水热处理对氧化铝载体物化性质及丙烷脱氢性能的影响

采用水热处理对γ-Al2O3载体改性,并进行XRD、N2物理吸附-脱附、热重、NH3-TPD及H2-TPR表征。结果表明,γ-Al2O3经过"再水合-焙烧"过程,晶型变好,表面总酸量降低,Pt-Al2O3相互作用增加,提高了Pt Sn K/Al2O3催化剂的丙烷脱氢转化率、选择性及稳定性。其中,140℃处理4 h时,氧化铝负载的Pt Sn K催化剂表现出最优的丙烷脱氢性能,100 h内平均转化率为33.6%,平均选择性97.3%,失活参数为15.9%。     

活性炭负载磷钨酸催化合成三羟甲基丙烷三丙烯酸酯

制备了负载型磷钨酸催化剂 ,发现 PW/ C的催化活性比 PW/ Si O2 和 PW/ Ti O2 高。以 PW/C作为丙烯酸与三羟甲基丙烷的酯化催化剂 ,在丙烯酸 0 .78mol、三羟甲基丙烷 0 .2 5mol、催化剂用量约为反应物总量的 0 .7% (质量分数 )、反应温度 1 2 0°C,反应时间 60 min的条件下 ,酯化率达94.6% ,产品纯度 >98% ,并且催化剂可多次使用活性没有明显下降。     

负载Al_2(SO_4)_3型催化剂对1-丁烯齐聚反应的影响

通过等体积浸渍法在载体表面负载不同组分制备了不同酸型和酸强分布的催化剂,探讨负载型固体酸催化剂不同酸型和酸强分布对1-丁烯齐聚反应的影响。结果表明,催化剂的催化性能与其酸量分布和酸型有密切关联。Al2(SO4)3的负载量对催化剂酸量分布产生一定影响,差异主要体现在中强酸位,且中强酸位是此反应的活性酸位。当Al2(SO4)3负载量为0. 667 mmol/g时,Al2(SO4)3/γ-Al2O3催化剂的催化效率最高为76. 9%。催化剂的NH3-TPD和X射线衍射表征结果表明,催化剂的活性物质为硫酸铝,1-丁烯齐聚反应催化剂的活性需要L酸与B酸的共同作用。     

CH_4/CO_2重整反应中NiO-Ce_xZr_(1-x)O_2/Al_2O_3催化剂的研究

通过共沉淀法制备了一系列CexZr1-xO2的介孔材料,采取浸渍法负载10 wt%Ni O/γ-Al2O3,得到不同组成的Ni O-CexZr1-xO2/Al2O3(x=0,0.25,0.5,0.75,1)催化剂。对所得催化剂进行BET、XRD表征分析,同时考察了在相同条件下CH4/CO2重整反应中的催化性能。结果表明:Ni O-Ce0.75Zr0.25O2/Al2O3催化剂有较好的稳定性和抗积炭性,CH4、CO2转化率和H2收率分别可达85.5%、86.4%和93.8%;碱金属助剂有大的比表面积,可使活性组分Ni O充分分散,且随着Ce O2含量增加分散度也提高,使得催化剂抗积炭性能增强,催化活性提高。     

双功能催化剂γ-Al_2O_3-MgO-K_2CO_3中MgO的负载方法及协调作用

研究了用于环戊二烯 ( CPD)和甲醇制备甲基环戊二烯 ( MCPD)的双功能催化剂。制备的催化剂是在 γ- Al2 O3 上分别用混合、沉淀、浸渍法负载 Mg O,焙烧后再负载 1 6% K2 CO3 (摩尔分数 ,下同 )。研究 Mg O负载方法及含量对催化剂活性的影响 ,进行了比表面、XRD和程序升温脱附( TPD)测定。结果表明三种方法形成的催化剂均在含 1 5 %～ 30 % Mg O时呈现高活性。从活性和比表面结果看 ,沉淀法最好 ,混合法次之 ,而浸渍法最差。性能最优化的催化剂是用沉淀法负载 2 5 %Mg O,其 MCPD产率达 76% ,比表面为 1 1 0 .4m2 /g。 XRD分析表明浸渍法的多次焙烧使催化剂表面烧结并形成镁铝尖晶石 ( Mg Al2 O4)。 TPD测定表明在 γ- Al2 O3 - K2 CO3 中负载 Mg O使催化剂表面酸中心强度增强 ,碱中心数量明显增多 ,由此使催化剂酸碱催化功能很有效地“匹配”。     

