Sid-Ahmed Rezzoug

Liquefaction of wood in two successive steps: solvolysis in ethylene-glycol and catalytic hydrotreatment

The purpose of this paper is to describe a process of wood liquefaction in two steps: a first step of wood solvolysis in acidified ethylene-glycol or in some recycled solvent; a second step of catalytic hydrogenation at high pressure of the solvolysis liquid product. For the solvolysis step, the liquefaction yield is limited by the acidity of reactant media and by the formation of a coke-like residue. A kinetic model of solvolysis is proposed accounting for the production of the coke-like residue. When using recycled solvolytic oil instead of fresh ethylene-glycol, the conversion into liquid is also reduced and the viscosity of the solution strongly increases. The step of hydrogenation was investigated by varying different parameters, i.e., the nature of the catalyst, the initial hydrogen pressure (30-60-90 MPa), the maximal temperature of plateau (from 330 to 400 °C) and the ratio tetralin/solvolytic oil. A slightly better deoxygenating rate is obtained by using a Ni-Mo bi-functional catalyst. The deoxygenation rate increases with the tetralin/solvolytic oil ratio and a minimum value of 0.5 for this ratio is necessary to prevent the unwanted formation of a solid residue. After hydrogenation, an upgraded oil is obtained with a heating value similar to that of a usual petroleum fuel.

Solvolysis and hydrotreatment of wood to provide fuel

The objective of this study is to describe a liquefaction process of wood in two successive steps. The wood is first dissolved in an organic solvent, acidified with small amounts of H2SO4, in mild conditions of temperature and pressure. The solvolytic oil is then subjected to a catalytic hydrotreatment at about 350°C. In the first step, whatever the tested solvent, simple alcohol, phenol or ethylene glycol, the best experimental conditions prevail when the amount of H2SO4 is not higher than 1% (with respect to dry wood) and the temperature is not over 250°C. A mixture of phenol-tetralin (5050 by mass) is a good solvent media and can be recycled several times in batch tests. The solvolytic oil is upgraded under H2 pressure in the presence of tetralin. The tetralin/solvolytic oil ratio is one of the tested parameters. A ratio as low as 1 results in a good hydrotreatment and avoids the processing of too large quantities of tetralin, difficult to separate from the other compounds. The effectiveness of the hydrotreatment is evaluated from the viscosity and the oxygen content of the upgraded oil. The best deoxygenation is obtained with NiMo as catalyst.

Impact of ultrasound on solid–liquid extraction of phenolic compounds from maritime pine sawdust waste. Kinetics, optimization and large scale experiments

Maritime pine sawdust, a by-product from industry of wood transformation, has been investigated as a potential source of polyphenols which were extracted by ultrasound-assisted maceration (UAM). UAM was optimized for enhancing extraction efficiency of polyphenols and reducing time-consuming. In a first time, a preliminary study was carried out to optimize the solid/liquid ratio (6g of dry material per mL) and the particle size (0.26 cm(2)) by conventional maceration (CVM). Under these conditions, the optimum conditions for polyphenols extraction by UAM, obtained by response surface methodology, were 0.67 W/cm(2) for the ultrasonic intensity (UI), 40°C for the processing temperature (T) and 43 min for the sonication time (t). UAM was compared with CVM, the results showed that the quantity of polyphenols was improved by 40% (342.4 and 233.5mg of catechin equivalent per 100g of dry basis, respectively for UAM and CVM). A multistage cross-current extraction procedure allowed evaluating the real impact of UAM on the solid-liquid extraction enhancement. The potential industrialization of this procedure was implemented through a transition from a lab sonicated reactor (3 L) to a large scale one with 30 L volume.

DEVELOPMENT OF A NEW DRYING PROCESS – DEHYDRATION BY CYCLICAL PRESSURE DROPS (D.D.S.): APPLICATION TO THE COLLAGEN GEL

ABSTRACT Experiments to dry a collagen gel in order to obtain a homogenous film were carried out using a new process: dehydration by successive decompression “DDS” (Déshydratation par Détentes Successives). This process, particularly suited to thermosensitive products, involves a series of cycles during which the collagen gel is placed in desiccated air at a given pressure then subjected to an instantaneous (200 ms) pressure drop to a vacuum (7–90 kPa). This paper assesses the effect of four parameters of this drying process, namely high pressure (P h) and vacuum pressure (P v) and the effect of the duration at these pressures (t h and t v) on the drying rate, and the temperature of the collagen gel during drying. A comparative study between this new drying process and conventional methods indicated that the drying time was reduced from 480 and 700 min for vacuum and hot air drying respectively to 270 min for our process.

Isolation of Rosemary Oils by Different Processes

Abstract Rosemary oil may be isolated by three different processes, including steam distillation, water distillation and controlled instantaneous decompression. The concrete resulting from extraction by volatile organic solvents was also made using hexane, dichloromethane and ethanol. The oils and extracts obtained were analyzed by gas chromatography (GC) and gas chromatography coupled to mass spectroscopy (GC/MS) in order to determine their chemical composition. A scanning electron microscope was used to observe the impact of different processes on the structure of leaves and essential oil bearing trichomes.

Chemical Composition and Insecticidal Properties of Thymus numidicus (Poiret) Essential Oil from Algeria

Abstract Essential oils of thyme (Thymus numidicus (Poiret)) from Algeria were isolated by steam distillation, analysed by gas chromatography coupled with the mass spectrometry (GC-MS) and investigated for their insecticidal activities against Rhizopertha dominica. Contact toxicity of global oil recovered after one hour of extraction and its fraction F1 recovered after 2.5 minutes of extraction were tested using the filter paper method. Analysis of the essential oil made it possible to identify 14 components, representing 75.4 % of the oil. The major components were thymol (51.0 %) followed by carvacrol (9.4 %), linalool (3.3 %), thymol-methyl-ether (3.2 %) and iso-caryophyllene (2.7 %). The evolution of the yield and the composition of essential oil as function of time extraction show that steam distillation is a very rapid process and the duration of extraction could be limited to 15 minutes, since more than 94 % of oil are extracted. The toxicity tests show that thyme oil and its fraction F1 have an insecticidal activity, nevertheless, the mortality obtained for global oil are weaker compared with those obtained for the F1 fraction. This toxicity would be allotted to the presence in strong proportion of linalool and thymol.

