1,5-己二烯和苯对NiY分子筛脱硫性能的影响

利用固定床、傅里叶红外光谱(FT-IR)及频率响应(FR)等方法研究了1,5-己二烯和苯对NiY分子筛脱硫性能的影响机理. 结果表明, 吸附剂的选择性吸附脱硫性能随着模拟燃料中1,5-己二烯和苯含量的增加而显著降低, 苯的影响比1,5-己二烯更显著. 1,5-己二烯和苯影响NiY脱硫的机理不同, 在吸附剂表面质子酸的作用下, 烯烃与噻吩发生催化反应, 噻吩开环生成烷基噻吩类大分子化合物, 这类吸附堵塞分子筛的孔道, 阻碍硫化物分子进入超笼与其中的金属阳离子吸附活性中心发生吸附作用. 通过FR光谱观察, 得知吸附过程是噻吩在NiY分子筛中传质过程的速控步骤, 扩散过程是苯在NiY分子筛上动力学过程的速控步骤, 这使噻吩从吸附中心上置换下来的苯不易从分子筛孔道中扩散出去, 从而阻碍了噻吩在吸附中心上的吸附.

Effects of 1,5-Hexadiene and Benzene on the Desulfurization Property of NiY Zeolites

Effects of 1,5-hexadiene and benzene on the desulfurization property of NiY were investigated by Fourier transform-infrared (FT-IR), frequency-response (FR), and fixed-bed techniques. Results indicate that both 1,5-hexadiene and benzene inhibit the desulfurization of the sorbent which can be detected by a decrease in the desulfurization capacity of the NiY in the presence of 1,5-hexadiene and benzene in the model fuels. The effect of benzene on the adsorption capacity of the NiY was more conspicuous than that of 1,5-hexadiene. In the zeolite, the sulfur compounds and 1,5-hexadiene adsorbed on the protons can subsequently undergo an opening reaction of the heterocyclic rings, which blocks the zeolite pores and then hinders sulfide molecule access to the supercage where they could come into contact with metal cations. Distinct processes were observed in the FR spectra of thiophene and benzene on NiY zeolites, with the adsorption of thiophene in the supercage being the rate-controlling step and the diffusion process of benzene in the supercage being the rate-controlling step. The benzene molecules were replaced by thiophene molecules from the active centers and they, therefore, diffused out of the zeolite channels with difficulty. The adsorption of thiophene into the active centers will, therefore, be hindered.