预处理对Ru/Al_2O_3催化马来酸二甲酯加氢影响

采用吸附-沉淀法制备负载Ru质量分数为1.0%的Ru/Al_2O_3催化剂,以马来酸二甲酯催化加氢合成丁二酸二甲酯为探针反应,详细考察预处理条件对Ru/Al_2O_3催化剂加氢性能的影响,并对其进行XRD、TEM和H2-TPR表征。结果表明,焙烧温度越高,催化剂催化活性越低;直接还原活化所得催化剂活性高于空气中焙烧后还原活化所得催化剂。以甲醇为溶剂,在70℃和1.0 MPa条件下,直接还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率达100%,丁二酸二甲酯选择性约100%。相同时间内,空气焙烧后还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率接近25%,继续延长反应时间,马来酸二甲酯转化率几乎不变。经高温焙烧还原后,活性组分Ru烧结;直接还原活化后,活性组分Ru高度分散。     

4-甲氧基环己酮的绿色合成

在Al_2O_3负载的镍基纳米催化剂作用下进行了4-甲氧基苯酚催化加氢反应,然后使用双氧水对加氢反应液进行催化氧化合成4-甲氧基环己酮。在催化加氢反应中,考察了沉积-沉淀法和浸渍法及反应条件对催化剂活性和稳定性的影响。通过XRD、H_2-程序升温还原(H_2-TPR)及TEM等对催化剂进行了表征,结果发现,沉积-沉淀法制备的Ni/Al_2O_3-DP催化剂中活性粒子分散度高、粒径较小,并且活性粒子与载体之间有较强的作用力,具有比浸渍法制备的Ni/Al_2O_3-IMP催化剂更好的活性和稳定性。在4-甲氧基苯酚的加氢反应中,以Ni/Al_2O_3-DP为催化剂,最佳的反应条件为:反应温度423 K、反应压力4.0 MPa、反应时间1.0 h、m(4-甲氧基苯酚)∶m(Ni/Al_2O_3-DP)=6∶1。在氧化反应中,探究了氧化条件对反应活性的影响,结果表明:当n(4-甲氧基环己醇)∶n(双氧水)=1.0∶2.5时,353 K反应20 h,目标产物4-甲氧基环己酮的选择性可达95.3%。     

Fe修饰Mn-Ce/Al2O3-TiO2催化剂对NO氧化性能的实验研究

采用溶胶凝胶法制备了TiO_2与Al_2O_3摩尔比为1∶4的Al_2O_3-TiO_2复合氧化物载体,使用共浸渍法制备了Mn,Ce质量分数分别为10%和2%的Mn-Ce/Al_2O_3-TiO_2催化剂,并通过添加不同质量分数的Fe对催化剂进行修饰。在固定床反应装置上进行了催化剂氧化性能的实验。结果表明:在空速为15 000 h~(-1),氧气体积分数为8%时,Fe的添加能够显著提升Mn-Ce/Al_2O_3-TiO_2催化剂的NO催化氧化性能,并在Fe质量分数为4%时,Mn-Ce-Fe(4)/Al_2O_3-TiO_2催化剂的NO催化氧化活性最优,280℃时NO的转化率达到86%。H_2-TPR实验结果显示,Fe的修饰使Mn-Ce/Al_2O_3-TiO_2催化剂的还原峰大幅向低温方向移动,改善了催化剂的氧化还原活性。     

α-蒎烯催化加氢催化剂制备及催化性能

采用溶胶-凝胶法制备了Al_2O_3、ZrO_2和ZrO_2/Al_2O_3载体,采用浸渍法制备了NiO/Al_2O_3、NiO/ZrO_2和NiO/ZrO_2/Al_2O_3催化剂,采用H_2-TPR、NH_3-TPD和原位红外等技术对催化剂的还原性能、表面酸特性、α-蒎烯的吸附性及比表面积等进行了表征。结果表明,负载型ZrO_2/Al_2O_3复合载体与活性物种形成较强的相互作用,稳定活性中心,复合载体Ni催化剂表面酸强度介于Ni/ZrO_2和Ni/Al_2O_3之间,α-蒎烯能与Ni/ZrO_2/Al_2O_3催化剂形成适宜化学吸附态。在α-蒎烯加氢反应中,Ni/ZrO_2/Al_2O_3催化剂表现出较好的催化活性和选择性,α-蒎烯转化率为84%,蒎烷选择性为83%。     

