三氟甲磺酸盐催化甲苯硝化反应的研究

利用三氟甲磺酸盐作为新型的Lewis酸催化剂, 用于甲苯与等物质的量的硝酸的硝化反应. 通过对不同催化剂进行考察发现Zr(OTf)₄和Sm(OTf)₃的催化性能最好, 甲苯转化率分别达77.1%和67.4%. 使用98%硝酸能使转化率达100%, 而用甲苯作溶剂时转化率达95.4%. 对硅胶负载催化剂的考察发现硅胶负载催化剂Sm(OTf)₃能使甲苯转化率升至89.9%, 且异构体分布有所改变, 其o∶m∶p为44.6∶5.7∶49.7.     

吸附NOx的功能化硅胶用于催化温和条件下醇的选择性氧化

利用接枝方式将2,2,6,6-四甲基哌啶(TEMPO)固载到SPE柱填料硅胶上制备了功能化硅胶,其吸附NO_x应用于催化醇的选择性氧化反应中. 并利用元素分析、红外光谱、N₂吸附-脱附和NO_x程序升温脱附对催化剂进行了考察. 结果表明,所制备催化剂中TEMPO固载量为0.292 mmol/g,NO_x吸附量为0.749 mmol/g; 常温常压下1 mmol芳香醇在0.5g该催化剂作用下进行选择性氧化反应2h,原料转化率和产物选择性均高达99%. 该催化剂提高了醇分子在孔道内部与TEMPO和NO_x接触几率,促进了反应进行,根据反应现象,对该体系催化机理进行了推测.     

焙烧温度对MnOx-CeO2-WO3-ZrO2催化剂上NH3选择性还原NO的影响

采用共沉淀法制备了MnO_x-CeO₂-WO₃-ZrO₂催化剂,考察了催化剂焙烧温度对O₂和H₂O存在下NH₃选择性催化还原（NH₃-SCR） NO的影响,并利用低温N₂吸附、X射线衍射（XRD）、透射电镜（TEM）、X射线光电子能谱（XPS）、NH₃程序升温脱附（NH₃-TPD）和CO脉冲反应对催化剂进行了表征. 结果表明在NH₃-SCR反应中,催化剂的低温活性随焙烧温度的提高而降低,这是由于催化剂表面化学吸附氧和酸性位减少引起的;催化剂的高温活性随焙烧温度的提高先增加后减小,这与催化剂表面最易释放氧数量的变化趋势相反. 700 ℃焙烧的催化剂具有良好的低温活性和最宽的反应温度窗口,在空速为90000 h^-1的条件下,该催化剂的起燃温度（50% NO转化率）为189 ℃,且反应温度在218-431 ℃范围内,NO转化率可达到80%-100%.     

用原位红外技术研究Ag-MoO3/ZrO2催化丙烯气相环氧化反应

制备了对丙烯直接气相环氧化具有优良催化性能的Ag-MoO₃/ZrO₂催化剂, 采用原位FT-IR技术研究了丙烯、环氧丙烷及丙烯和氧气混合气在载体和催化剂上的吸附及反应行为. 研究表明, 丙烯在ZrO₂载体和20%Ag-4%MoO₃/ZrO₂催化剂上吸附后, 均不发生化学反应, 而环氧丙烷在ZrO₂载体上吸附后于400 ℃发生开环反应, 在20%Ag-4%MoO₃/ZrO₂催化剂上吸附后于300 ℃发生开环反应. 当丙烯和氧气混合气在ZrO₂载体上共吸附后, 随着反应温度从室温升高至400 ℃, 二者开始反应生成CO₂和H₂O; 混合气在20%Ag-4%MoO₃/ZrO₂催化剂上共吸附后于350 ℃开始反应. 对比非负载型Ag-MoO₃催化剂的研究结果可见, ZrO₂载体的存在使催化剂的活性下降的同时, 提高了对产物环氧丙烷的选择性.     

