Abstract: Lignite is of high carbon content, rich in oxygen and nitrogen, and other heteroatoms, thereby is treated as an important raw material for the preparation of carbon materials. However, the preparation of carbon materials from lignite is faced with many challenges, due to the low soluble organic carbon content and the irregular distribution of heteroatoms. Therefore, it is necessary to achieve the soluble transformation of lignite. In this investigation, ammonia was applied to achieve the solubilization of Zhaotong lignite, and also the regulation of oxygen and nitrogen in soluble portion from lignite under mild conditions. As a result, Zhaotong lignite exhibits efficient thermal dissolution with a soluble portion yield of 76.66%, at the condition of ammonium concentration of 15%, temperature of 160 ℃, and reaction time of 3 h. Based on the characterization and analysis of soluble portion, the macromolecular structure of coal is changed by ammonolysis, mainly displaying the replacement of the hydroxyl group by the amino group or the formation of organic nitrogen groups by the direct reaction between the carboxyl or carbonyl groups with the amino group. By contrast, the occurrence forms of nitrogen in raw coal are mainly quaternary nitrogen and pyrrole nitrogen, while they in soluble matter are mainly amino nitrogen and pyridine nitrogen, indicating that amino or amide groups are formed during the thermal dissolution of lignite.
Abstract: Coal gasification fine slag is one of the by-products from clean and efficient utilization of coal, and its resource utilization is extremely urgent. In this work, a high carbon fraction with a fixed carbon content higher than 60% was obtained by simple sieving of gasification fine slag, from which a porous material was prepared by ultrasonic acid leaching method. The adsorption performance of porous materials, being used as treatment of radioactive iodine in nuclear wastewater, is characterized by iodine adsorption value. The effects of ultrasound time, ultrasound power, acid concentration, and temperature on the iodine adsorption performance and compositional structure of the porous materials were systematically investigated by combining the results of SEM, BET, XRD, and FTIR. The mechanisms of ultrasound-enhanced acid leaching on compositional structure of residual carbon and migration and transformation laws of the ash constituents were explored and summarized. The results show that the porous material prepared under conditions of acid concentration of 4 mol/L, acid immersion temperature of 50 ℃, ultrasonic power of 210 W, and ultrasonic time of 1.5 h has the best iodine adsorption performance of 468.53 mg/g, with a specific surface area of 474.97 m2/g, and possesses a rich pore structure with predominant mesopores. The order of each factor on the iodine adsorption performance is: sonication time > acid concentration > sonication power > acid immersion temperature. The mechanism of ultrasonic enhanced acid leaching is that ultrasonic cavitation and mechanical wave action firstly enhance dissociation of carbon-ash adherent particles, thus making desorption of ash particles blocked in pore channels of the gasification slag to increase its connectivity; secondly, lead to generation of cracks on surface of the carbon and ash particles to enhance accessibility of inorganic components inside the carbon particles; and thirdly, enhance the acid leaching process by increasing mass transfer rate to strengthen leaching effect of inorganic components in the gasification slag.
Abstract: A zirconium oxychloride based ternary deep eutectic solvent (DES) was prepared by simply heating mixture of ethylene glycol, p-toluenesulfonic acid and octahydrate zirconium oxychloride. The successful synthesis of deep eutectic solvents was verified using Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectroscopy (1H NMR). The acidity and viscosity were tested using UV-visible absorption spectroscopy and rotary viscometer, respectively. The extraction-oxidation desulfurization system was composed of hydrogen peroxide as the oxidant, deep eutectic solvent as the extractant and catalyst. The effects of the composition of the deep eutectic solvent, reaction temperature, oxygen sulfur ratio, solvent oil ratio, and different sulfides on the desulfurization rate were investigated. The experimental results showed that the desulfurization rates of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzothiophene (BT) simulated oil were 100%, 92.2%, and 60%, respectively, under the optimal reaction conditions of a molar ratio of 1:10:10 between zirconium oxychloride, ethylene glycol, and p-benzenesulfonic acid components, 50 ℃, a solvent oil ratio of 1∶5, and an oxygen sulfur ratio of 8. After repeated use of the deep eutectic solvent for 5 times, the desulfurization rate could still reach 96.2%. The mechanism of oxidative desulfurization was explored.