Ni-B/Al2O3催化1-辛炔选择性加氢反应

采用硼氢化钾还原方法制备了Ni-B/Al_2O_3催化剂,并与传统高温加氢还原法制备的Ni/Al_2O_3催化剂进行对比。通过X射线衍射(XRD)、透射电子显微镜(TEM)、氢气程序升温还原(H2-TPR)、紫外-可见漫反射光谱(UV-vis DRS)及X射线光电子能谱(XPS)等方法对催化剂结构和性质进行表征,并对催化剂进行1-辛炔加氢性能考评。结果表明,由于硼氢化钾还原能力较弱,Ni-B/Al_2O_3催化剂表面Ni0含量小于氢气还原的催化剂,但是其活性金属粒径更小,因而加氢反应活性仍与Ni/Al_2O_3相近。此外,Ni-B/Al_2O_3催化剂中Ni处于富电子状态,减弱了1-辛烯的吸附,显著提高了1-辛烯选择性。在1-辛炔转化率为99%时,1-辛烯选择性仍高达91%。     

改性Al2O3负载Ru催化剂制备及1,4-丁炔二醇加氢性能

采用炭改性Al_2O_3(CCA)为载体,通过吸附-沉淀法制备Ru/CCA催化剂,以1,4-丁炔二醇加氢制1,4-丁二醇为探针反应,考察Ru/CAA催化剂的加氢性能,并对催化剂进行XRD和H2-TPR表征。活性评价结果表明,在110℃和4.0 MPa条件下,Ru/CAA催化剂上1,4-丁炔二醇转化率100%,1,4-丁二醇选择性88%。表征结果表明,采用炭改性可提高催化剂的水热稳定性,同时炭的加入还增强了活性组分与载体的相互作用。     

浸渍-水热制备方法对Ni/Al_2O_3催化剂结构和性能的影响

活性组分与载体之间的相互作用能够影响催化剂的催化性能。浸渍法是最常规的催化剂制备方法,本文通过对浸渍之后的催化剂前驱体进行水热处理,改善了浸渍法制备的Ni/Al_2O_3催化剂上Ni粒子与Al_2O_3之间的相互作用,从而改善了催化剂的催化性能。通过XRD和H_2-TPR表征发现,水热处理4h制得的Ni/Al_2O_3-4催化剂上,Ni与Al_2O_3之间的相互作用强度适中,Ni-Al合金的衍射峰强度最低,活性组分Ni的衍射峰最为弥散,该催化剂在甲烷干重整具有最高的催化性能。     

改性Ni/Al_2O_3催化蒽醌加氢反应的研究

以Al_2O_3为载体,La、Ce或Zr为改性剂,Ni作为活性组分,制备了一系列改性的Ni/Al_2O_3催化剂,并通过蒽醌加氢反应系统地评价了催化剂的反应活性,发现La、Ce改性的催化剂,其加氢活性得到显著的增加。活性最好的催化剂为La_5-Ni_(40)/Al_2O_3,氢效为3.96g·L~(-1)。采用XRD、H_2-TPR、BET等方法对La_5-Ni_(40)/Al_2O_3的表面结构进行了一定的表征分析,发现加入La元素能促进活性组分Ni的分散,提升了其加氢性能。实验得出催化剂的最佳焙烧温度和还原温度分别为600℃和550℃,既保证了催化剂具有适当的孔道结构,同时也改善了活性组分Ni的分散度。     

Ru/Al_2O_3催化剂上邻苯二甲酸二丁酯加氢合成1,2-环己烷二甲酸二丁酯

以浸渍法制备Ru/Al2O3催化剂,研究在高压反应釜中Ru/Al2O3上催化加氢邻苯二甲酸二丁酯(DBP)合成1,2-环己烷二甲酸二丁酯(CDADE)。采用X射线衍射(XRD)、H2程序升温还原(H2-TPR)、扫描电镜(SEM)、X射线能谱仪(EDS)和透射电子显微镜(TEM)对催化剂进行表征。结果表明,Ru负载量为3.0%(质量分数),200℃氢气气氛中还原的Ru/Al2O3催化剂,在催化DBP合成CDADE的反应中具有较高的催化活性。在反应温度80℃、反应压力2.0~2.5 MPa和搅拌转速800 r/min下,DBP转化率和CDADE选择性分别达到99.972%和99.904%,催化剂重复使用9次后仍有较高活性,但继续使用,由于活性组分Ru部分流失、团聚和催化剂表面积炭,催化剂活性有所下降。     

