氮气热处理对硫代硫酸铵预硫化的Mo／Al2O3催化剂的影响

考察了氮气预处理温度对硫代硫酸铵预硫化的Mo/Al2O3催化剂噻吩加氢脱硫(HDS)活性的影响. 采用X射线衍射、高分辨电镜、光电子能谱、热重质谱和硫分析等方法对催化剂进行了表征. 结果表明,预硫化催化剂经80 ℃低温处理并于200 ℃氢气原位活化后噻吩转化率达到最高. 对于氮气低温预处理或常温干燥的预硫化催化剂,载体氧化铝被硫酸根修饰,减少了Mo与载体的相互作用,使得催化剂活化后硫化程度高, MoS2活性相呈多层的Ⅱ型结构,因而HDS活性高. 高于200 ℃的氮气热处理造成硫代硫酸铵的分解,并有少量的多层MoS2活性相生成,但高温热处理造成硫的流失使得活性金属活化后硫化程度偏低,而且MoS2活性相呈现单层的Ⅰ型结构,因而HDS活性较低.     

硫代硫酸铵预硫化的MoO3／Al2O3催化剂的活化和加氢脱硫活性

以硫代硫酸铵为硫化剂对MoO3/Al2O3催化剂进行预硫化,考察了制备方法和活化条件对预硫化催化剂噻吩加氢脱硫活性的影响. 结果表明,硫代硫酸铵预硫化的催化剂活化后,加氢脱硫活性好,噻吩的转化率达到99%以上,而二甲基二硫硫化的MoO3/Al2O3催化剂在相同条件下,噻吩转化率只有92%. 合适的活化温度为200～300 ℃, 活化压力增加有利于预硫化催化剂的还原硫化和加氢脱硫活性的提高. 硫代硫酸铵预硫化催化剂的高脱硫活性主要归因于多层的Ⅱ型MoS2活性相的形成,其次是硫化程度的提高. 硫代硫酸铵预硫化催化剂经过氢气活化和补充硫化两个阶段,其硫化程度高于传统方法硫化的催化剂.     

免预硫化的加氢脱硫MoNiP/Al2O3催化剂的制备和表征

在Mo-Ni-P-O浸渍液中添加一定量的极性有机物如柠檬酸等,采用共浸渍法制备了一种不需预硫化和焙烧也具有较高加氢脱硫活性的MoNiP/Al2O3催化剂,并用N2吸附、程序升温还原、X射线光电子能谱、红外光谱和元素分析对催化剂进行了表征.结果表明,柠檬酸的添加削弱了金属组分与载体间的相互作用,有利于金属组分在载体表面的分散,且改善了催化剂的还原性,使催化剂在与含硫反应物料接触过程中自发硫化,从而有利于催化剂加氢脱硫活性的提高.     

超声波-微波法制备NiW/Al2O3加氢脱硫催化剂

 采用一次浸渍技术制备了NiW/Al2O3加氢脱硫(HDS)催化剂,在制备过程中采用超声波处理浸渍液,采用微波进行样品干燥. 以噻吩为模型化合物,在微反装置上评价了该催化剂的加氢脱硫活性. 使用X射线光电子能谱和透射电镜等表征手段研究了催化剂的表面状态和物化性. 结果表明,使用超声波及微波技术制备的NiW/Al2O3催化剂具有较高的加氢脱硫活性,催化剂的活性组分较易硫化,可生成更多的硫化物种参与反应. 催化剂中硫化态钨的表面原子浓度较高,从而使硫化态钨物种保持较高的表面分散度,有利于增加活性中心的数目. 该催化剂的活性中心结构具有较多配位不饱和的边缘位和棱边位,因而具有较高的加氢脱硫活性.     

