油品的閃點、燃(ran)(ran)點與(yu)自燃(ran)(ran)點與(yu)油品的組成關(guan)系:

1.與化(hua)學組(zu)成有關:通常情況下(xia)，烷(wan)烴(jing)(jing)比芳烴(jing)(jing)容易氧化(hua)，故含烷(wan)烴(jing)(jing)多(duo)的油品(pin)自燃(ran)點比較(jiao)低，但其閃點卻比粘度相(xiang)同(tong)而(er)含環(huan)烷(wan)烴(jing)(jing)和芳烴(jing)(jing)較(jiao)多(duo)的油品(pin)高。在同(tong)類烴(jing)(jing)中，隨相(xiang)對(dui)分(fen)子質量增(zeng)大，自燃(ran)點降(jiang)低，而(er)閃點和燃(ran)點增(zeng)高。對(dui)碳原子數相(xiang)同(tong)的烴(jing)(jing)類，自燃(ran)點的順序為烷(wan)烴(jing)(jing)<環(huan)烷(wan)烴(jing)(jing)，烯(xi)烴(jing)(jing)<芳烴(jing)(jing);嫩點的順序正好相(xiang)反(fan):烷(wan)烴(jing)(jing)>環(huan)烷(wan)烴(jing)(jing)，烯(xi)烴(jing)(jing)>芳烴(jing)(jing)。

2.與餾分組(zu)成有關:油(you)品的(de)閃(shan)點(dian)與其(qi)蒸氣(qi)壓有關，亦(yi)與其(qi)餾分組(zu)成有關，油(you)品的(de)沸點(dian)越高(gao)、餾分越重、相對(dui)分子質量越大，其(qi)閃(shan)點(dian)越高(gao)。反之,油(you)品的(de)沸點(dian)越低，餾分越輕(qing)，相對(dui)分子質量越小，越易揮發,其(qi)閃(shan)點(dian)和燃點(dian)越低。油(you)品閃(shan)點(dian)和燃

點(dian)(dian)(dian)(dian)的(de)(de)高(gao)(gao)低(di)(di)取決(jue)于低(di)(di)沸點(dian)(dian)(dian)(dian)烴(jing)類含(han)(han)量(liang)，烷烴(jing)的(de)(de)閃(shan)(shan)點(dian)(dian)(dian)(dian)比對(dui)應(ying)的(de)(de)烯烴(jing)要高(gao)(gao)。油(you)品閃(shan)(shan)點(dian)(dian)(dian)(dian)的(de)(de)高(gao)(gao)低(di)(di)取決(jue)于油(you)品中(zhong)沸點(dian)(dian)(dian)(dian)zui低(di)(di)的(de)(de)那部分烴(jing)類的(de)(de)含(han)(han)量(liang)。當有極少量(liang)輕油(you)混人到(dao)高(gao)(gao)沸點(dian)(dian)(dian)(dian)油(you)品中(zhong)時，就能引起閃(shan)(shan)點(dian)(dian)(dian)(dian)顯(xian)著(zhu)降低(di)(di)。例(li)如(ru)，某潤滑油(you)中(zhong)摻(chan)人1%的(de)(de)汽油(you)，閃(shan)(shan)點(dian)(dian)(dian)(dian)可從200°C降至(zhi)170°C。正是由于這一原因，原油(you)的(de)(de)閃(shan)(shan)點(dian)(dian)(dian)(dian)是很低(di)(di)的(de)(de)，它和低(di)(di)閃(shan)(shan)點(dian)(dian)(dian)(dian)油(you)品一起被列人易(yi)燃(ran)(ran)物品之(zhi)中(zhong)。與燃(ran)(ran)點(dian)(dian)(dian)(dian)相反(fan)，油(you)品的(de)(de)沸點(dian)(dian)(dian)(dian)越(yue)(yue)低(di)(di)，越(yue)(yue)不(bu)易(yi)自(zi)(zi)燃(ran)(ran)，其自(zi)(zi)燃(ran)(ran)點(dian)(dian)(dian)(dian)就越(yue)(yue)高(gao)(gao);反(fan)之(zhi)，自(zi)(zi)燃(ran)(ran)點(dian)(dian)(dian)(dian)越(yue)(yue)低(di)(di)。對(dui)同-烴(jing)類沸點(dian)(dian)(dian)(dian)越(yue)(yue)高(gao)(gao)其燃(ran)(ran)點(dian)(dian)(dian)(dian)越(yue)(yue)高(gao)(gao)沸點(dian)(dian)(dian)(dian)越(yue)(yue)高(gao)(gao)其自(zi)(zi)燃(ran)(ran)點(dian)(dian)(dian)(dian)反(fan)而較低(di)(di)。