含尘焦油在改性白云石催化剂上的裂解特性

Cracking characteristics of dust-containing tar over modified dolomite catalyst

采用混捏法制备了一种添加助剂La的Ni-白云石催化剂。在常压固定床反应器中,以正十二烷、环己烷、甲苯和甲基萘的混合物作为焦油模型化合物,进行焦油裂解特性研究。考察了温度、空速、水料比等条件对气相产物产率的影响,对该催化剂进行了稳定性和再生性评价,在此基础上探讨了粉尘在催化剂表面沉积对催化剂性能影响的作用及机理。结果表明,该催化剂的最佳操作条件为反应温度800℃、空速300h-1、水料比5∶1、再生温度700℃、再生时间1h。XRD表征结果表明,改性白云石催化剂中形成了MgO-NiO固溶体和La(NiO3)晶相。粉尘中的不同组分对催化剂性能的影响不同,CaO有利于提高催化剂的活性,Fe2O3的沉积会形成NiFe2O4的新晶相,而SiO2会促进表面积炭,对催化活性的"抑制"作用明显。

A Ni-dolomite catalyst with promoter Lanthanum was prepared by kneading method. The catalyst was used for the cracking reaction of tar model compound containing N-dodecane,cyclohexane,toluene and methylnaphthalene in an atmospheric fixed reactor. The effects of temperature,space velocity and the ratio of water and ingredient on the yield of gas products were examined. The stability test and reaction-regeneration experiments were conducted. Moreover,cracking characteristics of dust-containing tar over the catalyst and dust deposition mechanism were investigated. The results showthat the optimum operating condition for the catalyst is reaction temperature 800 ℃,space velocity 300 h^-1,the ratio of water to ingredient 5 ∶ 1. The optimum regeneration condition is 700 ℃ and 1 h. XRD results showthat MgO-NiO solid solution and La（ NiO3）crystalline phase are converted in the modified dolomite catalyst. Different dust species depositing on the catalyst surface have different influences on the catalytic activity. CaO can improve the catalytic activity. The deposition of Fe2O3 can convert into a newcrystalline phase Ni Fe2O4. SiO2 plays a promoting role in carbon deposition,which can significantly inhibit the catalytic activity.