Abstract: Influence of two kinds of industrial ashes with high carbon and calcium-rich as additives (drying ash and fly ash) on slagging characteristics for blends of high and low sodium coals was studied in detail. Experiments were performed including ash fusion temperature tests, ashing for blending coals with/without additives in a fixed bed furnace and slagging on un-cooled probe in a drop tube furnace. The results show that there is a large amount of amorphous silicon at 1000 ℃ during combustion of raw blending coals, which easily leads to low-temperature eutectic reaction at higher temperature. Adding 5% fly ash can raise soften temperature of the blended coal ashes by 100 ℃, and mass ratio of CaO to SiO2 in ashes reaches up to 2.5. Dicalcium silicate and grossular are newly generated, which effectively reduce the slagging propensities. The main phase in slag samples collected on the probe is identified as gehlenite after adding two industrial ashes into raw blending coals. The addition of two typical ashes can transform amorphous silicon into its crystalline mineral phase, inhibit formation of low-temperature eutectics. In contrast to the case of adding 5% fly ash, impact of adding 5% drying ash into raw blending coals on slagging tendency of the ash particles on un-cooled probe is insignificant.
Abstract: Shenhua bituminous coal and corn stalks were selected as experimental materials, and the effects of biomass blending ratio on the ash melting characteristics and viscosity-temperature characteristics of Shenhua bituminous ash in a weakly reducing atmosphere were studied. The mineral composition and micro-morphology of ash were detectd by XRD and SEM, and the phase and mineral transformation of ash at different temperatures were simulated by thermodynamic software FactSage. The results indicate that with the increase in corn stalks addition, the contents of high melting point quartz, anorthite and cordierite in ash decrease, and the content of low melting point potassium feldspar increases. Besides, the critical viscosity temperature (tcv), the lowest operation temperature (tlp) of ash and the viscosity of slag reach to the minimum values as the blending ratio of corn stalk to Shenhua coal is 20%. When the temperature arrives at 1255 ℃, the value of viscosity is less than 25 Pa·s, which can meet the liquid slag discharging requirements of the gasifier. Combining the Urbain homogeneous model with the Einstein-Roscoe heterogeneous model and using the FactSage software to calculate the liquid phase content at different temperatures, an empirical formula for the viscosity prediction of the corn stalks and Shenhua bituminous coal mixed gasification slag has been obtained.
Abstract: A lignite-based porous carbon was prepared by KOH solution extraction and subsequently by an activation of the extractant with Baoqing lignite as the raw material, and the composite capacitive materials combining the porous carbon with CoNi2S4 were fabricated by a facile hydrothermal method. The effect of different carbon material ratios on the electrochemical performance of lignite-based porous carbon/CoNi2S4 composites was investigated. The results indicate that too high or too low carbon content is not conducive to an improvement in the specific capacitance of the composites, while the lignite-based porous carbon/CoNi2S4 composites with 37% of carbon have higher specific capacitance and better cycling performance. The specific capacitance of the composites is as high as 1318.2 F/g at a current density of 4 A/g, and the capacitance retention is 80.9% after 4000 cycles.
Abstract: Five dispersed molybdenum, nickel and cobalt oil soluble homogeneous catalysts were synthesized. The hydrogenation of coal tar pitch was under the conditions of 370 °C, 10 MPa hydrogen pressure, and 4 h reaction time in an autoclave reactor. The effects of molybdenum naphthenate addition, molybdenum nickel and molybdenum cobalt bimetallic ratios on hydrogenation were investigated. The catalytic hydrogenation effect was evaluated by the liquid yield. A variety of analytical methods, such as elemental analysis, ICP-MS, TEM, XPS, and four component separation, were used to explore the optimal catalytic system for the slurry bed hydrogenation of coal tar pitch. The results show that the optimal catalytic system is molybdenum naphthenate and nickel naphthenate ratio of 1∶1 at catalyst amount of 2×103. Under optimal conditions, the liquid yield is 85.3%, the residue yield is 10.6%, and the gas yield is 4.1%.
