载体酸碱性对高硫合成气制甲硫醇的K-Mo-Co催化剂结构和性能的影响

选取3种酸碱性不同的载体(γ-Al2O3,SiO2,MgO)制备由高硫合成气制甲硫醇的负载型K-Mo-Co催化剂。它们的活性高低顺序为:K2MoCo0.35O/SiO2>K2MoCo0.35O/γ-Al2O3>K2MoCo0.35O/MgO;程序升温脱附表征结果显示,这3种不同载体的催化剂与载体的酸碱性强弱顺序一致,弱酸性载体制备的催化剂对合成甲硫醇有利;H2程序升温还原和激光Raman光谱表征结果显示,碱性载体制备的催化剂中,Mo以易于还原和硫化的八面体构型存在,硫化后主要以MoS2存在;弱酸性载体制备的催化剂中,Mo以难于还原和硫化的四面体构型存在,硫化后主要以氧硫钼物种存在,这些物种与合成甲硫醇密切相关

钾修饰的MoO_3/SiO_2催化剂的XRD和TPR表征

采用XRD和TPR测试技术表征了一系列不同K与Mo摩尔比的MoO3/K2O/SiO2催化剂。XRD表征结果显示,随着元素K的加入,多钼物种逐渐被破坏,最终形成了单钼的K2MoO4物种。TPR表征显示,催化剂表面的钼物种有2种结构,即八面体的Mo(Oh)和四面体的Mo(Td)。八面体Mo(Oh)的还原峰在770 K附近,而四面体Mo(Td)还原峰在1 000 K附近;无K的MoO3/SiO2催化剂的低温还原峰出现在840 K,少量元素K的添加削弱了Mo与SiO2之间的作用,使得低温还原峰温度降低到770 K附近;随着元素K添加量的进一步增加,Mo(Oh)物种逐渐减少而Mo(Td)物种逐渐增多,从而使得催化剂表面的Mo更难被还原。高硫合成气制甲硫醇的活性随着钼基催化剂八面体(Oh)钼物种的增加而增加

Effect of Thermal Treatment on Structure and Catalytic Performance of K_2MoO_4-NiO/SiO_2 Catalyst for One-Step Synthesis of Methanethiol from High H_2S-Containing Syngas

王 琪. Tel: (0551)2901458; Fax: (0551)2901450; E-mail: [email protected][中文文摘]在不同焙烧温度和焙烧气氛下对共浸渍法制备的K2MoO4-NiO/SiO2催化剂进行热处理,并采用X射线衍射、热重-差示扫描量热、氢气程序升温还原、拉曼光谱和电子自旋共振波谱等手段对催化剂进行了表征,同时考察了催化剂催化高硫化氢合成气一步法制甲硫醇的性能.结果表明,由于催化剂中所含柠檬酸氧化放热,空气中焙烧的催化剂发生严重烧结.随着焙烧温度的升高,八面体配位的Mo(Oh)逐渐向四面体配位的Mo(Td)转变,导致催化剂的还原能力降低,配位不饱和Mo(CO吸附位)减少,因而CO转化率降低.甲硫醇的生成与Mo–S–K相密切相关,而MoS2晶相表面主要生成烃类.与氮气中焙烧的催化剂相比,空气中焙烧的催化剂表面的MoS2相较多,而Mo–S–K相较少,因此具有更高的烃类选择性和更低的甲硫醇选择性. [英文文摘]K2MoO4-NiO/SiO2 catalyst samples prepared by the co-impregnation method were calcined at different temperatures and atmosphere. X-ray diffraction, thermal gravimetric-differential scanning calorimetry, hydrogen temperature-programmed reduction, Raman spectroscopy, and electron spin resonance techniques were used to characterize the catalyst samples. The catalytic performance of the catalyst for one-step synthesis of methanethiol from high H2S-containing syngas was evaluated. The results showed that the catalyst calcined in air sintered seriously because of the heat release from citric acid oxidation. With the increase of calcination temperature, octahedral coordination Mo(Oh) gradually changed into tetrahedral coordination Mo(Td), which made the reduction of Mo6+ more difficult, decreased the number of CO adsorption sites (coordinatively unsaturated sites) of Mo, and at last led to the decrease of CO conversion. Methanethiol synthesis was closely related to the Mo–S–K phase, and hydrocarbon synthesis was related to the MoS2 phase. Compared with the catalyst calcined in N2, there were more MoS2 phase and less Mo–S–K phase on the surface of the catalyst calcined in air, resulting in the higher selectivity for hydrocarbon and lower selectivity for CH3SH

