摘要
利用BET、NH3-TPD、FT-IR、MAS-NMR和SEM等方法研究了经不同F/Nb负载的F-Nb/HZSM-5催化剂的结构和表面酸性,并与乙醇催化脱水制乙烯的反应催化性能进行了关联。结果表明,F-Nb改性后的HZSM-5分子筛发生了明显的脱铝现象,且随着F离子添加量的增加,脱铝越发严重。经27Al MAS NMR测试显示,脱铝后产生了新的非骨架铝物种,其化学位移为-13.5。随F/Nb摩尔比的增大,改性HZSM-5的弱酸、强酸量都减少。当F/Nb摩尔比大于2时,NH3-TPD谱中观察到在500℃的高温区出现新的酸性位。当F/Nb摩尔比为0.7时,F-Nb/HZSM-5催化剂催化低浓度乙醇脱水制乙烯性能得到改善,转化率、选择性和产率均达到最高,且优于HZSM-5分子筛,F/Nb的添加有效延长了催化剂的稳定性。
The structures and surface acidities of F-Nb/HZSM-5 catalysts with different F/Nb mol ratio were studied using BET,NH3-TPD,FT-IR,MAS-NMR and SEM.The catalytic performance of these catalysts for ethanol dehydration to ethylene was evaluated and correlated with the characterization results.It is found that,dealumination of HZSM-5 occurred after modification and the depth of dealumination increased with the increase of the amount of F added.The extra-framework aluminum species were observed by 27Al MAS NMR with a signal appeared at-13.5.With the increase of F/Nb mol ratio,both weak and strong acid amounts decreased and a new strong acid site was found in the NH3-TPD profile at 500℃.The catalyst with F/Nb mol ratio of 0.7 gave the highest catalytic activity and selectivity.The stability of the catalyst was greatly improved by the addition of F-Nb.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2011年第11期850-855,共6页
Journal of Fuel Chemistry and Technology
基金
国家高技术研究发展计划(863计划
2006AA020101)
国家科技支撑计划重点资助项目(2006BAE02B04)
关键词
氧化铌
氟化铵
HZSM-5分子筛
固体酸催化剂
乙醇
乙烯
脱水
niobium oxide
ammonium fluoride
HZSM-5 molecular sieve
solid acid catalyst
ethanol
ethylene
dehydration
