CuCl2和HY分子筛的表面反应及Cu/Y分子筛的制备及其催化甲醇氧化羰基化

以CuCl₂为前驱物与HY分子筛进行固相离子交换制备了Cu/Y催化剂,采用热重方法研究了CuCl₂与HY分子筛的表面固相离子交换反应,结合活性测试表明催化剂中高度分散的CuCl和离子交换形式的Cu⁺物种是甲醇氧化羰基化合成碳酸二甲酯的催化活性中心。X射线光电子能谱表征和元素分析结果表明,活性金属Cu主要以CuCl形式存在于分子筛外表面,而在分子筛笼内则以交换的Cu⁺和少量吸附的CuCl形式存在。与以CuCl为交换铜源所制催化剂相比,以CuCl₂为铜源制备的催化剂Cu含量低,催化活性更高。     

Cu/NiO-V2O5/SiO2催化剂光催化CO2和甲醇合成碳酸二甲酯的研究

采用表面改性法和等体积浸渍法制备了NiO-V₂O₅/SiO₂和Cu/NiO-V₂O₅/SiO₂光催化剂. 用TPR, XRD, UV-Vis DRS, IR和TPD-MS技术对催化剂的结构、吸光性能和化学吸附性能进行了表征, 研究了催化剂上CO₂和甲醇光促表面催化反应的反应性能. 结果表明, 半导体NiO和V₂O₅复合后部分形成了Ni^2＋—O—V^5＋键联, 而且NiO和V₂O₅在催化剂表面有相互修饰作用, NiO的加入有助于提高V₂O₅在载体SiO₂表面的分散程度, 抑制V₂O₅的聚集, 而且金属Cu和NiO的引入扩展了催化剂的光响应范围. 在催化剂表面存在多种活性吸附位, 催化剂对CO₂和甲醇的有效吸附使得其在较低温度下就能促进碳酸二甲酯的紫外光化学合成. 用Cu/NiO-V₂O₅/SiO₂催化剂, 在常压、空速300 h^－1、140 ℃和125 W紫外灯辐照的情况下, CH₃OH的转化率为14.2%, 碳酸二甲酯的选择性可达89.9 %.     

二苯并噻吩和吲哚在NiMoS/γ-Al2O3上加氢脱硫和加氢脱氮反应的相互影响

在固定床高压微反装置上考察了预硫化型NiMoS/γ-Al2O3催化剂上二苯并噻吩（DBT）加氢脱硫（HDS）反应和吲哚加氢脱氮（HDN）反应之间的相互影响。结果表明,吲哚对DBT的加氢脱硫反应具有抑制作用,其中对加氢路径（HYD）比对氢解路径（DDS）的抑制作用强,温度升高后,吲哚的抑制作用减弱。吲哚对DBT加氢脱硫反应的抑制作用源于吲哚及其HDN反应的中间产物在活性位上的竞争吸附。DBT和原位生成的H2S促进了催化剂表面硫阴离子空穴（CUS）向B酸位的转化,从而提高1,2-二氢吲哚（HIN）分子中C(sp3)—N键的断裂能力,使得吲哚的转化率和产物中邻乙基苯胺（OEA）的相对含量增大。HDN活性相的形成虽然需要硫原子的参与,但是活性相的保持并不需要大量的硫原子,较高含量硫化物存在时加氢活性位减少,不利于脱氮反应。     

Atom-economy Synthesis of N-Substituted Carbamate from Urea Derivative and Dimethyl Carbonate Catalyzed by La/SiO_2: Characterization and Activity

