANES analysis suggests the electron transfer from Ni to Fe, which explains the superior activity observed with Ni5Fe2/TiN.

Conversion of benzyl phenyl ether to monoaromatics in high-temperature aqueous ethanol solution under high-pressure carbon dioxide conditions

Solvolysis of benzyl phenyl ether, which is a model compound of lignin ether linkage, was performed in an aqueous ethanol solution, which can be obtained from bioethanol, under high-pressure carbon dioxide conditions.

Selective cleavage of C–O bond in lignin and lignin model compounds over iron/nitrogen co-doped carbon supported Ni catalyst

The utilization of lignin to produce high value-added chemicals is conducive to alleviating the fossil energy crisis. Herein, Ni nanoparticles supported on iron/nitrogen co-doped carbon was prepared by co-pyrolysis and solvothermal reduction method for catalytic hydrogenolysis (CH) of dealkaline lignin and its model compounds. The catalysts were prepared under different calcination temperature, N/C ratio and Ni loading, and the optimal catalyst was Ni10%@Fe/NC0.33–800 (calcination temperature: 800 °C, N/C ratio: 0.33, Ni loading: 10%) based the on the CH of benzyl phenyl ether (BPE). Ni10%@Fe/NC0.33–800 showed good catalytic performance on the selective cleavage of C-O bond of lignin and its model compounds. The BPE conversion reached up to 97.7% over Ni10%@Fe/NC0.33–800 under mild conditions (230 °C, 1 MPa H2, and 0.5 h) with toluene and cyclohexanol as major products. Catalyst characterizations suggest that N content affects the formation of NiFe alloy and the synergistic effect between Ni and Fe plays an important role in CH of BPE. Moreover, Ni10%@Fe/NC0.33–800 could promote the cleavage of C-O bonds in dealkaline lignin through CH and hence enhance producing aromatics such as phenols, aromatic ethers, and aromatic esters, among which phenols are the main aromatics with guaiacols predominant.

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.

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.

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.

Transfer hydrogenolysis of aromatic ethers promoted by the bimetallic Pd/Co catalyst

The transfer hydrogenolysis of lignin derived aromatic ethers (benzyl phenyl ether, phenethyl phenyl ether and diphenyl ethers) have been investigated by using the coprecipitated Pd/Co as heterogeneous catalyst and 2-propanol as H-donor/solvent. A quantitative conversion of benzyl phenyl ether into toluene and cyclohexanol was obtained after 180 min at 240 °C. The bimetallic Pd/Co catalyst is, by far, more efficient if compared to commercial Pd/C and Co-based catalytic systems showing, at the same time, a good reusability. The enhanced ability in the CO bond cleavage in aromatic ethers is related to the formation of bimetallic Pd-Co ensembles, arisen from the preparation procedure adopted, as confirmed by a complete physico-chemical characterization that includes XRD, SEM, TEM, H2-TPR, XPS and EXAFS analysis.

Selective cleavage of C[sbnd]O bond in benzyl phenyl ether over Pd/AC at room temperature

Selectively cleaving the CO bonds in lignin to produce aromatic products are challenging problems. Currently, catalytic hydrogenolysis of CO bonds in lignin requires harsh conditions. Herein, selectively cleaving CO bond of benzyl phenyl ether (BPE) was studied over Pd/AC, Ru/AC and Ni/AC. Among these catalysts, Pd/AC efficiently cleaved CO bond in BPE under super mild conditions (25 °C, 2 h and 0.1 MPa H2). The products were toluene and phenol without hydrogenation of the aromatic ring. The main competitive step of hydrogenolysis and hydrogenation is sensitive to reaction temperature over Pd catalyst. A mild temperature is preferred for hydrogenolysis, since the H species nearby the oxygen atom are more strongly adsorbed than nearby the benzene rings. With the different H-donor solvents, the highest conversion of BPE was obtained in isopropanol. Based on the experiments, the reactions occurred via cleavage of the Caliphatic-O bond in BPE and the synergetic effects between the H from absorbed H2 on the surface of the Pd and the intermediates radicals of benzyl and phenoxy should be the key points to such an optimum result.

