Saturation Of Aromatic Rings Research Articles

Identification of electron-rich mononuclear Ni atoms on TiO2-A distinguished from Ni particles on TiO2-R in guaiacol hydrodeoxygenation pathways

Electron-rich mononuclear Ni atoms located at the oxygen vacancies on TiO2-A are the active sites for selective hydrodeoxygenation of guaiacol to phenolics, while the reduced Ni particles on TiO2-R catalyze hydrogenative aromatic ring saturation.

Compositional differences of fluorescent dissolved organic matter in Arctic Ocean spring sea ice and surface waters north of Svalbard

We assessed the qualitative composition of fluorescent dissolved organic matter (FDOM) in Arctic Ocean surface water and in sea ice north of the Svalbard Archipelago (in the Sophia Basin, the Yermak Plateau and the north Spitsbergen shelf) in May and June 2015, during the “TRANSSIZ” expedition (Transitions in the Arctic Seasonal Sea Ice Zone). Samples collected in open lead waters (OW), under-ice waters (UIW) and from the sea ice (ICE) were analyzed by fluorescence spectroscopy and subsequently by multivariate statistical methods using Parallel Factor Analysis (PARAFAC). Statistical analyses of all measured DOM fluorescence excitation and emission matrices (EEMs) enabled four components to be identified and validated. The spectral characteristics of the first component C1 (λEx/λEm 282(270)/335) corresponded to those of tryptophan. The spectral properties of the other three components corresponded to those of humic-like substances: components two (C2 − λEx/λEm 315(252)/395) and three (C3 − λEx/λEm 357(258)/446) corresponded to humic-like substances of marine origin, whereas component four (C4 − λEx/λEm 261(399)/492) resembled terrestrial humic-like substances. Changes in FDOM composition were recorded in OW, in contrast to UIW and sea ice. In the OW the sum of fluorescence intensities of humic-like components (C2, C3 and C4) was two times higher than the fluorescence intensity of protein-like component (C1). Component C2 exhibited the highest fluorescence intensity. In the UIW and particularly in the sea ice the fluorescence intensity of the protein-like component, IC1, was the highest. The IC1 in the sea ice increased toward the sea ice bottom, reaching maximum values at the sea ice-water interface. The calculated spectral indices (SUVA(254) and HIX) and ratios of fluorescence intensities of protein-like to humic-like components, Ip/Ih, suggested that FDOM in water and sea ice was predominantly autochthonous, characterized by low molecular weight organic compounds and low aromatic ring saturation. Enrichment factors Dc, calculated from salinity-normalized values of the optical DOM properties and dissolved organic carbon concentrations, indicated the significant fractionation of FDOM in the sea ice relative to the parent open waters. The humic-like terrestrial component C4 was enriched the least, whereas the protein-like component C1 was enriched the most. A statistically significant (p < 0.0001) and relatively strong (R = 63) correlation between IC1 and the total chlorophyll a concentration Tchla was found in the sea ice, which suggests that sympagic algal communities were producers of the protein-like FDOM fraction.

DFT insights in to the hydrodenitrogenation behavior differences between indole and quinoline

The hydrodenitrogenation behavior differences between indole and quinoline were investigated using density functional theory calculation to explain the phenomena of previous experimental results. Theoretical calculation was carried out to explain the results using GGA-RPBE function with dispersion force correlation. The process of hydrogenation of indole, quinoline and 1,2,3,4-tetrahydroquinoline as well as denitrogenation of o-ethylaniline and o-propylaniline were conducted on a NiMoS nanocluster. The results suggest Ni-S-Edge is suitable for hydrogenation saturation of aromatic rings of nitrogen compounds and Ni-Mo-Edge is responsible for hydrogenolysis of C–N bond via E2 path. Besides, indoline could be directly converted to o-ethylaniline, whereas the C–N bond of 1,2,3,4-tetrahydroquinoline could only be broken after complete saturation of the aromatic ring. The reason is that the N atom and CC bond of indoline could be coplanar and well adsorbed on Ni-Mo-Edge simultaneously, which is beneficial to reduce the activation energy of C–N bond cleavage.

