Synthesis of Micro-Crystalline Zeolite Containing Calcium by Addition of Boric Acid

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Other Title
  • ホウ酸添加によるカルシウム含有微結晶ゼオライトの合成

Description

ZSM-5 type zeolites containing alkaline earth metal, especially calcium, showed the best catalyst performance for methanol conversion to light olefins at high temperatures above 500°C. In order to extend the catalyst life, the control of the zeolite crystal size was studied. First we investigated the effect of the amounts of aluminium and calcium in the synthesis mixture on the zeolite crystal size. It was found that the crystal size became small with an increase in these amounts. However, we could not obtain the zeolites with Ca/Al2 ratio of more than 3, which were effective for methanol conversion to light olefins under high temperatures. Then, we tried to control the crystal size of the zeolites containing calcium by adding boric acid. It was found that the zeolite crystal size became small with the amount of boric acid and in the case of SiO2/B2O8 ratio of 20 in the synthesis mixture, the crystal size of the zeolite with Ca/Al2 ratio of 3.29 was below 1 μm (Fig.2, Table 1). Fig.4 shows the results of methanol conversion over the micro-crystalline zeolite with high Ca/Al2 ratio under the reaction conditions of LHSV=.4h-1 and 600°C. The initial activity of the zeolite synthesized in the presence of boric acid was similar to that of the zeolite synthesized in its absence. The catalyst life, the time with a selectivity for ethylene and propylene of >50%, of the zeolite prepared in the presence of boric acid was approximately 30 h, which was 1.6 times that of the zeolite prepared without the acid.

Journal

  • NIPPON KAGAKU KAISHI

    NIPPON KAGAKU KAISHI 1990 (6), 636-641, 1990-06-10

    The Chemical Society of Japan

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