Analysis of soluble components in coals and interpretations for the complex mass spectra.

RATIONALE: The deduction of useful information from the mass spectra of a complex mixture like coals remains difficult, which limits the clean and efficient utilization of coals. It is necessary to explore the data interpretation methods for mass spectra and visualize the analytical data of coals for industrial utilization such as feedstock selection. METHODS: Coal sample and methanol were mixed and heated to 310 °C and kept at that temperature for 2 h. The solvent was under supercritical state at 310 °C and the solubility for the solid mixture increased. Soluble products from thermal dissolution of two Chinese coals were analyzed by high-performance liquid chromatography/atmospheric pressure chemical ionization orbitrap mass spectrometry. RESULTS: The iso-abundance plot for molecules in coals was upgraded to display the distributions of isomers which are indicated as concentric circles or triangles with the same carbon number and value of double-bond equivalent. The concentration ratio was introduced from economics to describe the content inequality of organic species within the same class of coal molecules. CONCLUSIONS: Interpretation methods for mass spectra visualize and simplify the understanding of complex components in coals for industrial utilization. Coals with a high concentration ratio for a specific class should take priority as a feedstock for chemicals and receive more attention. Copyright © 2016 John Wiley & Sons, Ltd.

Sequential ultrasonic extraction of a Chinese coal and characterization of nitrogen-containing compounds in the extracts using high-performance liquid chromatography with mass spectrometry.

Dongming lignite was sequentially extracted with petroleum ether, carbon disulfide, methanol, acetone, and isometric carbon disulfide/acetone mixed solvent at room temperature to afford extracts 1-5, respectively. High-performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry was used to separate and characterize heteroatomic species in the extracts at molecular level. Molecular mass of compounds in the extracts is mainly distributed from 300 to 800 u, and the relative abundance of compounds with molecular mass over 800 u in the carbon disulfide extract is 135 times of that in the petroleum ether extract. The acetone extract has the highest relative abundance for organonitrogen compounds. Double bond equivalence numbers of detected species indicate that most of the organonitrogen compounds contain N-heterocyclic aromatic rings, including pyridine, quinoline and pyrrole. Some organonitrogen isomers in Dongming lignite were separated and identified by high-performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry, and the corresponding structural information was proposed.

Pd-Based Nano-Catalysts Promote Biomass Lignin Conversion into Value-Added Chemicals.

Lignin, as a structurally complex biomaterial, offers a valuable resource for the production of aromatic chemicals; however, its selective conversion into desired products remains a challenging task. In this study, we prepared three types of Pd-based nano-catalysts and explored their application in the depolymerization of alkali lignin, under both H2-free (hydrogen transfer) conditions and H2 atmosphere conditions. The materials were well characterized with TEM, XRD, and XPS and others, and the electronic interactions among Pd, Ni, and P were analyzed. The results of lignin depolymerization experiments revealed that the ternary Pd-Ni-P catalyst exhibited remarkable performance and guaiacols could be produced under H2 atmosphere conditions in 14.2 wt.% yield with a selectivity of 89%. In contrast, Pd-Ni and Pd-P catalysts resulted in a dispersed product distribution. Considering the incorporation of P and the Pd-Ni synergistic effect in the Pd-Ni-P catalyst, a possible water-involved transformation route of lignin depolymerization was proposed. This work indicates that metal phosphides could be promising catalysts for the conversion of lignin and lignin-derived feedstocks into value-added chemicals.

In situ one-pot synthesis of Sn/lignite-based porous carbon composite for enhanced lithium storage.

To expand the variety of Sn/C composites, lignite-based porous carbon was initially prepared with Baoqing lignite as the raw material and K2CO3 as the extractant and activator. A novel Sn/lignite-based porous carbon composite was subsequently fabricated via an in situ one-pot synthesis method. In the nanocomposite, Sn nanoparticles are uniformly distributed on lignite-based porous carbon, improving the lithium-ion storage performance of the as-prepared material. Compared with pure Sn and bare lignite-based porous carbon, Sn/lignite-based porous carbon displayed a superior electrochemical performance. The composite material exhibits a high reversible capacity of 941 mAh g-1 after 200 cycles at 100 mA g-1. Even after 800 charge/discharge cycles at a high current density of 1000 mA g-1, the nanocomposite retains a reversible capacity of 573 mAh g-1. The enhanced lithium-ion storage performance can be attributed to the combined effect of Sn and lignite-based porous carbon.

Amorphous/low-crystalline core/shell-type nanoparticles as highly efficient and self-stabilizing catalysts for alkaline hydrogen evolution.

Amorphous/low-crystalline core/shell-type nanoparticles (Pd-P/Pt-Ni NPs) were prepared via a facile seed-mediated method. After acid treatment, the NPs exhibited self-improved catalysis for hydrogen evolution during electrolysis in an alkaline medium.

