Bimetallic CoNi single atoms supported on three-dimensionally ordered mesoporous chromia:highly active catalysts for n-hexane combustion

Developing the alternative supported noble metal catalysts with low cost,high catalytic efficiency,and good resistance toward carbon dioxide and water vapor is critically demanded for the oxidative removal of volatile organic compounds(VOCs).In this work,we prepared the mesoporous chromia-supported bimetallic Co and Ni single-atom(Co_(1)Ni_(1)/meso-Cr_(2)O_(3))and bimetallic Co and Ni nanoparticle(Co_(NP)Ni_(NP)/mesoCr_(2)O_(3))catalysts adopting the one-pot polyvinyl pyrrolidone(PVP)-and polyvinyl alcohol(PVA)-protecting approaches,respectively.The results indicate that the Co_(1)Ni_(1)/meso-Cr_(2)O_(3)catalyst exhibited the best catalytic activity for n-hexane(C_(6)H_(14))combustion(T_(50%)and T_(90%)were 239 and 263℃ at a space velocity of 40,000 mL g^(-1)h^(-1);apparent activation energy and specific reaction rate at 260℃ were 54.7 kJ mol^(-1)and 4.3×10^(-7)mol g^(-1)_(cat)s^(-1),respectively),which was associated with its higher(Cr^(5+)+Cr^(6+))amount,large n-hexane adsorption capacity,and good lattice oxygen mobility that could enhance the deep oxidation of n-hexane,in which Ni_(1) was beneficial for the enhancements in surface lattice oxygen mobility and low-temperature reducibility,while Co_(1) preferred to generate higher contents of the high-valence states of chromium and surface oxygen species as well as adsorption and activation of n-hexane.n-Hexane combustion takes place via the Mars van Krevelen(MvK)mechanism,and its reaction pathways are as follows:n-hexane→olefins or 3-hexyl hydroperoxide→3-hexanone,2-hexanone or 2,5-dimethyltetrahydrofuran→2-methyloxirane or 2-ethyl-oxetane→acrylic acid→CO_x→CO_(2)and H_(2)O.

Effects of carrier and Mn loading on supported manganese oxide catalysts for catalytic combustion of methane

Supported manganese oxide catalysts were prepared by incipient wetness impregnation method for methane catalytic combustion, and effects of the support （Al2O3, SiO2 and TiO2） and Mn loading were investigated. These catalysts were characterized with N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Methane conversion varied in a large range depending on supports or Mn loading. Al2O3 supported 15% Mn catalyst exhibited better activity toward methane catalytic oxidation. The manganese state and oxygen species played an important role in the catalytic performance,

Platinum in-situ catalytic oleylamine combustion removal process for carbon supported platinum nanoparticles

Colloidal synthesis method such as oleylamine(OAm)-stabilized process is of great interest for obtaining uniform and highly dispersed platinum nanoparticle catalysts, yet the ligand may unavoidably inhibit their electro-catalytic performance. Thus, fully removing these ligands is critical to activate catalyst surface. Previous research of OAm removal process pointed that thermal annealing was the most effective way in comparison with other methods such as chemical washing, UV–Ozone irradiation and cyclic voltammetry sweeping, but generally resulting in undesired growth of platinum nanoparticle. Few studies concerning a more efficient ligand removal process have been published yet. In this work we proposed a platinum in-situ catalytic OAm combustion strategy to elucidate the removal mechanism of OAm ligands in thermal process and the key experimental parameters were also optimized. In addition, heat flow signal based on differential scanning calorimetry(DSC) measurement as a sensitive indicator, is suggested to reveal the ligand removal efficiency, which is much more reliable than the traditional spectroscopy.In comparison with commercial Pt/C sample, such a surface clean Pt/C electrocatalyst has shown an enhanced specific activity for oxygen reduction reaction. Our removal strategy and the evaluation method are highly instructive to efficient removal of different organic ligands.

Effect of Novel Supporter on Catalytic Combustion of Methane

A new catalyst support, Ce-Mg-O, was prepared in a novel way macromolecule surfactant modified method and was used as a catalyst support for low-temperature methane combustion. The results indicate that the new type of FeOx/Ce- Mg-O catalyst exhibits high activity in low-temperature methane combustion, such that the T90 at which 90% conversion of methane occurs can be obtained at 560 ℃. The structure of the catalyst and the effect of the supporter on catalytic activity were characterized by transmission electronic microscopy （TEM）, X-ray diffraction （XRD）, and temperature-programmed reduction （TPR）. The results indicate that the high catalytic activity of FeOx/Ce-Mg-O over methane combustion is strongly dependent on the particle size, typical crystal phase of the Ce-Mg-O, and the interaction of FeOx and Ce-Mg-O.

