载体对甲烷在镍催化剂上分解反应的影响

开发洁净廉价的燃料替代石油已成为各国竞相研究的热点。从环境友好的观点出发 ,Ｈ2 气是一种理想的洁净燃料 ,其燃烧产物只有Ｈ2 Ｏ ,对环境无任何污染 ,Ｈ2 气将成为未来人类主要的能源。因此 ,近年来各国竞相开发大规模廉价的制氢和储氢技术。目前 ,碳及碳氢化合物制合成气法[1 ,2 ] 以其成本低和技术成熟已成为当前大规模制氢最常用的方法 ,包括碳氢化合物的水蒸气重整、ＣＯ2 重整、催化部分氧化法和自热重整[1～ 4] 。近年来又兴起了甲烷催化分解制氢[5,6] 。以上各方法均包含甲烷在镍催化剂上的分解过程[7,8] 。Ｒｏｓｔｒｕｐ Ｎｉ…     

CuO系粉体催化剂的制备方法及其分解H2O2活性研究

ＣｕＯ系粉体催化剂在氧化、加氢、ＣＯ及碳氢化合物燃烧、精细化工合成、氧电极催化等领域具有重要用途 ,因而有关ＣｕＯ系粉体的研究倍受人们的关注[1～ 7] 。我们以前的研究发现 ,ＣｕＯ粉体的催化活性与其状态密切相关 ,大颗粒ＣｕＯ(微米级 )对分解Ｈ2 Ｏ2 无活性 ,但当颗粒尺寸小到纳米级时却表现出较高活性[8] 。本文在此工作基础上着重研究制备方法对ＣｕＯ系粉体催化剂的物相组成、颗粒大小与形貌、表面结构及分解Ｈ2 Ｏ2 活性的影响 ,旨在为该类催化剂的研究开发提供有价值的信息。1　实验部分1 1　主要仪器与试剂Ｄ ｍａｘ ⅢＣ…     

CO和CO2在Cu／ZnO／Al2O3催化剂上加氢反应机理的原位红外研究

ＣｕＺｎＯＡｌ2Ｏ3催化剂用于合成甲醇的反应机理已经进行了大量的研究[1～3]。近年来,利用原位红外技术在研究合成甲醇的催化反应机理方面取得了不少研究成果[4～7]。但大多数实验是采用低铜含量催化剂[4,5]。本文采用高温加压式原位红外池,在513Ｋ和20ＭＰａ的条件下,...     

肉桂酸环己酯的合成研究

肉桂酸环己酯为具有令人愉快的果香香气的无色粘稠液体 ,不溶于水 ,易溶于乙醇 ,常用于食用香精和日化香精的配料中 ,是典型的香料和食品添加剂[1,2 ] 。据报道 ,目前合成肉桂酸环己酯的方法有二 ,一是传统的硫酸催化酯化法 ,二是用路易斯酸ＦｅＣｌ3·6Ｈ2 Ｏ做催化剂来合成肉桂酸环己酯 ,两种方法虽有各自的优点 ,但它们的收率均不高 ,分别为 78.4%、73 .4% [3] 。近年来人们用相转移催化技术合成了许多酯类[4 ,5] ,受其启发 ,我们在催化剂浓硫酸中加入聚乙二醇 40 0作为混合催化剂来合成肉桂酸环己酯 ,获得了满意的结果 ,反应收率达 84.8…     

新型单茂钛催化剂乙烯均聚反应合成支化聚乙烯

单茂钛化合物Ｃｐ′ＴｉＬ3(Ｃｐ′为 η5 环戊二烯基或取代 η5 环戊二烯基 ;Ｌ为卤素、氢、烃基、烃氧基等 )和甲基铝氧烷 (ＭＡＯ)组成的催化剂催化苯乙烯聚合 ,表现出非常高的催化活性和间规立构选择性[1～ 3] .这类催化剂也可用于丙烯、丁烯等α 烯烃聚合 ,合成无规或立构嵌段聚合物[4～ 6] ;但用单茂钛 /ＭＡＯ催化剂进行乙烯均聚合研究[7] 较少 .本文报道用三甲基铝 (ＴＭＡ)含量不同的改性ＭＡＯ(ｍＭＡＯ)作助化催剂激活 1 ,2 ,3,4,5 五甲基茂基三苄氧基钛 [Ｃｐ Ｔｉ(ＯＢｚ) 3]催化乙烯均聚合 ,对聚合产物结构性能进行表征 ;发现…     

