Effect of pressure on direct synthesis of DME from syngas over metal-pillared ilerites and metal/metal-pillared ilerites

The effect of pressure on the direct synthesis of dimethyl ether (DME) from syngas over metal (Cu, Zn) pillared ilerites and metal (Cu, Zn) impregnated metal-pillared ilerites was explored. The prepared catalysts were characterized by XRD, BET, ICP-AES, SEM and FT-IR. The direct DME synthesis reaction was carried out in a differential fixed bed reactor with the prepared catalysts at various pressures (10, 20, 30 bar), 250°C and H₂/CO ratio of 2. The Cu/Zn-pillared ilerite catalyst showed the highest catalytic activity among the prepared catalysts at 20 bar, in which CO conversion was about 62% and DME selectivity was about 89%. CO conversion increased with pressure, and DME selectivity increased with pressure in the range of 10–20 bar, and above the pressure slightly decreased with pressure. The optimum pressure for this reaction was 20 bar.     

Semi-indirect synthesis of LPG from syngas: Conversion of DME into LPG

Efficient conversion of dimethyl ether (DME) into liquefied petroleum gas (LPG) with a hybrid catalyst is a novel method for semi-indirect synthesis of LPG fuel from syngas. The hybrid catalysts consisting of zeolite and hydrogenation catalyst were investigated in a fixed bed reactor. Experimental results demonstrated that the hybrid catalyst consisting of (Pd/SiO₂) and USY efficiently converted DME into LPG and restrained decomposition of DME into CO and H₂. With that catalyst, the one through conversion of DME reached about 100%, almost no CO and CO₂ were produced and selectivity for LPG was more than 65%.     

Intrinsic kinetics study of LPDME process from syngas over bi-functional catalyst

The intrinsic kinetics of the three-phase dimethyl ether (DME) synthesis from syngas over a bi-functional catalyst has been investigated in a agitated slurry reactor at 20–50 bar, 200–240 °C and H₂/CO feed ratio from 1 to 2. The bi-functional catalyst was prepared by physical mixing of CuO/ZnO/Al₂O₃ as methanol synthesis catalyst and H-ZSM-5 as methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H₂, methanol dehydration and water gas shift reaction were chosen as the independent reactions. A kinetic model for the combined methanol and DME synthesis based on a methanol synthesis model proposed by Graaf et al. [G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of low pressure methanol synthesis, Chem. Eng. Sci. 43 (12) (1988) 3185; G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of the three-phase methanol synthesis, Chem. Eng. Sci. 43 (8) (1988) 2161] and a methanol dehydration model by Bercic and Levec [G. Bercic, J. Levec, Intrinsic and global reaction rate of methanol dehydration over γ-Al₂O₃ pellets, Ind. Eng. Chem. Res. 31 (1992) 399–434] has been fitted our experimental data. The obtained coefficients in equations follow the Arrhenius and the Van’t Hoff relations. The calculated apparent activation energy of methanol synthesis reaction and methanol dehydration reaction are 115 kJ/mol and 82 kJ/mol, respectively. Also, the effects of different parameters on the reactor performance have been investigated based on the presented kinetic model.     

含低碳烃气体的低温及常温油吸收工艺的模拟分析

针对费托合成及石油化工等领域含有一定低碳烃类气体的特点,提出了采用低温油吸收回收尾气中烃类组分的工艺,用ASPEN Plus软件建立了低温油吸收的工艺,并模拟分析了低温油吸收的主要工艺参数,与常温油吸收进行比较.结果表明,低温油(-40℃)吸收工艺的低碳烃回收率较高(＞97%),比常温油吸收工艺的低碳烃回收率(66.49%)高约1/3.     

The kinetics of coal chars hydrogasification

Hydrogasification reaction of chars produced from two rank coals was investigated in temperature up to 1173 K and pressure up to 8 MPa. The reactivity of the lignite Szczerców char has been found to be slightly higher than of the subbituminous coal Janina char produced at the same conditions. A high value of the char reactivity was observed to certain carbon conversion, above which a sharp drop takes place. It has been shown that to achieve proper carbon conversion the hydrogasification reaction must proceed at temperature above 1200 K. Based on the active centres theory the kinetic equations of the hydrogasification process were developed and the kinetic constants at the maximum reaction rate evaluated for the analyzed chars.     

