無(wu)(wu)煙(yan)煤(mei)濾(lv)料中的炭分子通(tong)常被認為是無(wu)(wu)定(ding)形碳。X射線衍(yan)射分析表明,它結構中含(han)有1-3nm的石墨微晶,所以又(you)有人認為它屬于微晶類(lei)碳。這些無(wu)(wu)煙(yan)煤(mei)濾(lv)料基(ji)團可分為酸性(xing)基(ji)團和堿(jian)性(xing)基(ji)團兩大類(lei)。
高溫活化(800-900℃)容(rong)易(yi)(yi)形成(cheng)堿(jian)性基(ji)(ji)團,炭分(fen)子低(di)溫活化(300-500℃以(yi)下(xia))容(rong)易(yi)(yi)形成(cheng)酸性基(ji)(ji)團。常見(jian)的(de)酸性基(ji)(ji)團以(yi)羥基(ji)(ji)、內脂基(ji)(ji)為(wei)(wei)主,常見(jian)的(de)堿(jian)性基(ji)(ji)團是(shi)含(han)有氧(yang)萘結構(gou)的(de)基(ji)(ji)團,基(ji)(ji)團的(de)數量大約為(wei)(wei)0.1-0.5mmol/g。
無煙煤濾(lv)料中炭(tan)分子(zi)主要的(de)結構特(te)征是(shi)它的(de)碳分子(zi)孔(kong)結構。描述孔(kong)結構的(de)指標是(shi)比(bi)表而積,孔(kong)徑(jing)、孔(kong)徑(jing)分布(bu)和孔(kong)容(rong)。炭(tan)分子(zi)吸附所依賴的(de)巨大比(bi)表面積主要是(shi)內部(bu)孔(kong)洞(dong)的(de)表現。如果對孔(kong)的(de)大小進行區分,則(ze)可以分為微孔(kong)、過渡孔(kong)(中孔(kong))和大孔(kong)三種。
按國(guo)際純粹化(hua)學和應用化(hua)學聯(lian)合會(hui)的(de)規定,微孔(kong)是指孔(kong)直徑小于2nm的(de)孔(kong),無煙煤(mei)濾料中(zhong)孔(kong)是指孔(kong)直徑為2~50nm的(de)孔(kong),大(da)孔(kong)是指直徑大(da)于50nm的(de)孔(kong)。
無煙煤濾(lv)料孔(kong)(kong)(kong)徑(jing)分布測(ce)定(ding)方法(fa)(fa)有電子顯微鏡(jing)法(fa)(fa)、分子篩法(fa)(fa)、壓(ya)汞(gong)(gong)(gong)法(fa)(fa)、X射線小角度散射法(fa)(fa)等,常(chang)用的(de)是(shi)壓(ya)汞(gong)(gong)(gong)法(fa)(fa),該(gai)法(fa)(fa)是(shi)利用汞(gong)(gong)(gong)不潤濕活性炭細(xi)孔(kong)(kong)(kong)壁,要讓汞(gong)(gong)(gong)進(jin)入細(xi)孔(kong)(kong)(kong)中就需要壓(ya)力這一原理,通過下式進(jin)行計(ji)算:rp'=-2vcoso 式中:r-圓筒形細(xi)孔(kong)(kong)(kong)的(de)孔(kong)(kong)(kong)半徑(jing);p-汞(gong)(gong)(gong)的(de)壓(ya)力;v-汞(gong)(gong)(gong)的(de)表面(mian)張力;o-汞(gong)(gong)(gong)的(de)接觸角。在壓(ya)力P下,汞(gong)(gong)(gong)應該(gai)進(jin)入半徑(jing)r以(yi)上(shang)的(de)所(suo)有細(xi)孔(kong)(kong)(kong)中,所(suo)以(yi)測(ce)定(ding)由于壓(ya)力的(de)變化而引起(qi)進(jin)入汞(gong)(gong)(gong)量(liang)的(de)變化,就可以(yi)知道孔(kong)(kong)(kong)徑(jing)太小,進(jin)而確(que)定(ding)孔(kong)(kong)(kong)徑(jing)分布。