磷对预硫化型NiMo/Al2O3催化剂加氢脱硫脱氮性能的影响

利用等体积浸渍法制备了不同磷含量的预硫化型NiMo/Al2O3催化剂,并利用XRD、BET、TPR和HRTEM等分析方法对其进行了表征,研究了磷对其加氢脱硫脱氮性能的影响.结果表明,由于预硫化型NiMo加氢催化剂上活性组分和载体的相互作用较弱,MoS2或Ni-Mo-S相主要以TypeⅡ形式存在,磷通过增加MoS2的堆积...     

活性炭负载的Co-Mo催化剂的加氢脱硫性能 Ⅰ.活性炭载体与γ-Al2O3的对比

 用XRD,TPR和XPS技术对Co-Mo/AC(活性炭)和Co-Mo/γ-Al2O3催化剂进行了表征,并以二苯并噻吩HDS反应评价了催化剂的活性. 在不同温度下处理的催化剂,其活性组分高度分散在活性炭表面,未检测到明显的Mo和Co物种. 在Co-Mo/AC催化剂中,表面物种的还原温度低于Co-Mo/γ-Al2O3的还原温度. 在260 ℃下处理的Co-Mo/AC催化剂,其表面Mo是高价态的Mo(Ⅵ),在500 ℃下处理的Co-Mo/AC催化剂,其表面存在Mo(Ⅴ)和Mo(Ⅵ)两种价态. 硫化态CoMoS/AC催化剂中存在Mo(Ⅳ)和Mo(Ⅴ)两种低价态的Mo物种,而S主要以S2-2和S2-的形式存在于MoS2和MoO3S2-中,还有部分高价态的S6+. 在硫化态CoMoS/γ-Al2O3催化剂中,Mo主要以Mo(Ⅴ)和Mo(Ⅵ)两种状态存在,而S主要以S2-2或S2-的形式存在于MoO2S2-和MoO3S2- 中,还有部分高价态的S6+. 活性评价结果表明,n(Co)/n(Mo)=0.7的Co-Mo/AC的活性高于Co-Mo/γ-Al2O3的活性,而其他Co/Mo比的Co-Mo/AC的活性低于Co-Mo/γ-Al2O3的活性.     

器外预硫化型MoNiP/γ-Al2O3催化剂的二苯并噻吩加氢脱硫活性

 制备了两种器外预硫化型MoNiP/γ-Al2O3催化剂,并以二苯并噻吩为模型化合物考察了其加氢脱硫(HDS)活性,选择了传统的器内预硫化催化剂作为参比. 采用X射线衍射(XRD)、 高分辨透射电镜(HRTEM)和X射线光电子能谱(XPS)等手段对二者在加氢活性相方面的差别进行了研究. 结果表明,器外预硫化催化剂的HDS活性(最高达到99%)与器内预硫化催化剂相当,但是其加氢能力相对较弱. XRD与HRTEM等研究表明,器外预硫化催化剂所形成的MoS2片晶的堆垛层数相对较低,而Mo与S元素的XPS分析结果则说明相对器内预硫化催化剂,器外预硫化催化剂中不但Mo的硫化度较低,而且MoS2活性相的含量亦较少,而二者活性相之间的这种差异应是导致两类催化剂加氢活性不同的主要原因.     

原位分解法制备免预硫化CoMoS／γ-Al2O3催化剂的表征及加氢性能研究

以钼酸铵、硫代乙酰胺为原料合成四硫代钼酸铵溶液,γ-Al2O3为载体,首先浸渍Co盐,再负载四硫代钼酸铵,制备负载钴钼盐的前体.通过考察不同状态助剂钴对催化剂活性的影响,确定金属态存在的助剂钴可以显著提高催化剂的活性.对此前体采用原位分解法制备硫化态CoMoS/γ-Al2O3加氢精制催化剂,并进行XRD、XPS和HRTEM等表征.以FCC柴油为原料,考察了催化剂的活性及稳定性.结果表明,该催化剂的活性组分与载体γ-Al2O3的相互作用较弱,MoS2的分散度较好,堆积层数较高,大部分的MoS2以II型的CoMoS相存在,与传统方法制备的催化剂相比,硫化态的CoMoS/γ-Al2O3加氢精制催化剂具有更高的脱硫性能,1100 h稳定性试验结果表明该催化剂的稳定性较好.     

