三维有序大孔钙钛矿催化剂在挥发性有机物催化燃烧中的研究进展

催化燃烧是处理挥发性有机物(VOCs)的有效处理技术之一。催化燃烧的核心是制备高效稳定的催化剂,随着多孔材料制备技术的发展,具有三维有序大孔(3DOM)的钙钛矿催化剂表现出较好的催化燃烧稳定性和活性,受到人们普遍关注。本文结合近几年国内外3DOM钙钛矿催化剂的主要研究成果,在3DOM钙钛矿催化剂的结构、性能及制备方法等方面的研究成果概述的基础上,分析了其热稳定性、机械稳定性、疏水性、氧化还原性及酸碱性等功能化方面的最新进展,指出了目前3DOM钙钛矿催化剂亟待解决的问题,最后对今后的研究趋势进行了展望:胶体晶体模板的合成方法的改进、多功能性3DOM钙钛矿催化剂的制备及其对催化活性的影响机理的研究是今后发展的方向。     

难降解工业有机废水臭氧催化氧化催化剂研究进展

催化臭氧氧化技术是一种重要的有机废水处理方法,具有氧化能力强,操作简便,无二次污染等特点。综述了不同催化剂在催化臭氧氧化降解有机废水过程中性能,并对其机理进行分析,讨论了不同工艺条件对反应结果的影响,并在现有基础上对催化臭氧氧化催化剂的研究方向进行推测,指出具有高热稳定性和化学稳定性的钙钛矿催化剂应是未来重要的研究方向之一。     

改性镧系钙钛矿催化剂强化挥发性有机物催化氧化的研究进展

钙钛矿因其结构稳定并具有优异的物化性质,近年来在催化剂方面的应用受到了广泛关注。本文综述了采用不同方法对镧系钙钛矿进行改性来增强催化剂的活性、抗毒性、稳定性和选择性的研究进展;分析了镧系钙钛矿的结构、表面参数、活性氧和低温还原性对于挥发性有机物转化效率的影响,重点阐述了通过优选钙钛矿的制备方法、制备负载型钙钛矿和掺杂型钙钛矿等改性方法来提高镧系钙钛矿催化剂的性能,由此展望了未来改性镧系钙钛矿催化剂的研究方向：采用非金属元素掺杂或多种强化方法结合制备高效催化剂、利用催化燃烧协同光催化氧化转化挥发性有机物、进一步通过实验和仿真模拟制备理想钙钛矿催化剂催化氧化多种挥发性有机物混合物以满足工业化需求。     

生物质油催化加氢脱氧（HDO）反应机理及催化剂研究进展

对近年来生物质油催化加氢脱氧催化剂的制备、催化性能和反应机理的研究进展进行了整理总结。重点对贵金属催化剂、过渡金属催化剂和硫、氮、碳、磷等金属化合物催化剂的制备方法、催化性能和作用机理进行了概述,并分析了加氢脱氧催化剂的失活原因,同时提出生物质油加氢脱氧反应催化剂的未来发展方向：三维有序大孔（3DOM）钙钛矿氧化物的应用可能在提高催化剂的催化性能有作用。     

钙钛矿La1-xKxCoO3纳米晶的制备与结构及其对炭烟的催化燃烧性能

采用溶胶-凝胶法制备了K 掺杂的La1-xKxCoO3系列钙钛矿结构柴油车尾气炭烟氧化催化剂,用XRD, TG-DTA及程序升温反应等技术详细研究了K 掺杂量及焙烧温度对催化剂结构和炭烟燃烧性能的影响,初步探讨了催化剂结构与性能之间的相关性. 实验结果表明,以蔗糖为络合剂在600℃下可以得到纯钙钛矿结构的La1-xKxCoO3纳米晶,其中菱方相为LaCoO3系钙钛矿的高温稳定相,升高焙烧温度及增加K 掺杂量都会促进钙钛矿结构由立方相转变为菱方相. K 的掺杂可以降低炭烟的燃烧温度,一定量的K可以提高炭烟的燃烧速率. 700℃焙烧的具有菱方相钙钛矿结构的La0.9K0.1CoO3具有最好的催化性能,对炭烟的起燃点和燃尽温度分别为240及387℃,可以通过柴油车自身的排气热量来实现炭烟的催化燃烧过程.     

