Haokan Chen

Northeast Institute of Geography and Agroecology, Beijing, Beijing Shi, China

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Publications (33)23.32 Total impact

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    ABSTRACT: In this work the influences of alkaline earth metals on cross-linking reactions (CLRs) during direct liquefaction of lignite were investigated. The oxidized lignite, which has been proved to be appropriate for quantitatively examine the extent of CLR during direct liquefaction, was used as a model coal to study the effects of ion-exchanged calcium, barium and magnesium on CLR during direct liquefaction of the oxidized lignite. Firstly, Chinese Yitai lignite (YT) was oxidized by nitric acid at 70°C and about 98% of the oxidized sample could be dissolved in tetrahydrofuran (THF) at room temperature. Then, ion exchange experiments were performed by soaking the oxidized coal in the solutions of calcium, barium and magnesium salts at elevated pH, respectively. At last, temperature-programmed liquefaction of the raw, the oxidized and the ion-exchanged coals were conducted under H2 atmosphere. The amounts of THF-insoluble solid products after liquefaction were used to quantitatively evaluate the CLR during liquefaction of the ion-exchanged coal. The results show that the oxidized coal is appropriate to quantitatively examine the extent of CLR and the targeted ions are exchanged to the oxidized coal in the form of highly-dispersed ion. The ion-exchanged Mg2+ suppresses the CLR during direct liquefaction of coal at both low and high temperature. However, the exchanged Ca2+ always promotes the CLR at the selected temperatures. While the exchanged Ba2+ promotes the CLR at low temperature, but suppresses it at high temperature.
    Fuel and Energy Abstracts 02/2012;
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    ABSTRACT: Cross-linking reactions (CLR) of oxygen groups during liquefaction of lignite were quantitatively studied by a new model system. Chinese Yitai lignite (YT) was first oxidized by nitric acid at 70 °C and about 98% of the oxidized sample could be dissolved in tetrahydrofuran (THF) at room temperature. Then benzyl alcohol, PhCH2OH (BA), as a model compound was added into the oxidized coal, also acted as solvent in the subsequent liquefaction. Temperature-programmed reactions (TPR) at liquefaction conditions under hydrogen atmosphere were performed to evaluate the CLR by quantitative analysis of THF-insoluble solid products (THFI) after reaction. Extensive CLR were observed even under high pressure of H2 at 200–400 °C, and more than 51.7% and 81.2% of the THFS fraction was converted into the THFI at 300 °C with tetralin (TET) and BA as solvent, respectively. The THFI fraction was almost solely caused by the CLR, which makes it possible to quantitatively study the CLR by analyzing the amount of the cross-linked solid products (CSP). The pyrolysis behaviours of CSP and oxidized coal were examined by TG. Other model compounds containing oxygen-functional groups (alcohol, phenol, carboxyl, carbonyl and ether groups) can also be used in this model system to study CLR of oxygen groups in low-rank coals.
    Fuel Processing Technology - FUEL PROCESS TECHNOL. 01/2010; 91(4):410-413.
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    ABSTRACT: A Chinese lignite, Yitai (YT) was pretreated by pyridine vapor and then purged by nitrogen gas to remove the pyridine which weakly interacted with coal. The effects of pyridine vapor treatment on the hydrogen bonds and the pyrolysis behavior of coal were studied by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) and TG-MS, respectively. The pyridine adsorption behavior of coal at room temperature was also studied. The results show that the pyridine vapor can break the hydrogen bonds in coal and form new stronger N–OH hydrogen bonds with oxygen function groups, resulting in N–OH hydrogen bonds slight increase and other hydrogen bonds decrease. When this swelled coal was pyrolyzed, the low-temperature cross-linking reactions that related to the hydrogen-bonded COOH–COOH and COOH-OH was suppressed due to the better thermal stability of the N–OH hydrogen bond in coal. This effect is reflected by the decrease in the yields of CO2 or H2O, and the larger weight loss difference between the raw and the pretreated coal during pyrolysis at the temperature below 400 °C.