非负载型铁催化剂上二氧化碳加氢制低碳烯烃

研究了非负载型铁催化剂上CO₂加氢制低碳烯烃反应.结果显示,添加碱金属可显著提高铁催化剂上的CO₂转化率和烯烃选择性.在经K和Rb修饰的Fe催化剂上,CO₂转化率可达约40%,烯烃选择性达到50%以上,其中C₂~C₄烯烃收率超过10%.催化剂表征结果表明,碱金属促进了催化剂中碳化铁的生成,这可能是催化剂性能提高的一个关键原因.随着K含量由1 wt%增加至5 wt%,CO₂转化率及烯烃选择性均升高.但K含量过高时,催化剂活性降低.这可能是由于催化剂比表面积和CO₂化学吸附量降低所致.当K含量为5%~10%时,K-Fe催化剂上烯烃收率较高; 进一步添加适量的硼可进一步提高烯烃选择性,且CO₂转化率下降不大.     

生物质焦油组分甲苯在镍/凹凸棒石上的二氧化碳催化重整

 以大比表面积的天然纳米矿物材料凹凸棒石 (PG) 为载体, 采用等体积浸渍法制备了 Ni/PG 催化剂. 运用 X 射线衍射、透射电镜和 CO₂ 程序升温脱附对 Ni/PG 催化剂进行了表征, 并用于以甲苯为生物质焦油模型化合物的 CO₂ 催化重整反应. 考察了反应温度、CO₂ 浓度以及催化剂中 Ni 负载量对甲苯与 CO₂ 重整性能的影响. 结果表明, 吸附在催化剂表面的 CO₂ 存在三个脱附峰, 其中高温脱附 CO₂ 与反应密切相关; 随着 CO₂ 浓度、Ni 负载量和反应温度的增加, 甲苯转化率和 H₂ 产率升高. 在 800 ^oC, CO₂/PhCH₃ 摩尔比为 0.2~0.26 时, 甲苯转化率达最高; 而在 CO₂/PhCH₃ 摩尔比为 0.2 时, H₂ 产率最高. 催化剂上积炭量随 CO₂ 浓度的增加和反应温度的升高而显著降低.     

用原位红外技术研究Ag-MoO3/ZrO2催化丙烯气相环氧化反应

制备了对丙烯直接气相环氧化具有优良催化性能的Ag-MoO₃/ZrO₂催化剂, 采用原位FT-IR技术研究了丙烯、环氧丙烷及丙烯和氧气混合气在载体和催化剂上的吸附及反应行为. 研究表明, 丙烯在ZrO₂载体和20%Ag-4%MoO₃/ZrO₂催化剂上吸附后, 均不发生化学反应, 而环氧丙烷在ZrO₂载体上吸附后于400 ℃发生开环反应, 在20%Ag-4%MoO₃/ZrO₂催化剂上吸附后于300 ℃发生开环反应. 当丙烯和氧气混合气在ZrO₂载体上共吸附后, 随着反应温度从室温升高至400 ℃, 二者开始反应生成CO₂和H₂O; 混合气在20%Ag-4%MoO₃/ZrO₂催化剂上共吸附后于350 ℃开始反应. 对比非负载型Ag-MoO₃催化剂的研究结果可见, ZrO₂载体的存在使催化剂的活性下降的同时, 提高了对产物环氧丙烷的选择性.     

镍基催化剂：制备及水相催化糠醛加氢脱氧反应性能

以SiO₂-Al₂O₃、γ-Al₂O₃为载体采用浸渍法制备了不同负载量的镍基催化剂,以XRD、H₂-TPR、NH₃-TPD与低温N₂吸附等技术对催化剂特性进行了表征,并进行了水相催化糠醛加氢脱氧实验研究以制备以C₅为主要成分的生物汽油。重点考察了催化剂的镍负载量、载体种类及反应温度对糠醛转化率、目标产物C₅选择性的影响,并对催化剂的重复利用性能和糠醛水相加氢脱氧反应机理进行了探讨。结果表明,Ni/SiO₂-Al₂O₃催化性能明显优于Ni/γ-Al₂O₃。在140 ℃、氢冷压3.0 MPa的优化反应条件下,14wt% Ni/SiO₂-Al₂O₃催化糠醛反应的转化率为63%,C₅选择性高达93%。升高反应温度可以提高糠醛的转化率,但反应产物的选择性降低。催化剂在第3次重复使用时糠醛的转化率明显降低,催化剂表面有明显的残留有机聚合物和积碳,达到25wt%左右。     

