The Surface-to-volume Ratio of the Synthesis Reactor Vessel Governing the Low Temperature Crystallization of ZSM-5

Abstract

Abstract. Zeolite ZSM-5 is one of the major catalysts in the petroleum and finechemical industries. The synthesis of zeolite ZSM-5 is usually carried out at a temperature above 100 °C using an immense amount of organic structuredirecting agents (OSDA). It is interesting to note that fine-tuning the initial gel mixture can be used to enhance the typical slow crystallization rate of ZSM-5. Herein, we report the effect of the surface-to-volume ratio of the reactor vessel on the crystallization of ZSM-5 at low temperature. The surface-to-volume ratio of the reactor vessel influences the heat-transfer during the synthesis, which further governs the crystallization of ZSM-5. It was found that the higher the surface-to-volume of the reactor, the more crystalline the resulting product. The products with the highest crystallinity exhibited a nearly spherical morphology composed of smaller ZSM-5 crystallites. This phenomenon allows the presence of inter-crystallite mesopores, which is an advantage for the catalytic reaction of bulky molecules. Keywords: low OSDA; low temperature; mesopores; surface-to-volume ratio; ZSM-5. IntroductionZeolite is a class of crystalline microporous (< 2 nm) aluminosilicate materials, arranged in a long-range order by TO4 (T = Si or Al) units. Zeolite is widely known for its application in particular fields such as sorption [1], catalysis [2,3] and ion-exchange [4]. Recently, its use has been extended to wider applications, including optical [5] and membrane technology [6]. Catalysis is the most known application of zeolite, for instance ZSM-5, especially for boosting the octane number in fluid catalytic cracking (FCC) units [7]. This is due to its peculiar structure comprising straight and zig-zag channels within sizes of around 5.5 Å and the presence of strong acid sites.

A Mechanistic Investigation of Sustainable Solvent-Free, Seed-Directed Synthesis of ZSM-5 Zeolites in the Absence of an Organic Structure-Directing Agent

“…There are several pronounced bands in the spectra. The bands at 1087, 937, 789, and 455 cm –1 are assigned to the asymmetric stretching Si–O–Si vibration, in-plane stretching vibration of Si–O within the silanol bond (Si–OH), symmetric stretching Si–O–T vibration, and bending Si–O–T vibration, respectively. , Moreover, the characteristic features of the crystalline ZSM-5 phase are indicated by the bands at 1217 and 548 cm –1 , which correspond to the asymmetric Si–O–Si stretching vibration associated with the five-membered ring and asymmetric Si–O–Si stretching vibration of the double five-membered rings within the pentasil unit of the MFI framework, respectively. , From 0 to 4 h, the characteristic bands of ZSM-5 were hardly observed since the amorphous precursors dominated the products. Furthermore, as the synthesis time progressed, both bands at 1217 and 548 cm –1 intensified, demonstrating the gradual formation of the MFI framework.…”

Advanced Ordered Nanoporous Materials

“…Many syntheses of commercial zeolites are carried out using silica, alumina, inorganic cation, hydroxide, water, and optionally OSDA reagents ingredients, through hydrothermal synthesis procedure at certain crystallization time and temperature, following the sequence of steps: (1) mixing of all of the ingredients to form a homogenous gel; (2) heating of the gel at a certain temperature (70 °C to 200 °C), in a Teflon-lined stainless steel autoclave; (3) evolution of the reaction mixture to form the designated framework; and (4) recovery of the zeolite crystals by filtration or centrifugation, washing, and drying. The role of each compound to make the gel composition, crystallization time, and the temperature has been widely reviewed (Hartmann et al 2016;Martinez and Corma 2013;Kadja et al 2015Kadja et al , 2017Mukaromah et al 2016). The role of OSDA is mainly explained in this chapter since it could be reworded as the decisive factor in synthesizing most zeolites.…”

Efektivitas Hydrilla verticillata dan Lemna minor sebagai Fitoremediator LAS pada Deterjen Limbah Domestik

“…Kenaikan suhu air disebabkan karena adanya bahan pencemar berupa LAS deterjen yang memengaruhi peningkatan metabolisme biota perairan yang akan membuat toksisitas bahan pencemar menjadi meningkat pula sehingga kadar oksigen dalam air akan menurun. Tanda air yang memiliki kandungan limbah yaitu suhu pada air yang akan lebih tinggi, hal tersebut dikarenakan air akan mengalami biodegradasi yang akan mempengaruhi kecepatan reaksi kimia (Mukarromah et al, 2016). Perubahan suhu yang terjadi pada media tanam akan berpangaruh terhadap proses metabolisme dan fotosintesis Hydrilla verticillata dan Lemna minor.…”