SAPO-34分子筛上丁烯催化裂解制乙烯和丙烯

以SAPO-34分子筛为催化剂,在固定流化床装置上研究了丁烯裂解的反应规律和结焦规律。实验结果表明,反应温度对丁烯裂解产物分布影响较大,丁烯转化率、乙烯和丙烯收率均随反应温度的升高而增加,乙烯和丙烯总选择性(双烯选择性)随反应温度的升高先增加后降低,适宜的反应温度为580～600℃;延长停留时间可提高丁烯转化率及乙烯和丙烯总收率(双烯收率),但停留时间过长会增加二次反应,降低乙烯、丙烯的选择性,尤其是丙烯;水蒸气对丁烯裂解有一定的促进作用,可使丙烯收率明显增加。与ZSM-5分子筛相比,SAPO-34分子筛的稳定性较差,但双烯选择性较高,在运行初期可获得与ZSM-5分子筛相当的双烯收率。SAPO-34分子筛催化丁烯裂解时,在运行初期及高温下生焦速率快,积碳显著影响SAPO-34分子筛的酸性。

Catalytic Cracking of Butene to Ethylene and Propylene over SAPO 34 Molecular Sieves

Cracking and coking of butene on SAPO 34 molecular sieve catalyst were investigated in a fixed fluidized bed reactor. High temperature(580-600 ℃) was required for butene cracking. Conversion of butene, and total yield of ethylene and propylene increased with temperature raising,but total selectivity to ethylene and propylene showed a maximum with temperature. Appropriate residence time was required for butene cracking in order to obtain high conversion and total yield of ethylene and propylene. Addition of a proper amount of water was preferable to butene cracking to obtain ethylene and propylene, especially the latter. In comparing with ZSM 5 catalyst, although total selectivity to ethylene and propylene on SAPO 34 catalyst was high, stability lowered. The total yield of ethylene and propylene on SAPO 34 catalyst at initial stage of butene cracking was comparable with that on ZSM 5 catalyst. The deposition of coke on SAPO 34 catalyst was observed to be fast at initial stage and high temperature. The acidity of SAPO 34 catalyst reduced obviously along with coke deposition.