A series of silica gel immobilized lanthanum catalysts were prepared for the atom‐economy synthesis of N‐substituted carbamates from urea derivatives and dimethyl carbonate. The La/SiO₂ catalysts with lanthanum loadings varied from 1.3 wt% to 8.5 wt% were characterized by AES, BET, XRD, TEM, FT‐IR, XPS and TPD. According to the characterization, lanthanum species with particle sizes of 5–10 nm on the surface of silica gel were formed. The catalysts were all amorphous and the surface areas were 336.5–530.2 m²/g. NH₃‐TPD analysis showed that all samples exhibited similar acid strength with different acid amounts. FT‐IR measurement indicated that the component of lanthanum species on the catalyst surface were La(OH)₃, LaOOH and hydrated La₂O₃. Also, the peak value of the absolute amount of LaOOH was obtained with 4.3 wt% lanthanum loading. The BET surface area decreased dramatically when the lanthanum loading was above 4.3 wt%. In consideration of the results obtained from the catalytic reactions, it could be concluded that LaOOH was the possible active species and high surface area was important for the high catalytic activity.     

TiO2-Al2O3载体的制备方法对其负载的磷化镍催化剂加氢脱氮反应性能的影响

采用共沉淀法和原位溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体,其负载的磷化镍催化剂采用等体积浸渍法和H₂原位还原法制备. 通过N₂吸附（BET）、X射线衍射（XRD）、透射电镜（TEM）、程序升温还原（TPR）,X射线光电子能谱（XPS）和等离子体发射光谱（ICP-AES）表征技术对催化剂进行了表征,并通过喹啉的加氢脱氮反应评价了催化剂的加氢脱氮性能. 结果表明,原位溶胶-凝胶法制成的复合载体基本保留了原有的γ-Al₂O₃的孔特征,具有较大的比表面积和较宽的孔分布,TiO₂主要以表面富集的形式分散在管状的γ-Al₂O₃表面,其负载的磷化镍催化剂还原后所形成的活性相为Ni₂P和Ni₁₂P₅;而共沉淀法制成的复合载体比表面积较小,孔径分布更加集中,TiO₂趋于在块状的Al₂O₃表面均匀分散,其负载的磷化镍催化剂具有更好的可还原性,还原后所形成的活性相为Ni₂P. 不同的载体制备方法和不同的钛铝比对催化剂加氢脱氮性能影响较大,当n（Ti）/n（Al）=1/8时,共沉淀法载体负载的催化剂表现出最佳的加氢脱氮性能,在340 ℃,3 MPa,氢油体积比500,液时空速3 h^-1的反应条件下,喹啉的脱氮率可以达到91.3%.     

表面覆盖SiO2用于提高Pt-Pd/CeO2-ZrO2-Al2O3商用柴油机氧化型催化剂的抗硫性

向Pt-Pd/CeO₂-ZrO₂-Al₂O₃ （Pt-Pd/CZA）商用柴油机氧化型催化剂（DOC）中加入多孔SiO₂以提高其抗硫性. 使用多层涂覆法在Pt-Pd/CZA 催化剂表面覆盖一层多孔SiO₂,从而制得SiO₂/Pt-Pd/CeO₂-ZrO₂-Al₂O₃（SiO₂/Pt-Pd/CZA）抗硫DOC. 并使用扫描电子显微镜（SEM）,H₂程序升温还原（H₂-TPR）,氮气吸脱附,X射线能谱（EDX）和热重分析（TGA）等对其进行表征. SEM结果显示,SiO₂层以多孔形式均匀覆盖在催化剂表面. 氮气吸脱附结果表明,所添加的SiO₂的织构性质与Pt-Pd/CZA 催化剂的织构性质相似,因而表面覆盖的SiO₂并未明显改变Pt-Pd/CZA催化剂的比表面积和孔结构. H₂-TPR结果证实表面覆盖的SiO₂不影响Pt-Pd/CZA催化剂的还原性能. EDX和TGA结果说明表面覆盖SiO₂可以抑制硫物种在催化剂表面的形成及累积. 最终,本文所制备的SiO₂/Pt-Pd/CZA催化剂在保持Pt-Pd/CZA商用DOC的高活性及耐久性的同时有效提高了其抗硫性.     

