连续相变的加氢反应器

引　言加氢反应是一类强放热反应 ,在采用滴流床反应器的情况下 ,经常遇到由于液体分布不均而导致的催化剂不完全润湿的现象[1] 。当液体反应物中含有挥发性组分时 ,在一定条件下 ,液相反应物可能会蒸发 ,伴随着反应速度的突然增加[2 ] ,使催化剂局部过热而失活 .另外 ,由于液体在催化剂床层中的不均匀分布而使床层出现未被润湿的干区 ,在强放热反应中 ,会经常观察到出现热点 ,床层的轴向温度出现振荡[3] .两相并流向上的固定床反应器 ,由于床层内的持液量较高 ,液体分布均匀 ,催化剂能很好地润湿 ,因此有可能避免出现热点[4 ] .这种操作形…

FIXED-BED HYDROGENATION WITH CONTINUOUS PHASE TRANSITION

A new hydrogenation method was introduced in an adiabatic fixed-bed reactor with gas and liquid upflow cocurrently. Three reaction regimes, i.e., liquid phase regime, mixed phase regime and gas phase regime were observed in the bed through regulating the operating conditions. Hydrogenation of benzene to cyclohexane over palladium catalyst was used as the model reaction. The effects of hydrogen flow rate, liquid flow rate, feed temperature and pressure on the flow regime were studied. For exothermic reactions, a small increase in reaction temperature can lead to a large increase in reaction rate due to Arrhenius temperature dependence of rate constant .The increased reaction rate results in more heat generation which further increases reaction temperature, this may results in reactor runaway. In this work, we propose that it is possible to obtain effective temperature control by using a fixed-bed reactor with cocurrent upflow of the reagents. The reaction heat evolved is absorbed by evaporation of the liquid phase. The experiments showed that the conversion of benzene in the reactor with this new kind of operation could reach almost 100%, and the risk due to hot spots appearance may also be avoided.