甲醇气相脱水制二甲醚催化剂研究进展

甲醇气相脱水制二甲醚反应为固体酸催化反应,常用的固体酸催化剂有γ-Al₂O₃和分子筛类。γ-Al₂O₃表面存在弱酸中心或中等强度酸中心,催化剂有较好的初始催化活性,但活化所需的反应温度较高,耐水稳定性差;分子筛类催化剂表面有许多强酸性位,低温下催化活性较高,但在高温反应条件下易产生烃类副产物和积炭,热稳定性差。为改善这两类催化剂的催化性能,对催化剂进行了各种改性研究,改性后催化剂的活性、选择性和稳定性均有一定程度提高。综述了近年来在γ-Al₂O₃和分子筛催化剂上进行的改性研究,总结并展望了甲醇脱水催化剂的发展方向。     

SBA-15固载酸性离子液体催化酯化反应性能

为了减少离子液体用量及解决催化剂分离问题,采用键合法制备了以SBA-15为载体的固载化离子液体催化剂[C₃SO₃HCP]HSO₄/SBA-15,通过FT-IR、TG、XRD、BET和TEM分析了催化剂的结构和稳定性。并将其应用于催化丁二酸酐和乙醇的酯化反应。结果表明:[C₃SO₃HCP]HSO₄被成功固定在SBA-15上,且具有较高的热稳定性和催化活性,克服了非均相催化剂活性不高与均相催化剂难以分离的不足。在催化剂用量为反应物总质量的5%、n(C₄H₄O₃):n(C₂H₅OH)=1:3,反应温度80℃;反应时间4 h、带水剂用量为反应物总质量的30%的条件下,酯收率达93.7%,且该催化剂循环使用8次后,仍具有较高的催化活性。此外,还考察了以[C₃SO₃HCP]HSO₄/SBA-15为催化剂催化合成系列酯也获得了较高的酯收率,且易于与产物酯分离。     

Pt/Pt-Ce/γ-Al2O3催化氧化甲苯研究

通过等体积浸渍法制备单贵金属Pt/γ-Al₂O₃和双金属Pt-Ce/γ-Al₂O₃催化剂,考察Ce对催化剂活性的影响,确定催化剂最优配比。结果表明,当Pt的负载量为质量分数0.5%时,Pt/γ-Al₂O₃催化活性最高;当Pt的负载量为质量分数0.2%,Ce的负载量为质量分数1.0%时,Pt-Ce/γ-Al₂O₃催化剂的催化活性最高。Pt-Ce/γ-Al₂O₃催化剂的甲苯转化率高于Pt/γ-Al₂O₃催化剂。随着Pt负载量增大,催化剂孔容、孔径减小。粉体式催化剂性能优于整体式催化剂,但差别不大;Ce的添加有助于催化剂活性的提升。     

载体对Pt催化甲基环己烷脱氢性能的影响

采用浸渍法制备了Al₂O₃、SiO₂、Y₂O₃及活性炭负载的0.2%(质量分数,下同)Pt催化剂。氮气吸附脱附、H₂-TPR、CO脉冲吸附对催化剂表征的结果表明,活性炭载体上活性组分的分散度最高,催化甲基环己烷(MCH)脱氢反应的结果表明,活性炭负载的Pt催化剂具有最高的催化活性。     

微乳液法制备Pt/Al2O3催化剂及其催化氯代硝基苯选择加氢活性

采用十六烷基三甲基溴化铵（CTAB）/正丁醇/环己烷/H₂PtCl₆溶液的微乳体系,以N₂H₄·H₂O为还原剂,Al₂O₃为载体制备Pt/Al₂O₃催化剂。以邻氯硝基苯（o-CNB）选择加氢反应为探针,考察微乳液组成对Pt/Al₂O₃催化剂选择加氢活性的影响。运用XRD、XPS、IR、TEM和EDS对载体和催化剂进行表征。结果表明,微乳体系中CTAB∶正丁醇∶环己烷质量比9∶21∶70,3.6% H₂PtCl₆溶液中制备的Pt/Al₂O₃催化剂的o-CNB选择加氢活性最高。Pt粒子粒径5 nm左右,与载体之间没有明显的电子效应。对于取代位置不同的间、对氯硝基苯（m-CNB、p-CNB）加氢,Pt/Al₂O₃催化剂也表现出较高的催化活性。     