Stable CuO/La_(2)Sn_(2)O_(7) catalysts for soot combustion:Study on the monolayer dispersion behavior of CuO over a La_(2)Sn_(2)O_(7) pyrochlore support

To understand the dispersion behavior of metal oxides on composite oxide supports and with the expectation of developing more feasible catalysts for soot oxidation,CuO/La_(2)Sn_(2)O_(7)samples containing varied CuO loadings were fabricated and characterized by different techniques and density functional theory calculations.In these catalysts,a spontaneous dispersion of CuO on the La_(2)Sn_(2)O_(7)pyrochlore support formed,having a monolayer dispersion capacity of 1.90 mmol CuO/100 m^(2) La_(2)Sn_(2)O_(7)surface.When loaded below this capacity,CuO exists in a sub-monolayer or monolayer state.X-ray photoelectron spectroscopy(XPS),Raman spectroscopy,and Bader charge and density of states analyses indicate that there are strong interactions between the sub-monolayer/monolayer CuO and the La_(2)Sn_(2)O_(7)support,mainly through the donation of electrons from Cu to Sn at the B-sites of the structure.In contrast,Cu has negligible interactions with La at the A-sites.This suggests that,in composite oxide supports containing multiple metals,the supported metal oxide interacts preferentially with one kind of metal cation in the support.The Raman,in situ diffuse reflectance infrared Fourier transform spectroscopy,and XPS results confirmed the formation of both O2^(-)and O2^(2-)as the active sites on the surfaces of the CuO/La_(2)Sn_(2)O_(7)catalysts,and the concentration of these active species determines the soot combustion activity.The number of active oxygen anions increased with increase in CuO loading until the monolayer dispersion capacity was reached.Above the monolayer dispersion capacity,microsized CuO crystallites formed,and these had a negative effect on the generation of active surface oxygen sites.In summary,a highly active catalyst can be prepared by covering the surface of the La_(2)Sn_(2)O_(7)support with a CuO monolayer.

Fault Identification of Internal Combustion Engine based on Support Vector Machine and Fuzzy Neural Network

The internal combustion engine is the main power source of current large⁃scale machinery and equipment.Overhaul and maintenance of its faults are important conditions for ensuring the safe and stable operation of machinery and equipment,and the identification of faults is a prerequisite.Therefore,the fault identification of internal combustion engines is one of the important directions of current research.In order to further improve the accuracy of the fault recognition of internal combustion engines,this paper takes a certain type of internal combustion engine as the research object,and constructs a support vector machine and a fuzzy neural network fault recognition model.The binary tree multi⁃class classification algorithm is used to determine the priority,and then the fuzzy neural network is verified.The feasibility of the model is proved through experiments,which can quickly identify the failure of the internal combustion engine and improve the failure processing efficiency.

Pt/Co_3O_4/3DOM Al_2O_3:Highly effective catalysts for toluene combustion

Three-dimensionally ordered macro-/mesoporous alumina（3DOM Al2O3）-supported cobalt oxide and platinum nanocatalysts（xPt/yCo3O4/3DOM Al2O3,Pt mass fraction（x%）= 0-1.4%,Co3O4 mass fraction（y%） = 0-9.2%） were prepared using poly（methyl methacrylate） templating,incipient wetness impregnation and polyvinyl alcohol-protected reduction.The resulting xPt/yCo3O4/3DOM Al2O3 samples displayed a high-quality 3DOM architecture with macropores（180-200 nm in diameter） and mesopores（4-6 nm in diameter） together with surface areas in the range of 94 to 102m^2/g.Using these techniques,Co3O4 nanoparticles（NPs,18.3 nm） were loaded on the 3DOM Al2O3 surface,after which Pt NPs（2.3-2.5 nm） were uniformly dispersed on theyCo3O4/3DOM Al2O3.The1.3Pt/8.9Co3O4/3DOM Al2O3 exhibited the best performance for toluene oxidation,with a T（90%） value（the temperature required to achieve 90%toluene conversion） of 160 ℃ at a space velocity of20000 mL g^（-1） h^（-1）.It is concluded that the excellent catalytic performance of the 1.3Pt/8.9Co3O4/3DOM Al2O3 is owing to well-dispersed Pt NPs,the high concentration of adsorbed oxygen species,good low-temperature reducibility,and strong interaction between the Pt and Co3O4 NPs,as well as the unique bimodal porous structure of the support.