Cu/La2O3-ZrO2-Al2O3催化剂的制备及其对NO选择性还原的催化性能

采用将Al(NO3)3、La(NO3)3和ZrOCl2的混合液滴入沉淀剂(NH4)2CO3中的共沉淀法制备La2O3-ZrO2-Al2O3复合载体,然后负载上Cu2+,制成Cu/La2O3-ZrO2-Al2O3催化剂。考察了该催化剂在富氧条件下对C3H6选择还原NO的催化性能,并借助扫描电子显微镜（SEM）、X射线衍射（XRD）、比表面积测定（BET）、吡啶吸附红外光谱（Py-IR）、程序升温还原（TPR）和热重分析（TG）等方法研究催化剂制备方法与结构、性能的关系。实验结果表明,采用将Al(NO3)3滴入(NH4)2CO3制得的γ-Al2O3能有效地增大催化剂的比表面积,加入La2O3能提高催化剂的热稳定性,加入ZrO2能大幅度增加催化剂表面L酸和B酸的酸量。因此,采用共沉淀法制备的La2O3-ZrO2-Al2O3复合载体能够使Cu/La2O3-ZrO2-Al2O3催化剂具有良好的催化性能,最佳催化活性温度为300℃,NO最大转化率高达88.9%,在有10%水蒸气存在的情况下,仍可达81.9%。     

应用原位漫反射红外-质谱技术研究CuO/Al2O3催化剂表面酸性及其反应性能

应用原位漫反射红外-质谱联用、程序升温和暂态响应技术研究了CuO/Al₂O₃催化剂表面酸性及其反应性能. 实验结果表明, CuO/Al₂O₃催化剂表面呈Lewis酸性, 硫化不仅可增强CuO/Al₂O₃催化剂的Lewis酸性, 而且可产生新的Brønsted酸性位; 吸附于Lewis酸性位的NH₃具有选择性催化还原(SCR)活性. 而在硫化样Cu8(400S)中Lewis和Brønsted酸性位同时存在的情况下, 吸附于Lewis和Brønsted酸性位的氨均具有SCR活性, 且后者较前者弱; CuO/Al₂O₃催化剂上的SCR反应遵循Eley-Rideal机理, 即SCR反应发生于吸附态NH₃与气相NO之间.     

Co或Ni促进的Cu/SiO2-Al2O3催化剂上丙三醇和苯胺气相合成3-甲基吲哚

对丙三醇和苯胺在Co或Ni促进的Cu/SiO2-Al2O3催化剂上气相合成3-甲基吲哚进行了研究.采用N2吸附、氢气程序升温还原(H2-TPR)、电感耦合等离子体(ICP)发射光谱、X射线衍射(XRD)、透射电子显微镜(TEM)、氨程序升温脱附(NH3-TPD)及热重(TG)分析等技术对催化剂进行了表征.结果表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂改善了催化剂的催化性能,钴比镍更加有效.在催化剂Cu-Co/SiO2-Al2O3和Cu-Ni/SiO2-Al2O3上,反应第3 h,3-甲基吲哚收率分别达到47%和45%,而且催化剂经过6次再生收率仍能达到44%和42%.各种表征表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂能增强铜和载体之间的相互作用,其结果不仅促进了铜粒子在载体表面的分散度,而且有效减少了反应过程中铜组分的流失.另外,加入钴或镍助剂还能减少催化剂的中强酸中心数,从而提高3-甲基吲哚的选择性,并且抑制积炭的形成.此外,钴助剂还能增加催化剂的弱酸中心数,促进3-甲基吲哚的生成.提出了金属铜与弱酸中心共同促进3-甲基吲哚合成的催化反应机理.     