水热沉积法制备高分散W/Al2O3加氢脱硫催化剂

提出了一种用于制备高分散型W/Al2O3加氢脱硫催化剂的水热沉积法.该方法利用钨酸钠和盐酸在水热条件下的沉积反应生成纳米WO3,通过加入表面活性剂十六烷基三甲基溴化铵可防止WO3颗粒的团聚,从而实现了WO3在Al2O3载体上的高分散负载.采用X射线光电子能谱、高分辨率透射电镜、N2物理吸附以及氢气程序升温还原等技术对W/Al2O3催化剂进行了表征,并以二苯并噻吩的加氢脱硫作为模型反应评价了催化剂的催化性能.结果表明,与采用常规浸渍法制备的具有相同活性组分含量的催化剂相比,采用水热沉积法制备的催化剂具有更高的WO3分散度(表面W/Al原子比从0.051提高到0.061)、更大的比表面积和孔体积;活性组分与载体间的相互作用减弱,WO3的最高还原温度从1 030℃降低到1 015℃,预硫化后催化剂上的活性物种WS2具有更短的片层长度和更高的堆积程度,WS2片层的平均长度从7.78 nm减小到5.71 nm,平均堆积层数从1.23增加到1.41;催化剂对二苯并噻吩的加氢脱硫活性比浸渍法制备的催化剂高15%~18%.     

新型Ni-Mo/Al2O3加氢脱硫催化剂的研究

采用溶胶凝胶技术,制备了双结构Al2O3载体,用此改性载体制备了Ni-Mo/Al2O3催化剂,在中压固定床微反装置上考察了载体改性对催化剂上噻吩加氢脱硫(HDS)活性的影响,并用X射线粉末衍射、透射电镜、吡啶-红外光谱等分析方法对改性载体和催化剂进行了表征。结果表明,由铝溶胶改性载体制备催化剂的加氢脱硫活性均高于未改性载体制备的催化剂的催化活性。XRD和TEM结果表明氧化铝表面负载的铝溶胶经过干燥、焙烧后以纳米尺度的η-Al2O3状态存在,吡啶-红外光谱结果表明,改性氧化铝载体制备催化剂的弱B酸和弱L酸的酸量均提高,强L酸的酸量也明显增加。酸性、酸量的提高和纳米尺度η-Al2O3的存在是催化剂活性提高的主要原因。     

Study of Carbon Nanotube Supported Co-Mo Selective Hydrodesulphurization Catalysts for Fluid Catalytic Cracking Gasoline

In this paper, carbon nanotube supported Co-Mo catalysts for selective hydrodesulphurization （HDS） of fluid catalytic cracking （FCC） gasoline were studied, using di-isobutylene, cyclohexene, 1-octene and thiophene as model compounds to simulate FCC gasoline. The results show that the Co-Mo/CNT has very high HDS activity and HDS/hydrogenation selectivity comparing with the Co-Mo/γ-Al2O3 and Co-Mo/AC catalyst systems. The saturation ratio of cyclohexene was lower than 50%, and the saturation ratio of 1,3-di-isobutylene lower than 60% for the Co-Mo/CNT catalysts. Co/Mo atomic ratio was found to be one of the most important key factors in influencing the hydrogenation selectivity and HDS activity, and the most suitable Co/Mo atomic ratio was 0.4. Co/CNT and Mo/CNT mono-metallic catalysts showed lower HDS activity and selectivity than the Co-Mo/CNT bi-metallic catalysts.     

