Abstract: A brown coal, a high-volatile bituminous coal and a low-volatile bituminous coal were pyrolysed at a slow heating rate in a thermogravimetric analyser. The char samples were characterised with FT-Raman spectroscopy using a 1 064 nm laser. The Raman spectra of these chars between 800 cm-1 and 1 800 cm-1 were then deconvoluted with 10 Gaussian bands representing the typical structures found in highly disordered carbon materials. Both total Raman intensity (peak area) and the Raman band intensity ratios from spectral deconvolution are useful parameters for the description of the structural features of coal chars. While the chars from the brown coal, the high-volatile bituminous coal and the low-volatile bituminous coal differ significantly at low pyrolysis temperatures (e.g. 600 ℃), the differences diminish with increasing pyrolysis temperature to 800 ℃ or 900 ℃. The ion-exchangeable Na in brown coal affects the char-forming reactions taking place during pyrolysis.
Abstract: Pd/ZnO catalysts with Pd loadings between 5.2% and 21.9% for steam reforming of methanol to hydrogen have been prepared by co-precipitation. The effects of Pd loadings and the reduction temperatures on the catalytic performance have been investigated in a stainless steel reactor at 1 bar, 523 K, 17.2 h-1～57.2 h-1 (WHSV) and H2O/CH3OH(mol ratio)=1.0. The 15.9% Pd/ZnO catalyst at a reduction temperature of 523 K～573 K has the best methanol conversion. 41% of methanol conversion, 94% of selectivity for CO2 and 0.65 mol/(gcat·h) of hydrogen yield are obtained at 1 bar, 523 K and 17.2 h-1 over 15.9% Pd/ZnO reduced at 573K. The temperature programmed reduction (TPR) results show that PdO can be reduced to Pd at room temperature, and some of ZnO can be initially reduced at about 440 K. Introduction of Pd facilitates the reduction of ZnO. The X-ray diffraction (XRD) results of various Pd loading catalysts, reduced at 573 K, confirm the existence of hexagonal ZnO and tetragonal PdZn alloy. Moreover, minor cubic Pd2Zn on 21.9% Pd/ZnO is also observed. PdZn alloy may be the active site for the titled reaction, while Pd2Zn on 21.9% Pd/ZnO results in low activity. XRD results of 15.9% Pd/ZnO reduced at different temperatures show a peak ascribed to PdZn alloy appeared progressively, which becomes remarkably intense and sharp with the increasing reduction temperature. A marked PdZn alloy occurs when the reduction temperature rises up to 573 K, which suggests that PdZn alloy forms easily over Pd/ZnO catalysts prepared by co-precipitation. The crystal size of Pd-Zn alloy (111) grows up from 14.4 nm to 27 nm while the reduction temperature rises from 573 K to 773 K. XRD of 15.9% Pd/ZnO, subjected to methanol reforming at 523 K after reduction at room temperature, also shows the peak ascribed to PdZn alloy. Though the hydrogen product can reduce the catalyst, the best reduction atmosphere is under pure hydrogen conditions. The initial stability tests over 15.9% Pd/ZnO and the commercial CuO/ZnO/Al2O3 catalyst are operated at 573 K. The results show that the methanol conversion over 15.9% Pd/ZnO remains a constant value for 8 h without deactivation. On the contrary, the methanol conversion over CuO/ZnO/Al2O3 catalyst gradually decreases with time on stream.
Abstract: Several carbonates are synthesized from carbamates either with hydrochloride as coreactant or with zeolites as catalysts under low temperature and pressure, whereas high yield is achieved through either the formation of ammonium chloride as precipitate or the adsorption of ammonia in zeolites. With hydrochloride as coreactant, the yield reaches 58% at 60 ℃, while the highest yield is 19% at 140 ℃ with zeolites as catalysts. Carbonates are considered as environmentally compatible reagents, solvents and gasoline additives, and the new processes may be potential for the substitution of the phosgene routes of pollution hazards.
