The Engineering Meetings Board has approved this paper for publication. It has su ccessfully completed SAE’s peer review process under the supervision of the session organizer. This process requires a mini mum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form o r by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not nec essarily those of SAE. The author is solely responsible for the content of the paper. SAE Customer Service: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: [email protected] SAE Web Address: http://www.sae.org Printed in USA 2009-01-2578 An Investigation into the Carbon Dioxide Removal Performance of a Novel Hydrophobic Adsorbent Gareth Toft and Tony Aitchison QinetiQ Copyright © 2009 QinetiQ Limited. Pub lished by SAE International with permission. ABSTRACT Under contract to the UK Mi nistry of Defence (MoD), QinetiQ has been investigat ing the feasibility of an atmospheric carbon dioxide removal system, based on a novel hydrophobic adsorbent produced by impregnating mesoporous silica MCM41 with an imine. The silica/imine material has been found to perform better in humid conditions than when dry. This is in contrast to traditional zeolite molecular sieves, where carbon dioxide adsorption is adverse ly affected by the presence of water. The use of a hydrophobic adsorbent that functions regardless of the presence of water vapour, has the potential to greatly simplify temperature swing molecular adsorption systems by eliminating the need for an up-stream dryer bed, wh ilst eliminating the risk of the ammonia and monoethanolamine emissions associated with ‘wet amine’ scrubbers. The objective of the present work was to establish the performance characteristics of the adsorbent under a range of carbon dioxide concentrations, humidities and regeneration conditions. INTRODUCTION The current technology employed onboard the UK Royal Navy’s submarine fleet for atmospheric carbon dioxide (CO 2) removal, is the monoethanolamine packed tower scrubber (MPT). Whilst this technology has proven effective, there is a potential risk of release of low levels of ammonia and monoethanolamine into a submarine’s atmosphere during operation. As part of its on-going commitment to improve the working environment of its personnel, and to reduce potential health risks to ‘as low as reasonably practicable’ (ALA RP), the British Ministry of Defence (MoD) is seeking an alternative carbon dioxide removal technology. QinetiQ has been studying a temperature swing carbon dioxide removal system based on a novel hydrophobic adsorbent. The solid-phase adsorbent is produced by impregnating mesoporous silica MCM41 with a low vapour pressure, carbon dioxide absorbing, imine. The porous structure of the silic a provides a support for the imine, whilst its large internal surface area allows a high density of absorbent per unit mass. In a traditional temperature swing adsorption system drying beds of zeolite 3A or silica gel, are required before the zeolite 5A adsorption beds, to ensure any water, that would otherwi se impede absorption of CO 2 by the 5A bed, is removed. This two stage arrangement greatly complicates the system. The novelty of the modified MCM41 material under investigation is that it has been found to perform better in humid conditions than when dry. The use of a material that functions regardless of the presence of water vapour, has the potential to greatly simplify temperature swing adsorption systems, while a