Abstract: This review introduces the recent progresses made in the study of direct reaction and hydrocarbon-pool mechanisms for the C-C bond formation in the conversion of methanol over acid molecular sieves. It also involves in the main theoretical and experimental methods. The dehydration mechanism of methanol and the problems of direct reaction and hydrocarbon-pool mechanisms are also analysed. In addition, the effect of molecular sieve pore structures on the hydrocarbon-pool species and their reaction mechanism was evaluated.
Abstract: Biomass pyrolysis and Maillard reaction were discussed in this article. Maillard reaction existed not only in biomass pyrolysis, but also could be facilitated to produce high value-added compounds, such as pyrazine by adding defined ammonia. The condensable gas was condensed into two types of bio-oil which could be used for chemical and fuel, respectively. The former could be served as material to obtain valuable chemicals by separation and extraction, while the latter could be used to burn in boiler or kiln. The economy of biomass fast pyrolysis process would be considerably improved when the Maillard reaction was introduced.
Abstract: To investigate the variation in gasification reactivity and microstructure of char from the multi-circulation fluidized bed gasifier, 3 chars from different rank coals were gasified in a simulated multi-circulated reactor (rapid heating-up fixed bed). The carbon conversion was calculated from the weight of residues, and the structure was analyzed by pore and XRD analyzer. The results show that with the increase of cycle time, the carbon conversion of low rank HLH lignite char increases while that of SM bituminous and JC anthracite chars decrease. The evolutions of BET surface area and micropore area have a peak value with the circulate time. The variation of graphitization is similar with the carbon conversion, which can be considered as the key factor to determine the carbon conversion.
Abstract: The liquefaction behaviors of Xianfeng lignite (XL) in ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate ([Bmim]BF4) under mild condition-350 ℃ were studied. The effect of catalysts (FeS, ZnCl2, AlCl3 and FeCl3) on the XL liquefaction in [Bmim]BF4 were investigated and the liquefaction products obtained were analyzed by FT-IR spectra. It is found that the XL has a good hyrogenation activity in the presence of [Bmim]BF4, catalysts and tetralin (THN). XL liquefied product yield reaches to about 66.2% and the main liquefaction product is heavy fraction-tetrahydrofuran soluble (THFS) and tetrahydrofuran insoluble/N-methyl-2-pyrrolididinone soluble fractions (NS). The analyses of liquefied product by FT-IR show that the type of catalyst significantly affects the distrubution and structure of liquefied product.
Abstract: Ionic liquid-assisted coal water slurry (CWS) electrolysis was carried out in KNO3 system with constant current. The effects of ionic liquids including structure, concentration, temperature and time on the removal of sulfur were investigated to intensify desulfurization ratio from CWS electrolysis. Given the organic structure of imidazole, the influence of anions on the desulfurization was in the following order: Br->BF4- >Cl-. Given the same anion of Br-, imidazole showed better performance than pyridine in terms of sulfur elimination. With increasing N-butylpyridinium bromide ([BPy]Br) concentration, the desulfurization ratio increased at the initial stage, and then decreased after 0.30 mol/L. Additionally, the desulfurization ratio continuously increased with time and temperature. Finally, the organic sulfur occurrences in coal before and after experiments were characterized by XPS technique. Results showed that the removal of thiophene was improved due to the extraction-oxidation effects and others (i.e. thioethers and sulfoxide) were removed mainly via enhanced oxidation and hydrolysis reactions.
Abstract: To improve the quality of tar, and reduce the heavy fraction (whose boiling points are greater than 360 ℃) in the tar, the lignite fast pyrolysis process using olivine and Co-impregnated olivine (Co/olivine) as the solid heat carrier was investigated in a fixed bed reactor over the temperature range 450~600 ℃. The effects of olivine and Co/olivine on the product yield, gas composition and tar fraction were examined. The results show that Co/olivine leads to a decrease in heavy oil fraction content, but an increase in tar yield. Co/olivine makes an increase in tar yield by 19.2% compared to the silica sand, while a decrease in heavy oil fraction content by 17.0% compared to the olivine at 550 ℃. The yield of light oil can reach up to 5.1%, however, the content of light oil, phenol oil and naphthalene oil increases by 19.6%, 17% and 15.2%, respectively. Meanwhile, the content of H2 and CH4 in gaseous product is obviously decreased.