Abstract: The co-pyrolysis behavior of two low rank coals (Inner Mongolia Xinghe coal, Xiaolongtan coal) and three common biomasses (straw, sunflower, apple tree branches) was investigated by non-isothermal thermogravimetric analysis and fixed bed experiments. The results show that whether the co-pyrolysis of biomass and coal has synergistic effects is closely related to the type and the adding amount of biomass. The synergistic effect during the co-pyrolysis of Inner Mongolia Xinghe coal and apple tree branches at the mixing proportion 2∶1 is found to be the most obvious, which is further proved by an analysis of co-pyrolysis products in a fixed bed. The analysis results of tar component show that the content of oxygenated compounds in tar increases, but the amount of hydrocarbons decreases. The co-pyrolysis can increase the yield of tar but it cannot improve the quality of tar.
Abstract: To enhance the catalytic effect of dolomite, La/Dol catalyst was prepared by impregnation modification of dolomite with La (NO3)3 as additive. The catalyst was characterized by BET, SEM and XRD. With pine rods as raw materials and La/Dol as reforming catalysts, the effects of gasification temperature and La amount of catalysts on the catalytic gasification of pine were compared and analyzed in a self-made two-stage biomass gasification reforming experimental furnace. The results show that a small amount of La (2%) can obviously promote the forward progress of water gas reaction and perfect the catalytic reforming effect. Under the working condition of steam flow rate of 10 g/min, 2-La/Dol catalyst and reforming temperature of 750℃, with the increase of gasification temperature, the amount of H2 increases significantly, and the highest volume fraction of H2 increases from 28.51% (0-La/Dol) to 41.72% (2-La/Dol). La2O3 in the catalyst promotes the secondary cracking of tar. As a result, the tar content of liquid phase product is obviously reduced, and the number of functional groups is also reduced. La2O3 on dolomite surface occupies active sites, so carbon filaments are not suitable for accumulation and carbon deposition is inhibited. Carbonate (La2O2CO3) in the catalyst can react with carbon to slow down the carbon deposition on the surface and improve the activity and service life of the catalyst.
Abstract: Co-MOF was firstly prepared by solvothermal method, and then Co@C catalyst was prepared by one-step pyrolysis method from Co-MOF. The structure of Co@C catalyst was characterized by N2 physical adsorption-desorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Effects of Co-MOF pyrolysis temperature, reaction temperature, initial hydrogen pressure and reaction time on catalytic hydrogenation of guaiacol were investigated. The results show that both Co-MOF and Co@C are dominated by mesoporous. After pyrolysis, lamellar structure of Co-MOF changes into irregular sphericity. As raising pyrolysis temperature, specific surface area of Co@C decreases continuously. Under the conditions of reaction temperature 180 ℃, initial hydrogen pressure 2 MPa and reaction time 2 h, the guaiacol was completely transformed and selectivity of cyclohexanol was 92.8% using Co@C-600 as catalyst. The main reaction pathway of guaiacol hydrogenation catalyzed by Co@C is that guaiacol firstly forms phenol through removal of methoxyl group, and further is hydrogenated to cyclohexanol. In addition, Co@C-600 also has good catalytic activity for other phenolic monomers derived from lignin, such as phenol, p-methoxyphenol and 4-methyl guaiacol.
Abstract: Sulfated zirconia (SZ) and two promoted 1%Mn/SZ catalysts which have been prepared via sol gel (Mn/SZ-S) and impregnation (Mn/SZ-I) methods were studied. The morphology of the catalysts was characterized by XRD, BET, NH3-TPD, ICP, SEM and FT-IR analysis. The conversion of methanol to dimethyl ether and hydrocarbons was carried out in the temperature range of 120−300 °C. The Mn/SZ-S showed the highest activity due to the high surface area with suitable acidity. The optimum condition of Mn/SZ-S catalyst was investigated at 200 °C and LHSV of 0.02 h−1 in a time range from 30 to 210 min. It was found that the total conversion decreased from 80.18% to 53.26% at 210 min. The reusability of this catalyst was studied at the optimum condition up till four cycles for 1 h. The characterization of the reused catalyst showed a significant change in the structure and surface acidity due to the blockage of the surface acid sited by carbonaceous materials.
