MoBiTeO/SiO2催化剂在丙烷选择氧化反应中的表面结构重组

 考察了MoBiTeO/SiO2催化剂对丙烷选择氧化制丙烯醛的催化性能,并采用原位拉曼、 X射线衍射和X光电子能谱等技术研究了催化剂在反应过程中的结构重组及其对催化性能的影响. 实验结果表明,反应前, MoBiTeO/SiO2催化剂主要由Te多钼酸盐物种组成; 在570 ℃和C3H8/O2/N2=1.2/1/4的反应条件下, MoBiTeO/SiO2催化剂中的部分Te组分被深度还原为金属Te而流失,使部分Te多钼酸盐物种进行了结构重组形成了MoO3物种. Te多钼酸盐和MoO3之间的协同作用使催化剂的催化性能提高.     

二氧化硅负载氧化锌催化剂的溶胶-凝胶和浸渍法制备及对仲丁醇分解反应的催化性能

分别采用溶胶-凝胶法和浸渍法制备了ZnO-SiO₂催化剂和ZnO/SiO₂催化剂并进行了表征, 以仲丁醇脱氢为探针反应, 研究了不同制备方法对催化剂表面ZnO物种存在状态及其催化性能的影响. 结果表明, 2种方法均可制备高分散的负载型ZnO催化剂. 在ZnO-SiO₂和ZnO/SiO₂催化剂上, 仲丁醇分别以脱水和脱氢反应为主. 经过分析, 催化剂上ZnO物种的存在状态是影响产物选择性的关键因素, 而2种催化剂表面的粒径、 比表面积和表面酸碱性不是影响该反应选择性的根本原因.     

高硫化氢合成气制甲硫醇新型钼基催化剂研究

研究了一系列负载型钼基催化剂催化含高硫化氢合成气制甲硫醇的性能,用XPS和ESR对其进行表征.活性测试显示,钾促进的钼基催化剂催化的反应产物中甲硫醇成为主导产物.几种钼基催化剂合成甲硫醇的活性大小顺序:K₂MoO₄/CoO/SiO₂>K₂MoO₄/SiO₂>MoO₃/K₂CO₃/SiO₂>K₂MoS₄/SiO₂>MoS₂/K₂CO₃/SiO₂.ESR表征显示,反应后的催化剂可以检测到"oxo-Mo(V) "和"thio-Mo(V)"物种.XPS表征显示反应后催化剂中的Mo包含着Mo⁴⁺,Mo⁵⁺和Mo⁶⁺,S包含着S^2-,(S-S)^2-和S⁶⁺三种价态.添加CoO后,"oxo-Mo(V)"含量减少,而"thio-Mo(V)"含量增加,(S-S)^2-物种的生成得到抑制,S^2-物种的量增多.(Mo⁴⁺+Mo⁵⁺)/Mo⁶⁺峰强度比为0.75以及S^2-/(S-S)^2-接近1有利于甲硫醇的生成.本文提出甲硫醇的合成与"Mo-S-K"相关联的反应机理.     

分子筛稳定的孤立Mo物种催化氧化脱硫研究

本工作通过两步后合成方法，使用脱铝Si-beta分子筛和双（环戊二烯基）二氯化钼（Cp₂MoCl₂）制备了一系列Mo负载的Mo/beta分子筛材料.通过一系列谱学技术对Mo/beta进行表征分析，发现以beta分子筛为载体材料，可以将孤立的钼物种以（Si-O）₂Mo（=O）₂的形式稳定限域于BEA分子筛结构中.将所制备的Mo/beta分子筛应用于模拟柴油催化氧化脱硫（ODS）反应中，考察了不同的载体、钼负载量、温度和反应底物随着反应时间的变化，并进行典型动力学分析.源于BEA分子筛结构限域以及结构明确的孤立双氧钼物种，实验所制备的1% Mo/beta催化剂对模拟柴油中二苯并噻吩等模型杂环硫化合物表现出优异的氧化脱除效果，并成功解决了传统Mo/SiO₂催化剂钼物种流失、循环稳定性差的缺点，具有工业应用前景.     

