EDITORIAL: Conversion of Biomass into Biofuels with Supercritical Fluids
Pages 101-102
Tevfik Aysu

Published: 17 October 2016 

Energy Production by Hydrothermal Treatment of Liquid and Solid Waste from Industrial Olive Oil Production
Pages 103-116
Pau Casademont-Lanzat, Belen García-Jarana, Xiaowei Chen, Carol Maritza Olmos Carreño, Jezabel Sánchez-Oneto, Juan R.Portela and Enrique J. Martínez de la Ossa

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.03.1

Published: 17 October 2016

Abstract: This work studies the use of olive oil mill waste (OMW) treated as subcritical or supercritical water to produce both, a biofuel by liquefaction and a gas fuel by gasification. The increasing amount of OMW, both liquid and solid, is becoming a serious environmental problem. This wastewater is highly resistant to biodegradation and contains a wide variety of compounds such as polyphenols, polyoils, organic acids, etc, that require depuration treatments to remove the odour and pollutant load before being discharged.

This work studies both, liquefaction and gasification of OMW streams in subcritical and supercritical water in different batch reactors at temperatures between 200 and 530 ºC and pressures between 150 and 250 bar. This study also tests the effectiveness of various types of homogeneous (KOH 0.01 g/g_{sample dry}) and heterogeneous catalysts (TiO₂, V₂O₅ and Au-Pd 0.1-0.5 g/g_{sample dry}) for supercritical water gasification (SCWG) and studied the way they affect biomass conversion yields. It also covers the effect that the use of different organic compound concentrations (23, 35, and 80 g O₂/l of chemical oxygen demand concentration (COD)) and compositions (mixtures of solid and liquid OMW) has on energy production results. A maximum of 82% oil yield was obtained from the hydrothermal liquefaction of OMW under optimum conditions (330 ºC, 150 bar, 23 g O₂/l as initial concentration and 30 minutes reaction time). Meanwhile, a yield of 88.6 mol H₂/kg_{OMW dry} was obtained when Au-Pd was used as a catalyst for the gasification of OMW supercritical water.

Production and Characterization of Energy Materials with Adsorbent Properties by Hydrothermal Processing of Corn Stover with Subcritical H₂O
Pages 117-130
N.T. Machado, D.A.R. de Castro, L.S. Queiroz, M.C. Santos and C.E.F. da Costa

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.03.2

Published: 17 October 2016

Abstract: This work aims to investigate the effect of temperature on the process performance of hydrothermal processing (HTC) of corn Stover with subcritical H₂O and on the morphology of solid products. The experiments were carried out at 200, 225 and 250 ºC, reaction time of 240 minutes, heating rate of 2.0 ºC/min, and biomass to water ratio of 1:10, using a pilot scale stirred tank reactor (STR) of 5 gallon, operating in batch mode. The process performance analyzed by computing the yields of solid and liquid reaction products (RLP). The aqueous phase (H₂O + RLP) was physicochemical analyzed for pH and total carboxylic acids, expressed as total acetic acid content. The chemical compositions of carboxylic acids, furfural, and hydroxymethylfurfural (HMF) in the aqueous phase determined by GC-MS and HPLC. The results showed solid yields ranging from 57.39 to 35.82% (wt.), and liquid reaction products (RLP) yields ranging from 39.53 to 54.59% (wt.). The solid phase products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The chemically activated (2.0 M NaOH) solid phase energy material obtained by HTC at 250°C, applied as adsorbent to investigate the capacity and/or efficiency to adsorb acetic acid from 1.0 to 4.0 g/L model solutions at 25 °C. The solid phase yield decreases along with the temperature, showing an inflection region between 200 and 225 °C, whereas a drastic change takes place, while that of liquid phase increases, showing also a drastic change between 200 and 225 °C. The total acetic acid content of aqueous phase varied from 4064 to 5387 mg/L, while the pH from 3.77 to 3.91. The GC analysis identified the presence of volatile carboxylic acids, particularly acetic acid, in concentrations between 4020 and 5040 mg/L. HPLC identified the presence of furfural and hydroxymethylfurfural, whose concentrations decrease exponentially and linearly along with the temperature between 686.7 and 0.0, and 443.9 and 0.0 mg/L, respectively, being both compounds not detectable at 250 °C. The elemental/ultimate analysis of solid products shows that carbon content increases, while the oxygen and hydrogen contents decrease, along with the temperature. The H/C and O/C ratios decrease linearly as process temperature increases, and the high heating value (HHV) of solid reaction products, an energy densified material, changes sharply between 200 and 225 °C, showing an increase with temperature. The SEM, EDX, and XDR indicates a change on the morphology and mineralogical phases present in solid reaction products with temperature, particularly at 250 °C. The activated solid phase has proven to be very selective to adsorb acetic acid, showing that recovery of acetic acid from hydrothermal carbonization/liquefaction aqueous solutions is feasible by using a multistage-stage adsorption process in series.

Effects of Phenol Addition on Oil Extraction from Moroccan Oil Shale by Supercritical Toluene
Pages 131-138
A.Abourriche, M.Oumam, A. Benhammou, M. Mouiya, Y. Elhafiane, Y. Abouliatim, L. Nibou, H. Hannache, M. Birot, R. Paillerand R. Naslain

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.03.3

Published: 17 October 2016

Abstract: In the present work, the effect of phenol on the supercritical extraction of the organic matter from Tarfaya's oil shale with toluene was evaluated. The experimental results showed clearly that phenol had a significant effect on the yield and the composition of the oils obtained. Moreover, it was shown that phenol was a very efficient modifier for oil shale, giving a good yield of recovery and a suitable maturation of the organic matter. The pitches prepared by mixing phenol and toluene contain more aromatics and have a high char yield at 950 °C compared to those obtained by extraction with supercritical toluene alone.

Regeneration of Activated Carbon Sutured Hexavalent Chrome
Pages 103-116
K. Elmerzouki, I. Bimaghra and A. Khalidi

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.03.4

Published: 17 October 2016

Abstract: In order to prevent a simple pollution transfer and for the purpose of valorization of the process of activated carbon treatment, this one, saturated with pollutants should not increase the pollution mass of household waste. Indeed, an adsorbent offers a real interest only if it can be easily regenerated. This work addresses to the becoming the activated carbon after being saturation with hexavalent chromium. The activated carbon should not be stored directly, since the acid rain waters might leach some heavy metals. This would contaminate the soil and water resources. For this, it should be treated after use and returned to its original structure and chemical composition for an eventual future use with a good yield of re-adsorption. Within this work, the use of a base (KOH) has recovered an amount of hexavalent chromium retained by the activated carbon CAB. This one, regenerated was again used to secure the hexavalent chromium ions during several cycles. Regeneration test results have shown that the efficacy of CAB remains almost constant during the first four cycles of reuse and then decreases during the fifth cycle.