Abstract: When a granular bed filter is used for the dust removal of hot gas containing tar from low-rank coal pyrolysis, the filter media will affect the reaction behavior of gaseous tar to a certain extent. Four granular bed filter media including ceramic ball (CB), expanded perlite (EP), activated carbon (AC) and γ-Al2O3, were selected to investigate their influence on the gaseous tar reaction during Naomaohu long-flame coal pyrolysis in a downer-bed pyrolysis reactor. The results indicate that the distribution and compositions of pyrolysis products and the coke deposition behavior are significantly affected by the filter media. The inert CB and EP increase the residence time of gaseous tar, which intensifies the cracking and polycondensation reactions of gaseous tar, resulting in a reduction in the tar yield and an increase in the gas, water and coke yield. In the meantime, the pitch content in tar is increased due to the polycondensation reactions of gaseous tar, while the chemical composition of tar and the amount of coke in tar have less change. The AC and γ-Al2O3, which have a strong catalytic cracking action, reduce the pitch content and the amount of coke in tar. Also, partial gaseous tar is transformed into gas, water and coke, resulting in an obvious reduction in the tar yield. Also, AC and γ-Al2O3 can crack some oxygen-containing compounds and nitrogen-containing or sulfur-containing heterocycles in the gaseous tar into aromatics.
Abstract: Coal-derived needle coke was prepared using refined coal tar pitch as feedstock. Its polarized light microstructure was quantitatively analyzed by bricc-m coal macerals automatic testing system with RICC-Imager analysis software and the dot counting method. Microstructure of needle coke was characterized using scanning electron microscope. The results indicate that the large domain streamline structure content of the prepared green coke is 87.8% under carbonization conditions of 490 ℃, 0.2 MPa and 6 h, which shows good optical microstructure. Compared with the traditional quantitative analysis method, the quantitative analysis using dot counting method is more accurate and efficient. It can be used as an effective means for quantitative analysis of needle coke microstructure.
Abstract: Based on the mercury (Hg) mass balance, a sequential-chemical-extraction method and the thermal analysis technique were used to investigate the occurrence forms of mercury in coal and the effect of washing process on the Hg migration and emission characteristics using Ningwu coal and its washery products. The experimental results show that the ash content and sulfur content reduce in the cleaned coal and Hg is enriched in the gangue, causing an Hg redistribution in the washery products. The linear correlation coefficients of Hg content with ash and sulfur are 0.89 and 0.99, respectively. Hg mainly exists as an inorganic bound state in the raw coal, so its migration behavior is determined by the transfer of inorganic minerals during the washing process. Gangue shows the highest mass increase in the Hg content by 322.8% compared to the raw coal, while the content of Hg in cleaned coal decreases to 40% of that in raw coal with the removal efficiency of 56.4%. The difference of mercury enrichment degree in coal washery products is closely related to its occurrence form in raw coal, in which the proportion of sulfide-bound mercury in gangue is as high as 56.6%, while the organic bound mercury in cleaned coal and slime is higher than that in raw coal. Furthermore, Hg in all samples has been completely released at 650 ℃ during pyrolysis process. Hg has the highest release ratio in slime and the lowest one in gangue at the same pyrolysis temperature. The release characteristics of mercury in coal is also closely related to its occurrence forms, which determines the Hg release behavior at different temperatures. The organic bound mercury escapes in large quantities at 300 ℃ with the decomposition of organic matter, while the decomposition temperature of sulfide bound mercury mainly concentrates at 400−600 ℃.
Abstract: Moisture is one of the important factors affecting coal spontaneous combustion. Coal with different moisture contents was prepared to obtain oxidized coal samples at different temperatures through temperature programming. In situ Fourier Transform Spectrometer was used to determine content of active functional groups in different oxidized coal samples, and to study influence of moisture form on formation and transformation of microscopic functional groups during coal spontaneous combustion. Nitrogen adsorber was used to study specific surface area of different oxidized coal samples and influence of form moisture on changes of micro-pore structure during coal spontaneous combustion. Combined with the change law of functional groups and specific surface area, microscopic action of different form moisture on coal spontaneous combustion process was discussed. The action regime of outside moisture varies with the development of coal spontaneous combustion. Different forms of moisture can promote formation of phenols, alcohols, hydroxyl groups, and carbonyl-containing compounds. Effects of moisture form and its content on change of micro-specific surface area, and on evolution of aliphatic C−H components, hydroxyl-containing compounds and carbonyl-containing compounds during spontaneous combustion of coal are different. While effect of moisture form and its content on formation and transformation of hydroxyl-containing compounds and carboxylic acid compounds are similar.
