NiW/SAPO-11催化剂对煤焦油加氢尾油模型化合物二十烷加氢异构性能的影响

Effect of NiW/SAPO-11 catalyst on hydroisomerization performance of model compound eicosane for tail oil hydrogenation of coal tar

以SAPO-11分子筛为载体,采用机械化学法制备Ni系催化剂,引入W调节其电子结构、晶粒尺寸与形态分布以及催化剂的孔结构、酸性与酸量等,基于对XRD、TEM、BET、NH3-TPD、吡啶吸附红外等结果的深入分析,探究催化剂NiW配比对催化剂性质和煤焦油加氢尾油模型化合物正二十烷(n-C_(20))加氢异构性能的影响规律。结果表明,Ni/SAPO-11负载W后,比表面积不同程度增加,W质量分数为0.5%时比表面积达到最大值149 m^(2)/g;Ni的平均粒径减小,W质量分数为1%时降至最小值4.43 nm,比Ni/SAPO-11减小36%,且Ni^(0)的含量和表面酸量均最高。此外,W促进了Ni的还原,使得还原峰温向低温方向移动。XPS分析表明,随着W含量的增加,Ni^(0)的结合能降低,W5+的结合能升高。二十烷(n-C_(20))的加氢异构产物分布显示,3Ni1W/SAPO-11作用下n-C_(20)的转化率和异二十烷(i-C_(20))的收率均最高,分别为88.23%和75.72%,且以单支链异二十烷(Mono-i-C_(20))为主,收率达71.65%。在线取样结果显示,n-C_(20)在金属位点与酸功能的双重作用下先生成单支链异构体,随着反应的进行向多支链异构体转化,不稳定的多支链异构体会进一步裂解成小分子烷烃。

Ni-based catalysts were prepared by mechanochemical method with SAPO-11 zeolite as the carrier,and W was introduced to adjust the electronic structure,grain size and morphology of Ni particle,as well as pore structure,acidity,and acid amount of the catalyst.The effect of NiW ratios on catalyst properties and the hydro-isomerization properties of n-eicosane(n-C_(20)),which is a model compound for coal tar hydrogenation tail oil,was explored by XRD,TEM,BET,NH3-TPD and Py-FTIR.The results show that the specific surface area of Ni/SAPO-11 increases with the addition of W,and reaches the maximum value of 149 m^(2)/g at the W addition of 0.5%.The average particle size of Ni decreases with the addition of W,and reaches to the minimum value of 4.43 nm at the W addition of 1%,which is 36%less than that of Ni/SAPO-11.At this time,the content of Ni^(0)and the amount of surface acid are the highest.In addition,W promotes the reduction of Ni,causing the reduction peak temperature to move toward lower temperature.XPS results show that with the increase of W content,the binding energy of Ni^(0)decreases while that of W5+increases.The isomers distribution of eicosane(n-C_(20))shows that the conversion of n-C_(20)and the yield of i-C_(20)are the highest in the presence of 3Ni1W/SAPO-11,which are 88.23%and 75.72%,respectively.It is mainly the mono-i-C_(20)with a yield of 71.65%.The on-line sampling results show that n-C_(20)generates the mono-branched isomer under the action of metal site and acid function.With the reaction,the mono-branched isomer is transformed into the multi-branched isomer,and the unstable multi-branched isomer is cracked into small molecule alkanes.