A model for alkaline removal of sulfur from a low-rank coal

A low-rank coal cleaned by heavy-liquids separation was treated by 1 M KOH solution at room conditions for a maximum of 2 h. The desulfurization mechanism in terms of total sulfur was well described by the model of unreacted-shrinking core in a homogeneous coal particle of unchanging size during process development. The external diffusion stage might be omitted when modeling this process. A chemical reaction component was considered during diffusive flow of KOH through particle pores, too. It was possible to remove 50% of total sulfur after 2 h of treatment, although three-quarters of achieved conversion happened at first 30 min.     

Effect of inorganic matter on reactivity and kinetics of coal pyrolysis

Two Chinese coals, Shenfu subbituminous coal and Huolingele lignite, were used to investigate the effect of mineral matter in coal on reactivity and kinetic characteristics of coal pyrolysis. The experiments were carried out by using thermogravimetry to check the pyrolysis behavior of raw coal, HCl/HF demineralized coal and demineralized coal with inorganic matter (CaO, K₂CO₃ and Al₂O₃) added, respectively. The results showed that inherent mineral in coal had no evident effect on the reactivity and kinetics of coal pyrolysis. CaO, K₂CO₃ and Al₂O₃ all had a catalytic effect on the reactivity of coal pyrolysis, their effects were closely related to temperature region and coal types. The pyrolysis process of all the samples studied can be described by three independent first order kinetic model. Addition of inorganic matter the activation energy decreased and the characteristic temperature of coal changed.     

A new process for synthesis gas by co-gasifying coal and natural gas

Production of synthesis gas with coal and natural gas co-gasification is a new process based on coupling of methane steam-reforming and coal gasification. The process concept is discussed in this paper. Experiments are carried out in a laboratory fixed-bed gasifying reactor to investigate the effect of feedstock on composition, ratio of hydrogen to carbon monoxide, concentrations of hydrogen and carbon monoxide in the produced raw synthesis gas. Preliminary experimental results indicate that the effect of steam flow rate on component, ratio of hydrogen to carbon monoxide and concentrations of hydrogen and carbon monoxide of the raw synthesis gas is slight, while the effect of oxygen flow rate is pronounced. When the ratio of oxygen to methane in feedstock is below 1, the ratio of hydrogen to carbon monoxide is greater than 1 and the total concentration of hydrogen and carbon monoxide is above 90%. Comparison of experimental results with calculated results shows that the composition of raw synthesis gas is near equilibrium.     

Effect of process conditions on co-liquefaction kinetics of waste tire and coal

Thermal and catalytic liquefactions of waste (recycled) tire and coal were studied both separately and using mixtures with different tire/coal ratios. Runs were made in a batch tubing bomb reactor at 350–425°C. The effect of hydrogen pressure on the product slate was also studied. Mixtures of tire components and coal were used in order to understand the role of the tire as a solvent in co-liquefaction. In the catalytic runs, a ferric-sulfide-based catalyst impregnated in situ in the coal was used. Both the tire components and the entire tire exhibit a synergistic effect on coal conversion. The extent of synergism depends on temperature, H₂ pressure and the tire/coal ratio. Experiments with coal and tire components show that the synergistic effect of tire is due to the rubber portion of the tire and not the carbon black. The synergism mainly leads to an increase in the yields of asphaltenes, which are nearly double those in the coal-only runs at 400°C. The conversion of coal increases dramatically using the catalyst, but the catalytic effect is attenuated somewhat in the presence of tire, especially at high tire/coal ratios. The data were analyzed using a consecutive reaction scheme for the liquefaction of coal to asphaltenes and thence to oil+gas, both reactions being of second order; a second-order conversion of tire to oil+gas; and an additional synergism reaction when both coal and tire are present, first-order in both coal and tire. Parallel schemes were assumed for thermal (uncatalyzed) and catalyzed reactions. The uncatalyzed liquefaction of coal has a low apparent activation energy, 36 kJ/mol, compared to those for the synergism reaction (84 kJ/mol) and the catalytic coal liquefaction (158 kJ/mol). The conversion of asphaltenes to oil+gas is relatively independent of temperature and of the presence of the catalyst. The catalyst appears to play a significant role in the conversion of coal to asphaltenes, but a negligible role in the synergism reaction.     

