Development of useful metal catalysts for hydrotreatment of diesel fuel to decrease particulate matters in diesel exhaust.

为了开发适用于柴油中芳烃加氢的金属催化剂，我们研究了在含硫化合物二甲基二硫化物存在下，负载型钯催化剂上萘的加氢反应。(1)研究了Pd/Al_2O_3、Pd/SiO_2、Pd/TiO_2、Pd/TiO_2-SiO_2和Pd/TiO_2-Al_2O_3催化剂在二甲二硫（DMDS）存在或不存在条件下的萘加氢反应。通过共浸渍法制备了Pd- pt /TiO_2-Al_2O_3、> Pd/TiO_2-SiO_2、> Pd/TiO_2、> Pd/Al_2O_3、> Pd/SiO_2(2)催化剂，并对二甲基二硫存在下的萘加氢反应进行了评价。Pd-Pt/TiO_2 bime - talic催化剂的TOF均高于Pt/TiO_2催化剂。含50mol% Pd的Pd- pt /TiO_2催化剂的TOF最高。Pd- pt /Al_2O_3的TOF在Pd含量为80mol%时最高。含有80mol% Pd的Pd-Pt/Al_2O_3的TOF分别是Pd/Al_2O_3和Pt/Al_2O_3的8倍和18倍。(3)与Pd/Al_2O_3相比，Pd/TiO_2在DMDS存在和不存在的情况下均表现出较高的TOF和耐硫性能。通过程序升温还原（H_2S-TPR）谱测定了Pd-S的结合强度。结果表明，硫化Pd/TiO_2中H_2S的解吸发生在553 K，而硫化Pd/Al_2O_3中H_2S的解吸需要更高的温度（773 K），表明Pd/TiO_2中的Pd- s键明显弱于Pd/Al_2O_3中的Pd- s键。因此，在Pd/TiO_2中，钯金属的清洁表面高度暴露为二甲基二硫化物存在下萘加氢的活性位点。

To develop useful metal catalysts for hydrogenation of aromatic hydrocarbons in diesel fuel, we have studied naphthalene hydrogenation over supported Pd catalysts in the presence of dimethyldisulfide as a sulfur compound.(1)Naphthalene hydrogenation over Pd/Al_2O_3, Pd/SiO_2, Pd/TiO_2, Pd/TiO_2-SiO_2, and Pd/TiO_2-Al_2O_3 cal alysts was studied in the presence or absence of dimethyldisulfide (DMDS). As a results, the order of TOP (turn over frequency) was Pd/TiO_2-Al_2O_3 > Pd/TiO_2-SiO_2 > Pd/TiO_2 > Pd/Al_2O_3 > Pd/SiO_2(2)Pd-Pt/TiO_2 and Pd-Pt/TiO_2 catalysts were prepared by a co-impregnation method and evaluated in the hydrogenation of naphthalene in the presence of dimethyldisulfide. All Pd-Pt/TiO_2 bime tallic catalysts showed the higher TOF than the Pt/TiO_2 catalyst. Pd-Pt/TiO_2 containing 50mol% Pd showed the highest TOF in the catalysts tested. Meanwhile The highest TOF of Pd-Pt/Al_2O_3 were obtained at the content of 80mol% Pd. The TOF of Pd-Pt/Al_2O_3 containing 80mol% Pd was 8 times and 18 times higher than those of Pd/Al_2O_3 and Pt/Al_2O_3, respectively.(3)As compared with Pd/Al_2O_3,Pd/TiO_2 showed high TOF and sulfur tolerance, in both the presence of DMDS and the absence of DMDS. Pd-S bond strength was determined by temperature-programmed reduction (H_2S-TPR) profiles. The results show that desorption of H_2S from sulfided Pd/TiO_2 occurs at 553 K, whereas desorption of H_2S from sulfided Pd/Al_2O_3 requires a higher temperature (773 K), indicating that the Pd-S bond in Pd/TiO_2 is significantly weaker than that in Pd/Al_2O_3. Consequently, in Pd/TiO_2 clean surfaces of Pd metals are highly exposed as active sites for the naphthalene hydrogenation in the presence of dimethyldisulfide.