Ruthenium Ion-catalyzed Oxidation Research Articles

Study of the composition of high molecular asphaltenes of bituminous oils using ruthenium ion-catalyzed oxidation reaction

Relevance. Conditioned by the need to expand the amount of data on composition and structure of the asphaltene constituents of heavy oils. The data are important for creation of new and modernization of existing technologies for processing unconventional hydrocarbon raw materials. Aim. To study the composition of structural fragments in macromolecules of asphaltenes of bituminous oils from the Ashalchinskoe, Usinskoe, and Nurlatskoe oilfields using the ruthenium ion-catalyzed oxidation. Object. Fractions of high-molecular asphaltenes, which make up the bulk of the asphaltene constituents of the Ashalchinskoe, Usinskoe, and Nurlatskoe oils (94.1; 92.1 and 95.0 rel. %). Methods. Elemental analysis, cryoscopy in benzene, selective chemical destruction of Car–C bonds using a ruthenium ion-catalyzed oxidation, gas chromatography–mass spectrometry. Results. It has been established that the structure of high-molecular asphaltenes of bituminous oils from the Ashalchinskoe, Usinskoe, and Nurlatskoe oilfields contains fragments bound to the core of their molecules through Car.–C bridges and compounds trapped in the hollow cells of macromolecular entities of asphaltenes during kerogen cracking. It follows from the analysis of the oxidation products that the covalently bonded fragments are represented by C8–C32 n-alkanes, branched C9–C30 alkanes (2-methylalkanes and C15, C19, C20 isoprenoids), C22–C24 cheilanthanes, C27, C29–C33 hopanes and long chain alkyl bridges (C9–C30) connecting aromatic blocks. Most of the fragments linked by Car.–C bridges are linear paraffin chains. Typical biological markers, i. e. n-alkanes and hopanes were identified among the occluded compounds.

Comprehensive evaluation of polycyclic aromatic units in three liquefaction-derived heavy fractions from Zhunnan lignite

The structural characteristics of polycyclic aromatic units in three liquefaction-derived heavy fractions from Zhunnan lignite, including thermal dissolution (TD) in cyclohexane (HF C ), ethanolysis (HF E ), and two-step sequential TD in cyclohexane-ethanol (HF CE ), were investigated in depth. Combining multiple destructive tools, the intrinsic correlation among dissociated/degraded fragments and organic macromolecular networks, involving the types of alkyl side chain, methylene bridged bond, heteroatom, and aromatic nucleus, was also constructed. The results indicate that HF C with a smaller average molecular weight may be rich in -OH, >C-O-, and >C O units, while HF CE has higher aromaticity. In addition, abundant arenes and arenols were detected in the volatiles released from HF C flash pyrolysis, but macro/ultramolecular groups dominated in HF E and HF CE . Obviously, the differences in thermochemical reactions further confirmed that the component distribution of volatiles is mainly related to the direct gasification of small/medium molecules and the cleavage of weak/moderate strength covalent bonds. The analyses with quadrupole exactive orbitrap mass spectrometer and ruthenium ion-catalyzed oxidation show that HF C also contains abundant oxynitrides, while HF CE may be dominated by cata -condensed aromatics and polyaryl units, followed by few peri -condensed aromatics, long-chain saturated rings, aromatic rings with longer aliphatic side chains, and polymethylene linkage units. Comprehensive evaluation of these difficult-to-detect parts is beneficial to the resource and diversified utilization of such special soluble portions with potential environmental hazards. • HFCE has the highest aromaticity, while HFC is rich in O-containing FGs. • HFC also contains abundant >C-O- moieties and oxynitrides. • HFCE may be dominated by cata-condensed aromatics and polyaryl units. • The inner link among degraded fragments and organic structures was revealed.