Abstract: The Co catalysts exhibit high catalytic activity and low water gas shift activity, as well as excellent chain growth ability and low by-product selectivity for Fischer-Tropsch synthesis. The performance of the Co catalyst is influenced by several factors, including its structural composition and physical and chemical properties. The traditional cobalt Fischer-Tropsch catalyst follows the ASF distribution, resulting in a wide range of hydrocarbon products. This makes it difficult to achieve high selectivity for liquid hydrocarbons. Due to the presence of a large number of acidic sites on the surface of zeolite, it has excellent catalytic performance for hydrocracking. The integration of zeolite molecular sieves with Fischer-Tropsch catalysts to form a multi-component catalyst can significantly improve product selectivity, optimize liquid hydrocarbon yields and bypass conventional wax treatment steps. In this study, the catalysts Co/Al2O3, Co/Zr/Al2O3 and Co/Zr/Al2O3-Pt/ZSM-5 were prepared by ultrasonic dispersion method, and the effects of Zr promoter modification and multicomponent coupling catalyst on the activity and product selectivity of Fischer-Tropsch synthesis were investigated. In Co/Al2O3, Co/Zr/Al2O3 and Co/Zr/Al2O3-Pt/ZSM-5 catalysts, the Co species are uniformly dispersed on the support surface and have similar particle sizes. Pt and Zr were uniformly dispersed in the catalyst, Zr was mainly dispersed on the surface of Al2O3 supports, and Pt was mainly dispersed on the surface of ZSM-5 molecular sieve. The reduction of Co species was promoted by Zr-modified alumina. With the addition of Pt/ZSM-5 catalyst, the adsorbed hydrogen is more easily dissociated and converted into active hydrogen, further promoting the reduction of Co species. The catalytic performance of Fischer-Tropsch synthesis was evaluated. Compared with Co/Al2O3 catalyst, the selectivity of C12+ heavy hydrocarbon products on Co/Zr/Al2O3 catalyst increased from 28.2% to 38.1%, with a corresponding decrease in CH4, C2−C4 and C5−C11 products, indicating that Zr promoter promoted the generation of heavy hydrocarbon products. Coupled with Pt/ZSM-5 catalyst, the Co/Zr/Al2O3-Pt/ZSM-5 catalyst showed low CH4 selectivity (10.0%) and C2−C4 selectivity (15.0%), while the selectivity of C5−C11 liquid hydrocarbon products increased from 32.1% to 45.9%, the selectivity of heavy hydrocarbon products (C12+) decreased from 38.1% to 29.1%. Compared to Co/Zr/Al2O3, the TOF and CTY of Co/Zr/Al2O3-Pt/ZSM-5 catalysts are increased by 212.6% and 62.7%, respectively. The improvement in catalytic activity was mainly due to the addition of Zr promoter and Pt/ZSM-5 catalyst, which promoted the reduction of Co species. Under the synergistic effect of Zr promoter and Pt/ZSM-5 catalyst, Zr promoter promotes the formation of C12+ heavy hydrocarbons, while Pt/ZSM-5 catalyst promotes the hydrocracking of heavy hydrocarbons to C5−C11 liquid hydrocarbons, thereby improving the selectivity of Co/Zr/Al2O3-Pt/ZSM-5 catalyst for C5−C11 liquid hydrocarbons. In this study, a functional catalyst was constructed by coupling Fischer-Tropsch synthesis catalyst and hydrocracking catalyst at nanoscale, which achieved high selectivity of C5−C11 liquid hydrocarbon and low selectivity of CH4 and C2−C4 products, which provided a reference for the design and implementation of catalysts with high selectivity for liquid hydrocarbons.
Abstract: A series of spinel catalysts, including ZnFe2O4, MgFe2O4, CuFe2O4, and MnFe2O4, were prepared and applied to the Fischer-Tropsch synthesis (FTS). Zn, Mg, Cu and Mn easily form spinels with Fe. Among them, Zn and Mg can significantly maintain the spinel structure during the pretreatment and reaction, resulting in a low CO conversion. Cu and Mn are beneficial to the formation of iron carbide during the reaction, resulting in an apparent influence on FTS performance. ZnFe2O4 has little effect on the hydrocarbon distribution and the olefin/paraffin (O/P) ratio of C2−C4. MgFe2O4 exhibits low selectivity for C5+ hydrocarbons, and the selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4 in the product are increased due to the alkaline effect of Mg. Cu can promote the carbonization of the catalyst, so that CuFe2O4 has higher activity. Meanwhile, CuFe2O4 can significantly improve the selectivity of C5+ hydrocarbons. Moreover, Cu can promote the dissociation and activation of H2, which is beneficial to the secondary hydrogenation of olefins, thereby reducing the selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4. Mn promotes carbonization during the reaction, but MnFe2O4 has little effect on the chain growth of hydrocarbon. However, Mn can promote the generation of a certain amount of ε-Fe2C, which may explain the higher selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4 for MnFe2O4. All spinel catalysts exhibit low CO2 selectivity, which meets the current green environmental protection requirements.
