合成气直接合成二甲醚的工艺研究

本文考察了二氧化碳浓度、空速、温度在合成气直接合成二甲醚过程中对双功能催化剂的影响，结果表明，合成比2．85，在CO2浓度4．2％－7．15％范围内，随着CO2浓度增加，CO的转化率和DME的选择性逐渐下降，在进气空速1300－3200h^-1范围内，CO的转化率和DME的选择性随空速的增加而减小，但在1500h^-1左右CO的转化率和DME的选择性较高；在反应温度265－300℃范围内，CO的转化率和DME的选择性随浊度的升高而增加，但在285－300℃之间两者变化不大，最佳条件：CO2浓度5．2％，空速1500h^-1,温度285℃。     

煤制合成天然气甲烷化反应研究

采用本征动力学装置进行了煤制合成天然气(SNG)甲烷化反应研究,实验采用0.154~0.198mm的自制甲烷化催化剂NJ34,反应温度300~500℃,反应压力2.0~5.0 MPa,体积空速5 000~9 000h-1。实验结果表明,在温度和空速一定的条件下,反应压力的变化对催化剂的CO转化率、CO2转化率以及总碳转化率的影响不明显;在反应温度和压力一定的条件下,气体空速的变化对催化剂的CO转化率的影响不明显,CO2转化率出现了一定的波动;在压力和空速一定的条件下,随着反应温度的提高,CO和CO2转化率都呈下降趋势,且CO2转化率的下降更加显著。     

不同工艺条件下耐硫甲烷化催化剂的反应活性研究

考察了钼基耐硫甲烷化催化剂在不同反应温度下的催化活性,结果表明反应温度在560℃附近时甲烷化活性最高。在此温度下研究了空速、原料气中H2S、H2O、CO2、CH4、H2/CO等浓度对反应活性的影响,结果表明,原料气中H2S含量的增加有利于提高催化剂的甲烷化反应活性;H2O的加入促进了水煤气变换反应的进行但抑制了甲烷化反应,因此CO转化率虽没有下降但甲烷化效率却有所降低;添加CH4对甲烷化反应没有明显影响,而添加CO2则明显抑制了甲烷的生成。结合催化剂表征结果进一步对各因素的影响机理进行了分析,这为耐硫甲烷化工艺条件优化及催化剂设计提供了重要依据。     

一种高活性耐硫甲烷化催化剂的反应性能

本文报道了一种多组分钼系耐硫甲烷化催化剂的反应性能。考察了反应温度、压力、空速和原料气组成对活性的影响,结果表明,此催化剂具有活性高、稳定性好和对原料气中硫浓度适应性强等特点。在压力2.0MPa、空速1000h~(-1)、入口温度380℃的反应条件下,CO 转化率约达95％,甲烷选择性约为75％。CO 转化率与原料气中 H_2S 浓度呈X_(co)∞[H_2S]~(0.05)关系。     

添加WO_3对铈钴催化剂CO氧化性能的影响

采用共沉淀法制备xWO_3-Ce O2-Co_3O_4复合型非贵金属CO低温催化剂,考察不同WO_3添加量和空速对催化剂催化活性的影响,并考察催化剂的抗硫性能。通过孔隙结构测试、H2-TPR、FT-IR和SEM等对催化剂进行表征。结果表明,WO_3添加质量分数1%时,催化剂具有最佳的低温活性。在CO进口体积分数0.12%、O2进口体积分数5%和空速15 000 h-1条件下,50℃时,CO转化率即可达到99.6%,60℃时,CO转化率达100%。添加WO_3,催化剂氧化能力增强,催化效率提高。随着空速升高,CO转化率下降。WO_3的加入可有效提高催化剂的比表面积,抑制硫酸盐在催化剂表面聚集,提高催化剂的抗硫性能。     

合成甲醇铜基催化剂反应条件的研究

本文叙述了反应条件对合成甲醇铜基催化剂活性(时空收率和 CO 转化率)的影响.时空收率和 CO 转化率均随反应压力的升高而增加;在一定空速范围内,时空收率随空速增大而增加,而CO 转化率随空速的增大而降低;反应温度为250℃时,时空收率和 CO 转化率均达最高值.     

