The acidic properties of H-MeAlPO-5 (Me=Si, Ti, or Zr): A periodic density functional study

Influence of dopant substitution mechanism on catalytic properties within hierarchical architectures

“…In the case of the tetravalent dopants, a trend between bond angle and acid site strength in microporous Me AlPO-5 has been observed. The bond angles of the microporous catalyst increase in the following order Ti−O−Al = 119.4 • < Si−O−Al = 132.9 • , and the acidity of the framework follows the same trend [49]. It is therefore envisaged that the Ti and Si Brønsted acid sites will be found in the micropores of the HP catalyst; hence similar bond angles would be expected.…”

“…Microporous Co AlPO-5 is well documented containing Lewis acid and Brønsted acid centres [50][51][52]. The nature of bonding between divalent dopants and the neighbouring oxygens is considered to be more ionic in nature than M(IV)-O bonds; hence this explains the Lewis acidity of the Me (II) dopants [49,53]. HP Ti AlPO-5 also had minimal absorption in this region, whereas HP Si AlPO-5 had no evidence of Lewis acidity being present in the catalyst.…”

The effect of framework organic moieties on the acidity of zeolites: A DFT study

“…It should be mentioned here that the adsorption energy of NH 3 and DPE have been used carefully to measure and to predict the acidic properties of doped AlPO-34 [15], H-MOR [16], and doped AlPO-5 [17]. The choice of these molecular sieves was made on the basis of their potential applications to several industrial processes [13,18,19].…”

NO_x Molecule Adsorption in [Ag]-MAPO-5 (M=Si, Ti)Molecular Sieves

“…Cu鄄APO鄄34 和 Cu鄄SAPO鄄34(SAPO 表示以 PO 4 、 AlO 4 和 SiO 4 四面体交替构成的硅磷酸铝分子筛)在 NO 氧化生成 NO 2 反应中表现出优良的催化性能 [14] , 此 外, 在氧气或水存在下, 它在 N 2 O 分解反应中仍表 现出优良的催化活性. 研究 [15] 还发现 Cu鄄SAPO鄄34 骨架中硅的存在有利于分子筛结构热稳定和水热稳 定.Akolekar 等 [10] 采用傅里叶变换红外(FTIR)光谱研 究了银离子交换的 SAPO鄄34, 即 Ag鄄SAPO鄄34 对NO 和 CO 吸附, 结果表明, 在 Ag鄄SAPO鄄34 中形成各种 各样 NO/CO 复合物如 Ag(I)鄄NO、 Ag(I)鄄(NO) 2 、 Ag(I)鄄 (NO) 3 、 Ag(I)鄄CO 等.Elanany 等 [16] 采用密度泛函理论 (DFT)研究了 H鄄MeAlPO鄄5(Me=Si,Ti,Zr)的Br觟nsted 酸强度, 结果表明,H鄄ZrAlPO鄄5 的Br觟nsted 酸强度最 弱.…”

“…采用 DFT 中的GGA/ BLYP 方法和 DND 基组 [22][23] 对所有模型进行部分结 构优化, 对于金属离子采用赝势(ECP) [24] , 在此基础 上, 采用 GGA/BLYP 方法和 DNP 基组对所有模型 进行单点能计算. 同样的方法已被成功应用于研究 分子筛的酸强度 [18,25] 和吸附 [16,18] . 在进行计算时, 对所 [26], 在 结构优化基础上进行自然键轨道计算, 采用 Gaussian 03 软件中的模块 [27] , 以 DFT 方法在 B3LYP/6鄄31G ** 水平完成, 过渡金属采用 LANL2DZ 赝势基组.…”