Abstract: Phenolic derivatives, crucial components of bio-oil, require thorough understanding of their electrocatalytic hydrogenation (ECH) properties for efficient bio-oil utilization. This study investigated guaiacol, a representative phenolic derivative in bio-oil, focusing on its ECH mechanism, conversion, and product selectivity under varied conditions (temperature: 40−80 °C, perchloric acid concentration: 0.2−1.0 mol/L, current intensity: ((−10)−(−150) mA). Additionally, this study also explored the influence of intermediate products (2-methoxycyclohexanone and cyclohexanone) on both the conversion rate and the selectivity of the products. The experiment had revealed that guaiacol's ECH conversion rate improved with higher temperature and current intensity, whereas an increase in perchloric acid concentration negatively affected the conversion. Significantly, the presence of intermediate products, especially 2-methoxycyclohexanone, markedly enhanced the ECH conversion of guaiacol. Investigating further into the ECH mechanism of other phenolic derivatives, including phenol, pyrocatechol, guaiacol eugenol, and vanillin, as well as their combination, revealed a trend where conversion rates inversely correlated with the complexity of the functional groups on the benzene ring. Specifically, phenol, with its simpler structure, showed the highest conversion rate at 89.34%, in stark contrast to vanillin which, owing to its more complex structure, exhibited the lowest at 46.79%. In our multi-component mixture studies, it was observed that synergistic and competitive interactions significantly alter ECH conversion rates, with some mixtures showing enhanced conversion rate indicative of synergistic effects.
Abstract: The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.
Abstract: Cuprous oxide (Cu2O) is an ideal visible light catalyst owing to its narrow band gap, environmental benignity and abundant storage; however, the fast recombination of photogenerated charge carriers and poor stability of Cu2O has impeded its application in photocatalysis. Herein, we demonstrate that Cu2O@C nanocomposite can spontaneously evolve from a methanol aqueous solution containing cupric ions under the induction of irradiation. Compared with the traditional carbon coating method, the Cu2O@C nanocomposite obtained by the photo-induced in-situ synthesis can reserve superior original characteristics of the semiconductor under mild reaction conditions, promote the charge transfer and enhance the separation efficiency of charge carriers; in addition, the carbon shells can also effectively prevent Cu2O from photo-corrosion. As a result, the Cu2O@C nanocomposite exhibits excellent photocatalytic activity in the hydrogen evolution in comparison with the Cu2O particles; the H2 evolution rate over the Cu2O@C nanocomposite reaches 1.28 mmol/(g·h) under visible light, compared with the value of 0.065 mmol/(g·h) over Cu2O. Moreover, the Cu2O@C nanocomposite displays good cycle stability, viz., without any deactivation in the catalytic activity after five cycles.
Abstract: A series of Co3O4/eggshell catalysts with different Co3O4 contents were prepared by the deposition-precipitation method using discarded eggshells as supports, and tested for the catalytic reaction of N2O decomposition on a fixed-bed continuous flow micro-reactor. The activity test results show that the catalyst exhibits higher activity towards N2O decomposition when the mass fraction of Co3O4 is 20%, with a specific activity of 4.3 times to that of pure Co3O4 (reaction temperature 440 ℃). At the same time, it shows strong resistance to 3% O2, 3.3% H2O and/or 2.0×10−4 NO in feed. Various characterization results indicate that the predominant composition of eggshell is CaCO3, which has a close incorporation with Co3O4. The strong interaction between CaCO3 and Co3O4 contributes to producing more oxygen vacancies and Co3+ in the 20% Co3O4/eggshell catalyst. The redox performance of Co3O4 is improved, and the Co−O bond is effectively weakened. In addition, it helps to increase the strength and amount of basic sites on the catalyst surface, making it easily transfer electrons and promote N2O decomposition.
