Studying a gas–solid multi-component adsorption process with near-infrared process analytical technique: Experimental setup, chemometrics, adsorption kinetics and mechanism

The study on multi-component or competitive gas–solid adsorption process is a challenge to current theories as well as experimental methods. In the paper, a methodology composed of near-infrared spectroscopy, process analytical technique and chemometrics has been tried to investigate the adsorption process of orthoxylene/aniline onto active alumina surface. The adsorption process took place in a differential adsorption bed, which was non-invasively monitored by a near-infrared spectrometer via optical fiber probe, and spectra were collected at every minute during the whole adsorption process. After treating these spectra with chemometrics algorithms, including wavelet analysis, partial least squares and artificial neural network, the adsorption process has been investigated thoroughly as well as clearly: not only the adsorption rates of each adsorbates at various adsorption times but also a great deal of information about the mechanism of the adsorption process. For example, orthoxylene was adsorbed evenly on the active alumina surface, while aniline was adsorbed uprightly; aniline was adsorbed to fabricate the first and the second adsorption layer on the adsorbent surface simultaneously rather than to construct them in sequence or step by step; and some parts of the adsorbent surface was more active for adsorption.