乙烯、丙烯中微量水含量的分析

Determination of Trace Water in Ethylene and Propylene

采用便携式微量水分析仪和库仑法微量水分析仪测定了乙烯、丙烯试样中的微量水含量,对试样的传输系统、进样量的控制、液体试样的气化和水标准气体的制备方法进行了改进,优化了测试条件.以低吸附惰性管线和小死体积单进单出的不锈钢减压器为试样传输系统,缩短了测试时间.采用液态烃闪蒸气化取样进样器气化液体试样并准确控制试样的进样量,可避免液体试样渐次气化对水含量测定结果的影响及对采样钢瓶大小的限制.采用渗透管发生器制备水标准气体,可验证分析结果的准确度.采用库仑法微量水分析仪测定水含量时,试样流量选择600 mL/min较适宜,开封保存15 d之内的卡尔·费休试剂对测定结果无影响.采用便携式微量水分析仪测定水含量时,选择试样流量在400～800 mL/min之间较适宜.两种仪器的测量结果相近,稳定性好,准确度高,回收率在102％～ 107％之间,相对偏差小于10％.

Trace water contents in ethylene and propylene were determined by portable and coulometric analyzer separately. The analysis time was shortened by adopting both inert pipe with low adsorption capacity and tow way stainless steel pressure regulators with small dead volume as transmission system. The restriction of the sample gradual gasification to the sample cylinder and its effect on the water content determination could be avoided by using liquid flash evaporator as sample injector. The accuracy of the analysis results was tested by permeation tube generator, which could generate standard gas with accurate water content. The appropriate sample flowrates were 600 mL/min and 400 - 800 mL/min for the coulometric and portable analyzers, respectively. The Karl Fischer reagent which was unsealed and conserved less than 15 days had no influence on the water content results. The water content determined by coulometric analyzer was close to that measured by portable water analyzer, with good accuracy, recovery in the range of 102% and 107%, and relative deviation of less than 10%.