Abstract: The mechanism of nitrogen oxide (NO) reduction over graphite carbon-supported single-atom iron (Fe) catalyst (Fe/G) was investigated by density functional theory (DFT) and transition state theory (TST). The catalyst deactivation was also analyzed. The results revealed that the NO reduction, based on the Eley-Rideal (E-R) mechanism, underwent four stages including N2O formation and release as well as N2 formation and release. However, the NO reduction only involved two stages according to Langmuir-Hinshelwood (L-H) mechanism: N2 formation and release. Furthermore, for the E-R mechanism, the rate-controlling step was NO reduction, where a NO molecule was adsorbed on an Fe atom with an N, O-down structure with energy barrier of 15.5 kJ/mol, lower than that of other paths. Energy barrier analysis indicated that the energy barrier for the reduction of reactive oxygen species was higher than that for the formation of N2. Reactive oxygen species remaining on the surface of Fe atoms after NO decomposition inhibited the adsorption and reduction of NO, leading to catalyst deactivation due to the absence of active sites. The single-atom Fe species promoted the NO reduction. Kinetic analysis results suggested that, upon increasing the reaction temperature, the NO reduction rate increased more significantly than the reactive oxygen transfer rate.
Abstract: Flame spray pyrolysis (FSP) is a versatile, rapid, and scalable preparation technique for the nanocatalysts. CeO2 and Pt-CeO2 carriers, Pd-Pt-CeO2 catalyst were synthesized by flame spray pyrolysis, and then Pd-Pt bimetallic catalysts were prepared by impregnation method, and as-obtained Pd-Pt catalysts were tested in the methane combustion. The physicochemical properties of the catalysts were characterized by ICP, XRD, TEM, BET, H2-TPR, XPS, and Raman. TEM results showed that Pd and Pt species were highly dispersed in CeO2 carriers in Pd-Pt/CeO2 catalysts. Compared with the Pd-Pt-CeO2(OS-FSP) catalyst prepared by one-step flame spray pyrolysis, the catalytic activity of the Pd-Pt/CeO2(0.25)-WI prepared by co-impregnation was higher, with its t50 reduced by 60 ℃, and no deactivation was seen for 60 h. It is attributed to the fact that the Pd-Pt/CeO2(0.25)-WI catalyst has a higher molar ratio of Pd0/Pd2+ and Ce3+/Ce4+ on the surface of the catalyst and more lattice oxygen, resulting in an excellent performance during the methane combustion.
Abstract: Biomass-based 2,5-bis(hydroxymethyl)furan (BHMF) is one of the important high value-added chemicals, which can be prepared from inexpensive and renewable carbohydrates through the way of catalytic conversion and selective hydrogenation, and as a widely used chemical intermediate and fuel precursor, it has unique advantages in improving the performance of traditional polyesters and synthesizing new biodegradable bio-based polyesters. In recent years, the research on the production of high value-added chemicals such as BHMF from carbohydrate has been attracting much attention from both academia and industry. However, cleanliness, high efficiency, high selectivity and low-cost remain key challenges in this area, especially for practical applications. In the process of BHMF production, the traditional hydrogenation method consumed a large amount of high-grade energy of hydrogen, and an excessive investment in infrastructure would be generated due to the security risks of higher pressure of hydrogen. On account of the advantages of catalytic transfer hydrogenation, the advances in selective hydrogenation to prepare BHMF using formic acid, alcohols and other types of hydrogen donors by the approach of catalytic transfer hydrogenation is systematically discussed in this review. In view of the features and problems of different types of hydrogen donors, catalysts and reaction processes during the catalytic transfer hydrogenation process, the effects of reaction conditions and process intensifications on the selectivity and yield of BHMF, and the merits and demerits of the reaction system were all investigated. On this basis, the future directions of new catalytic systems for preparation of BHMF by transfer hydrogenation is proposed, and the cleaner, more efficient and essential safety technologies for the production of BHMF is predicted, which will provide some scientific reference for the research and development of related catalytic systems in biomass conversion.
Abstract: Selective catalytic reduction (SCR) technology has been widely used in the denitrification of cement industry, in which a relatively mature system has been formed in the high temperature (280–350 ℃) section, but there is still a breakthrough in the middle temperature zone. Focusing on medium temperature catalysts, this paper reviewed the progress of Mn, Ce and V catalysts, and analyzed the doping of Sm, Nb, Ho, Sb, La, Mo and Pr to improve the performance of catalysts. Combined with the characteristics of the high content of SO2, H2O and alkali metal in cement kiln smoke, the causes of catalyst poisoning were analyzed, and the way to resist sulfur poisoning, water poisoning, and alkali metal poisoning was summarized. The research prospect of SCR medium temperature denitration catalyst in cement industry is prospected.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