制备条件对Pt/SO42-/ZrO2-Al2O3异构化性能的影响

采用沉淀法制备了Pt/SO₄^2-/ZrO₂-Al₂O₃ (PtSZA)催化剂,考察了氢氧化锆水凝胶干燥速率、锆盐浓度、铂含量、Al₂O₃和SO₄^2-添加顺序等制备条件对PtSZA异构化性能,尤其是低温异构化性能的影响,并用XRD和TG对催化剂进行了表征。结果表明,提高水凝胶的干燥速率降低了PtSZA催化剂中的硫含量,大大提高了催化剂中的单斜相,进而导致了催化剂低温失活加速以及高温活性下降。较低或较高的锆盐浓度劣化了PtSZA的低温异构化稳定性,以0.4~0.6mol/L硝酸氧锆制备的催化剂硫含量和四方相氧化锆含量较高,异构化活性相对较好,Al₂O₃和SO₄^2-添加顺序对PtSZA异构化性能没有明显影响。     

La2O3/AC催化剂在CO同时还原SO2和NO反应中的性能

以改性活性炭为载体,采用等体积浸渍法制备了La₂O₃/AC催化剂。采用XRD和BET手段对催化剂进行表征,使用微型固定床反应器考察催化剂的脱硫脱硝活性。结果表明,La₂O₃/AC催化剂对CO同时还原SO₂和NO具有良好活性,负载质量分数10%的La₂O₃/AC催化剂活性较好,SO₂和NO转化率达到90%的反应温度最低,分别为335 ℃和325 ℃;载体与活性组分之间存在协同作用,引入活性炭载体能够降低反应温度并提高催化活性。     

负载型Pt-Fe/Al2O3催化剂用于室温催化氧化甲醛

采用胶体沉积法制备不同载体（Ni₂O₃、Co₃O₄、TiO₂、Al₂O₃）的Pt-Fe/MeO_x催化剂用于甲醛室温催化氧化。活性测试表明,以γ-Al₂O₃为载体的Pt-Fe/Al₂O₃催化剂具有较高的催化活性,在25℃时甲醛的转化率可达到100%,而且Pt-Fe/ Al₂O₃催化剂还表现出良好的稳定性。采用各种表征技术对Pt-Fe/Al₂O₃的形貌、价态及氧化还原性等物理化学性质进行了研究,结果表明：Pt-Fe/Al₂O₃催化剂中Pt物种和Fe物种在Al₂O₃载体的表面上均匀分散;二者之间存在着较强的相互作用,在Al₂O₃载体的表面上形成一些类似Pt-O-Fe活性物种,有效促进了Pt-Fe/Al₂O₃催化性能,从而显示出较高的氧化活性。     

Co3O4-MMT催化剂的制备及其N2O催化分解性能

以MMT为载体，采用原位聚合-配位沉积法制备3种不同Co负载量的Co₃O₄-MMT催化剂。采用N₂物理吸附、XRD和TEM对载体和催化剂进行表征，并在连续流动微反装置上考察其N₂O催化分解性能。结果表明，与Co₃O₄催化剂相比，Co₃O₄-MMT催化剂的比表面积显著增大，且活性组分Co₃O₄具有较高的分散状态。Co₃O₄-MMT催化剂的催化活性随着Co含量的增加先升后降，其中0.015Co-MMT表现出最佳的催化活性，其活性远高于Co₃O₄催化剂，同时，该催化剂还表现出良好的催化稳定性和较好的杂质气体耐受性。     

煅烧温度对磁性铁钛复合氧化物微观结构及脱硝活性的影响

利用共沉淀微波法构筑新型磁性铁钛复合氧化物催化剂,研究了煅烧温度对其物性结构及NH₃-SCR脱硝性能的影响,揭示了钛掺杂对磁性γ-Fe₂O₃晶体高温热转化及其脱硝性能的优化机制。结果表明：当煅烧温度由300℃升至500℃时,磁性铁氧化物的比表面积、孔容先增大后减小,且较高的煅烧温度促使其γ-Fe₂O₃晶体逐步转变为α-Fe₂O₃晶体,导致磁性铁氧化物表面Fe²⁺和活性氧浓度增大,促使其NH₃-SCR脱硝性能降低;掺杂钛可提高磁性铁氧化物的热稳定性,抑制了高温煅烧下γ-Fe₂O₃晶体向α-Fe₂O₃晶体的不可逆转变和其孔隙结构的坍塌,增大了高温煅烧时磁性铁氧化物催化剂的比表面积和比孔容,合适的煅烧温度为400℃;该煅烧温度下,催化剂低温活性最佳,反应温度高于220℃、空速比60000h^-1时可获得80%以上的NO_x转化效率。     

Comparison of behaviour of rare earth containing catalysts in the oxidative dehydrogenation of ethane