Effect of preoxidation treatment with H2O2 on ruthenium ion-catalyzed oxidation of Yima long flame coal

Environmental concerns have led researches to investigate carbon neutral and sustainable strategies to satisfy well-being of present and future generations, in which coal oxidation becomes a promising approach to achieve this goal. In this study, Yima long flame coal (YLFC) was subjected to ruthenium-ion-catalyzed oxidation (RICO) after peroxidation with H2O2 (PO). The results indicate that the organic matter in YLFC is mainly oxidized into benzenecarboxylic acids, accounting for 70.36% of all the oxidation products, and the yields of the valuable resulting carboxylic acids are significantly elevated by PO from 12.99 wt% to 35.06 wt%, leading to a higher utilization of carbon and lower CO2 emission. Moreover, PO can enhance remarkably the reactivity of the macromolecular precursors of coals, especially highly condensed aromatic species to produce benzenepentacarboxylic acid and mellitic acid more efficiently with a 20-fold increase and 200-fold increase, which is ascribed to the formation of carboxyl groups from other oxygen-containing groups or bonds in coals via PO. The reactive intermediates OH and OOH generated from H2O2 decomposition can attack the carbon atom of alkyl side chains, ether bonds, C=O bonds, and the bridged linkages to undergo a preliminary degradation of macromolecular networks in coals and produce more active sites for the subsequent RICO, leading to the yield and species number increase of carboxylic acids via PO.

Composition of petroleum asphaltenes derived from ruthenium-catalyzed oxidation

Ruthenium ion-catalyzed oxidation of methanonaphthene oil (Krapivinskoye oilfield) revealed that its high molecular asphaltenes contain aromatic–aliphatic bridges and non- covalently bound (occluded) compounds. Covalently bound fragments are represented by C5–C18n-alkanes, aromatic biphenyl-type structures, and naphthalenes located in the peripheral part of asphaltene molecules. Typical biological markers, i.e. terpanes, steranes, and n-alkanes have been identified among the occluded compounds.

Polycyclic Aromatics Observed in Enzymatic Lignin by Spectral Characterization and Ruthenium Ion-Catalyzed Oxidation.

It is generally considered that lignin is a three-dimensional amorphous polymer consisting of methoxylated phenylpropane structures. However, high yields of monomer structural units of lignin cannot be obtained through various ways, which inspired us to gain insights into the structures of lignin. Herein, enzymatic lignin (EL) was directly characterized by a solid-state 13C nuclear magnetic resonance spectrometer and Fourier transform infrared spectrometer and then subjected to ruthenium ion-catalyzed oxidation. According to the spectral characterization, it can be inferred that multi-ring aromatic clusters exist in EL because of the aromatic bridgehead carbon ratio of 0.136. Based on the results of ruthenium ion-catalyzed oxidation of the EL, it can be deduced that (1) double- and triple-aromatic ring clusters exist in the EL besides the traditional phenylpropane single-aromatic ring clusters, and (2) some aromatic rings with long-alkyl chain substituents exist in the EL, which is quite different from the traditional cognition of lignin. This investigation provides a new insight into the structure of EL.

Reusability Investigation of a Ruthenium Catalyst during Ruthenium Ion-Catalyzed Oxidative Depolymerization of Lignite for the Production of Valuable Organic Acids.

A clean and efficient conversion process is essential for the utilization of low-rank coals. Lignite, a typical representative of the low-rank coal family, has huge potential for the production of valuable chemicals via the oxidative depolymerization reaction. Ruthenium ion-catalyzed oxidation (RICO) is an effective route for lignite depolymerization under mild conditions, but the high cost of precious Ru limits the potential large-scale application of RICO. How to recycle and reuse Ru is critical to promote the application of RICO. In this work, a novel and efficient approach for reusing Ru through recycling the solvent mixture containing Ru was established for RICO. First, the influence of different reaction parameters on the depolymerization degree of lignite and benzene polycarboxylic acid (BPCA) yields was investigated. Second, the distribution of Ru in the organic phase (OP), aqueous phase (AP), and residual solid phase (RSP) was analyzed after the RICO reaction. Finally, based on the distribution of Ru in different phases, a novel route of recycling Ru by reusing the Ru-containing solvents was proposed. The results showed that the dosage of RuCl3 and NaIO4 had a significant influence on both the depolymerization degree of lignite and BPCA yields. The distribution of Ru had a close relationship with the depolymerization degree of lignite and the dosage of NaIO4. After the depolymerization reaction, the CCl4 phase containing Ru was reused directly as the solvent for the next run, which could fulfill the reuse of both CCl4 and Ru. The results proved that the Ru-containing CCl4 phase could maintain catalytic performance for 5 runs. This work provides an efficient route to reuse Ru for the RICO depolymerization of lignite into valuable organic acids. As far as we know, this is the first report concerning the recycling and reuse of Ru during the RICO of lignite. This work is important for the application of RICO in lignite depolymerization.

