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1.
考察了在含氧化铝载体条件下,不同Zn负载量改性后HZSM-5催化剂的MTA反应性能。采用BET、XRD、PyFTIR、NH3-TPD和H2-TPR等分析手段对催化剂进行表征。实验结果表明,氧化铝载体的加入使得HZSM-5催化剂产生了介孔并且增强了Zn物种在催化剂表面的稳定性;Zn物种的加入破坏了HZSM-5分子筛的骨架结构、改变了催化剂表面酸性;此外,Zn物种的加入可以促进MTA过程脱氢反应的进行,中间产物烯烃的后续芳构化过程受到抑制;在实验的考察范围内,当Zn负载量为0.5%(质量分数)时,芳烃(C6~11)收率存在最大值21.0%(质量分数);甲醇的芳构化能力会受到生焦的抑制,然而,再生后的催化剂呈现更高的芳烃收率。 相似文献
2.
Yi-Ping Zhang Dong-jie Wang Jin-hua Fei Xiao-ming Zheng 《Reaction Kinetics and Catalysis Letters》2001,74(1):151-161
The influence of Zn content, reaction temperature and pretreatment conditions on a Zn-modified Mo/HZSM-5 catalyst for methane
aromatization were studied. It was found that the addition of Zn promoted the reaction. Methane conversion of 10.9% and aromatics
selectivity of 96.7% were obtained with a Zn/Mo molar ratio of 0.03 and N2 pretreatment at 973 K. The results of isopropanol decomposition, NH3-TPD and TG-DTA suggest that the addition of Zn decrease the acidity of the catalyst, which may be the reason for the high
activity on the Mo-Zn/HZSM-5 catalyst.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
DEHYDROGENATION AND AROMATIZATION OF METHANE IN THE ABSENCE OF OXYGEN OVER DOPED Mo/HZSM-5 CATALYSTS
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研究了在Mo/HZSM-5催化剂上添加助剂以及不同的反应预处理温度对甲烷无氧脱氢芳构化反应的影响。实验结果表明,由于第二组分的添加,Mo/HZSM-5催化剂的活性和选择性都得到了较大程度的改善。预处理温度是影响催化剂反应性能的关键因素。Mo-Ru/HZSM-5催化剂经过873K空气预处理后,甲烷在973K的转化率约为10%,催化剂的稳定性也得到较大程度的提高。TPSR实验结果表明,Ru的加入降低了芳烃生成的温度。TPO和DTA实验结果表明,在Mo-Ru/HZSM-5催化剂上可生成较多的碳物种,结合反应结果,可以认为反应过程中生成的碳物种对甲烷的无氧脱氢芳构化反应是起积极作用的 相似文献
4.
W掺杂对Mo/HZSM催化甲烷无氧芳构化性能的影响 《燃料化学学报》2017,45(11):1384-1391
采用浸渍法制备了Mo/HZSM-5、Mo-W/HZSM-5和W/HZSM-5三种催化剂。通过XRD、BET、Py-FTIR、H2-TPR、XPS、TEM、NH3-TPD、TPO、TG和Raman等技术对催化剂的物化性质进行表征,并考察其在甲烷无氧芳构化反应中的催化性能。结果表明,相比于Mo/HZSM-5,Mo-W/HZSM-5催化剂表现出更高的CH_4转化率、芳烃收率以及催化稳定性。H_2-TPR和XPS结果表明,Mo-W/HZSM-5中存在更易被还原为W~(4+)的正八面体(WO_6)~(n-)前驱体,反应过程中W4+的形成有助于提高CH_4转化率。同时,积炭表征结果表明,石墨型积炭是导致Mo/HZSM-5催化剂快速失活的主要原因,W掺杂可以抑制MoW/HZSM-5催化剂上石墨型积炭的形成,进而提高催化剂的稳定性。 相似文献
5.