Abstract: Sustainable development requires cheap, secure and environmental-friendly energy supply and use. None of the current energy options, including natural gas, oil, coal, nuclear and renewables, and the current ways of their use could fully meet the needs of growing economy and sustainability requirements. Evolutionary changes in the current energy systems to improve efficiency, eliminate pollutant emissions and reduce greenhouse gas per unit energy output are the most important first step in the sustainable development. Revolutionary technology innovations in energy sources and use, through continuing R&D effort, must occur before a genuine sustainable state could be reached. In searching for the zero-emission energy technologies as required by the sustainability principles, fuel cells and hydrogen economy, powered by renewable sources, are found to provide the most appropriate combination. Coal has a critical role to play in the transition path towards such sustainability, for it is abundant, cheap, secure, and long-term available. Coal gasification, combined with fuel cells technology and future advancement in CO2 sequestration and storage, can achieve zero-emission. The coal technologies will also provide renewable energy, particularly biomass and wastes, a real opportunity to grow its contribution in the sustainable energy mix.
Abstract: The combustion residues of Xinwen coal water slurry (CWS) and black liquor coal slurry (CS) were studied. The typical combustion ashes sampled from different locations such as furnace wall, silicon carbide rod, heat flux probe et al. were analyzed in detail, including the chemical composition, mineral component, element distribution and microstructure. The results show that the content of compound and mineral phase comprising Al, Fe, Ca in the ash from combustion of CWS is higher than that of CS, while the case of Na, K, S and Cl is opposite. The enrichment of Fe in the ash is the reason of fouling and slagging during combustion of CWS, but Na and Fe are the essential mineral elements for the ash deposition of CS. Na plays more important role than Fe in the forming and developing of ash deposit in combustion of CS. The ash samples of CS are composed of many sodium rich and fusing temperature low minerals, such as nepheline, thenardite and hauyne. Hence, Na is the key element giving rise to severe fouling and slagging when black liquor coal slurry is fired in furnace, which is confirmed by microscopic analysis and practical burning test. The ash deposition trend for CS is much stronger than that for CWS, and their deposition mechanisms are different because of the existence of Na2SO4 and other S, Cl elements in the black liquor.
Abstract: To understand the relationship of the tar compositions and the coal macerals, the tars obtained from the pyroloysis and hydropyrolysis of Shenmu coal macerals in a fixed-bed reactor were analyzed using GC-MS. And the effects of petrographic component, atmosphere and pressure on the yield of aromatic hydrocarbon, phenols, hydrocarbons, oxygen-containing heterocycle and PAHs were systematically investigated. The results show that there is great difference in the composition and the relative content of long chain hydrocarbon, aromatic hydrocarbon, phenols, oxygen-containing heterocycle and PAHs in tars from vitrinite and inertinite pyrolysis. Vitrinite tar contains high content of hydrocarbon with long chain, and inertinite tar contains high content of aromatic hydrocarbon, phenols, oxygen-containing heterocycle and PAHs. It suggests that vitrinite has lower aromaticity and longer chain in its structure than inertinite, which is in well agreement with the result from 13C NMR and FT-IR test. The tar yield of hydropyrolysis is higher than that of pyrolysis. With increasing the hydrogen pressure, the yield of tar increases greatly. The content of phenols and naphthalenes in vitrinite tar from hydropyrolysis under 0.1 MPa is much lower than that from pyrolysis, while that of internite tar changes a little. The difference of tar composition and relative content during pyrolysis and hydropyrolysis reflets the effect of hydrogeneration and hydrocarcking reactions and the structure characteristics of the macerals.
Abstract: On the basis of coal geochemistry and coal petrology, the content, migration, and distribution of rare earth elements (REEs) in the Paleozoic coals and their washing products were determined using inductively coupled-plasma mass spectrometry (ICP-MS), sequential chemical extraction procedure, and optical microscope. The contents of REEs in 47 coal channel samples from 10 mines of Kailuan Coalfield were determined. The results show that the REEs are not significantly enriched in the coals from the Kailuan Coalfield, North China. The content of REEs increases in the order of cleaned coal (76.63 w/10-6), raw coal (85.84 w/10-6), middling coal (88.6 w/10-6), tailing coal (125.93 w/10-6), and coal slime (177.08 w/10-6). The values of δEu and δCe are similar among raw coal and its washing products. The obvious difference of REEs in raw coal and its products is their different concentrations. Six states of REEs, water soluble, exchangeable, organic, carbonate, silicate, and sulfide states, are classified to study modes of occurrence. Modes of coccurrence of REEs in raw coal and middling coal are similar. REEs in the cleaned coal are mainly associated with organic matrix and silicates. Most of REEs in the tailing coal and coal slime are associated with alumino-silicate mineral matters. However, Tm, Yb and Lu associated with organic matter are surprised high in all coal washing products compared with the other REEs. Tm, Yb, and Lu associated with organic matter in the coal slime are 2.4%, 3.5% and 2.8%, respectively. Combined with the results of sequential chemical extraction and mineral composition analyses, it can be concluded that the dominant influence factors on the concentration and modes of occurrence of REEs are in order of clay minerals, organic matter, pyrite, quartz and calcite.