Al含量对Pt-SO2-4 /ZrO2-Al2O3固体超强酸催化

通过向SO^2-₄ /ZrO₂催化剂中同时引入适量的Pt和Al₂O₃, 制备出了具有较高催化性能和稳定性的Pt-SO^2-₄ /ZrO₂-Al₂O₃型固体超强酸催化剂. 以正戊烷异构化反应为探针, 考察了Al含量对催化剂性能的影响; 并采用X射线衍射(XRD)、比表面积测定(BET)、红外(IR)光谱、程序升温还原(TPR)、热重-差热分析(TG-DTA)和氨-程序升温脱附(NH₃-TPD)手段对催化剂进行了表征. 结果表明, Al能够提高ZrO₂的晶化温度, 抑制硫的分解, 增加催化剂的比表面积, 增强硫氧键的结合, 提高催化剂的还原性能, 增加催化剂的酸强度和酸总量. 当Al₂O₃含量(质量分数, w)为5.0%时, Pt-SO^2-₄ /ZrO₂-Al₂O₃固体超强酸催化剂的催化活性最好, 在100 h内异戊烷收率可稳定在52.0%以上, 选择性在98.2%以上.     

Study of CO2 Hydrogenation to Methanol over Cu-V/γ-Al2O3 Catalyst

The effect of vanadium addition to CU/γ-Al2O3 catalyst used in the hydrogenation of CO2 to produce methanol was studied. It was found that the catalytic performance of the Cu-based catalyst improved after V addition. The influence of reaction temperature, space velocity and the molar ratio of H2 to CO2 on the performance of 12%Cu-6%V/γ-Al2O3 catalyst were also studied. The results indicated that the best conditions for reaction were as follows: 240℃, 3600 h-1 and a molar ratio of H2 to CO2 of 3:1. The results of XRD and TPR characterization demonstrated that the addition of V enhanced the dispersion of the supported CuO species, which resulted in the enhanced catalytic performance of CU-V/γ-Al2O3 binary catalyst.     

α-Fe2O3/SiO2纳米颗粒混合体系表面的酸碱性质及其对重金属离子的吸附行为

以Fe(NO₃)₃·9H₂O和正硅酸乙酯(TEOS)为原料, 通过溶胶-凝胶法和辅助模板法分别制备了纳米α-Fe₂O₃和SiO₂, 并对所合成样品进行了粉末X射线衍射(XRD)和BET表征. 使用自动电位滴定仪测定了α-Fe₂O₃/SiO₂纳米颗粒混合体系的表面酸碱性质. 研究了在不同pH下α-Fe₂O₃/SiO₂混合体系对Cu²⁺、Pb²⁺、Zn²⁺离子的吸附行为. 基于上述实验数据, 用WinSGW软件计算了α-Fe₂O₃/SiO₂混合体系表面酸碱配位常数, 并得出结论: α-Fe₂O₃/SiO₂混合体系表面反应为单一脱质子反应≡XOH ⇔ ≡XO^-+ H⁺(lg K = -8.19±0.15), 明显区别于同时具有加质子和脱质子反应的α-Fe₂O₃/SiO₂/γ-Al₂O₃, α-Fe₂O₃/γ-Al₂O₃和SiO₂/γ-Al₂O₃等纳米颗粒混合体系. 在此基础上拟合得到α-Fe₂O₃/SiO₂混合体系吸附重金属离子Cu²⁺、Pb²⁺、Zn²⁺的表面络合反应平衡常数分别为:
≡XOH + M²⁺ ⇔ ≡XOM⁺+ H⁺ [lg K = -3.1, -3.6, -3.8 (M = Cu, Pb, Zn)].
≡XOH＋M²⁺＋H₂O ⇔≡XOMOH＋2H⁺[lg K = -8.8, -8.0, -10.5 (M = Cu, Pb, Zn)]     

Study on the formation and role of copper chloride hydroxide in the oxidative carbonylation of methanol to dimethyl carbonate

The synthesis of dimethyl carbonate by oxidative carbonylation of methanol over CuCl/SiO₂-TiO₂ catalysts has been investigated in a slurry reaction system. The γ-Cu₂(OH)₃Cl crystals were detected by X-ray diffraction on the catalysts after reaction. It was revealed that γ-Cu₂(OH)₃Cl was formed by CuCl reacting with O₂ and by-product water. The catalytic tests showed that γ-Cu₂(OH)₃Cl was largely inactive for this reaction, may be attributed to its high stability that resisted the Cu⁺/Cu²⁺ redox cycle.     

