A 3D-Printed Zeolitic Imidazolate Framework-8 Monolith For Flue- and Biogas Separations by Adsorption: Influence of Flow Distribution and Process Parameters

Brieuc Verougstraete,Jasper Lefevere,Dieter Schuddinck,Gino V Baron,Joeri F M Denayer

doi:10.3389/fceng.2020.589686

Abstract

Improving the efficiency of gas separation processes for CO2 capture is primordial. In the field of adsorptive separation processes, a shift to structured adsorbents, more especially monoliths, can be seen. These offer better efficiency, better mass transfer characteristics and a lower pressure drop compared to the conventional shape of adsorbents. This could lead to short adsorption/desorption cycles, which is crucial. In this study we analyzed a 3D-fiber deposited ZIF-8 monolith. The resulting interwoven structure of the monolith has the advantage to allow for radial diffusion in between the channels. Therefore, the gas flow distribution inside the monolith was investigated. This was done experimentally, but also in silico. Next, breakthrough experiments were performed to study the influence of flow rate and desorption time, since ZIF-8 can easily be regenerated. It was seen that flowing air through the monolith for 6 s was sufficient to regenerate the monolith. Regarding the hydrophobicity of ZIF-8, the presence of water vapor in the gas stream was investigated. Lastly, the selectivity of ZIF-8 for CO2 over CH4 was determined.

Highlights

Over the last years, an increasing interest in structured adsorbents, and monoliths, can be noticed
For the zeolitic imidazolate framework (ZIF)-8 Monolith For CO2 Capture extrusion process, the paste will pass through a die, which is expensive to produce and limits the structures that can be obtained
The synthesis of the 3D-printed ZIF-8 monolith and its performance in the adsorption of butanol has already been published in earlier work (Lefevere et al, 2019; Claessens et al, 2020)

Summary

Introduction

An increasing interest in structured adsorbents, and monoliths, can be noticed. Compared to conventionally shaped adsorbents like beads or pellets, these structures lead to lower pressure drop and an improved mass and heat transfer (Avila et al, 2005; Rezaei and Webley, 2009; Rezaei and Webley, 2010; Rezaei and Grahn, 2012; Hasan et al, 2013) As a result, they allow higher gas velocities and can lead to much shorter cycle times in an adsorption/desorption cycle. Due to the need for short cycles in the field of CO2 capture, monolithic structures are becoming more important (Hasan et al, 2013; Middelkoop et al, 2019) To prepare these monoliths, traditional methods consist of coating a support monolith with the adsorbent or directly by extrusion (Williams, 2001; Avila et al, 2005; Akhtar et al, 2014; Govender and Friedrich, 2017). A variety of structures that are complex or impossible to produce with traditional methods, are made available (Lee et al, 2017; Ruiz-Morales et al, 2017)

Methods

Results

Conclusion