Abstract: Solid heat carrier coal pyrolysis can be conducted at mild conditions to produce coal gas and light tar by using the combination of coal pyrolysis and char combustion with air. It has a good prospect of industrial application. In this work, an intermittent experimental apparatus with the capacity of 1 kg coal was set up for solid heat carrier pyrolysis of Huainan bituminous coal. Quartz sand was used as the solid heat carrier in the tests. The effects of initial temperature of solid heat carrier, pyrolysis time, mass ratio of solid heat carrier to coal and coal particle size on the yields of gas and tar were studied. The analysis result of gas product shows that the heating value of coal gas is about 38 MJ/m3. Low temperature tar and char with a good ability for combustion are generated in the process. Under the conditions of initial temperature of solid heat carrier of 700 ℃~900 ℃, pyrolysis time of 4 min～16 min, and mass ratio of solid heat carrier to coal of 5～9, the yields of gas and tar increase with initial temperature of solid heat carrier, and the yield of gas increases with pyrolysis time and mass ratio of solid heat carrier to coal. The initial temperature of solid heat carrier has great influence on the gas composition. Char agglomeration on the reactor inner wall can be reduced by raising the mass ratio of solid heat carrier to coal. For the purpose of producing tar, the suitable operating parameters should be the temperature ranging from 750 ℃ to 900 ℃ and the residence time of 4 min.
Abstract: The ferruginous sphere is one of the main microscopy particle components in coal fired fly ash. The microstructure and mineral characteristics of the ferruginous spheres in fly ashes from 3 coal fired power plants were studied. The ferruginous spheres in fly ash samples were investigated using scanning electronic microscopy, ICP-AES and Mössbauer spectroscopy, etc. The results are expected to reveal the physicochemical characteristics of the ferruginous sphere and provide the scientific basis for prevention of slag on the boiler heating surface and resource utilization of coal fly ash. Three types of micro-particles, namely cenospheres, plerospheres and solid spheres were identified. Hematite and magnetite occur on the surface of these spheres in the form of dendritic or octahedral euhedral crystals. The element compositions of ferruginous spheres collected from Xiao Longtan power plant include mainly Fe, Si, Al and Ca, etc.; however, those from Jiaozuo and Yaomeng power plants include mainly Fe, Si and Al, etc.. The reason was analyzed in this article. The type of mineral-phase of ferruginous spheres are divided into Fe3O4, α-Fe2O3, γ-Fe2O3 and Fe3+-silicate, and their contents are quite different among three ash samples, reflecting the difference in combustion temperature of the feed coals in boilers. With increase of the temperature, Fe3O4 is generally oxidized to γ-Fe2O3 or the co-melted solid including γ-Fe2O3 and Fe3O4 firstly, then turned to α-Fe2O3; but when exceeding 1 400 ℃, Fe2O3 turns to Fe3O4 again.
Abstract: An integrated additive that has catalysis and sulfur retention functions was investigated by thermogravimetry analysis. In the TG experiments of catalytic sulfation reaction, 4.1‰ of SO2 was introduced into the system at the appointed temperature. Results show that in the presence of Fe2O3, the sulfation efficiency of CaO is 12%～58% higher than that of pure CaO at the temperature range of 650 ℃~1 000 ℃. TG curves can be divided into two ranges according to the slope, which indicates there are two different mechanisms for the sulfation reaction of CaO. In the TG study of catalytic coal combustion reaction in the airflow, results show that the mass-loss rate of coal sample doped with integrated additive increases in the main combustion interval. The ignition temperature t1 and burnout temperature t2 shift to low temperature region. The shape of DTG curve of sample doped with additive becomes sharp. Furthermore, the kinetic parameters of coal combustion reaction and CaO sulfation reaction with and without additives were calculated according to the nonisothermal combustion model and grain model respectively. Results show that catalytic promoter Fe2O3 in additive exhibits high catalytic performances both for sulfur retention of CaO and coal combustion. The promotion of coal combustion rate attributes to the increasing of active site of carbon surface by ion exchange between carbon and adding metal, thus the adsorption rate of oxygen is accelerated while the active energy and pro-exponent coefficient are decreased. The catalytic promoter Fe2O3 in the additive catalyzes the reaction of SO2 to SO3 in the chemical reaction control region and accelerates the sulfation reaction rate of CaO in the diffusion control region. Fe2O3 alleviates the aggregation of CaSO4 and weakens the pore closure in the CaO sulfation reaction.
