F-T合成催化剂羰基硫中毒热力学分析

利用热力学基础数据和相关软件对F-T合成催化剂COS中毒的热力学进行了计算。在热力学上,Ru、Fe、Co的COS中毒在F-T合成反应可以发生的条件下均是自发过程。F-T合成反应体系中10^-9级的COS即可使Ru基催化剂中的金属Ru生成RuS₂而中毒。Fe和Co毒化后生成的硫化物种类较多,对反应的热力学计算结果表明,对于不同的反应,其平衡常数的差异很大,对应中毒反应发生时,所需COS的浓度也不同。由于Fe基F-T合成催化剂活性相的复杂性,利用对催化剂相关性质的修饰开发具有一定抗硫性的铁基F-T合成催化剂是可行的;对于Co催化剂,利用F-T合成的反应特点和催化剂改性开发具有一定抗硫性催化剂也是可能的。     

氧化铝负载Co基F-T合成催化剂还原性能

采用XRD、TPR、XPS和H2-TPD等技术对Co/Al2O3催化剂的还原性能进行了研究.还原温度低时,催化剂中Co物种还原不充分,活化不够,催化剂的F-T合成反应活性偏低;高温还原时,由于催化剂中金属钴颗粒聚集和增大使活性组分的有效活性面积减小,催化剂的F-T合成反应活性下降.还原温度在400～500℃之间存在最佳...     

Removal of carbonyl sulfide and hydrogen sulfide from synthesis gas byChlorobium thiosulfatophilum

Applied Biochemistry and Biotechnology - The anaerobic, photosynthetic bacteriumChlorobium thiosulfatophilum utilizes CO2 as its carbon source and operates at the mesophilic temperature of...     

Mechanism of oxygen poisoning of ammonia synthesis catalyst

The effect of oxygen adsorbed on the surface of a commercial catalyst from a mixture of hydrogen with water vapor on the steady-state and nonsteady-state ammonia synthesis kinetics is studied under gradientless conditions at the pressures of the stoichiometric nitrogen-hydrogen mixture below the atmospheric pressure and at the temperatures of 285 and 240°C. The results obtained are discussed on the basis of the concepts of the ammonia synthesis theory of Temkin. The poisoning effect of oxygen on the reaction rate is explained by an increase in the activation energy of the rate constant k ₊ in the Temkin-Pyzhev equation, i.e., an increase in the activation energy of the rate constant of nitrogen adsorption at the fixed nitrogen adsorption heat. This conclusion agrees with the concepts of Ertl et al., according to which the activation energy of nitrogen adsorption on iron changes in symbasis with the variation of the electronic work function. Oxygen adsorption on the catalyst surface increases the electronic work function. Thus, the mechanism of the catalyst poisoning by oxygen (at its low surface coverage) consists in an increase in the electronic work function. Assumptions are stated as to the role of chemical promoters of iron catalysts.     

内扩散行为对F-T合成反应过程影响的研究

选用Co/ZrO2催化剂,通过改变催化剂颗粒径,在积分固定床反应器上研究了内扩散行为对F-T合成反应过程的影响。以表观活化能、烯/烷比的变化等为依据,考察了内扩散行为对F-T合成反应历程、催化剂活性及产物选择性的影响。催化剂颗粒径不同,内扩散限制程度会发生相应变化。实验结果表明,不同程度的内扩散限制条件下,F-T合成反应历程会有较大差异。当反应开始后,颗粒内孔从"干"到"湿",不同粒径的催化剂颗粒上气态烯/烷比变化均呈"U"型趋势。在固定床反应器上,增加空速通常会有CH4选择性升高、气态烯/烷比略有增加的现象,这是由于内扩散限制未完全消除的缘故。     