六方沸石分子筛催化剂用于异丁烷与丁烯的烷基化

异构烷烃与烯烃的烷基化是炼油装置制备高辛烷值汽油添加剂的重要途径.目前传统工艺仍使用矿物酸如硫酸或氢氟酸作催化剂,由于该工艺存在着产物分离困难、设备腐蚀严重及环境污染问题,从60年代起国内外开始致力于新型固体酸催化剂的研究与开发工作,已报道的有离子交换树脂[1]、分子筛催化剂[2]及SO=4/MxOy型催化剂[3]等,在分子筛催化剂中已报道的有立方沸石[4]β-分子筛[5]、ZSM系列[5]、分子筛[5]、蒙脱石[5]及MCM-22[6]等,这些催化剂的共性是催化活性较高,但失活较快.目前对分子筛催化剂的研究主要集中在改进的立方沸石体系,而六方沸石催化剂催化异丁烷与丁烯烷基化反应尚未见报道.     

茂钛催化剂聚1-丁烯的合成

茂金属催化烯烃聚合以其高活性、定向性等特点受到广泛重视.Ｋａｍｉｎｓｋｙ[1～4]等用二茂基(Ｃｐ、Ｉｎｄ和Ｆｌｕ)过渡金属(Ｔｉ、Ｚｒ和Ｈｆ)化合物/ＭＡＯ催化剂催化1丁烯聚合,可得到间规(ｓＰＢ)、无规(ａＰＢ)或等规(ｉＰＢ)聚1丁烯.Ｌｉｎ[5]和Ｗｕ[6]分别用单茂基的ＣｐＴｉ(ＯＰｒ)3/ＭＡＯ和ＣｐＴｉ(ＯＢｚ)3/ＭＡＯ催化剂进行丙烯聚合,都得到无规聚丙烯(ａＰＰ),并研究了催化体系中Ｔｉ氧化态分布,认为Ｔｉ+4有利于α烯烃聚合.有关用单茂钛化合物/ＭＡＯ催化体系催化1丁烯聚合的研究目前较少文献报道.本文用新型茂钛催化剂—…     

Au/Mn2O3/Al2O3催化剂的制备及其deNOx活性

由于燃煤烟气、汽车尾气的过度排放 ,大气中ＮＯｘ(其中ＮＯ占 90 %以上 )浓度已呈上升趋势。ＮＯ在阳光作用下 ,易形成光化学烟雾 ,危害人体的呼吸系统。ＮＯ还是破坏大气臭氧层和形成酸雨的前驱气体之一 ,破坏生态环境。催化分解和催化还原法是消除ＮＯ(ｄｅＮＯｘ)的主要方法。但由于实际环境中ＮＯ往往与某一种或几种还原性气体 (如ＣＯ、低碳烃 )共存 ,所以催化还原法是人们公认的有应用前景的ｄｅＮＯｘ 方法[1 ] 。近十几年来 ,国内外研究较多的ｄｅＮＯｘ 催化剂是Ｃｕ ＺＳＭ 5 ,其催化活性除受原料气中氧含量的影响外 ,很大程度上…     

负载型纳米金催化葡萄糖氧化研究进展

正近年来,负载型金催化剂已广泛应用于催化各类氧化反应,如CO氧化[1-2]、水煤气转换反应[3-4]、醇醛的选择性氧化[5-7]、过氧化氢合成[8]、挥发性有机物催化燃烧等[9].同时,负载型金属催化剂(Pt、Pd)已应用于催化葡萄糖氧化制备葡萄糖酸盐,但在催化反应过程中易发生催化剂钝     

甲醇多相羰化制甲酸甲酯新催化体系的研究

甲酸甲酯（MF）是用途广泛的低沸点溶剂和基本有机合成的重要中间体，近年来又逐渐发展为动力燃料的添加剂[1]．迄今MF主要由甲醇液相羰化法生产[2]，但该法存在时空收率低，催化剂与产物需进行分离，反应不能连续进行等弊端[3]。文献[4]曾报道过一种可用于多相体系的阴离子强碱交换树脂，但其催化活性太低，尚看不出有太大的实用价值．本文开发了一种负载型强碱液膜催化剂，在固定床连续流动反应器中首次实现了甲醇多相催化羰化制甲酸甲酯，其催化活性及时空产率明显优于均相催化体系[5]．1实验部分催化剂由碱金属醇化物、液膜相溶剂（甲…     