不同锌盐改性的HZSM-5催化剂上甲醇芳构化反应 总被引:3,自引:0,他引:3
分别用ZnSO4,Zn(AcO)2,Zn(NO3)2和ZnCl2溶液对HZSM-5分子筛浸渍改性得到不同Zn盐改性的HZSM-5催化剂.采用X射线衍射、N2物理吸附、热重-质谱分析、氨程序升温脱附和吡啶吸附红外光谱等方法对改性后的催化剂进行了表征,并在固定床反应装置上考察了其甲醇芳构化反应性能.结果表明,不同Zn盐改性的HZSM-5催化剂上Zn物种的存在形式不同会导致其表面酸中心强度与分布具有较大差异,经ZnSO4改性的HZSM-5催化剂表面上强B酸中心和Zn物种的存在使其表现出最佳的甲醇芳构化反应性能. 相似文献
6.
Low-temperature activation of methane over rare earth metals promoted Zn/HZSM-5 zeolite catalysts in the presence of ethylene
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At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons (C2–C4) and aromatics (C6–C10), through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed. 相似文献
7.
8.
《Journal of Energy Chemistry》2015,(3)
Long-term stability test of Mo/HZSM-5-N catalysts(HZSM-5-N stands for nano-sized HZSM-5) in methane dehydroaromatization(MDA)reaction has been performed with periodic CH4-H2 switch at 1033-1073 K for more than 1000 h.During this test,methane conversion ranges from 13% to 16%,and mean yield to aromatics(i.e.benzene and naphthalene) exceeds 10%.N2-physisorption,XRD,NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition,and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke,thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition.The effect of zeolite particle size on the catalytic activity was also explored,and the results showed that the nano-sized zeolite with low diffusion resistance performed better.It is recognized that the size effect was enhanced by reaction time,and it became more remarkable in a long-term MDA reaction even at a low space velocity. 相似文献
9.
在反应温度下以1%O2对Mo/MCM-22催化剂的原位再生 总被引:1,自引:0,他引:1
In recent years, the catalytic dehydroaromatization of methane to yield aromatics has been a challenging and intriguing topic in heterogeneous catalysis. Until now, the two effective methane dehydroaromatization catalysts are Mo/HZSM-5[1] and Mo/MCM-22[2]. However, this reaction suffers from rapid catalyst deactivation due to coking[3]. 相似文献
10.
《Journal of Saudi Chemical Society》2019,23(5):612-626
The promotional effect of Fe-Mo species introduced into HZSM-5 (Zeolyst Int., SiO2/Al2O3 ≈ 30) zeolite catalyst by the wetness impregnation method for the 1-hexene aromatization was investigated. The structure and catalytic performance for the aromatization of 1-hexene over xFeyMo-ZSM-5 catalysts in comparison with unmodified HZSM-5 catalysts were studied. The xFeyMo-ZSM-5 catalysts contain fixed loading (5 wt%) and variable Fe/Mo ratio. The catalysts were characterized by BET, ICP-AES, HRSEM-EDS, HRTEM, XRD, FTIR, H2-TPR, NH3-TPD, and pyridine DRIFT spectroscopy. The characterization data confirmed the existence of Fe and Mo species in the zeolite matrix. With Fe and Mo species implementation to HZSM-5 zeolite, the amount of the acid sites decreased, but the selectivities to C9+ aromatics increased. The catalyst evaluation was performed at 350 °C for 6 h on-stream at atmospheric pressure using a fixed-bed quartz tube reactor. The selectivity to products of different carbon number was affected by the Fe/Mo ratio within the zeolite. It was found the product distribution of grouped fractions of C1–C17+ from the liquid product. The results indicate that the optimum ratio of Fe/Mo is 1–1.5. The highest selectivity for gasoline and distillate ranges was obtained for the 2.5wt%Fe2.5wt%Mo- and 3wt%Fe2wt%Mo-ZSM-5 samples, which was higher than that for parent HZSM-5 catalyst. 相似文献
11.
Impregnation,mechanical mixing and hydrothermal treatment methods were used to introduce molybdenum species into the HZSM-5 zeolite ,the structure and surface acidity of the catalysts were studied by means of XRD,FT-IR ,NH3-TPD,TPR and XPS,The effects of Mo content and reaction time on stream on the aromatization of propane were investigated,It was found that the performance of the Mo/HZSM-5 catalst prepared by the hydrothermal treatment method was much better than that of the other two catalysts,For example ,under the reaction conditions of 823 K and 600h^-1, propance conversion and aromatics selectivity over the catalyst prepared by hydrothermal pretreatment could reach 89.17% and 78.56%,respectively,XRD and XPS results showed that the Mo species in the catalysts prepared by hydrothermal treatment were highly dispersed on the surface of the HZSM-5,and lartger amounts of them could penetrate into the HZSM-5 channel ,as compared with the other two kinds of catalysts,These factors may be responsibled for their high activities for propane aromatization,IR and NH3-TPD studies indicated that the number of Broensted acid centers decreased and the Lewis acid centers increased after Mo was introduced into the HZSM-5 zeolite. 相似文献
12.