Preparation of layered-porous carbon from coal tar pitch narrow fractions by single-solvent extraction for superior cycling stability electric double layer capacitor application.

Coal tar pitch (CTP) with high carbon content and wide source of raw materials was an excellent precursor for the preparation of porous carbons (PCs). CTP was composed of polycyclic aromatic hydrocarbons (PAHs) with complex molecular size and chemical structure, the separation of CTP into several fractions with relatively narrow molecular weight by solvent extraction was of significance for CTP utilization. In this paper, CTP was treated by single-solvent extraction (carbon disulfide, acetone and ethyl acetate), and the six fractions were used as raw materials to prepare PCs as electrode material for electric double layer capacitor. The fractions were well characterized and the effect of mass distribution of different narrow fractions on structure property and electrochemical performance of the PCs was studied. The PCs prepared by carbon disulfide extract, acetone raffinate and ethyl acetate extract, containing more PAHs, exhibited the excellent specific capacitance performance in comparison with its residual components. The remarkable performance might contribute in the enhanced transport of electrolyte ions via the molecular graphene structure of PAHs. Additionally, the PC prepared by carbon disulfide raffinate showed outstanding cycling performance (99.7% at 2 A g-1 after 15,000 cycles) which was related to its unique layered porous structure.

N/O co-doped porous interconnected carbon nanosheets from the co-hydrothermal treatment of soybean stalk and nickel nitrate for high-performance supercapacitors.

Porous interconnected carbon nanosheets (PICNs) with high electrochemical performance were prepared by doping urea and a co-hydrothermal precursor derived from soybean stalk (SS) and nickel nitrate. The specific surface area and average pore diameter of the as-synthesized PICNs are 2226.29 m2 g-1 and 1.89 nm, and their N and O contents are 5.08% and 9.4%, respectively, which is beneficial for increasing pseudocapacitance. Furthermore, the doping of the metal Ni increases the graphitization degree of the PICNs and promotes the conversion of pyridine-N to graphitized-N. Therefore, the PICNs possess a high specific capacitance of 407 F g-1 at a current density of 0.5 A g-1, a high capacitance retention of 78.62% even at 20 A g-1, and an outstanding cycling stability (over 93% retention rate after 10,000 charge/discharge cycles). Moreover, an energy density of 36.11 W h kg-1 is achieved at a power density of 517.8 W kg-1 during a two-electrode system test, and a retention rate of 87.5% is obtained after 10,000 cycles. This co-hydrothermal treatment as well as nitrogen-doping approach for preparing porous interconnected carbon from SS not only represents an alternative strategy for carbon-based supercapacitor materials but also provides a new option for the utilization of waste SS.

Enhancement of light aromatics from catalytic fast pyrolysis of cellulose over bifunctional hierarchical HZSM-5 modified by hydrogen fluoride and nickel/hydrogen fluoride.

Pore structure and accessible active sites of HZSM-5 (Z5) are the key factors for its catalysis. The bifunctional hierarchical Z5 were prepared with leaching agent HF and loading Ni, and their performance for catalytic fast pyrolysis (CFP) of cellulose was investigated in a drop tube quartz reactor. Z5 modified with 0.5 mol/L HF (0.5F-Z5) showed excellent light aromatics (LAs) yield, which can be attributed to the enhancement in the small mesopores (2-10 nm) and the decrease of Brønsted acid sites during dealumination. Simultaneously, the loading of a 1 wt% Ni produced more LAs than 0.5F-Z5, due to the improvement in deoxidation/hydrogenation reactions. The highest LAs yield (31.3%) was obtained over 1%Ni-0.5 mol/LHF-Z5, which increased by 44.9% compared to the parent Z5. In addition, the reaction routes over different active centers and acid-catalyzed reactions were analyzed, based upon the composition of bio-oils and catalyst characterization.

Preparation of porous carbon spheres from 2-keto-l-gulonic acid mother liquor by oxidation and activation for electric double-layer capacitor application.

A novel strategy is proposed for the increase of specific surface area (SSA) of porous carbon sphere (PCS) by oxidation and activation. 2-keto-l-gulonic acid mother liquor (GAML) as a high-pollution waste has a relatively high value of reutilization. For its high value-added utilization, GAML is used as the precursor for preparation of PCS as carbon-based electrode materials for electric double-layer capacitor. PCS is prepared by hydrothermal carbonization, carbonization and KOH activation, and Fe(NO3)3 9H2O is used as an oxidizing agent during carbonization. The as-prepared PCS has excellent porosity and high SSA of 2478 m2 g-1. Meanwhile, the pore structure of PCS can be controlled by the adjustment of carbonization parameters (carbonization temperature and the loading of Fe(NO3)3 9H2O). Besides, the SSA and specific capacitance of PCS can be increased remarkably when Fe(NO3)3 9H2O is added in carbonization. The specific capacitance of PCS can reach 303.7 F g-1 at 40 mA g-1. PCSs as electrode material have superior electrochemical stability. After 8000 cycles, the capacitance retention is 98.3% at 2 A g-1. The electric double-layer capacitance of PCS is improved when CS is carbonized with Fe(NO3)3 9H2O, and the economic and environmental benefits are achieved by the effective recycle of GAML.