Efficient ozone decomposition over bifunctional Co3Mn-layered double hydroxide with strong electronic interaction

Ground-level ozone is one of the primary pollutants detrimental to human health and ecosystems. Catalytic ozone decomposition still suffers from low efficiency and unsatisfactory stability. In this work, we report a manganese-based layered double hydroxide catalyst (Co₃Mn-LDH), which exhibited a superior ozone decomposition performance with the efficiency of 100% and stability over 7 h under a GHSV of 2,000,000 mL g^?1h^?1 and relative humidity of 15%. Even when the relative humidity increased to 50%, the ozone decomposition also reached 86%, which significantly exceeds as-synthesized MnO₂ and commercial MnO₂ in performance. The catalytic mechanism was studied by H₂-TPR, FT-IR and XPS. The excellent performance of Co₃Mn-LDH can be attributed to its abundant surface hydroxyl groups that ensured the preferentially surface enrichment of ozone, as well as the cyclic dynamic replenishment of electrons between multivalent Co²⁺/Co³⁺, Mn²⁺/Mn³⁺/Mn⁴⁺ and oxygen species that endowed the stable ozone decomposition. This work offers new insights into the design of efficient catalysts for ozone pollution control.     

臭氧在金属氧化物上的分解机理

臭氧分解反应在环境科学中具有重要理论和实际意义。本文对近期相关文献进行了综述，对臭氧在固体催化剂表面上的吸附和分解过程进行了总结，并结合我们的实验对其分解机理进行了探讨。     

Performance of an Ozone Decomposition Catalyst in Hybrid Plasma Reactors for Volatile Organic Compound Removal

In order to enhance the energy efficiency of nonthermal plasma methods for volatile organic compound decomposition in a catalyst-hybrid plasma reactor, we used a Cu–Cr catalyst to dissociate ozone into active atomic oxygen species at low temperatures. We investigated the conditions necessary to obtain the synergetic effect in single-stage and two-stage combinations. The ozone decomposition catalyst was not effective for the reaction under plasma discharge in the single-stage combination. In the two-stage combination, the efficiency increased by increasing the amount of catalyst. Although the propensity of catalysts for active oxygen species formation from ozone decomposition is important for optimizing the reaction efficiency, the surface area is even more important. We conclude that ozone decomposition catalysts are more effective in the two-stage combination compared to the single-stage.     

A kinetic study of ozone decomposition on illuminated oxide surfaces

The heterogeneous chemistry and photochemistry of ozone on oxide components of mineral dust aerosol, including α-Fe(2)O(3), TiO(2), and α-Al(2)O(3), at different relative humidities have been investigated using an environmental aerosol chamber. The rate and extent of ozone decomposition on these oxide surfaces are found to be a function of the nature of the surface as well as the presence of light and relative humidity. Under dark and dry conditions, only α-Fe(2)O(3) exhibits catalytic decomposition toward ozone, whereas the reactivity of TiO(2) and α-Al(2)O(3) is rapidly quenched upon ozone exposure. However, upon irradiation, TiO(2) is active toward O(3) decomposition and α-Al(2)O(3) remains inactive. In the presence of relative humidity, ozone decay on α-Fe(2)O(3) subject to irradiation or under dark conditions is found to decrease. In contrast, ozone decomposition is enhanced for irradiated TiO(2) as relative humidity initially increases but then begins to decrease at higher relative humidity levels. A kinetic model was used to obtain heterogeneous reaction rates for different homogeneous and heterogeneous reaction pathways taking place in the environmental aerosol chamber. The atmospheric implications of these results are discussed.     

Rapid Ozone Decomposition over Water-activated Monolithic MoO3/Graphdiyne Nanowalls under High Humidity

Catalytic ozone (O₃) decomposition at high relative humidity (RH) remains a great challenge due to the catalysts poison and deactivation under high humidity. Here, we firstly elaborate the role of water activation and the corresponding mechanism of the promoted O₃ decomposition over the three-dimensional monolithic molybdenum oxide/graphdiyne (MoO₃/GDY) catalyst. The O₃ decomposition over MoO₃/GDY reaches up to 100 % under high humid condition (75 % RH) at room temperature, which is 4.0 times as high as that of dry conditions, significantly surpasses other carbon-based MoO₃ materials(≤7.1 %). The sp-hybridized carbon in GDY donates electrons to MoO₃ along the C−O−Mo bond, facilitating water activation to form hydroxyl species. As a result, hydroxyl species dissociated from water act as new active sites, promoting the adsorption of O₃ and the generation of new intermediate species (hydroxyl ⋅OH and superoxo ⋅O₂⁻), which significantly lowers the energy barriers of O₃ decomposition (0.57 eV lower than dry conditions).     