Study on the K_2MoO_4/SiO_2 Catalysts Promoted by Nickel for Methanethiol Synthesis from High H_2S-Containing Syngas

采用共同浸渍法制备了k_2MOO_4-nIO/SIO_2催化剂,考察了nIO添加量对高硫合成气制甲硫醇k_2MOO_4/SIO_2催化剂性能的影响。活性评价结果表明,添加了nIO的催化剂活性有很大的提高,当nI/MO物质的量比为2/9时,CO转化率为72.6%,较未添加nIO的催化剂提高了一倍多。程序升温还原(TPr)表征显示,添加的nIO与MO有强相互作用,促进了MO物种的还原。电子自旋共振(ESr)表征显示,反应后的催化剂中可检测到“OXO-MO(V)“物种和“THIO-MO(V)“物种,k_2MOO_4-nIO/SIO_2催化剂表面主要为“THIO-MO(V)“物种,而k_2MOO_4/SIO_2催化剂表面主要为“OXO-MO(V)“物种,nIO的添加促进了MO物种的还原、硫化,可能是造成催化剂活性极大提高的原因。The catalysts of NiO loadings on K_2 MoO_4/SiO_2 were prepared by co-impregnated method for methanethiol synthesis.The effect of NiO loading dose on K_2MoO_4/SiO_2 catalystic activity was investigated.The activity evaluating results showed that the activity of K_2MoO_4/SiO_2 catalyst was promoted by NiO obviously,the CO conversion could reach 72.6%over K_2MoO_4-NiO/SiO_2 with 2/9 molar ratio of Ni to Mo,which was more than twice of that over the catalyst without NiO.TPR characterization indicated that there was strong interaction with NiO and Mo,which leaded to the reduction of Mo species more easily.The"oxo-Mo(V)"and"thio-Mo(V)"species in functioning catalysts could be detected by ESR characterization."Thio-Mo(V)"species were dominant on the surface of K_2MoO_4-NiO/SiO-2 catalysts,but the"thio-Mo(V)"species were dominant for K_2MoO_4/SiO_2 catalyst, which indicated that the adding of NiO could promote the reduction and sulfurization of Mo species.And This maybe the reason of the good activity of K_2MoO_4-NiO/SiO_2 catalyst.德国Degussa公司的经费资

高硫合成气制甲硫醇K_2MoO_4/SiO_2催化剂的研究 Ⅰ.镍的促进作用

采用共同浸渍法制备了K_2MoO_4-NiO/SiO_2催化剂,考察了NiO添加量对高硫合成气制甲硫醇K_2MoO_4/SiO_2催化剂性能的影响。活性评价结果表明,添加了NiO的催化剂活性有很大的提高,当Ni/Mo物质的量比为2/9时,CO转化率为72.6%,较未添加NiO的催化剂提高了一倍多。程序升温还原(TPR)表征显示,添加的NiO与Mo有强相互作用,促进了Mo物种的还原。电子自旋共振(ESR)表征显示,反应后的催化剂中可检测到"oxo-Mo(V)"物种和"thio-Mo(V)"物种,K_2MoO_4-NiO/SiO_2催化剂表面主要为"thio-Mo(V)"物种,而K_2MoO_4/SiO_2催化剂表面主要为"oxo-Mo(V)"物种,NiO的添加促进了Mo物种的还原、硫化,可能是造成催化剂活性极大提高的原因