柠檬酸溶胶-凝胶法制备Cu-ZnO-ZrO_2催化剂:pH对其性能的影响

采用溶胶-凝胶法以硝酸盐、柠檬酸为原料,加入氨水调节溶液pH,制备出一系列Cu-ZnO-ZrO_2催化剂。并通过粉末XRD、热重-差示扫描量热分析(TG-DSC)、N_2吸附-脱附(BET)、氢气程序升温还原(H_2-TPR)、CO_2程序升温脱附(CO_2-TPD)、SEM、TEM及傅里叶变换红外光谱(FTIR)对干凝胶及催化剂进行了理化性能测试,并在高温高压固定床反应器上进行催化剂活性评价。讨论了溶液pH对干凝胶结构及催化剂性能的影响。结果表明:pH为0.5制备得到的干凝胶中存在未配位的游离羧酸,又有部分羧酸通过羧基与金属离子进行了配位,而pH为4、6、8、10制备得到的干凝胶中不存在游离羧酸,羧酸均通过羧基与金属离子进行了配位。pH的改变调控着Cu~(2+)、Zn~(2+)、Zr~(4+)与柠檬酸之间的配位能力,pH为6时制备得到的催化剂具有较大的比表面积以及铜分散度,比表面积为92.5 m~2/g,铜分散度为18.63%,并表现出较好的CO_2加氢合成甲醇催化性能,CO_2转化率为24.7%,甲醇选择性为42.3%。     

溶胶-凝胶法制备Cu-ZnO-ZrO2催化剂：柠檬酸用量对催化剂性能的影响

采用溶胶-凝胶法以铜、锌、锆硝酸盐和柠檬酸为原料，改变柠檬酸用量，制备出一系列Cu-ZnO-ZrO₂催化剂。通过X射线衍射仪（XRD）、热重分析仪（TG-DTG-DTA）、H₂程序升温还原（H₂-TPR）、CO₂程序升温脱附（CO₂-TPD）、红外光谱仪（FTIR）及BET比表面积等表征手段对干凝胶及催化剂理化性能进行测试，并在催化反应活性评价装置上对催化剂的CO₂加氢合成甲醇反应活性进行评价，研究凝胶过程中Cu²⁺、Zn²⁺、Zr⁴⁺与柠檬酸结合方式对催化剂性能的影响。结果表明：改变柠檬酸用量可调控Cu²⁺、Zn²⁺、Zr⁴⁺与羧酸的配位方式，配位能力较强的Cu²⁺、Zn²⁺在凝胶制备过程中参与三维网络的构筑，而配位能力相对较弱的Zr⁴⁺游离于三维网络之外，从而差异化地调控催化剂中活性组分CuO、ZnO、ZrO₂晶粒尺寸大小。当柠檬酸的摩尔量为金属离子摩尔量的1.5倍时，催化剂中的活性成分CuO、ZnO、ZrO₂晶粒尺寸相互匹配，表现出较好的CO₂加氢合成甲醇催化性能。     

制备方法对CuO-ZnO-ZrO_2低温催化CO氧化性能的影响

采用不同制备方法(共沉淀法、柠檬酸络合法、溶胶凝胶法、模板剂法及均匀沉淀法)制备了Cu O-Zn O-Zr O2催化剂,考察了制备方法对催化剂物化性能及CO氧化性能的影响。通过X射线衍射、N2吸附-脱附、氢气程序升温还原等对制备的催化剂进行表征,结果表明,共沉淀法制备的催化剂比表面积和孔容积最大,分散度最高,平均晶粒尺寸最小。在CO氧化反应中,共沉淀法制备的样品CO低温氧化活性最高,连续反应100 h,稳定性能良好。在50℃、3 MPa的工况条件下,可将液相丙烯中CO体积分数脱除低至2×10-8,达到聚合级烯烃对CO脱除深度的要求。     

