Selective dealumination of large pore Zeolite Beta for effective Brønsted acid site utilization

• Published in: Journal of catalysis 2024-12, Vol.440, p.115796, Article 115796
• Main Authors: Samanta, Pranit, Ussama, Mohd, Shrivastav, Gourav, Ali Haider, M., Pant, K.K., Kumar, Manjesh
• Format: Article
• Language: English
• Subjects: Alkylation; aluminum; catalytic activity; Dealumination; Dicarboxylic acids; geometry; NMR; phenol; T sites; Zeolite Beta; zeolites
• ISSN: 0021-9517
• DOI: 10.1016/j.jcat.2024.115796

[Display omitted] •Aqueous dicarboxylic acids were used as dealuminating agents for Zeolite Beta.•Al removal depends on acid size, strength, and stability of the acid-Al complex.•Oxalic acid removed Al from T3, T9 and extra-framework positions completely.•Malonic acid partially removed Al from all three T sites (T2, T3, and T9).•Alkylation productivity was highest in Malonic acid-treated Zeolite Beta. Tuning of Al sites through spatial and geometric distribution is a novel pursuit for deterministic catalytic performance. To design an efficient Zeolite Beta for phenol alkylation with optimal physicochemical attributes, we conducted a systematic study with a series of dicarboxylic acids to selectively extract the framework and/or non-framework Aluminium. Herein, the post-synthetic treatment resulted in dealuminated catalysts of silicon-to-aluminum ratio ∼15–53. Extensive Al and Si NMR studies glean the selective extraction of aluminum from the zeolitic framework along with recomposition in T sites. The potency study alludes to the convoluted role of pH, chelating ability, and/or site accessibility for complexation. The differentiated Al extraction results in the emergence of unique super-strong acid sites. The novelty of our approach was established using phenol alkylation with cyclohexanol wherein we observed the highest conversion and desired CC alkylated product formation for the malonic acid-treated Zeolite Beta.