In situ FT-IR spectroscopy investigations of carbon nanotubes supported Co-Mo catalysts for selective hydrodesulfurization of FCC gasoline

To better understand the nature of carbon nanotubes supported Co-Mo catalysts （Co-Mo/CNTs） for selective hydrodesulfurization （HDS） of fluid catalytic cracking （FCC） gasoline, studies are carried out using in situ Fourier transform infrared spectroscopy （FT-IR）. The catalytic performances of Co-Mo/CNTs catalysts were evaluated with a mixture of cyclohexane, diisobutylene, cyclohexene, 1-octene （60 ： 30 ： 5 ： 5, volume ratio） and thiophene （0.5%, ratio of total weight） as model compounds to simulate FCC gasoline. The HDS experimental results suggested that the HDS activity and selectivity of Co-Mo/CNTs catalysts were affected by Co/Mo ratio; the optimal Co/Mo atomic ratio is about 0.4, and the optimum reaction temperature is 260 ℃. The in situ FT-IR studies revealed that 1-octene can be completely saturated at 200 ℃. In the FT-IR spectra of diisobutylene, the characteristic absorption peak around 3081 cm^-1 for the stretching vibration peak of =C-H bond was still clear at 320 ℃ indicating that diisobutylene is difficult to be hydrogenated. As for the thiophene, no characteristic absorption peak could be found around 3092 cm^-1 and 835 cm^-1 when the reaction temperature was raised to 280 ℃, indicating that thiophene had been completely hydrodesulfurized. On the basis of FT-IR results, it can be deduced that thiophene HDS reaction occurred mainly through direct hydrogenolysis route, whereas thiophene HDS and diisobutylene hydrogenation reaction over Co-Mo/CNTs catalysts might occur on two different kinds of active sites.     

States of Carbon Nanotube Supported Mo-Based HDS Catalysts

The dispersion of the active phase and loading capacity of the Mo species on carbon nanotube (CNT) was studied by the XRD technique. The reducibility properties of Co-Mo catalysts in the oxide state over CNTs were investigated by TPR, while the sulfided Co-Mo/CNT catalysts were characterized by means of the XRD and LRS techniques. The activity and selectivity with respect to the hydrodesulfurization (HDS) performances on carbon nanotube supported Co-Mo catalysts were evaluated. It was found that the main active molybdenum species in the oxide state MoO3/CNT catalysts were MoO2, but not MoO3, as generally expected. The maximum loading before the formation of the bulk phase was lower than 6% (percent by mass, based on MoO3). TPR studies revealed that the active species in the oxide state Co-Mo/CNT catalysts were reduced more easily at relatively lower temperatures in comparison to those of the Co-Mo/γ-Al2O3 catalysts, indicating that the CNT support promoted or favored the reduction of the active species. The active species of a Co-Mo-0.7/CNT catalyst were more easily reduced than those of the Co-Mo/CNT catalysts with Co/Mo atomic ratios of 0.2, 0.35, and 0.5, respectively, suggesting that the Co/Mo atomic ratio has a great effect on the reducibility of the active species. It was found that the incorporation of cobalt improved the dispersion of the molybdenum species on the support, and a phenomenon of mobilization and re-dispersion had occurred during the sulfurization process, resulting in low valence state Mo3S4 and Co-MoS2.17 active phases. HDS measurements showed that the Co-Mo/CNT catalysts were more active than the Co-Mo/γ-Al2O3 ones for the desulfurization of DBT, and the hydrogenolysis/hydrogenation selectivity of the Co-Mo/CNT catalysts was also much higher than those of the Co-Mo/γ-Al2O3. The Co-Mo/CNT catalyst with a Co/Mo atomic ratio of 0.7 showed the highest activity, whereas the catalyst with a Co/Mo atomic ratio of 0.35 had the highest selectivity.     