SBA-15负载高分散纳米NiO的丙烷氧化脱氢制丙烯催化性能

采用浸渍法通过改变焙烧气氛制备了系列NiO/SBA-15 (w_NiO=20%)催化剂, 并考察了催化剂的丙烷氧化脱氢(ODHP)反应性能. 实验结果表明, 与在静止和流动空气中焙烧的催化剂相比, 在1%NO/He (V_NO/V_He=1:99)气氛中焙烧的NiO/SBA-15-NO具有优异的低温丙烷氧化脱氢制丙烯性能, 在350 ℃时, 丙烷的转化率和丙烯收率分别约达29%和13%. 反应温度升至450 ℃时, 丙烯的选择性仍保持在45%左右. X射线粉末衍射(XRD)和透射电镜(TEM)测试结果表明, 1%NO/He气氛可有效抑制焙烧过程中NiO纳米颗粒的团聚, 使NiO物种高分散于SBA-15 的孔道中. H₂-程序升温还原(H₂-TPR)和O₂-程序升温脱附(O₂-TPD)测试结果表明, 随着NiO在SBA-15上分散度的提高, 催化剂的抗还原性增强, ODHP活性氧物种O-的含量增加, 进而使1%NO/He气氛中焙烧的NiO/SBA-15-NO在较宽的温度范围内(350-450 ℃)均具有良好的丙烯选择性, 并显著提高了催化剂的低温活性.     

K2CO3含量对Ni-Cu-Mn-K/Al2O3水煤气变换催化剂结构和性能的影响

以γ-Al₂O₃为载体，采用等体积浸渍法，制备了不同K₂CO₃含量的Ni-Cu-Mn-K/Al₂O₃水煤气变换催化剂，采用低温N₂吸附、XRD、TPD和TPR，考察了K₂CO₃含量对催化剂结构和性能的影响。结果表明:K₂CO₃的加入使催化剂的还原温度有所提高，适量的K₂CO₃能增加活性组分的电子密度，从而增强其给电子活化CO的能力，提高催化剂的活性。但过量的K₂CO₃使得催化剂比表面积和孔容降低，且导致催化剂对CO吸附过强，催化活性降低。当Ni-Cu-Mn-K/γ-Al₂O₃催化剂中K₂CO₃的添加量为7.5%时，且催化剂经530 ℃耐热15 h后，在350 ℃时水煤气变换反应中CO转化率达62.29%。     

Hydroisomerization of n-heptane over bimetal-bearing H3PW12O40 catalysts supported on dealuminated USY zeolite

The bimetal-bearing (CePt or LaPt) 12-tungstophosphoric acid (H₃PW₁₂O₄₀ (PW)) catalysts supported on dealuminated USY zeolite (DUSY) were prepared by impregnation and characterized by XRD, BET, IR, and H₂-chemisorption. Their catalytic activities were tested in the hydroisomerization of n-heptane with a continuous atmospheric fixed-bed reactor. After the steam treatment combined with the acid leaching, as well as the supporting with PW and the bimetals, the DUSY support retains the Y zeolite porosity and the PW well keeps its Keggin structure in catalysts. The doping of Ce into the catalysts enhances the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Ce or La, especially Ce, exhibit much higher catalytic activity and selectivity than the catalysts without dopants at lowered reaction temperatures. At the optimal reaction conditions, i.e., the reaction temperature of 250°C and WHSV of 1.4 h⁻¹, the catalyst with a Pt loading of 0.4%, PW loading of 10% and a molar ratio of Ce to Pt of 15:1 shows a conversion of n-heptane of 70.3% with a high selectivity for isomerization products of 94.1%. Supported by the Natural Science Foundation of China (Nos. 20306011 and 20476046), the Ph. D. Program Foundation of Chinese University (20040291002), and the Ph. D. innovation Program Foundation of Nanjing University of Technology (BSCX200506)     

Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C₃-C₅ alcohols and for alkylation ofm-xylene bytert-butyl alcohol.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp, 2912–2917, December, 1996.     