Abstract: A series of metal (Zn, Ga and Mg) modified H-ZSM-5 bifunctional catalysts were prepared by impregnation method. Three types of milled wood lignin (MWL), isolated from softwood (Chinese Fir, CF), hardwood (Poplar, P) and herbaceous plant (Corn Straw, CS), were served as starting material to produce light aromatics via the catalytic fast pyrolysis (CFP). The effect of metal modifying and lignin source on the component of bio-oil derived from the lignin CFP was investigated. The results indicate that: Among three types of MWL, CF-MWL has the highest carbon content (59.90%) and calorific value (23.05 MJ/kg), whereas CS-MWL has the highest hydrogen content (6.51%) and effective hydrocarbon ratio (0.43); Compared to H-ZSM-5, Ga/H-ZSM-5 and Zn/H-ZSM-5 can promote the production of light aromatics, whereas Mg/H-ZSM-5 inhibits the formation of light aromatics. Zn/H-ZSM-5 as a catalyst in the lignin CFP displays the highest yield of light aromatics, with 3.122 × 109 a.u./mg for CF-MWL, 2.916 × 109 a.u./mg for P-MWL, and 2.865 × 109 a.u./mg for CS-MWL. Among three types of MWLs, the CFP of CF-MWL gives highest selectivity of 65.02% to BTX. The coke is mainly deposited on the outside surface of zeolite catalyst during the pyrolysis, leading to a great decrease in the number of strong acid sites.
Abstract: In order to improve yield of aromatics from catalytic pyrolysis of lignin, alkali lignin was used for rapid pyrolysis experiments under a binary catalysis system of alkali lignin char and ZSM-5. Influence of catalyst ratio and pyrolysis temperature as well as pyrolysis time on aromatics quantity and mechanism of synergistic catalysis of alkali lignin char and ZSM-5 were investigated. The results show that quantity of aromatics has increased from 17 mg/g (without char) to 33 mg/g (with char addition of 1 g), which is about doubled. The optimal conditions for preparation of aromatics are under alkali lignin∶alkali lignin char∶ZSM-5=1∶1∶1 at 500℃ for 10 min. Meanwhile, the mechanism analysis shows that alkali lignin char mainly plays a role in bond breaking during pyrolysis, while ZSM-5 can act as selective aromatization to obtain higher aromatics yield, whose synergistic effects result in higher aromatic yield.
Abstract: MnO2 with different crystal structures was used to catalyze the oxidation reaction of 5-hydroxylmethylfurfural (HMF), and α-MnO2 exhibited the highest catalytic activity. Magnetic MnO2-Fe3O4 oxides were prepared by α-MnO2 and Fe3O4 and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of NH3/CO2 (NH3/CO2-TPD) and Fourier transform infrared reflection spectra of pyridine adsorption (Py-FTIR). The results showed that the composite catalyst still maintained the basic structure of α-MnO2 and Fe3O4, whereas the number of active center Mn4+·O2− ion pair increased compared with α-MnO2 and Fe3O4, which significantly improved the catalytic activity on HMF oxidation reaction. The reaction conditions of HMF oxidation to 2,5-furandicarboxylic acid (FDCA) were optimized. The composite oxide Mn8Fe3Ox showed the best catalytic performance for HMF oxidation. HMF could be completely converted, with 76.9% of FDCA yield under the optimal conditions.
Abstract: CaO/KIT-6 was successfully prepared by loading activated calcium oxide particles on the surface of mesoporous silica (KIT-6) by post-synthesis method and tested for the transesterification of soybean oil with methanol. The catalyst was characterized by XRD, XPS, CO2-TPD, N2 adsorption-desorption and TEM. It is found that when the molar ratio of methanol to oil is 12, the reaction temperature is 65 °C, the addition of catalyst is 8% and the Ca/Si atomic ratio is 0.4, the conversion of soybean oil exceeds 99.9% at 2 h. After 5 cycles, the catalytic activity decreases slightly and the conversion is still up to 90%. Compared with CaO and other supported catalysts, CaO/KIT-6 catalyst exhibits higher catalytic performance and good reusability at lower methanol-to-oil molar ratio.