    Journal of Analytical and Applied Pyrolysis 01/2010; 87(1):45-49. · 2.56 Impact Factor
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    Gang Wang, Wen Li, Baoqing Li, Haokan Chen
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    ABSTRACT: Pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer (TGA92) under syngas and hydrogen. The effect of different heating rates (5, 10, 15 and 20 {\textdegreeC/min) on the pyrolysis of these samples were examined. The pyrolysis tests of the synthesized samples (a mixture of the three components with different ratios) were also done under syngas. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics. It is found that syngas could replace hydrogen in hydropyrolysis process of biomass. Among the three components, hemicellulose would be the easiest one to be pyrolyzed and then would be cellulose, while lignin would be the most difficult one. Heating rate could not only affect the temperature at which the highest weight loss rate reached, but also affect the maximum value of weight loss rate. Both lignin and hemicellulose used in the experiments could affect the pyrolysis characteristic of cellulose while they could not affect each other obviously in the pyrolysis process. Values of k0 (frequency factor) change very greatly with different E (activation energy) values. The E values of sawdust range from 161.9 to 202.3 kJ/mol, which is within the range of activation energy values for cellulose, hemicellulose and lignin.
    Fuel. 04/2008; 87:552--558.
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    Xijie Chu, Wen Li, Baoqing Li, Haokan Chen
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    ABSTRACT: The sulfur transformation during pyrolysis and gasification of Shenhua direct liquefaction residue was studied and the release of H2S and COS during the process was examined. For comparison, the sulfur transfer of Shenhua coal during pyrolysis and that of pyrolyzed char during gasification were also studied. The residue was pyrolyzed at 10°C /min to 950°C. During pyrolysis about 33.6% of sulfur was removed from the residue, among which 32.1% was formed H2S in gas and 1.5% was transferred into tar, 66.4% of the sulfur was remained in residue char. Compared with coal, the residue has generated more H2S due to presence of Fe1−xS which was enriched in residue during liquefaction process. There is a few COS produced at 400–500°C during pyrolysis of coal, but it was not detected form pyrolysis of the residue. During CO2 gasification, compared with pyrolysis and steam gasification, there are more COS and less H2S formation, because CO could react with sulfide to form COS. During steam gasification only H2S was produced and no COS detected, because H2 has stronger reducibility to form H2S than CO. After steam gasification no sulfur was detected in the gasification residue. The XRD patterns show after steam gasification, only Fe3O4 is remained in the gasification residue. This indicates that the catalyst added during the liquefaction of coal completely reacted with steam, resulting in the formation of H2 and Fe3O4.
    Fuel. 01/2008; 87(2):211-215.
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    Gang Wang, Wen Li, Baoqing Li, Haokan Chen
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    ABSTRACT: Liquefaction of sawdust under syngas was performed in an autoclave and the effects of temperature, initial syngas pressure and reaction time on the product distribution of sawdust liquefaction were studied. The results using different solvents and atmospheres were also compared by product distribution and analyses of GC-MS, TG, IR and GPC. It was found that hydrogen donor solvent showed remarkable effect than either non-hydrogen donor solvent or without presence of solvent and its hydrogenation ability was much higher than gaseous hydrogen. Among various atmospheres H2 displayed higher activity than syngas and both of them were better than Ar and CO, while CO did not give the favorable influence. With increasing temperature and reaction time (10–30min) the oil yield increases, while less effect with increasing initial syngas pressure. The thermal decomposition of sawdust to form preasphaltene and asphaltene (PA+A) is a fast step, while longer reaction time is necessary for conversion of PA+A to oil as the 2nd step. The results also indicated that syngas can replace hydrogen in sawdust liquefaction.
    Fuel. 01/2007; 86(10):1587-1593.