Ru/TiO_2催化剂制备及其在有机酸废水湿式氧化中的应用

以纳米TiO_2为载体,通过优化制备方法,合成了高活性的Ru/TiO_2贵金属催化剂,采用X射线衍射(XRD)、N_2物理吸附、程序升温还原(H_2-TPR)和透射电镜(TEM)等手段对催化剂进行表征,并将制备的催化剂应用到湿式氧化处理3种有机酸模拟废水中。研究表明,氢气还原有助于Ru在TiO_2表面的分散,由此制备的催化剂氧化活性较高。在200℃,初始氧压3 MPa的条件下反应2 h,Ru/TiO_2在湿式氧化处理丙烯酸、丁二酸和乙酸有机酸模拟废水时,化学需氧量(COD)去除率分别达到95.3%,91.6%和70.1%。     

Activity enhancement of SnO2-doped Ga2O3–Al2O3 catalysts by coexisting H2O for the selective reduction of NO with propene

Catalytic reduction of NO by propene in the presence of oxygen was studied over SnO₂-doped Ga₂O₃–Al₂O₃ prepared by sol–gel method. Although SnO₂-doped Ga₂O₃–Al₂O₃ gave lower NO conversion than Ga₂O₃–Al₂O₃ in the absence of H₂O, the activity was enhanced considerably by the presence of H₂O and much higher than that of Ga₂O₃–Al₂O₃. The presence of SnO₂ and Ga₂O₃–Al₂O₃ species having intimate Ga–O–Al bondings was found to be essential for the promotional effect of H₂O. The promotional effect of H₂O was interpreted by the following two reasons. The first one is the removal of carbonaceous materials deposited on the catalyst surface by H₂O. The other is the selective inhibition by H₂O of the reaction steps resulting in propene oxidation to CO_x without reducing NO.     

Enhanced activity of metal oxide-doped Ga2O3–Al2O3 for NO reduction by propene

Effect of additives, In₂O₃, SnO₂, CoO, CuO and Ag, on the catalytic performance of Ga₂O₃–Al₂O₃ prepared by sol–gel method for the selective reduction of NO with propene in the presence of oxygen was studied. As for the reaction in the absence of H₂O, CoO, CuO and Ag showed good additive effect. When H₂O was added to the reaction gas, the activity of CoO-, CuO- and Ag-doped Ga₂O₃–Al₂O₃ was depressed considerably, while an intensifying effect of H₂O was observed for In₂O₃- and SnO₂-doped Ga₂O₃–Al₂O₃. Of several metal oxide additives, In₂O₃-doped Ga₂O₃–Al₂O₃ showed the highest activity for NO reduction by propene in the presence of H₂O. Kinetic studies on NO reduction over In₂O₃–Ga₂O₃–Al₂O₃ revealed that the rate-determining step in the absence of H₂O is the reaction of NO₂ formed on Ga₂O₃–Al₂O₃ with C₃H₆-derived species, whereas that in the presence of H₂O is the formation of C₃H₆-derived species. We presumed the reason for the promotional effect of H₂O as follows: the rate for the formation of C₃H₆-derived species in the presence of H₂O is sufficiently fast compared with that for the reaction of NO₂ with C₃H₆-derived species in the absence of H₂O. Although the retarding effect of SO₂ on the activity was observed for all of the catalysts, SnO₂–Ga₂O₃–Al₂O₃ showed still relatively high activity in the lower temperature region.     