负载型催化剂在乳化液废水处理中的应用

研究了过渡金属氧化物、稀土金属氧化物、CuO／γAl2O3、MnO2／γAl2O3负载型催化剂及其复合负载型催化剂对乳化液废水催化湿式氧化工艺中的催化活性及处理效果。结果表明,CuO的活性高于MnO2,Co3O4未表现出催化活性,CeO2、Nd2O3、Sm2O3均表现一定活性;CuO／γAl2O3负载型催化剂用于乳化液废水处理,200℃下反应2h,COD去除率为88．4％,MnO2／γAl2O3表现出负催化作用,复合负载型催化剂的活性低于CuO／γAl2O3。     

纳米Al_2O_3负载Ru催化剂用于CO_2加氢合成甲酸研究

为了研究载体性质对Ru负载型催化剂的CO2加氢合成甲酸反应性能的影响,制备了以Al2O3纳米棒和γ-Al2O3为载体的一系列Ru基催化剂,采用透射电镜(TEM)、X射线衍射(XRD)、D2/OH交换和程序升温还原(H2-TPR)等方法详细表征催化剂的性质,并考察CO2加氢制甲酸的反应性能。结果表明:与传统Ru/Al2O3催化剂相比,以Al2O3纳米棒为载体时,Ru Ox物种在载体表面的分散程度高,Al2O3纳米棒的表面OH数目多,有利于提高催化剂的反应活性,另外当Ru在Al2O3纳米棒上的负载量(质量分数)为1%时,甲酸产量最高可以达到11.7mmol/h。     

微波法制备的固体碱催化丁醛自缩合反应

用微波辐射法制备了负载型固体碱催化剂K2 O/γ Al2 O3 、MgO/γ Al2 O3 、KF/γ Al2 O3 、Na2 O/γ Al2 O3 、CaO/γ Al2 O3 和SrO/γ Al2 O3 ,并应用于丁醛的自缩合反应 ,其中K2 O/γ Al2 O3和KF/γ Al2 O3 的活性较好 ,1h产率分别为 5 2 5 %和 4 7 5 %。同时考察了水的浓度及溶剂对反应的影响。结果表明当水的浓度为 1 4mol/L时 ,催化剂的活性最佳 ,而丁醇作为溶剂是几种所用溶剂中最好的一种     

ZnCl_2/Al_2O_3催化尿素和1,2-丙二醇合成碳酸丙烯酯

以Al2O3为载体,采用浸渍蒸发法制备了负载型ZnCl2/Al2O3固体酸催化剂,将其应用于催化尿素和1,2-丙二醇合成碳酸丙烯酯,采用XRD、FTIR等手段分析了ZnCl2与载体Al2O3的结合情况,考察了原料配比、反应温度、催化剂用量、反应时间等条件对反应效果的影响。结果表明,在最佳反应条件下,碳酸丙烯酯的收率可达68.2%。     

助剂和制备方法对V2O5/Al2O3催化性能的影响

用浸渍法制备了负载型MxOy-V2O5/Al2O3催化剂,同时考察了不同的制备方法对MoO3-V2O5/Al2O3催化剂的性能影响。用BET、H2-TPR、TPD平衡法等考察了催化剂的比表面积、氧化还原性能、表面氧脱附性能,结果表明,添加变价助剂Mo、Fe和Cr氧化物会增加供氧数目,提高α-蒎烯转化率。MoO3-V2O5/Al2O3催化剂表面O 2-和O-物种较多,活性也较好,桃金娘烯醛收率较高。MoO3-V2O5/Al2O3催化剂的制备方法影响其催化性能,表面化学改性法制备的催化剂表面具有较多O2-和O-物种,有利于催化剂的活性提高,α-蒎烯的转化率达88.9%,桃金娘烯醛的收率为79.1%。     

Complex metal oxide catalysts for selective oxidation of propane and derivatives: II. The relationship among catalyst preparation, structure and catalytic properties