Catalytic performance enhancement by alloying Pd with Pt on ordered mesoporous manganese oxide for methane combustion

Ordered mesoporous Mn2O3 (meso‐Mn2O3) and meso‐Mn2O3‐supported Pd, Pt, and Pd‐Pt alloy x(PdyPt)/meso‐Mn2O3; x = (0.10?1.50) wt%; Pd/Pt molar ratio (y) = 4.9?5.1 nanocatalysts were prepared using KIT‐6‐templated and poly(vinyl alcohol)‐protected reduction methods, respectively.The meso‐Mn2O3 had a high surface area, i.e., 106 m2/g, and a cubic crystal structure. Noble‐metalnanoparticles (NPs) of size 2.1?2.8 nm were uniformly dispersed on the meso‐Mn2O3 surfaces. AlloyingPd with Pt enhanced the catalytic activity in methane combustion; 1.41(Pd5.1Pt)/meso‐Mn2O3gave the best performance; T10%, T50%, and T90% (the temperatures required for achieving methaneconversions of 10%, 50%, and 90%) were 265, 345, and 425 °C, respectively, at a space velocity of20000 mL/(g?h). The effects of SO2, CO2, H2O, and NO on methane combustion over1.41(Pd5.1Pt)/meso‐Mn2O3 were also examined. We conclude that the good catalytic performance of1.41(Pd5.1Pt)/meso‐Mn2O3 is associated with its high‐quality porous structure, high adsorbed oxygen species concentration, good low‐temperature reducibility, and strong interactions between Pd‐Pt alloy NPs and the meso‐Mn2O3 support.

Catalytic performance and kinetics of Au/γ-Al_2O_3 catalysts for low-temperature combustion of light alcohols

Au/γ-Al2O3 catalysts were prepared by deposition-precipitation method for the catalytic combustion of low concentration alcohol streams(methanol,ethanol,iso-propanol and n-propanol).The catalysts were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffractometry(XRD) and energy dispersive X-ray micro analysis(EDS) techniques.The XPS results showed that there was only Au0 on the surface of catalysts.The XRD patterns showed that Au was presumably highly dispersed over γ-Al2O3.The temperatures for complete conversion of methanol,ethanol,iso-propanol and n-propanol with concentration of 2.0 g/m3 were 60,155,170 and 137 ℃,respectively,but they were completely mineralized into CO2 and H2O at 60,220,260 and 217 ℃ respectively over the optimized catalyst.The activity of the catalyst was stable in 130 h.The kinetics for the catalytic methanol elimination followed quasi-first order reaction expressed as r=0.652 8c0+0.084 2.The value of apparent activation energy is 54.7 kJ/mol in the range of reaction temperature.

Tuning SnO_2 surface with CuO for soot particulate combustion: The effect of monolayer dispersion capacity on reaction performance

With the objective to investigate the structure-reactivity relationship of CuO/SnO2 and eventually design more applicable catalysts for soot combustion,catalysts with different CuO loadings have been prepared by impregnation method.By using X-ray diffraction and X-ray photoelectron spectroscopy extrapolation methods,it is disclosed that CuO disperses finely on the SnO2 support to form a monolayer with a capacity of 2.09 mmol 100 m^-2,which equals 4.8 wt%CuO loading.When the CuO loading is below the capacity,it is in a sub-monolayer state.However,when the loading is above the capacity,CuO micro-crystallites will be formed that coexist with the CuO monolayer.The soot combustion activity of the catalyst increases with the CuO loading until it reaches the monolayer dispersion capacity.A further increase in the CuO loading has no evident influence on the activity.Raman results have testified that with the addition of CuO onto the SnO2 support,a surface-active oxygen species can be formed,the amount of which also increases significantly with the increase in the CuO loading until it reaches the monolayer dispersion capacity.Increasing the CuO loading further has no evident impact on the amount of surface oxygen.Therefore,an apparent monolayer dispersion threshold effect is observed for soot combustion over CuO/SnO2 catalysts.It is concluded that the amount of surface-active oxygen sites is the major factor determining the activity of the catalyst.

