Danil Korelskiy

A Uniformly Oriented MFI Membrane for Improved CO2 Separation

Membrane separation of CO2 from natural gas, biogas, synthesis gas, and flu gas is a simple and energy-efficient alternative to other separation techniques. But results for CO2 -selective permeance have always been achieved by randomly oriented and thick zeolite membranes. Thin, oriented membranes have great potential to realize high-flux and high-selectivity separation of mixtures at low energy cost. We now report a facile method for preparing silica MFI membranes in fluoride media on a graded alumina support. In the resulting membrane straight channels are uniformly vertically aligned and the membrane has a thickness of 0.5 μm. The membrane showed a separation selectivity of 109 for CO2/H2 mixtures and a CO2 permeance of 51×10(-7) mol m(-2) s(-1) Pa(-1) at -35 °C, making it promising for practical CO2 separation from mixtures.

Efficient ceramic zeolite membranes for CO2/H2 separation

Membranes are considered one of the most promising technologies for CO2 separation from industrially important gas mixtures like synthesis gas or natural gas. In order for the membrane separation process to be efficient, membranes, in addition to being cost-effective, should be durable and possess high flux and sufficient selectivity. Current CO2-selective membranes are low flux polymeric membranes with limited chemical and thermal stability. In the present work, robust and high flux ceramic MFI zeolite membranes were prepared and evaluated for separation of CO2 from H2, a process of great importance to synthesis gas processing, in a broad temperature range of 235–310 K and at an industrially relevant feed pressure of 9 bar. The observed membrane separation performance in terms of both selectivity and flux was superior to that previously reported for the state-of-the-art CO2-selective zeolite and polymeric membranes. Our initial cost estimate of the membrane modules showed that the present membranes were economically viable. We also showed that the ceramic zeolite membrane separation system would be much more compact than a system relying on polymeric membranes. Our findings therefore suggest that the developed high flux ceramic zeolite membranes have great potential for selective, cost-effective and sustainable removal of CO2 from synthesis gas.

MFI zeolite as adsorbent for selective recovery of hydrocarbons from ABE fermentation broths

Abstract1-Butanol and butyric acid are two interesting compounds that may be produced by acetone, butanol, and ethanol fermentation using e.g. Clostridium acetobutylicum. The main drawback, restricting the commercialization potential of this process, is the toxicity of butanol for the cell culture resulting in low concentrations of this compound in the broth. To make this process economically viable, an efficient recovery process has to be developed. In this work, a hydrophobic MFI type zeolite with high silica to alumina ratio was evaluated as adsorbent for the recovery of butanol and butyric acid from model solutions. Dual component adsorption experiments revealed that both butanol and butyric acid showed a high affinity for the hydrophobic MFI zeolite when adsorbed from aqueous model solutions. Multicomponent adsorption experiments using model solutions, mimicking real fermentation broths, revealed that the adsorbent was very selective to the target compounds. Further, the adsorption of butyric and acetic acid was found to be pH dependent with high adsorption below, and low adsorption above, the respective pKa values of the acids. Thermal desorption of butanol from MFI type zeolite was also studied and a suitable desorption temperature was identified.

Selective blocking of grain boundary defects in high-flux zeolite membranes by coking

Commercial application of zeolite membranes has been hindered by the challenge of preparing defect-free membranes. Herein, we report a facile method able to selectively plug grain boundary defects in high-flux MFI zeolite membranes by coking of iso-propanol at 350 °C. After modification, the permeance via defects was reduced by 70%, whereas that via zeolite pores was reduced by only 10%.