负载型Fe-Ce催化剂低温SCR脱硝性能的研究

以氧化铝为载体,负载不同比例的金属组分Fe、Ce制作单组分及多组分的负载型催化剂。实验研究在不同反应温度、氧含量和空速比下,此类负载型催化剂的SCR脱硝性能。结果表明:由于稀土元素Ce的加入,多组分的8Fe-2Ce/Al_2O_3的催化脱硝效率明显高于单组分的8Fe/Al_2O_3,在240℃时可达94%,而且具有比单组分催化剂更好的抗硫性能。但Ce的加入并不是越多越好,Ce的过量加入反而会影响催化剂的催化脱硝效率。催化剂的制备方法与其催化脱硝效率有关,沉淀法制备的催化剂的催化脱硝效率高于浸渍法制备的催化剂,以450℃煅烧制备的催化剂的催化脱硝效率高于550℃煅烧的催化剂。脱硝实验条件影响催化剂的催化脱硝效率,3%氧含量下的催化脱硝效率高于无氧条件下的,低空速比时脱硝效果高于高空速比的。     

CuO-CeO2-MnOx/γ-Al2O3催化剂选择性催化脱除NO机理研究

利用溶胶凝胶法制备CuO-CeO2-MnOx/γ-Al2O3催化剂颗粒,在固定床上测试其催化脱硝活性.CuO-CeO2-MnOx/γ-Al2O3催化剂在200～450℃范围内脱硝效率保持在70%以上.利用程序升温方法研究了催化剂对NH3的氧化性能,活性组分负载量增多,加强了催化剂对NH3氧化性能.红外表征显示NH3被吸附在催化剂的L酸位和B酸位.NO以多种硝酸盐物种在催化剂表面吸附.吸附态NH3参与SCR反应,但吸附态NO物种仅部分参加SCR反应.     

CuO/γ-Al2O3催化吸附剂脱硝性能研究

本文采用溶胶-凝胶法制备CuO/γ-Al2O3催化吸附剂颗粒.分析表明:SO2的存在可以提高CuO/γ-Al2O3催化吸附剂的脱硝活性,SO2存在条件下,CuO/γ-Al2O3催化吸附剂的脱硝活性在载铜量8wt%时达到最高,达到95.7%.载铜量太高会使单位质量催化剂NO脱除率降低.在350℃时,硫酸盐化和未硫酸盐化的8wt%Cu催化吸附剂NO脱除率达到最高.NH3/NO摩尔比在1～1.2之间时,CuO/γ-Al2O3催化吸附剂的脱硝活性较高.     

MnOx/Ti-PILC低温NH3-SCR脱除NO研究

实验制备并测试MnO_x/Ti-PILCs的低温（80～260℃）SCR脱硝活性,发现当MnO_x负载量为10%,催化剂煅烧温度为300℃时催化剂表面酸性较强,活性成分分散较好,脱硝活性最佳,在180℃下,NO脱除效率接近100%。研究了氧浓度和空速等对脱硝效率的影响,发现O₂浓度为3%时,对催化剂最为有利;在65000 h^-1的高空速条件下,10 MnO_x/Ti-PILC（300）依然表现出较高活性。MnO_x/Ti-PILC与MnO_x/Al₂O₃活性相当,高于MnO_x/TiO₂。     

铁矿石低温催化脱硝性能研究

分别对不同铁矿石进行煅烧处理制备催化剂,研究其低温SCR脱硝活性。通过对催化剂进行XRD分析和BET测试,确定催化剂主要组成成分及表面结构特性。研究结果表明:赤铁矿的活性成分为α-Fe_2O_3,在240~300℃脱硝效率达90%以上;锰铁矿活性成分主要是Mn_2O_3和Fe_2O_3,在低温条件下表现优秀的脱硝性能,尤其是450℃煅烧制备的催化剂在90~270℃温度区间均保持99%以上的脱硝效率,且抗SO_2中毒性能较强,是一种具有广泛应用前景的低温SCR脱硝催化剂。     

Mn掺杂对磁性γ-Fe_2O_3低温SCR脱硝活性的影响

采用共沉淀法制备一系列Fe_(1-x)Mn_xO_z(x为Mn物质的量比,x=0、0.1、0.3、0.5)磁性催化剂,考察Mn掺杂对γ-Fe_2O_3催化剂低温SCR脱硝活性的影响规律。结果表明,Mn掺杂能显著提高γ-Fe_2O_3的低温SCR脱硝活性,并拓宽其活性温度窗口;Fe_(0.7)Mn_(0.3)O_z催化剂的低温SCR脱硝活性最高,在125~200℃其NO_x转化率约为100%。N_2吸附及XRD分析结果表明,Mn的掺杂能优化γ-Fe_2O_3催化剂的孔隙结构及孔径分布,增大其比表面积和比孔容,并与催化剂中铁氧化物相互作用形成良好固溶体,从而提高γ-Fe_2O_3催化剂的低温SCR活性。     

