煤热解焦油催化裂解和乙烷水蒸气重整耦合提高焦油品质

Upgrading of coal pyrolysis tar by catalytic cracking coupled with steam reforming of ethane

本文旨在通过在炭基催化剂上发生的煤焦油原位催化裂解与乙烷水蒸气重整过程耦合以提高轻质焦油产率。以平朔煤(PS)为煤样,利用常压固定床反应器在氮气以及乙烷水蒸气混合气氛下进行焦油提质实验,并使用半焦(Char),活性炭(AC)以及活性炭负载金属钴和镍(Co/AC,Ni/AC)作为提质催化剂,对比考察催化剂种类和反应气氛对提质过程中焦油及气体产物的影响。同时,为了解提质过程所得焦油产物的组成和性质,利用模拟蒸馏,GC-MS等表征手段对焦油进行检测分析。结果表明,活性炭负载Ni催化剂(Ni/AC)可催化乙烷水蒸气重整反应,产生的·CH x,·C 2H x,·H等小分子自由基可与焦油催化裂解产生的自由基结合,避免焦油过度裂解。与未加催化剂得到的平朔煤热解焦油相比,采用Ni/AC使轻质焦油(沸点低于360℃馏分)的质量分数和产率分别提高54.3%和52.4%,同时焦油中BTEXN(苯、甲苯、乙苯、二甲苯和萘)等芳烃组分产率明显提高;乙烷水蒸气混合气氛下(耦合过程)比同条件氮气下的焦油产率和轻质焦油产率分别提高38.1%和35.3%,焦油中C2~C3烷基取代苯和C1~C2烷基取代酚的相对含量有明显提高,说明乙烷和水蒸气被活化并参与了焦油形成过程。煤热解焦油的原位催化裂解的总体效果是将焦油中重质组分转化为轻质焦油和热解气,其提质效果与催化剂的活性组分密切相关,且反应气氛在煤焦油的形成过程中具有重要作用。

The purpose of this paper is to improve the light tar yield by coupling in-situ catalytic cracking of coal tar with steam reforming of ethane(SRE)over carbon-based catalysts.The tar upgrading experiments using Pingshuo coal(PS)as coal sample were performed in an atmospheric pressure fixed bed reactor under nitrogen and a mixed atmosphere of ethane and steam.Semi-coke(char),activated carbon(AC),AC supported cobalt and nickel(Co/AC,Ni/AC)were used as upgrading catalysts to comparatively examine the effects of catalyst types and reaction atmosphere on tar and gas products.Meanwhile,the tar was analyzed by means of characterization methods such as simulated distillation and GC-MS in order to understand the composition and properties of the tar product obtained in the upgrading process.The results show that Ni/AC can simultaneously catalyze the coal tar cracking and SRE,thus the small radicals such as·CH x,·C 2H x and·H produced from SRE can combined with the radicals from tar cracking to avoid an excessive cleavage of tar.Compared with the non-upgrading tar,the content and yield of light tar(the fraction having boiling point below 360℃)increase by 54.3%and 52.4%with Ni/AC,respectively.Besides,the yield of aromatic components such as BTEXN(benzene,toluene,ethylbenzene,xylene and naphthalene)in tar is significantly improved.When Ni/AC is used,the tar yield and light tar yield increase by 38.1%and 35.3%,respectively,in the mixed atmosphere of ethane and steam(coupling process)compared with those in nitrogen.Also,the contents of C2-C3 alkyl substituted benzene and C1-C2 alkyl substituted phenol in the tar are improved.It explains the activated ethane and steam participate in the tar formation process.The overall effect of in-situ catalytic cracking of coal pyrolysis tar is to convert heavy components in the tar into light tar and pyrolysis gas.The upgrading effect is closely related to the active components of the catalyst,and the reaction atmosphere plays an important role in the formation of coal tar.