Abstract: Additives have usually been used to improve the slurryability and rheological behavior as well as static stability of coal water slurry (CWS). The effect of polymerization degree of polyoxyethylene nonyl phenyl ether (PNPE) on the properties of CWS prepared from 8 coals was investigated. It is found that CWS with high coal content can be prepared when PNPE polymerization degree is in a optimal range from 40 to 80. The relationships between coal properties and maximum concentration of slurry and minimum flow index were analyzed by Multiple Linear Regression method. Regression results suggest that low value of moisture content and low value of small pore volume are favourable to the slurryability of CWS when PNPE additive is added, and large value of vitrinite reflectance (Rmax) facilitates the formation of CWS with the rheological behavior of pseudo plasticity. The static stability test results show that the important factors determine the CWS properties are high rank of coal, low inertinite content, and suitable PNPE additive polymerization degree as well as.
Abstract: Using methane as the carbon source to lower the coke reactivity and enhance its strength is a promising method. However, there is little literature on the thermal performance of metallurgical coke under methane. In this work, thermal performances of metallurgical coke and the gas evolution under methane were studied by TG-MS to well understand the interaction between methane and metallurgical coke. Effects of experimental conditions including temperature, holding time, partial pressure and flow rate of methane, and the quality of cokes on the weight gain of cokes were investigated. The gas evolution including CO2, H2O and H2 during the process was examined by MS. The results show that only weight loss is found when the metallurgical coke is heated under inert gas while the weight gain begains at 860 ℃ when it is heated under methane. It is found that no weight gain and methane decomposition reaction occur in the absence of metallurgical coke in the reactor. It indicates that the metallurgical coke has some catalytic effects on the decomposition of methane. The results of MS analysis show that the weight loss at the initial stage is mainly caused by the evolution of CO2 and H2O, while the weight gain of coke above 800 ℃ is due to the carbon formation on the coke by the CH4 decomposition to release H2. At the constant temperature, the rate of H2 evolution does not change greatly in the holding time. The experimental conditions and the quality of the coke also have great effects on the methane decomposition. The weight of cokes increases with increasing temperature, holding time and partial pressure of methane. Flow rates of methane in the experiment have little effect on the weight gain of cokes. The poorer the quality of metallurgical coke is, the higher the increase of the coke weight will be, which shows that the thermal processing in methane could improve the quality of metallurgical coke.
Abstract: A moisture stable ionic liquid that contains Cu(Ⅰ) was used as solvent for desulfurization from gasoline in this paper. CuC1 was mixed with 1-butyl-3-methylimidazolium (BMIM) chloride according to the molar ratio of 2∶1 to synthesize [BMIM][Cu2Cl3] ionic liquid. [BMIM][Zn2Cl5] and [Et3NH][Cu2Cl3](Et=ethyl) were prepared in the same process. Model oil (dissolving thiophene in the mixture of heptane and toluene) and commercial gasoline were treated by [BMIM][Cu2Cl3] at room temperature. It is found that [BMIM][Cu2Cl3] could remarkably remove sulfur from oil. After six-stage extraction, the S content in the model oil reduces from 650×10-6 to 20×10-6 when the mass ratio of IL/oil is 1∶3. The single stage desulfurization decreases from 37% to 23% with the IL/oil ratio decrease from 1∶2 to 1∶5. It is also shown that the desulfurization ability of [BMIM][Cu2Cl3] from real gasoline is similar to that from model oil. Other components in gasoline have little influence on the desulfurization ability of [BMIM][Cu2Cl3]. [BMIM][Cu2Cl3] can be easily separated because of the biphasic systems of IL/oil formation. The polymerization products of olefin in gasoline are not detected in desulfurization. Desulfurization abilities of [BMIM][Zn2Cl5] or [Et3NH][Cu2Cl3] are lower than that of [BMIM][Cu2Cl3]. Carbon tetrachloride and toluene were used to regenerate the ionic liquid prepared. The regeneration was conducted at mass ratio IL/solvent of 1∶3 and temperature of 75 ℃ with stirring for 30 min. The regeneration results indicate that the sulfur removal capacity of IL is recovered completely by carbon tetrachloride treatment, but toluene shows poor ability to regenerate [BMIM][Cu2Cl3]. CCl4 might be easily seperated from the high boiling point thiophene derivatives absorbed by evaporation or rectification .