Abstract: It has been clarified that SO2 emission during coal combustion is the main source of acid rain， and the level of SO2 in flue gas determines the erodibility of equipments. Sulfur emission form coal during combustion is determined by fuel properties and combustion conditions. The reaction mechanism of fuel sulfur conversion to oxide and the influence of different factors are still remained unclear. In this paper， combustion of six coals with carbon contents of 77％～93% (daf) and the corresponding demineralized samples has been studied in a thermogravimetric analyzer with heating rate of 20 ℃/min to examine the effect of coal rank， demineralization and inherent mineral species on SO2 emissions. For Fushun coal demineralized by HCl， Si is the main remaining mineral species with content of 3.4% (db)， so the effect of Si on devolatilization can be examined. AlCl3， Fe(C5H5)， Ca(OH)2， KOH， MgCl2， NaOH and TiO2 were used as the catalyst precursors. The results show that the concentration of SO2 in flue gas is associated with the sulfur content in coal， whereas there is no clear relation between them. That demineralization increases the SO2 emission， which indicates that inherent mineral species play a major role during combustion. Si， Al， Mg， Na， K， Ca， Fe and Ti， which are the main species in the ash of Fushun coal， are added into the demineralized coal sample by suitable method with different catalysts precursors. In the minerals， some species decrease the SO2 emission with the sequence of MgNa≈K>Ca>Mg>Ti. Si and Al are found to be inert during coal combustion. The mechanism of influence of different catalysts on the combustion is also discussed.
Abstract: Sulfur compounds in coal gas must be removed before gas processing or burning to meet the chemical synthesis and environmental law. The developments of desulfurization sorbent and technologies at high temperature have been attracting world wide attention because of its importance to the advanced coal based power generation (e.g. IGCC). The existing problems for coal gas desulfurization technology at high temperature are the loss of effective component and the powdering of desulfurizer which considerably hinder the industrial application. Zinc titanate desulfurizer is regarded as a promising sorbent for its good chemical and mechanical performance. The effect of the concentration of H2S and desulfurization temperature on the desulfurization beheavior of zinc titanate (Zn2TiO4)sorbent and the kinetic model validation were investigated in a fixed bed reactor under atmospheric pressure. The results show that the sorbent has a very good desulfurization performance. The desulfuization rate of the sorbent increases with raising the sulfidation temperature in the range of 400 ℃ ～600 ℃ and the H2S concentration of inlet gas in the range of 3 g/m3～10 g/m3. Model tests show that the desulfurization process can be fitted by the equivalent grain model with the diffusion controlling in the product layer. The calculated values of diffusion activation energy and corresponding frequency factor are 61.4 kJ/mol and 4.4×105 m2/min, respectively. It suggests that the desulfurization process is controlled by solid grain diffusion instead of pore diffusion. It is found that specific surface area and pore volume of the sulfided sample decrease considerably and there are many congregating grains formed on the surface of sulfided sorbent by means of N2 adsorption analysis and SEM photos of surface morphology, which further validates that the desulfurization of Zn2TiO4 sorbent is controlled by the solid grain diffusion.
Abstract: The solubility parameters are important in removal of pitch by solvent and the deposition of coke during transportation of asphaltene and petroleum processing technology. The thermo-cracking of Karamay vacuum residue （VR） was carried out to find the optimum condition at which the VR was thermally cracked deeply without the coke formation. The VR and the cracked residue after distillation at 500 ℃ (Re VR) were separated by supercritical fluid extraction and fractionation (SFEF) technique. The narrow fractions and non-extractable end-cuts were obtained accordingly. Each residue and their narrow fractions were characterized by average molecular weight, carbon residue, elemental contents (CHNS), metal contents and SARA composition (saturate, aromatic, resin and asphaltene). The solubility parameters of two end-cuts were determined by measuring the solubility in a series of toluene-pentane solvent mixtures, and then the solubility parameters of the fractions were calculated according to the properties. Compared with VR, the SFEF fractions and end-cut of Re VR have more unfavorable properties such as lower H/C ratio, more content of nitrogen and metals. Although the end-cut occupies only 10.4% of Re VR, it enriches most part of the impurity. The solubility parameters of the end-cuts from VR and Re VR are 18.27 MPa1/2 and 19.79 MPa1/2. The coke deposition in the processing of vacuum residue was studied in view of solubility parameter. The difference of solubility parameter between end-cut and the extractable fraction is the key to affect the stability of vacuum residue. When the difference amounts to 6.37 MPa1/2, coke will deposit under the conditions of thermo-cracking of Karamay vacuum residue.