Catalyst promotion by addition of either La and Sm to MgO or Na aluminate to Sm₂O₃ and La₂O₃ has been investigated for the oxidative dehydrogenation of ethane in the temperature range 550–700°C. With all unpromoted and promoted catalysts, the selectivity to ethylene is strongly enhanced by the temperature, the highest values being obtained at 700°C. Sm₂O₃ is the most active among the bulk oxides, while samarium addition to MgO results in higher surface area, but does not enhance the catalytic activity. Ethylene productivity on La₂O₃ promoted MgO samples is higher than with pure La₂O₃, Sm₂O₃ and MgO, not only due to the stabilising effect of La on MgO surface area, but also due to a higher intrinsic activity. With both bulk oxides and rare earth promoted MgO, the selectivity to ethylene strongly increases by decreasing the O₂/C₂H₆ feed ratio, while it is quite unaffected by ethane conversion and catalyst composition, in agreement with the hypothesis that the main role of catalyst in the experimental conditions investigated is to produce ethyl radicals which are converted in the gas phase to CO and C₂H₄. When La₂O₃ is modified by the addition of sodium aluminate the catalytic behaviour significantly changes, likely due to a different, mostly heterogeneous reaction mechanism. On aluminate promoted lanthana, ethane is converted to ethylene with higher yields which do not depend on the feed ratio. Moreover, only CO₂ is produced as by-product, the formation of CO being quite negligible.     

Preparation of nanosized Mn3O4/SBA-15 catalyst for complete oxidation of low concentration EtOH in aqueous solution with H2O2

A new heterogeneous Fenton-like system consisting of nano-composite Mn₃O₄/SBA-15 catalyst has been developed for the complete oxidation of low concentration ethanol (100 ppm) by H₂O₂ in aqueous solution. A novel preparation method has been developed to synthesize nanoparticles of Mn₃O₄ by thermolysis of manganese (II) acetylacetonate on SBA-15. Mn₃O₄/SBA-15 was characterized by various techniques like TEM, XRD, Raman spectroscopy and N₂ adsorption isotherms. TEM images demonstrate that Mn₃O₄ nanocrystals located mainly inside the SBA-15 pores. The reaction rate for ethanol oxidation can be strongly affected by several factors, including reaction temperature, pH value, catalyst/solution ratio and concentration of ethanol. A plausible reaction mechanism has been proposed in order to explain the kinetic data. The rate for the reaction is supposed to associate with the concentration of intermediates (radicals: OH, O₂⁻ and HO₂) that are derived from the decomposition of H₂O₂ during reaction. The complete oxidation of ethanol can be remarkably improved only under the circumstances: (i) the intermediates are stabilized, such as stronger acidic conditions and high temperature or (ii) scavenging those radicals is reduced, such as less amount of catalyst and high concentration of reactant. Nevertheless, the reactivity of the presented catalytic system is still lower comparing to the conventional homogenous Fenton process, Fe²⁺/H₂O₂. A possible reason is that the concentration of intermediates in the latter is relatively high.     

Influence of the reaction conditions on the electrochemical promotion by potassium for the selective catalytic reduction of N2O by C3H6 on platinum

In this work, we have investigated for the first time the selective catalytic reduction of N₂O by C₃H₆ over an electrochemical catalyst (Pt/K-βAl₂O₃). It was evaluated the influence of the reaction conditions (temperature, oxygen concentration, water vapour presence and time on stream treatment under reaction conditions) on the catalytic performance of the electrochemical catalyst. Electrochemical pumping of potassium ions to the Pt catalyst working electrode strongly increased the N₂O reduction rate, activating the catalyst at lower temperatures. However, it was found that the efficiency of the electrochemical promotion decreased as the oxygen concentration increased because of a strong inhibition of propene adsorption and a relative increase of the oxygen coverage. On the contrary, the presence of potassium ions on the Pt catalyst strongly decreased the inhibiting effect of water vapour, increasing the catalytic activity of the catalyst. In addition, the catalyst stability was confirmed by a deactivation study. It was found that a long term treatment at high temperature under operating conditions had a positive effect on the efficiency of the Pt/K-βAl₂O₃ electrochemical catalyst.     

SBA-15分子筛负载磷钨酸催化合成己二酸

采用SBA-15分子筛等体积浸渍负载磷钨杂多酸制备了PW/SBA-15催化剂,应用XRD、DSG-TGA等对催化剂结构进行分析和表征。结果表明,SBA-15分子筛在负载磷钨酸后,磷钨杂多酸完全引入到SBA-15分子筛的骨架结构中,其稳定性大幅增加。同时采用"一锅煮"的方法用过氧化氢氧化环己烯制得己二酸,运用正交试验法和单因素实验法对催化剂性能进行评价。结果表明,催化剂用量1.75 g、反应时间9 h、反应温度80℃、n(H_2O_2)∶n(环己烯)=5.47∶1,反应开始加入13.75 mL的H_2O_2,4 h后再加入13.75 mL的H_2O_2条件下合成的己二酸收率和纯度最高。     