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    Zongqing Bai, Haokan Chen, Baoqing Li, Wen Li
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    ABSTRACT: Methane decomposition over Ni loaded activated carbon (AC) was investigated in a fixed-bed reactor, and the results were compared with those of the individual methane decomposition over AC. XRD results show that there is no NiO observed, and only Ni metal crystallite is found in the catalyst even if it is calcined in Ar, which eliminates the inevitable reduction step with other supports. When Ni is loaded on AC, the Ni/AC catalyst shows higher activity in methane decomposition than the original carbon. Ni crystal size increasing and the new crystallite Ni3C formation during the process lead to the deactivation of the catalysts. Filamentous carbon formation is observed and interlaced with the deactivated catalyst surface at moderate condition with low amount of Ni loaded. Temperature has great effect on the catalytic performance of Ni/AC catalyst and the formation as well as the characterization of the filamentous carbons.
    International Journal of Hydrogen Energy. 01/2007;
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    Fenrong Liu, Wen Li, Haokan Chen, Baoqing Li
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    ABSTRACT: Two Chinese coals, Liuzhi high pyrite coal with high ash content (LZ) and Zunyi high organic sulfur coal (ZY), were pyrolyzed in a fixed-bed reactor under nitrogen and hydrogen at temperature ranging from 400 to 700°C. The effects of heat rate, temperature and gas atmosphere on sulfur transformation and sulfur uneven distribution were examined by XPS combined with traditional sulfur analysis method. The ratio of surface S to bulk S is used to describe the uneven distribution of sulfurs. It is found that oxygen is rich on the surface, while S in the bulk. The increasing ratio of surface S to bulk S with increasing temperature clearly indicates the sulfur transfer from the bulk to the char surface during pyrolysis. The ratios are higher at all temperatures studied for ZY coal than for LZ coal, which may be related to the higher ash content in LZ coal. The ratio of surface S to bulk S increases with increasing heating rate for LZ coal, while it decreases for ZY coal. In the presence of H2, the S on the surface is much lower than that under N2 and surface S in sulfidic, thiophenic and sulfoxide forms is totally disappeared for LZ coal at various temperatures and heating rates, while the surface S in thiophenic and sulfoxide forms is not totally disappeared for ZY coal, which may be related to the high rank of ZY coal. The ratio of surface S to bulk S decreases before 600°C with increasing temperature for both coals in the presence of H2, showing that gaseous H2 can easily react with the surface S to form H2S, while above 600°C it increases because the supply of H2 cannot match the rate of formation of HS free radicals at high temperature.
    Fuel. 01/2007; 86(3):360-366.
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    ABSTRACT: Sawdust loaded with 1wt.% Mo catalyst was liquefied in a 250ml autoclave at 300°C, initial gas pressure of 2.0MPa and reaction time of 30min in attempt to produce more liquid fuels. The effects of different catalyst preparation methods including mechanical mixing, impregnation and ultrasonic treatment with or without solvents on liquefaction were compared. The effect of atmosphere and temperature was also examined. The results show that the highest yield of oil and lowest yield of preasphaltene and asphaltene are obtained using the sample loaded catalyst with ultrasonic treatment than those with impregnation or mechanical mixing no matter with or without solvents due to the well dispersion of the catalyst. Solvent, especially a hydrogen-donor, plays an important role in sawdust liquefaction, while gaseous hydrogen itself displays less action in promoting hydrogenation reaction and enhancing catalyst ability. Gaseous hydrogen and catalyst do show significant functions in the presence of solvent. Higher temperature is favorable of thermal decomposition, hydrogenation and hydrocracking reactions. Based on the experimental results, a two-step liquefaction mechanism is proposed.
    Chemical Engineering and Processing - CHEM ENG PROCESS. 01/2007; 46(3):187-192.
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    Qinglei Sun, Wen Li, Haokan Chen, Baoqing Li
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    ABSTRACT: The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H2, heating rate of 10°C/min and final temperature of 900°C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H2O, C1–C4, and C6H6. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H2O and light hydrocarbons was higher in H2 than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H2O and CH4 had different peak distributions and evolution temperatures under H2 and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.