丙烷选择氧化制丙烯醛MoBiTeO/SiO2催化剂中Te组分的作用

用浸渍法制备了一系列不同Te含量的MoBiTeO/SiO2催化剂, 并用XRD、Raman、XPS、NH3-TPD、吡啶吸附FT-IR和催化剂性能评价等方法考察了Te组分对催化剂的结构、酸性及其丙烷选择氧化制丙烯醛性能的影响. 结果表明, 催化剂中Mo氧化物与Te氧化物之间发生了相互作用, 通过形成Mo—O—Te 桥氧键生成了Te多钼酸盐物种,在一定程度上分散了Mo-O活性中心, 同时TeOx具有脱除丙烯α-H、插氧并将其转化为丙烯醛的功能, 因此, 在MoBiO/SiO2催化剂中添加Te组分使丙烯醛选择性有显著的提高. 但是Te的加入同时也使催化剂中B 酸增强, 这不利于丙烯醛生成. 因此, Te添加量有一最佳范围, nTe/nMo为0.05-0.1 时催化剂具有较好的催化性能.     

H2S/H2硫化温度对MoP/SiO2催化剂硫醚化性能的影响

以负载磷酸钼为前驱体,采用程序升温还原法制备了MoP/SiO₂催化剂,以体积分数3%H₂S/H₂对其进行了硫化处理,利用XRD、CO化学吸附、NH₃-TPD、HRTEM-EDX、ICP-AES以及XPS等手段对催化剂进行了表征,研究了硫化温度对MoP/SiO₂催化剂结构和异戊二烯与正丁硫醇硫醚化性能的影响。结果表明,即使在400℃硫化处理也未改变MoP/SiO₂催化剂中MoP体相结构;随着硫化温度提高,催化剂表面酸量增加、金属位数量减少,降低了催化剂C-S键氢解及异戊二烯深度加氢活性,但同时也提高了催化剂烯烃聚合活性。经120℃硫化处理的MoP/SiO₂兼具较佳硫醚化及异戊二烯选择加氢性能。     

水热合成的MoO3-SnO2催化剂催化氧化二甲醚的性能研究

采用无沉淀剂水热法一步合成了MoO₃-SnO₂复合金属氧化物催化剂,通过调变Mo/Sn物质的量比,考察了催化剂上活性组分MoO_x分散程度对二甲醚（DME）低温氧化生成甲酸甲酯（MF）反应性能的影响。当Mo/Sn=1∶2,反应条件为150℃时,催化剂表现出较好的催化性能,DME转化率为22.0%,MF选择性达到77.6%。实验中采用TEM、XRD、Raman、FT-IR、NH₃-TPD及H₂-TPR等表征对催化剂晶体结构及表面性质进行了分析。结果发现,Mo/Sn物质的量比变化会对催化剂晶体结构产生显著影响,钼氧化物在SnO₂表面形成不同分散程度的MoO_x结构,这种钼氧化物结构的变化进一步影响了催化剂表面的酸性及氧化还原性,是造成催化性能差异的主要原因。     