甲烷催化燃烧催化剂催化理论与应用研究进展

概述了甲烷催化燃烧催化剂的研究现状,从组成甲烷燃烧催化剂的3个部分（基体、活性组分、氧化物载体）分别加以论述。通过掺杂一些金属和金属氧化物,不但可以提高高活性贵金属催化剂的热分解温度,还可以提高高温催化剂（如钙钛矿和六铝酸盐材料等）的催化活性。最后简要综述了甲烷催化燃烧反应机理。     

天然气催化燃烧催化剂的研究(Ⅱ)

介绍了天然气催化燃烧钙钛矿型氧化物催化剂、六铝酸盐型催化剂以及负载型非贵金属催化剂的研究现状。对于钙钛矿型氧化物催化剂,利用A位取代或调整B位元素的种类及配比、新的技术和方法制备高比表面积或具有纳米结构的钙钛矿型氧化物,是提高其甲烷催化燃烧活性的重要手段。六铝酸盐型催化剂具有很高的热稳定性和甲烷燃烧活性,但起燃温度较高,通过采用将金属Pd负载到六铝酸盐上或改变制备方法,提高其比表面积,以提高其低温反应活性。负载型非贵金属催化剂研究最多的是过渡族金属,其氧化活性、抗毒性能和耐久性都存在问题,需进一步研究。     

钙钛矿La1-xKxCoO3纳米晶的制备与结构及其对炭烟的催化燃烧性能

采用溶胶-凝胶法制备了K+掺杂的La1-xKxCoO3系列钙钛矿结构柴油车尾气炭烟氧化催化剂,用XRD, TG-DTA及程序升温反应等技术详细研究了K+掺杂量及焙烧温度对催化剂结构和炭烟燃烧性能的影响,初步探讨了催化剂结构与性能之间的相关性. 实验结果表明,以蔗糖为络合剂在600℃下可以得到纯钙钛矿结构的La1-xKxCoO3纳米晶,其中菱方相为LaCoO3系钙钛矿的高温稳定相,升高焙烧温度及增加K+掺杂量都会促进钙钛矿结构由立方相转变为菱方相. K+的掺杂可以降低炭烟的燃烧温度,一定量的K可以提高炭烟的燃烧速率. 700℃焙烧的具有菱方相钙钛矿结构的La0.9K0.1CoO3具有最好的催化性能,对炭烟的起燃点和燃尽温度分别为240及387℃,可以通过柴油车自身的排气热量来实现炭烟的催化燃烧过程.     

甲烷催化燃烧非贵金属氧化物催化剂的研究进展

催化燃烧具有起燃温度低、能量利用率高、有毒物质排放少等优点。催化剂是催化燃烧的关键,非贵金属氧化物催化剂因来源广、价格低、稳定性较好成为研究热点。综述了单组分、双组分或多组分、钙钛矿型、六铝酸盐型、尖晶石型等几类非贵金属氧化物催化剂的研究进展。     

催化燃烧法脱除含氯挥发性有机化合物研究进展

含氯挥发性有机物(CVOCs)由于其毒性、高稳定性和在环境中的持久性而备受关注,有效脱除CVOCs是环境治理领域面临的重要课题,也成为近年来研究的热点。催化燃烧或氧化法因其能耗和成本低有望成为最有效脱除CVOCs的方法之一。对催化燃烧脱除CVOCs的研究进行了综述,重点总结和评述了催化燃烧脱除CVOCs的催化剂,包括金属氧化物、过渡金属氧化物和钙钛矿复合氧化物等催化剂,简要阐述了催化剂的失活类型和再生方法,并对未来催化燃烧法脱除CVOCs的研究进行了展望。     