采用浸渍法制备了La改性HZSM-5分子筛催化剂,利用X射线衍射(XRD)、氮气吸附-脱附、氨气程序升温脱附(NH3-TPD)以及吡啶吸附红外光谱(Py-FTIR)技术对催化剂进行表征,并在固定床微型反应评价装置上,在反应温度350℃,系统压力0.1 MPa,甲醇质量空速4.74 h-1的条件下,考察La改性HZSM-5分子筛催化剂的甲醇转化制汽油反应性能。结果表明,La改性HZSM-5分子筛催化剂的酸量降低,比表面积和孔容减小。La负载量为4%时,其MTG反应性能最佳,催化剂的寿命和汽油收率分别由改性前的12 h和52.69%增加到16 h和59.28%。此外,随着La负载量的增加,汽油中芳烃含量显著降低,降幅达18%。 相似文献
13.
Junwei Wang Maoqing Kang Zhixin Zhang Xinkui WangInstitute of Coal Chemistry Chinese Academy of Sciences Taiyuan China Manuscript received December revised March 《天然气化学杂志》2002,(Z1)
Impregnation, mechanical mixing and hydrothermal treatment methods were used to introduce molybdenum species into the HZSM-5 zeolite. The structure and surface acidity of the catalysts were studied by means of XRD, FT-IR, NH3-TPD, TPR and XPS. The effects of Mo content and reaction time on stream on the aromatization of propane were investigated. It was found that the performance of the Mo/HZSM-5 catalyst prepared by the hydrothermal treatment method was much better than that of the other two catalysts. For example, under the reaction conditions of 823 K and 600 h-1, propane conversion and aromatics selectivity over the catalyst prepared by hydrothermal pretreatment could reach 89.17% and 78.56%, respectively. XRD and XPS results showed that the Mo species in the catalysts prepared by hydrothermal treatment were highly dispersed on the surface of the HZSM-5, and larger amounts of them could penetrate into the HZSM-5 channel, as compared with the other two kinds of catalysts. These factors may be responsi 相似文献
14.
YU Yue XI Zhixiang ZHOU Bingjie JIANG Binbo LIAO Zuwei YANG Yao WANG Jingdai HUANG Zhengliang SUN Jingyuan YANG Yongrong 《高等学校化学研究》2022,38(4):1012-1017
Acidity plays a vital role in methane conversion by co-feeding method, which is one of the best strategies to improve the utilization and gentle the reaction conditions of methane. In this work, Zn, Ni, Mo, La, Ga, Fe and Co-impregnated ZSM-5 zeolites have been prepared with the same substitutions to variate the acidities and tested in co-aromatization of methanol with methane. It is demonstrated that the new medium-strong acid sites formed by metal and strong acid sites are the key role to activate methane in co-reaction. Zn-modified ZSM-5 catalyst is preferred to exhibit the best methane conversion of 12%, whose aromatic selectivity increases from 27.2% to 52.2% compared with that of HZSM-5. Besides, the addition of methane further improves the production of high-valued aromatics compared with methanol to aromatics (MTA) reaction. 相似文献
15.
Aromatization of methane over different Mo-supported catalysts in the absence of oxygen 总被引:2,自引:0,他引:2
Tan Pinglian Xu Zhusheng Zhang Tao Chen Liayuan Lin Liwu 《Reaction Kinetics and Catalysis Letters》1997,61(2):391-396
Both acidity and structure of the support are important factors in converting methane to aromatics. Lower SiO2/Al2O3 ratio seems to favor the aromatization of methane over the Mo/HZSM-5 catalyst. When Pt is added as a modifier the activity
of Mo/HZSM-5 catalyst will decrease slightly, but coke formation will enhanced. 相似文献
16.
