Mechanism of effects of surface acidity on performance of adsorption desulfurization of NiY zeolites
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摘要: 采用原位红外光谱技术，以噻吩、环己烯和苯为模型探针分子，分别考察单一烃分子在NiY分子筛上的吸附与反应行为以及噻吩与烯烃、芳烃间的竞争吸附和催化反应行为。单一探针分子吸附研究发现，NiY分子筛中与Ni物种相关的Lewis（L）酸位是噻吩的选择性吸附活性位；噻吩和环己烯在NiY分子筛中Brönsted（B）酸位上发生的质子化和低聚反应明显弱于HY分子筛。双探针分子竞争吸附研究发现，环己烯二聚体在NiY中强B酸位上的强化学吸附与噻吩存在显著的竞争吸附行为。另外，苯和噻吩在NiY上的竞争吸附现象在373 K时明显减弱。由此，在选择性吸附脱硫过程中，减少吸附剂表面B酸中心可降低烯烃对噻吩的竞争吸附，另外适当提高吸附体系的温度可以有效避免芳烃对噻吩的竞争吸附。Abstract: The adsorption behaviors of thiophene, cyclohexene and benzene, and competitive adsorption of thiophene & cyclohexene, and thiophene & benzene over NiY zeolites were studied by in situ Py-FTIR spectroscopy method. The results of single probe molecular adsorption indicate that the Lewis (L) acid sites according to Ni species are the major active centers for the thiophene adsorption, more over the Brönsted (B) acid sites of the NiY and HY are the catalytic active centers of the protonation and oligomerization of thiophene and cyclohexene, while the reaction intensity on NiY is significantly weaker than that on HY zeolite. The competitive adsorption results show that the strongly adsorbed dimeric cyclohexene on B acidic sites in NiY zeolite plays a significant competitive adsorption to thiophene adsorption behavior. The effective solutions to solve the competitive adsorption from olefins and aromatics to thiophene are to reduce the surface B acid centers of the adsorbent and to increase temperature of adsorption system.
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Key words:
- in situ Py-FTIR /
- NiY zeolite /
- surface acidity /
- adsorption desulfurization /
- competitive adsorption
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图 1 NiY (a)、HY (b) 和NaY (c) 分子筛的Py-FTIR谱图
a: background; b: desorption at 423 K; c: desorption at 673 K
Figure 1 Py-FTIR spectra of the NiY (a), HY (b) and NaY (c) zeolites
图 2 噻吩在分子筛上吸附的原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY; d: thiophene
Figure 2 In situ Py-FTIR spectra of thiophene adsorbed on the zeolites
图 3 环己烯在分子筛上吸附原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY; d: cyclohexene
Figure 3 In situ Py-FTIR spectra of cyclohexene adsorbed on the zeolites
图 4 苯在分子筛上吸附的原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY; d: benzene
Figure 4 In situ Py-FTIR spectra of benzene adsorbed on the zeolites
图 5 在分子筛上吸附噻吩后再吸附环己烯的原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY
Figure 5 In situ Py-FTIR spectra of adsorbed thiophene and cyclohexene on the zeolites
图 6 在分子筛上吸附环己烯后再吸附噻吩的原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY
Figure 6 In situ Py-FTIR spectra of adsorbed cyclohexene and thiophene on the zeolites
图 7 在分子筛上吸附噻吩后再吸附苯的原位红外光谱谱图
(a): desorption at 295 K; (b): desorption at 373 K a: NiY; b: HY; c: NaY
Figure 7 In situ Py-FTIR spectra of adsorbed thiophene and benzene on the zeolites
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