    Energy Sources 10/2006; Part A(Vol. 28):1281-1294. · 0.54 Impact Factor
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    Qinglei Sun, Wen Li, Haokan Chen, Baoqing Li
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    ABSTRACT: The pyrolysis of Shenmu coal macerals was performed in TG151 thermobalance. The volatile matter evolved in primary and secondary devolatilization and devolatilization kinetics were studied. The volatile matter evolved during primary devolatilization is the major part of the total volatile matter, especially for vitrinite. The percentage of volatile matter evolved during primary and secondary devolatilization suggested that inertinite have higher thermal stability. Though the heating rate can affect the percentage of volatile matter evolved during primary and secondary devolatilization, the order of volatile matter in all the temperature range is the same: vitrinite > parent coal > inertinite. The kinetic analysis of devolatilization using distributed activation energy model (DAEM) shows that the activation energy existed relatively large error at the conversion of initial 10% and final 10%. And the conversion of 10% to 90% was used to describe the variation of activation energy during pyrolysis. The activation energy of vitrinite appeared a minimum of about 50% conversion, but that of inertinite always increased as pyrolysis went on, indicating the different structure and chemical composition between them. Inertinite has higher activation energy and lower pyrolysis rate than vitrinite.
    Energy Sources 07/2006; Part A(Vol. 28):865-874. · 0.54 Impact Factor
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    ABSTRACT: The transformation behavior of mercury in two Chinese coals (WJP and HYS coal) during sub-critical water treatments was studied in a semi-continuous apparatus. Float–sink method, demineralization and sequential chemical extraction were used to study the occurrence mode of mercury in raw coals and extracted samples. The results show that with increasing temperature, pressure, water flow and extraction time, the removal of mercury increases. During sub-critical water treatment, the content of mercury associated with sulfates, monosulfides, disulfides, organic material, and insoluble forms decreases. The removal efficiency of mercury is almost 100% at 410 °C, 15 MPa, 0.58 l/h, and 60 min for HYS coal and 96.7% at 380 °C for WJP coal. Under the same temperature and pressure the mercury removal through pyrolysis is less than that through sub-critical water extraction which is an efficient method to remove most mercury from coal.
    Fuel Processing Technology - FUEL PROCESS TECHNOL. 01/2006; 87(5):443-448.
  • Zongqing Bai, Haokan Chen, Wen Li, Baoqing Li
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    ABSTRACT: The aim of this work was to use low-cost coal char without further activation as a catalyst for hydrogen production by methane decomposition in a fixed bed reactor. The kinetic of methane decomposition was investigated preliminarily and the changes of surface properties were also studied. The results show that the lignite char has a much higher activity in methane decomposition than bituminous and anthracite ones and its initial rate is not less than that of activated carbon under the same condition. The temperature of the preparation of char has an effect only on the initial activity of char in methane decomposition, while the reaction temperature influences the activity and the stability of char greatly. The ash in coal also has little effect on the catalytic activity of char in methane decomposition. The initial reaction order of methane decomposition over coal char is 0.5 which is the same as that over activated carbon. And the activation energy is about 89–105kJmol-1 which is much lower than the methane C–H bond dissociation energy of 440kJmol-1. Methane decomposition over coal chars occurs mainly within its micropores. Using low-cost coal char as a catalyst is a promising method for hydrogen production by methane decomposition both economically and environmentally.
    International Journal of Hydrogen Energy - INT J HYDROGEN ENERG. 01/2006; 31(7):899-905.
