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《Zeolites》1989,9(4):329-335
H-erionite is very active for n-heptane cracking at 450°C, but its deactivation is almost instantaneous. This rapid deactivation is not due to a high coking rate but to a pronounced deactivating effect of coke that is characteristic of pore blockage. With short reaction time, “coke” is constituted of volatile compounds: isobutene, mono, and bi or triaromatics blocked in the erionite cages. These compounds lead through oligomerization, alkylation, cyclization, hydrogen transfer … to polyaromatic molecules with 3–6 aromatic rings. Each molecule can be located in one single erionite cage. Adsorption experiments show that each molecule blocks the access not only to the cage in which it is located but to several other cages. With long reaction time, highly polyaromatic compounds (> 6 aromatic rings) are formed through condensation of the less polyaromatic ones. They occupy several erionite cages or overflow unto the outer surface of the zeolite crystallite. 相似文献
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《Journal of power sources》2004,129(1):81-89
In processing heavier hydrocarbons such as military logistic fuels (JP-4, JP-5, JP-8, and JP-100), kerosene, gasoline, and diesel to produce hydrogen for fuel cell use, several issues arise. First, these fuels have high sulfur content, which can poison and deactivate components of the reforming process and the fuel cell stack; second, these fuels may contain non-volatile residue (NVR), up to 1.5 vol.%, which could potentially accumulate in a fuel processor; and third is the high coking potential of heavy hydrocarbons. Catalytic cracking of a distillate fuel prior to reforming can resolve these issues. Cracking using an appropriate catalyst can convert the various heavy organosulfur species in the fuel to lighter sulfur species such as hydrogen sulfide (H2S), facilitating subsequent sulfur adsorption on zinc oxide (ZnO). Cracking followed by separation of light cracked gas from heavies effectively eliminates non-volatile aromatic species. Catalytic cracking can also convert heavier hydrocarbons to lights (C1–C3) at high conversion, which reduces the potential for coke formation in the reforming process. In this study, two types of catalysts were compared for JP-8 cracking performance: commercially-available zeolite materials similar to catalysts formulated for fluidized catalytic cracking (FCC) processes, and a novel manganese/alumina catalyst, which was previously reported to provide high selectivity to lights and low coke yield. Experiments were designed to test each catalyst’s effectiveness under the high space velocity conditions necessary for use in compact, lightweight fuel processor systems. Cracking conversion results, as well as sulfur and hydrocarbon distributions in the light cracked gas, are presented for the two catalysts to provide a performance comparison. 相似文献
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In this work, the composites with multilayered distribution of the mica were fabricated by a multilayer coextrusion technique. The influence of layer number on sound insulation and mechanical properties of multilayered composites was investigated. The distribution, dispersion and orientation of mica particulates in composites were characterized by PLM and SEM. The sound insulation property of composites was measured by four microphone impedance tube. PLM and SEM images showed that the mica was distributed as the multilayered structure along the thickness direction of the composites. With the increase of layer number, more mica aggregates delaminated into thin flakes and aligned parallel to the flow direction. Compared to the conventional composites, the multilayered composites showed the enhanced sound insulation efficiency and mechanical properties. The discontinuity of sound impedance and the improved stiffness were considered to play a crucial role in the improvement of sound transmission loss. 相似文献
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为研究4种不同典型结构的轨道车辆车体用碳纤维复合材料的火灾危险性,引入多种测试方法,依据其在傅里叶变换红外烟气毒性测试系统、NBS烟密度箱、火焰蔓延测试仪和锥形量热仪中的试验数据,运用层次分析法,建立了以毒性指数作为毒性危险指标、烟密度峰值作为烟气危险指标、火焰蔓延最远距离作为火焰蔓延危险指标以及平均热释放速率峰值和热释放总量作为放热危险指标的火灾危险性综合评价模型,并依据该模型对碳纤维复合材料进行了火灾危险性综合评价。结果表明,多腔结构碳纤维复合材料的火灾危险性综合指数为0.342,聚甲基丙烯酰亚胺(PMI)泡沫夹层结构碳纤维复合材料的火灾危险性综合指数为0.312,聚对苯二甲酸乙二酯(PET)泡沫夹层结构碳纤维复合材料的火灾危险性综合指数为0.250,层压板结构碳纤维复合材料的火灾危险性综合指数为0.169,火灾危险性排序为：多腔结构碳纤维复合材料＞PMI泡沫夹层结构碳纤维复合材料＞PET泡沫夹层结构碳纤维复合材料＞层压板结构碳纤维复合材料,该评价方法弥补了单项指标评价的不足,可较为全面、合理地反映轨道车辆复合材料的火灾危险性。 相似文献
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李佳霖;龚晓波;于尧;高广军;李健 《中南大学学报(英文版)》2023,30(8):2726-2739
在列车撞击动力学中,简化的刚体模型被广泛应用于研究列车耐撞性,以及进一步优化列车在冲击载荷下的能量分布。然而忽略弹性波传播对列车耐撞性能的影响尚不清楚。为了解决这一问题,本文建立了简化的一维弹性车体模型,并研究了弹性波传播对列车能量耗散以及动力学特性的影响。基于经典的弹性波传播理论,提出了一种密度及弹性模量缩比准则,使一维弹性车体的运动特性与其横截面积无关。讨论了弹性波传播速度对不同冲击速度下三节编组列车在冲击工况下的能量吸收、弹性能储存以及车体最终的等效平衡速度的影响。研究发现,当弹性波的传播速度约为3500 m/s时,一维弹性车体与实际列车模型的一致性最好。在初始冲击速度为10、15和20 m/s时,简化的一维弹性模型吸能量与实际列车模型相比误差仅为2.56%、1.84%和1.45%,而简化的刚性模型能量吸收量比实际列车模型高10.7%、12.4%和14.8%,刚性模型显著高估了列车的能量吸收量。我们的研究结果可以促进列车在碰撞条件下的耐撞性设计和优化。 相似文献
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为满足高速开关阀在复杂时变环境下的控制需求,通过数学模型分析,提出阈值占空比自学习的高速开关阀自适应控制算法。自学习阶段,通过自学习方波自适应调整阈值占空比,满足复杂时变环境控制需求;压力控制阶段,采用混合脉宽激励——“积分+斜率”控制算法,在缩短压力响应时间的同时,减少动态调节时的超调量。实验验证表明,在不同环境温度下,方波跟随响应时间不超过350 ms,超调量不超过0.25 MPa,稳态误差不超过0.1 MPa;1 Hz正弦波动态跟随性能良好,因此高速开关阀自适应控制算法在复杂时变环境中具有良好的自适应和鲁棒性。 相似文献