ZrO2晶相对ZnO/ZrO2+SAPO-34双功能催化剂上合成气制烯烃反应的影响

烯烃是重要的化工原料,目前主要通过石油催化裂化得到.随着石油资源的消耗以及人们对烯烃需求的日益增长,开发非石油路线制取烯烃势在必行.合成气可以从煤、天然气和生物质等获得,由合成气作为重要的C1平台分子一步制取烯烃(STO)的过程受到了广泛关注.将合成气制甲醇/二甲醚的金属催化剂与甲醇制烯烃的分子筛催化剂耦合得到的混合双功能催化剂,可以使合成气高选择性地转化为烯烃.其中,ZnO/ZrO₂金属氧化物催化剂被广泛应于合成气的活化,然而,该金属氧化物结构对混合双功能催化剂上合成气制烯烃反应的影响尚不明确.本文合成了单斜相ZrO₂(m-ZrO₂)和四方相ZrO₂(t-ZrO₂),并负载ZnO制成催化剂,再将其与SAPO-34分子筛物理混合得到混合双功能催化剂,用于合成气制烯烃反应中.在较优化的条件下,ZnO/m-ZrO₂与SAPO-34分子筛组成的双功能催化剂CO转化率为27.9%,低碳烯烃选择性高达80.5%,性能明显优于ZnO/t-ZrO₂+SAPO-34双功能催化剂.为研究ZrO₂晶相对催化合成气制烯烃反应性能的影响,对ZnO/ZrO₂进行红外光谱表征.结果表明,ZnO/m-ZrO₂较ZnO/t-ZrO₂具有更多的表面羟基和更多的路易斯酸性位点.金属氧化物表面的路易酸主要与催化剂表面不饱和的金属离子有关,而且Zr基催化剂表面羟基有助于缺陷氧的形成,因此,ZnO/m-ZrO₂催化剂表面应该具有更高浓度的氧缺陷位.光电子能谱进一步证明了ZnO/m-ZrO₂表面有更高浓度的氧缺陷位.另外,Zr基催化剂上表面羟基还有利于CO与其形成羧酸盐物种,在623-673 K条件下的CO原位吸附的红外光谱表明,ZnO/m-ZrO₂催化剂上CO吸附的浓度及其表面羧酸盐浓度均明显高于ZnO/t-ZrO₂催化剂,这与ZnO/m-ZrO₂表现出更好的催化合成气转化性能一致.为了探究该催化剂体系上合成气制烯烃的反应路径,分别对两种晶相的ZnO/ZrO₂和相应的双功能催化剂进行了原位红外监测.与CO红外漫反射相比,合成气氛围下金属氧化表面除了存在吸附态的CO和甲酸盐物种,还存在表面甲氧基物种,后者是合成气制甲醇/二甲醚过程重要的中间物种.对合成气制烯烃过程中分子筛上的停留物种进行分析,结果发现,停留物种中含有多甲基苯、多甲基萘等甲醇制烯烃过程中的烃池物种.另外,合成气氛围下双功能催化剂甲氧基信号峰明显弱于金属氧化物表面甲氧基的信号强度,表明STO过程应该是合成气制甲醇/二甲醚与甲醇制烯烃的串联过程.综上所述,在STO反应中,相较于ZnO/t-ZrO₂催化剂,ZnO/m-ZrO₂催化剂具有更高浓度的表面羟基物种、路易斯酸密度和表面氧缺陷位,从而有利于羧酸盐及甲氧基中间物种的形成,进而提高了混合双功能催化剂催化STO反应性能.     

银离子修饰的介孔磷钨酸/二氧化硅催化剂氧化脱硫性能研究

采用银修饰介孔磷钨酸/二氧化硅（mesoporous HPW/SiO₂）催化剂,并研究了其在模拟柴油和真实柴油氧化脱硫反应中的催化性能。通过银修饰介孔HPW/SiO₂,结合银离子对有机硫化物的选择吸附性和HPW对有机硫化物的催化氧化活性,以达到选择氧化脱硫的目的。模拟柴油分别采用石油醚、苯、1-辛烯和二苯并噻吩配制,当银离子与HPW的摩尔比为2时,催化剂具有最高的选择催化氧化活性。采用N₂ 吸附-脱附、XRD、UV-vis和EDS表征了银修饰的介孔HPW/SiO₂催化剂,结果表明,银物种分散均匀且以Ag⁺形式存在。真实柴油的脱硫研究表明,相比介孔HPW/SiO₂催化剂,修饰的催化剂介孔Ag₂-HPW/SiO₂脱硫率提高了4.6%,初始硫含量为1800×10^-6的直馏柴油能被脱除至228×10^-6,脱硫率为87.3%。介孔Ag₂-HPW/SiO₂催化剂具有良好的再生性能,经再生处理后,Ag的损失量极少,其三次脱硫率达到84.8%。     

镧改性Cu/SiO2催化剂的乙酸甲酯高效加氢催化性能研究

采用蒸氨法制备了镧(La)改性的负载型铜硅(Cu/SiO₂)催化剂,并对其乙酸甲酯(MeOAc)气相加氢制乙醇(EtOH)的催化性能进行了研究。采用N₂吸附-脱附(N₂ adsorption-desorption)、X射线粉末衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)、氢气程序升温还原(H₂-TPR)、傅里叶红外光谱(FT-IR)、高分辨透射电镜(HRTEM)、光电子能谱(XPS)和原子发射光谱仪(AES)等手段对催化剂进行了的表征,发现La物种的加入产生了较多的层状硅酸铜,增强了Cu和La物种之间的相互作用。La物种的加入在结构方面提高了催化剂的比表面积,降低了铜物种的粒径,提高了铜物种的分散度;在电子还原调控方面提高了Cu⁺的含量,增强了催化剂吸附酰基和甲氧基的能力。与未改性的Cu/SiO₂催化剂相比,镧改性后Cu/SiO₂催化剂的乙酸甲酯加氢性能得到大幅提升;其中La掺杂量0.5%的Cu/SiO₂     