镧改性Cu-Fe/SiO2催化剂对合成气制备低碳醇的影响

采用超声辅助浸渍法制备La-Cu-Fe/SiO2催化剂,考察稀土元素La对Cu-Fe/SiO2催化剂的催化性能影响。通过X射线衍射(XRD),氮气吸附-脱附,CO的程序升温脱附(CO-TBD),程序升温还原(H2-TPR)等测试技术对La-Cu-Fe/SiO2催化剂进行表征,并利用合成气制备低碳醇反应评价其催化性能。试验结果表明,Cu-Fe/SiO2催化剂加入稀土元素La后,有助于改善活性中心的分散程度,增大催化剂的比表面积,提高反应物CO的吸附浓度,减小活性中心的还原损失,从而促进C2 醇的生成,有效降低产物的甲醇含量。     

钒钛催化剂制备方法对甲醇氧化制二甲氧基甲烷反应性能的影响

分别用快速燃烧法(RC)、共沉淀法(CP)、浸渍法(IM)和机械混合法(PM)制备了钒钛催化剂,并将其应用于甲醇氧化一步法合成二甲氧基甲烷的反应中.同时采用X射线衍射(XRD)、N2吸附/脱附(BET)、NH_3程序升温脱附(NH_3-TPD),H_2程序升温还原(H_2-TPR)等多种手段对催化剂进行了表征.结果表明RC催化剂上钒的分散度最高,酸中心数最多,同时氧化还原能力较强.甲醇氧化反应结果表明.RC催化剂上甲醇转化率和DMM选择性最高,这可能与RC上较高的钒分散度,较强的氧化还原能力和较多的酸性中心数有关.     

CuO-ZnO-γ-Al_2O_3催化剂的制备及应用

采用液相沉淀包覆法制备了以γ-Al2O3为核相的CuO-ZnO-γ-Al2O3复合催化剂,考察了不同制备方法对复合催化剂结构性质的影响。采用X射线衍射(XRD)、CO2程序升温脱附(CO2-TPD)和N2吸附脱附(BET)等手段对几种复合催化剂进行了分析表征。结果表明,制备方法对复合催化剂物化性质影响较大。采用传统共沉淀法制得的复合催化剂γ-Al2O3结晶度,比表面积及表面碱性均较低,而采用液相沉淀包覆法制得的复合催化剂γ-Al2O3结晶度较好,具有较大的比表面积和总碱量。     

甲醇水蒸气重整制氢CuZnAl催化剂的制备和研究

采用机械化学法制备了用于SRM反应的CuZnAl催化剂,并通过N2吸-脱附、N2O滴定、SEM、XRD、H2-TPR及原位FT-IR等手段对催化剂进行表征,对不同方法所制备催化剂的结构和性能进行了研究.结果表明:球磨法制备的CuZnAl催化剂形成较为规整的表面介孔结构,与浸渍法相比,具有较高的Cu比表面积和分散度,在SRM反应中CuZnAl催化剂较浸渍法制备的JZ-CuZnAl催化剂展现出更为优异的催化性能,当空速为58464 mL·(g·h)-1、进料水醇摩尔比为3:2、反应温度为300℃条件下,甲醇转化率达到81.2％,重整气中CO的体积分数为1.2％.     

沉淀剂对ZnCr氧化物催化剂合成异丁醇性能的影响

为开发高选择性和稳定性的异丁醇合成催化剂,选用了不同的沉淀剂,通过共沉淀法制备了系列ZnCr基氧化物催化剂。采用N_2吸附-脱附、X射线衍射(XRD)、程序升温还原(H_2-TPR)等手段对催化剂织构参数、体相结构、还原性能等进行表征,并研究了其CO加氢制异丁醇的催化性能。表征数据表明:使用碱性较弱的沉淀剂时,制得的催化剂比表面积较大,ZnO和Cr_2O_3形成非计量比尖晶石Zn_xCr_(2/3(1-x))O结构,且颗粒分散度较好,被还原能力较强。使用强碱性沉淀剂时,制得的催化剂比表面积较小,出现相分离现象,且被还原能力较差。研究结果表明,使用(NH_4)_2CO_3沉淀剂制备的ZnCr催化剂表现出了最佳的催化性能。该催化剂在390℃,10000h~(-1),12MPa时,CO单程转化率可达15.3%,醇选择性90.3%,异丁醇选择性33.5%。     