Abstract: A series of carboxylic acid-functionalized deep eutectic solvents (DES) were constructed by a natural organic dicarboxylic acid, oxalic acid (OA), as the hydrogen bond donor and the polyethylene glycol (PEG) with different polymerization degrees as the hydrogen bond acceptors, which are used in the hydration of α-pinene to produce α-terpineol. Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), and thermogravimetric analysis (TGA) were used to prove the hydrogen bonding between OA and PEG. It is found that the presence of PEG has a less impact on the acid strength of DES. However, an increase in both molecular weight and dosage of PEG results in a decrease in total acidity and catalytic activity. Among them, OA/0.6PEG200, a DES catalyst prepared by PEG with the smallest molecular weight, exhibits a favorable catalytic performance. Under an optimal reaction condition with 0.03 mol of DES (based on OA), 0.06 mol of α-pinene, 0.3 mol of water, at 75 °C for 8 h, an α-pinene conversion of 81.5% and an α-terpineol selectivity of 51.2% are obtained. The catalyst phase can be separated by refrigerating overnight after reaction and reused directly with relatively stable catalytic performance. Thus, OA/0.6PEG200, as a DES catalyst prepared by a simple and highly atom economical process, will offer a clean catalytic route for the one-step production of α-terpineol.
Abstract: ZSM-5 zeolites were modified by desilication with sodium acetate and sodium citrate. The physicochemical properties of ZSM-5 zeolites, such as crystal structure, acid content, surface area and pore volume, were characterized by XRD, SEM, NH3-TPD, 27Al MAS NMR, pyridine adsorption infrared spectroscopy and N2 adsorption-desorption isotherms. The results indicate that pore size of the zeolite increases and mesoporous structures are formed by alkali modification, and the amount of Lewis and Brönsted acid contents decreases obviously. When the concentration of sodium acetate solution is 0.5 mol/L, the modified zeolite has a suitable B/L value for the aromatization of methanol while forming a large number of mesoporous structures. Compared with microporous ZSM-5, the catalyst life is increased from 20 h to 74 h, and the highest yield of aromatics is increased from 20.97% to 40.05%.
Abstract: An investigation of hydrotalcite-derived ternary Mg-Al-Ce oxides as catalysts for vapour phase condensation of ethanol to 1-butanol in a flow reactor under atmospheric pressure was carried out. The Mg-Al-Ce oxide systems with Mg/(Al + Ce) ratio from 1 to 4 were synthesized and characterized by XRD, SEM, NMR, and XPS. The study of acid-base characteristics of the systems with different Mg/(Al+Ce) ratio by NH3/CO2 quasi-equilibrium thermal desorption techniques shows that the ratio of the catalyst oxide components (Mg, Al, Ce) can provide acid/base capacity ratio close to 3 for the effectivity of the target process. The highest selectivity 68% is reached over Mg-Al-Ce oxide catalyst with the ratio of Mg/(Al+Ce) = 2.
Abstract: Developing efficient and stable bimetallic catalysts has been a highly promising challenge for the direct synthesis of ethanol from syngas in recent years. In this study, a series of RhCu/P25 bimetallic catalysts with different Rh contents were prepared by combining the urea-assisted gel method and the impregnation method, and their performance in ethanol synthesis from syngas was studied. The results show that Rh-modified Cu-based catalyst can effectively promote the ethanol production. However, when the active sites of Rh and Cu are in close contact, the reaction products are mainly methane and methanol, and ethanol content is very low. This should be attributed to the inhibition of the adsorption of CO molecules on the Rh and Cu active sites. When the spatial distance between the Rh and Cu active sites is increased by physical mixing, the adsorption of CO molecules is significantly enhanced, and the catalytic activity and ethanol selectivity are improved.