丙烷选择氧化制丙烯醛催化剂中Ce的作用

考察了一系列助剂如:Cu、Zn、Mn、W、Ce、Pr、Nd等对Ag-Mo-P-O催化剂丙烷选择氧化制丙烯醛的影响.其中添加助剂Ce的Ag-Mo-P-O催化性能较好.添加Ce降低了丙烷氧化反应的活化能并有利于中间产物丙烯转化为丙烯醛.采用BET、XRD、H2-TPR、O2-TPD、C3H8-TPD和EPR等方法,研究了含Ce催化剂的结构和性质.结果表明,助剂Ce改善了催化剂的可还原性,并调变了催化剂中Mo5＋/Mo6＋比例,有利于催化剂上丙烷选择氧化生成丙烯醛,这可能归因于催化剂中形成Ce3＋＋Mo6＋Ce4＋＋Mo5＋氧化-还原循环的缘故.     

The effects of Te on the performance of Mo-V catalysts prepared by hydrothermal synthesis

Some Mo-V-Te-La catalysts with varied component were prepared by hydrothermal synthesis and dried with microwave method. The component of the catalyst were greatly affected the crystal structure and Raman spectrum. The phase in the catalysts was different when the Mo, V, and Te content varied. When the catalyst containing the same Mo, V content, due to the effect of dopant of Te element (V0.07 Mo0.93)5O14 became the main phase in the catalyst. The catalyst also showed good activity for the reaction of selective oxidation propane to acrolein and acrylic acid.     

BiMo 基复合氧化物催化剂晶格氧性质与丙烷选择氧化性能

研究了不同组成、结构的BiMo基复合氧化物催化剂的丙烷选择氧化至丙烯醛的性能.X射线衍射(XRD)、X光电子能谱(XPS)、原位傅里叶变换激光拉曼光谱(FT-LRS)、电子顺磁共振(ESR)等多种表征结果表明,BiMo基复合氧化物催化剂上丙烷经由中间物丙烯选择氧化至丙烯醛,催化剂的晶格氧为选择性活性氧物种.丙烷直接氧化下丙烷至丙烯醛的选择性和收率与催化剂的Mo=O物种的氧化-还原性质密切关联,而Mo=O物种的性质又取决于Mo离子的配位环境,Mo=O物种的选择性转化丙烷经由丙烯至丙烯醛活性随畸变MoO6八面体、共顶点八面体、共边八面体、MoO4四面体配位环境递增.组成、结构优化调变的催化剂上丙烷选择氧化至丙烯醛选择性和收率可达45%和13.5%,催化剂中具有选择氧化活性的晶格氧物种数可达258 μmol/g.     

Effect of Different Dopant in the Mo-V-Te-O Catalyst on the Performance of Selective Oxidation Propane to Acrolein

Several Mo-V-Te-O mixed metal oxides catalysts with different dopant were prepared and used for catalytic oxidation propane to acrolein. It was revealed that the addition of P could greatly improve the performance of the Mo-V-Te-O catalyst. The catalysts were examined by XRD and H2-TPR. The XRD characteristic of the Mo-V-Te-P-O showed that the addition of P could aggrandize the (V0.07Mo0.93)5O14 phase. H2-TPR illuminated that the MoV0.3Te0.23P0.15On catalyst took on the best redox ability.     