The catalytic activity and surface characterization of Ln2B2O7 (Ln=Sm, Eu, Gd and Tb; B=Ti or Zr) with pyrochlore structure as novel CH4 combustion catalyst

Ln₂B₂O₇ (Ln=Sm, Eu, Gd and Tb; B=Zr or Ti) with pyrochlore structure was prepared by sol–gel method for the high-temperature catalytic combustion. The crystal structure of Ln₂B₂O₇ was identified by XRD and their surface area was about 4 m²/g after calcinations at 1200 °C. Catalytic activity of methane combustion was observed for Ln₂Zr₂O₇ series and the best catalyst was Sm₂Zr₂O₇. Its relative reaction rate per unit surface area at 600 °C was 2 cm³/m² min, which was twice higher than that of Mn-substituted Sr hexaaluminate. From surface analysis by XPS, the low binding energy of each Ln element of Ln₂Zr₂O₇ compared to that of Ln₂Ti₂O₇, gave the catalytic activity of methane combustion.     

介孔Fe2O3/SBA-15催化臭氧氧化含酚废水

含酚废水来源广泛自然条件下难以去除,酚类物质毒性大对生态环境和人类生活健康造成了较严重的影响。本文选取了有机废水处理中较为高效的臭氧催化氧化技术,使用臭氧氧源曝气产生大量的含氧自由基,催化氧化降解酚类有机物,同时对活性中心载体进行了优化,选取制备了一类水热稳定性好及机械强度高的多孔材料,使用这些多孔材料对活性中心Fe₂O₃进行了再组装,合成了一系列表面富集Fe₂O₃的SBA-15介孔薄膜材料,由于SBA-15材料较大的比表面积、丰富的孔隙结构、高度分散的活性中心,在臭氧催化氧化含酚废水中取得了较好效果。苯酚溶液初始浓度为100mg/L (COD 238mg/L)、Fe₂O₃(5)/SBA-15催化剂投加量为30g、臭氧气体流量为2mg/min、废水HRT为5min、流量为0.8L/h的条件下,该催化剂能高效连续稳定运行500h不易失活,其COD去除率仍能保持在65%以上,催化剂活性依然保持在83%以上。Fe₂O₃/SBA-15类介孔催化材料在深度处理含酚废水中具有工业化应用潜质。     

The size effect and high activity of nanosized platinum supported catalysts for low temperature oxidation of volatile organic compounds

Pt/Al₂O₃ catalysts with smaller size of Pt nanoparticles were prepared by ethylene glycol reduction method in two different way and their oxidation activities for three typical VOCs (volatile organic compounds) were evaluated. The catalyst prepared by first adsorption and then reduction procedure is denoted as L-Pt/Al₂O₃ while the catalyst prepared by first reduction and then loading procedure is defined as R-Pt/Al₂O₃. The results show that L-Pt/Al₂O₃ with the stronger interaction between Pt species and Al₂O₃ exhibit smaller size of Pt nanoparticles and favorable thermal stability compared with R-Pt/Al₂O₃. L-Pt/Al₂O₃ is favor of the formation of more adsorbed oxygen species and more Pt²⁺ species, resulting in high catalytic activity for benzene and ethyl acetate oxidation. However, R-Pt/Al₂O₃ catalysts with higher proportion of Pt⁰/Pt²⁺ and bigger size of Pt particles exhibits higher catalytic activity for n-hexane oxidation. Pt particles in R-Pt/Al₂O₃ were aggregated much more serious than that in L-Pt/Al₂O₃ at the same calcination temperature. The Pt particles supported on Al₂O₃ with~10 nm show the best catalytic activity for n-hexane oxidation.     

The selective oxidation of methane to ethane and ethylene over doped and un-doped rare earth oxides

A comparison has been made of the behaviour in the oxidative coupling of methane of the oxides of Sm, Dy, Gd, La and Tb with that of a Li/MgO material. All but the Tb₄O₇ (which gave total oxidation) were found to give higher yields than the Li/MgO material at temperatures up to approaching 750°C but the Li/MgO system gave better results at higher temperatures. The cubic structure of Sm₂O₃ was found to be responsible for its good performance while the monoclinic structure was relatively inactive and unselective. The addition of Na or Ca to cubic Sm₂O₃ gives a higher optimum C₂ yield than that of unpromoted Sm₂O₃. Sm₂O₃ and Ca/Sm₂O₃ catalysts are more stable than Li/MgO, Li/Sm₂O₃ or Na/Sm₂O₃. The addition of Li or Na to Sm₂O₃ causes the structure to change from cubic to monoclinic; the deactivation of the Na/Sm₂O₃ catalysts is caused by a loss of Na coupled with the formation of the monoclinic form of Sm₂O₃.