Abstract: To suppress the coke formation during utilization of hydrocarbon fuel is the key factor in practice. A set of chromatographic reactor system was set up for determining the coke deposition produced in the cracking process of endothermic hydrocarbon fuel. The chromatographic system was useful for study on coking mechanism through online analysis of products distribution. The system is suitable for studying coking inhibition over a wide range of conditions. Endothermic hydrocarbon fuel S-1 was selected as cracking feedstock. The effect of coking inhibitors carbon bisulfide and thiophene on the cracking of S-1 were studied, including coking rate, products distribution, weight loss of metal carrier, functions and properties of the coke. The functions and properties of coke formed on the metal carrier were characterized through SEM photographs. The results show that the coking rate of endothermic hydrocarbon fuel could be effectually restrained by sulfur-inhibitors. It is also found that carbon bisulfide is the better one that could decrease 90% of initial coking rate, while thiophene could decrease 40%. The distribution of paraffin and alkene in gas products was investigated on chromatographic system, and the alkene product distributions in cracking reactions is increased by carbon bisulfide and thiophene, which is beneficial for the improvement of endothermic property of fuel. Sulfur-inhibitor improves the configuration and hydrogen-carbon ratio of coke, which is in favor of coke-cleanup. Sulfur-inhibitor could also decrease the weight loss of metal carrier.
Abstract: The catalyst precursors for slurry-bed hydroprocessing of residue need to be sulfurized for higher catalytic activity. In this study, two of the most important precursors described above, ammonium molybdate and nickel nitrate, are sulfurized. Sodium sulfide is employed as the sulfrization reagent and ammonium chloride is employed as the auxiliary sulfurization reagent. The sulfruization is carried out in three stages: Stage 1. Precursors are sulfurized directly in water-solution; Stage 2. Precursors are sulfurized in water-oil emulsification; Stage 3. The sulfurized catalysts, which have been dispersed in the media, are heated in the presence of hydrogen. XRD is employed to recognize the crystalline components in the sulfurization products, and the crystal-grain size is calculated using Scherrer's equation. TEM is employed to observe the form and size of the particles of the products. It is observed that nickel nitrate is transferred into micro-crystallized NiS2 firstly, and crystallized to NiS and Ni7S6 after heated under hydrogen, with little change in particle sizes and crystal-grain sizes; while molybdate is transferred into crystallized thioxomolybdate before the heating, and micro-crystallized MoS2 finally, with great increase in their particle sizes and great decrease in their crystal-grain sizes, thus it can be concluded that the heating under hydrogen is an important stage in the sulfurization of both precursors. According to the result of XRD, the addition use of ammonium chloride in sulfurization does not affect the chemical composition, the particle size or the crystalline-grain size of the sulfurized product of nickel salt. But the molybdate cannot be sulfurized at all without the existence of NH4Cl. When the amount of NH4Cl added rises up, it is shown by XRD that its chemical composition does not vary much, but the crystalline size is slightly decreased, and the particle of the product turns to be larger and looser. The viscosity and density of the dispersion media affect the particle size and the crystalline-grain size of the sulfurization products remarkably. When the Kelamayi vacuum residue, which has a higher viscosity and density, is used as the dispersion media, the crystalline-grain size is smaller than that of the lubricant used as the dispersion media and the shape of the particles turns from compact to loose.
Abstract: The catalyst with molybdate as the precursor for the slurry-bed hydroprocessing of residue needs to be sulfurized for higher catalytic activity. In this study, ammonium molybdate is dispersed in lubricant oil and sulfurized under different conditions. XPS is employed to analyze the surface composition of the sulfurized products. Sodium sulfide is employed as sulfurization reagent and ammonium chloride is employed as auxiliary sulfurization reagent. The sulfurization conditions examined in this study included the amount of NH4Cl added and whether the sulfurization product is heated under hydrogen or not. Chemical probe method is employed to measure the hydrogenation activity of the sulfurized catalysts. Anthracene is employed as the probe to undergo the hydrogenation with the existence of sulfurized catalysts, and the anthracene conversion is used to show the hydrogenation activity of the catalyst used. According to the XPS spectra obtained, the molar ratio of molybdenum of different valences and the molar ratio of sulfur to molybdenum is considered respectively. It is discovered that under different sulfurization conditions, the molar proportion of MoIV and the molar ratio of sulfur to molybdenum do not form a direct ratio, thus it is concluded that the sulfides of molybdenum in the sulfurization products are not only composed by MoS2, so that a new definition of sulfurization ratio is suggested. When the sulfurization product is not heated under hydrogen, the molar fraction of MoIV and the sulfurization ratio is much lower than that of being heated. It is also observed that the ratio of MoIV and the sulfurization ration increase with the increase of the amount of the NH4Cl, which results from the special sulfurization mechanism of the molybdate. The catalytic activity measured using the method of chemical probe shows that the catalytic activity is promoted along with the molar ratio of ammonium chloride added, which is in accord with the results obtained by XPS.