柠檬酸改性制备NiCu/SAPO-11催化剂及其加氢性能

为了研究柠檬酸对NiCu/SAPO-11催化剂的结构和临氢异构性能影响,通过柠檬酸改性制备一系列的NiCu/SAPO-11催化剂。采用X射线衍射(XRD)、N_2吸附-脱附、NH_3程序升温脱附(NH_3-TPD)、透射电子显微镜(TEM)和氢气程序升温还原(H2-TPR)等技术对催化剂进行表征。以正十六烷(n-C_(16))为模型化合物,研究催化剂在固定床反应器中的临氢异构性能。结果表明,柠檬酸改性可以增强金属的分散性,可以使催化剂具有更大的比表面积和孔体积,暴露出更多的酸性位点,从而增加催化剂的催化活性。在温度为340℃、空速为1.5 h~(-1)、压力为1.5 MPa、氢气和n-C_(16)体积比V(H_2):V(n-C_(16))为1 000的条件下,正十六烷的转化率,异构十六烷(i-C_(16))的选择性和收率分别为95.67%,94.89%和90.78%。     

氯对Pt-Sn-K/γ-Al_2O_3催化剂及其性能的影响

制备了不同氯含量的Pt-Sn-K/γ-Al_2O_3催化剂,利用X射线荧光光谱仪(XRF)、低温氮吸附-脱附法、氨-程序升温脱附法(NH_3-TPD)、氢气程序升温还原法(H_2-TPR)、热重(TG)分析等手段考察了氯含量对Pt-Sn-K/γ-Al_2O_3催化剂物性、表面酸性、铂分散度等的影响。通过异丁烷脱氢反应,考察氯对催化剂脱氢性能及积炭的影响。结果表明:适宜的催化剂表面酸性能够提高催化剂的性能,当氯质量分数为0.9%时,催化剂表现出较高的活性和选择性。     

铈锆固溶体担载的镍催化剂对CO2甲烷化性能研究

采用共沉淀法制备了Ce_xZr_1-xO₂固溶体作为催化剂载体，采用柠檬酸络合法将镍负载于Ce_xZr_1-xO₂载体上得到Ni/Ce_xZr_1-xO₂催化剂，利用X射线衍射（XRD）、N₂吸附-脱附（N₂-BET）、程序升温脱附（TPD）、程序升温还原（TPR）等技术对催化剂进行表征，在常压微型固定床反应器上测试了CO₂甲烷化的性能，考察了n（Ce）/n（Zr）、镍含量对催化性能的影响。研究发现制备的催化剂具有优异的活性，在常压和空速15 000 mL·g^-1·h^-1条件下，反应温度200℃时，12% Ni/Ce_0.25Zr_0.75O₂催化剂（负载量为质量分数，下同）CO₂的转化率达74%，CH₄选择性为100%。12% Ni/Ce_0.25Zr_0.75O₂催化剂300 h的稳定性测试结果显示其具有较高的抗烧结性能。催化剂的优异活性归因于采用了新的负载方法--柠檬酸络合法负载活性组分镍，该法实现了镍的高分散和催化剂的大的比表面积。     

Optimization of Effective Sol‐Gel Parameters for the Synthesis of Mesoporous γ‐Al2O3 Using Experimental Design

Mesoporous nanocrystalline γ‐alumina was prepared by a template‐free sol‐gel method using aluminum ethoxide as precursor. Significant parameters, such as the water/aluminum ethoxide molar ratio, the pH of the solution, and the time and temperature of aging, were optimized by the Taguchi method to obtain γ‐alumina with a high surface area and pore volume. The influences of the main parameters on the catalytic performance of the prepared catalysts were investigated via dehydration of methanol to dimethyl ether in a fixed‐bed reactor. The catalysts were characterized by X‐ray diffraction, N₂ adsorption‐desorption, ammonia temperature‐programmed desorption, and scanning electron microscopy techniques. The results show that the aging temperature had a significant influence on the catalyst performance.     

