水蒸气对煤焦油模化物裂解行为及析碳的影响

采用机械化学法制备Ni-Ce/Al₂O₃催化剂，在固定床反应器中考察了水蒸气气氛对煤焦油模型化合物甲苯＋芘催化裂解行为的影响。根据产物生成规律提出了芘向萘转化的裂解机理，并以D₂O对其进行了验证。通过XRD、TG-DTG和Raman等表征了析碳的类型与结构特征。结果表明：相较于纯氮气气氛，水的加入可明显提升重质组分芘的裂解率，且随水碳比（S/C）增加呈先增加后降低的趋势，在S/C=0.15时达到最大值98.93%，比S/C=0时增加32.09%。析碳率随S/C比增加一直呈下降趋势，由S/C=0时的10.04%降至S/C=0.26时的5.39%。析碳分析结果表明，S/C=0时，生成的积炭类型主要是β型碳及γ型碳，水蒸气存在时，活性较高的α型碳含量增加，说明水蒸气的持续消碳作用抑制了C_α向C_β与C_γ方向转化。

Effect of steam atmosphere on cracking behavior and carbon deposition of coal tar model compounds

The Ni-Ce/Al₂O₃ catalyst was synthesized via mechanochemical method. The effects of steam on the cracking behavior of toluene and pyrene as coal tar model compounds were investigated in a fixed bed reactor. Based on the product distribution, the cracking mechanism of the conversion of pyrene to naphthalene was proposed and verified by D₂O as a tracer. The types and structural characteristics of carbon deposition on the spent catalysts were characterized by XRD, TG-DTG and Raman, etc. The results showed that the addition of steam obviously enhanced the cracking rate of pyrene, compared with the pure nitrogen atmosphere, and it increased first and then decreased with the increase of steam-carbon ratio (S/C) and reaching a maximum of 98.93% at S/C=0.15, increased by 32.09% in comparison with S/C=0. A downward trend was that the yield of carbon decomposition decreased from 10.04% to 5.39% with the increase of S/C ratio from 0 to 0.26. In addition, carbon analysis results show that the main type of carbon deposits were β-type and γ-type at S/C=0. On the contrary, in the presence of steam, the activity of higher α-type carbon content increased. Therefore, it indicated that the carbon elimination by steam inhibited the conversion of C_α to C_β and C_γ.