The catalytic toluene hydrogenation over Ni/SiO₂ was carried out using H₂ or a H₂/H₂O mixture. The toluene conversion and MCH selectivity were evaluated under partial steam pressures 0-10 kPa, at H₂/toluene molar ratios 1-5, and at temperatures 393-453 K. In the absence of steam, toluene conversion increased with increasing H₂ partial pressure, and the MCH selectivity decreased with increasing temperature. In the presence of steam, the toluene conversion showed near-constant activities over the entire range of steam partial pressures, and the MCH selectivity increased with increasing steam partial pressure. This result indicated that the addition of steam inhibited byproduct formation. To clarify the effects of steam on the side-reaction, the byproducts composition was analyzed using a gas chromatograph. The results showed that the addition of steam inhibited demethylation, the ring-opening reaction of MCH, the disproportionation of toluene, and isomerization to convert six-membered ring compounds into five-membered ring compounds.

使用H ₂或H ₂ / H ₂ O混合物在Ni / SiO ₂上进行甲苯催化氢化。在部分蒸汽压力0-10 kPa，H ₂ /甲苯摩尔比1-5和温度393-453 K的条件下评估了甲苯的转化率和MCH的选择性。在没有蒸汽的情况下，甲苯的转化率随H _2的增加而增加。分压和MCH选择性随温度升高而降低。在存在蒸汽的情况下，甲苯转化率在整个蒸汽分压范围内均表现出近乎恒定的活性，并且随着蒸汽分压的增加，MCH的选择性也随之增加。该结果表明添加蒸汽抑制了副产物的形成。为了阐明蒸汽对副反应的影响，使用气相色谱仪分析了副产物的组成。结果表明，蒸汽的加入抑制了脱甲基作用，MCH的开环反应，甲苯的歧化和异构化作用，从而将六元环化合物转化为五元环化合物。