Abstract: The steam reforming and partial oxidation of methane to produce hydrogen under dielectric barrier discharge were conducted in the CH4-O2-N2-H2O reaction system; the effects of H2O/CH4 molar ratio, O2/N2 molar ratio, total gas flow, discharge voltage and discharge frequency on the hydrogen production were investigated and the reaction mechanism was analyzed on the basis of the in-situ diagnostic emission spectroscopy. The results indicate that the conversion of methane and the yield of hydrogen increase with the increase of H2O/CH4 molar ratio, O2/N2 molar ratio, and discharge voltage, but decrease with the increase of the total gas flow rate and show an volcano-shape trend with the increase of discharge frequency (peaked at 9.8 kHz). Under the conditions with an H2O/CH4 molar ratio of 1.82, O2/N2 molar ratio of 2.1, total flow rate of 136 mL/min, discharge voltage of 18.6 kV and discharge frequency of 9.8 kHz, in particular, the conversion of methane and the yield of hydrogen reach 47.45% and 21.33%, respectively. During the reaction, methane and water vapor may dissociate by the action of high energy electrons to generate CHx ·, H·, OH·, O· and other free radicals and hydrogen is then produced through the collision between the free radicals. H· may come from the electronic dissociation of CH4 as well as the dissociation of OH· formed primarily from the water vapor dissociation. The partial oxidation of methane is mainly manifested by the oxidation of CH2· with O·, where O· is produced by the electronic dissociation of O2 as well as the further dissociation of OH·.
Abstract: Expanded graphite (EG) was prepared by intercalation oxidation of natural flake graphite with perchloric acid and Pt nanoparticles were then loaded on the surface of EG by means of liquid phase reduction method with ethylene glycol. The electrocatalytic performance of EG-supported Pt nanoparticle (Pt/EG) catalyst in the direct methanol fuel cell was investigated with the help of XRD, TEM, SEM and cyclic voltammetry (CV) characterizations. The results show that the Pt nanoparticles with average diameter of 2.56 nm are well dispersed on the surface of EG. The structure of expanded graphite sheets can obviously improve the electrocatalystic activity and tolerance to CO poisoning ability during methanol oxidation. Under the same conditions, the mass specific activity and the current density of current Pt/EG catalyst are 1.24 times and 1.5 times that of the commercial JM Pt/C, respectively.
Abstract: In this paper, a series of mesoporous melem materials were prepared from melamine by solid-phase reaction using nano-silica (SiO2) as the template. The mesoporous melem materials with high specific surface area (40−92 m2/g) and pore volume (0.179−0.407 cm3/g) were obtained by adjusting the ratio of SiO2 template and melamine. The obtained melem was used as catalyst for the cycloaddition reaction between BDODGE and CO2. The results showed that the catalytic activity was greatly improved with the increase of specific surface area of the catalysts. The catalyst mp-CN-450-2 showed the best performance. After 20 h reaction at 130 ºC, 2.0 MPa, 99.3% of BDODGE conversion and 99.5% of cyclic carbonate selectivity were acquired, respectively.
Abstract: To study the effects of HNO3 modification on NO reduction over activated carbon (AC) at low temperatures, the AC was modified using HNO3 at different temperatures. The activity of the resulted activated carbons towards NO reduction with NH3 was investigated in a temperature range of 30−250 ℃. The temperature programmed desorption (TPD) and transient response experiments were used to study the mechanism of NO reduction. The results reveal that the NO conversion decreased with temperature at the initial stage and then kept stable. The adsorption of reactants was the rate-determining step. The increase of oxygen groups on the catalyst surface enhanced NH3 adsorption. The adsorbed NH3 hardly reacted with NO at 30 ℃. With increasing temperature, the adsorbed NH3 was gradually activated. In the temperature range of 30−90 ℃, the adsorption of reactants was rate-determining step of NO reduction. When the temperature was higher than 90 ℃, the reaction was dominated by the activation of adsorbed NH3.
Abstract: With the increasing waste disposal problems, high-value utilization technology using less energy is important to incentivize better recycling of plastic waste. Polyethylene high-pressure thermal cracking and catalytic pyrolysis experiments were conducted at a set temperature of 380 ℃ and low initial pressures (1−5) × 105 Pa. The process temperature curves were recorded and the hydrocarbon distribution of products was analyzed. The results suggest that the phase state in the pyrolysis system is a critical issue for reaction pathways. Thus, the pressure changes have different effects on the thermal cracking and catalytic pyrolysis of polyethylene. There is a phenomenon of thermal runaway during the polyethylene high-pressure pyrolysis process. The peak temperature represents a monotonous increase with the increasing initial pressure; the higher peak temperature leads to deeper cracking of polyethylene, giving more low-molecular-weight products. In the high-pressure catalytic pyrolysis experiments under the same other conditions, no thermal runaway is observed. The Zn-supported ZSM-5 catalyst converts polyethylene into aromatics, and the selectivity for monocyclic aromatics in the liquid phase is up to 82.53%. Moreover, the coke yield is less than 1.5%.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