Abstract: Series of non-precious metal catalysts Ni-WO3/SBA-15 were prepared by means of incipient impregnation and applied to the hydrogenalysis of cellulose in aqueous solution. The effect of reaction temperature on the hydrolysis and morphology of cellulose, and the influence of Ni, WO3 loading on the conversion of cellulose were investigated. High crystalline cellulose was transformed gradually into amorphous state with the increase of reaction temperature. H2 temperature program reduction of the catalyst proved that a strong interaction existed between nickel and tungsten trioxide, which enhanced the ability of tungsten species to the cleavage of C-C bond and the activity of hydrogenation of nickel. Thus, the transformation of cellulose into ethylene glycol was strengthened markedly. The complete conversion of cellulose and 70.7% ethylene glycol yield were obtained over a 3%Ni-15%WO3/SBA-15 catalyst under the reaction condition of 230 ℃and 6.0 MPa H2 for 6.0 h.
Abstract: The pyrolysis of K2CO3-impregnated hemicelluloses, cellulose, lignin and pine was investigated by TG-FTIR to assess the influence of potassium on the pyrolysis mechanisms of the main components of biomass. The results show that the pyrolysis temperature range of hemicelluloses, cellulose and lignin is 200~350 ℃, 300~365 ℃,200~600 ℃, respectively. CO and CO2 are mainly produced during hemicellulose pyrolysis, and levoglucosan and carbonyl group are mainly produced during cellulose pyrolysis, while solid product is the main product for lignin pyrolysis. The pyrolysis of the mixture of three components reveals that there are interactions among biomass components. Potassium could catalyze the pyrolysis process of hemicelluloses and cellulose, lower the pyrolysis temperature, and increase the char yields. Potassium influences the pyrolysis of cellulose most obviously, leading to a marked increase in the yields of CO, CO2 and solid product, and a decrease in carbonyl compound yield. However, potassium has little effect on the char yield of lignin, and the catalysis of potassium for the pyrolysis of mixture weakens.
Abstract: The bio-char from cotton stalk and sawdust was prepared using a tubular fixed bed, and the combustion characteristics of the resulted bio-chars were analyzed with a thermogravimetric analyzer. Based on the comprehensive reaction rate equation, the gas-solid reaction mechanism of the bio-char combustion was deduced, and the thermogravimetric data of the bio-char combustion were fitted. The results indicate that as the carbonization temperature increases, the ignition temperature and burnout temperature of the bio-chars increase, while the combustion performance index (S) decreases. The combustion characteristics of the cotton stalk charcoal are better than that of the sawdust charcoal. The reaction mechanisms for the cotton stalk charcoal combustion are different in different temperature ranges. The charcoal combustion in lower temperature range follows the planar internal diffusion reaction mechanism, while the globular interface reaction mechanism applies to higher temperature range. The combustion reaction of sawdust charcoal follows globular interface reaction mechanism during the whole oxidation process. The reaction reactivity of bio-char combustion can't be judged by the calculated activation energy.
Abstract: Zr-doped Ni/γ-Al2O3 catalyst was prepared by co-impregnation of Ni and Zr on γ-Al2O3; over it, the methanation of syngas at low temperature (300~330 ℃) in a slurry reactor was investigated. Compared with single NiO and Ni/γ-Al2O3, the catalytic performance of the Zr-doped Ni/γ-Al2O3 is greatly improved. Under optimized condition, a high CO conversion of 86.41% and a selectivity of 90.53% to CH4 are achieved at a GHSV of 4 200 mL·g-1·h-1. XRD, TEM and H2-TPR results suggest that the doping of Zr promotes dispersion of Ni on γ-Al2O3, weakens the interaction between Ni and the support and suppresses the formation of NiAl2O4 spinel with low methanation activity; all these may contribute to the excellent performance of the Zr-doped Ni/γ-Al2O3 catalyst in syngas methanation.