合成碳酸二甲酯宏观动力学及反应器数值模拟

在固定床反应器中研究了PdCl_2-CuCl_2-KOAc/AC催化剂上甲醇气相氧化羰基化合成碳酸二甲酯(DMC)反应的宏观动力学,建立了以CO、O_2、甲醇分压表示的幂函数动力学模型,统计检验表明所得模型具有较高的可信度。依据动力学模型,建立了用于该反应过程的固定床反应器二维拟均相模型,借助Matlab软件,模拟分析了空速、原料组成、进口温度、操作压力和管外介质温度等因素对反应过程的影响。模拟计算结果显示,操作压力和空速对反应器的热点温度影响显著,而甲醇的转化率及DMC对CO的选择性受原料组成影响较大。优化确定了在PdCl_2-CuCl_2-KOAc/AC催化剂上甲醇气相氧化羰基化合成碳酸二甲酯适宜的条件为进料组成CH_3OH/CO/O_2的体积比为0.20:0.27:0.53,空速7 500 h~(-1),进口温度160℃,操作压力0.30 MPa。在该条件下,床层的热点温度为214.96℃,甲醇的转化率为51.69%,DMC对CO的选择性为65.92%。     

工艺条件对碳二前加氢催化剂性能的影响

以α-Al2O3为载体,钯为活性组分,银为助剂制备了前加氢催化剂,并在750 mL工业侧线装置上与进口催化剂进行了对比评价。考察了入口温度、空速和CO含量三个工艺参数对碳二前加氢催化剂性能的影响,结果表明:提高入口温度,催化剂乙炔转化率、MAPD转化率升高,乙烯增量先增加后降低;和入口温度相比,空速对催化剂性能的影响稍小;CO含量对催化剂性能影响较大。     

整体式Fe-β分子筛成型方法及其催化N_2O分解反应性能

为了降低催化剂床层压降,提高Fe-β分子筛催化剂用于N_2O催化分解的能力,通过研究整体式分子筛催化剂制备方法,优化出最优原料配比为ω(拟薄水铝石)=40%,ω(硝酸)=8%,水粉比为0.6 m L·g~(-1)。研究了成型过程对分子筛催化剂结构及性能的影响,并在不同孔密度分子筛催化剂、N_2O浓度和空速条件下考察N_2O分解反应性能。结果表明,在相同温度、空速和N_2O浓度下,分子筛催化剂的孔密度越高,催化活性呈增强趋势;对于相同孔密度的分子筛催化剂,随着空速的增加,相同温度下的N_2O转化率逐渐下降;对于相同孔密度的分子筛催化剂,在相同反应空速和温度下,随着N_2O浓度的增大,N_2O转化率呈上升趋势。     

MK-101催化剂作用下操作条件对甲醇合成的影响研究

实验模拟低压甲醇合成工艺流程,在压力4～7MPa,温度210～270℃,空速6000～15000h-1,CO2浓度4.5%～14.3%的实验条件下,选用MK-101催化剂,考察了温度、压力、空速和CO2浓度对甲醇合成反应的CO、CO2的单程转化率和甲醇时空收率的影响。     

Conversion of syn-gas to lower alkenes over Fe-TiO2-ZnO-K2O catalyst system

Conversion of syn-gas to lower alkenes is studied over a multicomponent catalyst system, Fe-TiO₂-ZnO-K₂O. Various reaction variables affecting the conversion were studied. At H₂:CO=1, 2.5 kg/cm² pressure, 250°C temperature and GHSV=960 h⁻¹, maximum selectivity of 68% to alkenes was obtained at 45% conversion of the feed. The alkenes consist of a mixture of propylene (65%) and ethylene (35%). The catalyst is active even after 200 h of use. The catalyst samples were characterised by BET surface area measurements, TPR and TPD. XRD and ESCA studies reveal the presence of Fe₂O₃ phase in the fresh catalyst. This phase is ably promoted by Zn and K. On reaction with CO+H₂, electron-rich species are formed on catalyst surface, which are the most likely active species. In addition to this, there is an improvement in dispersion of the active phase. These factors may contribute toward better performance of the catalyst in the conversion of syn-gas to lower alkenes.     

Catalytic reduction of NO by CO over NiO/CeO2 catalyst in stoichiometric NO/CO and NO/CO/O2 reaction

A new catalyst composed of nickel oxide and cerium oxide was studied with respect to its activity for NO reduction by CO under stoichiometric conditions in the absence as well as the presence of oxygen. Activity measurements of the NO/CO reaction were also conducted over NiO/γ-Al₂O₃, NiO/TiO₂, and NiO/CeO₂ catalysts for comparison purposes. The results showed that the conversion of NO and CO are dependent on the nature of supports, and the catalysts decreased in activity in the order of NiO/CeO₂ > NiO/γ-Al₂O₃ > NiO/TiO₂. Three kinds of CeO₂ were prepared and used as support for NiO. They are the CeO₂ prepared by (i) homogeneous precipitation (HP), (ii) precipitation (PC), and (iii) direct decomposition (DP) method. We found that the NiO/CeO₂(HP) catalyst was the most active, and complete conversion of NO and CO occurred at 210 °C at a space velocity of 120,000 h⁻¹. Based on the results of surface analysis, a reaction model for NO/CO interaction over NiO/CeO₂ has been proposed: (i) CO reduces surface oxygen to create vacant sites; (ii) on the vacant sites, NO dissociates to produce N₂; and (iii) the oxygen originated from NO dissociation is removed by CO.     

