二氧化碳加氢直接合成二甲醚催化剂的研究进展

综述了CuO-ZnO-Al2O3/HZSM-5、CuO-ZnO-ZrO_2/HZSM-5、CuO-Fe2O3-ZrO_2/HZSM-5等催化剂、催化剂制备方法以及添加不同助剂对CO_2加氢直接合成二甲醚反应催化性能的影响,展望了CO_2加氢直接合成二甲醚催化剂未来的发展方向。     

浆态床合成二甲醚用CuZnAlSi催化剂的完全液相法制备及表征

采用完全液相法制备了不同SiO₂含量的二甲醚(DME)合成CuZnAlSi双功能催化剂,并在浆态床反应器中评价其催化反应活性,通过in-situ XPS、XRD、BET、NH₃-TPD等方法对其物理化学性能进行研究。结果表明,CuZnAl催化剂中加入SiO₂组分,能够促进活性组分Cu的分散,并通过与AlOOH的作用调变催化剂的孔结构和表面酸性,从而提高催化剂在DME合成反应中的活性。准原位 XPS表征结果显示,还原后的催化剂表面Cu⁰和ZnO共同构成DME合成反应中的甲醇合成活性中心。SiO₂的加入可能导致Cu、Zn和Al组分间的相互作用减弱,催化剂稳定性降低。     

二甲醚制备方法的研究进展

简述了二甲醚的性质、用途。介绍了实验室和工业制二甲醚的方法。详细阐述了甲醇法和以一氧化碳、氢气为原料的合成气制备二甲醚的工业制法，指出了每种方法的工艺特点和国内外的研究进展及发展前景。     

二甲醚催化剂活性评价方法研究

针对现有二甲醚催化剂活性评价系统分析方法的缺陷,在单柱分析的基础上,利用系统C、H、O的平衡,建立了色谱分析结果的计算方法,通过实践对比,证明该方法是可行的。     

二氧化碳与氢气合成二甲醚催化剂的研制

以二氧化碳为原料,加氢催化制甲醇和二甲醚具有重要的社会经济意义。研究采用CNJ202合成甲醇催化剂和HZSM－5沸石分子筛制得了二氧化碳加氢一步法合成甲醇及二甲醚双功能催化剂。实验测试结果表明,该催化剂合适的配比是HZSM－5／CNJ202＝0．5（wt/wt),合适的焙烧温度550℃,还原条件是在以N2为载气,2％H2气氛中,于250℃、常压下还原6h。催化剂粒度和不太大的操作空速变化对二甲醚选择性无明显影响,提高反应温度有利于增大二甲醚的选择性。测试显示,进一步改进双功能催化剂,可望大幅度提高CO2转化率,获得较高的生成二甲醚的选择性,为工业试验提供了依据。     

合成气一步法合成二甲醚催化剂的研究

采用共沉淀与浸渍相结合的方法制备出合成气直接合成二甲醚的双功能催化剂,其中活性组分主要有Cu、Zn、Mn、Al和Zr等,脱水剂主要有γ-Al2O3和HZSM-5分子筛。考察了不同脱水组分以及不同的引入方式和不同活性组分对催化剂性能的影响,经过对催化剂综合性能的评价,得到最佳催化剂活性组分质量比为CuO∶ZnO∶ZrO2=5∶4∶1,CO转化率为89.96%,二甲醚选择性为69.92%,收率为62.90%。     

还原胺化合成乙二胺催化剂的制备及表征

选择TiO2为载体,Cu和Re为助剂,采用浸渍法制备改性Ni-Co双金属催化剂,研究其在乙醇胺还原胺化合成乙二胺的应用,通过单2因素和正交设计实验确定催化剂制备的最佳条件:金属负载量10%,镍/钴比4,助剂含量2%,浸渍溶液pH为8。采用XRD和SEM-EDS技术对催化剂的晶型结构、表面微观形貌和元素含量进行表征。结果表明,Ni以分散的金属态存在,Co以氧化物的形式存在,催化剂表面粗糙,比表面积较大,金属含量适当,催化剂活性较好。     

二甲醚的制备及其应用

简述了重要的化工原料——二甲醚的性质、合成方法以及各方法的工艺特点，综述了二甲醚在燃料、气雾剂制冷剂和合成低碳和合成低碳烯烃等方面的应用，指出了二甲醚具有广阔的发展前景。     

合成二氧化氯的催化剂和方法及该催化剂的制备

使用一种失活速率降低的催化剂用亚氯酸钠的水溶液合成二氧化氮。催化剂最好为钯,钯与其它钯系金属的混合物（如Ｐｂ＋Ｐｔ）或者是钯与第１副族金属的混合物（Ｐｂ＋Ａｕ）,所用的载体为可用第１主族金属的硕酸盐如（Ｋ２ＣＯ３）、第２主族金属的碳酸盐（如ＣａＣＯ３）或者是可转化成ＭｇＯ的镁盐改性的物质,载体还可以是第１主族金属的碳酸盐（如Ｋ２ＣＯ３）或者是可转化成ＭｇＯ的镁盐改性的物质,载体还可以是第１主族金属     