以飞灰为载体的低温SCR成型催化剂的性能研究

本文采用30%硝酸酸洗预处理可以去掉飞灰中绝大部分碱金属以及碱土金属，其比表面积相比提高近30倍，在此基础上将其作为催化剂载体并采用浸渍法制备出5种不同Mn掺杂量的粉末状低温脱硝催化剂。通过BET、SEM、XRD、XPS等表征手段，对比发现当含Mn量为20%时，由于催化剂中高活性的Mn⁴⁺、Mn³⁺以及O_β的相对含量较高，使其在180～260?C脱硝效率都超过了90%，并且在200℃达到最高的98.76%。此时，将筛选出的活性组分浸渍负载在不同成型形状的飞灰载体上，研究发现当体积空速一致时，圆孔状催化剂相对其他成型形状具有更好的脱硝性能，并且在200?C时可以达到98.56%的最大脱硝活性，同时其机械抗压强度达到2.04 MPa。另外在10%H₂O和0.02%SO₂混合气氛下，催化剂的脱硝性能仍维持在71.41%以上。     

Cr-MnO_x/堇青石催化剂制备及催化降解邻二氯苯性能研究（英文）

采用溶胶凝胶法、浸渍法、共沉淀法以及流变相法制备了新型Cr-MnO_x/堇青石催化剂,同时采用X射线衍射(XRD)、扫描电镜(SEM)、热重和差热分析(TG-DTA)、H_2-程序升温还原(H_2-TPR)以及元素能谱(EDS)技术对催化剂进行表征。经筛选发现,以共沉淀法制备的Cr-MnO_x/堇青石催化剂(Cr/Mn=2∶5)催化活性最高。通过表征结果可知,以共沉淀方法制备的催化剂主要活性成分为Mn_2O_3和Cr_2O_3,并且具有特殊的球形和较好的氧化还原性能,协同作用的存在有助于催化降解目标污染物邻二氯苯(o-DCB)性能的提高;在60h之内,o-DCB降解率仍保持在80%以上,具有较好的催化稳定性。     

甲烷部分氧化制合成气Pt/Al_2O_3催化剂的表征及其反应性能评价

采用浸渍法制备了3种不同负载量的Pt/Al2O3催化剂,考察了催化剂的甲烷选择氧化性能,并用程序升温还原技术,程序升温脱附技术以及微型脉冲催化色谱技术对催化剂进行表征。结果表明,随着Pt的负载量升高,甲烷催化氧化的性能也越好,对CO与H2的选择性也越高。其中,在750℃原料气组成CH4/O2为2∶1,4%Pt负载量的催化剂,甲烷转化率达到98%以上。     

镍改性ZSM-5催化剂及其SCR催化性能

采用液态离子交换法制备了不同负载量的镍改性ZSM-5分子筛催化剂,并考察了上述催化剂的微观结构和物理化学特性及其在NH3-SCR反应中的催化性能。结果表明:在负载量<10.9%时镍在分子筛中具有高度的分散性,而随着镍负载量的进一步增加,分子筛表面开始出现较大的NiO颗粒;镍元素只以+2价存在于分子筛催化剂中;在NH₃-SCR反应中,镍负载量低于14.9%时,增加镍负载量将提高催化剂的低温活性;当反应温度超过300℃时,高温催化中心开始起作用,但随镍负载量的增加,高温活性开始下降时的温度逐渐降低。     

Morphological investigation of nanostructured CoMo catalysts

This work reports the morphological investigation of nanostructured sulfided CoMo catalysts by means of high-resolution transmission electron microscopy (HRTEM). The catalysts were supported on Ti-modified hexagonal mesoporous silica (HMS-Ti) and P-modified HMS-Ti (P/HMS-Ti) materials. The oxide precursors were characterized by specific surface area (S_BET), temperature-programmed reduction (TPR), diffuse reflectance infrared Fourier transform spectroscopy in the OH region (DRIFTS-OH) and X-ray photoelectron spectroscopy (XPS) in order to elucidate the influence of the impregnation sequence (successive vs. simultaneous) and the effect of P-incorporation into HMS-Ti material on the morphology of calcined CoMo catalysts. Both TPR and XPS measurements indicate that the catalysts prepared by successive impregnation possess well-dispersed MoO₃ and CoO phases, whereas their counterparts prepared by simultaneous impregnation additionally possess the CoMoO₄ phase. For all sulfided catalysts, the presence of MoS₂ phase with particle size in the range 3.3-4.4 nm was confirmed by HRTEM. Catalytic activity was evaluated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) carried out in a flow reactor at 593 K and hydrogen pressure of 5.5 MPa. P-incorporation into the HMS-Ti material led to an overall increase in HDS activity and the hydrogenation ability of the sulfided catalysts. All catalysts proved to be stable during 10 h time-on-stream (TOS) operation. The activity of sulfide catalysts in the target reaction depends linearly on the surface exposure of Co species in the oxide precursors, as determined by XPS, and on the morphology of the sulfide form of catalysts (surface density of MoS₂ particles and their sizes) as determined by HRTEM.     