低负载Pd/Al2O3催化剂的制备及其对CO室温催化性能研究

采用等体积浸渍法和还原法结合制备了Pd/Al_2O_3催化剂,通过N_2吸附-脱附、SEM、TEM、X射线衍射、X射线光电子能谱和CO原位漫反射傅里叶变换红外光谱等表征手段对制备的样品微观结构进行了系统分析,考察了不同Pd负载量和测试条件下CO催化氧化性能。实验结果表明,水合肼还原法实现了Pd在Al_2O_3载体上的均匀分散,Pd颗粒的直径在9 nm左右,且为Pd单质;负载后的催化剂呈现明显的中孔结构特征,有利于气体分子的扩散。在0.2%～0.5%的低负载质量分数下,CO的催化性能随着Pd负载量的增加而增加,随着CO进口浓度和空速的升高而逐渐降低,在进口浓度为0.05%,空速为4 017 h~(-1)时,不同负载量的催化剂均能使CO完全催化;温度对催化剂的催化效果影响显著,从常温到50℃催化剂的性能变化显著;湿度增加对催化有一定的促进作用。Pd负载质量分数0.5%的催化剂稳定性测试表明,催化剂能够在100 h内保持92%以上的稳定转化率。     

CO oxidation and oxygen-assisted CO adsorption/desorption on Ag/MnOx catalysts

A series of Ag-doped manganese oxide catalyst were synthesized by the reflux method in an acid medium. The surface structure of the catalysts was characterized by N₂ adsorption, XRD and TEM experiments. The catalysts showed excellent catalytic activity for CO oxidation. The adsorption and oxidation of CO on a 1.0% Ag/MnO_x catalyst between 393 and 493 K were studied by means of single pulse experiments in a TAP reactor. The adsorption of CO was reversible at these temperatures and CO₂ was formed in an oxidation reaction of CO and lattice oxygen. Curve fitting to the experimental TAP response curves of the reactant and product was used to determine the kinetic parameters for the elementary steps. The activation energies were 83 kJ/mol for CO desorption, 31 kJ/mol for CO₂ desorption, and 116 kJ/mol for the surface CO oxidation by lattice oxygen. In addition, the effect of coadsorbed O₂ on CO adsorption was studied by the TAP technique. Below 353 K, there was a sharp increase, by about one order of magnitude, in the rate constant of CO adsorption promoted by the presence of coadsorbed O₂.     

Catalytic NO reduction with ammonia at low temperatures on V2O5/AC catalysts: effect of metal oxides addition and SO2

The catalytic behavior of the V-M/AC (M=W, Mo, Zr, and Sn) catalysts were studied for the NO reduction with ammonia at low temperatures, especially in the presence of SO₂. The presence of the metal oxides does not increase the V₂O₅/AC activity but decreases it. Except V-Mo/AC, the other catalysts are promoted by SO₂ at 250°C, especially for V-Sn/AC. However, the promoting effect of SO₂ is gradually depressed by catalyst deactivation. Changes in catalyst preparation method can improve the catalyst stability in short-term but cannot completely prevent the catalyst from a long-term deactivation. Mechanisms of the promoting effect and the deactivation of V-Sn/AC catalyst by SO₂ were studied using Fourier transform infrared spectroscopy (FT-IR) spectra and measurement of catalyst surface area and pore volume. The results showed that both the SO₂ promotion and deactivation are associated with the formation of sulfate species on the catalyst surface. In the initial period of the selective catalytic reduction (SCR) reaction in the presence of SO₂, the formed sulfate species provide new acid sites to enhance ammonia adsorption and thus the catalytic activity. However, as the SCR reaction proceeds, excess amount of sulfate species and then ammonium-sulfate salts are formed which is stabilized by the presence of tin oxide, resulting in gradual plugging of the pore structures and the catalyst deactivation.     