The effects of the preparation methods on the structure and catalytic performance of the MVTeNb (M=Mo or W) complex metal oxides (CMO) in selective oxidation of propane to acrylic acid (AA) were investigated. Preparation methods can play as significant roles as the chemical composition in determining the structures and catalytic properties of a CMO catalyst. Undesirable preparation methods or conditions can lead to the formation of ineffective crystal phases in the resulting catalysts, leading to poor catalytic activity or selectivity. An effective MoVTeNb oxide catalyst for propane selective oxidation to acrylic acid could be obtained with a combination of a proper metal ratio and proper preparation procedures. Certain drying methods, such as freeze dry and heat evaporation, are undesirable because phase segregation tends to occur during such processes, which negatively affect the catalytic performance. The preferred drying method is the rotavap method, which favors the formation of an effective crystal phase and suppresses the formation of impurity phases. The preferred calcination atmosphere is an inert atmosphere while a calcination atmosphere containing oxygen leads to the formation of significant amounts of MO₃ in MVTeNb oxides (M=Mo or W), which is known to be inactive in propane oxidation. It is proposed that an effective MoVTeNb oxide catalyst for propane selective oxidation to acrylic acid should contain at least two major crystal Phases A and B. Based on studies of oxides of pure Phase A and those exclusively enriched with Phase B, X-ray diffraction (XRD) characteristics of the two major crystal phases (A and B) have been identified and their catalytic functions studied. It is proposed that Phase A is active in propane activation but relatively unselective for the acrylic acid formation, while Phase B is reasonably active for propane activation and fairly selective for acrylic acid formation. It has been shown that using MoVTeNb oxide catalyst with a proper ratio of Phases A and B and synergy between them, very high propane conversion (73%) and acrylic acid selectivity (58%) can be achieved at the same time.     

Propane Selective Oxidation Over Monophasic Mo–V–Te–O Catalysts Prepared by Hydrothermal Synthesis

Two distinct phases, orthorhombic and hexagonal, of Mo–V–Te–O mixed oxide catalysts were prepared separately by the hydrothermal synthetic method and solid-state reaction, and these catalysts were tested for propane selective oxidation to acrylic acid. The hydrothermally synthesized orthorhombic phase of the Mo–V–Te–O catalyst showed high activity and selectivity for the oxidation of propane into acrylic acid. This catalyst also showed extremely high catalytic performance in the propene oxidation, producing acrylic acid in a high yield. The hexagonal Mo–V–Te–O catalyst was formed via the solid-state reaction between the orthorhombic Mo–V–Te–O and -TeVO₄. This phase showed poor activity to both propane and propene oxidations, although the hexagonal phase was constructed with the octahedra of Mo and V similar to the orthorhombic phase. Reaction kinetics study over the catalyst with orthorhombic structure revealed that propane oxidation was of first order with respect to propane and nearly zero order with respect to oxygen, suggesting that the rate-determining step of the reaction is C–H bond breaking of propane to form propene. Structural effects on the catalytic oxidation performance were discussed.     

Effect of Potassium Doping on the Catalytic Behavior of Mo–V–Sb Mixed Oxide Catalysts in the Oxidation of Propane to Acrylic Acid

Small addition of potassium to a Mo–V–Sb mixed oxide catalyst (previously prepared by hydrothermal synthesis) strongly modifies its catalytic behavior. Thus, while acetic acid is mainly observed in the K-free catalysts, acrylic acid is selectively obtained in K-doped catalysts. In this case, a selectivity to acrylic acid of about 30% is achieved at propane conversions of 30%. This catalytic behavior is apparently not due to modification of the crystalline phases in the K-doped catalysts but to the elimination of the acid sites of the undoped Mo–V–Sb mixed oxide catalyst.     

丙烷选择氧化制丙烯酸复合金属氧化物催化剂的研究

采用溶胶-凝胶法制备了一种MoVTeNbO复合金属氧化物催化剂,考察了反应温度、空速、原料气比例和原料中水蒸汽等工艺条件对丙烷选择氧化制丙烯酸催化性能的影响。结果发现,用溶胶-凝胶法制备的复合金属氧化物催化剂前驱体,当反应温度为400 ℃、空速1 800 h^-1、原料气:n(C₃H₆)∶n(O₂) ∶n(Ar) ∶n(H₂O)=4.4∶12.8∶36.9∶15.3时,表现出很好的丙烷选择氧化制丙烯酸催化性能,丙烷转化率、丙烯酸选择性和丙烯酸的收率分别为60%、49.9%和30%。     