Hybridization of ZSM‐5 with Spinel Oxides for Biomass Vapour Upgrading

AbstractIn this study, we report catalytic fast pyrolysis of biomass using multifunctional hybrid spinel‐oxide@zeolite catalysts prepared by using the steam‐assisted crystallization (SAC) method to create the mesoporous zeolite followed by urea hydrolysis of metal nitrates to deposit spinel‐oxides. This hybrid catalyst was quite effective in the deoxygenation of pinewood sawdust pyrolysis vapours, while avoiding over cracking of the lignin precursors, which are already ideal as chemical and fuel precursors. In the first step, multiple spinel oxides MgB2O4 (where B=Fe, Al, Ce, Ga, Cr) were screened as catalysts for the pyrolysis of pinewood sawdust and the resultant bio‐oil (bio‐oil on the water‐free basis) was assessed in terms of carbon efficiency, oxygen content and chemical composition. While all the tested spinel oxides deoxygenated the pyrolysis vapour, MgAl2O4 and MgFe2O4 were found to provide a well‐balanced deoxygenation degree and producing bio‐oil with acceptable carbon efficiency. Catalytic activity and product distribution were affected by the density and strength of the acid sites of the spinel oxides. Subsequently, CFP over MgFe2O4@ZSM5 and MgAl2O4@ZSM5 was investigated under similar condition. The better performance of the hybrid catalyst was attributed to the deposition of small particles of MgFe2O4 in the external surface of the zeolite. The presence of this spinel oxide on the external surface depolymerized bulky oxygenates to lighter fractions that could easily access the active sites within the mesoporous structure of the zeolite, thus providing the catalytic function needed for the oxygen removal after aromatic ring saturation.

Electrocatalytic Hydrogenation of Guaiacol Using a Slurry Reactor with Carbon-Supported Platinum Catalyst in Different Aqueous Electrolytes

An ideal upgrading process of biomass derivatives into renewable chemicals/fuels aims for energy densification and carbon emission neutrality. This work focuses on the reductive upgrading of lignin model compounds, namely guaiacol and phenol, using electrocatalytic hydrogenation (ECH). Compared to the classic thermal hydrogenation process, ECH offers some advantages, in terms of greener hydrogen gas (internally supplied from water oxidation), milder operating conditions (lower temperature and pressure, elimination of typical catalyst deactivation due to coking), cleaner process (possibility of integration with solar and/or wind energy, which are renewable and becoming more economical sources of electricity), and simpler operation (controlled by current/voltage input). In this work, ECH of guaiacol was performed in a stirred slurry reactor (SSR) configuration of an H-type cell using Pt/C catalyst. Different pairs of aqueous electrolytes (as catholyte-anolyte combinations), including acid (0.2 M H2SO4), neutral (0.5 M NaCl), and base (0.2 M NaOH) were tested using chronocoulometry, showing that the choice of anolyte has a significant impact on the electron transfer and the reduction rates. Acidic anolyte is preferable for the ECH of phenolics due to the highest proton concentration and specific conductance, whereby the acid-acid and neutral-acid electrolytes were found to be the most effective pairs, resulting in high guaiacol conversion (80–92%) at reasonable current efficiencies (40–62%) after 4 h reaction. The two major products were cyclohexanol (yield: 34–44%) and 2-methoxycyclohexanol (yield: 23–37%) indicating the effective aromatic ring saturation. The hydrogenation rates can be increased by increasing the cathode potential and/or by using higher acid concentration. Increasing the applied voltage contributed to faster reduction at the expense of current efficiency. High conversion of guaiacol (91%) was achieved using HClO4 (0.5 M) as both anolyte and catholyte at -1.0 V (vs. Ag/AgCl) and 34 oC, resulting in 54% cyclohexanol selectivity at moderate current efficiency (53%). A parametric study of guaiacol ECH was carried out using a jacketed cell and the variables were: acid concentration (0.2–1.0 M), superficial current density (110–255 mA cm-2), and temperature (30–60 oC). The current efficiency increased with the acid concentration and temperature; but decreased at the higher superficial current densities due to the enhanced hydrogen evolution reaction. Interestingly, at higher temperature (60 oC), the deoxygenation route was more favored than the ring saturation route, as indicated by the higher cyclohexanone and the lower 2-methoxycyclohexanol yields compared to those obtained at lower temperature (30–40 oC). The present study aims to contribute to the development of a mild electrochemical reduction process for catalytic conversion of lignin-derived substrates (e.g., phenolic compounds). Figure 1

Liquid-phase hydrodeoxygenation of lignin-derived phenolics on Pd/Fe: A mechanistic study