Abstract: With the increasing attentions to global environment, it becomes a new subject to reduce the olefin content in catalytic cracking gasoline, and to increase the content of iso-paraffin and naphthene at the same time. As the mid-product of the FCC process, olefin will undergo various reactions, and its reaction mechanism is quite complex. A series of cracking experiments of pure olefin compounds and FCC gasoline under different reaction conditions have been carried out in the self-made instrument of subminiature reactor-chromatograph united apparatus. The reaction mechanism of pure olefin compounds and that of olefins in gasoline under different conditions were analyzed. In the reactions of pure olefin molecules, the olefins with carbon number less than six mainly isomerize, and no cracking and H-transformation reactions take place. 95% of olefins with carbon number more than seven directly crack to produce C3, C4 at high reaction temperatures. Compared with the rules of pure olefin compounds cracking, the conversion of olefins in gasoline mainly occurs among olefins with carbon number more than seven, and the content of C5, C6 olefins in upgraded gasoline is hardly reduced. Though some interactions of olefin compounds in the gasoline upgrading process are observed, the mechanism and rules of pure olefins can be used to predict the conversion of olefins in gasoline. Therefore, under FCC conditions, it is difficult to transform C5, C6 olefins, and this is also the key problem of olefin reduction. Conversions of olefins over spent catalyst and regenerated catalyst with a small quantity of coke deposition were compared. It is found that the route of the conversion of olefins in gasoline is hardly influenced by the type of coke on catalyst.
Abstract: Thermal cracking and secondary reactions occurred in FCC process were studied by using a continuous pilot riser-type FCC unit. The effects of operating parameters(reaction temperature, catalyst to oil ratio, contact time)on thermal cracking and secondary cracking were also investigated. Moreover, the influence of overcracking operation on thermal cracking, hydrogen transfer and isomerization reactions was particularly discussed. The experimental results show that low reaction temperature, short contact time of oil and catalyst, and high catalyst to oil ratio may suppress the detrimental thermal cracking dramatically, and benefit to hydrogen transfer and the isomerization reactions. In the overcracking operation caused by high temperature, the thermal cracking may be enhanced, and hydrogen transfer and the isomerization reactions may be decreased remarkably, while the condensation reaction between olefin and aromatic hydrocarbons can be enhanced. In the overcracking operation caused by high catalyst to oil ratio, the thermal cracking may be restrained while the hydrogen transfer and the isomerization reaction in the secondary reactions can be promoted obviously. In the overcracking operation caused by long contact time, the thermal cracking reaction increases and the hydrogen transfer and the isomerization reaction appear the same tendency as thermal cracking reaction.
Abstract: Coke depositions in modern fluid catalytic cracking units (FCCUs) have been found in many parts of the unit, which can form large accumulations in reactors and affect the process performance and more badly, result in a significant safety hazard. Therefore, it is necessary to understand the microstructures of coke and coking process in commercial FCCUs. Coke samples from the FCC reactors in several refineries and their microstructures were analyzed by using both scanning-electron microscope (SEM) and X-ray analysis (EDS) methods. Meanwhile, the coking process was also investigated. The cokes can be divided into four kinds, i. e. filamentous coke, guttate coke, block coke and particle cluster coke, which have different formation mechanisms. The coking process in the FCC reactors is a complicated sequence of catalytic and/or noncatalytic reactions. Some occur in the gas phase and the others on the solid surfaces. The filamentous coke is formed from gaseous hydrocarbons metal-catalyzed reaction in which metal carbides are intermediate compounds catalyzed by iron and nickel. The guttate coke is resulted from the coking of non-volatile tar droplets which are transferred to the solid surfaces. As a result of dehydrogenation and condensation reactions of multi-ring aromatics, resins and asphaltenes and the cyclization and polymerization of olefin and diolefin, the non-volatile droplets are rapidly carbonized and a graphitic coke spheroid is produced. The block coke is formed when the non-volatile droplets are dissolved together and then carbonized. The particle cluster coke is formed by the agglomeration of micro coke particles formed in the gas phase.
