chemical engineering research and design 9 1 ( 2 0 1 3 ) 2663–2670 Contents lists available at ScienceDirect Chemical Engineering Research and Design j ourna l h omepage: www.elsevier.com/locate/cherd Evaluation and modelling of continuous flow sub-critical water hydrolysis of biomass derived components; lipids and carbohydrates M.N. Baig a,∗ , R.C.D. Santos a , J. King b , D. Pioch c , S. Bowra d a School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK b Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA c Génie des Procédés d’Elaboration des Bioproduits, CIRAD Dpt Amis, Montpellier, Cedex 5, France d Department of Research and Development, Phytatec Ltd, Plas Gogerddan, Aberystwyth SY23 3EB, UK a b s t r a c t Sub-critical water is widely accepted as an environmentally benign solvent, for extraction but also as a catalytic medium therefore has the potential to support processing of multiple components found in biomass. The manuscript demonstrates the versatility of sub-critical water as a generic medium to support hydrolysis of rice bran (carbohy- drates) and sunflower oil (lipid substrates), substrates that possess very different physio-chemically properties within a continuous flow process configuration. Response surface methodologies (RSM) were used to assist modelling the multiple process parameters that impact sub-critical water mediate hydrolysis of sunflower oil. Successful validation, of the models illustrate that 100% FFA yield would be achieved at temperature 385 ◦ C; pressure 20 MPa; residence time of 35 min; oil to water ratio 1:1.8 (v/v) represents 65% water. Experiments conducted under these conditions yielded 93.5%, thereby confirming the utility of the RSM as a tool to assist in process development. © 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Hydrolysis; Sub-critical water; Biomass; Lipids; Carbohydrates; Response surface methodology (RSM) 1. Introduction The transition to a knowledge-based bio-economy (KBBE) is the vision within the European Union, US and other devel- oped countries. Supporting the goal of achieving biobased economic development is the increased utilisation of indus- trial biotechnology which will foster more environmentally benign manufacturing and chemical processes. Due to the complexity of biomass and the fact that it is most often in a solid form, there is a need for sustainable and envi- ronmentally friendly pre-treatment process technologies that will enable any biomass or organic waste to be fully utilised without creating waste streams. Critical fluids have increasingly been recognised as envi- ronmentally benign, ‘green’ solvents in part due to their unique physical and chemical properties (King and Srinivas, 2009). Chemists and engineers have begun to exploit both ∗ Corresponding author. Tel.: +44 121 414 6965; fax: +44 121 414 5324. E-mail address: m.n.baig@bham.ac.uk (M.N. Baig). Received 15 September 2012; Received in revised form 18 March 2013; Accepted 26 May 2013 sub and supercritical water as a reaction medium to sup- port extraction and reactions. Water is a cheap, non-toxic, non-combustible and in fact water may be the most benign alternative to organic solvents. Sub-critical water is hot water maintained between 100 ◦ C and 374 ◦ C (critical temperature) and below 22 MPa, its critical pressure. Many studies have been conducted to explore the use of water under sub and supercritical conditions to promote organic reactions. Sub- critical water has successfully been used as a solvent for the extraction of numerous compounds (Lanc ¸as, 2003), primar- ily because the dielectric constant of water can be efficiently modified through modulation of pressure and temperature, thereby ‘mimicking’ organic solvents. Moreover, the ion prod- uct constant for sub critical water is in the order of 10 -11 , which is three orders of magnitude larger than that exhibited by ambient water (Clifford, 1998; Savage, 1999). Due to the vari- ation of the ion product and its acidic nature, sub-critical water 0263-8762/$ – see front matter © 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cherd.2013.05.029