Pd-Cu双金属催化剂上加氢反应的仲氢诱导超极化研究

本文通过多相催化-仲氢诱导超极化（HET-PHIP）核磁共振（NMR）技术研究了Pd-Cu/SiO₂双金属催化剂上丙炔选择性加氢反应.首先利用等体积浸渍法和连续浸渍法合成了一系列不同Pd/Cu比例和形貌的Pd-Cu/SiO₂双金属催化剂.通过ALTADENA（Adiabatic Longitudinal Transport After Dissociation Engenders Net Alignment）方法发现,催化剂的Pd/Cu比例和形貌均对PHIP的极化效率有较大影响.随着Pd-Cu双金属催化剂中Pd比例的增大,PHIP极化效率降低,同时反应活性增强.在同Pd/Cu比例下,相对于等体积浸渍法,连续浸渍法制备的层叠形貌催化剂具有较弱的极化效率以及较强的催化活性,这是由于催化剂表面暴露出的Pd数量增多,导致催化活性增强;同时单个Pd集簇表面积增大,使得氢原子移动范围扩大,从而造成极化效率降低.     

Investigation of PdSn-catalysts for nitrate removal in drinking water processing

PdSn catalysts prepared by various methods and used for nitrate reduction were investigated by means of in situ _119mSn Mössbauer spectroscopy. Characterization by ^119mSn Mössbauer spectroscopy revealed significant differences concerning the modification of the palladium particles supported on alumina. The controlled surface reaction preparation method (CSR) leads to formation of PdSn alloys with different tin contents besides small amounts of Sn(II) species and unalloyed metallic Sn. On the other hand the impregnation method leads to a small amount of PdSn alloys and higher contents of Sn(II) species. Sn(IV) species were found in both kinds of catalysts. The CSR prepared PdSn catalysts showed an improved activity and selectivity compared to the catalysts obtained by the impregnation method.     

Removal of recalcitrant pollutants from wastewater

Triton X-100 was oxidized in aqueous solutions with the presence of O₂ using photocatalysis and H₂O₂ addition alone or coupled. New supported TiO₂/Al₂O₃ catalysts modified with vanadium and cobalt were used. Catalysts were prepared using the classical impregnation method (CIM) and the double impregnation method (DIM). The effect of the physico-chemical properties of the catalysts on its activity were studied. The research on the interactions between the metal precursor and the titania-alumina surface by means of FT-IR/PAS (Fourier transform infrared photoacoustic spectroscopy) were also conducted.     

Enhancement of catalytic activity in NH3-SCR reaction by promoting dispersibility of CuCe/TiO2-ZrO2 with ultrasonic treatment

A series of CuCe-modified TiO₂-ZrO₂ catalysts synthesized by stepwise impregnation method and ultrasonic-assisted impregnation method were investigated to research the removal of NO in the simulated flue gas. Results showed that the CuCe/TiO₂-ZrO₂ catalyst prepared by ultrasonic-assisted impregnation method exhibited the superior NO conversion, in which higher than 85% NO was degraded at the temperature range of 250–400 °C and the highest NO conversion of 94% at 350 °C. It proves that ultrasonic treatment can markedly improve the performance of catalysts. The effect of ultrasonic enhancement on CuCe/TiO₂-ZrO₂ was comprehensively studied through being characterized by physicochemical characterization. Results reveal that the ultrasonic cavitation effect improves the distribution of active species and the synergistic interaction between Cu with Ce components (Cu⁺ + Ce⁴⁺ ↔ Cu²⁺ + Ce³⁺) on the catalysts significantly, thus resulting in better dispersibility as well as a higher ratio of Cu²⁺ and Ce³⁺ of the catalysts. Moreover, it was found that the CuCe/TiO₂-ZrO₂ catalyst prepared by the ultrasonic-assisted impregnation method represented a higher degree of ultrafine metal particles and evenness. The above results were described with the generalized dimension and singularity spectra in multifractal analysis and validated by the comparative test. Therefore, it can be concluded that ultrasonic treatment facilitates the particle size and distribution of active sites on the catalysts.     