含氟材料助燃硼粉研究进展

系统综述了含氟材料助燃硼粉的研究进展,并分析了助燃机制。研究表明,不论无机含氟材料、有机含氟材料还是自组装含氟材料,对硼粉燃烧都有一定的助燃效果。但是,不同含氟材料对硼粉的助燃效果有很大差异,新兴的自组装含氟材料结构规整,可能极具应用价值,值得深入研究。分析表明,含氟材料的助燃机制为氟自由基或含氟基团的自由基的催化作用,该发现对材料的应用场景具有重要参考意义。综合大量文献研究,作者首次提出,氢含量低、易于热解且热解时易产生氟原子及含氟烷烃、含氟烯烃的自由基的材料,对硼粉会具有更好的助燃效果。研究结果预计对火炸药行业从业者会有重要的参考价值。

基于硝化棉助燃的含能粘合剂爆热特征值测试研究

为了表征含能粘合剂的能量特性,开展了含能粘合剂的燃烧热、生成焓与爆热特征值的测试研究并评估了将其作为含能粘合剂能量特性量化指标的合理性,探索了利用硝化棉(NC)助燃来测试含能粘合剂爆热特征值的方法。结果表明:当含能粘合剂/NC质量比达到1∶5时,绝大多数含能粘合剂可以充分燃烧;以硝化棉为助燃物可准确测取含能粘合剂的爆热特征值,所测聚硝酸酯基缩水甘油醚(PGN)与聚乙烯醇硝酸酯(PVN)的爆热特征值分别为3164、4713 kJ·kg^(-1),与文献值的相对误差均小于5%;燃烧热不能准确反映含能粘合剂的能量优势,采用爆热特征值可较好地表征含能粘合剂的能量特性,避免了生成焓正负之分导致估值体系自我矛盾的缺点;在隔绝氧气的条件下,含能粘合剂能量贡献值从小到大依次为GETPE<FATPE<GAP<PBAMO<NC(12%)<PGN <PVN。

基于深度自编码器的城市固废焚烧过程燃烧状态识别

国内城市固废(municipal solid waste,MSW)的组分复杂且多变,其焚烧过程的燃烧状态识别主要依靠人工判断,难以维持稳定的运行工况。针对上述问题,提出了一种基于深度自编码器的分区域燃烧状态识别方法。首先,依据炉排结构对燃烧段和燃烬段的分界线进行标定;然后,利用具有深层结构的卷积稀疏自编码器(convolutional sparse autoencoder,CSAE)提取两部分火焰图像的特征;最后,将特征分别输入到相应的最小二乘支持向量机进行状态识别。基于处理规模为750 t/d的焚烧炉的不同燃烧状态图像进行实验,实验结果表明,在有限的标记样本数量下,所提方法的平均识别准确率为98.04%,该方法能够实现MSW燃烧状态的实时监测。

Catalytic removal of volatile organic compounds using ordered porous transition metal oxide and supported noble metal catalysts

Most of volatile organic compounds （VOCs） are harmful to the atmosphere and human health. Cata‐lytic combustion is an effective way to eliminate VOCs. The key issue is the availability of high per‐formance catalysts. Many catalysts including transition metal oxides, mixed metal oxides, and sup‐ported noble metals have been developed. Among these catalysts, the porous ones attract much attention. In this review, we focus on recent advances in the synthesis of ordered mesoporous and macroporous transition metal oxides, perovskites, and supported noble metal catalysts and their catalytic oxidation of VOCs. The porous catalysts outperformed their bulk counterparts. This excel‐lent catalytic performance was due to their high surface areas, high concentration of adsorbed oxy‐gen species, low temperature reducibility, strong interaction between noble metal and support and highly dispersed noble metal nanoparticles and unique porous structures. Catalytic oxidation of carbon monoxide over typical catalysts was also discussed. We made conclusive remarks and pro‐posed future work for the removal of VOCs.

麦尔兹窑富氧煅烧的生产实践

以某钢厂麦尔兹石灰窑为研究对象,基于其工艺特点,从石灰产量、煤气消耗、石灰质量、废气排放等方面开展富氧煅烧生产实践。富氧煅烧可优化生产指标,加快煤气燃烧速率,提高火焰温度,增强窑内的辐射能力。实践结果表明:将富氧气体φ(O_(2))控制在29%左右可以取得最好的经济效益;富氧煅烧同传统助燃空气煅烧相比,可提高日产75 t,降低助燃空气量25%~35%,节约转炉煤气消耗35.92 m3/t,降低废气排放量19%。

基于改进NSGA-Ⅱ算法的W火焰锅炉燃烧系统多目标优化

以W火焰锅炉为例,首先探讨了可调变量与NOx排放量和锅炉燃烧效率之间的关系,将所得的先验信息采用单调约束的形式与数据驱动建模融合,建立了灰狼优化融合先验知识的支持向量机燃烧特性预测模型。结果表明,该模型提高了预测精度。在此基础上,针对NSGA-Ⅱ算法易陷入极值的问题,加入带有惩罚机制的锦标赛选择策略,对不同工况下的W火焰锅炉进行多目标燃烧优化实验,并提出将归一化环保和经济指标得到的综合效益因子作为评判锅炉燃烧优化结果的标准。实验表明,出力为290MW工况下,综合效益因子提高了7.11%。

