混合二甲苯系统热力学平衡组成的计算

研究混合二甲苯模型中3种组分在不同温度下的热力学平衡组成,依据状态函数特点,分别计算各平衡的标准摩尔反应熵变、标准摩尔反应焓变及标准摩尔吉布斯自由能变,进而计算平衡组成。结果表明,在该混合二甲苯理想气体模型中,反应温度由298.15 K升至1 023.15 K,混合二甲苯中3个平衡组成随着反应温度升高呈如下变化规律:间二甲苯含量y(MX)由0.599 0逐渐降至0.496 3,降幅达17.15%;邻二甲苯含量y(OX)由0.162 6逐渐升至0.275 9,升幅达69.68%;对二甲苯含量y(PX)由0.238 4缓慢升至0.242 6,而后逐渐降至0.227 7,最大值出现在423.15 K,最大降幅仅为6.14%,表明升高温度不利于提高对二甲苯的平衡组成。

Calculation of thermodynamic equilibrium compositions of mixed xylenes

The thermodynamic equilibriums of three components of mixed xylenes model under different temperatures were researched.Based on the characteristics of the state function,three thermodynamic functions △rS_m^Θ(T),△rH_m^Θ(T) and △rG_m^Θ(T) of three equilibriums components under different temperatures were calculated,respectively.And then the equilibrium compositions were calculated.The results showed that in the ideal gas model of mixed xylene,the change rules of the three equilibrium compositions with the increase of reaction temperatures from 298.15 K to 1 023.15 K were as follows:the y_(MX) of m-xylene contents reduced gradually from 0.599 0 to 0.496 3 with the drop of 17.15%;the y_(OX) of o-xylene contents enhanced gradually from 0.162 6 to 0.275 9 with the increase of 69.68%;the y_(PX) of p-xylene contents increased slowly from 0.238 4 to 0.242 6,and then decreased gradually to 0.227 7.Its maximum of 0.242 6 at 423.15 K with the biggest drop of 6.14% was obtained,which indicated that increasing temperature was unfavorable to improving balance composition of p-xylene.