葡萄糖和Pd对钴基费托合成催化剂结构和性能的影响

采用等体积浸渍法制备SiO₂负载的钴基催化剂,利用N₂低温吸附、XRD、SEM和H₂-TPR等方法表征了在浸渍操作中添加葡萄糖和助剂Pd对催化剂结构和性质的影响,并在固定床反应器中评价了催化剂的费托合成反应性能。葡萄糖和Pd能够改变Co₃O₄晶粒形状,添加葡萄糖提高了Co₃O₄的分散程度,助剂Pd促进了Co₃O₄还原。两者的联合使用则同时提高了钴物种分散度和还原度,从而改善了催化剂的费托合成反应活性和C₅₊烃选择性。     

Alternating copolymerization of carbonyl sulfide with aziridines

The copolymerization of carbonyl sulfide with aziridines such as ethylenimine, propylenimine, and N-ethylethylenimine was studied in various organic solvents. The copolymerizations occurred easily without the addition of any catalyst and gave white powdery crystalline copolymers. The copolymers produced were insoluble in many organic solvents, but soluble in p-chlorophenol and dimethyl sulfoxide. The elementary analyses and the infrared spectra showed that alternating copolymers which have a thiourethane structure were produced. In the copolymerization of carbonyl sulfide with ethylenimine, both the polymer yield and the molecular weight of the resulting polymer increased with the use of a solvent having a higher dielectric constant, and also with an increase in the ratio of carbonyl sulfide to imine in the feed. The rate of copolymerization of carbonyl sulfide with aziridines was in the order of ethylenimine > propylenimine > and N-ethylethylenimine. Irradiation of the copolymers improved their thermal properties and increased their melting point.     

Mechanism of heterogeneous reaction of carbonyl sulfide on magnesium oxide

Heterogeneous reaction of carbonyl sulfide (OCS) on magnesium oxide (MgO) under ambient conditions was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), quadrupole mass spectrometer (QMS), and density functional theory (DFT) calculations. It reveals that OCS can be catalytically hydrolyzed by surface hydroxyl on MgO to produce carbon dioxide (CO2) and hydrogen sulfide (H2S), and then H2S can be further catalytically oxidized by surface oxygen or gaseous oxygen on MgO to form sulfite (SO3(2-)) and sulfate (SO4(2-)). Hydrogen thiocarbonate (HSCO2-) was found to be the crucial intermediate. Surface hydrogen sulfide (HS), sulfur dioxide (SO2), and surface sulfite (SO3(2-)) were also found to be intermediates for the formation of sulfate. Furthermore, the surface hydroxyl contributes not only to the formation of HSCO2- but also to HSCO2- decomposition. On the basis of experimental results, the heterogeneous reaction mechanism of OCS on MgO was discussed.     

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over AlzO3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon(CAC) catalysts loaded by Al2O3were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide(COS) and carbon disulfide(CS2) at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2concentration, gas hourly space velocity(GHSV) and relative humidity(RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3calcined at 300 ℃ had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2decrease. A small amount of O2introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.     

Structures and vibrational spectra for protonated carbonyl sulfide

The HOCS⁺ form of protonated OCS was identified in 1987 using high-resolution difference frequency laser spectroscopy by assigning the vibrational frequency (ν=3435cm⁻¹) as the O-H stretch. The isomer HSCO⁺ was not detected in spite of a search of the S-H stretching region. Theoretical calculations indicate, however, that the S-protonated form lies significantly lower than the O-protonated form. To resolve this apparent discrepancy between experiments and theoretical calculations, highly accurate ab initio studies of both species have been carried out. Our results indicate that the S-protonated form lies about 5 kcal/mol below the O-protonated one. The SH stretching frequency is predicted to be found around 2496cm⁻¹. A new search for the ν₁ band of HSCO⁺ using a diode spectrometer showed no evidence of HSCO⁺. Received: 26 November 1996 / Accepted: 3 March 1997     

Benzene hydrogenation on sulfide catalyst under unsteady-state conditions

A kinetic model of benzene hydrogenation on a sulfide hydropurification catalyst (Ni,Mo)/Al₂O₃ has been developed. The model describes well the experimental data obtained under unsteady-state conditions and relies on the assumption that the catalyst surface contains only one type of active sites, i.e., Ni atoms in the sulfide bimetallic complex, and makes allowance for the transition of active sites into inactive sites. This revised version was published online in August 2006 with corrections to the Cover Date.     

