摘要
研究了以Na Al O2为铝源时不同碱源对MCM-22分子筛合成的影响。以KOH为碱源时,得到纯相MCM-22分子筛的K/Si O2比值范围变窄;在体系中引入含羟基的低聚物以后,合成纯相K/Si O2的比值范围得以扩大,其原因是羟基与碱羟基的作用降低了碱羟基的活度;在体系中引入硝酸钾,对合成没有影响。可以扩大在Si O2-Na Al O2-HMI-Na OHH2O体系中,以KOH为碱源,加入多羟基低聚物扩大了合成纯相MCM-22的K/Si O2比值范围;而KNO3的引入对合成结果影响较小。以Ba(OH)2为碱源时,当Ba/Si O2≤0.061时,可以得到纯相MCM-22分子筛,且样品的结晶度随着Ba/Si O2比值的增大出现一个最高点,当Ba/Si O2比值继续增大时,也即体系的碱度增大,合成产物则发生从无定形物-混晶的转变。在体系OH-/Si O2比值不变时,以(KOH+Na OH)为碱源,合成产物均为纯相MCM-22,且产物的结晶度随KOH/Na OH比值的增大而有所提高。采用KOH+Ba(OH)2作碱源,保持K/Si O2比值不变,随着Ba/Si O2比值的增大,产物MCM-22的结晶度逐渐减小。当其他因素不变时,合成产物随体系碱度的增大而逐步发生从MCM-22-无定形-转晶的变化;同时,MCM-22分子筛的结晶度随体系碱度的变化出现最大值。
This article analyzes the effect of different alkali sources on the synthesis of MCM-22 molecular sieve when Na Al O2 is used as the aluminum source.When KOH is the alkali source,the K/Si O2 range for synthesizing pure-phase MCM-22 molecular sieve becomes narrower.After a hydroxyl oligomer is introduced in the system,the K/Si O2 range for synthesizing pure-phase MCM-22 molecular sieve widens.This is a result of a lower activity of alkali hydroxyl group due to the reaction of hydroxyl group with alkali hydroxyl group.The introduction of nitrate in the system does not have any effect on synthesis.In the Si O2-Na Al O2-HMI-Na OH-H2 O system,when KOH is used as the alkali source,adding a poly-hydroxyl oligomer can widen the K/Si O2 range for synthesizing pure-phase MCM-22 and the introduction of KNO3 only has little effect on synthesis.If Ba（ OH）2is used as the alkali source, when Ba / Si O2≤0.061,pure-phase MCM-22 molecular sieve can be synthesized and the crystallinity of samples peaked with the increase of the Ba/Si O2 value.When the Ba/Si O2 value continues to increase,i.e.,when the alkalinity of the system increases,the synthesized products change from amorphous substances to mixed crystals.If the OH-/Si O2 value of the system remains unchanged,when（KOH ＋Na OH） is used as the alkali source,all synthesized products are pure-phase MCM-22 and the crystallinity of the synthesized products increases with the KOH/Na OH value.When KOH＋Ba（OH）2is used as the alkali source,if the K/Si O2 value remains unchanged,as the Ba/Si O2 value increases,the crystallinity of synthesized MCM-22 gradually decreases.When other factors do not change,the synthesized product gradually changes from MCM-22 to amorphous substance and to crystal as the alkalinity of the system increases.In ad-dition,the crystallinity of the MCM-22 molecular sieve will peak as the alkalinity of the system changes.
出处
《中外能源》
CAS
2015年第2期74-79,共6页
Sino-Global Energy