Temperature Tuning the Catalytic Reactivity of Cu-Doped Porous Metal Oxides with Lignin Models

Reported are the temperature dependencies of the temporal product evolution for lignin model compounds over copper-doped porous metal oxide (CuPMO) in supercritical-methanol (sc-MeOH). These studies investigated 1-phenylethanol (PPE), benzyl phenyl ether (BPE), dihydrobenzofuran (DHBF), and phenol over operating temperature ranges from 280 to 330 °C. The first three model compounds represent the β-O-4 and α-O-4 linkages in lignin as well as the furan group commonly found in the β-5 linkage. Phenol was investigated due to its key role in product proliferation as noted in earlier studies with this Earth-abundant catalyst. In general, the apparent activation energies for ether hydrogenolysis proved to be significantly lower than that for phenol hydrogenation, a major side reaction leading to product proliferation. Thus, temperature tuning is a promising strategy to preserve product aromaticity as demonstrated by the more selective conversion of BPE and PPE at lower temperatures. Rates of methanol reforming o...

Decomposition of lignin model compounds by Lewis acid catalysts in water and ethanol

The conversion of benzyl phenyl ether, diphenyl ether, diphenyl methane and biphenyl as representative model compounds for α–O4, 5–O4, α 1 (methylene bridges) and 5–5′ lignin linkages was investigated. We compared the use of metal chlorides and acetates. The reactions were studied in sub- and supercritical water and supercritical ethanol between 300 and 400°C. At low temperature in water, Lewis acids mainly catalyzed condensation of hydrolysis products of the dimeric model compounds. At higher temperature, mono-aromatic products were formed. The yield of monomeric products was higher in ethanol than in water. The preference for ethanol is due to extensive alkylation of the mono-aromatic products, which inhibits their condensation into larger products. The highest yields of deoxygenated mono-aromatics were obtained using Lewis acid catalysts at 400°C in supercritical ethanol. The preferred Lewis acid catalysts were Fe, Cu, Ni and Al chlorides.

Selective cleavage of C[sbnd]O bond in benzyl phenyl ether to aromatics over Pd–Fe bimetallic catalyst supported on ordered mesoporous carbon

Bimetallic Pd–Fe catalyst supported on ordered mesoporous carbon (Pd–Fe/OMC) was prepared by a surfactant-templating method and a subsequent incipient wetness impregnation method. The catalyst was applied to the catalytic cleavage of CO bond in benzyl phenyl ether to aromatics. For comparison, monometallic Pd/OMC and Fe/OMC catalysts were also investigated. Benzyl phenyl ether was used as a lignin model compound for representing α-O-4 linkage in lignin. The combined effect of palladium and iron on the physicochemical properties and catalytic activities of Pd–Fe/OMC was investigated. Although Pd/OMC catalyst showed the highest conversion of benzyl phenyl ether, selectivity for aromatics was low due to saturation of aromatic ring. On the other hand, Fe/OMC catalyst showed lower conversion of benzyl phenyl ether than Pd/OMC, but Fe/OMC catalyst showed higher CO bond cleavage selectivity than Pd/OMC catalyst without saturation of aromatics. Bimetallic Pd–Fe/OMC catalyst showed the highest yield for aromatics. The introduction of Fe into Pd/OMC catalyst resulted in the modification of electronic properties of Pd by electron transfer from Fe to Pd, which led to the enhanced yield for aromatics.

Production of high carbon number hydrocarbon fuels from a lignin-derived α-O-4 phenolic dimer, benzyl phenyl ether, via isomerization of ether to alcohols on high-surface-area silica-alumina aerogel catalysts

Two-step hydrodeoxygenation of benzyl phenyl ether (BPE), a lignin-derived phenolic dimer containing an α-O-4 linkage, was performed to produce high carbon number saturated hydrocarbons. The ether linkage of BPE was first isomerized to alcohols of benzylphenols on the solid acid catalysts of silica (SA), alumina (AA), and silica-alumina aerogels (SAAs), which were further hydrodeoxygenated to saturated cyclic hydrocarbons on a silica-alumina-supported Ru catalyst. During the isomerization of BPE, noble-metal-free catalysts suppressed the formation of phenyl monomers but produced the phenolic dimers. SA, AA, and SAA-73 (Al/(Si+Al)=0.73) exhibited negligible activity. However, SAA-38 and SAA-57 containing Al/(Si+Al) contents of 0.38 and 0.57, respectively, exhibited high catalytic activity among the prepared aerogel catalysts. The BPE conversion on SAA-38 reached 100% at a temperature range of 100-150°C. The Brönsted acid sites appear to be catalytic active sites. On the basis of the predominant isomerization of phenyl ether to phenols over ether decomposition on the SAAs, the following second step of hydrodeoxygenation (HDO) after the first step of isomerization of BPE produced deoxygenated C13–19 cyclic hydrocarbons, as opposed to the saturated deoxygenated cyclic hydrocarbons produced trhough a one-step reaction process with silica-alumina-supported Ru catalysts, demonstrating this to be a promising process for producing high carbon number hydrocarbons from lignin dimers and oligomers.

