预处理方法对Ru/SBA-15催化丙三醇氢解反应性能的影响(英)

使用浸渍法结合不同预处理方法制备了一系列的Ru/SBA-15催化剂,并将其应用于丙三醇氢解反应中.使用N_2吸附-脱附、X射线衍射、CO化学吸附以及透射电子显微镜等方法对所制备Ru/SBA-15进行了表征.结果表明,催化剂前驱体经过空气焙烧后再经H_2还原的Ru/SBA-15催化剂上Ru的分散度较低,而直接使用H_2处理较高.同时,随着H_2还原温度提高,Ru分散度逐渐降低.保持反应活性接近时,随着Ru分散度的降低,TOF增加.表明Ru/SBA-15催化剂上丙三醇氢解是结构敏感反应.     

Ru添加对Co/SiO2费托合成催化剂性能的影响

用初湿含浸法制备了不同Ru添加量的Co/SiO₂模型催化剂,然后进行N₂物理吸附、XRD、H₂-TPD、DRIFTS等表征和微分固定床费托(F-T)反应评价。F-T反应结果表明,催化剂中添加Ru后,CO转化率显著提高,TOF值增大,CO₂和CH₄选择性降低,烯/烷比(O/P)降低。FT-IR表征说明,催化剂添加Ru后Co-O键的强度减弱,相对应的H₂-TPR也表明,催化剂的还原度得到显著提高。还原后的催化剂XRD结果进一步证实,加入Ru后,催化剂无钴氧化物被检出,并且当Ru添加量为0.5%(质量分数)时催化剂中金属钴主要以六方密堆(hcp)形式存在。CO-DRIFTS结果显示,Ru的加入使CO的吸收峰发生红移,即Ru促进了CO的解离。H₂-TPD结果则表明,随着Ru添加量的增加,催化剂表面CO_ads/Co_s和CO^*/Co_s增大,这是CH₄选择性降低的主要原因。     

载体效应对Ru催化剂F-T反应性能的影响

采用浸渍法将Ru负载于SiO₂、Al₂O₃和Beta分子筛制备了不同载体的Ru基F-T合成催化剂。通过N₂-物理吸附、XRD、NH₃-TPD、H₂-TPR、H₂-TPD、XPS和CO-DRIFTS等表征方法对不同催化剂的织构、物相、酸性、还原性质、吸附性能和电子状态信息进行了考察,并对不同载体催化剂的F-T反应性能及产物分布进行了研究。结果表明,不同载体Ru基催化剂在金属分散度、还原性质、对氢气吸附性能和电子状态等方面均存在较大差异。其中,酸性较弱的Ru/SiO₂催化剂具有较弱的金属载体相互作用、较小的颗粒粒径和较高的电子密度,同时该催化剂的Ru金属平台位点较多,导致其在F-T反应过程中表现较好的反应稳定性,其产物以重质烃为主,CH₄和轻质烃选择性较低。     

等离子体技术对CO2甲烷化用Ni/SiO2催化剂的改性作用

采用浸渍法制备了Ni/SiO₂催化剂,应用等离子体技术对催化剂进行改性处理。以CO₂甲烷化为模型反应对催化剂进行活性评价,通过H₂程序升温还原(H₂-TPR)和CO₂程序升温脱附(CO₂-TPD)技术对催化剂进行表征。研究了等离子体技术强化处理对催化剂吸附性能和还原性能的影响。结果表明,与常规焙烧的催化剂相比,等离子体技术改性处理提高了催化剂活性组分的分散度,增加反应活性位并调变了活性位对吸附物种的吸附强度,改进了催化剂的还原性能,CO₂甲烷化反应活性和甲烷的时空产率显著提高。     