Selective hydrogenation of o-chloronitrobenzene (o-CNB) over supported Pt and Pd catalysts obtained by laser vaporization deposition of bulk metals

Carbon nanotubes (CNTs), γ-alumina (γ-Al₂O₃) and silica (SiO₂) supported Pt and Pd catalysts were produced by laser vaporization deposition of respective bulk metals. The catalysts were characterized by inductive coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic properties of the catalysts were investigated in the liquid phase hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) under 333 K and 1.0 MPa hydrogen pressure. The results show that the catalytic properties are greatly affected by the supports. Pt/CNTs catalyst exhibits the best catalytic performance among the Pt-based catalysts, producing o-CAN with 99.6% selectivity at complete conversion. Pd/CNTs catalyst exhibits the best catalytic performance among the Pd-based catalysts, giving o-CAN with 95.2% selectivity at complete conversion. For Pt-based catalysts, geometric effect and the textures and properties of the supports play important roles on catalytic properties. On the other hand, geometric effect, electronic effect and the textures and properties of the supports simultaneously influence the catalytic properties of the Pd-based catalysts. In addition, hydrogenolysis of the C–Cl bond can be well inhibited over all catalysts prepared by laser vaporization deposition.     

Hydroisomerization of n-heptane over bimetal-bearing H3PW12O40 catalysts supported on dealuminated USY zeolite

The bimetal-bearing (CePt or LaPt) 12-tungstophosphoric acid (H₃PW₁₂O₄₀ (PW)) catalysts supported on dealuminated USY zeolite (DUSY) were prepared by impregnation and characterized by XRD, BET, IR, and H₂-chemisorption. Their catalytic activities were tested in the hydroisomerization of n-heptane with a continuous atmospheric fixed-bed reactor. After the steam treatment combined with the acid leaching, as well as the supporting with PW and the bimetals, the DUSY support retains the Y zeolite porosity and the PW well keeps its Keggin structure in catalysts. The doping of Ce into the catalysts enhances the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Ce or La, especially Ce, exhibit much higher catalytic activity and selectivity than the catalysts without dopants at lowered reaction temperatures. At the optimal reaction conditions, i.e., the reaction temperature of 250°C and WHSV of 1.4 h^?1, the catalyst with a Pt loading of 0.4%, PW loading of 10% and a molar ratio of Ce to Pt of 15:1 shows a conversion of n-heptane of 70.3% with a high selectivity for isomerization products of 94.1%.     

Synthesis of hexamethylene-1,6-dicarbamate by methoxycarbonylation of 1,6-hexamethylene diamine with dimethyl carbonate over bulk and hybrid heteropoly acid catalyst

Synthesis of HDC by methoxycarbonylation of HDA with DMC was carried out over the bulk and hybrid heteropoly acid (HPA) catalyst. The catalysts were systematically characterized by XRD, FTIR, SEM and NH₃-TPD techniques. The by-products produced in the reaction were identified and a possible reaction pathway was proposed based on the by-products analysis. The performances of bulk and hybrid HPA catalysts were evaluated. The H₄[SiW₁₂O₄₀] catalyst revealed high performance compared with other catalysts and its high performance was attributed to its acidic properties. Effects of reaction parameters and reusability of the H₄[SiW₁₂O₄₀] catalyst were also investigated. Under the optimized reaction conditions, HDA conversion reached 93.2% with 64.8% HDC selectivity and only 3.8% by-product selectivity. Moreover, a possible reaction mechanism was proposed for the synthesis of HDC over H₄[SiW₁₂O₄₀] catalyst.     

Catalytic Performance of Re/Ga2O3/WO3/ZrO2 Catalyst for n-Hexane Isomerization

A series of Re/Ga₂O₃/WO₃/ZrO₂ catalysts were prepared by the impregnation method. The crystalline structure, redox, and acid site distribution of the catalysts were characterized by X-ray powder diffraction, temperature-programmed reduction of H₂, and temperature-programmed desorption of NH₃. Their catalytic performance for n-hexane isomerization was studied. The results showed that the addition of Re greatly affected the redox properties and the acid site distribution of the catalysts. Owing to the presence of Re, n-hexane isomerization was catalyzed by metal and acid sites, and thus the conversion of n-hexane and the selectivity for 2,2-dimethylbutane were significantly increased. Under the conditions of 195 °C, 1.0 MPa, LHSV = 1.0 h⁻¹, and n(H₂)/n(C₆) = 2.0, the conversion of n-hexane over 1.0%Re/1.0%Ga₂O₃/WO₃/ZrO₂ is 84.8%, and the selectivities for 2,2-dimethylbutane, i-hexane, and cracking products (C_5-) are 20%, 97.7%, and 2.1%, respectively. The catalyst is stable during 150 h operation.     