Adsorption behavior of NO and CO and their reaction over cobalt on zeolite beta

Adsorption behavior of NO and CO as well as their reaction was investigated on cobalt supported zeolite beta (Co/BEA) prepared by solid-state ion exchange (SSIE) and by impregnation (IMP). By temperature programmed desorption (TPD), two NO desorption peaks at 100 and 260‡C were observed over both SSIE and IMP catalysts with complete desorption after 450‡C. CO desorbed from SSIE catalyst between 50 and 200‡C. In the same temperature interval negligible CO₂ desorption was observed, most likely due to reaction of CO with trace of cobalt oxides. Over IMP catalysts, desorption of CO₂ was found mainly at 500‡C. By comparing CO TPD profiles from physical mixtures of cobalt oxides and HBEA, SSIE catalysts most likely contained cobalt cations in zeolite exchange position while IMP catalysts had cobalt in oxidic forms. The SSIE catalysts were active for NO reduction at 400 and 500‡C with a maximum conversion at 500‡C. However, the activity in the presence of water and oxygen was low. Water might inhibit the reaction by blocking active sites for NO and CO, while oxygen reacted with CO to form carbon dioxide. The activity of SSIE was better than IMP catalyst.     

Acid and base characteristics of molybdenum carbide catalysts

The acid and base properties of a high surface area Mo₂C catalyst were characterized using the temperature programmed desorption of CO₂ and NH₃, the decomposition of isopropyl alcohol (IPA) as a test reaction and monitoring changes in the associated rates and product selectivities on the addition of acid and base site poisons. The Mo₂C catalyst was prepared using the temperature programmed reaction method and passivated prior to exposure to air. Prior to carrying out the temperature programmed desorption experiments and reaction rate measurements, the Mo₂C catalyst was reduced in H₂ at 400 °C. Results obtained for the reduced Mo₂C catalyst were compared with those for MgO, HZSM-5 and 1% Pt/SiO₂ catalysts. The study provided evidence for the presence of both acid and base sites on Mo₂C. The base and acid sites on the Mo₂C catalyst were weaker than those on the MgO and HZSM-5 catalysts, respectively. The base and acid sites were likely created as a consequence of charge transfer from molybdenum to carbon.     

钒钛基SCR脱硝催化剂碱土金属中毒

分别制备了钒钨体系和钒钼体系的新鲜催化剂,并通过浸渍法、固态扩散法与干混法分别制备了碱土金属中毒的催化剂,比较了中毒方法、碱土金属以及催化助剂种类等因素对催化剂脱硝活性的影响,并利用程序升温脱附（NH₃-TPD）、程序升温还原（H₂-TPR）和X射线光电子能谱分析（XPS）等表征手段进行分析。结果表明,3种中毒方法中,浸渍法碱土金属中毒对催化剂毒害作用最大;Ca对催化剂的毒性大于Mg,且钒钼体系催化剂比钒钨体系催化剂具有更强的抗碱土金属中毒性能。碱土金属的存在会降低催化剂表面的总酸量与酸位点的强度,提高催化剂的还原温度,改变活性组分的价态并降低催化剂上表面活性氧的比例。     

Crude bio-glycerol as a hydrogen source for the selective hydrogenation of aromatic nitro compounds over Ru/MgLaO catalyst

Crude glycerol has been utilized as a hydrogen source for the selective hydrogenation of aromatic nitro compounds over MgLaO, MgO and La₂O₃ supported Ru catalysts. Ru dispersion and basicity of the catalysts had strongly influenced the turnover rates of aromatic amines. The catalyst was recovered and reused for 5 recycles without significant loss of activity. The physicochemical properties of the catalysts were rationalized by temperature programmed desorption (TPD) of CO₂ and CO pulse chemisorption in conjunction with rates of aromatic amines.     