金复合介孔SBA-15吸附血红蛋白在H2O2电催化反应中的应用

以P123嵌段共聚物表面活性剂为模板剂制备介孔氧化硅SBA-15,并用沉积-沉淀(DP)法在SBA-15介孔表面负载纳米Au颗粒制备得到金复合介孔SBA-15材料(Au-SBA-15).再以Au-SBA-15材料制备玻碳修饰电极,将血红蛋白固定于修饰电极上用循环伏安法考察其对不同浓度H₂O₂溶液的电催化反应.在固定了血红蛋白的Hb/Au-SBA-15/GC修饰电极上,H₂O₂在+0.95 V处出现了氧化峰,且随着H₂O₂浓度的增大峰电流不断增加,说明金复合介孔氧化硅材料具有良好的生物兼容性,有利于血红蛋白的固定,其修饰电极对H₂O₂溶液具有一定的电催化作用.     

利用原位红外光谱确证Ru/SBA-15的加氢活性位点

Ru/SBA-15催化剂具有高的氢气活化能力,因此被广泛应用在加氢和氢解反应中.一般认为Ru/SBA-15催化剂的高活性与金属Ru的高分散有关,然而有研究发现在氧化硅载体上还存在溢流的氢,这部分溢流氢也很可能参与加氢和氢解反应.这就产生了两个关键性的问题:(1)Ru/SBA-15的催化加氢活性中心是什么,是金属Ru还是载体SBA-15;(2)在金属Ru上解离的H是如何迁移到载体上的.因此,加氢活性位点及其形成机理的确认对理解Ru/SBA-15催化剂的高活性至关重要.原位红外光谱可从分子层面研究在工作状态的催化剂表面活性位点的状态,进而推测可能的反应机理.通过与催化剂Pd/SBA-15,Ru/Al2O3和SBA-15比较发现,在氢气氛围中Ru/SBA-15催化剂的原位红外谱图中存在一个独特的位于1996 cm?1的峰.由于在Pd/SBA-15,Ru/Al2O3和SBA-15上都不存在这个峰,因此该峰的形成是金属Ru和SBA-15相互作用的结果.此外,Si–O键在位于1866 cm?1的合频峰不随氢气氛围变化而变化,因此可排除这个峰属于Si–O键振动的倍频峰.为了排除该峰的产生是由于CO的吸附,我们采用脉冲引入CO的方法,发现在低的CO覆盖率下,红外谱图中位于2068 cm?1处出现了一个CO在Ruδ+上的线性吸附峰.随着CO覆盖率增加,该峰逐渐蓝移至2075 cm?1,同时位于2132 cm?1处的峰强度增强了,这两个峰都归属于Run+(CO)x物种的振动峰.这些CO的化学吸附强度都很高,即使在He气中吹扫1 h后仍然存在,而1996 cm?1峰的形成是可逆的.此外,低CO覆盖率下生成的吸附峰(2068 cm?1)的强度低于1996 cm?1峰的强度,因此可以排除1996 cm?1峰属于CO吸附峰的可能.既然1996 cm?1峰的形成是可逆的,将这个峰归属于载体上氢的可能性也可排除,因为形成载体上氢的过程是不可逆的.另外,形成1996 cm?1峰的速率还证明了这个峰不属于金属Ru上吸附的氢,因为金属Ru上氢的吸附是很快的.通过以上分析,我们推断1996 cm?1峰应该指认为在Ru和SBA-15界面处位点的红外峰.为了证明这一点,我们制备了不同Ru负载量的Ru/SBA-15催化剂,发现这个界面处位点峰的峰面积与金属Ru颗粒在载体上形成交界面的周长成正比,而峰达到稳态所需时间与Ru颗粒大小成反比.这说明H2在金属Ru上发生解离吸附后迁移到Ru和SBA-15界面处,形成了Ru–H–Si物种.当金属Ru的颗粒比较小时,与载体形成交界面的周长小,Ru–H–Si物种的数量少,体现在红外谱图上峰的峰面积小,但解离的氢迁移到该界面所需时间变短了.当金属Ru的颗粒比较大时,与载体形成交界面的周长大,Ru–H–Si物种的数量多,1996 cm?1峰的峰面积大,但解离氢的迁移慢了.此外,H-D交换实验还证明这个界面处的位点具有加氢活性.与文献报道的孤立Si–H物种的红外峰位置比较发现,Ru–H–Si物种具有明显的峰红移现象,说明该物种中的Si–H键活性很高,这可能是由于金属Ru将电子转移至Si–H键的结果.总之,以上结果清晰地表明这个1996 cm?1峰归属为结构是Ru–H–Si的活性位点.     