Abstract: A series of Ti(SO4)2/activated carbon spheres (CS) bifunctional catalysts were designed and prepared by impregnation method, and the effect of calcination temperature of the catalysts on direct oxidation of dimethyl ether (DME) to polyoxymethylene dimethyl ethers (DMMx) was investigated. The results showed that the performance of Ti(SO4)2/CS catalysts was closely related to the calcination temperature. The 30% Ti(SO4)2/CS catalyst calcined under O2 atmosphere at 280 ℃ exhibited excellent activity over which the conversion of DME reached 11.7% with the selectivity of DMM1−3 up to 75.8%, wherein, the selectivity of DMM2−3 was over 30%. The texture and surface properties of the catalysts were characterized by SEM, XRD, Raman, TG, NH3-TPD and XPS. The suitable amount of weak acid sites and redox sites of the Ti(SO4)2/CS were beneficial to the direct oxidation of DME to DMMx. The calcination temperature changed the distribution of functional groups on the surface of CS which then affected the dispersion form of Ti(SO4)2. The type and amount of acid centers especially the ratio of weak acid and medium strong acid could also be adjusted, which can lead to different gradients of the surface acidity of the catalyst. The reasonable matching of the acidic and redox sites on the catalyst can evidently promote the growth of C−O chain.
Abstract: A series of K-CuZrO2 catalysts with different Cu contents were prepared. The catalytic performance and reaction mechanism of 2-pentanone from ethanol condensation were investigated. The structure and properties of the catalysts were studied by N2 sorption, XRD, H2-TPR, CO2-TPD, TEM and XPS. The results showed that when the content of Cu was 9%, the conversion of ethanol reached the maximum (99.5%) due to the strong interaction between CuO and ZrO2 which promoted the reduction of CuO and resulted in the largest specific surface area of Cu on the catalyst surface. The selectivity of 2-pentanone reached the maximum (35.0%) because the strongest basicity related to medium-strength basic sites of the catalyst surface were suitable for the condensation reaction. The formation of 2-pentanone on K-CuZrO2 catalyst was speculated on the basis of the analysis of intermediates: ethanol was dehydrogenated to form acetaldehyde. Then, the acetaldehyde was condensed and decomposed to acetone followed by reaction with acetaldehyde to form 2-pentanone.
Abstract: The CuZnAl catalyst prepared by co-precipitation was further modified with different contents of Ce through impregnation and used in the dehydrogenation of sec-butanol (SBA) to methyl ethyl ketone (MEK); the effect of Ce modification on the performance of CuZnAl catalyst was investigated. The results illustrate that the introduction of Ce in CuZnAl can promote the formation of CuAl2O4 spinel and thus improve the stability of Ce-modified CuZnAl catalyst; meanwhile, Ce is also conducive to reducing the grain size, enhancing the dispersion of CuO and ZnO, lowering the reduction temperature, and increasing the content of Cu2+ and consequently the content of active Cu0 species upon reduction. Over the Ce-modified 8%-Ce-CuZnAl catalyst, the conversion of SBA reaches 91.4% under 240 °C and a mass space velocity of 5 h−1, with a selectivity of 96% to MEK; during the 100 h reaction test, the SBA conversion keeps at about 92%, with the selectivity to MEK at about 96%, demonstrating excellent stability of the Ce-modified CuZnAl catalyst.
Abstract: The Ni/SiO2 catalysts were prepared by ammonia evaporation method, with nickel nitrate as Ni source and silica sol as the SiO2 source, for synthesis of 2-MTHF from 2-MF hydrogenation. The catalytic performance of catalysts prepared at different calcination temperatures were tested on a fixed-bed reactor. XRD, N2 adsorption-desorption, H2-TPR, NH3-TPD, XPS and TG were employed to characterize the structure and surface properties of these catalysts. The effect of calcination temperature on the structure, surface property and catalytic performance of catalysts were investigated. The result indicated that all the catalysts had a phyllosilicate structure after calcination, and maintained the structure after reduction. Ni particles dispersed well with smaller size and strong metal support interaction showed high activity. The surface acidity of catalysts was influenced by the calcination temperature. The maximum catalytic activity and selectivity were obtained on the catalyst calcined by at 500 ℃, which exhibited a 2-MF conversion of 100% and the 2-MTHF selectivity of 93.5% at the optimized condition, due to smaller particle size and suitable surface acidity.