Abstract: Two Ni-based catalysts of 13%Ni/SiO2(13Ni/Si) and 7%Ni-2%Ce/SiO2(7Ni-2Ce/Si, by weight) were prepared by the incipient-wetness impregnation method and characterized with N2-sorption, XRD, H2-TPR, FT-IR, TEM, H2-TPD and CO-TPD techniques. It was shown that addition of Ce promoter generated an interaction among NiO, CeO2 and SiO2, which changed chemical environment of Ni-O-Si bond, enhanced the dispersion and reduction of NiO, and increased the active surface area. In particular, a new type of moderately strong CO adsorption sites was formed on the surface of the 7Ni-2Ce/Si catalyst. As a result, the low Ni-loading 7Ni-2Ce/Si catalyst exhibited higher CO adsorption capacity and CO methanation catalytic activity than the high Ni-loading 13Ni/Si. Under the reaction conditions of 1% CO (volume fraction in H2 atmosphere), GHSV of 7 000 h-1 and atmospheric pressure, the temperature for complete conversion of CO over the 7Ni-2Ce/Si catalyst was 230 ℃, being 30 ℃ lower than that found over the high Ni loading 13Ni/Si catalyst.
Abstract: A comprehensive thermodynamic analysis was made on the carbon deposition behavior for the production of substitute natural gas (SNG) through syngas methanation. The component concentrations and the equilibrium constants of ten reactions involved in the syngas methanation were calculated at different temperatures; the effects of temperature, pressure, and the addition of other compounds in the feed gas on the behavior of carbon deposition were investigated. The results indicated that the catalyst bed is prone to carbon deposition at 550~800 ℃ and 0.1~1.5 MPa; as a result, lower temperature, higher pressure, and a larger H2/CO ratio are suitable for the methanation reactions. The addition of steam in the feed gas may alleviate the carbon deposition to a large extent, whilst a large amount of CO2 or CH4 in feed gas may lead to carbon deposition.
Abstract: The CuPc/Y which is copper phthalocyanine encapsulated inside the supercage of zeolite-Y was prepared with copper dichloride, ammonium molybdate, phthalic anhydride, urea and NaY molecular sieve by means of phthalic anhydride-urea solid state synthesis method. By using CuPc/Y as support, Pd-CuPc/Y composite catalyst was prepared by equivalent-volumetric impregnation method. The catalytic activity of the composite catalyst for selective aerobic oxidation of methane to methanol in acetic acid solvent was investigated. The results showed that the catalytic performance of the composite catalyst was related to reaction temperature, volume ratio of CH3COOH to H2O in acetic acid solvent, amount of p-benzoquinone and reaction time. The optimal yield of methanol was 1 840 μmol under the reaction conditions: 0.5 g of 0.5%Pd-0.5%CuPc/Y, 4 to 1 of volume ratio of CH3COOH to H2O in acetic acid solvent, 1 000 μmol of p-benzoquinone, 3 h of reaction time and 150 ℃ of reaction temperature. Pd-CuPc/Y catalyst could be reused repeatedly. However, the catalytic activity of reused catalyst decreased by catalyst loss and Pd particle aggregation. The selective oxidation of methane catalyzed by Pd-CuPc/Y catalyst in acetic acid solution possibly involved electrophilic substitute reaction and reactive oxygen species oxidation reaction.
Abstract: Hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) on unsupported NiMoW catalyst was studied. Moreover, mechanisms and reaction networks were revealed on the basis of GC and GC-MS analyses of the reaction products. The result shows that, the HDS rate of dibenzothiophenes is in the order of 4,6-DMDBT≈4-MDBT＜DBT for the spatial restraining effect of the methyl group. Unsupported NiMoW catalyst has high hydrogenation activity in aromatics saturation, it favours the hydrogenation of alkyl-substituted aromatic ring, weakens the spatial restraining effect, leads to the effectively removing of alkyl-substituted dibenzothiophenes. The hydrodesulfurization products of DBT could be hydrogenated further and its distribution is similar to the hydrogenation products of biphenyl(BP). The hydrogenation route of the hydrodesulfurization of 4-MDBT have two reaction pathways, the electron donor induction of the methyl group could promote the hydrogenation of the adjacent phenyl. On the lewis acid sites of catalyst, part of 4-MDBT and 4,6-DMDBT transformed into DBT through the demethylation reaction in their hydrodesulfurization process.