Ga对0.3Ga-WOx/SBA-15催化顺式-环辛烯环氧化的促进作用(英文)

本工作研究了镓(Ga)对Ga-WO_x/SBA-15催化H₂O₂与顺式-环辛烯环氧化反应活性的促进作用。最佳催化剂0.3Ga-WO_x/SBA-15的TOF为112 h^-1，是WO_x/SBA-15(57 h^-1)的近两倍。相较于WO_x/SBA-15(64.0 kJ/mol),0.3Ga-WO_x/SBA-15的低表观反应活化能(49.6 kJ/mol)与其优异的环氧化性能一致。动力学分析表明，H₂O₂在0.3Ga-WO_x/SBA-15表面上的吸附更强，这有助于H₂O₂的活化。基于催化剂的表征和环氧化的性能表明，Ga添加剂的提升作用归因于Lewis酸位点的增加和亲电性的增强。此外，金属过氧化氢(M-OOH)被鉴定为主要中间体。     

SBA-15负载钒氧化物催化剂上甲烷选择氧化反应

对SBA-15负载的钒、钼、钨氧化物催化的甲烷选择氧化反应性能进行了比较,发现VO_x/SBA-15催化剂优于MoOx/SBA-15和WOx/SBA-15催化剂.针对钒氧化物催化剂,考察了不同钒源、不同载体以及少量P元素的添加对催化性能的影响,结果表明以SBA-15为载体的催化剂的性能好于MCM-41和Cab-O-Sil为载体的催化剂;与V₂O₅,VO(C₂O₄)相比,NH₄VO₃是制备性能良好的VO_x/SBA-15的钒源;在VO_x/SBA-15中,添加少量P元素后,HCHO的选择性有一定程度的提高.XRD,N₂物理吸附、UN-Raman和H₂-TPR表征结果表明,负载量低于3 wt%时,钒组分可能主要以高分散的单核的VO_x物种存在,我们推测该物种对甲烷选择氧化制甲醛起关键作用.     

Ru-Re/SiO2催化剂上丙三醇氢解制丙二醇:催化剂的酸性质与Re组分的作用

考察了Ru-Re/SiO2 组分催化剂的酸性质,并探讨了Re组分在丙三醇氢解制丙二醇反应中对提高该催化剂性能所起的作用.本文采用氨气程序升温脱附法和吸附吡啶原位红外光谱法表征了双组分Ru.Re/SiO2和单组分Ru/SiO2、Re/SiO2催化剂的酸性质,并比较了催化剂在丙三醇氢解反应中的催化性能.结果显示,Ru-Re...     

镁铝复合氧化物负载铜催化剂上甘油选择性氢解合成丙二醇

我们通过乙醇溶液浸渍法合成出了具有高分散度金属Cu 的Cu/MgO-Al₂O₃ (Mg/Al 原子比=1/1, 3/1, 4/1)、Cu/MgO 和Cu/Al₂O₃ 等催化剂. 在200℃, 6.0 MPa H₂ 和二氧六环溶剂中, 这些催化剂高选择性地将甘油氢解为1,2-丙二醇(选择性>90%), 而单位表面Cu 原子的甘油转化速率则随催化剂表面碱中心与Cu 原子比例的提高而增大. N₂O 化学吸附-H₂ 程序升温还原实验表明Cu 粒子的本征氢解能力不随其负载量以及载体中的Mg/Al 原子比发生明显改变, 加之碱性MgO-Al₂O₃ 载体本身不催化甘油的转化, 我们推测在甘油氢解反应中金属Cu 粒子与载体界面处的碱中心辅助Cu 粒子活化甘油分子的α 位C-H键, 从而加速甘油脱氢为甘油醛步骤以及甘油氢解反应的进行. CO₂程序升温脱附实验以及对甘油氢解反应中Cu/MgO-Al₂O₃ 催化剂稳定性的考察结果暗示在甘油氢解反应中起主要作用的碱中心是载体表面上与Mg²⁺键连的羟基基团(即B 碱OH^-). 这些对甘油氢解反应中金属中心与碱性中心协同作用的认识对进一步理性设计高效的甘油或其它多元醇分子氢解催化剂具有重要指导意义.     