Ce和La改性固体超强酸S2O82-/ZrO2-SiO2催化剂合成及其酯化性能研究

以Zr(NO₃)₄·5H₂O和Na₂SiO₃·9H₂O为原料,利用共沉淀法制备前驱体,浸渍添加稀土Ce和La,一定温度焙烧后制得掺杂稀土S₂O₈^2-/ZrO₂-SiO₂固体超强酸。通过XRD、FT-IR和SEM对催化剂进行表征,以硬脂酸的酯化合成反应为探针,考察制备条件对催化剂性能的影响以及催化剂的重复使用率。结果表明,相对于未改性的S₂O₈^2-/ZrO₂-SiO₂催化剂,添加了Ce或La的固体超强酸酯化催化活性及重复使用性能均有提高。     

In-situ growth of needlelike LaAl11O18 for reinforcement of alumina composites

In situ growth of needlelike LaAl₁₁O₁₈ grains reinforcing Al₂O₃ composites can be fabricated by a coprecipitation method using La(NO₃)₃√6H₂O and Al(NO₃)₃√9H₂O as starting materials. The new two-step process involved firstly preparing needlelike LaAl₁₁O₁₈ grains distributed homogeneously in Al₂O₃ powder and then pressureless sintering the composite powders. The Al₂O₃/25 vol.%LaAl₁₁O₁₈ samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m^1/2.     

Pt/Al_2O_3与Pt/MgO-Al_2O_3催化剂制备及其催化氢能载体甲基环己烷脱氢反应性能

以碱共沉淀法制备Mg-Al水滑石,然后采用浸渍法负载活性组分Pt,经焙烧、氢气还原得到Pt/Al_2O_3与Pt/Mg O-Al_2O_3催化剂,采用XRD、N2吸附-脱附、FT-IR、H2-TPR和Py-IR等分析Mg O的加入对Pt/Al_2O_3催化剂结构性能的影响,并在甲基环己烷连续脱氢反应中对比两种催化剂活性。结果表明,Pt/Mg O-Al_2O_3催化剂比表面积小于Pt/Al_2O_3催化剂,且表面基本无酸性活性中心,但表现出与Pt/Al_2O_3催化剂相同的脱氢活性。在Pt负载质量分数2%、催化剂用量0.5 g、甲基环己烷0.1 m L·min-1纯样进料和325℃反应10 h后,原料平均转化率79.9%,脱氢产物只有甲苯,对应的产氢速率192.8 mmol·(g-metal·min)-1,表现出优良的脱氢活性。     

Cu2O催化甲醛乙炔化反应助剂效应

在液相还原法制备的纯Cu2O样品中,采用浸渍法分别引入Mg、Al、Fe助剂制备Cu2O-MgO、Cu2O-Al2O3、Cu2O-Fe2O3催化剂。采用XRD、FT-IR、TEM和H2-TPR等对催化剂进行表征,研究不同助剂的加入对甲醛乙炔化反应的影响。结果表明,不同助剂对催化剂的结晶度和可还原性能有较大影响,进而使甲醛乙炔化表现出不同的催化活性。相比MgO与Al2O3,Fe2O3的引入,使Cu2O结晶度明显下降,主要是由于Fe2O3与Cu2O之间产生强的相互作用,有利于乙炔亚铜活性物种的形成,从而表现出最优的催化性能。     

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.     

Superior performance of Ir-substituted hexaaluminate catalysts for N2O decomposition

Novel Ir-substituted hexaaluminate catalysts were developed for the first time and used for catalytic decomposition of high concentration of N₂O. The catalysts were prepared by one-pot precipitation and characterized by X-ray diffraction (XRD), N₂-adsorption, scanning electronic microscopy (SEM) and temperature-programmed reduction (H₂-TPR). The XRD results showed that only a limited amount of iridium was incorporated into the hexaaluminate lattice by substituting Al³⁺ to form BaIr_xFe_1−xAl₁₁O₁₉ after being calcined at 1200 °C, while the other part of iridium existed as IrO₂ phase. The activity tests for high concentration (30%, v/v) of N₂O decomposition demonstrated that the BaIr_xFe_1−xAl₁₁O₁₉ hexaaluminates exhibited much higher activities and stabilities than the Ir/Al₂O₃-1200, and the pre-reduction with H₂ was essential for activating the catalysts. By comparing BaIr_xFe_1−xAl₁₁O₁₉ with BaIr_xAl_12−xO₁₉ (x = 0–0.8), it was found that iridium was the active component in the N₂O decomposition and the framework iridium was more active than the large IrO₂ particles. On the other hand, Fe facilitated the formation of hexaaluminate as well as the incorporation of iridium into the framework.