Catalytic decomposition of benzyl phenyl ether to aromatics over cesium-exchanged heteropolyacid catalyst

Cesium-exchanged Cs x H3.0−x PW12O40 (X=2.0–3.0) heteropolyacid catalysts were prepared and applied to the decomposition of benzyl phenyl ether to aromatics. Benzyl phenyl ether was chosen as a lignin model compound for representing α-O-4 bond in lignin. Phenol, benzene, and toluene were mainly produced by the decomposition of benzyl phenyl ether. Conversion of benzyl phenyl ether and total yield for main products (phenol, benzene, and toluene) were closely related to the surface acidity of Cs x H3.0−x PW12O40 (X=2.0–3.0) heteropolyacid catalyst. Conversion of benzyl phenyl ether and total yield for main products increased with increasing surface acidity of the catalyst. Among the catalysts tested, Cs2.5H0.5PW12O40 with the largest surface acidity showed the highest conversion of benzyl phenyl ether and total yield for main products.

Influence of alkali carbonates on benzyl phenyl ether cleavage pathways in superheated water

Benzyl phenyl ether conversion in superheated water yields a broad product distribution. In addition to the hydrolysis products, phenol and benzyl alcohol, a large amount of consecutive products are formed depending on the operating conditions. The influence of Li2CO3, Na2CO3, and K2CO3 on these reactions is explored between 270 and 370°C. It is shown that high selectivity towards hydrolysis can be achieved at low temperatures and short reaction times. At higher severities the yields of phenol and especially benzyl alcohol decrease and higher molecular weight compounds are formed by consecutive reactions. Alkali carbonates effect this distribution by decreasing the concentration of protons in the system and by providing and enhancing parallel and secondary reaction mechanisms. The yields of toluene, 2 and 4-benzyl phenol are strongly enhanced in the presence of an alkali carbonate, by formation of a cation–BPE adduct in which the ether bond is strongly polarized.

Thermolysis of Benzyl Phenyl Ether in Subcritical and Supercritical Water, and Supercritical Methanol.

The thermolysis of benzyl phenyl ether (BPE) in subcritical and supercritical (SC) water and SC methanol has been studied to investigate the solvent effects on thermolysis of ether compounds in supercritical fluids (SCFs). Experiments were performed at temperatures of 593 and 648 K, over a solvent density range from 2.2 to 21.7 mol/dm 3 , and in the range of reaction period from 180 to 2400 seconds. Reactions in water at 593 K proceeded under subcritical conditions, while all other reactions proceeded under SC conditions. Selectivity for reaction products was determined from the plot of product yield versus BPE conversion. It was found that both pyrolysis and hydrolysis occurred in subcritical and SC water, but only pyrolysis occurred in SC methanol. The lumped elementary reaction model for the reaction in SC methanol proposed by Wu et al. was extended to the reaction in subcritical and SC water by adding therefore hydrolysis reaction. The values of rate constants for such reactions as C-O bond fission, hydrogen abstraction, radical recombination, and hydrolysis were optimized using the multivariable constrained search method. The dependence of rate constants of BPE thermolysis in SCFs on density was discussed.

Influence of supercritical fluid solvent density on benzyl phenyl ether pyrolysis: indications of diffusional limitations

The influence of supercritical solvent density on the pyrolysis of benzyl phenyl ether (BPE) in tetralin and supercritical toluene is interpreted in terms of transport limitations. Reaction at varying toluene densities highlighted the transport dependence of the BPE fission rate constant. The conversion of BPE decreased from 0.55 to 0.15 as the toluene density increased from 0.0 to 0.75. The yield and selectivity of BPE rearrangement products were also density dependent. These results were explained and modeled quantitatively in terms of the cage effect theory

Effect of coal minerals on the thermal treatment of aromatic ethers and carbonyl compounds

To elucidate the effect of mineral matter in coal on coal liquefaction, the thermal decomposition of some model compounds of coal structure, aromatic ethers and carbonyl compounds, has been carried out in tetralin solvent and in the presence of coal ash obtained by low temperature combustion. The conversion of benzyl phenyl ether and dibenzyl ether was considerably enhanced; alkylated products such as benzyltetralin were obtained. The conversion of phenoxyphenanthrene and phenoxynaphthalene also was increased to some extent in the presence of coal ash. These effects can be attributed to the acidic components of coal minerals, because silica-alumina has shown the same effect, which is suppressed by quinoline. The addition of coal ash increases the yield of hydrocarbon from the corresponding aromatic carbonyl compounds by reduction. This effect is attributable to iron sulphide.