Abstract: In order to reduce the sulfur content of the liquid transportation fuels from petroleum residua to low levels, it is very necessary to investigate the distribution of sulfur-containing compounds for the processes and desulfurization of residua. In the past, a number of methods have been reported for the isolation of sulfur compounds from petroleum based on distillation and/or mercuric chloride adduct formation. Most of these procedures are tedious and/or applicable only to the isolation of individual sulfur-containing compounds from petroleum and other fossil fuels. In this paper the crude oil from Russia was distillated to get the distillates and the atmospheric residua (AR) was further distillated under vacuum to get VGO fractions and vacuum residua (VR). The AR and VR were deeply cut into a number of fractions by supercritical fluid extraction and fraction (SFEF) respectively. A simple method used to determine the quantity and distribution of sulfur compounds in petroleum fractions was based on the ability to selectively oxidize the sulfur atom and large difference in polarity between the oxidized and non-oxidized forms. IR and element analysis were applied in the quantitative determination of sulfur species and their distributions. It is shown that the isolation of sulfide and thiophenic compounds from petroleum residua are obtained in a high yield and the sulfur is found in light, medium and heavy fraction of residua. The quantity of sulfides varies from 0.29% to 0.72% in fractions of VR and from 0.29% to 0.96% in those of AR; and the thiophenic compounds are from 1.19% to 1.50% in fractions of VR and from 0.67% to 1.43% in those of AR. The dominated sulfur type is thiophene in which the sulfur content is over 70% of total sulfur and the minority is sulfide. When fraction becomes heavier, the absolute sulfur contents in both forms will increase. However, the relative content of thiophenic sulfur decreases while that of sulfide increases.
Abstract: A catalyst for hydroisomerization with high isomerization selectivity and excellent stability has been obtained. For the advanced use of the catalyst in industry, the effects of reaction parameters such as temperature, pressure, space velocity and hydrogen to hydrocarbon H2/CH (mol ratio) on the catalytic performance of 0.4% Pt/SAPO-11 hydroisomerization catalyst have been investigated in a 10 mL fixed-bed down-flow reactor using n-heptane as a probe molecule. The catalytic behavior and the optimum reaction parameters have been thus obtained. The evaluation results manifest that the main reaction of n-heptane over Pt/SAPO-11 is isomerization, and the selectivity to i-C7 maintains above 90% even at the conversion up to 70%. The optimum reaction conditions are: temperature 360 ℃～380 ℃, pressure 0.5 MPa～1.0 MPa, WHSV 2.1 h-1～4.1 h-1, and H2/CH (mol ratio) 2～6. Moreover, the conclusion can be drawn from the obtained data that the reaction parameters interact with each other, indicating that variation of one parameter needs the adjusting others in order to gain an optimal performance.
Abstract: As a primary energy source, bagasse has huge potential to steam or power generation in sugarcane industry. Due to its high moisture content, bagasse can cause problem of instable combustion in traditional boiler. Some new techniques have been developed to improve thermal conversion efficiency, such as gasification or co-firing with coal. The mechanism of bagasse degradation is very complex and has not been fully elucidated. This work is to describe the thermal decompose behavior of bagasse in different thermochemical processes. Non-isothermal kinetics has been proposed as an alternative to the classical determination of activation energy parameters. The dynamic thermal analysis was carried out in a Netzsch STA409 thermobalance. The pyrolysis and combustion characteristics of bagasse were obtained at different heating rates. With the Friedman method, some latent reaction mechanisms can be derived from the data analysis of non-isothermal experiments. A mechanism based on three independent parallel reactions have been used to model the pyrolysis process of hemicellulose, cellulose and lignin, with activation energy of 203.92 kJ·mol-1,238.50 kJ·mol-1 and 77.11 kJ·mol-1 respectively. Combustion process can be divided into two distinct stages, with first stage coinciding with pyrolysis process and the second one concerning a consecutive reaction of lignin pyrolysis and char combustion with activation energy of 255.57 kJ·mol-1 and 159.11 kJ·mol-1, respectively. The fitting curve of TG obtained from nonlinear regression method is coincident with experiment curves. Based on this study, it is suggested that the three major components of bagasse appear to be pyrolyzed independently with little interactions. Comparing their thermal stability, lignin is found to be most stable, the next is cellulose, while hemicellulose appears to be least stable. The results can also provide useful data for the design of a thermochemical conversion processes for bagasse utilization.
Abstract: A series of ZrO2-Al2O3 mixed oxides with different ZrO2 contents were prepared using ZrOCl2·6H2O and AlCl3 as the raw material by means of co-precipitation method. The Co/ZrO2-Al2O3 catalysts with 12% cobalt loading were prepared using the incipient wetness impregnation method. XRD, NH3-TPD, TPR and in situ IR characterization results show that surface areas of the mixed oxides support are first increased and then decrease with the increase of the ZrO2 content in the mixed oxides. The average pore size of the mixed oxides is smaller than that of the single ZrO2 or Al2O3 oxides. When the mixed oxides were used as the support of the cobalt-based catalyst, the mixture of zirconia and alumina can result in the increase of the surface area and support acidity. Meanwhile, a new crystal phase could also be formed due to the interaction between alumina and zirconia. When the ZrO2-Al2O3 mixed oxides were used as the supports of the cobalt-based catalysts, the dispersion of metallic cobalt and the amount of adsorbed CO species on the surface of the catalysts are reduced and the reduction behaviors of cobalt oxides are changed. In the test of the F-T reaction, CO hydrogenation demonstrated that cobalt supported on ZrO2-Al2O3 mixed oxides have lower catalytic activity and C5+ selectivity compared with the cobalt supported on the single alumina or zirconia catalysts.