Hydrogenolysis of glycerol to propanediols over supported Ag–Cu catalysts

Hydrogenolysis of glycerol to 1,2-propanediol and 1,3-propanediol has significant scientific importance and commercial interest due to the huge surplus of glycerol and the various application of propanediols. A series of supported Ag–Cu catalysts synthesized by impregnation method were studied for hydrogenolysis of glycerol to propanediols. The catalysts were characterized by H₂-TPR, NH₃-TPD, XRD, BET, N₂O chemisorption, TG, ICP and SEM. It was observed that the loading of 5% Ag–Cu-based catalysts facilitated the reduction, surface acidity and dispersion of the Cu particles, which improved the conversion of glycerol and promoted the generation of propanediols. It was also found that when loading Ag and Cu simultaneously on Al₂O₃, the catalyst had a better performance for the reaction because of the higher acidity, dispersion and surface area of the Cu species on the catalyst surface. In addition, effects of metal concentrations, metal impregnation sequence, reaction temperature, reaction pressure, reaction time, solvent and pH value of the solution on glycerol hydrogenolysis together with the recyclability of catalyst were investigated in detail. The optimal 5Ag–15Cu/Al₂O₃ achieved 66.4% glycerol conversion with 68.2% 1,2-propanediol and 3.1% 1,3-propanediol selectivity at 200 °C under 3.5 MPa in ethanol for 8 h.     

由M0.02Cu0.4Mg5.6Al1.98(OH)16CO3 (M=Ru,Re)水滑石为前驱体制备的双金属固体碱催化甘油氢解

采用共沉淀法合成了M_0.02Cu_0.4Mg_5.6Al_1.98(OH)₁₆CO₃ (M = Ru,Re)水滑石前驱体,然后经焙烧和还原制备了铜分散度较高的双功能M-Cu/固体碱催化剂.这些双功能催化剂在粗甘油氢解制备丙二醇反应中表现出了很好的催化活性.表征结果证明,M的加入增强了催化剂表面氢的吸附和活化,进而促进了甘油的转化.     

SBA-15负载高分散纳米NiO的丙烷氧化脱氢制丙烯催化性能

采用浸渍法通过改变焙烧气氛制备了系列NiO/SBA-15 (w_NiO=20%)催化剂, 并考察了催化剂的丙烷氧化脱氢(ODHP)反应性能. 实验结果表明, 与在静止和流动空气中焙烧的催化剂相比, 在1%NO/He (V_NO/V_He=1:99)气氛中焙烧的NiO/SBA-15-NO具有优异的低温丙烷氧化脱氢制丙烯性能, 在350 ℃时, 丙烷的转化率和丙烯收率分别约达29%和13%. 反应温度升至450 ℃时, 丙烯的选择性仍保持在45%左右. X射线粉末衍射(XRD)和透射电镜(TEM)测试结果表明, 1%NO/He气氛可有效抑制焙烧过程中NiO纳米颗粒的团聚, 使NiO物种高分散于SBA-15 的孔道中. H₂-程序升温还原(H₂-TPR)和O₂-程序升温脱附(O₂-TPD)测试结果表明, 随着NiO在SBA-15上分散度的提高, 催化剂的抗还原性增强, ODHP活性氧物种O-的含量增加, 进而使1%NO/He气氛中焙烧的NiO/SBA-15-NO在较宽的温度范围内(350-450 ℃)均具有良好的丙烯选择性, 并显著提高了催化剂的低温活性.     