Simulation of partial oxidation of natural gas to synthesis gas using ASPEN PLUS

Conversion of natural gas to liquid fuels is a challenging issue. In SMDS process natural gas is first partially oxidized with pure oxygen to synthesis gas (a mixture of H₂ and CO) which is then converted to high quality liquid transportation fuels by utilizing a modernized version of the Fischer-Tropsch reaction. This paper presents a computer simulation of the first stage of the process, i.e. the synthesis gas production from natural gas. ASPEN PLUS equipped with a combustion databank was used for calculations. Concentrations of over 30 combustion species and radicals expected in the synthesis gas have been calculated at equilibrium and several non-equilibrium conditions. Using a sensitivity analysis tool, the relative feed flow rates and reactor parameters have been varied searching to maximize the CO/O₂ yield as well as to minimize the undesired nitrogen compounds in the product stream. The optimum reactor temperature for maximizing the CO mole fraction in the synthesis gas was also calculated.     

浆态床合成气合成二甲醚的工艺研究

考察了反应温度、反应压力、进料空速对浆态床合成二甲醚反应过程的影响,结果表明,在245～300℃范围内,随着反应温度的升高,一氧化碳转化率、二甲醚选择性和时空收率逐渐增加,在265℃时达到最大值后开始下降;在3.0～5.0MPa范围内,随压力的升高,一氧化碳转化率、二甲醚选择性和时空收率逐渐增加;在700～2500h-1范围内,一氧化碳转化率、二甲醚选择性随空速的增加而逐渐减小,空速以1200h-1为宜。     

Research into the kinetics of COS elimination from syngas at moderate temperatures

Thermogravimetry at constant temperature and programmed temperatures is used to study reaction kinetics and possible mechanism of COS desulfurization using ferric oxide as the main active component. The apparent reaction activation energy is smaller in hydrogen atmosphere than in nitrogen. The desulfurization reaction of COS takes place easily in a hydrogen atmosphere. At the same time, the influence of the reducing temperature on the desulfurizing reaction was also studied in the TGA apparatus and was shown to play an important part for ferric desulfurization. The optimum temperature for the reducing reaction is under 360 °C. The kinetics of the COS removal reaction are approximately first-order. When the reaction gas contains hydrogen, the apparent reaction activation energy is 12.36 kJ mol⁻¹, in contrast to 21.92 kJ mol⁻¹ in the absence of hydrogen.     

Predictive model for countercurrent coal gasifiers

The paper deals with a model able to predict the stationary operating conditions of a moving bed gasifier with upflow of gas. The model was used to simulate coal gasifiers but the proposed approach can also be useful for biomass gasifiers. The model considers the different phenomena that occur along the reactor: drying and pyrolysis take place at the top, while the behaviour of the lower part is dominated by the combustion and gasification reactions between the coal char and the oxidizing gas. The model is structured into two levels: particle level and reactor level. At the particle level, the strong gradients of temperature in the single pellet caused by external heating were taken into account. Literature kinetic models developed with isothermal particles were employed. The calculated results of fixed carbon yield and gas were compared with experimental results obtained in our laboratory.At the whole apparatus level, the reactor was subdivided into two zones: pyrolysis (upper) zone and gasification/combustion (lower) zone. The upper zone was modelled by coupling convective heating of the particles, temperature gradients inside the particles and kinetics. In the lower zone transport of heat by radiation was taken into consideration. The governing equations were solved as a boundary condition problem, leading to a stable and reliable solution. The model was validated by comparison with some literature data of full scale gasifiers.     