Abstract: Direct DME synthesis catalyst contains methanol synthesis catalyst and solid acid catalyst for methanol dehydration. The general solid acid catalyst is γ-Al2O3, zeolite, or SiO2-Al2O3. And the optimal reaction temperature of HZSM-5 zeolite matches the methanol synthesis catalyst best. The key effect on the direct DME synthesis is due to the acidity of the HZSM-5. However the acidity of the HZSM-5 is up to the Si/Al ratio on the bone of the zoelite. In this paper, several kinds of HZSM-5 with different Si/Al ratios are used to investigate their effects on the direct DME synthesis. The acidity of the zeolite is tested by NH3-TPD. The HZSM-5 zeolites with different Si/Al ratios are mechanically mixed with the methanol synthesis catalyst respectively. The bi-functional catalyst is tested on the micro-reactor with an online tail gas analysis system. The feed gas composition is H2∶CO∶N2∶CO2∶CH4＝60∶30∶3∶4∶3. The reaction conditions are 493 K～553 K, 2 MPa～4 MPa, and 1 000 h-1～4 000 h-1. With the decrease of the Si/Al ratio, the acidity of the HZSM-5 increases and the CO single pass conversion increases. The selectivity order of CO to DME with different Si/Al ratio is sDME (cat38)> sDME (cat50)>sDME (cat25). The highest space time yield (STY) is 0.38 gDME/gcat·h－１ at the reaction condition of 553 K, 3 MPa and 4 000 h-1 on the catalyst with Si/Al ratio 25, which is the best Si/Al ratio among the the reaction condition range. From the NH3-TPD spectrum, the smaller the Si/Al value is, the stronger the acidity on the strong acid site (Brönsted acid) is. The dehydration process happens on the B acid site of the zeolite. With small Si/Al ratio, the results of methanol dehydration on the zeolite will be better. It can enhance the CO hydrogenation. So the CO single pass conversion increase with the decrease of the Si/Al ratio. If the Si/Al ratio is too small, the acidity on the B acid site will become too strong and the DME formed on the zeolite will be dehydrated further to form hydrocarbons such as C2H2 and C2H4. According to our study, the Si/Al ratio is 38 and 25, the selectivity to DME and the STY of DME can reach their best value respectively.
Abstract: The slurry reactor with inert liquid can transfer heat in time and avoid the catalysts sintering, CO rich synthesis gas can be used in this reactor. In order to maintain both effective heat transfer and higher CO conversion, a slurry reactor in tandem with a fixed-bed reactor was used for DME synthesis. The synthesis gas was pre-mixed in a pressurized gas cylinder. The high pressure syngas was regulated and its flow rate was controlled by a mass flowmeter and fed to the reactor. The reaction pressure was kept by a back pressure regulator. The reactor effluent was analyzed on-line by two gas chromatographs. The experiments were carried out in the range of 220 ℃～260 ℃, 3.0 MPa～7.0 MPa and 500 mL·g-1·h-1～2 000 mL·g-1·h-1. The catalyst was a physical mixture of commercial methanol synthesis catalyst and methanol dehydration catalyst, the granularity was 0.15 mm～0.18 mm. The experimental results showed that the conversion of CO increased with increasing reaction temperature and pressure, the selectivity of DME was insensitive to temperature and pressure. 7.0 MPa and 260 ℃ were the optimal reaction conditions, at which 84.5% of CO conversion and 78.7% of DME selectivity were obtained while the the weight ratio of the catalysts loaded in the two reactors was 1∶1. Then DME synthesis reactions carried out in a fixed-bed reactor, a slurry reactor and the slurry-fixed-bed equipment respectively were compared and the adiabatic temperature rise of syngas was calculated. The results demonstrated that higher CO conversion was obtained in the slurry-fixed-bed equipment and the high temperature of hotspot was avoided simultaneously. Moreover, the catalyst was stable in the reactor during the 370 h reaction.