钼基催化剂氧化还原性质对丙烷选择氧化制丙烯醛反应的影响

 制备了Ag0．3MoP0．6Ox和Ce0．1Ag0．3MoP0．6Oy催化剂，并用XRD，TPR，LRS，XPS和EPR对催化剂进行了表征，考察了催化剂的氧化还原性质及其对丙烷选择氧化制丙烯醛反应的催化性能．结果表明，由于Ce和Mo发生相互作用，调变了催化剂的可还原性和配位不饱和Mo的量，使Ce0．1Ag0．3MoP0．6Oy催化剂对反应中间产物丙烯和正丙醇转化为丙烯醛具有较高的能力，从而提高了催化剂的活性．     

BiMo基复合氧化物催化剂丙烷直接氧化至丙烯醛研究

The effects of the available zoon above the catalyst bed on the performance of the catalyst were investigated. It has been suggested that propylene is an intermediate species in the reaction of propane to acrolein， and a two-step reaction scheme is proposed， the first step is oxidative dehydrogenation of propane to propylene in the gas phase then followed by the second step， the selective oxidation of propylene to acrolein on the surface of the catalyst. The performance of the catalyst depends on both the oxidative dehydrogenation of propane to propylene in the gas phase and the selective oxidation of propylene to acrolein on the catalyst surface. The thermal cracking， homogeneous oxidative dehydrogenation and heterogeneous catalytic dehydrogenation of propane as well as the selective catalytic oxidation of propane to acrolein over BiMoO based mixed oxides catalysts were studied. Under the optimum reaction conditions of propane dehydrogenation and selective oxidation of propylene， the selectivity and the yield of acrolein approached to 45mol% and 14mol%， respectively under about 30mol% propane conversion.     

Roles of surface Te, Nb, and Sb oxides in propane oxidation to acrylic acid over bulk orthorhombic Mo-V-O phase

The outermost surfaces and subsurface layers of the orthorhombic (M1) Mo-V-O catalysts promoted with Te, Nb, and Sb oxide species at submonolayer surface coverage were examined by low-energy ion scattering (LEIS). This study indicated that the Nb oxide species was preferentially located at the topmost surface, while the subsurface Te and Sb concentrations declined gradually into the bulk. Although the original Mo-V-O catalyst was essentially unselective in propane oxidation to acrylic acid, significant improvement in the selectivity to acrylic acid was observed when Te, Nb, and Sb oxides were present as the surface species at submonolayer coverage. These findings further suggested that the formation of the surface V-O-M bonds (M = Nb, Te, or Sb) was highly beneficial for both the activity and selectivity of the orthorhombic Mo-V-O catalysts in propane oxidation to acrylic acid. The highest selectivity was observed when both Nb and Te (or Sb) oxide species were present at the surface. The selectivity trends established for the surface-promoted Mo-V-O catalyst parallel those found previously for the corresponding bulk Mo-V-M-O catalysts. These results further indicated that the introduction of surface metal oxide species is a highly promising method to prepare well-defined model catalysts for studies of the structure-activity/selectivity relationships as well as optimize the catalytic performance of the bulk mixed Mo-V-M-O catalysts for selective (amm)oxidation of propane.     

Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based Composite Oxide Catalysts

Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) supported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and BET corroborated that the mixed oxides were dispersed homogeneously on the surface of support. The activity of lattice oxygen in the catalysts was studied by TPR, and the chemisorption property of isobutane on the surface of the catalysts was investigated by the TPD method. H2-TPR of the catalysts revealed that the lattice oxygen of the vanadium-based catalysts is more active than that of the molybdenum-based catalysts. The redox property of V or Mo species is slightly affected by other compositions of the series catalysts. The TPD curves illustrate that there are two kinds of adsorptive species of isobutane on     

Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based

Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) supported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and BET corroborated that the mixed oxides were dispersed homogeneously on the surface of support. The activity of lattice oxygen in the catalysts was studied by TPR, and the chemisorption property of isobutane on the surface of the catalysts was investigated by the TPD method. H2-TPR of the catalysts revealed that the lattice oxygen of the vanadium-based catalysts is more active than that of the molybdenum-based catalysts. The rcdox property of V or Mo species is slightly affected by other compositions of the series catalysts. The TPD curves illustrate that there are two kinds of adsorptive species of isobutane on the surface of the V and Mo based catalysts. The adsorbing species on the VMoP/SiO2 catalyst are identical to the main adsorbing species on VP/SiO2 and MoP/SiO2. The catalyst VMoP/SiO2 is more active than others in the selective oxidation of isobutane.