Temperature dependence of the heterogeneous reaction of carbonyl sulfide on magnesium oxide

The experimental determination of rate constants for atmospheric reactions and how these rate constants vary with temperature remain a crucially important part of atmosphere science. In this study, the temperature dependence of the heterogeneous reaction of carbonyl sulfide (COS) on magnesium oxide (MgO) has been investigated using a Knudsen cell reactor and a temperature-programmed reaction apparatus. We found that the adsorption and the heterogeneous reaction are sensitive to temperature. The initial uptake coefficients (gammat(Ini)) of COS on MgO decrease from 1.07 +/- 0.71 x 10-6 to 4.84 +/- 0.60 x 10-7 with the increasing of temperature from 228 to 300 K, and the steady state uptake coefficients (gammat(SS)) increase from 5.31 +/- 0.06 x 10-8 to 1.68 +/- 0.41 x 10-7 with the increasing of temperature from 240 to 300 K. The desorption rate constants (kdes) were also found to increase slightly with the enhancement of temperature. The empirical formula between the uptake coefficients, desorption rate constants and temperature described in the form of Arrhenius expression were obtained. The activation energies for the heterogeneous reaction and desorption of COS on MgO were measured to be 11.02 +/- 0.34 kJ.mol-1 and 6.30 +/- 0.81 kJ.mol-1, respectively. The results demonstrate that the initial uptake of COS on MgO is mainly contributed by an adsorption process and the steady state uptake is due to a catalytic reaction. The environmental implication was also discussed.     

Adsorption of carbonyl sulfide on modified activated carbon under low-oxygen content conditions

Activated carbon sorbents impregnated with KOH, Fe(NO₃)₃, Cu(NO₃)₂, Zn(NO₃)₂ or Co(NO₃)₂ and their applications in catalytic oxidation reaction of COS were investigated. The results showed that the activated carbon modified with 10 % (mass percentage) KOH enhanced the adsorption ability significantly. And it was also found that the oxygen content and temperature were the two most important factors in the COS adsorption. Further investigation on the pore structures of the samples with X-ray photoelectron spectroscopy indicated that an adsorption/oxidation process happened in the KOH modified activated carbon in which the major existing forms of sulfur were SO₄ ^2? and S species. The oxidation of COS suggested that KOH in the micropores may play a catalytic role during the adsorption. On the other hand, we found that the desorption activation energy from KOHW was higher than that from AC by the CO₂-TPD spectra, which indicated the adsorption of CO₂ on KOH impregnated activated carbon was stronger. The strong adsorption could be attributed to the basic groups on the activated carbon surface. In conclusion, the activated carbon impregnated with KOH promises a good candidate for COS adsorbent.     

Thermodynamics of the system lead sulfide and thiol collector

The thermodynamics of the systems between lead sulfide and two thiol collectors, potassium ethyl xanthate and sodium diethyl dithiophosphate, have been examined in this work. It was found that the experimental data cannot be explained using the thermodynamics of bulk phases. Therefore, a mixed phase model was developed in which the concentrations of the components PbS and (PbX)₂S in the surface phase are taken into account. When the experimental results are compared with the theoretical ones it could be found that the system of ethyl xanthate and lead sulfide behaves as an ideal mixed phase, whereas the system of diethyl dithiophosphate behaves non-ideally, i.e. the activity coefficients of the components in the surface phase are unity in the former system but differ from unity in the latter case. This difference is probably due to the different sizes of the two thiol collector molecules.     

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al2O3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon(CAC) catalysts loaded by Al2O3were prepared by sol-gel method and used for the simultaneous catalytic hydrolysis of carbonyl sulfide(COS) and carbon disulfide(CS2) at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as: reaction temperature, O2concentration, gas hourly space velocity(GHSV) and relative humidity(RH) were also discussed respectively. The results showed that catalysts with 5.0 wt% Al2O3calcined at 300 ℃ had superior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2decrease. A small amount of O2introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.     

