Insight into the correlation between the effective adsorption sites and adsorption desulfurization performance of CuNaY zeolite
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摘要: 以液相离子交换法制备了一系列不同Cu负载量的CuNaY分子筛；采用XRD及N2吸附-脱附表征分子筛的微观结构和织构性质，采用动态吸附法考察其对噻吩模拟油的吸附脱硫性能，结合NH3-TPD和Py-FTIR方法对CuNaY分子筛的酸量和有效Cu+物种进行定量分析，研究了CuNaY分子筛的表面酸性和铜物种形态结构对其吸附脱硫性能的影响机制。结果表明，通过改变铜负载量可有效调控改性Y分子筛的表面酸性以及铜物种化学形态；适量铜物种的引入可以最大限度的形成有效吸附位，从而获得最优吸附脱硫性能，而过量的Cu物种会在Y分子筛笼内形成多核铜物种结构，导致有效吸附位点的减少，影响其对噻吩的吸附能力。Abstract: A series of CuNaY zeolites with different Cu loadings were prepared from NaY by liquid-phase ion exchange (LPIE) method. The microstructure and textural properties of CuNaY zeolites were characterized by XRD and N2 sorption and their adsorption desulfurization performance were evaluated with a model oil containing thiophene by the dynamic adsorption method. Combined with the Py-FTIR and NH3-TPD methods, the amounts of surface acid sites and effective Cu+ species were determined quantitatively and a correlation between the effective adsorption sites and adsorption desulfurization performance of CuNaY zeolite towards thiophene was then established. The results revealed that the surface acidity and the active copper species in Y zeolite can be regulated effectively by controlling the copper loading; an adsorbent provided with abundant effective adsorption sites and excellent adsorption desulfurization performance can be obtained by loading appropriate amount of copper. On the contrary, an excessively high copper loading may promote the formation of polymeric copper species in the cavity of Y zeolite, which leads to a decrease in the number of effective adsorption sites as well as a decrease in the adsorption capacity of CuNaY zeolite towards thiophene.
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Key words:
- CuNaY zeolite /
- adsorption site /
- copper loading /
- adsorption desulfurization
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图 1 不同铜负载量Cu(Ⅱ)NaY分子筛的XRD谱图
Figure 1 XRD patterns of Cu(Ⅱ)NaY zeolites with different copper loadings
图 2 不同铜负载量Cu(Ⅰ)NaY分子筛的N2吸附-脱附等温线
Figure 2 Nitrogen adsorption-desorption isotherms of Cu(Ⅰ)NaY zeolites with different copper loadings
图 3 噻吩模拟油在不同铜负载量Cu(Ⅰ)NaY分子筛上的动态吸附穿透曲线和穿透、饱和硫含量
Figure 3 Breakthrough curves (a) and dsorption capacity towards thiophene of Cu(Ⅰ)NaY zeolites (b) with different copper loadings
图 4 铜改性Y分子筛单核铜聚合成多核铜形成过程
Figure 4 Polymerization process from mono-copper species to di-copper species in the copper modified Y zeolite
图 5 铜改性Y分子筛自还原机理
Figure 5 Self-reduction of copper modified Y zeolite
(a): mono-copper species; (b): di-copper species
图 6 不同铜负载量Cu(Ⅰ)NaY分子筛的NH3-TPD谱图; NH3-TPD谱图的高斯拟合曲线
Figure 6 NH3-TPD profiles (a) and their Gaussian fitting curves (b) of Cu(Ⅰ)NaY zeolites with different copper loadings
a: NaY; b: Cu(Ⅰ)NaY-1; c: Cu(Ⅰ)NaY-2; d: Cu(Ⅰ)NaY-3
图 7 Cu(Ⅰ)NaY分子筛中总的铜物种和有效铜物种含量变化
Figure 7 Total and effective copper species of the Cu(Ⅰ)NaY zeolites alone with the copper loading
表 1 不同铜负载量Cu(Ⅱ)NaY分子筛的结构与组成
Table 1 Structure and composition of Cu(Ⅱ)NaY zeolites with different copper loadings
Sample w(Na2O)/% w(CuO)/% Nactual Lattice parameter d/nm Relative crystallinity/% NaY 12.73 0 0.0 2.464 100 CuNa(Ⅱ)Y-1 11.40 1.18 3.4 2.463 96.2 CuNa(Ⅱ)Y-2 5.31 9.39 15.2 2.462 83.1 CuNa(Ⅱ)Y-3 4.02 10.89 17.7 2.460 70.6 note: Nactual: Cu2+ number per unit cell 
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表 2 不同铜负载量Cu(Ⅰ)NaY分子筛的孔结构参数
Table 2 Textural properties of Cu(Ⅰ)NaY zeolites with different copper loadings
Sample Surface area
A/(m2·g-1)Mesoporous
surface area A/(m2·g-1 )Micropore volume
v/(cm3·g-1)Mesoporous volume
v/(cm3·g-1)NaY 585.3 38.2 0.28 0.029 Cu(Ⅰ)NaY-1 602.7 86.8 0.31 0.074 Cu(Ⅰ)NaY-2 601.0 65.0 0.28 0.060 Cu(Ⅰ)NaY-3 597.8 65.1 0.28 0.055
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表 3 Cu(Ⅰ)NaY分子筛的酸量和具有络合能力Cu(Ⅰ)物种的含量
Table 3 Distribution of acid sites and complex Cu(Ⅰ) species in the Cu(Ⅰ)NaY zeolites
Sample Acid strength distribution /(μmol·g-1) μt/μ0 Mediate strong acid
amounts /(μmol·g-1)Neffective 100-250 ℃ 250-500 ℃ NaY 126.0(100%) 0 0 0 0 Cu(Ⅰ)NaY-1 213.9(52.6%) 193.1(47.4%) 1 64.37 3.4 Cu(Ⅰ)NaY-2 58.3(7%) 733.6 (93%) 4.01 237.77 13.58 Cu(Ⅰ)NaY-3 23.6 (4%) 626.9(96%) 3.84 189.86 10.02 note: μ0 is the mediate strong acid amounts of Cu(Ⅰ)NaY-1; μt is the mediate strong acid amounts of NaY, Cu(Ⅰ)NaY-2 and Cu(Ⅰ)NaY-3; Neffective represents the number of Cu+ with complexing capability per unit cell
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