A General Route of Using Lignite Depolymerized Derivatives for Catalyst Construction: Insights into the Effects of the Derivative Structures and Solvents.

Depolymerization is an emerging and promising route for the value-added utilization of low-rank coal (LRC) resources, and how to use the complex depolymerized mixtures efficiently is of great importance for this route. In this work, we designed the rational route of using depolymerized mixtures from lignite via ruthenium ion-catalyzed oxidation (RICO) depolymerization directly without complex separation to construct a Zr-based hydrogenation catalyst. The prepared catalyst was applied into the catalytic transfer hydrogenation of biomass-derived carbonyl compounds. Meanwhile, a copper-based oxidation catalyst was also constructed via a similar route to investigate the universality of the proposed route. Special insights were given into how the depolymerized components with different structures influenced the performances of the catalysts. The effects of the solvents used during the catalyst preparation (H2O and DMF) were also studied. The results showed that the proposed route using the depolymerized mixtures from lignite via RICO to construct catalysts was feasible for both Zr-based and Cu-based catalysts. The two catalysts prepared gave high efficiency for their corresponding reaction, i.e., the Zr-based catalyst for catalytic transfer hydrogenation of biomass-derived carbonyl compounds and the Cu-based catalyst for selective oxidation of alcohols into aldehydes. Different depolymerized components contributed differently to the activity of the catalyst, and the solvents during the preparation process could also influence the activity of the catalyst. The depolymerized components and the solvents influenced the activities of the Zr-based catalyst mainly via changing the Zr contents, the microenvironment of Zr4+, and the specific areas of the catalyst.

Mellitic acid production by ruthenium ion-catalyzed oxidation of cokes

Cokes are rich in highly condensed aromatic rings, however, the current applications of cokes mainly focus on the thermal energy or carbon-rich structures, and the aromatic ring structures in cokes are underutilized, which are usually employed as feedstock to fabricate valuable fine chemicals and synthesized with complex steps. The pyrolysis temperatures have great impact on the structures of resulting cokes. It is necessary to learn about the structural features of cokes produced from different pyrolysis conditions to explore the optimal reaction conditions. This study reported an eco-friendly and efficient method, ruthenium ion-catalyzed oxidation, to utilize Guizhou cokes produced from different pyrolysis temperatures for green and value-added chemical production. The results indicate that arenecarboxylic acids account for more than 90% of all the oxidation products, in which mellitic acid could be up to more than 70%. Compared with previous studies, this is the highest mellitic acid yield achieved in the oxidation products of fossil resources, indicating that cokes show good performance for the clean production of mellitic acid. The ruthenium ion-catalyzed oxidation product distribution demonstrates that 1,200 °C is a turning point during coking of Guizhou coals and the structure and reactivity of Guizhou coke1,200 deviate from the expected variation tendency, which is related to the inverse influence of pyrolysis temperatures on condensation degree and ash property of cokes. Effect of pyrolysis temperatures on aromatic structures and reactivity of Guizhou cokes was also discussed further.