Catalytic reforming of nitrogen-containing volatiles evolved through pyrolysis of composted pig manure.

The pyrolysis of pig compost was performed in a two-stage fixed-bed reactor to determine the effects of decomposition temperatures and catalysts (i.e., transition-metal and non-transition-metal catalysts) on carbon and nitrogen conversions. The secondary decomposition was investigated at different temperatures from room temperature up to 750°C. Then the effects of various catalysts were investigated at 650°C. Approximately 60% of the carbon and 80% of the nitrogen in the pig compost were converted into volatiles during pyrolysis. Conversion of carbon and nitrogen species in tar into gas, and the evolution undesirable NH3 and HCN without catalyst increased with increasing decomposition temperature. Transition-metal catalysts showed excellent activity for conversion of condensable volatiles into gas and NH3 and HCN into N2. Although non-transition-metal catalysts had moderate activity for the conversion of volatiles into gas and negligible activity for the conversion of NH3 into N2, dolomite can provide liquid fuel with negligible amount of nitrogen species.

Synergic effect of methanol and water on pine liquefaction.

Pine liquefaction (PL) and re-liquefaction of its liquefaction residues in sub- and supercritical methanol, water or methanol/water mixed solvents (MWMSs) was investigated. The results show that isometric MWMS has the highest synergic effect on PL. Moreover, the total yield of bio-oil (BO) and conversion from pine and its residue both liquefied in the MWMS were obvious higher than those from PL in methanol (water) and re-liquefaction of its residue in water (methanol), suggesting that the interaction between the two solvents is responsible for synergic effect. This approach facilitates understanding the mechanism for biomass liquefaction in mixed solvents and developing efficient utilization process of biomass.

Characterization of a bio-oil from pyrolysis of rice husk by detailed compositional analysis and structural investigation of lignin.

Detailed compositional analysis of a bio-oil (BO) from pyrolysis of rice husk was carried out. The BO was extracted sequentially with n-hexane, CCl(4), CS(2), benzene and CH(2)Cl(2). In total, 167 organic species were identified with GC/MS in the extracts and classified into alkanes, alcohols, hydroxybenzenes, alkoxybenzenes, dioxolanes, aldehydes, ketones, carboxylic acids, esters, nitrogen-containing organic compounds and other species. The benzene ring-containing species (BRCCs) were attributed to the degradation of lignin while most of the rests were derived from the degradation of cellulose and hemicellulose. Along with guaiacyl and p-hydroxyphenyl units as the main components, a new type of linkage was suggested, i.e., C(ar)-CH(2)-C(ar) in 4,4'-methylenebis(2,6-dimethoxyphenol). Based on the species identified, a possible macromolecular structure of the lignin and the mechanism for its pyrolysis are proposed. The BO was also extracted with petroleum ether in ca. 17.8% of the extract yield and about 82.1% of the extracted components are BRCCs.

Low temperature catalytic gasification of pig compost to produce H2 rich gas.

The low temperature catalytic gasification of pig compost before and after acid washing was carried out to produce H2 rich gas using a two-stage fixed-bed reactor. Little effect of the minerals on the manure pyrolysis is determined. Under the presence of Ni/Al2O3 catalyst nearly all the tarry matters were cracked into H2, CO, CO2 and residual carbon. High H2 and CO yields were obtained by low temperature catalytic steam gasification. Acid washing results in the decrease in the content of the ease-hydrolyzed organic components, which volatilize at low temperature. The change in the gas yields from the manure during catalytic decomposition is in accordance with its pyrolysis behavior.

H2 production from fowl manure by low temperature catalytic gasification.

In the paper, H(2) rich gas produced from fowl manure (hen compost-HC) by low temperature catalytic gasification (LTCG) technology is addressed. The pyrolysis behaviors of the samples before and after weak acid pretreatment were investigated using thermal gravimetric analysis. Furthermore, the catalytic influence of HC char and HC ash on the decomposition of the nascent volatiles was determined. A catalytic role of the minerals contained in HC on its pyrolysis behavior was confirmed due to the high content of Ca. LTCG process promotes the complete decomposition of the manure volatiles and significantly increases H(2) yield and the total gas yield. An obvious catalytic effect of HC char and HC ash on the decomposition of the nascent volatiles is attributed to CaO contained in them.