Abstract: A series of catalysts were prepared by calcination of copper(II) hydroxide and pseudo boehmite with a Cu/Al molar ratio of 1/2. When the calcination temperature was raised from 500 ℃ to 900 ℃, the main component of the catalysts varied from CuO to CuAl2O4, and the catalyst surface area declined from 75.0 to 16.6 m2/g. The catalysts, with CuAl2O4 as main component and high surface area, showed excellent catalytic performance in methanol steam reforming reaction (MSR). In addition, the catalyst, with CuAl2O4 as main component, had the copper releasing as well as sintering, hence the catalytic activity increased first and then decreased. The preferred catalyst was calcined at 800 ℃ and had better catalytic performance than commercial Cu-Zn-Al. Meanwhile, this catalyst can be regenerated after MSR. When the catalyst was not pre-reduced, the methanol conversion was 55.2% at the beginning, and then increased to 79.3% at 288.3 h, and decreased to 63.9% at 1 000.5 h, when reaction conditions were the molar ratio of alcohol to water 1, 240 ℃, 1.0×106 Pa, WHSV of 1.75 h-1.
Abstract: A core-shell catalyst CuO-ZnO-Al2O3@Al2O3 for one-step synthesis of dimethyl ether from synthesis gas was prepared using glucose, sucrose or starch as template, and characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The thickness of the Al2O3 shell in the catalyst was altered by controlling the synthesis condition, such as temperature and time. The catalytic performance of dimethyl ether (DME) synthesized from CO hydrogenation on the catalysts were investigated. The conversion of CO and the selectivity of DME on CuO-ZnO-Al2O3@Al2O3 achieved 35.2% and 61.1% at 260 ℃, 5.0 MPa and 1 500 mL/(h·gcat), respectively.
Abstract: Direct synthesis of liquefied petroleum gas (LPG) from syngas could be realized over a hybrid catalyst consisting of methanol synthesis catalyst and zeolite. In this work, SAPO-5 was chosen consciously for LPG synthesis, because its pore size (0.73 nm×0.73 nm) is similar to that of Y zeolite. As expected, the corresponding hybrid catalyst of SAPO-5 exhibits high selectivity (73.0%) to LPG, which confirms the previous deduction that large pore size of zeolite was beneficial to LPG synthesis. In addition, as one step process of syngas to LPG, the formation of hydrocarbons from methanol or dimethyl ether follows the hydrocarbon pool mechanism.
Abstract: The supported NiO-Fe2O3/modified dolomite (NiO-Fe2O3/MD) catalysts were prepared by deposition-precipitation (DP)method using modified dolomite as carrier, and different approaches including XRD, SEM, TEM and BET were used to characterize the synthetic catalysts. Meanwhile, the catalytic gasification of municipal solid wastes (MSW) was conducted to test the catalytic activity and life of NiO-Fe2O3/MD catalyst in a bench-scale combined fixed bed reactor, and compared with the catalytic properties of NiO/MD catalysts. The results indicated that the prepared NiO-Fe2O3/MD catalysts had a coated core-shell structure, the particles size of the active components in catalyst surface were about 37 nm, and they had also a high BET surface area of 62.48 m2/g. The catalytic activity testing showed that the NiO-Fe2O3/MD catalysts using in gasification of MSW had a very high catalytic activity, which could significantly improve the quality and H2 yields of the produced gas, meanwhile efficiently eliminate the tar generation. Comparing with NiO/MD catalyst, the NiO-Fe2O3/MD catalyst demonstrated its unique property in preventing deactivation to attain a longer lifetime.
Abstract: The effect of limestone addition on the emission characteristics of PM2.5 (particulates with aerodynamic diameter less than 2.5 μm) was studied in a fluidized bed combustor. The combustion tests were carried out at 1 123 K under O2/CO2 atmosphere. The PM2.5 generated from coal combustion was collected and analyzed with an Electrical Low Pressure Impactor (ELPI). The results indicate that limestone has a great effect on the formation of PM2.5 during coal combustion under O2/CO2 atmosphere. The concentration of PM1.0 is diminished; but the concentration of PM1.0~2.5 is enhanced slightly with the addition of limestone. The mass size distribution of PM2.5 is similar, which displays two peaks around 0.2 and 2.0 μm, respectively. As the molar ratio of Ca/S increases, the concentrations of Si, Na, K, S, and Cu decrease. As the particle size decreases, the concentrations of S, Cu, K, and Na increase, but the concentrations of Si decrease.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