Development of Mn-based perovskite materials: Chemical structure and applications

In this article, we summarize current progress on the bulk and surface characteristics of Mn-containing perovskite oxides known for their good catalytic activity in atmospheric pollutant abatement. These materials are emphasized as serious alternatives for noble metal-based catalysts (Pt, Rh, Pd) in many catalytic applications particularly in automotive exhaust catalytic converters, mainly due to their low cost, good thermal stability at high temperature and ease of preparation compared to supported noble metal catalysts. The success of such materials is mainly related to Mn³⁺ and Mn⁴⁺ mixed valence and the resulted point defects formed after incorporation of a large variety of metals with different size and charge in the perovskite structure. These parameters could also affect the Mn reducibility and oxygen species mobility considered as one of the most determining factors in catalytic activity. The effect of perovskite metallic composition on the surface Mn oxidation state and relative cations segregation as well as applications of Mn-containing perovskite oxides as catalysts for several deep oxidation reactions at low and high temperatures are presented. Particular attention is devoted to the solution combustion synthesis for Mn-containing perovskite catalysts due to its time and energy saving characteristics and high surface areas of the obtained products. These advantages open new attractive opportunities for the use of this economic process to prepare supported perovskite oxide catalysts with the aim to better control morphology and stability of both surface catalyst and supports.     

Preparation and characterisation of supported La0.8Sr0.2MnO3+x

Three supported La_0.8Sr_0.2MnO_3+x catalysts were prepared, one supported on lanthanum-stabilised alumina and two supported on a NiAl₂O₄ spinel. The catalysts were characterised using X-ray diffraction, transmission electron microscopy and surface area measurements following heat-treatments at temperatures up to 1200°C in air. In the alumina-supported catalyst, a reaction occurred between the active phase and the support at high temperatures, indicating that these materials would be unsuitable for high temperature catalytic combustion. Only in the NiAl₂O₄-supported catalysts were the supported perovskite phases found to be stable at high temperature. These catalysts showed good methane combustion activity.     

Low Cost, Ceria Promoted Perovskite Type Catalysts for Diesel Soot Oxidation

Perovskite type catalysts with SrCoO₃ and Sr_0.8Ce_0.2CoO₃ compositions have been prepared by co-precipitation and other methods and, their catalytic activity towards diesel particulate matter (PM)/carbon oxidation has been evaluated under the loose contact condition. These catalysts show excellent catalytic activity for PM/carbon oxidation, despite their low surface area and under the loose contact condition. The synergistic effects of Ce incorporation in perovskite and presence of a small amount of potassium appears to be responsible for the high soot oxidation activity of these perovskite type materials. The Ce incorporation seems to be contributing by enhancing the redox property of the catalyst, while it appears unlikely that potassium is contributing by improving the catalyst–soot contact through its volatization. The catalysts show excellent thermal stability and stable activity under repeated cycles of use.     

金属基体整体式催化剂的制备及在VOCs催化燃烧中的应用研究进展

催化燃烧是对挥发性有机物(VOCs)高效率、低污染的处理技术.以金属为基体制备的整体式催化剂因压降低、催化效率高,机械强度和热稳定好等优点是催化燃烧VOCs的研究热点.本文从金属基体结构选择、表面预处理、涂层制备和催化燃烧VOCs几个方面,对近年来金属基体整体式催化剂的研究进行了述评.由此指出,制备高性能的过渡涂层以及...     