VOCs催化燃烧催化剂Mn/γ-Al2O3和CuMn/γ-Al2O3的性能研究

用浸渍法制备了两种负载型的Mn/g -Al2O3和Cu-Mn/g-Al2O3复合氧化物催化剂,同时用共沉淀法制备了Cu-Mn-O复合氧化物催化剂。以气相色谱为检测手段,用常压气体流动评价装置考察了这三种催化剂对苯、甲苯、二甲苯等挥发性有机化合物VOCs的催化燃烧性能。发现负载型的催化剂转化率达到99%时的反应温度比非负载型的降低30~40C,其中Cu-Mn/g-Al2O3催化剂具有更好的低温活性,催化燃烧反应的速率明显提高。负载型催化剂表面的活性组分以高度分散状态存在和催化剂高的比表面积是性能好的主要原因。     

Surface texturing of Mo–V–Te–Nb–O x selective oxidation catalysts

The paper concentrates on the study of Mo–V–Te–Nb oxide mixtures by electron microscopy combined with catalytic investigation of these materials in the partial oxidation of propane. Surface texturing of catalyst particles composed of two phases referred to in the literature as M1 and M2 is revealed by high-resolution transmission electron microscopy of high performing catalysts. The chemical composition of the catalyst surface is modified by treatment in water to obtain a significant increment in yield of acrylic acid. A chemical realization of the site isolation concept recurring on a supramolecular arrangement of catalyst and reactant rather than on atomic site isolation is suggested. A complex Mo–V–Te–Nb–O _x precursor phase carries nanoparticles made from a network of oxoclusters active as catalyst for the conversion of propane to acrylic acid. The designed synthesis of the multi-element oxide bulk and of the surface structure with a different composition than the precursor phase improved the performance by a factor of 4.     

丙烷直接氧化制丙烯酸的研究进展及展望

丙烷直接氧化制丙烯酸是近年来烃类催化氧化的热点课题。MoVTeNbOx复合金属氧化物催化剂被认为是目前对于该反应催化性能最好的一类催化剂。作者针对在丙烷直接氧化制丙烯酸领域中影响MoVTeNbOx系列金属氧化物催化性能的因素及将来可能开发的烃类选择氧化反应新工艺两方面进行综述。     

固体超强酸SO_4~(2-)/Fe_2O_3催化合成丙酸丙酯

利用制备的固体超强酸SO2-4/Fe2O3代替浓硫酸作催化剂,将正丙酸和正丙醇酯化合成丙酸丙酯,讨论了催化剂的制备及合成丙酸丙酯的条件。实验表明:固体超强酸不仅能减少对生产设备的腐蚀,而且具有很好的催化活性,当催化剂用量为1.0g(正丙酸为0.1mol),醇酸摩尔比为2.5∶1,回流反应3h时,酯收率可达97.2%。     

电镀法制备FeCrAl合金负载的Co_3O_4催化剂及对丙烷的电焦耳催化氧化

金属载体负载型催化剂的电焦耳催化氧化是挥发性有机物控制技术,其核心是向金属载体中通入电流,产生焦耳热来实现负载的催化剂活化。受制于催化剂涂层与金属载体之间较低的黏附力,催化剂在金属表面的负载是技术难点。将Co和Ce电镀到FeCrAl合金表面,焙烧形成氧化物催化剂,并用于丙烷的电焦耳催化氧化。结果表明,对合金载体表面进行阳极氧化预处理,可以有效促进催化剂组分的分散,而且催化剂涂层上有空穴结构,有利于反应过程的传质; CeO_2的存在显著提高Co_3O_4催化剂对丙烷的催化氧化性能。通过进一步优化,电镀法可成为制备金属负载型催化剂的有效方法。     

MoVTeNbO_x催化剂焙烧条件对丙烷氧化制丙烯酸的影响

制备了Mo1V0.25Te0.13Nb0.12Ox催化剂,研究了焙烧条件（焙烧方式、焙烧气氛和焙烧温度）对该催化剂在丙烷选择氧化制丙烯酸反应中的影响。结果表明,两段间歇式焙烧要优于一段式连续焙烧所得催化剂的催化效果,适宜的预焙烧温度既有利于脱除挥发性物质和化学结合水,又能避免活性组分氧化生成不利的晶相;在惰性气氛中焙烧所得催化剂的催化效果要优于在弱氧化性气氛中焙烧,丙烷转化率和丙烯酸收率随着焙烧温度的升高先增加后减小,在600 ℃时达到最大值。