Ni掺杂的Cu-ZnO催化剂甘油加氢反应性能

采用浸渍法制备了Ni掺杂的Cu-Zn O催化剂,采用多种物理化学手段研究了其化学物理性质及甘油加氢制取1,2-丙二醇反应催化性能。结果发现,金属Ni助剂的引入可以进一步优化Ni-Cu-Zn O催化剂的甘油加氢生成1,2-丙二醇的反应活性。少量金属Ni的加入,Ni-Cu-Zn O催化剂的甘油转化率变化不大,生成1,2-丙二醇的选择性明显增加。而进一步增加Ni含量到nNi/nCu=0.5,Ni含量过高会导致Ni-Cu-Zn O催化剂中实际Cu原子的量减少,从而导致甘油转化率下降。Ni掺杂的Cu-Zn O催化剂甘油加氢性能稳定性较好,在反应102 h后没有明显变化。     

Hydrogenolysis of glycerol to propanediols over heteropolyacids promoted AgCu/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

Various amounts and different types of heteropolyacids promoted 5Ag15Cu/Al₂O₃ catalysts were prepared by impregnation method and analyzed through many techniques. The synthesized catalysts were evaluated for hydrogenolysis of glycerol to propanediols. The results demonstrated that heteropolyacids loading facilitated the reduction, promoted the dispersion, enhanced the acidity, and increased Broensted acid sites of the AgCu catalysts, which benefited the generation of 1,3-propanediol. Compared with phosphotungstic acid and phosphomolybdic acid, silicotungstic acid promoted AgCu catalyst had a better performance for 1,3-propanediol due to the better Cu dispersion and higher Broensted acidity. In addition, when the reaction was performed at 220 °C under 3.5 MPa for 8 h, the chosen 5Ag15Cu-10HSiW/Al₂O₃ achieved a 69.6% glycerol conversion with 35.6% 1,2-propanediol selectivity and 21.5% 1,3-propanediol selectivity.     

自还原双功能催化剂催化木质纤维素生物质氢解制低碳多元醇的研究

利用生物碳源在煅烧过程中产生的还原性气体还原金属氧化物来制备自还原型双功能催化剂Ni-W/SBA-15,将其直接应用于催化木质纤维素生物质氢解制备低碳多元醇,省去了催化剂还原步骤。TG和XRD结果表明,制备过程中引入的蔗糖含量为3.0 g时,催化剂中被还原的活性金属含量最高;随着Ni含量的增加,镍粒子逐渐增大;W物种为非晶态。SEM和TEM分析表明,SBA-15均匀地负载Ni、W粒子,且粒径小、分散性好。在自还原型催化剂10%Ni-15%W/SBA-15催化作用下,在反应温度为240℃、氢压为5.0 MPa和反应时间为6 h的条件下,微晶纤维素完全转化,低碳多元醇的收率达68.14%;当以小麦秸秆粉作为反应物时,转化率为85.32%,低碳多元醇总收率为44.71%。     

High-surface-area catalyst design: Synthesis, characterization, and reaction studies of platinum nanoparticles in mesoporous SBA-15 silica

