## 1 Introduction
Also, the production of H\({}_{2}\) by the SCWG of glucose and other biomasses in a batch reactor, at 450 \({}^{\circ}\)C and 340 bar, increased by 80% when NaOH was used as the catalyst [37]. Given these positive results, this study comprises a number of experiments where the effect of adding 0.1 wt % of KOH to a SCWG process at 535 \({}^{\circ}\)C has been determined. SCWG is a promising technology towards the conversion of waste biomass into fuels. However, the application of this process at an industrial scale has some limitations that require more research and development to be overcome. In this regard, significant progress has been made thanks to the research studies that have been conducted at VERENA pilot plant in Germany and at the Japanese plant in Hiroshima University. However, reduced size laboratory reactors, mainly of the batch type, have been used for most of the experimental studies on SCWG that have been completed so far. Only a few researchers have had the opportunity to carry out SCWG experiments using continuous flow tubular reactors with short residence times or continuous stirred tank reactors [38; 39; 40]. Since a continuous flow reactor has been used in the present study, extremely short residence times have been tested. Thus, on the one hand, the experimental conditions were closer to those found at industrial scale and, on the other hand, some of the main problems or limitations associated to batch reactors could be avoided (reduced sample volumes and difficulties to collect solid, liquid and gas phases, side-effects from long preheating times, etc. ), as described by [PERSON] et al. [39]. Such limitations enlighten how important it is to broaden our knowledge on kinetic parameters and a solid validation with experimental data that contribute to improve the design of the reactors and to better predict the distribution of the products to be obtained. Despite its relevance, only a limited number of kinetic models have been reported in the literature. Moreover, this limited information is available on the global kinetics of SCWG [41]. The aim of the present work is to dig into the SCWG processing of cellulose, a biomass model compound, by means of water at supercritical conditions in a continuous reactor and with short residence times. Most previous works on the SCWG of this model compound were carried out in batch reactors and at temperatures below 500 \({}^{\circ}\)C. Moreover, higher residence times are used in those previous studies (of the order of minutes at least). This study should cast some light on the effect of temperature and concentration rates on the SCWG of cellulose with regards to an improved hydrogen production with residence times of a few seconds. The experimental tests have been carried out at temperatures ranging from 450 to 560 \({}^{\circ}\)C, the amount of oxidant ranged from no addition of oxidant to an excess over stoichiometric oxygen of 10% (oxygen coefficient, n = 1.1), the initial concentration of organic matter ranged 0.25 and 2 wt % and, in some cases, 0.1 wt % of KOH was added as the catalyst. Moreover, a comparison study of experimental against theoretical data has been completed.