Pt对Ni2P/MCM-41催化剂加氢脱硫性能的影响

以MCM-41为载体, 采用程序升温还原法制备了含有少量Pt的Ni-P/MCM-41催化剂, 并用氢气程序升温还原(H₂-TPR)、 X射线衍射(XRD)、 N₂吸附比表面积、 X射线光电子能谱(XPS)和透射电子显微镜(TEM)对催化剂的结构和性能进行了表征. 考察了P/Ni摩尔比及Pt含量对Ni-P/MCM-41催化剂催化二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响. 结果表明, Pt能降低Ni₂P催化剂的还原温度, 并有助于Ni₂P相的生成, 抑制团聚现象, 提高催化剂的HDS活性. 当Pt的质量分数为0.6%, P/Ni摩尔比为2时, 催化剂具有最佳加氢脱硫活性, 在340 ℃, 3.0 MPa, 氢油体积比为500, 质量空速(WHSV)为2.0 h^-1的条件下, 二苯并噻吩转化率为100%, 且催化剂加氢脱硫活性在120 h内基本保持稳定.     

不同金属含量Ni-W催化剂的煤焦油加氢脱硫脱氮性能研究

以γ-Al_2O_3为载体,采用等体积浸渍法制备了五种金属原子比相同而金属负载量不同的Ni-W基催化剂。通过X射线衍射(XRD)、光电子能谱(XPS)、程序升温脱附(NH_3-TPD)、氮气吸附、高分辨透射电镜(HRTEM)等技术对催化剂进行了表征。在固定床反应器中,以中低温煤焦油为原料,考察了催化剂的加氢脱氮(HDN)和加氢脱硫(HDS)性能。结果表明,当Ni/W原子比为0.786时,负载金属后,催化剂的总酸量减少,且以中强酸为主。随着金属负载量的增加,催化剂的硫化程度逐渐增加,HDN活性先增加后降低,当WO_3负载量为24%时达到最优值,而HDS活性逐渐增强。     

准“原位”XPS技术研究加氢精制催化剂的硫化过程

用准“原位”XPS技术研究了Mo/Al_2O_3、Mo/TiO_2-Al_2O_3、CO/Al_2O_3、CO/TiO_2-Al_2O_3、Co-Mo-Al_2O_3和Co-Mo/TiO_2-Al_2O_3等催化剂的硫化过程．结果表明：对以Al_2O_3为载体的催化剂，当Mo或Co载量较低(分别低于0.05 gMoO_3/gAl_2O_3或0.03gCoO/gAl_2O_3)时，没有Mo或Co硫化物的生成，而以TiO_2改性的Al_2O_3为载体的催化剂，Mo/TiO_2-Al_2O_3催化剂的硫化较Mo/Al_2O_3容易得多, 表现为在较低温度下，负载在TiO_2改性Al_2O_3载体上的MoO_3，能很快硫化并达到相当大的硫化度, 对Co/Al_2O_3催化剂而言，即使在较高温度400 ℃时，载体上高分散的CoO物种仍难以硫化；而Co_3O_4微晶的硫化却容易得多, 载体用TiO_2改性，并不影响高分散形态的CoO催化剂的硫化，却明显地影响Co_3O_4微晶的硫化．噻吩加氢脱硫(HDS)的活性测量指出，对Co-Mo/Al_2O_3和Co-Mo/TiO_2-Al_2O_3催化剂而言，HDS活性和硫化度之间存在着良好的相关性．并用TiO_2改性载体，可以增加Co-Mo催化剂的HDS活性和硫化度.     

Study of Dibenzothiophene Adsorption Over Carbon Nanotube Supported CoMo HDS Catalysts