Homogeneous and Heterogeneous Catalyzed Esterification of Acrylic Acid with Ethanol: Reaction Kinetics and Modeling

Kinetics of esterification of acrylic acid with ethanol in the presence of homogeneous (H₂SO₄, HCl, p‐TSA, HI) catalysts as well as heterogeneous catalysts (Dowex 50WX, Amberlyst 15) was studied. The effects and performance of these catalysts on the conversion of acrylic acid were evaluated. In the kinetics of homogeneous catalyzed reaction, both concentration and activity‐based model were employed. Activity coefficients were predicted by the Universal Functional group Contribution (UNIFAC) method to consider nonideal behavior of the liquid phase. The heterogeneous catalyzed reaction mechanisms were developed using Eley–Rideal theory. The model results were compared with the experimental results and were in good agreement. The temperature dependency of the constants, reaction enthalpy, and entropy, and activation energy were determined. The conversion of acrylic acid was obtained as 63.2%, 61.02%, 53.3%, 21.4%, 34.96%, and 14.84% for H₂SO₄, p‐TSA, HCl, HI, Dowex 50WX, and Amberlyst 15, respectively, under process temperature of 70°C, reactant molar ratio of 1:1, and catalyst concentration of 2% (v/v) for homogeneous and 2.17 g for heterogeneous catalyst. These outcomes provide an approach to understand the significant effect of each catalyst on the esterification kinetics of acrylic acid and ethanol.     

High-Performance Supported Ru Catalysts for the Aqueous-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone

γ-Valerolactone (GVL) can be obtained by efficient hydrogenation of levulinic acid using ruthenium-based catalysts in an aqueous medium. This paper reports an in-depth study on the activity and selectivity of Ru catalysts supported on zirconia-alumina, focusing on the effect of Ru concentration (0.5, 1.5 and 3 wt. % of Ru) and the selection of operational reaction variables. The results showed that the activity strongly depends on the number and oxidation state of the supported ruthenium particles. The most active catalyst, Ru3/ZA, presented the highest number of nanometric particles of zerovalent Ru and the highest number of acid sites. This catalyst gave ca. 100 % selectivity towards GVL, at high conversion of levulinic acid (over 99 %) under the best operating conditions evaluated (120 °C, 3 MPa H₂ pressure, 1 h of reaction, and 0.1 g of catalyst). In addition, this catalyst kept high levels of conversion and selectivity after successive reuse cycles.     

HAlMCM-41介孔分子筛催化1,3-苯并二噁茂烷合成的研究

研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应. 考察了反应时间、酚与醛(酮)的配比、HAlMCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响. 结果表明, 当邻苯二酚与醛(酮)物质的量比为1∶1.4, 催化剂用量为3.5 g/mol邻苯二酚, 反应4 h, 分子筛n(SiO₂)/n(Al₂O₃)为15时, 选择性一般在99.4%以上, 转化率也一般在85.6%以上, 因此, HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能.     

乙醛低温绿色合成:焦磷酸锆催化乳酸脱羰反应

以生物基乳酸为原料,焦磷酸锆为催化剂,通过脱羰反应制备乙醛。探讨了模板剂、焙烧温度对催化剂的织构、表面酸碱性以及催化活性的影响规律。以此为基础,进一步揭示了催化剂的表面性质与脱羰反应活性之间的构效关系,发现乳酸脱羰反应由催化剂表面的酸碱位协同催化。和文献报道的相关催化剂比较,该催化剂拥有良好的低温催化活性。此外,在较高液空速、低催化剂用量以及控制低乳酸转化率(40%)下,催化剂连续运行50 h左右后,乳酸转化率及乙醛选择性没有明显变化,表明该催化剂拥有良好的稳定性能。通过反应尾气分析,证实了乙醛的合成主要是通过乳酸脱羰反应途径实现。