School of Chemical Engineering,Dalian University of Technology

为探究硫在煤直接液化反应中的作用,基于L9(34)正交试验设计,考察初压、温度、H2S在H2S/H2混合气中体积分数、硫/铁(S/Fe)摩尔比等因素对上湾煤在铁基催化剂下直接液化的煤总转化率、油产率、油中硫质量分数、氢耗率等的影响。结果表明:温度对油产率的影响最显著,从420~470℃油产率提升19.0%;H2S的加入可使氢耗率略有降低,油和气产率提高,但同时使油中硫质量分数增大;当H2S从0提高到1.0%时,氢耗率降低0.3%,油中硫质量分数从0提高至0.9%;S/Fe摩尔比在合适范围内可提升油产率,S/Fe摩尔比为0.8时油产率比S/Fe为1.6时高3.6%,比不加硫高7.2%。煤液化过程加入的单质硫大多迁移至四氢呋喃不溶物(即液化残渣,THFI),S/Fe摩尔比不为0时THFI中硫质量分数普遍高于2%。在正交试验基础上,进一步研究了纯氢气氛下不同S/Fe摩尔比、恒定S/Fe摩尔比下不同H2S体积分数的液化过程,从硫元素在油、沥青烯的分布,结合产物红外光谱表征、总自由基浓度测定,推测H2S、单质硫的作用机制及液化反应中硫的迁移规律。发现THFI总自由基浓度与油产率、氢耗率存在一定程度的关联,S/Fe摩尔比为1.2时油产率最高,与此相对应的THFI总自由基浓度存在极小值;H2S体积分数为0.25%时氢耗率明显增大,对应的THFI、沥青烯总自由基浓度亦有明显变化。H2S易作用于油与沥青烯的前驱体,并促进重质组分向轻质组分的转化,单质硫过量时也能与沥青烯前驱体作用。在煤直接液化过程中,H2S、单质硫的共同点是促进气相供氢,而对沥青烯官能团结构影响不明显。

Direct coal liquefaction reactivity under sulfur’s effect was studied via L9(3) orthogonal experimental design. Pressure,temperature,H2S volume content in H2S/H2,and S/Fe mole ratio were considered as factors while total conversion,oil yield,sulfurcontent of oil,and hydrogen consumption ratio as the target indexes. The sulfur migration mechanism in the reaction was inferredaccording to the results. The following conclusions could be confirmed or inferred from this work:Temperature has a remarkable effect onoil yield. From 420 ℃ to 470 ℃,there’s an average increase of 19.0% in oil yield. H2S plays three roles:hydrogen consumption ratiodecrease,light product (including oil and gas) generation,yet more sulfur content of oil. There is a decrease of 0.3% hydrogenconsumption ratio and an increase of 0.9% sulfur content of oil ranging from 0- 1% H2S volume content. S/Fe mole ratio within thereasonable range can promote oil yield,as 0.8 S/Fe mole ratio achieves a better oil yield than both 0(extra- 7.2%) and 1.6(extra-3.6%). During the processing of DCL,elemental sulfur migrates to THFI mostly,as there’s an extra 2% sulfur content of THFI if onlyelemental sulfur is added in the reaction system. According to the results of the orthogonal experiment,the liquefaction experiments withdifferent S/Fe molar ratios in a pure hydrogen atmosphere,and different H2S volume content in H2S/H2 under a constant 0.4 S/Fe molar ratio were further studied. From the distribution of sulfur in oil and asphaltene,combined with the changes in functional group,and freeradical concentration,the effect mechanism of H2S and elemental sulfur and the migration rule of sulfur in coal liquefaction reaction werededuced. It was indicated that the free radical concentration of THFI is to some extent related to both oil yield and hydrogen consumption.Oil yield shows a peak value at 1.2 S/Fe atomic ratio while the free radical concentration of THFI gets its minimal value. At 0.25% H2Scontent,the hydrogen consumption rises apparently while the free radical concentration of THFI reaches bottom peak. It seems to beeasier for H2S than elemental sulfur to react with the precursor of light products,and promote conversion of heavy fraction to the lightproducts. Only in excessive amounts can elemental sulfur combine with asphaltenes slightly. The common point of H2S and elementalsulfur is that they promote hydrogen supply in the gas phase,but have no obvious effect on the functional groups of asphaltene.

国家重点研发计划资助项目(2022YFB4101302);中国神华煤制油化工有限公司揭榜挂帅资助项目(MZYHG-22-02)

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LI Panyu,YANG He,LI Yang,et al. Effects of sulfur on direct coal liquefaction and sulfur migration mechanism[J].CleanCoal Technology,2025,31(3):147−155.