Solvent nature effect in preparation of perovskites by flame pyrolysis: 2. Alcohols and alcohols + propionic acid mixtures

The effect of either pure alcohols or alcohols + propionic acid mixtures as solvents for the preparation by flame pyrolysis of a standard LaCoO₃ catalyst, to be employed for the catalytic flameless combustion of methane, has been investigated. All the catalysts proved very active for the mentioned reaction. Low-MW pure alcohols showed however less suitable than alcohols-propionic acid mixtures, leading to lower perovskite phase purity, less particle size homogeneity and lower specific surface area. The high volatility of the solvent seems to be the major cause, together with the improper behaviour of nitrates (forced by solubility reasons) as perovskite metals precursors. However, the addition of propionic acid to the alcohols allowed to use the acetates as precursors and hence to obtain high perovskitic phase purity, high SSA and uniform particle size. Moreover, the increase of combustion enthalpy of the solvent, through the addition of higher-MW alcohols, leading to progressively higher flame temperature, strongly improved the thermal resistance of the catalyst, without lowering catalytic performance.     

Ethanol combustion over strontium- and cerium-doped LaCoO3 catalysts

Ce- or Sr-doped LaCoO₃ bulk perovskites were prepared by citric acid method as well as 10 wt.% of LaCoO₃ was deposited on alumina carrier stabilized with lanthanum. Properties of prepared materials were characterized by determination of surface area, acid-basic properties and XRD, XPS, TPDO₂, H₂-TPR measurements as well as catalytic activity and selectivity for ethanol combustion was tested. It was found that substitution of La in LaCoO₃ with either Sr or Ce has only small effect on its activity in ethanol combustion. Strontium inserted into LaCoO₃ structure increases basic character of the perovskite surface as well as selectivity to acetaldehyde (ACA). Substitution of La with cerium has no effect on the concentration of basic sites and does not affect the selectivity to ACA. Activity of LaCoO₃-based catalysts in ethanol combustion and their selectivity to ACA formation can be explained on the basis of the presence of both -oxygen species and sites with basic character on the material surface.

Acid-basic properties of supported LaCoO₃ are dominated by acidic character of the carrier. Results of XPS and H₂-TPR measurements of LaCoO₃ supported on La–Al₂O₃ suggest that perovskite remains in strong interaction with carrier and probably is partially decomposed. Deposition of perovskite on stabilized carrier significantly increases the rate of ethanol combustion.     

钙钛矿复合氧化物的介孔化及用于CH4催化燃烧

利用有序介孔立方相(Ia3d)乙烯基三乙氧基硅烷(TEVS)为模扳,通过纳米组装法在硅基硬模板的介孔中填入La - Fe -柠檬酸络合物,经焙烧和碱洗去除硅基模板,制备具有有序介孔结构且高比表面积的LaFeO3钙钛矿(ABO3),并与软模板法和自燃烧法制备的LaFeO3钙钛矿催化荆作对比,运用XRD、TEM和BET对合...     

A review on recent advances in catalytic combustion of chlorinated volatile organic compounds

Chlorinated volatile organic compounds (CVOCs) with strong stability, poor reactivity and high toxicity in waste gases are emitted into the atmosphere from many industrial operations, which has caused sustained harm to both human health and atmospheric environment. Catalytic combustion is regarded as one of the most effective methods to eliminate CVOCs due to its high removal efficiency, low energy consumption and low production of secondary pollutants. However, the screening of efficient catalysts (i.e. low cost, high activity and durability) still remains challenging. In this review, recent developments on catalytic combustion of CVOCs, including catalysts, reaction condition, catalytic reaction mechanism, deactivation reasons and regeneration methods are summarized. It is emphasized that the active components, structures and supports of catalysts have significant effects on their activity, selectivity, stability and longevity. In addition, it is pointed out that catalyst deactivation is closely related to chlorine poisoning, sintering, carbon deposition and metal active phase leaching. Compared with other catalysts, perovskite-type composite oxides and spinel-type composite oxides have shown to be promising materials in the catalytic combustion of CVOCs due to their particular structure and nature (e.g. surface area, redox property and surface acidity). Thereafter, the outlooks on catalytic combustion of CVOCs are also presented in this article based on the studies in the literature, which offer influential information for further research on the treatment technology of CVOCs. © 2020 Society of Chemical Industry