Abstract: In order to systemically investigate the effects of Cu/Zn ratio on physical-chemical properties and catalytic performance of catalyst, a series of CuO-ZnO-Al2O3/HZSM-5 composite catalysts with different Cu/Zn ratios (Cu/Zn=1/2；4/5；5/4 and 2/1, weight ratio of oxides) were prepared. And their catalytic performance for hydrogenation of CO2 was evaluated in a laboratory fixed-bed reactor system. The physical-chemical properties of these catalyst samples were also studied by means of H2-TPR, XRD, BET, IR and XPS. The results showed that Cu/Zn ratio in catalyst could affect the catalytic activity, the crystal phase structure and the reduction property of the catalyst to a certain extent. Among the concerned catalysts with different Cu/Zn ratios, the catalyst with Cu/Zn=1/2 showed better catalytic performance for dimethyl ether and methanol synthesis. The TPR profiles of different catalysts showed some difference. With the increase of Cu content, the areas of the reduction peaks increased and the reductive peak temperature decreased slightly. The XRD results indicated that the degree of copper dispersion was decreased with the increase of Cu content in the catalysts. There was no evident difference between the catalysts in BET specific surface areas, and there was also no obvious relation between BET specific surface area and catalytic performance. The IR results of the catalysts presented that there was a corresponding relation between the catalytic activity and the intensity of absorption peak at 1 101 cm-1, which indicated the interaction between the metal oxides and HZSM-5. The XPS characterization proved that the active sites could be in two forms, i.e., Cu+ and Cu0, which supported the viewpoint that the Cu+ and Cu0 both were active species during methanol synthesis.
Abstract: Oxidative steam reforming of methanol is an attractive technology for on-board production of hydrogen for fuel cell vehicles. In this work copper-zinc-aluminum- zirconium oxide catalysts (CuZnAlZr) were prepared by two different techniques, i.e. a simple wet-mixed method and the traditional co-precipitation method. The oxidative steam reforming of methanol reaction was performed over these catalysts in the range of temperature 225 ℃ to 275 ℃ at atmospheric pressure, using H2O/CH3OH molar ratio=3 and O2/CH3OH molar ratio=0.2. It was found that the wet-mixed catalyst shows almost the same activity as the co-precipitated catalyst at temperatures of 250 ℃～275 ℃, and lower activity at temperatures of 225 ℃~250 ℃. In addition, wet-mixed catalyst exhibits higher selectivity to CO2 than the co-precipitated catalyst. The physicochemical properties of the catalysts were investigated by X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermal gravimetry and differential scanning calorimetry (TG-DSC), and surface area measurement (BET), the copper surface area was determined by N2O chemisorption. The results of the characterization reveales that in the wet-mixed catalyst, which had higher BET area than the co-precipitated catalyst, Cu species tends to move to the catalyst surface and the surface spinel specie, i.e., CuAl2O4 can be formed. Therefore the dispersion of copper and the surface area of Cu0 per gram of copper in the wet-mixed catalyst are higher than those of co-precipitated catalyst. The wet-mixed catalyst exhibits stable activity over 100h of on-stream operation at 275 ℃, the methanol conversion maintains over 90%, H2 concentration in the product gas is over 60% and the selectivity to CO2 approaches 99%.
Abstract: Recently, much attention has been attracted by hydrogen preparation from bio-ethanol. Cu-based and ZnO based catalysts have been widely applied for the investigations of hydrogen preparation from methanol or ethanol. ZrO2 has shown unique behavior as a catalyst support in many reactions owing to its acid-base property and redox property. ZrO2 supported Cu catalysts are expected to be effective catalysts in the hydrogen preparation by steam reforming of ethanol. In this paper, the catalytic performance of Cu/ZrO2 catalysts in the steam reforming of ethanol was investigated. ZrO2 supports were prepared by precipitation and alcogel methods. Supported Cu catalysts were prepared by impregnation method. The physical properties of ZrO2 support and Cu/ZrO2 catalysts, such as specific surface areas, pore volume, crystal phase and so on, were characterized by BET, XRD, TEM and XRF. The reaction was carried out in a fixed-bed reactor at 300 ℃～700 ℃ and atmospheric pressure. The effluent of the reactor was analyzed with an on-line gas chromatograph (gas phase products) and an off-line gas chromatograph (condensed products). The reaction results revealed that Cu/ZrO2 possesses relatively high activity in the steam reforming of ethanol. The influences of preparation parameters, such as catalyst components, Cu loadings, supports, preparation methods and calcination temperatures of supports, on the catalytic performance were examined. The catalytic performances of Ni/ZrO2, Cu/10MgO-90ZrO2 and Cu/10CaO-90ZrO2 were compared with Cu/ZrO2. The results showed that high conversion of ethanol and high selectivity of H2 produced by ethanol steam reforming could be obtained over Cu/ZrO2 catalysts. The H2 production could be enhanced by the addition either of Ni promoter or of base oxides, such as CaO or MgO, to the Cu/ZrO2 catalyst. The optimum Cu loading was about 8% by weight and the catalytic performance of Cu/ZrO2 prepared by impregnation was much better than that prepared by co-precipitation. The ethanol conversion reached 98%~100% over 8%Cu/ZrO2 catalyst at 500 ℃~600 ℃ while the selectivity of H2 kept at about 2~2.6(mol ratio).
