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甲烷脱氢芳构化W/HZSM5基催化剂的制备
STUDY OF PREPARATION OF W/HZSM 5 BASED CATALYSTS FOR NON OXIDATIVE DEHYDRO AROMATIZATION OF METHANE

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甲烷脱氢芳构化W_HZSM_5基催化剂的制备.pdf (1.190Mb)
Date
1999-01
Author
熊智涛
曾金龙
张鸿斌
林国栋
蔡启瑞
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  • 化学化工-已发表论文 [14469]
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Abstract
[中文摘要]由H2SO4酸化的(NH4)2WO4溶液(pH=2~3)制备的WH2SO4/HZSM5催化剂对甲烷脱氢芳构化(DHAM)反应的催化活性比不经酸化的(NH4)2WO4溶液(pH=8~9)制备的W/HZSM5催化剂高得多.氧化前驱态催化剂的H2TPR研究表明,WH2SO4/HZSM5试样的还原所需温度比W/HZSM5低得多;前者可还原至较低价态的W物种在负载总W量中所占比例也比后者高得多.H2TPR及相关体系的EPR和Raman表征结果相互佐证表明,用H2SO4酸化导致负载钨酸铵前驱溶液中一些由共边正八面体配位结构单元(WO6)n-构成的聚钨酸根物种的生成;WH2SO4/HZSM5催化剂对DHAM反应催化活性之所以高,主要由于所负载的W前驱物种较大部分是(WO6)n-基的W物种,而非(WO4)2-基W物种;在较低温度下就可被还原,且在DHAM反应条件下有一部分可还原至较低价态W4+的(WO6)n-物种很可能是催化活性位的前驱组成部分.[英文摘要]It has been found experimentally that the acidification of the solution of (NH 4) 2WO 4 used for impregnation by H 2SO 4 enhances markedly the activity of the W/HZSM 5 based catalysts for non oxidative dehydro aromatization of methane (DHAM). The H 2 TPR results indicated that the temperature required for the H 2 reduction of the catalyst precursor of the W H 2SO 4/HZSM 5 derived from acidified solution of (NH 4) 2WO 4 (with pH=2~3) was much lower than that of the W/HZSM 5 derived from non􀀁acidified solution of(NH4)2WO4(with pH =8~9).It was estimated that, in the temperature region of 298~1200 K,the propor- tions of the W-species reducible to W5+ and W4+ in the total amount of loaded W for the former were~3.2 and ~ 10 times as high as that for the latter, respectively. This along with the results of the EPR and Raman investigat ions of the related systems 􀀁would be in favor of the following viewpoint, i e ,that the acidification by H2SO4 resulted in the formation of polytungstates species being built of octahedral group (WO6)n-sharing edges, via the reaction such as 6( WO4)2- + 7H+ = ( HW6O21)5- +3H2O, in the precursor solution, and that (WO6)n- derived W-species were more easily reduced by H2 than those derived from (WO4)2- , and that the high DHAM activity was closely correlated with the polytungstate group (WO6)n- as precursor of catalytically active species.
Description
第一作者: 熊智涛, 男, 1972 年生, 博士生.联系人: 张鸿斌.国家自然科学基金(批准号29392002) 和教育部博士点科研基金资助项目.
Citation
催化学报,1999,20(1):35-40
URI
https://dspace.xmu.edu.cn/handle/2288/10579

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