A series of sulfided tertiary NiMoP/ γ Al 2O 3 catalysts with different contents of MoO 3 were prepared by using molybdophosphoric acid of Keggin structure(H 3PMo 12 O 40 ) and nickel nitrate as origins of active pha...A series of sulfided tertiary NiMoP/ γ Al 2O 3 catalysts with different contents of MoO 3 were prepared by using molybdophosphoric acid of Keggin structure(H 3PMo 12 O 40 ) and nickel nitrate as origins of active phase components of molybdenum, phosphorus and nickel, and characterized by TPR technique, with their HDS activity being investigated with thiophene as a model substrate. For the sulfided Mo 0 catalyst containing no nickel as promoter, the only hydrogen sulfide evolution peak Ⅰ is observed at 462 K and attributed to the hydrogenation of the so called edge sulfur atoms chemisorbed on coordinatively unsaturated(cus) Mo x+ sites on the MoS 2 phase(MoS 2 slab). With the introduction of nickel into the active phase of the sulfided Mo 0 catalyst and with the increase of the molybdenum loading, a new hydrogen sulfide evolution peak Ⅱ gradually develops at the low temperature side of the peak Ⅰ, at the same time accompanied by both the increase of the area ratio of the peak Ⅱ to the peak Ⅰ and the shift of the hydrogen sulfide evolution maximum rate to lower temperatures, which may imply the existence of two kinds of active centers related to molybdenum and nickel respectively and the synergic action between the two centers above. It should be noted that for the sulfided NiMoP/ γ Al 2O 3 catalysts, the thiophene HDS rate and the quantity of hydrogen sulfide evolved during TPR process increase monotonously with the atomic ratio of molybdenum to nickel in the form of [ n (Ni)+ n (Mo)]/ n (Ni). On the basis of the results here, the conclusion may be reached that the two kinds of vacancies can be formed on the edge of Ni Mo S slab due to the loss of S during TPR process and vacancies or sites related to the H 2S evolution peak II should be regarded as the mainly active reaction centers of thiophene HDS.展开更多
文摘针对室内全球导航卫星系统(Global navigation satellite system,GNSS)信号受遮挡时,农用车辆协同定位精度低、稳定性差、信号丢包等问题,本文开展面向超宽带(Ultra-wideband,UWB)调频技术的室内外农用车辆协同定位算法研究。首先,搭建三基站多边测距定位模型,实现主基站绝对位置标定以及辅助基站绝对位置坐标的变换求解;其次,提出全质心加权最小二乘的高速双边双向(Weighted least squares high double sided two-way ranging,WLS-HDS-TWR)农机协同定位算法,基于泰勒级数展开的WLS估计算法,求解主车位置。同时,提出面向室内环境的多状态基站组合的UWB定位模块布设模式,并验证其可行性;通过飞行时间法(Time of flight,TOF)获取主从车距离信息,融合GNSS标定位置信息、主车坐标信息以及测距信息,实现主从车协同定位。最后,基于Prescan/Simulink搭建联合仿真平台,验证提出算法的可靠性;通过农用履带车辆开展室内及室外协同定位实车试验,试验结果表明:全质心WLS-HDS-TWR协同定位算法可有效解决室内GNSS信号缺失问题,室内环境下,定位精度较HDS-TWR及全质心LS-HDS-TWR算法分别提高26.98%和22.03%,满足智能农机协同定位作业需求。
文摘A series of sulfided tertiary NiMoP/ γ Al 2O 3 catalysts with different contents of MoO 3 were prepared by using molybdophosphoric acid of Keggin structure(H 3PMo 12 O 40 ) and nickel nitrate as origins of active phase components of molybdenum, phosphorus and nickel, and characterized by TPR technique, with their HDS activity being investigated with thiophene as a model substrate. For the sulfided Mo 0 catalyst containing no nickel as promoter, the only hydrogen sulfide evolution peak Ⅰ is observed at 462 K and attributed to the hydrogenation of the so called edge sulfur atoms chemisorbed on coordinatively unsaturated(cus) Mo x+ sites on the MoS 2 phase(MoS 2 slab). With the introduction of nickel into the active phase of the sulfided Mo 0 catalyst and with the increase of the molybdenum loading, a new hydrogen sulfide evolution peak Ⅱ gradually develops at the low temperature side of the peak Ⅰ, at the same time accompanied by both the increase of the area ratio of the peak Ⅱ to the peak Ⅰ and the shift of the hydrogen sulfide evolution maximum rate to lower temperatures, which may imply the existence of two kinds of active centers related to molybdenum and nickel respectively and the synergic action between the two centers above. It should be noted that for the sulfided NiMoP/ γ Al 2O 3 catalysts, the thiophene HDS rate and the quantity of hydrogen sulfide evolved during TPR process increase monotonously with the atomic ratio of molybdenum to nickel in the form of [ n (Ni)+ n (Mo)]/ n (Ni). On the basis of the results here, the conclusion may be reached that the two kinds of vacancies can be formed on the edge of Ni Mo S slab due to the loss of S during TPR process and vacancies or sites related to the H 2S evolution peak II should be regarded as the mainly active reaction centers of thiophene HDS.