Abstract: The traditional route for the synthesis of zeolites is in the system of M2O-Al2O3-SiO2-H2O or M2O-organic template-Al2O3-SiO2-H2O (M2O: Na2O, K2O or Li2O), in which inorganic alkali is necessary. Recent advances in zeolite synthesis have centered on high silica zeolite systems or have employed exotic templates. However, low Si/Al ratio zeolites are particularly attractive because they can offer high acid site density for catalytic applications and greater ion-exchange capacity in addition to compositional diversity for separation processes. Blackwell reported their discovery of two new zeolite materials UZM-4 and UZM-5, synthesized at low Si/Al ratio by using the combination of two of the most common organic templates, tetramethylammonium and tetraethylammonium ions. This exploits a new approach for novel zeolites synthesis. Offretite was first described by Gonnard and has relatively large pores of 0.67 nm running in the c-direction. It has been synthesized by several methods, such as in the system containing tetramethylammonium (TMA), Na+, K+ or p-dioxane and alkaline cations as well. Offretite synthesized by using only the combination of two organic templates (TEAOH, TMABr) has not yet to be reported. In this paper, small crystalline offretite was synthesized in a TEAOH/TMABr mixed template system at a typical synthesis composition of 12TEAOH∶ TMABr∶Al2O3∶13.5SiO2∶240H2O, and at crystallization temperature of 423 K within 7 days. The samples were characterized by XRD, SEM and IR. The catalytic properties of offretite were investigated in the alkylation of benzene with propene. These results showed that the dosage of TEAOH directly affects the crystalline phase and size of the product. Compared with TMABr, TEAOH played a more important role in the crystallization. With increasing the dosage of TMABr, zeolite Beta is obtained. The catalytic properties of H-offretite are superior in benzene alkylation reaction.
Abstract: Oxidative dehydrogenation of ethylbenzene to styrene has been studied in this paper over a novel TiO2 supported iron catalyst (Fex/TiO2) at low temperature. Here, x stands for the mol percent of iron among the catalyst. The catalysts were prepared by isovolumetric impregnation method. The solution of Fe(NO3)3 with a fixed ratio to TiO2 was impregnated into the powder of TiO2, keeping standing for 24 h～48 h and then taking it to a dryer at 120 ℃ for drying. Before it could be used, it would be calcined at a programmed temperature and then ground to a defined size. The factors involved in the dehydrogenation reaction, such as the loading amount of active component, calcined temperature during catalyst preparation, reaction temperature, particle size etc. have been investigated. By means of X-ray diffraction (XRD), thermogravimetry analysis (TGA), physical adsorption and pore size distribution and scanning electrical microscopy (SEM) analytical techniques, the function of catalyst was discussed. The results showed that Fe7/TiO2 is the optimal catalyst for the selective oxidehydrogenation of ethylbenzene at 350 ℃, 14.6% ethylbenzene conversion and 99.0% styrene selectivity were obtained in each run. Lower calcined temperature is favored for the preparation of Fex/TiO2 catalyst, at which the microstructure of active components was well controlled. Higher reaction temperature would lead to the side-reactions happened and the decrease of styrene selectivity. The deactivation of Fex/TiO2 catalyst is due to the loss of Fe active components.
Abstract: The specific heat capacity is one of the thermo-physical properties of coal, which is an important parameter in utilization of coal. The microstructure of coals and their chars produced at the different pyrolysis temperature were studied by a scanning electron microscope, and the specific heat capacity was measured by DTA and DSC method. The microstructure of 4 coals with higher rank and their chars are well statistically self-similar and have been expressed by the fractal dimension. The results show that the fractal dimension is related to coal rank and pyrolysis temperature. The microstructure and the fractal dimension of coals have a good relationship with their specific heat capacities. For coals with different rank or chars produced at different pyrolysis temperature, the specific heat capacity increases with the increase of fractal dimension. The mechanism of the fractal dimension and the specific heat capacity are correlated with fractal dimension and statistical-thermodynamics theory. The more compacted and ordered the microstructure is, the less the number of pores, cracks and defect center is and the smaller the specific heat capacity is; on the contrary, the specific heat capacity changes greatly.
