SAPO-34分子筛上丁烯催化裂解制乙烯和丙烯

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

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。

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.