Monolithic Catalysts with Low Noble-Metal Content for Exhaust Purification of Small Gasoline Engines

A series of low noble-metal coment monolithic catalysts for exhaust purification of small gasoline engines was investigated, and it was found that the Pt/Rh-OSM/Al2O3 （where OSM was oxygen storage material） catalyst with Ce0.5Zr0.5-MnOx（3%MnOx） OSM held low light-off temperature for CO, HC, and NO; quite wide three-way window, and outstanding thermal stability. The catalyst could efficiently comrol exhaust emission of small gasoline engines.     

正癸烷高温高压下等压热容测定新方法

针对航空燃料高温高压条件下的等压热容测试,建立了一种新的在线测量装置和测试方法。通过冷、热油对冲混合方式,基于能量守恒原理建立了等压热容的计算公式;基于自制的燃料高温高压流动装置,增加混油和测温部件建立了等压热容测试的实验装置。通过对相关物理量测试不确定度分析,计算得到等压热容的相对扩展不确定度为±3.78%;采用纯水进行标定,验证了该方法测试等压热容的可靠性和精确性。采用航空燃料中的常用组分正十烷,实验测定了在2.1和3.0MPa压力下的等压热容数据,与采用Supertrapp软件的拟合值吻合很好,误差基本在±5%以内。     

超临界状态下正癸烷与环己烷的热裂解

采用连续流动超临界裂解装置,对正癸烷与环己烷在超临界状态下的热裂解进行实验研究和理论分析。同时,采用密度泛函方法在BHHLYP/cc-pVDZ水平上,对两者热裂解过程中起始反应关键步骤的速率常数进行计算。结果表明,相同条件下,正癸烷初始产气温度低于环己烷;低于923K时,正癸烷更容易裂解,其产物主要是C1~C4小分子烃类及C5~C9的直链烯烃,1023K时,两者的裂解程度相当,此时正癸烷裂解产物主要是C1~C4小分子烃类,而环己烷在低于973K时裂解产物以甲基-环戊烷为主,随着温度升高,裂解产物种类增多,当温度达到1023K时裂解产物主要是芳香烃、环烯烃等结焦前驱体,积炭情况比正癸烷严重。相同温度时,正癸烷C—C键断键反应的速率常数比环己烷C—C键和C—H键断键反应速率常数都高,更容易发生裂解反应,理论结果很好地解释了温度低于923K时正癸烷比环己烷更容易裂解的实验现象。     

MnO_x/Ce_(0.5+x)Zr_(0.4–x)La_(0.1)O_(1.95)-Al_2O_3 catalysts used for benzene catalytic combustion

Complete oxidation of benzene over supported manganese oxides catalysts was studied.Composite supports Ce0.5+xZr0.4–xLa0.1O1.95-Al2O3 (x=0,0.1,0.2,0.3,0.4),and CeO2-Al2O3 were prepared by co-precipitation method,and manganese oxides (MnOx) catalysts were prepared by incipient wetness method.Catalytic activity was performed in a conventional fixed bed flow reactor.Among these catalysts,MnOx supported on Ce0.8Zr0.1La0.1O1.95-Al2O3 was found to have the highest catalytic activity for benzene oxidation.The comp...     

不同碱辅助的沉积沉淀法对三效催化剂稳定性的影响

老化处理会导致三效催化剂(TWCs)严重失活, 因此提高催化剂的耐久性能是TWCs设计的目标。本工作采用不同碱辅助的沉积沉淀法, 即尿素辅助沉积沉淀法和氨水辅助沉积沉淀法制备了Pt/Ce_0.4Zr_0.5La_0.05Pr_0.05O₂ (Pt/CZ)三效催化剂, 分析了不同碱对催化剂物理化学性质、催化活性和耐久性的影响。结果表明, 尿素辅助沉积沉淀法(UDP)制备的Pt/CZ催化剂的抗老化性能较差, 而氨水辅助沉积沉淀法(ADP)制备的催化剂的抗老化能力较强。XRD, CO 吸附, XPS和H₂-TPR表征结果表明, ADP中较大的Pt颗粒以及更强的金属载体相互作用使ADP在老化过程中烧结程度较低, 有利于维持催化活性。因此, ADP催化剂具有一定的工业应用前景。     

微通道内TiN、TiO_2涂层的制备及抑焦效果研究

为了缓解换热通道壁面金属催化结焦,在温度为800℃,时间为2 h条件下,实现了内径为2 mm,长度700 mm的304不锈钢管道内表面Ti N涂层的化学气相沉积(CVD);进一步,在700℃的氧化气氛中,将Ti N涂层氧化得到Ti O2涂层。采用扫描电子显微镜(SEM)、能量散射X射线谱(EDS)和X射线衍射(XRD)仪等分别检测了涂层的形貌、元素组成和晶型结构。检测结果表明,CVD法制备的Ti N、Ti O2涂层表面均匀完整,粒子结合紧密,其组成基本符合化学计量比;其中Ti N为立方晶相结构,Ti O2为金红石相结构。以某种碳氢燃料A为原料采用自制的超临界裂解装置对Ti N、Ti O2涂层的抑制结焦效果进行了初步评价。结果表明,与304空白管相比,Ti N涂层管和Ti O2涂层管高温稳定运行时间明显延长,其中Ti N涂层管抑焦效果更加显著。     