Surface acidity of supported vanadia catalysts

The surface acidity of SiO₂, γ-Al₂O₃ and TiO₂ supported vanadia catalysts has been studied by the microcalorimetry and infrared spectroscopy using ammonia as the probe molecule. The acidity in terms of nature, number and strength was correlated with surface structures of vanadia species in the catalysts, characterized by X-ray diffraction and UV-Vis spectroscopy. It was found that the dispersion and surface structure of vanadia species depend on the nature of supports and loading and affect strongly the surface acidity. On SiO₂, vanadium species is usually in the form of polycrystalline V₂O₅ even for the catalyst with low loading (3%) and these V₂O₅ crystallites exhibit similar amount of Brönsted and Lewis acid sites. The 25%V₂O₅/SiO₂ catalyst possesses substantial amount of V₂O₅ crystallites on the surface with the initial heat of 105 kJ mol^-1 and coverage of about 600 mmol g^-1 for ammonia adsorption. Vanadia can be well dispersed on g-Al₂O₃and TiO₂ to form isolated tetrahedral species and polymeric two-dimensional network. Addition of vanadia on γ-Al₂O₃ results in the change of acidity from that associated with g-Al₂O₃ (mainly Lewis sites) to that associated with vanadia (mainly Brönsted sites) and leads to the decreased acid strength. The 3%V₂O₅/TiO₂ catalyst may have the vanadia structure of incomplete polymeric two-dimensional network that possesses the Ti-O-V-OH groups at edges showing strong Brönsted acidity with the initial heat of about 140 kJ mol^-1 for ammonia adsorption. On the other hand, the 10%V₂O₅/TiO₂ catalyst may have well defined polymeric two-dimensional vanadia network, possessing V-O-V-OH groups that exhibit rather weak Brönsted acidity with the heat of 90 kJ mol^-1 for NH₃ adsorption. V₂O₅ crystallites are formed on the 25%V₂O₅/TiO₂ catalyst, which exhibit the acid properties similar to those for 25%V₂O₅ on SiO₂ and γ-Al₂O₃.     

Zr0.5Ti0.5O2的添加对超临界裂解RP-3催化剂性能的影响

采用共沉淀法制备了Zr_0.5Ti_0.5O₂载体材料,将其掺杂在CeO₂-Al₂O₃ (CA)基催化剂中, 并对其催化活性进行了超临界裂解测试, 采用全自动吸附仪、X射线衍射(XRD)、透射电镜(TEM)、程序升温脱附(TPD)等方法对催化剂进行了表征. 实验结果表明, 催化剂能够明显降低裂解反应的温度, 600 ℃ CA基催化剂产气率是热裂解的2.8倍, 掺杂Zr_0.5Ti_0.5O₂载体材料的CA基催化剂是热裂解的4.0倍, 650 ℃时, 掺杂Zr_0.5Ti_0.5O₂载体材料的CA基催化剂热沉提高了0.55 MJ·kg^-1. BET结果表明, 掺杂Zr_0.5Ti_0.5O₂载体后催化剂出现双孔结构, 部分小孔的出现使得乙烯的选择性提高; NH₃-TPD结果表明, 掺杂Zr_0.5Ti_0.5O₂载体材料后, 催化剂强酸位的酸量增加了4.0倍,催化剂表现出更强的表面酸性和更集中的强酸酸中心密度, 有利于裂解多产烯烃.     

