Tanwongwan Worapak, Chollacoop Nuwong, Faungnawakij Kajornsak, Assabumrungrat Suttichai, Nakhanivej Puritut, Eiad-Ua Apiluck
College of Materials Innovation and Technology, King Mongkut's Institute of Technology Ladkrabang (KMITL), Chalongkrung Rd., Ladkrabang, Bangkok, 10520, Thailand.
National Energy Technology Center (ENTEC), National Science and Technology Development Agency (NSTDA), Phahonyothin Rd. Khlong Luang, Pathum Thani, 12120, Thailand.
Heliyon. 2023 Jul 28;9(8):e18772. doi: 10.1016/j.heliyon.2023.e18772. eCollection 2023 Aug.
Zeolite has become a promising material that can potentially play a pivotal role in resolving environmental crises. Among zeolite families, MCM-22 zeolite shows outstanding intrinsic properties associated with the topology and porous structure, offering ion-exchange advantages for catalytic activity processes. The synthesis of MCM-22 zeolite becomes challenging when concerning the cost and catalytic performance. To overcome this bottleneck, we demonstrate a sustainable route of a hydrothermal process using natural resources as starting materials. Rice husk from agricultural waste was used as a silica source while natural clays (kaolin and bentonite) were applied as alumina sources. The products from natural sources were compared with the use of commercial starting materials, e.g., NaAlO (for alumina) and NaSiO and TEOS (for silica), in points of crystal, compositional, and morphological views. We showed that the high purity of MCM-22 zeolite can be obtained from rice husk silica (RHS) and aluminosilicate gel (ASG) extracted from kaolin, while the use of ASG extracted from bentonite tended to be unsuitable to generate the zeolite formation. We also studied the effects of reaction time and the ratio of RHS/ASG on the crystallinity and surface area of MCM-22. The architecture and acidity of an optimal product were explored by Nuclear magnetic resonance spectroscopy and Temperature-programmed desorption of ammonia, demonstrating the success of achieving well acidity.
沸石已成为一种有前景的材料，有可能在解决环境危机中发挥关键作用。在沸石家族中，MCM - 22沸石展现出与拓扑结构和多孔结构相关的出色固有特性，为催化活性过程提供离子交换优势。当涉及成本和催化性能时，MCM - 22沸石的合成变得具有挑战性。为克服这一瓶颈，我们展示了一种以自然资源为起始原料的水热法可持续路线。农业废弃物稻壳被用作硅源，而天然粘土（高岭土和膨润土）被用作铝源。从晶体、组成和形态角度，将天然源产物与使用商业起始原料（例如，用于氧化铝的偏铝酸钠和用于硅的硅酸钠及正硅酸乙酯）的产物进行了比较。我们表明，从稻壳二氧化硅（RHS）和从高岭土提取的硅铝酸盐凝胶（ASG）可获得高纯度的MCM - 22沸石，而使用从膨润土提取的ASG往往不适于生成沸石结构。我们还研究了反应时间和RHS/ASG比例对MCM - 22结晶度和表面积的影响。通过核磁共振光谱和氨程序升温脱附探索了最佳产物的结构和酸度，证明成功实现了良好的酸度。