High CO methanation activity on zirconia-supported molybdenum sulfide catalyst

In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high methanation performance. CO conversion could reach up to 90% on 25 wt% MoO3/ZrO2 catalyst, much higher than that on the conventional 25 wt% MoO3/Al2O3 catalyst. The Mo-based catalysts were characterized by XRF, XRD, Raman, BET, TEM and H2-TPR etc. It was found that MoO3 particles were highly dispersed on ZrO2 support for 25 wt% MoO3/ZrO2 catalyst prepared at 65-85℃ because of its relatively larger pore size, which contributed to a high CO conversion. Meanwhile, when MoO3 loading exceeded the monolayer coverage, the formed crystalline MoO3 and ZrM020g might block the micropores of the catalyst and make the methanation activity declined. These results are useful for preparing highly efficient catalyst for CO methanation process.     

A new synthesis of 1,3-thiazines and their transformation into 1-substituted-6-alkyluracils by extrusion of carbonyl sulfide

A simple synthesis of 5-acyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-diones from malonic acid, potassium thiocyanate and acid anhydrides is described. A new, general, regioselective method for the synthesis of 1-substituted-6-alkyluracils by the reaction of these thiazines with primary alkyl and arylamines is reported.     

Variation of pH in reaction of sodium sulfide with carbonyl compounds

The results of an experimental study of how pH varies in the course of a reaction between sodium sulfite and carbonyl compounds are presented.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 2031–2035.Original Russian Text Copyright © 2004 by A. Ivanov, Altukhova, I. Ivanov.     

Polynuclear nitrosyl carbonyl ReI complexes with thiolate and sulfide bridges

The reaction of the complex Re₂(CO)₄(NO)₂Cl₄ (1) with NaSCMe₃ (2) (in THF or MeCN, 65–80°C, 24 h) was studied at different ratios of the reagents (from 1∶2 to 1∶6). At the reagent ratio of 1∶2, the binuclear complex Re₂(CO)₄(NO)₂Cl₂(μ-SCMe₃)₂ (3) was obtained as a mixture ofsyn andanti isomers (3a and3b, respectively) containing Re₂S₂ fragments with different structures (the butterfly-like structure in3a and the planar fragment in3b). When the initials were taken in ratios from 1∶4 to 1∶6, two compounds were isolated: the binuclear complex Re₂(CO)₄(NO)₂(μ-SCMe₃)₂(μ-S)4 (cocrystallized as a mixture ofsyn andanti isomers,4a and4b, respectively) and the triangular cluster Re₃(CO)₃(NO)₃(μ-SCMe₃((μ₃-S)(μ₃-Cl) (5). Apparently, complex4 is formed in the course of isolation as a result of elimination of SR₂ from the unstable tetrathiolate dimer Re₂(CO)₄(NO)₂(SCMe₃)₂(μ-SCMe₃)₂ (6). Cluster5 is the product of the reaction between compounds3 and4. Products of interaction of compound6 with silica gel upon column chromatography of the reaction mixture were studied. Four complexes containing hydroxy and oxo bridging groups, (CO)₂(NO)Re(μ-SCMe₃)₂(μ-OH)Re(SCMe₃)(CO)(NO) (7), (CO)₃(NO)₃RE₃(μ-SCMe₃)₃(μ₃-SCME₃)(μ₃-O) (8), [(CO)₂(NO)₂Re₂(SCMe₃)₂(μ-SCMe₃)₂(μ-OH)][Na(THF)(Et₂O)] (9), and [(CO)₂(NO)₂Re₂(SCMe₃)₂(μ-SCMe₃)₂(μ-OH)]₂−[Na(H₂O)₆][H₅O₂] (10), were isolated. The structures of complexes3, 4, 5, 7, 8, 9, and10 were established by X-ray diffraction study. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1030–1044, May, 1998.