NMR imaging study of various stages of a supported catalyst preparation process: getting the qualitative and quantitative information

Supported metal and metal oxide catalysts are widely used to perform various industrial processes such as hydrogenation reactions, the Fischer–Tropsch synthesis, hydrotreatment, etc. The preparation of such catalysts often involves impregnation of a porous support with a solution containing a desired metal salt (the precursor of an active component) followed by drying, calcination, and reduction. The properties of the obtained in such a way supported catalysts depend significantly on the dispersion and distribution of the active component along the catalyst pellet radius. In this paper nuclear magnetic resonance (NMR) imaging was applied to visualize the distribution of the active component (metal) in catalyst pellets in various stages of their preparation (impregnation, drying, calcination). The possibility to get by NMR imaging the quantitative information on the distribution of the active phase in impregnated, dried, and calcined catalysts was also demonstrated on the example of the Co/γ-Al₂O₃ catalyst. The preparation conditions leading to various (uniform, egg-shell, egg-white and egg-yolk) Co distributions in the calcined Co/γ-Al₂O₃ catalysts were determined.     

XPS and XRD investigation of Co/Pd/TiO2 catalysts by different preparation methods

In the article, the Co/Pd/TiO₂, Co/TiO₂ and Pd/TiO₂ catalysts prepared by the impregnation and sol–gel method are studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The result shows that Co²⁺ and metal Pd may act as the active center for the direct synthesis of acetic acid from CH₄ and CO₂ by a two-step reaction sequence. When the catalysts are prepared by the sol–gel, Co²⁺ can enter the crystal lattice of the TiO₂, causing the phase transition from anatase to rutile at lower temperature, but existence of Pd²⁺ can prevent from the phase transition. When the catalysts are prepared by the impregnation, the phase transition is inhibited not only Co²⁺ but also Pd²⁺.     

Synthesis of Pt modified ZSM-5 and beta zeolite catalysts: influence of ultrasonic irradiation and preparation methods on physico-chemical and catalytic properties in pentane isomerization

Influence of preparation methods and ultrasound irradiation on physico-chemical and catalytic properties was investigated by synthesizing Pt-ZSM-5 and Pt-Beta catalysts by in-situ and impregnation methods and applying ultrasound irradiation to synthesis gel mixture of ZSM-5 and Beta zeolites. It was concluded from the X-ray powder diffraction patterns of Pt-ZSM-5 and Pt-Beta zeolite catalysts that introduction of Pt by in-situ method and ultrasound irradiation did not influence the structures of ZSM-5 and Beta zeolites. Morphology of ZSM-5 and Beta zeolites were investigated by scanning electron microscopy. SEM micrographs showed that the Pt-ZSM-5-IS-US catalyst synthesized by in-situ method with ultrasound irradiation resulted in smaller crystals of ZSM-5 than Pt-ZSM-5-IS catalyst prepared without ultrasound irradiation. Furthermore SEM micrographs of Pt-Beta-11-IS-US zeolite synthesized using ultrasound irradiation showed much smaller crystals than Pt-Beta-11-IM indicating that ultrasound irradiation had a significant effect on the morphology of Beta zeolite. Conversion of n-pentane and selectivity to iso-pentane over the Pt-ZSM-5-IS-US zeolite catalysts prepared by ultrasound irradiation during in-situ introduction of platinum was higher than the catalysts prepared without the ultrasound irradiation. Furthermore ultrasound irradiated and in-situ synthesized Pt-Beta-11-IS-US catalyst also showed higher selectivity to iso-pentane than Pt-H-Beta-11-IM prepared by impregnation method.     

纳米固体超强酸的制备及表征

本文采用不同的金属离子(Sn2+,Sn4+,Al3+,Ag+,Ni2+)和SO2-4浸渍ZrO(OH)2的方法制备了一系列金属改性的SO2-4/ZrO2的纳米固体超强酸。并通过指示剂法测定其酸强度,用IR、BET、XRD、TEM及化学分析等多种试验手段对催化剂进行表征,并通过正己烷裂解反应考察了该类固体超强酸催化剂的催化活性。结果发现:不同的金属离子掺杂制得的改性SO2-4/ZrO2催化剂具有不同的性能。Sn2+、Sn4+和Al3+掺杂的超强酸有较强的酸性,但只有Ni2+、Sn2+掺杂的SO2-4/ZrO2样品具有正己烷裂解反应活性,Ag+、Sn4+掺杂改性的SO2-4/ZrO2样品不具有正己烷裂解活性。