摘要
本文采用纳米碳黑颗粒作为硬模板,在水蒸气气氛下合成了介孔ZSM-5分子筛,使用所合成的介孔ZSM-5分子筛与氧化铝机械混合制备复合载体,担载金属组分制备NiMo/复合载体催化剂,并对其加氢脱硫和加氢脱氮活性进行了评价。
论文系统考察了分子筛合成过程中纳米碳黑颗粒和乙醇的加入比例、晶化时间、焙烧温度对介孔ZSM-5分子筛结构及性质的影响,并得出适宜的合成条件。采用XRD、BET、Py-IR、SEM、TEM、EDAX、AAS等手段对所合成的介孔分子筛进行表征。结果表明,通过选择不同粒径的碳黑颗粒及改变加入碳黑颗粒的比例,可以调控介孔ZSM-5分子筛的孔径分布、孔容大小及孔壁厚度;孔容较小的介孔分子筛具有较高的结晶度、较强的酸性及较好的热稳定性和水热稳定性。
论文采用XRD、BET、Py-IR、NH_3-TPD、HRTEM等手段对载体和催化剂进行表征。表征结果显示,与氧化铝为载体的催化剂相比,引入介孔ZSM-5分子筛使催化剂的介孔孔容和孔径有所增大,B酸中心增多,催化剂表面单层MoS_2晶片的数量减小,MoS_2晶片的平均堆垛层数增加。
分别以DBT和喹啉为模型化合物,利用高压微型反应器对催化剂的加氢脱硫和加氢脱氮进行了活性评价。与氧化铝为载体的催化剂相比,介孔分子筛-氧化铝复合载体催化剂中具有较强的酸性,促进了C-S、C-N键的断裂,提高了催化剂氢解脱硫和脱氮的能力。同时,介孔分子筛的加入,减弱了载体与活性组分间的相互作用,使MoS_2晶片的堆垛层数增加,加氢活性位数量增多,催化剂的加氢活性增强。与微孔分子筛-氧化铝复合载体催化剂相比,介孔分子筛-氧化铝复合载体催化剂具有孔道优势,较大的孔容和孔径降低了大分子的扩散阻力,避免副反应的发生。
In this paper, mesoporous ZSM-5 zeolites was synthesized in air of water steam using nano-carbon particles as the“hard template”. Ni-Mo catalyst with mixture ofγ-Al2O3 and mesoporous zeolite as support was prepared and the catalytic performance in HDS and HDN was evaluated.
The optimal synthesis condition was obtained, after the influence of carbon particles mass, ethanol mass, crystallizing time and calcining temperature on the performances of the mesoporous ZSM-5 zeolites was investigated. The mesoporous zeolites were characterized by XRD, BET, Py-IR, SEM, TEM, EDAX and AAS, and the results showed that the pore size distribution, pore volume and mesoporous wall thickness of the mesoporous zeolites could be controlled by using different carbon particles and changing the mass of the carbon particles. The mesoporous zeolites with smaller pore volume exhibited higher crystallinity, stronger acidity, higher thermal and hydrothermal stability.
In this paper, the carriers and catalysts were characterized by XRD, BET, Py-IR, NH3-TPD and HRTEM. Compared with Ni-Mo/γ-Al_2O_3, catalysts containing mesoporous zeolites showed lager pore volumes, lager pore diameter and more Bronsted acid, the number of single MoS_2 layer decreased and the average number of MoS_2 layers increased.
The evaluation of HDS and HDN catalytic activity was carried out in a high pressure micro-reactor, DBT and quinoline was used as model molecule respectively. Compared with Ni-Mo/γ-Al2O3, the catalysts containing mesoporous zeolites exhibited stronger acidity, and higher desulfurization and denitrogenation activity through the direct hydrogenalysis route. Meanwhile, the reaction between active constituent and carrier was reduced because the existence of mesoporous zeolites in carrier, and the number of MoS_2 layers increased, thus enhanced the forming of more catalytical active sites and the improving of hydrogenation ability. Compared with microporous zeolites-containing catalyst, catalysts containing mesoporous zeolites had lager pore volume and pore size, which reduced the diffusion resistance of large molecules and avoided the happening of side reactions.
引文
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