臭氧催化氧化脱除低浓度甲醛的新方法

甲醛作为一种典型的室内挥发性有机污染物,对人体健康危害很大.目前,在可用于室内甲醛脱除的诸多方法之中,臭氧催化氧化法因可于室温下使用廉价的金属氧化物催化剂实现对甲醛的高效脱除,从而受到了科研工作者的广泛关注.然而,考虑到室内甲醛的浓度极低,且存在着长期缓慢释放的特点,传统的臭氧催化氧化法应用于实际的室内甲醛脱除不仅会造成能量的浪费,而且还易因未完全分解臭氧的连续释放带来二次污染问题.为了提高臭氧催化氧化脱除甲醛过程的臭氧利用率,降低能耗,并有效缓解未分解臭氧引起的二次污染,本文将一种循环的甲醛存储-臭氧催化氧化新方法应用于室内低浓度甲醛的脱除.该新方法包含甲醛存储与臭氧催化氧化两个过程,在存储阶段低浓度甲醛吸附存储于催化剂表面,而在臭氧催化氧化阶段臭氧将存储的甲醛氧化为CO2与H2O,并重新释放催化剂表面的吸附位.因负载型氧化锰具有优良的臭氧分解能力,本研究以Al2O3负载的MnOx为催化剂,通过研究前驱体及担载量对甲醛脱除反应的影响,筛选出了最优的MnOx/Al2O3催化剂,并对相对湿度的影响规律进行了考察,最后通过低浓度甲醛存储-臭氧催化氧化循环实验验证了该甲醛臭氧催化氧化新过程的可靠性.我们采用传统的等体积浸渍法,基于不同的前驱体制备MnOx/Al2O3催化剂.XRD表征结果表明,乙酸锰为前驱体制得的MA/Al2O3催化剂中MnOx相主要为Mn3O4(粒径约为6.0 nm);而硝酸锰前驱体所得MN/Al2O3催化剂中则含有MnO2与Mn2O3相,且其MnOx颗粒粒径较大,约为9.5 nm.XPS测试结果表明,MA/Al2O3催化剂含有Mn2+,Mn3+及Mn4+,其中Mn3+与Mn4+的含量分别为75%与12%;而MN/Al2O3催化剂则仅含有Mn3+与Mn4+,含量分别为35%与65%.上述XRD与XPS结果相一致,说明以乙酸锰为前驱体所得催化剂的分散度较高且易形成低氧化态的Mn.甲醛存储-臭氧催化氧化实验结果表明,与Al2O3及MN/Al2O3相比,MA/Al2O3催化剂具有更高的甲醛存储与催化氧化脱除性能.基于MA/Al2O3催化剂,不同Mn负载量下的甲醛存储与臭氧催化氧化实验结果表明,Mn负载量为10 wt%时MA/Al2O3的性能最佳.因而,进一步的实验中我们均选用最优的10 wt%MA/Al2O3为催化剂,其在50%相对湿度下的甲醛存储量为26.9μmol/mL,臭氧催化氧化阶段碳平衡为92%,CO2选择性为100%.相对湿度的影响结果(23℃)则表明,由于水分子与甲醛分子间存在着竞争吸附作用,甲醛存储容量随相对湿度的增加而降低;但因相对湿度增加可建立利于甲醛氧化的新途径,故臭氧催化氧化性能随相对湿度增加而增强.综合考虑,10 wt%MA/Al2O3上甲醛存储-臭氧催化氧化的最优相对湿度为50%.为验证所提出新方法的实用性,我们基于10 wt%MA/Al2O3开展了甲醛存储-臭氧催化氧化的4次循环实验.4次循环实验中的甲醛存储以及臭氧催化氧化处理的规律可基本保持一致.50%相对湿度下,低浓度甲醛(15×10-6)在空速为27000 h-1时的穿透时间为110 min,而在臭氧催化氧化阶段(150×10-6臭氧,空速15000 h-1)仅需约50 min即可实现对存储甲醛的氧化脱除(碳平衡大于92%,CO2选择性100%),表明该新方法较传统的臭氧催化氧化方法臭氧用量可节省60%.     

