  Computational studies addressing the adsorption of fluids in nano-porous
materials mostly use ideal single crystal models of the adsorbent. While a few
recent studies have tried to address the effects of inter-crystalline spacing
on the adsorption of fluids in polycrystalline models of nano-porous materials,
the effects of the orientational disorder in the polycrystalline adsorbent
remain unexplored. Here we report the adsorption of SO$_2$, an industrially and
environmentally important gas, in ZSM-22, a zeolite characterized by straight
channel like pores. The simple pore geometry of ZSM-22 helps us make
polycrystalline models of the adsorbent with different degrees of orientational
disorder. Using grand canonical Monte Carlo (GCMC) simulations, we obtain the
adsorption isotherms of SO$_2$ in ZSM-22 with different inter-crystalline
spacings and degree of orientational disorder. Introducing inter-crystalline
space is found to enhance the adsorption capacity, with a larger
inter-crystalline space leading to higher adsorption. Increasing the
orientational disorder of the adsorbent is found to enhance the adsorption
capacity too. However, the effects of orientational disorder become weaker when
the inter-crystalline space is widened. This weakening of the effect of
orientational disorder is a result of an interplay between the width of the
inter-crystalline space and the strength of guest-guest interactions.