A novel method for enhancing on-stream stability of fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst: Post-treatment of HZSM-5 zeolite by combined steaming and citric acid leaching

This article describes a novel modification method consisting of steaming and subsequent citric acid leaching to finely tune acidity and pore structure of HZSM-5 zeolite and thereby to enhance the on-stream stability of the zeolite derived fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst. A series of dealuminated HZSM-5 zeolites and their derived catalysts were prepared and characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), ²⁷Al MAS NMR, nitrogen adsorption, temperature programmed desorption of ammonium (NH₃-TPD) and infrared (IR) spectroscopy of chemisorbed pyridine. The results showed that the citric acid leaching could preferentially remove the extra-framework Al (EFAl) species formed by steaming treatment and thus reopen the EFAl-blocked pore channels of the steamed zeolite. The steaming treatment at a suitable temperature and subsequent citric acid leaching not only decreased the strength of acid sites to a desirable degree but also increased the ratio of medium and strong Lewis acidity to medium and strong Brönsted acidity, both of which conferred the resulting catalyst with superior selectivity to aromatics, good hydroisomerization activity and gasoline research octane number (RON) preservability, as well as enhanced on-stream stability. The results fully demonstrated that the treatments by steaming and followed citric acid leaching can serve as an important method for adjusting the physicochemical properties of HZSM-5 zeolite.     

Mixed Alcohol Synthesis from Syngas on K–Co–Mo/C Catalyst Prepared by a Sol–Gel Method

A kind of K–Co–Mo/C catalyst with homogenous components distribution and small particle size was prepared by sol–gel method with citric acid as complexant. Its structure and catalytic performance for mixed alcohol synthesis were investigated. By heat treating the dried gel in argon, the decomposition of citric acid resulted in the formations of amorphous carbon and low-valence MoO₂ species. The incorporation of potassium and cobalt increased significantly the alcohol synthesis activity, especially improved the C₂₊OH selectivity. The optimal atomic composition of catalyst was: 0.10 K: 0.50 Co: 1.0 Mo. Comparing with the similar catalysts reported in literatures, the sol–gel derived K–Co–Mo catalyst showed better performance, especially much higher C₂₊OH selectivity for mixed alcohol synthesis. A 150 h reaction test indicated that the catalyst had good stability during the entire experimental period. It suggested that the homogenous components distribution and small particle size enhanced the synergistic effect of promoters and created more active species, leading to a high catalytic performance. The formation of MoO₂ species was also favorable to improve the catalytic activity because the low-valence Mo⁴⁺ was known to be more active in CO hydrogenation.     

An investigation into the effect of Cs promotion on the catalytic activity of NiO in the direct decomposition of N2O

A series of Cs promoted NiO catalysts have been prepared and tested for direct decomposition of N₂O. These catalysts are characterized by BET surface area, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of N₂O (TPD-N₂O) and X-ray photo electron spectroscopy (XPS). The Cs promoted NiO catalysts exhibit higher activity for the decomposition of N₂O compared to bulk NiO. The catalyst with Cs/Ni ratio of 0.1 showed highest activity. The enhancement in catalytic activity of the Cs promoted catalysts is attributed to the change in the electronic properties of NiO. The characterization techniques suggest weakening of Ni–O bond thereby the desorption of oxygen becomes more facile during the reaction. The Cs promoted NiO catalyst is effective at low reaction temperature and also in the presence of oxygen and steam in the feed stream. IICT Communication No: 070523.