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Preparation of Inorganic–Organic Composites As Acid–Base Catalysts Using Hca2nb3−Xta Xo10 and Quaternary JCS-Japan Onium Salts

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Preparation of Inorganic–Organic Composites As Acid–Base Catalysts Using Hca2nb3−Xta Xo10 and Quaternary JCS-Japan Onium Salts Journal of the Ceramic Society of Japan 128 [1] 51-55 2020 -Japan DOI http://doi.org/10.2109/jcersj2.19119 JCS NOTE Preparation of inorganic­organic composites as acid­base catalysts using HCa2Nb3¹xTaxO10 and quaternary onium salts Masataka OGASAWARA1,³, Takuto BAN2, Kanji SAITO1,3 and Sumio KATO1 1 Graduate School of Engineering Science, Department of Materials Science, Akita University, 1–1 Tegata gakuen-machi, Akita 010–8502, Japan 2 Graduate School of Engineering and Resource Science, Department of Applied Chemistry, Akita University, 1–1 Tegatagakuen-machi, Akita 010–8502, Japan 3 Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2–8–26 Nishiwaseda, Shinjuku-ku, Tokyo 169–0054, Japan Inorganic­organic composites have been prepared using Dion­Jacobson-type layered perovskite compounds as base catalysts. Dodecyltributylphosphonium bromide (C12TBPBr), dodecyltriphenylphosphonium bromide (C12TPPBr), or dodecyltrimethylammonium chloride (C12TMACl) were used as the organic species of the + + + inorganic­organic composite. It was suggested that C12TBP ,C12TPP ,orC12TMA were intercalated by ion- + exchange with interlayer H of HCa2Nb3O10. The acid­base reaction was evaluated by consecutive deacetalization­Knoevenagel reactions. The product of the second-step reaction of the inorganic­organic composite catalysts was obtained, which suggested that the composites were acid­base bifunctional materials. For composites prepared using HCa2Nb3¹xTaxO10 (x = 1, 2, and 3) as inorganic species, the base catalytic activity decreased with decreasing fraction of organic species. Therefore, the hydrophobicity of the layered compounds affected the catalytic activity of the composite. Various catalysts should be prepared using reported layered perovskite-type compounds having various compositions. ©2020 The Ceramic Society of Japan. All rights reserved. Key-words : Layered-perovskite, Inorganic–organic composite, Quaternary phosphonium cation, Intercalation, Acid–base catalyst [Received June 4, 2019; Accepted November 4, 2019] Environment-friendly catalysts are currently attracting are known as organic cationic species similar to quaternary attention in the fields of green and sustainable chemistry. alkylammonium cations, we attempted to prepare compo- The coexistence of multiple functions, such as acid and sites consisting of quaternary alkylphosphonium cations base catalytic properties, has been studied to guide the and a layered compound, and evaluated their base catalytic development of multistep cascade reactions that are activities. Furthermore, the addition of basic properties to advantageous for minimizing energy usage and chemical solid acid materials should produce acid­base bifunctional waste.1)­4) To impart base catalytic activity to inorganic materials. We would like to propose this approach as a compounds, grafting of basic organic functional groups is prospective method for functionalization of cationic- often used. For example, acidic montmorillonite,5) zeolite,6) exchangeable layered compounds. or mesoporous materials grafted with alkylamines behave Dion­Jacobson-type layered perovskite compounds 7),8) as solid base catalysts. In addition, it has been reported with the general formula AB[An¹1BnO3n+1] (A, AB: alkali, that precursors to zeolite and mesoporous silica with qua- alkali earth; B: Ti, Nb, Ta, or Fe) have been reported.15)­17) ternary ammonium cations act as solid base catalysts.9)­14) These compounds have attracted interest due to their com- In these materials, it is thought that the base sites are locat- positional variability and diverse chemical properties. In ed at the siloxy anion (Si­O¹) on the inorganic surface, particular, compounds with AB = H are known as solid near the quaternary ammonium cations. These results indi- Brønsted acids. In addition, inorganic­organic composites cate that a base site is formed by the interaction between can be prepared by the intercalation of organic spe- metal oxides and organic cations. Therefore, it is interesting cies.18)­24) We previously synthesized composites based on to investigate the base catalytic activity for composites Dion­Jacobson-type HLaNb2O7 and HCa2Nb3O10 com- containing organic cations. As alkylphosphonium cations pounds with the addition of alkyltrimethylammonium 23) (CnTMA) and alkylpyridinium (CnPy) cations. How- ³ Corresponding author: M. Ogasawara; E-mail: oga@gipc. ever, HCa2Nb3O10-based composites with other quaternary akita-u.ac.jp cations have not yet been reported, and the basic prop- ©2020 