Abstract: The influence of preparation conditions, such as pyrolysis temperature and feed moisture content, on the combustion reactivity of chars produced from spruce wood by the flash pyrolysis has been investigated using a thermogravimetric analyser (TGA). The chars were produced in a fluidised bed reactor at 748 K, 773 K and 823 K, and with wood feed containing different moisture contents of 0, 7.0% and 11.3%. It was found that the reactivity of a char in chemical kinetic control regime increased with decreasing pyrolysis temperature, and the volatile matter (VM) content and H/C ratio in chars also increased with decreasing pyrolysis temperature. There may have a direct relationship between the reactivity of chars and the combination of VM and H/C. In addition, chars produced under lower pyrolysis temperature possess higher activation energy and are more sensitive to combustion temperature, compared with those produced under higher pyrolysis temperature. It was found that feed moisture content has only a minor influence on char reactivity but has a significant effect on the volatile material content of chars produced at higher pyrolysis temperatures. Finally, a simple power-law kinetic model that has been employed to properly describe the char combustion.
Abstract: The biomass gasification power generation (BGPG) technology would be one of the most advanced ways to use biomass as an clean energy source. A 1MW circulating fluidized bed (CFB) wood waste gasification power generation plant was built and put into operation. The main existing problems during operations are fouling, slagging and corrosion, which are related to the characteristics of ash. A sound understanding of the characteristics of ashes can promote the design of BGPG and the assessment of the environmental impact of biomass utility. Therefore, the characteristics of ashes from biomass gasification power generation plant were investigated. The concentration, distribution and enrichment of the trace elements, As, Al, Br, Ca, Cd, Cl, Cr, Cu, F, Fe, Ga, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Sr, Ti, Zn in the gasifier bottom ash, cyclone separator ash and wet scrubber ash were determined by Inductive Coupled Plasma Spectrometer (ICP-AES). X-ray fluorescence (XRF) spectrometer was used to determine the ash compositions based on the weight percent of oxide. The distribution of trace elements in different sizes of ash particles was also examined. The particle size distribution for >50 μm ash presents a double peak curve, while the particle size distribution for ≤50 μm ash presents a single peak curve. The results show that the large part of ash is residual carbon, and most of the trace elements have an enrichment tendency in the small size particles. Most of volatile matter, e.g. halogen elements and alkali elements, mainly exists in the wet scrubber ash and enriches in fly ash. Most of Fe, Si, Ni, Pb, Zn, Cr, Cd elements are found in the separator ash, indicating an enrichment of heavy metal elements in separator ash. The trace elements such as K, S, Mn, Cu are mainly found in the gasifier bottom ash.
Abstract: The adsorption behavior of SO2 and NO on Na-γ- Al2O3, a sorbent used for simultaneous removal of SOx (98.0%~99.0% SO2) and NOx (90%~99% NO) form flue gas, was investigated in an atmospheric fixed bed reactor at 150 ℃ by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The volumetric composition of feed gas was 0.51% SO2, 0.1% NO, 4.5% O2, Ar as balance. For the adsorption behavior of a single pollutant, SO2 is adsorbed easily and no SO2 is oxidized to form SO42- (at least SO42- can not be detected on the surface of sorbent), whereas NO is adsorbed more difficultly compared with SO2. The adsorption capacity of NO is low, and a small amount of NO2 or surface nitrate is formed. The adsorption capacities of SO2 and NO are improved in the presence of O2. NO and SO2 can be adsorbed simultaneously in the presence or absence of O2. There are interactions between SO2 and NO on Na-γ- Al2O3. The presence of NO favors adsorption of SO2 and formation of SO42-. Whereas effect of SO2 on adsorption of NO is complicated. SO2 can promote NO oxidation to form NO2 or surface nitrate; on the other hand, SO2 can result in desorption of NO2. The adsorption capacities as well as interactions of NO and SO2 are enhanced by O2.
Abstract: A kind of active coke (AC-A) for SO2 removal from flue gas was directly produced from a large scale fluidized bed gasifier. The desulphurization behavior and characteristics of the active coke (AC-A) were investigated under different conditions and compared with a commercial active coke (AC-B) with approximate saturated sulphur capacity. It is found tht adsorption temperature has complicate effect on the adsorption behavisor of AC-A produced. AC-A has a maximum sulfur removal ability at 100 ℃. It is not surprised to see a short adsorption period of AC-A with the increase of gas hourly space velocity (GHSV) or SO2 concentration. There are suitable values of oxygen concentration (about 6%) and steam concentration (about 10%) for AC-A to obtain high sulfur removal ability. AC-A prepared shows higher desulfurization ability than commercial AC-B at the same adsorption conditions. Meanwhile, the desulphurization ability of regenerated active coke AC-A is also better than that of regenerated AC-B after every regeneration courses. This kind of active coke can be potentially used in the flue gas desulfurization, though efforts are needed to modify it.