Adsorption properties of dibenzothiophene (DBT) on a CNT (carbon nanotube) support as well as on CoMoS/CNT and CoMoO/CNT catalysts have been studied. Consecutive desorption of adsorbates was measured by TGA. The commonly used carriers AC (activated carbon), γ-Al2O3, and their supported catalysts (CoMoO/AC, CoMoS/AC, CoMoO/γ-Al2O3, CoMoS/γ-Al2O3) were also subjected to analysis for comparison. The acidic properties of the samples were characterized using the NH3-TPD technique.Correlation between the adsorption of DBT and the acidic properties of the catalysts has been established.It was found that the Co-Mo catalysts in the sulfide state adsorbed much more DBT molecules than the corresponding Co-Mo catalysts in the oxide state. The CoMoS/CNT catalyst exhibited very high HDS activity and selectivity, as compared with the CoMoS/γ-Al2O3 catalysts. Based on the BET data and the high hydrogenolysis/hydrogenation selectivity of the CoMoS/CNT, it was deduced that more than 90% of the DBT molecules adsorbed on the CoMoS/CNT with an end-on mode, and the surface of the CoMoS/CNT catalyst was almost fully covered with DBT molecules. Although the AC support had very high surface area and high loading ability, the AC supported CoMoS catalyst showed lower HDS activity,as compared with the CoMoS/γ-Al2O3 catalyst.     

介孔碳担载的 Co-Mo 和 Ni-Mo 加氢脱硫催化剂

 自制介孔碳 (CMC) 具有比传统活性碳 (AC) 更大的比表面积、孔径和孔体积, 以其为载体, 在浸渍液中加入螯合剂, 采用等量浸渍法制备了 Co-Mo/CMC 和 Ni-Mo/CMC 催化剂, 分别用于模型汽油和柴油加氢脱硫反应. 结果表明, Co-Mo/CMC 和 Ni-Mo/CMC 催化剂具有比 Co-Mo/AC 催化剂更好的织构性质和加氢脱硫活性. 在模型汽油的加氢脱硫反应中, Co-Mo/CMC 催化剂活性比工业催化剂 Co-Mo/Al2O3 高得多; 而在模型柴油的加氢脱硫反应中, Ni-Mo/CMC 催化剂活性也比工业催化剂 FH-98 高得多.     

磷含量对NiMo/γ-Al_2O_3催化剂活性相结构的影响

采用程序升温还原(TPR)、高分辨透射电镜(HRTEM)和X射线光电子能谱(XPS)表征手段对共浸渍法制备的不同磷含量NiMo/γ-Al2O3催化剂进行了表征,研究了磷含量对NiMo/γ-Al2O3催化剂活性相结构的影响。TPR研究表明,磷能够减少四面体配位Mo物种的数量,增加八面体配位Mo物种的数量,促进高活性Ⅱ型"Ni-Mo-S"活性相的形成。HRTEM研究表明,随磷含量的增加,MoS2颗粒堆积层数增加,催化剂的加氢选择性提高;适量磷能够增加边角位有效Mo原子的分散度(fMo),增加催化剂表面加氢脱硫(HDS)和加氢脱氮(HDN)活性位的数量。上述结论得到了XPS表征的证实:适量磷增加了催化剂表面Mo原子浓度、提高有效助剂比率(PR)和提升比率(Ni/Mo),相应催化剂表现出最高的HDS和HDN活性;但过高磷含量能够引起MoS2颗粒过度堆积,片层长度过长,导致活性位数量减少,催化活性降低。     

全硅MCM-41担载的加氢脱硫催化剂的TPR研究

用TRP技术研究了以全硅MCM-41(Si-MCM-41)和HNO3交换的全硅MCM-41(H-MCM-41)为载体制备的Ni-Mo、Co-Mo和Ni-W加氢脱硫(HDS)催化剂的还原性能，并以0．8(wt)％二苯并噻吩(DBT)的十氢萘溶液为模型化合物，在高压固定床反应器上考察了上述催化剂的加氢脱硫(HDS)反应性能。结果表明，Si-MCM-41经稀HNO3交换后，所担载的Ni-Mo和Ni-W催化剂还原性能、HDS活性和加氢活性有显著变化，但对Co-Mo催化剂影响不大。这说明在Ni-Mo／H-MCM-41和Ni-W／H-MCM-41中可能存在氢溢流现象，DBT的HDS活性与载体表面酸性和氢溢流有关。