This study delves into the acid modification of natural zeolite clinoptilolite, focusing on the identification of acid site types and their catalytic activity in the Brønsted acid‐catalyzed acetalization of benzaldehyde with 1,3‐butanediol. Following calcination, the samples underwent acidification via ammonium‐ion exchange, resulting in approximately 45% of the clinoptilolite cations being exchanged with ammonium ions. The investigation evaluates the structural, morphological, and textural alterations induced by this modification using XRD, FTIR, and nitrogen adsorption‐desorption measurements. Ammonia‐temperature‐programmed desorption (NH3‐TPD) analysis confirms the presence of medium to strong acidic protons, highlighting the acidity of the modified samples. Employing 27Al and 29Si magic‐angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy elucidated changes in the state and coordination of aluminum post‐sample activation. Specifically, the 27Al MAS NMR spectra indicate a partial dealumination, evidenced by the emergence of 5 and 6‐fold coordinated aluminum. Moreover, 29Si MAS NMR measurements tracked variations in the Si/Al ratio. The study probes the nature of these sites, their influence on catalytic activity, and the synergistic interplay between Brønsted acid sites and 5‐fold coordinated aluminum. The results showcase that the prepared acidic natural clinoptilolite catalysts augment acidity and porosity, fostering promising implications for catalytic applications.

中文翻译：

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天然沸石斜发沸石的温度诱导改性：对酸度和催化缩醛化的影响

本研究深入研究了天然沸石斜发沸石的酸改性，重点是酸位点类型的识别及其在布朗斯台德酸催化苯甲醛与 1,3-丁二醇缩醛化反应中的催化活性。煅烧后，样品通过铵离子交换进行酸化，导致大约 45% 的斜发沸石阳离子与铵离子交换。该研究使用 XRD、FTIR 和氮气吸附-解吸测量评估了这种修饰引起的结构、形态和结构变化。氨程序升温解吸 (NH3-TPD) 分析证实了中强酸质子的存在，突出了改性样品的酸性。采用 27Al 和 29Si 魔角旋转核磁共振 (MAS NMR) 光谱阐明了样品激活后铝的状态和配位变化。具体来说，27Al MAS NMR 谱表明部分脱铝，5 和 6 配位铝的出现证明了这一点。此外，29Si MAS NMR 测量跟踪了 Si/Al 比率的变化。该研究探讨了这些位点的性质、它们对催化活性的影响，以及布朗斯台德酸位点和五重配位铝之间的协​​同相互作用。结果表明，所制备的酸性天然斜发沸石催化剂增强了酸度和孔隙率，为催化应用带来了有希望的影响。