生物质合成燃料二甲醚的技术

介绍和分析了生物质合成气的制备工艺和合成气组分调整工艺，提出了生物质合成液体燃料二甲醚的工艺路线，展望了生物质合成二甲醚技术的前景。     

三相床中合成气一步法制二甲醚

在反应温度 2 30～ 2 70℃、压力 2～ 5MPa下 ,以医药用石蜡油为惰性液相介质 ,使用C30 2铜基催化剂和CM - 3- 1改性分子筛组成的复合催化剂 ,在三相搅拌釜中研究了合成气 (CO、CO2 、H2 )一步法合成二甲醚的反应。结果表明随着温度的升高 ,碳的转化率增加 ,二甲醚的选择性提高 ,甲醇的选择性降低 ;随着压力的增加 ,碳的转化率升高 ,二甲醚的选择性提高 ,甲醇的选择性降低     

Simulation and energy consumption analysis of a propane plus recovery plant from natural gas

This paper deals with the investigation of a cryogenic plant for the recovery of propane plus compounds from natural gas. The commercially available software ASPEN Plus® has been used to simulate the process, and to investigate the effect of the main operating variables on the efficiency of propane plus recovery and on the energy required by the various pieces of equipment of the plant. With respect to the base case considered, the optimized plant allows to reduce the heat required up to 25%; besides, the refrigeration required can be reduced up to 60%, without significantly affecting the propane plus recovery.     

Gasification of an Indonesian subbituminous coal in a pilot-scale coal gasification system

Indonesian Roto Middle subbituminous coal was gasified in a pilot-scale dry-feeding gasification system and the produced syngas was purified with hot gas filtering and by low temperature desulfurization to the quality that can be utilized as a feedstock for chemical conversion. Roto middle coal produced syngas that has a typical composition of 36–38% CO, 14–16% H₂, and 5–8% CO₂. Particulates in syngas were 99.8% removed by metal filters at the operating temperature condition of 200–250°C. Sulfur containing compounds of H₂S and COS in syngas were also desulfurized in the Fe chelate system to yield less than 0.5 ppm level. The full stream gasification and syngas purifying system has been successfully operated and thus can provide clean syngas for the research on the conversion of syngas to chemicals like DME and on the future IGFC using fuel cells. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

共沉淀法制备浆状催化剂前躯体对一步法合成二甲醚的影响

用共沉淀法制备一步法合成二甲醚浆状催化剂的前躯体,完全液相热处理后,在浆态床中对其催化性能进行了测试,通过XRD、BET和元素分析对其进行了表征。结果表明,将Zr组分引入CuZnSiAl催化剂后,催化剂二甲醚的选择性提高。     

Effect of surfactant on structure and performance of catalysts for DME synthesis in slurry bed

The Cu-Zn-Al slurry catalysts prepared via modified sol-emulsion-gel method by adding different water-soluble surfactants were studied for CO hydrogenation to produce dimethyl ether (DME) in slurry bed reactor. The results indicated that the catalyst adding Tween80 or PEG600 had higher activity than the catalyst with the PVP additive. All the catalysts had good stability. X-ray diffraction (XRD) results showed that Cu and Cu₂O existed in the pre-reduced Cu-Zn-Al catalysts, while ZnO did not appear. Nitrogen adsorption studies showed that the catalyst prepared with the additives of PEG600 or Tween80 was mesoporous structure with higher specific surface area compared with the one prepared with the additive of PVP. X-ray photoelectron spectroscopy (XPS) results indicated that the Cu/Zn ratio on the surface of all catalysts increased after subject to reduction and reaction. The morphology and size of the catalyst particles could be adjusted by adding water-soluble surfactants.     

Hydrogen production from partial oxidation and reforming of DME

Hydrogen production from partial oxidation and reforming of dimethyl ether (DME) was investigated with a fixed bed continuous-flow reactor. H₂ yield of over 90% was obtained with 100% DME conversion at 700 °C over Pt/Al₂O₃+Ni–MgO dual catalyst bed, while keeping CH₄ yield at low level. Such results indicated that partial oxidation and reforming of DME to produce hydrogen at high temperature is possible and effective.