Kinetics of adsorptive desulfurization over alkaline-treated Beta zeolite

doi:10.11949/j.issn.0438-1157.20160245

Abstract

Abstract:

When molecular size of an adsorbate is as large as the pore size of molecular sieves, the adsorbate can enter into the pore structure and thus the pore size of molecular sieves is a critical factor in determining adsorption performance. To improve adsorbate selectivity and diffusion, Beta molecular sieves were modified by alkaline treatment of NaOH solution. The treated Beta molecular sieves were characterized by analytical techniques of BET, TEM, FT-IR, XRD and NH₃-TPD to investigate the alkaline treatment process on crystal structure, surface acidity and pore structure. Adsorption desulfurization showed that both adsorption quantity and adsorption rate of alkaline-treated Beta molecular sieves were improved obviously. Especially the adsorption of large-kinetic-sized dibenzothiophene reached to 5.06 mg·g^-1. The kinetics of adsorbing dibenzothiophene on Beta molecular sieves was a pseudo-2nd-order adsorption process. After alkaline treatment, rate constants of both adsorption and molecular diffusion inside pores were increased significantly, which in turn improved mass transfer of diffusion inside porous structures and desulfurization efficiency of sulfur compounds.

Key words: alkaline treatment, adsorption, desulfurization, kinetics, mass transfer

摘要：

当吸附质尺寸与分子筛的孔结构尺寸相当时才能进入分子筛的内部，分子筛的孔道尺寸是影响吸附性能的重要因素之一，NaOH溶液处理可实现分子筛孔径的调变，以改善分子筛对吸附质的选择性和扩散传质能力。通过对碱处理后的Beta分子筛进行BET、TEM、FT-IR、XRD和NH₃-TPD表征，以考察碱处理对Beta分子筛晶体结构、表面酸性和孔结构参数的影响。碱处理Beta分子筛吸附脱硫的结果显示，碱处理后Beta分子筛吸附量和吸附速率明显增加，尤其动力学尺寸较大的二苯并噻吩吸附量达到了5.06 mg·g^-1。吸附动力学研究显示，该吸附过程符合准二级动力学方程，碱处理后分子筛吸附速率常数和粒子内扩散速率常数明显增大，有效地改善了硫化合物在孔道内扩散传质性能，脱硫效率增加。

关键词: 碱处理, 吸附, 脱硫, 动力学, 传质

CLC Number:

TQ028.3

PAN Xingpeng, WU Xiangying, DU Jun, QIAN Mingchao, YU Jiang. Kinetics of adsorptive desulfurization over alkaline-treated Beta zeolite[J]. CIESC Journal, 2016, 67(9): 3747-3754.

潘兴朋, 吴相英, 杜君, 钱明超, 余江. 碱处理Beta分子筛吸附脱硫动力学[J]. 化工学报, 2016, 67(9): 3747-3754.

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