Abstract Although Pd/Fe bimetallic catalysts have been extensively studied in vapor-phase hydrodeoxygenation of phenolics (i.e., guaiacol, cresol), little is yet known about their performance in liquid-phase reactions. In this work, we present a mechanistic study on the Pd/Fe bimetallic catalysts in liquid-phase hydrodeoxygenation of phenolics. The role of tautomerization in hydrodeoxygenation of the lignin-derived phenolics, particularly for ring saturation, is systematically studied by employing two representative modeling compounds: phenol (a molecule that is keto-enol tautomeric) and diphenyl ether (a molecule that does not allow ketol-enol tautomerization). It was found that although the addition of oxyphilic Fe inhibits the direct aromatic ring saturation reaction typically occurring on Pd, tautomerization opens another reaction pathway toward ring saturation products (i.e. cyclohexanone, cyclohexanol, cyclohexane et al.), where both tautomerization and the hydrogenation of keto isomers are significantly enhanced to produce cyclohexanol followed by direct hydrogenolysis of the cyclohexanol to cyclohexane.

Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen-Containing Compounds in the Hydrotreating Process of a Low-Temperature Coal Tar

A low-temperature coal tar was subject to a three-stage catalytic hydrotreating reactor. The raw coal tar and its hydrotreating products from each reactor section were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The removal efficiencies of sulfur, nitrogen, and oxygen were 99.4%, 88.4%, and 78.1%, respectively. The molecular transformation routes of each heteroatomic species are different. Sulfur species were removed from low double bond equivalence (DBE) values to higher values through the whole hydrotreating process. Furanic compounds and basic nitrogen compounds carried out the saturation of aromatic rings before the hydrogenation of low DBE species. Neutral nitrogen compounds were resistant in the processing and cannot be removed completely in the end of the hydroprocessing. The phenolic compounds were the most resistant to hydrotreating during the whole process. The transformation capabilities of heteroatom compounds in the p...

Ni/Al2O3 Catalysts Derived from Layered Double Hydroxide and Their Applications in Hydrodeoxygenation of Anisole

AbstractThe catalytic performance of Ni/Al2O3 catalysts derived from layered double hydroxide precursors with nickel ions incorporated into the brucite‐like layers was investigated for the hydrodeoxygenation (HDO) of anisole as a model compound of the lignin. Upon calcination and subsequent reduction, the well‐crystallized phase and highly dispersed Ni nanoparticles (3∼10 nm) on the support were obtained. The catalysts exhibited high activity toward the hydrogenolysis of C−O bonds and the hydrogenation saturation of aromatic ring at low temperature (200‐280 °C) and appropriate hydrogen pressure (2 MPa). The activity and selectivity of these two main reaction pathways of anisole conversion were independent of the Ni content. And the direct cleavage of Caromatic‐O bond of anisole forming benzene as another parallel pathway prevails at increasing temperature. In addition, the catalysts are highly resistant to coking and easy to be reactivated by the utilization of the layered double hydroxide precursors.

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.

Performance of facet-controlled Pd nanocrystals in 2-ethylanthraquinone hydrogenation

The Pd (100) facet is more active than Pd (111) in CO hydrogenation but less active in saturation of aromatic rings.

Synergistic Catalysis between Pd and Fe in Gas Phase Hydrodeoxygenation of m-Cresol

In this work, a series of Pd/Fe2O3 catalysts were synthesized, characterized, and evaluated for the hydrodeoxygenation (HDO) of m-cresol. It was found that the addition of Pd remarkably promotes the catalytic activity of Fe while the product distributions resemble that of monometallic Fe catalyst, showing high selectivity toward the production of toluene (C–O cleavage without saturation of aromatic ring and C–C cleavage). Reduced catalysts featured with Pd patches on the top of reduced Fe nanoparticle surface, and the interaction between Pd and Fe, was further confirmed using X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and X-ray absorption near edge fine structure (XANES). A possible mechanism, including Pd assisted H2 dissociation and Pd facilitated stabilization of the metallic Fe surface as well as Pd enhanced product desorption, is proposed to be responsible for the high activity and HDO selectivity in Pd–Fe catalysts. The synergic catalysis derived from Pd–Fe interaction found in this work was proved to be applicable to other precious metal promoted Fe catalysts, providing a promising strategy for future design of highly active and selective HDO catalysts.