Experimental study of improved two step synthesis for DME production

Dimethyl ether (DME) has received growing attention due to its potential use as a multi-purpose fuel. A new technical route of improved two step synthesis is proposed for DME production, which is composed of methanol synthesis and methanol dehydration in a fixed-bed reactor. The influences of the operating conditions including reaction pressure, temperature, H₂/CO mole ratio in the syngas and space velocity on CO conversion, selectivity and yield of DME are investigated. CO conversion and DME yield both increase monotonically with the pressure increase. The optimal reaction temperatures for the synthesis and dehydration of methanol are different. CO conversion increases at first and keeps constant when the H₂/CO mole ratio is above 2. DME yield increases obviously and then decreases gradually with the space velocity increase. The optimal conditions are obtained to maximize the CO conversion and DME selectivity. The reaction temperatures of the top and bottom stage are in the range of 270-280 °C and 235-245 °C, respectively. The optimal ratio of H₂/CO is above 2, and the space velocity is in the range of 1000-1300 h^− 1.     

甲醇制二甲醚用铝基催化剂的制备及其性能研究

研制出以氧化铝为载体的催化剂Ａ以及添加第ＩＶ副族元素的催化剂Ａ＋Ｂ,并与ＨＺＳＭ－５催化剂进行了活性对比。催化剂Ａ经１０００ｈ原粒度测试,结果表明：在反应温度３００℃,空速４．２５～４．５０ｈ－１,压力为常压的条件下,二甲醚选择性＞９９％,甲醇转化率≥８０％。     

Catalytic dehydration of methanol to dimethyl ether (DME) over Al-HMS catalysts

A series of Al-HMS with different Si/Al ratio was used as a solid acid catalyst for methanol dehydration to dimethyl ether (DME). The effect of temperature, feed composition, space velocity, and the catalyst Si/Al ratio on the catalytic dehydration of methanol was investigated. By decreasing Si/Al, the temperature required to reach equilibrium conversion of methanol decreased due to the increased number of acidic sites. Compared to commercial γ-Al₂O₃, Al-HMS-5 and Al-HMS-10, catalysts exhibited a high yield of DME. Among all Al-HMS catalysts, Al-HMS-10 exhibited an optimum yield of 89% with 100% selectivity and excellent stability for methanol dehydration to DME.     

Fischer-Tropsch synthesis and the generation of DME in situ

Ternary physical mixtures comprised a Fischer-Tropsch catalyst, a methanol synthesis catalyst and a zeolite employed in the hydrocarbon synthesis from syngas. Two Fe-based catalysts (i.e., one promoted by K and the other by Ru), two HY zeolites with different acidities, a commercial HZSM-5 and Cu/ZnO/Al₂O₃ (methanol synthesis catalyst) were used in these systems. The main products obtained were dimethyl ether, methanol and hydrocarbons. First of all, it was observed that by adding Cu/ZnO/Al₂O₃ catalyst to a binary physical mixture comprised of a Fischer-Tropsch catalyst and HZSM-5, the CO conversion increases more than 20 times. Second, during the reaction transient period the dimethyl ether selectivity decreases as the conversion increases. Third, the hydrocarbons synthesized followed the ASF distribution in the C₁-C₁₂ range and finally, it was also verified that the Y zeolites and the Fischer-Tropsch synthesis catalyst promoted by Ru generated the most active physical mixtures. The results showed that the role of zeolites in the ternary physical mixture is only associated with the dimethyl ether synthesis. The following reaction pathway was suggested: first, methanol is synthesized from syngas using Cu/ZnO/Al₂O₃ catalyst; after that, this alcohol is dehydrated by an acid catalyst generating DME; and lastly, DME initiates Fischer-Tropsch synthesis, which is then propagated by CO.     

Characterization of bimetallic rhodium-germanium catalysts prepared by surface redox reaction

The preparation of bimetallic rhodium-germanium/silica and rhodium-germanium/alumina catalysts was investigated by controlled surface reaction. Their catalytic performances were measured for two gas phase reactions (toluene hydrogenation at 323 K and cyclohexane dehydrogenation at 543 K) and for a liquid phase reaction (citral hydrogenation at 343 K).

