Abstract Pyrolysis of waste tires is a promising way to cost-efficiently produce high value limonene, but the reaction characteristics and mechanisms of limonene under pressurized pyrolysis are unclear to date. This study aims to investigate the effects of residence time and pressure on limonene conversion during waste tire pyrolysis. The yields of limonene increased significantly with a decrease of residence time during high pressure pyrolysis. At a pressure of 1.0 MPa, the yield of limonene increases by 20 % as the residence time decreases from 60 s to 15 s, while limonene concentration in TDO (tire-derived-oil) increases to 35.10 wt.%. On the other hand, the pressure has a positive effect on limonene production. The yield of limonene at 1.0 MPa is approximately 1.7 times larger than that of 0.1 MPa at a residence time of 30 s. Based on Spearman correlation analysis, the mechanisms of limonene conversion at pressurized pyrolysis were studied. Longer residence time means limonene undergoes more secondary reactions to be degraded to aromatic rings such as xylene and trimethylbenzene. However, the higher N2 partial pressure during pyrolysis suppressed the decomposition of limonene, producing TDO with high limonene concentration. Therefore, methods of reducing residence time and increasing pressures promote yield and concentration of limonene in the aspect of inhibiting decomposition, which provides references for improvement in limonene production by waste tire pyrolysis.

中文翻译：

---

压力和停留时间对废轮胎热解过程中柠檬烯产量的影响

摘要 废轮胎热解是一种经济高效地生产高价值柠檬烯的有前景的方法，但目前尚不清楚柠檬烯在加压热解下的反应特性和机理。本研究旨在研究停留时间和压力对废轮胎热解过程中柠檬烯转化的影响。在高压热解过程中，随着停留时间的减少，柠檬烯的产率显着增加。在 1.0 MPa 的压力下，随着停留时间从 60 s 减少到 15 s，柠檬烯的产率增加了 20%，而 TDO（轮胎衍生油）中的柠檬烯浓度增加到 35.10 wt.%。另一方面，压力对柠檬烯的生产有积极影响。在 30 s 的停留时间下，1.0 MPa 的柠檬烯的产率大约是 0.1 MPa 的产率的 1.7 倍。基于Spearman相关分析，研究了加压热解时柠檬烯转化的机理。更长的停留时间意味着柠檬烯会经历更多的二次反应，降解为二甲苯和三甲苯等芳环。然而，热解过程中较高的 N2 分压抑制了柠檬烯的分解，产生了具有高柠檬烯浓度的 TDO。因此，减少停留时间和增加压力的方法在抑制分解方面提高了柠檬烯的产率和浓度，为改进废轮胎热解生产柠檬烯提供了参考。更长的停留时间意味着柠檬烯会经历更多的二次反应，降解为二甲苯和三甲苯等芳环。然而，热解过程中较高的 N2 分压抑制了柠檬烯的分解，产生了具有高柠檬烯浓度的 TDO。因此，减少停留时间和增加压力的方法在抑制分解方面提高了柠檬烯的产率和浓度，为改进废轮胎热解生产柠檬烯提供了参考。更长的停留时间意味着柠檬烯会经历更多的二次反应，降解为二甲苯和三甲苯等芳环。然而，热解过程中较高的 N2 分压抑制了柠檬烯的分解，产生了具有高柠檬烯浓度的 TDO。因此，减少停留时间和增加压力的方法在抑制分解方面提高了柠檬烯的产率和浓度，为改进废轮胎热解生产柠檬烯提供了参考。