A deep insight into the structural characteristics of Yilan oil shale kerogen through selective oxidation

The structural characteristics of oil shale are important to its application. In this work, a deep insight into the structural characteristics of Yilan oil shale kerogen (YLK) was studied using alkali-oxygen oxidation at different times and ruthenium ion catalyzed oxidation (RICO). The results indicate that YLK is gradually converted to humic acids (HAs), water-soluble acids (WSAs), carboxylic acids (CAs), CO2 and H2O. 13C NMR analyses of YLK, residues and HAs indicate that C–O bonds, especially Car–O bonds of YLK, are easily cleaved. The condensed aromatic rings and long alkyl chains are difficult to be oxidized during the oxidation process. With increasing oxidation time, the molar fraction of aromatic bridgehead carbon (Xb) of YLK and the residues increases from 0.174 to 0.201, and that of HAs increases from 0.225 to 0.267. The result indicates that the aromatic structures of YLK are composed of 1-ring aromatic clusters (26.5%), 2-ring aromatic clusters (67.1%) and 3 or more-ring aromatic clusters (6.4%). Also, the average methylene chain (Cn) of YLK and the residues increases from 2.0 to 5.1, and that of HAs increases from 1.3 to 2.7, indicating that the alkyl chain length is not average but has a distribution. 2.5% methylene carbons exist as long n-alkyl chains in the alkyl side chains groups (SCGs) on the aromatic rings in YLK. The carbon number of SCGs ranges from 5 to 22, and C15 and C17 are predominant. 3.8% methylene carbons exist as alkyl bridges linkages (BLs) connecting aromatic rings in YLK. The carbon number of BLs connecting aromatic rings ranges from 6 to 19, and C8 is predominant. Because of the existence of above long n-alkyl chains, 93.7% methylene carbons in YLK exist as alkyl chains with an average length of 1.84.

Molecular Structure of Heavy Petroleum: Revealed by Molecular Composition of Ruthenium-Ion-Catalyzed Oxidation Products

Ruthenium-ion-catalyzed oxidation (RICO) is an approach for investigating the structure of heavy oils by selectively removing aromatic carbon from petroleum fractions, while leaving the structural ...

Insight into aromatic structures of a middle-temperature coal tar pitch by direct characterization and ruthenium ion-catalyzed oxidation

Aromatic structures dominated in a coal tar pitch (CTP), which play a significant role in the eco-environmental and effective utilization of CTP. Herein, a middle-temperature CTP was directly characterized by multiple instruments including solid-state (SS) 13C nuclear magnetic resonance spectrometer, X-ray photoelectron spectrometer, Fourier transform infraredspectrometer, X-ray diffraction and thermogravimetric analyzer, and then subjected to ruthenium ion-catalyzed oxidation (RICO), which aimed to providing the typical structural features of aromatic structures in CTP. Meanwhile, the carcinogenic polycyclic aromatic hydrocarbons (PAHs) in the CTP were quantitatively analyzed, and the toxicity was evaluated based on different standards. According to the direct characterization, CTP was rich in aromatic carbons, which accounted for 94.9% of total carbons. The average ring number of the aromatic clusters in CTP was 5, and aromatic rings were lowly substituted by methyl. Furthermore, the results from RICO of CTP implied that a series of cycloarylalkane structures exited in CTP. Peri-condensed aromatic structures were the most abundant, while the proportion of cata-condensed and biphenyl type structures were relatively small. This investigation provides a useful method for understanding the aromatic structures in CTP.

A three-step dissociation method for converting Xiaolongtan lignite into soluble organic compounds: Insights into chemicals, geochemical clues, and structural characteristics

Converting lignite into soluble organic compounds (SOCs) under mild conditions is significant for both evaluating molecular structure and producing clean fuels/chemicals. A three-step dissociation, i.e., sequential extraction, sequential thermal dissolution (TD), and ruthenium-ion-catalyzed oxidation (RICO), was adopted to convert the organic matter (OM) in Xiaolongtan lignite (XL) into SOCs. The perspectives on chemicals, geochemical information, and structural characteristics of XL were evaluated based on the molecular compositions of SOCs. Much higher yields of SOCs were obtained from TD than from extraction, which could be attributed to the thermal dissociation of non-covalent interactions in XL. Normal alkanes, alkyl-substituted benzenes, alkyl-substituted phenols, ketones, and aliphatic esters are the main group components released from TD. A series of important biomarkers were released and their distributions and evolution pathways during XL-forming process imply that higher terrestrial plants could be the main input of the OM in XL. Benzenecarboxylic acids were produced from TD residue in high selectivity via the RICO. According to the results from the RICO, the insoluble macromolecular structures in XL are rich in peri-condensed aromatics along with some cata-condensed aromatics and polyaryls, and CH3 is the major alkyl side chain on the aromatic rings. Adjacent aromatic moieties are mainly connected each other directly by CarCar bridged bonds.