Hydrodeoxygenation of Dibenzofuran Over SBA-15 Supported Pt, Pd, and Ru Catalysts

Hydrodeoxygenation (HDO) of dibenzofuran (DBF) has been carried out over mesoporous silica SBA-15 supported Pt, Pd, and Ru catalysts. The HDO of DBF went through hydrogenation of aromatic rings first, followed by hydrogenolysis of the saturated C–O bond to produce hydrocarbons. The detection of intermediate 2-cyclohexylcyclohexanol over as-prepared Pt catalysts illustrated that the aromatic ring-containing hydrogenated species transformed to the major deoxygenated product bicyclohexane after elimination of the heteroatom oxygen. Among all three catalysts, the Pt/SBA-15 catalysts exhibited the highest hydrogenation activity to yield aromatic ring-containing hydrogenated products. However, the Ru catalysts were more efficient in formation of completely deoxygenated products. Meanwhile, more cleavage of the saturated C–O bond took place at higher reaction temperature in the HDO of DBF. The increase of hydrogen pressure promoted the saturation of aromatic rings with an obvious influence on the conversion of DBF.

Mild catalytic pyrolysis of biomass for production of transportation fuels: a techno-economic analysis

A techno-economic analysis of mild catalytic pyrolysis (CP) of woody biomass followed by upgrading of the partially deoxygenated pyrolysis liquid is performed to assess this pathway's economic feasibility for the production of hydrocarbon-based biofuels. The process achieves a fuel yield of 17.7 wt% and an energy conversion of 39%. Deoxygenation of the pyrolysis liquid requires 2.7 wt% hydrogen while saturation of aromatic rings in the pyrolysis liquid increases total hydrogen consumption to 6.4 wt%. Total project investment is $457 million with annual operating costs of $142 million for a 2000 metric ton per day facility. A minimum fuel selling price (MFSP) of $3.69 per gal is estimated assuming 10% internal rate of return. Twenty-nine percent of the capital outlay is the result of including a co-generation system to consume heat generated from burning part of the off-gases from pyrolysis and upgrading and all of the coke during regeneration of catalysts. Forty-five percent of the MFSP arises from the cost of biomass feedstock. Hydrogen required for the upgrading process is generated using the balance of the process off-gases. The analysis reveals that an optimum design would include a cogeneration unit; however using natural gas for hydrogen generation is more favorable than using process off-gases as the feed. An uncertainty analysis indicates a probable fuel price of $3.03 per gal, demonstrating the potential of the CP pathway as an alternative to petroleum-derived transportation fuels.

Catalytic hydrogenation of substituted 15β-Pregn-16-enes

The catalytic hydrogenation of 15-benzoyloxybutyl-20-hydroxymethylpregn-16-enes under various conditions was studied. It was shown that at the use of a palladium catalyst along with the reduction of the double bond also its shift occurred giving Δ14-derivatives. The reduction over a platinum catalyst is accompanied by the saturation of aromatic ring of the protecting group, but gives the best yield of the desired products and provides a preparative approach to 15-substituted analogs of brassinosteroids. The structures of the obtained compounds were proved by two-dimensional NMR spectroscopy and HPLC-MS.

Theoretical and Spectroscopic Study of the Effect of Ring Substitution on the Adsorption of Anisole on Platinum

The adsorption of anisole, 3,5-dimethylanisole, and 3,5-bis-(trifluoromethyl)-anisole on Pt(111) was studied theoretically and compared to the adsorption of benzene using relativistically corrected density functional theory. A cluster of 31 platinum atoms was used to simulate the surface. The three anisoles were found to be less strongly adsorbed than the parent molecule benzene, 3,5-bis-(trifluoromethyl)-anisole showing weakest adsorption, with an adsorption energy of only one-third that of benzene. The theoretical study was complemented by in situ ATR-IR spectroscopy of the adsorption of the anisole derivatives on a polycrystalline Pt film. The spectroscopic study indicated that the adsorption strength of the anisoles follows the same order as predicted by the calculations. In addition, catalytic hydrogenation tests showed that the propensity to aromatic ring hydrogenation can also be correlated to the mode and strength of adsorption of the anisoles. The degree of saturation followed the same order as the adsorption strength found by the calculations and indicated by spectroscopy. Although 3,5-dimethyl substitution on anisole resulted in only a partial loss of adsorption energy and reactivity toward ring hydrogenation as compared to anisole, the substitution by CF(3) groups led to a large loss of adsorption energy and complete loss of reactivity toward aromatic ring saturation. Along with the study of the substituent effect on the adsorption of aromatic molecules, the correlation between adsorption and propensity to saturation of aromatic substrates could be corroborated.