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    Wei Yuchi, Baoqing Li, Wen Li, Haokan Chen
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    ABSTRACT: The effects of coal characteristics on the properties of coal water slurry (CWS) were systemically studied using sixteen Chinese coals of different ranks from lignite to anthracite. The correlation between coal properties and CWS characteristics were investigated by multivariate progressive regression analysis. CWS properties examined in this study included slurryability (concentration of slurry that gives an apparent viscosity at 1200 mPa · s at a shear rate of 28.38 s), rheological behavior (represented by a flow index), and static stability (days for formation of soft sediment). Coal properties examined in the study included coal rank, air equilibrium moisture (Mad), maximum moisture holding capacity (MHC), ash content, surface properties, petrographic macerals, pore structure, and adsorption characteristics of dispersants.
    Coal Preparation 10/2005; 25(4):239-249. · 0.08 Impact Factor
  • Wen Li, Hailiang Lu, Haokan Chen, Baoqing Li
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    ABSTRACT: The volatilization behavior of chlorine in three Chinese bituminous coals during pyrolysis and CO2-gasification in a fluidized bed reactor was investigated. The modes of occurrence of chlorine in raw coals and their char samples were determined using sequential chemical extraction method. The Cl volatility increases with increasing temperature. Below 600 °C the Cl volatility is different, depending on the coal type and the occurrence mode of Cl. Above 700 °C, the Cl volatilities for the three coals tested are all higher than 80%. About 41% of the chlorine in Lu-an coal and 73% of that in Yanzhou coal are organic forms, and most of them are covalently-bonded organic chlorine, which shows high volatile behavior even at low pyrolysis temperatures (below 500 °C), while the inorganic forms of chlorine in two coal samples are hardly volatilized even at low pyrolysis temperatures (below 400 °C). The restraining efficiency of addition of CaO on chlorine volatility is greatly dependent on pyrolysis temperature. The optimal restraining efficiency can be obtained at temperature range from 450 to 650 °C during pyrolysis of Lu-an coal. The volatile behavior of Cl is mainly dependent on temperature. Above 700 °C high volatility of Cl is obtained in both N2 and CO2 atmospheres.
    Fuel. 10/2005; 84(s 14–15):1874–1878.
  • Zongqing Bai, Haokan Chen, Baoqing Li, Wen Li
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    ABSTRACT: Methane decomposition over activated carbons was carried out in a fixed bed, quartz-tube flow reactor. The kinetics of methane decomposition and surface properties changes before and after reaction was investigated. As a non-carbon based material, active alumina was also used to compare and understand the catalytic decomposition mechanism of methane over different materials. A reaction order of 0.5 is obtained for methane decomposition over ACs and activation energies in the range from 117 to 185 kJ mol−1. The pore size change in the course of methane decomposition over activated carbons indicates that the catalytic reaction occurs mainly in the micropores. Activated alumina has different pore properties and carbon deposition in mesopores of the alumina is responsible for the catalytic activity.
    Journal of Analytical and Applied Pyrolysis. 06/2005;
  • Wen Li, Hailiang Lu, Haokan Chen, Baoqing Li
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    ABSTRACT: The volatilization behavior of fluorine in five Chinese coals was investigated during fluidized-bed pyrolysis and CO2-gasification at a temperature range of 500–900 °C. The effect of co-existed and added calcium on fluorine volatility during pyrolysis was also determined. With increasing pyrolysis temperature, the volatility of fluorine increases. However, the volatility is greatly dependent on the fluorine chemical forms occurred in coal. Except for Datong and Zhungeer coal, more than 65% of fluorine in other three coals occurs as the steady forms. Fluorapatite is not the major carrier of fluorine in the coals studied. Fluorine volatility is retarded by coexisting calcium during coal pyrolysis, indicating that at least part of the stable forms of fluorine in coal might occur as calcium fluoride or calcium fluoride with complex compounds which are stable even at high pyrolysis temperature. The addition of CaO and limestone can suppress the release of fluorine during pyrolysis. The effect of CaO is better than that of limestone. The volatility of fluorine of coal during CO2-gasification depends on not only the occurrence mode of fluorine, but also the gasification reactivity of the coal. Compared with N2 atmosphere, CO2 is more favorable to the release of fluorine from coal.
    Fuel. 03/2005; 84(4):353–357.
