稀土改性HZSM-5分子筛催化裂解混合C4烃制低碳烯烃性能的研究

Effect of Rare Earth-modified HZSM-5 Zeolites on the Catalytic Cracking of Mixed C4 Hydrocarbons to Produce Light Olefins

用浸渍法制备了稀土改性HZSM-5分子筛催化剂（简称RE/HZSM-5）,研究了RE/HZSM-5对混合C4烃（包括C4烷烃和C4烯烃）裂解活性及低碳烯烃收率的影响。结果表明,RE改性后HZSM-5分子筛催化剂的裂解活性明显增加,轻稀土改性HZSM-5分子筛比重稀土改性的表现出更好的增产低碳烯烃裂解性能。在0.1MPa,重时空速（WHSV）=1.2×104mL/h.g^-1条件下,轻稀土La、Pr、Nd、Sm、Gd改性HZSM-5分子筛催化剂上混合C4烃催化裂解产物中乙烯和丙烯总收率在625℃时达到最高,分别为54.66%、54.32%、53.32%、54.15%和54.06%,比相同条件下未改性的HZSM-5高3%~4%。重稀土中只有Yb/HZSM-5表现出较好的裂解活性,裂解产物中乙烯和丙烯总收率在600℃时达到最高,为54.80%。用红外光谱（FT-IR）,氨程序升温脱附（NH3-TPD）和吡啶吸附红外光谱法（Py-IR）法对RE/HZSM-5分子筛进行了表征,结果表明催化剂的总酸量、B酸与L酸的比值与催化活性之间存在密切关系。

Rare earth-modified HZSM-5 catalysts（RE/HZSM-5）were prepared by impregnation method.The catalytic performances of the RE/HZSM-5 catalysts for the catalytic cracking of the mixed C4 hydrocarbons to produce light olefins were investigated.The results indicated that the addition of rare earth metal on HZSM-5 catalyst greatly enhanced the cracking activity.Light rare earth-modified HZSM-5 catalysts showed better performance on the production of light olefins than those of heavy rare earth.Under the conditions of 0.1MPa,1.2×104 mL/h·g^-1,the yields of ethylene and propylene from the cracking of mixed C4 hydrocarbons at 625℃ on light rare earth-modified HZSM-5 including La/HZSM-5,Pr/HZSM-5,Nd/HZSM-5,Sm/HZSM-5 and Gd/HZSM-5 zeolites reached the maximum of 54.66%,54.32%,53.32%,54.15% and 54.06%,respectively,which is higher than that of unmodified HZSM-5 zeolite by 3%～4%.Among the heavy rare earth-modified HZSM-5 catalysts,only Yb/HZSM5 showed better cracking activity,with the maximum yield of light olefins at 54.80%.In addition,the catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD and IR spectroscopy of adsorbed pyridine,and the results showed that the total acidic amount and B/L ratio had the relation with the catalytic activity.