The role of substituents ofar-turmerone for its anticancer activity

For the evaluation of the role of substituents ofar-turmerone for its anticancer activity, ar-turmerone (1a) and its analogs like 2-methyl-6-(4′-methyphenyl)-2-octen-4-one (1b), 2-methyl-6-phenyl-2-hepten-4-one (1c), 2-methyl-6-phenyl-2-octen-4-one, (1d), and 2-methyl-6-(trans-4′-methylcyclohexyl)-2-hepten-4-one (1e) were prepared and their cytotoxic activities against L1210 cell were determined. Omission of methyl group atpara-position dose not variate the cytotoxicity of ar-turmerone. Elongation of alkyl group at 6-position decreases ED50 value. Saturation of aromatic ring of ar-turmerone markedly decreases the cytotoxicity. Therefore the smaller size of alkyl group at 6-position and aromatic ring of ar-turmerone should be essential for exhibiting its anticancer activity.

Effect of temperature and hydrogen partial pressure on the hydrogenolysis reaction of model compounds

The hydrogenolysis reaction of dibenzyl and benzyl phenyl ether has been studied varying temperature and hydrogen partial pressure. The increase in hydrogen partial pressure suppressed the formation of condensation products and accelerated the hydrogenation of aromatic ring, dehydroxylation and splitting the central CC or CO bonds. The increase in temperature firstly caused the saturation of aromatic ring and splitting of central bonds, then accelerated dehydroxylation. At higher temperatures the hydrogenation of aromatic rings was suppressed.

Composition of an SRC-II coal-derived liquid: Changes in composition resulting from hydrotreatment at different levels of severity

An SRC-II coal-derived liquid fuel and eight upgraded coal liquids derived from it were separated into chemical class-type fractions by preparative liquid chromatography. Mass and infrared spectroscopy, gas chromatography and non-aqueous titration were used, together with the mass balance data from the l.c. separations, to describe changes in composition of the liquids as a function of severity of hydrotreating conditions. The relative abundance of the following classes of compounds was determined in each of the liquids : saturates, monoaromatics, diaromatics, polyaromatics, total acids, total bases, hydroxyarenes, strong acids, pyrrolic benzologs, carbonyl compounds (amides), basic diarylamines, basic monoarylamines, azaarenes, and strong bases. The results are discussed in the light of known reaction pathways for aromatic ring saturation and heteroatom removal.

Pressure and temperature effect on the mean chemical structure of coal hydrogenolysis product

The hydrogenolysis reaction of coal using red-mud and sulphur as catalyst has been carried out at 400 and 450 °C, 10 MPa or 3 MPa of hydrogen, and 3 MPa of hydrogen plus 7 MPa of nitrogen. The mean chemical structures of the asphaltenes and oils produced show that at first the portion with relatively fewer aromatic rings and more aliphatic structures becomes soluble because of the saturation of the aromatic rings, and then gradually that having more aromatic rings and less of the aliphatic structures does likewise. The higher pressure contributes more to the saturation of aromatic rings and yields more extract. The higher temperature causes thermal decomposition of the aliphatic structures without changing the aromatic structures. When only the total reaction pressure is high, though the hydrogen density is unchanged, the chemical structure of the product is the same, but the reaction rate is accelerated because the reaction proceeds to a greater extent in the liquid state by the suppression of vaporization of low-molecular-weight matter under the higher pressure.

Mechanism of hydrogenation of coal-derived asphaltene

Use of asphaltene instead of the parent coal as the starting material for hydrogenolysis makes it easier to discuss the reaction mechanism, because the mean chemical structures of both reactant and products can be deduced from structural analysis. In this study asphaltene from Japanese Akabira coal was hydrogenated at 400 or 370 °C under initial pressures of 9.8 or 10.4 MPa using red-mud and sulphur catalyst. The structures of the products (oil and remaining asphaltene) and of the original asphaltene were analysed statistically by n.m.r. data. Most of the conversion of asphaltene to oil was caused by saturation of aromatic rings, decomposition of naphthenic rings, dehydroxylation and the decrease of inert ( O + N + S) elements resulting from the opening of hetero-rings; the splitting of linkages between unit structures did not contribute to the conversion.