Elemental analysis of bimetallic catalysts showed that germanium can be deposited by redox reaction between hydrogen activated on a parent monometallic rhodium catalyst and germanium tetrachloride dissolved in water (catalytic reduction method). EDX microanalysis of rhodium-germanium/silica catalysts indicated that rhodium and germanium were deposited in close contact on the silica support. However, on alumina-supported catalysts, germanium deposition occurred also separately on the support. For the different test reactions, the catalytic properties of rhodium were strongly altered by the addition of germanium. On alumina-supported catalysts, interesting catalytic effects were observed in citral hydrogenation when not only close contact exists between both metals but when, in addition, the second metal was deposited on the support in the close vicinity of rhodium.     

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。     

Methane aromatization using Mo-based catalysts prepared by microwave heating

Mo/HZSM-5 and Cu–Mo/HZSM-5 catalysts for the non-oxidative aromatization of methane have been prepared by microwave heating method. The effects of Mo loading, the molar ratio of Cu/Mo and preparation method on the catalytic performance of catalysts were studied. The results were compared with those for the methane aromatization over catalysts prepared by conventional heating. Both two kinds of catalysts have the maximum methane conversion when the Mo loading is 6%. The catalysts prepared by microwave heating exhibited higher selectivity to benzene than that prepared by conventional heating. The addition of metal Cu to Mo/HZSM-5 catalyst prepared by microwave heating enhanced the lifetime of catalyst, and gave rise to a little increase in methane conversion. The molar ratio of Cu/Mo influenced the methane conversion, and the maximum value was attained when Cu/Mo = 0.05, whereas no significant influence on the benzene selectivity was observed with the increase molar ratio of Cu/Mo. N₂ adsorption results showed that the catalysts prepared by microwave heating have the larger surface area and the similar pore volume compared with the catalysts prepared by conventional heating. This fact revealed that the more Mo species located on the outer surface of catalysts prepared by microwave heating is the main reason why they have better catalytic performance. XRD analysis indicated that the Mo species are highly dispersed on HZSM-5 zeolite. The addition of Cu influenced the dispersion. The actual active phase Mo₂C can be identified on the catalyst surface after reaction. TEM analysis revealed the carbonaceous deposition to have the form of carbon nanotube after reaction, with a uniform size range of 10–20 nm. TG analysis indicated that carbonaceous deposition on the catalysts prepared by microwave heating is lower than that by conventional heating, and the metal Cu further prompts the stability of catalyst. Most of the carbonaceous deposition on catalysts prepared by microwave heating is formed at low temperature and it is easy to burn-off. Coke accumulation at high temperature is the main reason of catalyst deactivation. The carbonaceous deposition formed on the catalysts for non-oxidative aromatization of methane is different from those formed on the catalysts for partial oxidation of methane.     

不同制备工艺的铜基合成甲醇催化剂的性能及结构

探讨不同制备工艺条件对Cu基合成甲醇催化剂性能的影响。分别采用反加共沉淀法、反加共沉淀法+助剂、并流法和并流法+助剂制备了4种催化剂样品,考察催化剂性能的变化,并对助剂在催化剂合成过程中所起的作用进行推测,采用X射线衍射、低温N₂吸附和扫描电子显微镜等对催化剂进行表征。结果表明,Cu基甲醇合成催化剂制备过程中加入助剂可以调整催化剂的孔径分布和表面组分分布,催化剂组成确定后,催化剂制备过程采用并流法+助剂制备的样品,孔径分布更合理,ZnO组分晶粒尺寸较小,Cu和Zn组分间相互接触的几率更大,催化剂性能更好。     

Effect of preparation methods on the performance of CeO2/Al2O3 catalysts for selective catalytic reduction of NO with NH3

CeO₂/Al₂O₃ catalysts prepared by three methods were investigated for selective reduction of NO with NH₃. It was found that the catalyst prepared by the single step sol–gel method had the best SCR activity and SO₂ resistance performance. From the results of BET, XRD, TPD and TPR, it can be concluded that large surface area, strong interaction, highly dispersed nano-crystalline ceria, high NH₃ adsorption capacity and good redox ability might be the main reasons for the excellent performance of CeO₂/Al₂O₃ catalyst prepared by the single step sol–gel method.     

Dimethyl ether conversion to light olefins over the SAPO-34/ZrO2 composite catalysts with high lifetime

The SAPO-34/ZrO₂ composite catalysts using ZrO₂ as a binder were prepared and their performance was investigated for the dimethyl ether to olefins (DTO) reaction. The composite catalysts showed higher catalytic lifetimes than the free SAPO-34 catalyst, while maintaining high selectivity toward light olefins. This suggests that the binder-filled space between the SAPO-34 crystals can provide additional diffusion paths for mass transfer. In the SAPO-34/ZrO₂ composite catalysts with different ZrO₂ contents, the SAPO-34(11 wt%)/ZrO₂ composite catalyst showed the highest catalytic lifetime. It can be concluded that ZrO₂ is one of the best binders for the preparation of SAPO-34/binder composite catalysts.