Abstract: Nanometer sized ZnO with average particle diameters of 15.4 nm, 19.1 nm, 22.9 nm and 33 nm were prepared by calcination at different temperatures. Their desulfurization behavior and selective oxidation of H2S at room temperature were studied, and compared with commercial ZnO. Properties of nanometer ZnO before and after reactions were characterized by XRD and XPS. XRD results show that there is not ZnS peak detected after reaction, and in the presence of oxygen sulfur and one unknown product are formed, but without oxygen two unknown products are found. In the absence of oxygen, the desulfurization abilities of ZnO decrease, and the product color changes from brown, orange to yellow with the increase of ZnO diameter. The brown and orange products are unstable in air. In the presence of oxygen, however, the desulfurization mechanism of nanometer sized ZnO is obviously different. Nanometer sized ZnO can catalyze the oxidation of H2S to sulfur at room temperature. ZnO particle size also gives great influence on this process.
Abstract: The heteropoly acid complex H6PMo9V2Nb1O40 was prepared by the method of common acidification. Kieselguhr supported heteropoly compounds PMo9V2Nb1/K was prepared by the isovolumic impregnation. Its reducibility and acidity and the chemisorption and reactivity for C2H6 oxidation were characterized by IR, H２-TPR, NH３-TPD and microreactor techniques. The results showed that the catalyst PMo9V2Nb1/K still keeps the original Keggin structure like H6PMo9V2Nb1O40, but the activity of the crystal oxygen increased obviously and the strength and amount of the Br ö nsted acidity decreased in some degree. The hydrogen in C2H6 can be adsorbed on the surface oxygen sites in Nb—O—Mo or V—O—Mo bonds of the catalyst to form a molecular adsorption state. With the temperature rising, the C—H bond in the adsorbed C2H6 on the bridge oxygen of Nb—O—Mo bond would be broken to form dissociative adsorption states, then react with the surface oxygen to form the target products. Under the optimal conditions of 240 ℃, 0.4 MPa and space velocity 2 000 h-1, the conversion of ethane reached 22.5%, with the selectivity of 90.8% to acetic acid and acetaldehyde. The support of heteropoly compounds PMo9V2Nb1 on kieselguhr improved remarkably the conversion of ethane.
Abstract: At present, the most catalysts studied for methanol synthesis are on the basis of Cu/ZnO/Al2O3 catalyst. It was believed that the particle size and surface composition of Cu in Cu/ZnO/Al2O3 catalyst are important factors to the catalytic process. In recent years, various methods, such as sol-gel method, micro-emulsions, coprecipitation with adding surfactant, two-step precipitation etc, have been developed to prepare Cu/ZnO/Al2O3 catalysts with fine particle size or (and) high relative surface composition of Cu. In this paper, a novel method by the two-step precipitation combined with addition of surfactant method was proposed to prepare a ultrafine Cu/ZnO/Al2O3 catalyst. The particle size and surface composition of Cu and catalytic activity of the catalysts were studied. Four kinds of Cu/ZnO/Al2O3 catalysts for methanol synthesis were prepared by conventional coprecipitation, two-step precipitation without addition of surfactant, coprecipitation adding surfactant and two-step precipitation combined with addition of surfactant, labeled as Cat 1, Cat 2, Cat 3 and Cat 4 separately. These catalysts were tested in a micro-reactor using a feed gas of H2/CO/CO2/N2 (vol ratio)=66/27/3/4.The reaction conditions were 483 K～543 K, 3 MPa and 7 500 h-1. The properties and structure of the catalysts were characterized by means of SEM, XRD and XPS. The space-time yield (STY) of methanol is in the order of STYCat 4>STYCat 3>STYCat 2 >STYCat 1. The optimal temperature for all four catalysts is 523 K. Under the reaction condition of 523 K, 3 MPa and 7 500 h-1, the STY of Cat 4 reaches to 0.494 g·g-1·h-1, which is 47.9%, 16.8% and 9.3%higher than that of Cat 1, Cat 2 and Cat 3 respectively, From results of SEM and XRD, it can be found that the particle size of catalysts are in the order of Cat 1>Cat 2>Cat 3>Cat 4. The XPS results show that the relative surface Cu contents are in the order of Cat 4>Cat 3>Cat 2>Cat 1. SEM, XRD and XPS results all suggest that Cat 4 has high methanol synthesis activity because of its fine particle size and high relative surface Cu content. Based on the study, two-step precipitation combined with addition of surfactant is a good method to prepare an ultrafine and high surface Cu content catalyst with high methanol synthesis activity.
