微波辐射对Fe/ZSM-5甲醇转化催化剂酸性的影响

IF 0.9 Q4 CHEMISTRY, MULTIDISCIPLINARY
T. S. Ntelane, Themba E. Tshabalala, C. M. Masuku, M. Scurrell
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Thus, the concentration of acid sites\nmore precisely, the number of Brønsted acid sites, is vital in determining the activity of ZSM-5 zeolite\nand product distribution in the methanol-to-hydrocarbons reaction.\n\n\n\n(1) To modify ZSM-5 using an iron solution to form Fe/ZSM-5 via the impregnation\nmethod.\n\n(2) To tune the acidic properties of Fe/ZSM-5 using microwave radiation.\n\n(3) To check and determine the concentration of acidic sites using n-propylamine temperature-programmed\nsurface reaction.\n\n(4) To check the effect of microwave radiation and acidic properties in the methanol conversion\n(product distribution) via methanol temperature-programmed surface reaction.\n\n\n\nTwo sets of zeolites were used, with iron being introduced by ion-exchange from ferric\nnitrate (Fe(NO3)3 9H2O, Sigma Aldrich, ≥ 98% metal) solutions. These two series were designated\nas Z (0.5FeZ10/0-700) and X (0.5FeX10/0-700) after microwave treatment. The Z and X series possess the\nSi/Al framework ratio of 30 and 80, respectively. The TPSR studies were then conducted for characterization\nand catalytic tests.\n\n\n\nFrom the C3H9N-TPSR experiments, it was found that the concentration of Brønsted acid\nsites decreased with increasing microwave power level. Both X and Z series exhibited high selectivity\nto propene than ethene. Microwave treated catalysts (0.5FeZ10/280 and 0.5FeX10/462) with decreased\nconcentration of Brønsted acid sites showed the highest propene/ethene ratios of 1.67 and\n5.27, respectively.\n\n\n\nFrom the results obtained, it was found that the amount of methane evolved (as a measure\nof coke deposited) and the concentration of Brønsted acid sites decreased with increasing microwave\npower level (0-700 Watts). High selectivity to propene was found when using both X series\n(0.5FeX10/0-700) and Z series (0.5FeZ10/0-700) as catalysts. 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引用次数: 0

摘要

采用微波辐射作为后处理方法,对Fe/ZSM-5催化剂的酸性进行了调整。ZSM-5沸石是甲醇转化烯烃和高辛烷值汽油系列碳氢化合物中广泛使用的标准催化剂。然而,焦炭的沉积和酸性位点的浓度决定了其整体催化活性。因此,确切地说,酸性位点的浓度,即Brønsted酸性位点的数量,对于确定ZSM-5沸石的活性和甲醇-烃反应中产物的分布至关重要。(1) 用铁溶液对ZSM-5进行改性,通过浸渍法形成Fe/ZSM-5。(2) 利用微波辐射调节Fe/ZSM-5的酸性性质。(3) 使用正丙胺温度程序化表面反应检查和测定酸性位点的浓度。(4) 通过甲醇温度程序化表面反应,检查微波辐射和酸性性质对甲醇转化(产物分布)的影响。使用两组沸石,通过离子交换从硝酸铁(Fe(NO3)3 9H2O,Sigma-Aldrich,≥98%金属)溶液中引入铁。这两个系列在微波处理后被命名为Z(0.5FeZ10/0-700)和X(0.5FeX10/0-700)。Z和X系列的Si/Al骨架比分别为30和80。然后进行了TPSR研究以进行表征和催化测试。从C3H9N-TPSR实验中发现,Brønsted酸性位点的浓度随着微波功率水平的增加而降低。X和Z系列对丙烯的选择性均高于乙烯。Brønsted酸中心浓度降低的微波处理催化剂(0.5FeZ10/280和0.5FeX10/462)显示出最高的丙烯/乙烯比,分别为1.67和5.27。从获得的结果中发现,随着微波功率水平(0-700瓦)的增加,甲烷的释放量(作为沉积焦炭的测量)和Brønsted酸位点的浓度降低。当使用X系列(0.5FeX10/0-700)和Z系列(0.5Fe Z10/0-700)作为催化剂时,发现对丙烯的高选择性。在使用微波处理降低Brønsted酸的浓度后,0.5FeX10/280、0.5FeX10/462、0.5FeZ10/280和0.5FeZ10/462催化剂的P/E比最高。有理由认为,微波辐射可能是生产ZSM-5基催化剂的一个可行的合成后改性步骤,该催化剂表现出降低的Brønsted酸位点浓度、减少的乙烷形成、提高的催化活性和选择性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Microwave Radiation Effects on the Acidic Properties of Fe/ZSM-5 Catalysts for Methanol Conversion
To use the microwave radiation as the post-treatment method to tune the acidic properties of Fe/ZSM-5 catalyst. ZSM-5 zeolite is a widely used standard catalyst in the methanol conversion to olefins and high-octane gasoline range hydrocarbons. However, the coke deposition and the concentration of acid sites determine its overall catalytic activity. Thus, the concentration of acid sites more precisely, the number of Brønsted acid sites, is vital in determining the activity of ZSM-5 zeolite and product distribution in the methanol-to-hydrocarbons reaction. (1) To modify ZSM-5 using an iron solution to form Fe/ZSM-5 via the impregnation method. (2) To tune the acidic properties of Fe/ZSM-5 using microwave radiation. (3) To check and determine the concentration of acidic sites using n-propylamine temperature-programmed surface reaction. (4) To check the effect of microwave radiation and acidic properties in the methanol conversion (product distribution) via methanol temperature-programmed surface reaction. Two sets of zeolites were used, with iron being introduced by ion-exchange from ferric nitrate (Fe(NO3)3 9H2O, Sigma Aldrich, ≥ 98% metal) solutions. These two series were designated as Z (0.5FeZ10/0-700) and X (0.5FeX10/0-700) after microwave treatment. The Z and X series possess the Si/Al framework ratio of 30 and 80, respectively. The TPSR studies were then conducted for characterization and catalytic tests. From the C3H9N-TPSR experiments, it was found that the concentration of Brønsted acid sites decreased with increasing microwave power level. Both X and Z series exhibited high selectivity to propene than ethene. Microwave treated catalysts (0.5FeZ10/280 and 0.5FeX10/462) with decreased concentration of Brønsted acid sites showed the highest propene/ethene ratios of 1.67 and 5.27, respectively. From the results obtained, it was found that the amount of methane evolved (as a measure of coke deposited) and the concentration of Brønsted acid sites decreased with increasing microwave power level (0-700 Watts). High selectivity to propene was found when using both X series (0.5FeX10/0-700) and Z series (0.5FeZ10/0-700) as catalysts. After decreasing the concentration of Brønsted acid using microwave treatment, the highest P/E ratios were observed for 0.5FeX10/280, 0.5FeX10/462, 0.5FeZ10/280 and 0.5FeZ10/462 catalysts. It is reasonable to suggest that microwave radiation could be a feasible post-synthesis modification step to produce ZSM-5 based catalysts that exhibit reduced concentration of Brønsted acid sites, reduced methane formation, increased catalytic activity and selectivity.
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来源期刊
Current Microwave Chemistry
Current Microwave Chemistry CHEMISTRY, MULTIDISCIPLINARY-
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