Abstract: The cracking reaction mechanism of C5 hydrocarbons(n-pentane, 1-pentene) was analyzed. It is found that according to the ideal carbanion reaction mechanism and free radicals reaction mechanism, the molar selectivity of the cracking of n-pentane and 1-pentene to lower olefins (C2H4+C3H6+C4H8) is 50% and 100%, respectively. However, using MFI-30 zeolite, the molar selectivity of catalytic cracking of n-pentane and 1-pentene to light olefins at 650 ℃ is 23.41% and 56.79%, respectively, suggesting that 26.59% and 43.21% of light olefins have undergone hydrogen transfer reactions. The effects of different zeolites and key reaction temperature on the hydrogen transfer reaction during the catalytic pyrolysis of C5 hydrocarbons were further investigated. The results show that the zeolite with small pore structure and low acid density and higher reaction temperature can inhibit the hydrogen transfer reaction to varying degrees, thereby increasing the selectivity of light olefins. At 650 ℃, as the zeolite changes from the FAU with a large pore structure and high acid content to the MFI-120 with a small pore structure and low acid content, the hydrogen transfer coefficient HTC of the catalytic pyrolysis of n-pentane and 1-pentene is reduced by 96.86% and 50.58%, respectively, and the coke selectivity is reduced from 11.91% and 20.77% to 0.75% and 0.89%, respectively. However, the selectivity of the lower olefins increases from 14.25% and 25.14% to 46.28% and 62.58%, respectively.
Abstract: The effect of lead on the catalytic performance of Mn-Ce/TiO2 catalysts in the selective catalytic reduction (SCR) of NOx with ammonia at low temperature was investigated; with the help of nitrogen sorption, XRD, FT-IR spectroscopy, H2-TPR and NH3-TPD characterization, the causes of lead poisoning and acid regeneration were clarified. The results indicate that the doping of Pb in Mn-Ce/TiO2 leads to a significant decrease of the low-temperature SCR activity; with a Pb loading of 11%, the conversion of NO over Mn-Ce/TiO2 at 180 °C decreases from original 100% on the fresh catalyst to 44% on the Pd-poisoned catalyst. The presence of Pb may reduce the content of active Mn4+ and Ce3+ species on the Mn-Ce/TiO2 catalyst, which suppresses the redox cycle of Mn4+ + Ce3+ ↔ Mn3+ + Ce4+; moreover, the decrease of surface acidity on the Mn-Ce/TiO2 catalyst by the doping of Pb is also disadvantageous to the adsorption and activation of NH3. The Pd-poisoned Mn-Ce/TiO2 can be regenerated by nitric acid treatment; after the regeneration, the catalytic activity of Mn-Ce/TiO2 in NH3-SCR of NO is almost completely recovered and even exceeds that of the fresh catalyst at 80–150 °C. The nitric acid treatment can restore the redox capacity of Mn-Ce/TiO2, increase the surface area, and create new acid sites, which contribute to recovery of the activity of Pb-poisoned Mn-Ce/TiO2 catalyst in NH3-SCR.
Abstract: The synthesis of high quality diethyl oxalate (DEO) via transesterification of dimethyl oxalate (DMO) and ethanol (EtOH) was reported. The thermodynamic data of each substance involved in the reaction were estimated by Benson and Joback's group contribution method and Watson formula, and the enthalpy change, entropy change, Gibbs free energy and equilibrium constant of each step of DEO synthesis were calculated by classical thermodynamic formula under atmospheric pressure and in the temperature range of 323−368 K. The DMO conversion, product composition and reaction equilibrium constant at different temperatures and raw material ratios were measured by experiments and compared with the theoretical data. It is found that the error between the measured DMO conversion and the estimated value is less than 1%, and the measured equilibrium constant is basically consistent with the estimated value. After strict experimental verification, it is proved that the thermodynamic data estimated by thermodynamic analysis are reliable. The actual catalytic distillation conditions were simulated, and the composition of the initial raw materials and the final products at 353 K was calculated with the hypothesis of 99.9% DEO purity at the bottom. When the content of EtOH in the bottom was higher than 2.59% and the molar ratio of initial EtOH to DMO was higher than 2.10, the purity of DEO could reach the target, and the overall process energy consumption was significantly reduced. It would be an efficient and green route for DEO synthesis.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