Abstract: The kinetics of the hydrodesulfurization (HDS) reaction of dibenzothiophene(DBT), as the model compound for S-bearing organics in middle distillates, were studied over the commercial NiW/Al2O3 catalyst RN-10 in a high-pressure trickle-bed reactor. The effect of reaction conditions on the catalytic behavior was studied at the hydrogen pressure of 1.5 MPa～4.5 MPa, volume ratio of hydrogen/oil of 150～700, weight hourly space velocity of 15 h-1～60 h-1 and reaction temperature of 280 ℃ to 380 ℃. The hydrogen pressure and volume ratio of hydrogen/oil exert little influence on the conversion of DBT at the high hydrogen pressures and volume ratios of hydrogen/oil. At low reaction temperatures, the conversion of DBT increases drastically with the increase of reaction temperature up to 330 ℃, while it increases slowly at high reaction temperatures. A kinetic model of HDS is established according to a second-order kinetics model at various reaction temperatures. The parameters of the model are calculated. The model correlation coefficient is above 0.989. The apparent activated energy at high reaction temperature region (≥330 ℃) is less than that at low temperature region, which are 13.4 kJ/mol and 121.4 kJ/mol respectively. Therefore, the HDS performance of the RN-10 catalyst could not be improved by just increasing the reaction temperature.
Abstract: The surface component of carbon black from pyrolysis of used tires in a pilot-scale rotary kiln was analyzed by X-ray photoelectron spectroscopy (XPS), and the difference between surface and bulk of pyrolytic carbon black (PCB) depending on pyrolysis temperature and PCB particle diameter was studied. The surface component of PCB was compared with that of commercial carbon black (CCB). Some X-ray photoelectron, auger electron and satellite peaks were found in the spectra of PCB or CCB. The bulk of PCB contains more ash elements such as Zn, Si, S and Mg than CCB. The type and distribution of ash elements are independence on pyrolysis temperature. Most ash elements in tires are left in PCB after pyrolysis. A layer consisting of adsorbates and deposits is found on the surface of PCB. The adsorbates and the deposits come from the condensed carbon formed by pyrolytic gases and hydrocarbons in gas phase during pyrolysis. The concentration of ash elements in the surface layer is very low. When pyrolysis is not completed below 500 ℃, there are a little adsorbates and deposits formation. The adsorbates layer is very thin and has little influence on the properties of bulk PCB. The finest PCB powder (diameter<0.074 mm) from the abrasion of PCB surface during rotation in the rotary kiln contains few ash elements. The relative concentration of Zn decreases with the decrease of PCB particle diameter. The quantitative analysis results show that in PCB the relative concentration of O is 4-6, N and S is about 1, and Zn is less than 0.6, if C is set to 100. In CCB, the concentration of S is about 0.3 and without Zn and N.
Abstract: Through Fischer-Tropsch (F-T) synthetic process, coal can be converted to F-T diesel fuel that has high cetane number, very low sulfur and aromatic contents. This paper presents the research results of an unmodified single-cylinder direct injection diesel engine operating on F-T diesel fuel. The indicated pressure diagrams and injector needle lifts were recorded and the combustion and emission characteristics were evaluated and compared with those of conventional diesel fuel operation. The results showed that F-T diesel fuel exhibits a 18.7% average shorter ignition delay, a 26.8% average lower peak value of premixed burning rate, a higher maximum diffusive burning rate and a comparable total combustion duration when compared to conventional diesel fuel. In addition, F-T diesel engine has a slightly lower peak combustion pressure, a far lower rate of pressure rise, and a lower mechanical load and combustion noise. The brake specific fuel consumption is lower and the effective thermal efficiency is higher for F-T diesel fuel operation. CO, HC, NOx and smoke emissions with F-T diesel fuel are reduced at all test speed-load points when compared to conventional diesel fuel. On average, NOx and smoke emissions are reduced by 16.7% and 40.3% respectively with F-T diesel fuel. The study demonstrates that F-T diesel fuel is an excellent clean alternative fuel for diesel engines.