Mechanistic Insights into Selective Oxidation of Polyaromatic Compounds using RICO Chemistry.

Ruthenium-ion-catalyzed oxidation (RICO) of polyaromatic hydrocarbons (PAHs) has been studied in detail using experimental and computational approaches to explore the reaction mechanism. DFT calculations show that regioselectivity in these reactions can be understood in terms of the preservation of aromaticity in the initial formation of a [3+2] metallocycle intermediate at the most-isolated double bond. We identify two competing pathways: C-C bond cleavage leading to a dialdehyde and C-H activation followed by H migration to the RuOx complex to give diketones. Experimentally, the oxidation of pyrene and phenanthrene has been carried out in monophasic and biphasic solvent systems. Our results show that diketones are the major product for both phenanthrene and pyrene substrates. These diketone products are shown to be stable under our reaction conditions so that higher oxidation products (acids and their derivatives) are assigned to the competing pathway through the dialdehyde. Experiments using 18 O-labelled water do show incorporation of oxygen from the solvents into products, but this may take place during the formation of the reactive RuO4 species rather than directly during PAH oxidation. When the oxidation of pyrene is carried out using D2 O, a kinetic isotope effect (KIE) is observed implying that water is involved in the rate-determining step leading to the diketone products.

Investigation on the structural feature of Shengli lignite

The extraction residue from Shengli lignite was sequentially dissolved in cyclohexane, benzene, methanol, ethanol, and isopropanol in an autoclave at 320 °C to afford soluble portions (SPs) 1–5 (SP1-SP5) and the final residue (FR). The total yield of SP1-SP5 is ca. 55.1%. The FR was subjected to ruthenium ion-catalyzed oxidation and the resulting products were isolated from the reaction mixture and esterified. Both the esterified products and SP1-SP5 were analyzed with a gas chromatograph/mass spectrometer. In total, 342 compounds were identified in SP1-SP5. They can be classified into normal alkanes, branched alkanes, alkenes, alkanedienes, arenes, alkanols, methylcycloalkanes, alkenols, alkylbenzenemethanols, arenols, anisol and substituted anisols, polymethyldihydrobenzofurans, arenofurans, dibenzofurans, ethoxymethylbenzenes, aldehydes, ketones, esters, nitrogen-containing organic compounds, sulfur-containing organic compounds, and other compounds. Among the compounds, arenols are predominant in SP1 and SP2 and the main compounds in SP3, while the main compounds in SP4 and SP5 are esters and arenes, respectively. According to the esterified products identified, the products from the FR oxidation can be grouped into non-benzene ring carboxylic acids (NBCAs) and benzenepolycarboxylic acids (BPCAs). The total yield of BPCAs is much higher than that of NBCAs, suggesting that the FR is rich in condensed aromatic moieties.

Oxidation of Polynuclear Aromatic Hydrocarbons using Ruthenium‐Ion‐Catalyzed Oxidation: The Role of Aromatic Ring Number in Reaction Kinetics and Product Distribution

Oxidation of aromatic hydrocarbons with differing numbers of fused aromatic rings (2-5), have been studied in two solvent environments (monophasic and biphasic) using ruthenium-ion-catalyzed oxidation (RICO). RICO reduces the aromaticity of the polyaromatic core of the molecule in a controlled manner by selective oxidative ring opening. Moreover, the nature of the solvent system determines the product type and distribution, for molecules with more than two aromatic rings. Competitive oxidation between substrates with different numbers of aromatic rings has been studied in detail. It was found that the rate of polyaromatic hydrocarbon oxidation increases with the number of fused aromatic rings. A similar trend was also identified for alkylated aromatic hydrocarbons. The proof-of-concept investigation provides new insight into selective oxidation chemistry for upgrading of polyaromatic molecules.

