Kanto Loam as a Starting Material for the Synthesis of ZSM-5 Zeolite and Catalytic Properties of the Product

TAKASAKI Yuukei, ISHIZAWA Noboru, YOSHIDA Akira, SHIBUYA Takemi, TOHGOH Hiroshi, ENDOH Atsushi

doi:10.1246/nikkashi.1989.324

A volcanic ash layer, referred to as Kanto loam, is widely distributed in Kanto area of Japan, and is composed of silica and alumina. In the present study, we present how Kanto loam influences the synthesis of ZSM-5 zeolite when Kanto loam is used as one of the raw materials. The synthesis of zeolite was hydrothermally carried out by shaking it in an autoclave (SUS 316) of 24 ml at 448 K for 24 h. Starting composition was 5 Na₂0-35 SiO₂-Al₂0₃-779 H₂0. Amounts of Kanto loam (dry), silicon dioxide, sodium hydroxide, and water used were 0.3285, 2.4141, 0.4435, and 15.0000g, respectively. The amount of “as made” product synthesized and the weight percentage of them to solid in the starting composition were 1.7221g and 54.1%, respectively. The product was identified as ZSM-5 zeolite on the bases of XRD (Fig.1 c) and SEM (Fig.2 c). However a product synthesized without addition of any Kanto loam was not ZSM-5 (Figs. 1b, 2b). It was found from the synthesis using residual Kanto loam extracted humic substances that this success was due to humic substances of Kanto loam. It was found that ZSM-5 could selectively and effectively be synthesized under reaction conditions of at 448K, for 24h, and water content of 95%. Typical results in these conditions are summerized in the phase diagram (Fig.7) that shows relationships between the starting composition and the product. The diagram shows that whether the metastable phase or ZSM-5 is selectively synthesized or not depends largely on the ratio of Na₂0/SiO₂.<BR>The catalytic properties of ZSM-5 synthesized from Kanto loam, referred to as L-ZSM-5, were compared with those of ZSM-5 prepared from tetrapropylammonium iodide, referred to as TPA-ZSM-5. The properties were examined with respect to the acidity and acid strengths measured by temperature-programmed desorption of NH₃, and alkylation of toluene with methanol. The acidity and acid strengths of L-NaZSM-5 were larger than those of TPA-NaZSM-5, but those of LHZSM-5 showed almost the same level as those of TPA-HZSM-5. Small differende in alkylation over both HZSM-5 was shown, but L-NaZSM-5 could produce only p-xylene (Table 3). The difference was ascribed to impurities in LZSM-5 (Table 4, Fig.9).

Kanto Loam as a Starting Material for the Synthesis of ZSM-5 Zeolite and Catalytic Properties of the Product

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