Synthesis and characterization of Fe2O3/SiO2 nanocomposites

Fe₂O₃/SiO₂ nanocomposites based on fumed silica A-300 (S_BET = 337 m²/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)₃) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)₃ then oxidized in air at 400–900 °C. Samples with Fe(acac)₃ adsorbed onto nanosilica and samples with Fe₂O₃/SiO₂ including 6–17 wt% of Fe₂O₃ were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe₂O₃ deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)₃ solution in isopropanol) treated at 500–600 °C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)₃ solution in carbon tetrachloride only α-Fe₂O₃ phase is formed in addition to amorphous Fe₂O₃. The Fe₂O₃/SiO₂ materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15 g/cm³ and S_BET = 265–310 m²/g.     

La2O3/γ-Al2O3催化剂用于二甲醚二氧化碳重整制氢

采用等体积浸渍法制备了不同负载量的La₂O₃/γ-Al₂O₃催化剂,并考察了负载量和反应温度对催化剂用于二甲醚二氧化碳重整制氢反应的性能影响。结果表明,反应温度为550℃、La₂O₃负载量为15%时,催化剂表现出最好的性能：二甲醚的转化率为100%,二氧化碳的转化率达到85.4%,产物氢气的选择性高达93.3%,一氧化碳的选择性为76.04%,副产物甲烷的选择性仅为6.3%。550 ℃时其平均积炭速率为1.387 5 mg/（g·h）。研究还利用XRD、BET、TEM、TG等方法对催化剂进行了表征。     

Influence of Pd precursors on the catalytic performance of Pd–H4SiW12O40/SiO2 in the direct oxidation of ethylene to acetic acid

The effects of palladium precursors (PdCl₂, (NH₄)₂PdCl₄, Pd(NH₃)₂Cl₂, Pd(NO₃)₂ and Pd(CH₃COO)₂) on the catalytic properties in the selective oxidation of ethylene to acetic acid have been investigated for 1.0 wt% Pd–30 wt% H₄SiW₁₂O₄₀/SiO₂. The structures of the catalysts were characterized using X-ray diffraction, N₂ adsorption, H₂-pulse chemical adsorption, infrared spectrometry of the adsorbed pyridine, H₂ temperature-programmed reduction and X-ray photoelectron spectroscopy. The present study demonstrates that the different palladium precursors can lead to the significant changes in the dispersion of palladium. It is found that Pd dispersion decreases as follows: PdCl₂ > (NH₄)₂PdCl₄ > Pd(NO₃)₂ > Pd(NH₃)₂Cl₂ > Pd(C₂H₃O₂)₂, which is nearly identical to the catalytic activity. This indicates that the dispersion of palladium plays an important role in the catalytic activity. Furthermore, density of Lewis (L) and Brönsted (B) acid sites are also strongly dependent on the palladium precursors. It is also demonstrated that an effective catalyst should possess a well combination of Brönsted acid sites with dispersion of palladium.     

Characterization of ZrO2- Al2O3mixed oxides support prepared by urea hydrolysis

The characteristics of Al₂O₃, ZrO₂ and three binary mixtures of ZrO₂-Al₂O₃ were studied by determining their BET surface areas, micropore surface area, total pore volume, adsorption-desorption isotherms, the X-ray diffractogram, surface acidity and catalytic functionality for cumene cracking. The XRD results show that the incorporation of alumina into the zirconia from 50% and beyond renders it amorphous. Furthermore, the mixed oxide containing 50% alumina and 50% zirconia had the highest BET surface area of 199.9 m²/g whilst pure zirconia had the lowest BET surface area of 37.19 m²/g. The pores for all the mixed oxides were found to be monomodal and zirconia pores were more open. The results of the acidity measurements and cumene cracking functionality indicates that whilst pure zirconia has low total acidity, the incorporation of alumina increases its acidity through a synergistic effect. This revised version was published online in June 2006 with corrections to the Cover Date.