  • Shuwen Gong, Haokan Chen, Wen Li, Baoqing Li
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    ABSTRACT: β-Mo2N0.78 catalyst was synthesized via the temperature-programmed reaction between N2–H2 mixture gases and molybdenum oxide. The influences of the synthesis conditions on catalyst structure and catalyst hydrodesulfurization (HDS) behavior were also studied. H2-TPR experiment was used to investigate the structure changes of catalyst before and after HDS reaction. Preparation results showed that β-Mo2N0.78 can be formed at a final nitriding temperature of 923–1023K and N2/H2 ratios of 1/4–1/1. The formation of MoO2 intermediate results in the low surface area β-Mo2N0.78 product. The thiophene HDS result indicated that β-Mo2N0.78 also has HDS catalytic activity. Its bulk structure is retained after HDS reaction although sulfur replaces the surface oxygen as determined by TPR examination. Pre-reduction does not improve the HDS activity of passivated β-Mo2N0.78 although hydrogen reduction can remove the oxygen from surfaces. The catalytic activity of passivated nitride decreases with the increasing of final nitriding temperature from 923 to 1123K, and there is a suitable N2–H2 ratio to prepare high activity β-Mo2N0.78 catalyst.
    Applied Catalysis A-general - APPL CATAL A-GEN. 01/2005; 279(1):257-261.
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    Rengui Guan, Wen Li, Haokan Chen, Baoqing Li
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    ABSTRACT: The effects of iron and calcium compounds on NO emission during CZC (carbazole char) gasification under different O2 concentrations have been investigated in a quartz tube fixed bed reactor. Temperature-programmed gasification was preformed to determine the influence of O2 concentration and catalytic effects of iron and calcium on NO emission. The results show that the O2 concentration strongly influences NO emission during CZC gasification; suitable O2 concentration could largely reduce NO emission, but high or low O2 concentration is unfavorable to reduce NO pollution. Iron catalysts increase NO emission during CZC gasification in O2 concentration ranging from 20.9 to 1.2%, and their catalytic effects are strongly depended on O2 concentration. The order of their catalytic effects is Fe(AC)2>FeCl2≈FeCl3. Different kinds of iron compounds show different catalytic activities for their different dispersion on CZC and their different decomposition tendency to form active sites. Calcium compounds show different effects on NO emission depending on O2 concentration. Ca(AC)2 and CaCl2 increase NO emission under high O2 concentration (such as 20.9%), but they decrease NO under low O2 concentration (such as 1.2%). When CZC gasification under 4.8% O2–Ar, Ca(AC)2 decreases NO emission, but CaCl2 increases NO emission.
    Fuel. 01/2005; 84(17):2178-2183.
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    ABSTRACT: γ-Alumina-supported β-Mo2N0.78 catalyst was synthesized by the temperature-programmed nitriding reaction and tested to determine its catalytic activity and selectivity during the hydrodesulfurization (HDS) of dibenzothiophene. The results indicated that the conversion increases with reaction temperature and hydrogen pressure. And increasing the hydrogen pressure results in more hydrogenation, but increasing reaction temperature can improve the two parallel pathways of direct desulfurization and hydrogenation desulfurization at same degree. Sulfur can replace the surface oxygen of passivated nitride in the HDS reaction although the bulk structure is preserved.
    Journal of Molecular Catalysis A-chemical - J MOL CATAL A-CHEM. 01/2005; 225(2):213-216.

Publication Stats

171 Citations
23.32 Total Impact Points

Institutions

  • 1999–2012
    • Northeast Institute of Geography and Agroecology
      • • State Key Laboratory of Coal Conversion
      • • Graduate School
      • • Institute of Coal Chemistry
      Beijing, Beijing Shi, China
  • 2003–2010
    • Chinese Academy of Sciences
      • State Key Laboratory of Coal Conversion
      Peping, Beijing, China
    • Dalian University of Technology
      Lü-ta-shih, Liaoning, China