Abstract: With the increasingly strictness of the pollutants emission limits, people have paid more and more attention to the polycyclic aromatic hydrocarbons (PAHs) formation during combustion process. Based on the analysis of PAHs formation mechanisms, including 101 gas species and 504 elemental reactions, the kinetic simulation of PAHs formation during gas phase combustion of the typical volatile matter from plastic pyrolysis using elementary reaction mechanisms was carried out in this work. rB is defined as the ratio of actual fuel/air to stoichiometric fuel/air. The simulation results show that with the increase of rB in combustion at same reaction temperature, the combustion becomes incomplete and the peak value of PAHs mole fraction goes up. Under the same value of rB in combustion, increasing combustion temperature can reduce the incomplete reaction, at the same time, the peak of PAHs appears early, and the peak value increases. In addition, the simulation results of three typical wastes at same conditions of rB and combustion reaction temperature show that the mole fractions of PAHs in the flue gas of paper combustion are less than those of plastic and fabric, and the yields of PAHs for plastic and fabric are almost the same.
Abstract: A laminar flow furnace reactor heated by a plasma jet was designed to study the influences of the biomass components, pyrolysis temperature and residence time on the volatility of biomass materials at flash heating rate and isothermal pyrolysis conditions. The plasma can provide with a high heating rate over 104 K·s-1 to meet the experimental requirement of this work. Flash pyrolysis experiments of coconut shell, cotton stalk and rice husk were conducted in the laminar flow furnace reactor at the temperatures of 750 K, 800 K, 850 K, 900 K, and with the gas passing distance of 0.2 m, 0.25 m, 0.3 m and 0.35 m, respectively. Using the ash as the tracer, the mass percentage of volatile products were obtained. The tests of three models by regression analysis on the experimental data employing statistics software were done to validate the models. The regression results show that the “S” model fits the data well. Compared with the theoretical analysis of the first-order kinetic Arrhenius model, it is found that the “S” model has the same expression as the first-order kinetic Arrhenius model . Thus the first-order kinetic Arrhenius model can be used to simulate the pyrolysis process and predict the percentage of volatile products during flash pyrolysis. The researches indicate that the biomass components, pyrolysis temperature and residence time have great influence on the mass volatile fraction of biomass flash pyrolysis. The mass volatile fraction grows with pyrolysis temperature and residence time. The mass volatile fraction as a function of pyrolysis temperature and residence time in the form of Arrhenius is determined. The volatile products are mainly produced by the pyrolysis of cellulose and hemicellulose, while the char is mainly formed by the pyrolysis of lignin. Therefore, the biomass material with high content of cellulose and hemicellulose would have high volatile yield.
Abstract: A series of Co/TiO2 catalysts were prepared by incipient wetness impregnation. The pH value of the impregnation solution was adjusted by using nitric acid and urea. The XRD, TPR and XPS characterization results indicate that the change of the pH value of the impregnation solution is correlated with the crystal particle size of cobalt oxide species (Co3O4), dispersion behavior and metal-support interaction. When the pH value of the solution is higher than the IEP (ion equipotential point) of titania, the larger Co3O4 particle size could be obtained on the surface of the catalyst. High pH value favores the adsorption and dispersion of active cobalt species over the titanium dioxide, and facilitates the interaction between cobalt and titania, and depresses the reduction degree of the catalyst. In the F-T reaction, catalysts prepared at high pH value have low activities and high methane selectivities. When the pH value of the solution is lower than the IEP of titania, the Co3O4 particle size is small, the interactions between cobalt species and support are weak and the reduction degrees are high, which further enhance the F-T reaction activity and suppress methane selectivity.
Abstract: 1-Butylene epoxidation was catalyzed by microporous titanosilicate molecular sieves TS-1 synthesized by different methods and mesoporous titanosilicate molecular sieves Ti-HMS, using dilute hydrogen peroxide solution as oxidant. The effect of the Si/Ti molar ratio of the catalyst TS-1 and Ti-HMS on their performance was investigated. Conventional TS-1 has smaller crystal size and higher activity than that of TS-1 synthesized by using TPABr as template or the method of gas-solid phase. The TS-1 synthesized by using TPABr as template exhibits the highest selectivity to 1, 2-epoxybutane (BO). With the increase of Ti content in molecular sieves, the conversion of H2O2 increases. The catalytic activity of mesoporous Ti-HMS is lower than that of TS-1, and large amount of H2O2 is decomposed in 1-butylene epoxidation. The primary reason for low activity of Ti-HMS in 1-butylene epoxidation is that Ti-HMS has poorer hydrophobicity property than TS-1.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