YipingZhang DongjieWang JinhuaFei XiaomingZheng 《天然气化学杂志》2003,12(2):145-149
Mo/HZSM-5 is a good catalyst for methane aromatization, and the reaction performance of Mo/HZSM-5 and Cu modified Mo/HZSM-5 catalysts under various pretreatment conditions has been studied. The results indicate that the catalyst presented a distinguished catalytic activity, benzene selectivity and a high stability when the bed temperature was raised in N2 atmosphere. 相似文献
17.
在Zn/P/ZSM-5催化剂上研究了甲醇、二甲苯、甲苯和甲醇等不同进料下芳烃产品分布随反应积碳的变化, 发现催化剂积碳对芳构化反应、脱烷基反应和烷基化反应的影响不同. 在不同硅铝摩尔比(Si/Al 比)和Zn负载量的Zn/P/ZSM-5 催化剂上进行甲醇转化, 考察催化剂酸性位点强度、密度和类型与芳烃收率和产品分布之间的关系, 发现当强酸位点酸密度下降时, 脱烷基反应最先被抑制, 其次是芳构化反应和异构化反应, 而烷基化反应却不受影响. 在Si/Al 比为14, 3% (w) Zn 负载量的Zn/P/ZSM-5 催化剂上可得到75%左右的芳烃收率, 二甲苯收率在35%左右, 具有重要的工业应用前景. 相似文献
18.
采用等量浸渍法制得一系列不同担载量的Mo/HZSM-5催化剂,运用XRD和FTIR方法考察了Mo物种在催化剂表面的分散状态,首次采用微分吸一热技术对Mo/HzSM-5催化剂的表面酸性进行表征。同时研究了催化剂对丙烷芳构化的反应活性。结果表明:对于担载Mo的HZSM-5分子筛催化剂,Mo物种在HZSM-5分子筛表面上顺序为HZSM-5〉1%Mo/HZSM-5〉2%Mo/HZSM-5分子筛本身表面的酸 相似文献
19.
Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics(MTA)reaction,which is often attributed to the metal promoting the aromatization of intermediate olefins.However,the effect of methanol dehydrogenation on aromatics formation over these catalysts is rarely studied.Here,we report that HCHO,which is formed by methanol dehydrogenation over Zn/H-ZSM-5 prepared by Zn impregnation,can participate in the synthesis of aromatics.Methanol conversion can produce more aromatics than olefins(propylene or ethylene)conversion over Zn/H-ZSM-5,indicating the conventional MTA pathway including methanol-to-olefins and olefins-to-aromatics is not complete.Moreover,an MTA mechanism including the conventional pathway and the methanol and HCHO coupling pathway is systematically proposed. 相似文献
20.
MCM-41和HZSM-5协同催化对油菜秸秆热解的影响 总被引:2,自引:0,他引:2
MCM和HZSM协同催化对油菜秸秆热解的影响 《燃料化学学报》2016,44(10):1195-1202
以油菜秸秆为原料,采用两种方案分层布置催化剂(HZSM-5/MCM-41和MCM-41/HZSM-5),并与MCM-41和HZSM-5单独催化进行对比,从生物油品质和催化剂耐久性两个角度探究协同催化作用机理;对精制生物油有机相进行理化特性分析,采用FT-IR和GC-MS进行成分分析,对催化剂进行耐久性分析。结果表明,与单独催化相比,协同催化所得精制生物油液相产率略有降低,气相产率升高,精制生物油有机相理化特性进一步提高,其中,MCM-41/HZSM-5协同催化所得精制生物油有机相热值较高,为34.31 MJ/kg;精制生物油有机相中含有多种芳香族类物质和少量的羰基类物质,协同催化较单独催化能产生较多的烃类物质及较少的含氧芳香族类物质,其中,MCM-41/HZSM-5协同催化所得精制生物油有机相中烃类物质含量较高,且以单环芳香烃为主;HZSM-5分子筛在300-800℃有两个失重峰,MCM-41分子筛在300-800℃仅有一个失重峰,表明MCM-41催化剂上沉积的焦炭成分单一,较易去除,且协同催化后分子筛表面沉积的焦炭总含量较少。 相似文献