Abstract: In order to reducing olefin fraction in FCC gasoline, USY zeolite, the active component of FCC catalyst, was modified by impregnating or ion-exchanging chromium. Acidity and cracking activity of modified USY zeolite were studied by IR and MAT. It was found that both amount and strength of Bronsted acid site on the surface of modified USY zeolite were increased obviously, but the Lewis acid site was almost unchanged. The hydrogen-transfer activity of modified USY zeolite was independent of the ways of loading chromium, but the isomerization activity of USY zoilite was dependent of the loading methods. The impregnated Cr-USY was better than ion-exchanged Cr-USY. The activities for cracking, hydrogen-transfer and isomerization reaction of modified USY zeolite were increased first, and then decreased with increasing of chromium amount. The cracking catalyst, USY zeolite with 0.01% chromium as the active component, showed higher activities for cracking, hydrogen-transfer and isomerization reaction. The olefin content in cracking gasoline was decreased evidently, and the isomeric alkane, cycloalkane and aromatic hydrocarbon were increased. The extent of olefin decline was high to 28 %, but the contents of isomeric alkane, cycloalkane and aromatic hydrocarbon were enhanced in evidence, they were 6.8 %, 20 % and 27.6 % separately comparing to the USY zeolite cracking catalyst. The decreasing of olefin and increasing of cycloalkane and aromatic hydrocarbon improved the octane number of cracking gasoline. It was indicate that the chromium modified USY zeolite was favorable to the olefin-reduce cracking catalysts.
Abstract: The improvement of the Cold Filter Plugging Point (CFPP) by an additive will depend on either the characteristics of the diesel or the additive itself. The ways in which cold flow improver interacts with the constituents of the fuels and the reasons for their efficiencies are far from fully elucidated. In this work , the contents of the n-paraffin in five kinds of diesels were tested by urea adduction, and the carbon distribution of n-paraffins was tested by temperature programmed gas chromatograph GC-14A and computed by the software for simulating distillation. Maximum likelihood method is applied to obtain μ and σ2 of the carbon distribution, and the deviation χ２ is computed. When the degrees of freedom is 4 and significance level (α) is 0.10, χ２０.９０(4)＝7.779. If deviation χ２ is smaller than χ２０.９０（4）, the hypothesis that the population is normal is accepted. The results show that the distributions of n-paraffin in these five kinds of diesels are normal. It can be found that the susceptibility of the diesel DQCH is weak and the variance σ2 of the carbon distribution in n-paraffin is only 1 076.21 smaller than that for other diesels. The smaller the variance σ2 is, the weaker the susceptibility is. The susceptibility of the diesel LYL is also weak. The value of the statistic test quantity χ２ on the normal distribution of the n-paraffin in the diesel LYL is 4.112 bigger than other diesels . Statistic test quantity χ２ could reflect whether the carbon distribution of n-paraffin fits the normal distribution. When the carbon distribution of n-paraffin does not fit normal well, the wax settling does not match the agglomeration of flow improver. In this situation, the flow improver can't interact with more wax crystal so that the CFPP of diesel can not be decreased.
Abstract: More and more stringent environmental regulation to lower the sulfur level in diesel fuel leads to extensive studies on the deep hydrodesulfurization (HDS), which is the key to produce the high quality fuel with low sulfur content. Kinetics and novel rector technologies for HDS have attracted wide attention of both researchers and refineries. In this paper, the reaction network for hydrodesulfurization of dibenzothiophen (DBT) and 4,6-dimethyldibenzothiophen (4,6-DMDBT), in which the sulfur is removed most difficultly, is introduced over various catalysts. The effect of component and support of the catalyst on the ratio of the rate of direct desulfurization (DDS) to that of hydrogenation followed desulfurization (HYD) is analyzed . Various kinetics, such as for model reactants related to DBT with or without inhibitors like H2S, and for the real oil feed, are reviewed in detail. The application of artificial neural network to the simulation and prediction of HDS for various diesel oils is presented. New reactor systems for HDS, such as cocurrent countercurrent trickle-bed reactor, two-phase reactor, catalytic distillation HDS reactor and so on, are summarized. Further researches and challenges for the kinetics of HDS and reactors are proposed.
Abstract: The pollution of dioxins emitted from incineration of municipal solid waste has become a serious problem and is paid attention gradually. The details of the mechanism of dioxins formation, detection methods and control technology were discussed. Chromatography, immunology, biology and laser mass spectrometry are main detection methods. HRGC/HRMS, CALUX and EIA have achieved better effects in practice. But each method has its specific application limits. Chromatography can separate dioxins compounds but much labor, high technical skill, long periodicity and extreme cost are required, usually be used in the case of accurate quantitative measurement on each composition and no need to calculate the total amount. Immunology and biology methods take short time and can detect large quantity samples at the same time. They are suitable for the screening of large-scale samples and the detection of total toxic equivalent weight. Laser mass spectrometry has the characteristics such as high selectivity, high sensitivity, multi-component detection and online analysis; but the spectrum structure of the pollutants should be known in advance. The control technology of dioxins mainly concentrated on the fields of improving combustion technology, capturing and decomposing dioxins. The most valid method is improving the incineration process of municipal waste so that dioxins can be eliminated from the source.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