活性炭负载金催化分解空气中低浓度臭氧

采用等体积浸渍法制备了以煤质活性炭为载体的负载金催化剂,并运用N2吸附-脱附法和X射线光电子能谱对样品进行了表征.考察了该催化剂催化分解低浓度臭氧的活性,并研究了载体预处理方法和催化剂后处理方法对催化剂活性的影响.在常温,相对湿度为60%,臭氧浓度为45 mg/m3,空速为60 000 h-1的条件下,1.6 g活性炭经HNO3和NaBH4处理后负载金再经H2还原后的催化剂在反应最初的16 h内臭氧去除率稳定在100%,反应100 h后对臭氧的去除率仍在97%以上.表征结果表明,NaBH4还原处理使得活性炭比表面积、孔体积及石墨碳含量增加,含氧官能团下降,从而提高了催化剂的活性.载金后,催化剂比表面积和孔体积进一步增大,但石墨碳含量下降,C-O和COO-等含氧官能团增加.经臭氧氧化后,催化剂的比表面积和孔体积减小,石墨碳含量下降,C-O,COO-和C=O等含氧官能团增加,而金的粒径和价态并未改变,表明活性炭在金催化下被臭氧氧化.     

堇青石蜂窝陶瓷负载锰氧化物催化分解臭氧性能

为了提高臭氧分解催化剂的实际应用能力,通过采用过渡金属锰氧化物为原料与铝胶混合涂覆到堇青石蜂窝陶瓷载体表面,制备了不同锰氧化物负载的整体式催化剂。 然后在常温常压下考察了整体式催化剂分解臭氧的性能。 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼(Raman)光谱、X射线光电子能谱仪(XPS)、BET比表面积法和程序升温还原技术(H₂-TPR)对催化剂进行了表征。 研究结果表明,不同锰氧化物催化剂的活性按以下顺序排列:氧化锰八面体分子筛(OMS-2)＞MnO₂＞Mn₂O₃＞Mn₃O₄＞MnO。 相比其它锰氧化物,OMS-2负载的整体式催化剂对臭氧的反应活性最高,这可能归因于OMS-2具有较大的比表面积和较好的还原性能,从而有利于表面氧空位的生成和参与臭氧分解反应。 研究结果为提高堇青石蜂窝陶瓷负载型整体式催化剂应用于臭氧分解的性能提供了理论依据。     

Removal of Volatile Organic Compounds (VOCs) at Room Temperature Using Dielectric Barrier Discharge and Plasma-Catalysis

Non-thermal plasma (NTP) was produced in a dielectric barrier discharge reactor for degradation of acetaldehyde and benzene, respectively. The effect of volatile organic compounds (VOCs) chemical structure on the reaction was investigated. In addition, acetaldehyde was removed in different background gas. The results showed that, no matter in nitrogen, air or oxygen, NTP technology always exhibited high acetaldehyde removal efficiency at ambient temperature. However, it also caused some toxicity by-product such as NOx and ozone. Meanwhile, some intermediates such as acetic acid, amine and nitromethane were formed and resulted in low carbon dioxide selectivity. To solve above problems, Co–OMS-2 catalysts were synthesized and combined with plasma. It was found that, the introduction of catalysts improved VOCs removal efficiency and inhibited by-product formation of plasma significantly. The plasma-catalysis system was operated in a recycling experiment to investigate its stability. The acetaldehyde removal efficiency can be kept at 100 % in the whole process. However, slight deactivation in ozone control was observed at the later stage of the experiment, which may be ascribed to deposition of VOCs on the catalysts surface and reduction of catalysts surface area.     

A Study of Sulfonol Decomposition in Water Solutions Under the Action of Dielectric Barrier Discharge in the Presence of Different Heterogeneous Catalysts

The decomposition kinetics of sulfonol (surfactant) in water solutions as well as the formation kinetics of decomposition products under the action of an oxygen dielectric barrier discharge (DBD) at atmospheric pressure in the presence or absence of TiO₂, NiO and Ag₂O catalysts in the plasma zone was studied. The DBD discharge was shown to have high decomposition efficiency (phenol-up to 98%, sulfonol-up to 80%). In a plasma-catalytic hybrid process, the efficiency of organic substances decomposition was higher than efficiency for the DBD treatment without catalyst. The catalysts application resulted in a change in the ratio and yield of decomposition products.