The Ceramic Society of Japan 51 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by-nd/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Ogasawara et al.: Preparation of inorganic–organic composites as acid–base catalysts using HCa2Nb3−xTa xO10 and quaternary JCS-Japan onium salts Scheme 1. Schematic of the consecutive deacetalization­Knoevenagel reactions. erties of composites containing CnTMA and CnPy cations C12TMACl aqueous solution in 1:1 molar ratio. The sus- have not yet been adequately studied. Therefore, in this pension was stirred at 303 K for 1 h. The obtained precip- study, we prepared inorganic­organic composites using itate was filtered and dried at 333 K. The prepared sam- HCa2Nb3¹xTaxO10 (x = 0, 1, 2, 3) as the inorganic species ples are henceforth referred to as HCa2Nb3O10-C12TBP, and CnTMA or alkylphosphonium ions as the organic HCa2Nb3O10-C12TPP, and HCa2Nb3¹xTaxO10-C12TMA. species. As described above, we synthesized HCa2Nb3O10- Phase identification of the prepared samples was per- CnTMA composites for n = 12 to 18. In this study, a formed by powder X-ray diffraction (XRD) using a Rigaku quaternary onium ion with a dodecyl (C12) group was Ultima IV X-ray diffractometer (Cu-K¡ radiation, 40 kV, selected. Results of composite including C12-group onium 40 mA). The acid amount of the samples was measured by cation would be useful to evaluate various properties of titration with an aqueous ammonium solution. The organic composites including C12­C18-group onium cations. Base species content was calculated from the carbon content site formation by the interaction between a metal oxide determined by CHN elemental analysis using an Exeter and a quaternary onium cation was reported only for com- Analytical Inc. CE-440M element analyzer. posites including quaternary ammonium cations. In order The acid­base reaction was carried out by liquid-phase to investigate the effect of the cationic functional group, consecutive deacetalization­Knoevenagel reactions quaternary phosphonium-containing composites were pre- (Scheme 1). Benzaldehyde dimethylacetal (BDMA; pared using dodecyltributyl and dodecyltriphenyl phos- 1 mmol), H2O (1 mmol), ethyl cyanoacetate (1 mmol), phonium cations, which are stable and readily available catalyst (30 mg), and acetonitrile solvent (2 mL) were as high-purity reagents. The catalytic behavior and acid­ added to a glass reactor, and stirred with a magnetic stirrer base properties of these composites were evaluated for at 343 K for 3 h. The sole Knoevenagel reaction was Knoevenagel reaction and consecutive deacetalization­ carried out using the following procedure. Benzaldehyde Knoevenagel reactions. (1 mmol), ethyl cyanoacetate (1 mmol), catalyst (50 mg), Layered-perovskite-type HCa2Nb3¹xTaxO10 (x = 0, 1, and dimethyl sulfoxide solvent (3 mL) were added to a 2, 3) compounds were used as the inorganic species of glass reactor and stirred at 303 K. The reacted solutions the inorganic­organic composites, and were obtained by were analyzed by high-performance liquid chromatogra- ion-exchange using KCa2Nb3O10 or RbCa2Nb3¹xTaxO10 phy with ultraviolet and refractive index detectors. 24) (x = 1, 2, 3). KCa2Nb3O10 and RbCa2Nb3¹xTaxO10 Figure 1 shows the XRD patterns of the HCa2Nb3O10, 17) (x = 1, 2, 3) were synthesized via solid-state reactions HCa2Nb3O10-C12TBP, HCa2Nb3O10-C12TPP, and of K2CO3,Rb2CO3,La2O3, CaCO3,Nb2O5, and Ta2O5. The HCa2Nb3O10-C12TMA. The (001) peaks of HCa2Nb3O10- molar ratio of the starting materials was alkaline carbonate C12TBP, HCa2Nb3O10-C12TPP, and HCa2Nb3O10-C12TMA (K2CO3 or Rb2CO3):CaCO3:Nb2O5:Ta2O5 = 1.5:4:3 ¹ x:x, were observed at lower angles than that of HCa2Nb3O10. and they were mixed in ethanol using a mortar and pestle. These results indicated that expansion of the interlayer KCa2Nb3O10 was obtained by heating the precursor mix- space occurred due to intercalation of C12TBP, C12TPP, ture at 1523 K for 18 h in air, while the RbCa2Nb3¹xTaxO10 or C12TMA cations. The d-spacings determined from the (x = 1, 2, 3) series of compounds were obtained by heating (001) peaks of HCa2Nb3O10-C12TBP, HCa2Nb3O10- the corresponding precursors at 1023 K for 12 h, and then C12TPP, and HCa2Nb3O10-C12TMA samples were 2.90, at 1423 K for further 36 h in air. The K- and Rb-type 2.98, and 3.02 nm, respectively. A previous study of the samples were dispersed in 6 mol/L HCl aqueous solution HCa2Nb3O10­C12Py composite with the same alkyl chain and stirred at 333­343 K for protonation by ion exchange. reported a d-spacing of 3.1 nm, where the organic species 23) Dodecyltributylphosphonium bromide (C12TBPBr; Tokyo formed a monolayer with tilting in the interlayer. The Chemical Industry Co., Ltd.; 98.0%), dodecyltriphenyl- d-spacings of the C12TBP-, C12TPP-, and C12TMA- phosphonium bromide (C12TPPBr; Wako Pure Chemical composites
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