RE-Y分子筛离子交换条件对稀土利用率的影响

Effect of ion exchange conditions on rare earth utilization rate of RE-Y zeolite

考察了NaY分子筛稀土离子(RE^(3+))交换过程的稀土投料量(稀土与分子筛质量比,%)、焙烧温度和铵盐用量(铵盐与分子筛质量比,%)对稀土利用率的影响。结果表明:NaY型分子筛交换过程的稀土饱和交换度、超笼中RE^(3+)的不稳定性,以及NH_(4)^(+)的反交换是造成分子筛交换过程稀土利用率低的主要原因;在稀土改性Y型分子筛(RE-Y)制备过程中,RE^(3+)与NaY分子筛的Na^(+)在100℃下的交换为不完全交换;当一交一焙中的稀土投料用量从3%提高至15%时,稀土利用率由95.9%降至84.6%,适当降低稀土投料量有利于提高其利用率;当一交中的铵盐用量为12%时,RE^(3+)完全被NH_(4)^(+)反交换出来,稀土利用率为0;当铵盐在一交、二交中用量分别为4%,15%时,稀土利用率分别为57.0%,96.7%,Na_(2)O质量分数分别为4.48%,1.58%,达到Y型分子筛Na_(2)O质量分数相应不大于4.5%,1.7%的指标要求;适当升高焙烧温度有利于提高超笼中的RE^(3+)向小笼的迁移率,增加RE^(3+)的稳定性,当一交一焙中的焙烧温度高于400℃时,稀土利用率约为90%。

The effects of rare earth feeding mass ratio to molecular sieve,calcination temperature and ammonium salt mass dosage on rare earth utilization rate of NaY zeolite in rare earth ion exchange process were investigated.The results showed that the saturation exchange degree of rare earth in Y zeolite exchange process,the instability of rare earth ions(RE^(3+)) in super cage and the reverse exchange of NH_(4)^(+) were the main reasons for the low utilization rate of rare earth in the exchange process of NaY zeolite.The exchange between RE^(3+) and Na^(+)of NaY was incomplete at 100℃during the preparation of rare earth modified Y molecular sieve(RE-Y).When the rare earth mass feeding ratio increased from 3%to 15%,the rare earth utilization rate reduced from 95.9%to 84.6%.For this above reason,reducing the rare earth feeding amount appropriately was conducive to improving the rare earth utilization rate.When the amount of ammonium salt in the first exchange was 12%,the RE^(3+) was completely exchanged by NH_(4)^(+),and the corresponding rare earth utilization rate was 0.When the amount of ammonium salt in the first and the second ion exchange was 4%and 15%respectively,the corresponding rare earth utilization rate was 57.0%and 96.7%.Meanwhile,the mass fraction of Na_(2)O was 4.48%and 1.58%,which met the index requirement of their relevantly matching the mass fraction of Na_(2)O within Y zeolite was not greater than 4.5%and 1.7%respectively.Increasing the calcination temperature would improve the mobility of RE^(3+) from the super cage to the small one and the stability of RE^(3+).When the calcination temperature of the first ion exchange was higher than 400℃,the utilization rate of rare earth was about 90%.