Effect of metal doping into Ce0.5Zr0.5O2 on catalytic activity of MnOx/Ce0.5–xZr0.5–xM0.2xOy/Al2O3 for benzene combustion

The research investigated the effect of doping two metals separately or together into Ce0.5Zr0.5O2 on the catalytic activity of MnOx/Ce0.5-xZr0.5-xM0.2xOy/Al2O3 （M=Y, Mn, Y and Mn） for catalytic combustion of benzene. The prepared catalysts were characterized by X-ray diffraction （XRD）, surface area analysis, oxygen storage capacity （OSC）, and H2-temperature programmed reduction （H2-TPR）. Catalytic test was performed on a conventional fixed bed flow reactor. The characterization results revealed that Y and Mn ions entered into the ceria-zirconia mixed oxides framework, which improved the textural properties and greatly promoted the MnOx dispersion on the support surface. The complete conversion temperature of benzene on MnOx/Ce0.4Zr0.4Y0.1Mn0.1Oy/Al2O3 was 563 K, and the selectivity of carbon dioxides was 99%. This catalyst could be applied in a wide range of GHSV and wide concentration condition, showing great potential for application.     

不锈钢表面TiN、TiO_2涂层化学气相沉积制备及抑焦性能研究

为抑制不锈钢材料表面催化结焦,采用常压化学气相沉积法,实现了在10 mm×10 mm×0.9 mm的310S型不锈钢试样表面TiN和TiO_2涂层沉积,沉积温度为850℃,时间为2.5 h。通过SEM、EDS和XRD分析了涂层的形貌特征和组织结构,结果显示,TiN和TiO_2涂层表面均匀完整,粒子结合紧密;氮化钛为立方晶相结构,Ti和N原子比约为1:1,氧化钛的组成为TiO_(1.7)。分别以正己烷、环己烷、苯和RP-3为原料,采用自制的常压裂解装置对2种涂层的抑焦效果进行了评价,结果表明,TiN涂层对4种原料的结焦抑制率分别为99.91%,86.19%,72.36%和94.68%,而TiO_2涂层则为83.39%,85.77%,57.78%和68.57%,TiN涂层具有更优的抑焦性能;310S空白片表面以丝状焦为主,TiN和TiO_2涂层表面以吸附气相结焦为主。     

Effects of ceria/zirconia ratio on properties of mixed CeO_2-ZrO_2-Al_2O_3 compound

A series of CexZr0.50-xAl0.50O1.75(0.05≤x≤0.45) mixed oxides with different Ce/Zr ratio were prepared by co-precipitation method and characterized by means of X-ray diffraction(XRD),Brunauer-Emmet Teller method(BET),temperature-programmed reduction(H2-TPR) and oxygen pulsing technique.The XRD results showed that all samples kept the single CeO2 cubic fluorite structure after calcination at 600 and 1000 oC for 5 h.The results of BET revealed that CexZr0.50-xAl0.50O1.75 with Ce/Zr molar ratio 1/1 exhibited higher specific surface area(212 m2/g) and larger pore volume(0.40 ml/g).For all aged samples,CZA with Ce/Zr molar ratio 3/7 presented the highest specific surface area(104 m2/g) and pore volume(0.34 ml/g).The compounds could still keep prominent structural and textural stability with excellent redox properties even calcined at 1000 oC.     

TiN、Al2O3涂层对燃料裂解结焦的抑制效果研究

为抑制镍基不锈钢油道本身对吸热型碳氢燃料裂解的金属催化结焦积碳作用,采用化学气相沉积法在Ф3 mmφ0.5 mm,800 mm长的3128型不锈钢基体管道内表面分别沉积了TiN和Al2O3涂层,沉积温度分别为950和1050℃,沉积时间为3 h。通过SEM、EDS和XRD分析了涂层的形貌特征和组织结构。SEM结果表明,CVD法制备的TiN、Al2O3涂层结构均匀致密;EDS结果显示,实验制得的氮化钛涂层的组成为非化学计量比的TiN0.67,氧化铝涂层的Al和O原子比为1:3;XRD结果表明,实验所得到的TiN为立方晶相结构,Al2O3为惰性的α-Al2O3。以二甲苯为原料采用自制的超临界裂解装置对TiN、Al2O3涂层的钝化效果进行了评价。二甲苯超临界裂解实验结果表明,TiN涂层钝化效果不明显,而Al2O3涂层的钝化效果十分显著,达到2倍的钝化效果。