Effect of Ethanolysis on the Structure and Pyrolytic Reactivity of Zhaotong Lignite

Lignite ethanolysis is one of the efficient conversion processes. In our previous study, Zhaotong lignite (ZL) from Southwest China was subjected to ethanolysis to afford an ethanol-soluble portion and ethanolyzed residue (ER). The structural features of ZL and ER were investigated by ruthenium-ion-catalyzed oxidation (RICO) and Fourier transform infrared spectrometry. The pyrolytic reactivities of ZL and ER were examined with a thermogravimetric analyzer and Curie-point pyrolyzer–gas chromatograph/mass spectrometer. The results show that both ZL and ER are rich in −CH2CH2– and −CH2CH2CH2– bridged linkages connecting aromatic rings. In comparison to the RICO of ZL, the RICO of ER produced much less long-chain alkanoic and alkanedioic acids, suggesting that long alkylene bridges and alkyl side chains in ZL were largely cleaved via ethanolysis. Interestingly, ZL has a higher condensation degree than ER, which was confirmed by RICO and solid-state 13C nuclear magnetic resonance analysis. The result was explained by ethanolysis simulation of lignite-related model compounds using density functional theory. Thermogravimetric analysis of ZL and ER exhibits their different pyrolytic reactivities. According to analysis with a Curie-point pyrolyzer–gas chromatograph/mass spectrometer, significant differences in the distributions of the volatile species from the pyrolyses of ZL and ER were observed. Guaiacols and carbazoles are the most abundant group components from the pyrolyses of ZL and ER, respectively. ZL pyrolysis released much more alkanes and phenolic compounds than ER pyrolysis. The cleavage of Car–O bonds significantly proceeded during ZL ethanolysis.

Insight into structural feature of the extraction residue from Shenmu coal char powder

Ruthenium ion-catalyzed oxidation of the extraction residue from Shenmu coal char powder (ERSCCP) was conducted. The resulting soluble portions (SPs) were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and direct analysis in real time/time-of-flight mass spectrometer (DART/TOF-MS) to obtain carboxylic acids and to understand the structural feature of ERSCCP. The results show that benzenepolycarboxylic acids with 3–6 carboxy groups are predominant in the SPs, suggesting that ERSCCP is rich in highly condensed aromatic moieties. In addition, small amounts of long-chain alkanoic acids were detected with GC/MS. According to analysis with positive-ion DART/TOF-MS, [M - OCH3]+ and [M+NH4]+are dominant ions generated from polymethylbenzenepolycarboxylates (PMBPCs) in the methyl esterified SPs. A series of dimers and trimers of PMBPCs were also identified with positive-ion DART/TOF-MS.

Quantitative Molecular Characterization of Petroleum Asphaltenes Derived Ruthenium Ion Catalyzed Oxidation Product by ESI FT-ICR MS

Molecular structure of heavy petroleum could be investigated by the composition of its ruthenium ion catalyzed oxidation (RICO) products. However, the interpretation of the results was not comprehensive due to the limited compositional information obtained solely by gas chromatography (GC) analysis. In this study, a semiquantitative method based on electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was established and applied for the molecular characterization of RICO products. Thousands of polar compounds were detected by negative-ion ESI FT-ICR MS in the RICO products of the Canadian oil sands bitumen derived asphaltenes. Besides alkyl carboxylic acids, naphthenic acids with one to five naphtha rings, nitrogen- and sulfur-containing carboxylic acids, and acidic compounds with multioxygen atoms were observed. The upper carbon number limit of alkyl moieties connected to the aromatic cores of the asphaltenes was found up to 60, which is much higher than th...

Characterization of condensed aromatics and heteroatomic species in Yanshan petroleum coke through ruthenium ion-catalyzed oxidation using three mass spectrometers

Ruthenium ion-catalyzed oxidation of Yanshan petroleum coke (YPC) was performed to characterize condensed aromatics and heteroatomic species in YPC.

Investigation on the structural features of Zhundong subbituminous coal through ruthenium ion-catalyzed oxidation

The structural features of Zhundong subbituminous coal were investigated by RICO and subsequent analysis with a gas chromatograph/mass spectrometer and an atmospheric pressure solid-analysis probe/time of flight-mass spectrometer.