KINETICS OF DRYING AND HYDRATION OF THE SCLEROGLUCAN POLYMER. A COMPARATIVE STUDY OF TWO CONVENTIONAL DRYING METHODS WITH A NEW DRYING PROCESS: DEHYDRATION BY SUCCESSIVE PRESSURE DROPS

The scleroglucan polysaccharides are mainly used in the petroleum industry but also have applications in the food, cosmetics and pharmaceutical industries. For most of these applications, the dissolution rate of hydrocolloïds is an important qualitative criterion. In this study, the kinetics of scleroglucan drying was investigated with the aim of improving the hydration capacity and the dissolution rate of the polymer. Two conventional methods (hot air and vacuum drying) were compared with a new drying process: dehydration by successive pressure drops, or DDS (Déshydratation par Détentes Successives). This process involves processing the polymer in a series of cycles that consist in placing it in desiccated air then subjecting it to an instantaneous (200 msec) decompression to a vacuum (50 mbar). Two parameters were varied: pressure (P: 4.5–7.5 bars) and processing time at this pressure (t = 5–10 sec). During each decompression, a certain quantity of water is eliminated by vaporisation, improving the diffusion of water by capillary action during hydration. Our results showed that processing time at high-pressure (P) has a significant effect on the drying kinetics. In contrast, processing pressure was not a critical parameter. The results showed that hot air and vacuum drying of scleroglucan are less effective techniques.

Effect of the Main Processing Parameters of the Instantaneous Controlled Pressure Drop Process on Oil Isolation from Rosemary Leaves. Kinetics Aspects

Abstract Experiments to isolate the essential oil from rosemary (Rosmarinus officinalis L.) were carried out using a new extraction process: “Détente Instantanée Contrôlée” (D.I.C) or “Controlled Instantaneous Pressure drop.” This process involves subjecting the rosemary leaves for a short period of time to a steam pressure, followed by an instantaneous pressure drop to a vacuum (about 15 mbar). This paper aims to assess the effect of processing pressure, processing time and initial moisture content of leaves before D.I.C. treatment on the extraction efficiency. The processing pressure varied from 0.5 to 5 bar, the processing time from 1 to 21 minutes and initial moisture content from 0.1 to 0.6 g H2O/g dm. It appears that a pressure of about 1 bar, and a treatment time less than 10 minutes are sufficient to extract more than 97% of the essential oil. The moisture content was not a critical parameter for the isolation efficiency. A stable yield and composition of the oil was obtained whatever the value of this parameter. The oil was also studied by quantitative and qualitative chemical analysis, the effect of modifying the operating conditions on the isolation of 10 components of the rosemary oil namely α-pinene, camphene, β-pinene, 1,8-cineole, camphor, borneol, terpinen-4-ol, α-terpineol, bornyl acetate and β-caryophyllene.

Isolation of Volatiles from Oak Wood (Quercus alba) by a Thermomechanical Process: Screening of some Processing Parameters

Experiments were performed to evaluate an extraction process developed in our laboratory called the instantaneous controlled pressure drop process (“Détente Instantanée Contrôlée” or (DIC)) for extracting volatile compounds from oak wood. This process involves subjecting oak chips for a short time (10 s to 12 min) under a steam pressure (1 to 6 bars or from 100 to 165°C). This first step is followed by a rapid decompression toward vacuum (up to 50 mbar). Some parameters were evaluated: steam pressure level, processing time, initial moisture content, chips thickness and velocity of the rapid decompression. A preliminary experimental design allowed optimizing the processing pressure and processing time: 6 bar and 5 minutes. Under these conditions, the optimal conditions were as follows: 20% for initial moisture content, 0.5 mm for the chips thickness. The number of decompressions towards vacuum was also investigated and it appeared that extraction yield can be enhanced by repeating the decompressions cycles for a same processing time. Moreover, GC-MS analysis indicated that DIC extract included the same molecules that obtained by steam distillation with almost the same percentages.

Solid-state 13C NMR Study of Scleroglucan Polysaccharide. Effect of the Drying Process and Hydration on Scleroglucan Structure and Dynamics

Abstract High-resolution solid-state 13C CP/MAS NMR was used to study the evolution of a polysaccharide (scleroglucan) conformation from the anhydrous to the hydrated form. The influence of a thermo-mechanical treatment applied during the drying process of scleroglucan is analyzed both on the dried and rehydrated product. 13C NMR spectra, 13C relaxation times (T 1C) and 1H relaxation times in the rotating frame (T 1ρH) of scleroglucan dried by using instantaneous controlled pressure drop (Détente Instantanée Controlée™) were analyzed in order to explain the observed differences of rehydration capacity. Although the scleroglucan treated at 6 bar has the same conformational state (triple-helix) as the one treated at 1 bar, it shows two different relaxation times T 1C for the C-3 carbon involved in the interglycosidic linkage. The magnetization decay of the hydrated sample exhibits a decrease of two time constants with significant shortening of the spin-lattice relaxation times T 1C that accounts for the higher mobility of the chains. High-pressure treatment creates highly rigid and compact domains. Consequently, water molecules cannot readily access the inside of the triple-helix and relax the interchain hydrogen bonds.