Preparation and characterization of bio-oils from internally circulating fluidized-bed pyrolyses of municipal, livestock, and wood waste.

Fast pyrolyses of sewage sludge (SS), pig compost (PC), and wood chip (WC) were investigated in an internally circulating fluidized-bed to evaluate bio-oil production. The pyrolyses were performed at 500 °C and the bio-oil yields from SS, PC, and WC were 45.2%, 44.4%, and 39.7% (dried and ash-free basis), respectively. The bio-oils were analyzed with an elemental analyzer, Karl-Fischer moisture titrator, bomb calorimeter, Fourier transformation infrared spectrometer, gel permeation chromatograph, and gas chromatography/mass spectrometry. The results show that the bio-oil from SS is rich in aliphatic and organonitrogen species, while the bio-oil from PC exhibits higher caloric value due to its higher carbon content and lower oxygen content in comparison with that from SS. The bio-oils from SS and PC have similar chemical composition of organonitrogen species. Most of the compounds detected in the bio-oil from WC are organooxygen species. Because of its high oxygen content, low H/C ratio, and caloric value, the bio-oil from WC is unfeasible for use as fuel feedstock, but possible for use as chemical feedstock.

Effect of pretreatment with different washing methods on the reactivity of manure char.

During low temperature gasification process of livestock manure, combustion of manure char feedbacks energy for the gasification reactions. The purpose of the present study is to determine the effect of mineral matters on the reactivity of manure char. The chars were prepared from pig and hen composts pretreated by different washing methods. The results show that the oxidation behavior of the manure char is affected greatly by the pretreatment process employed. Oxidation reactivity of the char from raw manure is much higher than that from de-mineralized manure sample. A good correlation between char reactivity and ash content was obtained. The difference in the char reactivities should be attributed to the presence of catalytically active inorganic constituents, especially Ca species.

Fractionation and identification of organic nitrogen species from bio-oil produced by fast pyrolysis of sewage sludge.

Pyrolysis of sewage sludge was performed at 500 degrees C and a sweeping gas flow rate of 300 cm(3)/min in a drop tube furnace. Liquid fraction (i.e., bio-oil) from the sewage sludge pyrolysis was separated by silica-gel column chromatography (SGCC) with different solvents, including mixed solvents, as eluants. A series of alkanenitriles (C(13)-C(18)), oleamide, alkenenitrile, fatty acid amides and aromatic nitrogen species were fractionated from the bio-oil by SGCC and analyzed with a gas chromatography/mass spectrometry (GC/MS). Most of the GC/MS-detectable organic nitrogen species (ONSs) are lactams, amides and N-heterocyclic compounds, among which acetamide is the most abundant. N-heterocyclics with 1-3 rings, including pyrrole, pyridine, indole, benzoimidazole, carbazole, norharman and harman, were observed. The lactams detected include pyrrolidin-2-one, succinimide, phathalimide, glutarimide, piperidin-2-one and 3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione, all of which should be formed via decarboxylation and cyclization of gamma- and delta-amino acids. Such a procedure provides an effective approach to fractionation and identification of ONSs from bio-oil produced by fast pyrolysis of sewage sludge.

Triacetonamine formation in a bio-oil from fast pyrolysis of sewage sludge using acetone as the absorption solvent.

A sewage sludge sample was pyrolyzed in a drop tube furnace at 500 degrees C and sweeping gas flow rate of 300cm(3)/min. Triacetonamine (TAA) was detected with GC/MS as major component in the resulting bio-oil using acetone as the absorption solvent and proven to be a product from the reaction of NH(3) in the bio-oil with the absorption solvent acetone. TAA yield increased with storage time and reached a level about 28.4% (% sludge fed, daf) after 175h. Since the reaction of pure NH(3) with acetone does not proceed, some species in the bio-oil must catalyze the reaction of NH(3) with acetone. TAA was isolated in a high yield (27.9%, daf) and high purity (80.4%) by column chromatography with different solvents, including mixed solvents, as eluants. The study revealed the possibility of sewage sludge as potential resource of TAA.

Influence of manure types and pyrolysis conditions on the oxidation behavior of manure char.

Livestock manure can be quickly converted into valuable products (H(2), syn-gas and char) by low temperature gasification. Manure char combustion offers energy for the gasification reactions. In the paper, the influence of manure type and pyrolysis conditions on manure char reactivity is addressed. The results show that the oxidation behaviors of manure char are dependent strongly on manure type and pyrolysis conditions employed. The large difference between the oxidation behaviors of pig and hen manure chars can be attributed to the difference in the organic materials and minerals of the samples. High final temperature, flash pyrolysis and water steam atmosphere used for char preparation promote the resultant char reactivity.