Platinum nanoparticles in the size range of 1.7-7.1 nm were produced by alcohol reduction methods. A polymer (poly(vinylpyrrolidone), PVP) was used to stabilize the particles by capping them in aqueous solution. The particles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM investigations demonstrate that the particles have a narrow size distribution. Mesoporous SBA-15 silica with 9-nm pores was synthesized by a hydrothermal process and used as a catalyst support. After incorporation into mesoporous SBA-15 silica using low-power sonication, the catalysts were calcined to remove the stabilizing polymer from the nanoparticle surface and reduced by H2. Pt particle sizes determined from selective gas adsorption measurements are larger than those determined by bulk techniques such as XRD and TEM. Room-temperature ethylene hydrogenation was chosen as a model reaction to probe the activity of the Pt/SBA-15 materials. The reaction was shown to be structure insensitive over a series of Pt/SBA-15 materials with particle sizes between 1.7 and 3.6 nm. The hydrogenolysis of ethane on Pt particles from 1.7 to 7.1 nm was weakly structure sensitive with smaller particles demonstrating higher specific activity. Turnover rates for ethane hydrogenolysis increased monotonically with increasing metal dispersion, suggesting that coordinatively unsaturated metal atoms present in small particles are more active for C2H6 hydrogenolysis than the low index planes that dominate in large particles. An explanation for the structure sensitivity is suggested, and the potential applications of these novel supported nanocatalysts for further studies of structure-activity and structure-selectivity relationships are discussed.     

Ni掺杂的Cu-ZnO催化剂甘油加氢反应性能

采用浸渍法制备了Ni掺杂的Cu-ZnO催化剂,采用多种物理化学手段研究了其化学物理性质及甘油加氢制取1,2-丙二醇反应催化性能。结果发现,金属Ni助剂的引入可以进一步优化Ni-Cu-ZnO催化剂的甘油加氢生成1, 2-丙二醇的反应活性。少量金属Ni的加入,Ni-Cu-ZnO催化剂的甘油转化率变化不大,生成1, 2-丙二醇的选择性明显增加。而进一步增加Ni含量到n_Ni/n_Cu=0.5,Ni含量过高会导致Ni-Cu-ZnO催化剂中实际Cu原子的量减少,从而导致甘油转化率下降。Ni掺杂的Cu-ZnO催化剂甘油加氢性能稳定性较好,在反应102 h后没有明显变化。     

Products distribution of glycerol hydrogenolysis over supported co catalysts in a liquid phase

The products distribution of glycerol hydrogenolysis over supported Co catalysts was evaluated in a liquid phase system. The effects of support type, temperature, pressure and reaction time on the conversion of glycerol as well as yield of desired products were investigated. The preliminary results indicated that various added compounds were generated in the presence of supported Co catalysts. The type of support and the reaction temperature, pressure and time significantly affected either the glycerol conversion or the product yield. The acidity of catalyst played a more important role in the glycerol hydrogenolysis over supported Co catalysts than the specific surface and pore volume. Among the utilized supported Co catalysts, Co/γ-Al₂O₃ exhibited the highest acrolein yield of about 31.1% at 70.5% conversion at 200°C, 8 MPa H₂ pressure and 6 h reaction time.     

Reductive amination of cyclohexanol/cyclohexanone to cyclohexylamine using SBA-15 supported copper catalysts

Amination of cyclohexanol was investigated in vapour phase over copper catalysts supported on mesoporous SBA-15. The different products identified during reductive amination of cyclohexanol reaction were cyclohexanone, cyclohexylamine, along with small amounts of N-Cyclohexylidinecyclohexylamine and dicyclohexylamine. Among several catalysts tested for the reductive amination, 5% Cu supported on SBA-15 exhibited better catalytic performance than other catalysts with 36% selectivity towards cylclohexylamine at 80% cyclohexanol conversion. The optimum reaction conditions employed to achieve the best catalyst performance were at 250 °C, 0.1 MPa of H₂/NH₃, TOS-10h. The active Cu sites, acidity of the catalyst, and effect of reaction parameters play a pivotal role in the reductive amination reaction. The prepared catalysts were characterized by XRD, BET, SEM, H₂-TPR and NH₃-TPD. The dispersion of Cu, particle size, and metal surface area (m²/g) calculated from pulse N₂O decomposition method. TPR findings reveal the presence of substantially dispersed copper oxide species at lower loadings which is easily reducible than the bulk copper oxide species found at higher Cu loadings. The acidity measurements by NH₃-TPD analysis suggest that the maximum acidic strength was obtained at 5 wt% copper on porous SBA-15, and decreased with Cu loadings. The catalytic properties are well in agreement with the findings of catalysts characterization.