Pd基催化剂载体对天然气催化燃烧影响的研究进展

天然气广泛应用于化学品合成和交通运输等领域。甲烷作为天然气的主要成分,具有强温室效应,其不完全燃烧会对环境产生不利影响。催化燃烧技术是解决甲烷不完全燃烧问题的有效方法,其中钯(Pd)基催化剂是该技术的核心,而载体是影响Pd基催化剂甲烷催化燃烧催化活性的重要因素。首先,阐述了甲烷催化燃烧的机理。其次,总结了近年来国内外Pd基催化剂的研究进展:对于多孔颗粒载体型Pd基催化剂,研究聚焦于提升Pd分散性、稳定性与耐热性,以增强催化活性并降低Pd负载量,从而减少成本;而对于整体型Pd基催化剂,研究聚焦于提升有效比表面积、传热传质效率与结构稳定性,以适应大通量甲烷催化燃烧。最后,对用于甲烷催化燃烧的Pd基催化剂载体的未来研究发展趋势进行了展望,包括优化整体型Pd基催化剂骨架载体的涂敷工艺以提高催化效率、采用新型材料替代传统载体材料以制备高性能催化剂,以及进行载体全周期寿命实验以确保催化剂的长期稳定性。

亚氯酸钠助燃特性试验分析研究

为了研究亚氯酸钠的防火措施,首先,通过模拟试验研究了不同引火源和湿度条件下亚氯酸钠的助燃特性;其次,通过离子色谱法测定燃烧残留物中ClO-2的含量,以对亚氯酸钠的助燃效果进行定量分析;最后,基于上述研究,制定针对亚氯酸钠的防火设计策略。结果表明,烟头作为引火源时,亚氯酸钠可使大多数可燃物燃烧,尤其是对含硫物质和山梨酸钾的助燃作用最为显著;机械火花作为引火源时,亚氯酸钠可促进含硫物质和防腐剂燃烧,也能使疏松多孔的可燃物燃烧,但结构致密的布料则难以引燃;白炽灯作为引火源时,亚氯酸钠仅能助燃少数几种还原性较强的物质;而电暖器作为引火源时,亚氯酸钠无法促使样品燃烧。此外,水滴作为引火源时,亚氯酸钠可促使含硫有机物或有还原性的含硫物质燃烧。在33.1%~97.6%的湿度条件下,亚氯酸钠分别与硫磺、硫化钠混合的样品亦可发生燃爆。对亚氯酸钠助燃特性的试验研究可为其生产、存储和运输中的防火需求提供一定的参考。

敞开式阳极焙烧炉火道结构参数与操作参数优化研究

本文以敞开式阳极焙烧炉为例,探究了火道结构和操作参数优化对阳极炭块温差的影响。以原始结构作为工况1,设计了4种优化方案,分别对应工况2~5,探究5种工况下阳极炭块的温差。结果表明,在工况5的情况下阳极炭块的温差最低。随后以工况5为例,探究了助燃空气温度、流量,以及两个喷嘴的燃料流量比例对阳极炭块温差的影响。研究表明,适当提高助燃空气温度和降低助燃空气流量,对提高阳极炭块温度场的均匀分布有积极帮助;当两个喷嘴的燃料流量比例为60%:40%时,阳极炭块的温差最低,此时焙烧炉的热效率最高。

基于DBO-SVM的采空区煤自燃危险性预测

为实现采空区煤自燃危险的准确预警,避免自燃火灾的发生,引入蜣螂优化(dung beetle optimizer,DBO)算法与支持向量机(support vector machine,SVM)算法相结合的煤自燃预测模型。选取O_(2)、N_(2)浓度等十种指标作为自燃预测输入指标,自燃危险性等级作为输出指标,对所建模型进行训练,以四种分类性能评价指标检验模型的预测性能和精度,同时将DBO-SVM模型分别与DBO优化反向传播神经网络(BPNN)模型、粒子群优化算法(PSO)、优化BPNN神经网络模型以及SVM模型的预测结果进行对比分析。结果表明:DBO-SVM模型准确率相较于DBO-BPNN、PSO-BPNN、SVM模型分别提高了1333%、20%、3333%。将DBO-SVM模型应用于山西晋牛煤矿工作面煤自燃预测,该模型能快速准确地对不同矿井采空区煤自燃危险性进行预测,表明DBO-SVM模型相较于其他模型更具普适性和稳定性,更适合钻孔自燃预测。