Fischer–Tropsch synthesis over Co–SiO2 catalysts prepared by the sol–gel method

Fischer–Tropsch synthesis was carried out in slurry phase over uniformly dispersed Co–SiO₂ catalysts prepared by the sol–gel method. When 0.01–1 wt.% of noble metals were added to the Co–SiO₂ catalysts, a high and stable catalytic activity was obtained over 60 h of the reaction at 503 K and 1 MPa. The addition of noble metals increased the reducibility of surface Co on the catalysts, without changing the particle size of Co metal significantly. High dispersion of metallic Co species stabilized on SiO₂ was responsible for stable activity. The uniform pore size of the catalysts was enlarged by varying the preparation conditions and by adding organic compounds such as N,N-dimethylformamide and formamide. Increased pore size resulted in decrease in CO conversion and selectivity for CO₂, a byproduct, and an increase in the olefin/paraffin ratio of the products. By modifying the surface of wide pore silica with Co–SiO₂ prepared by the sol–gel method, a bimodal pore structured catalyst was prepared. The bimodal catalyst showed high catalytic performance with reducing the amount of the expensive sol–gel Co–SiO₂.     

K-, CeO2-, and Mn-promoted Ni/Al2O3 catalysts for stable CO2 reforming of methane

Reforming of methane with carbon dioxide into syngas over Ni/γ-Al₂O₃ catalysts modified by potassium, MnO and CeO₂ was studied. The catalysts were prepared by impregnation technique and were characterized by N₂ adsorption/desorption isotherm, BET surface area, pore volume, and BJH pore size distribution measurements, and by X-ray diffraction and scanning electron microscopy. The performance of these catalysts was evaluated by conducting the reforming reaction in a fixed bed reactor. The coke content of the catalysts was determined by oxidation conducted in a thermo-gravimetric analyzer. Incorporation of potassium and CeO₂ (or MnO) onto the catalyst significantly reduced the coke formation without significantly affecting the methane conversion and hydrogen yield. The stability and the lower amount of coking on promoted catalysts were attributed to partial coverage of the surface of nickel by patches of promoters and to their increased CO₂ adsorption, forming a surface reactive carbonate species. Addition of CeO₂ or MnO reduced the particle size of nickel, thus increasing Ni dispersion. For Ni–K/CeO₂–Al₂O₃ catalysts, the improved stability was further attributed to the oxidative properties of CeO₂. Results of the investigation suggest that stable Ni/Al₂O₃ catalysts for the carbon dioxide reforming of methane can be prepared by addition of both potassium and CeO₂ (or MnO) as promoters.     

Design of a novel bifunctional catalyst IrFe/Al2O3 for preferential CO oxidation

In this study, a novel bifunctional catalyst IrFe/Al₂O₃, which is very active and selective for preferential oxidation of CO under H₂-rich atmosphere, has been developed. When the molar ratio of Fe/Ir was 5/1, the IrFe/Al₂O₃ catalyst performed best, with CO conversion of 68% and oxygen selectivity towards CO₂ formation of 86.8% attained at 100 °C. It has also been found that the impregnation sequence of Ir and Fe species on the Al₂O₃ support had a remarkable effect on the catalytic performance; the activity decreased following the order of IrFe/Al₂O₃ > co-IrFe/Al₂O₃ > FeIr/Al₂O₃. The three catalysts were characterized by XRD, H₂-TPR, FT-IR and microcalorimetry. The results demonstrated that when Ir was supported on the pre-formed Fe/Al₂O₃, the resulting structure (IrFe/Al₂O₃) allowed more metallic Ir sites exposed on the surface and accessible for CO adsorption, while did not interfere with the O₂ activation on the FeO_x species. Thus, a bifunctional catalytic mechanism has been proposed where CO adsorbed on Ir sites and O₂ adsorbed on FeO_x sites; the reaction may take place at the interface of Ir and FeO_x or via a spill-over process.     

过氧化氢蒽醌加氢流化床Pd/Al_2O_3催化剂载体性质与催化性能的关系

以氯化钯为前驱体,活性氧化铝为载体,采用等体积浸渍法制备蒽醌加氢流化床Pd/Al_2O_3催化剂。考察载体比表面积、孔容、孔径、粒度分布及表面形貌与催化剂催化性能的关系,结果表明,载体比表面积较高,小孔径且孔径分布不均匀,粒度较大且粒度分布均匀,载体表面光滑且成球性好的载体对应的催化剂性能较好。采用优化后活性氧化铝载体制备的Pd/Al_2O_3催化剂的氢化效率和选择性分别为9.98 g·L-1和80.3%。