Efficient Downstream Processing of Renewable Alcohols Using Zeolite Adsorbents
Increasing energy prices, global warming, and concerns for environmental pollution has been pushing the chemical industry to look for alternatives for traditional, fossil-based chemical feedstocks. Important platform molecules are alcohols, which can be p
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Efficient Downstream Processing of Renewable Alcohols Using Zeolite Adsorbents Benjamin Claessens, Julien Cousin-Saint-Remi, and Joeri F. M. Denayer
Contents 1 The Production of Renewable Alcohols in a Biorefinery 2 MFI Zeolites: ZSM-5 and Silicalite-1 2.1 Structure and Selectivity 2.2 Which Channel to Choose? The Adsorption Mechanism of Alcohols on MFI Zeolites 2.3 The Adsorption of Water: Si/Al Ratio, Cations, Defects, and Co-adsorption 2.4 Diffusion of Alcohols and Water in MFI Frameworks 2.5 Process Aspects and Mixture Separation 3 Cage-and-Window-Type Zeolites: LTA and CHA 3.1 Framework Structure 3.2 Equilibrium: Chain-Length and Entropic Effects 3.3 Kinetics: Co-diffusion and Crystal Diversity 3.4 Separation of ABE Mixtures on ITQ-29 and CHA Zeolites 3.5 Combining the Selectivity of CHA and LTA Zeolites 4 Conclusions and Future Perspectives References
Abstract Increasing energy prices, global warming, and concerns for environmental pollution has been pushing the chemical industry to look for alternatives for traditional, fossil-based chemical feedstocks. Important platform molecules are alcohols, which can be produced from renewable feedstocks via fermentation. The implementation of these fermentation processes to produce chemicals leads to important challenges regarding the downstream purification. Adsorption-based purification technologies are alternatives for traditional energy-intensive distillation processes. The well-defined pore structure of zeolites makes them ideal candidates for the removal of alcohols from these complex fermentation mixtures, which contain cells and cell debris, acids, sugars, lipids, and proteins. The following B. Claessens, J. Cousin-Saint-Remi, and J. F. M. Denayer (*) Vrije Universiteit Brussel, Brussels, Belgium e-mail: [email protected]
B. Claessens et al.
chapter covers important aspects in the adsorption mechanism of alcohols and water in (mainly) hydrophobic zeolite pores, such as cluster formation and hydrogen bonding. These effects inevitably also play a role when looking at the diffusion of alcohols inside the zeolite pores. Finally, this chapter will cover some examples of studies where hydrophobic zeolites have been used to recover bio-alcohols, such as biobutanol and bioethanol, from model solutions or fermentation broths via fixedbed separations. Keywords Adsorption · Biobutanol · Chabazite · LTA · Silicalite
1 The Production of Renewable Alcohols in a Biorefinery Important environmental challenges, such as global warming and pollution, lead to an increasing pressure on chemical industry to move away from fossil-based feedstocks. An alternative source of energy (fuels) and materials (platform chemicals) is waste biomass from the agricultural or food industry. The conversion of biomass to fuels and chemicals can be performed either via more traditional, catalytic processes [1–3] or via bioconversion or fermentation processes, based on the use of enzymes and microorganisms [1, 4–8]. In fermentation processes, a biomass-based substrate is very selectively converted i
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