Steam explosion method

Joseph et had also prepared the oil palm microfibril-reinforced NR composites by conventional mechanical blending. The used microfibrils were separated from the oil palm fibres by using the steam explosion method, and were subsequently subjected to treatments such as mercerization, benzoylation, and silane treatment. They found that the storage modulus value of untreated and treated microfibril-reinforced NR composites was higher than that of macrofibre-reinforced composites. The Tg values of microfibril-reinforced composites were slightly higher than that of macrofibre-reinforced composites. The treated microfibril-reinforced NR composites displayed better adhesion between fibre and NR matrix. 

Steam explosion is a thermomechanical process. At high pressure, steam penetrates to cellulose fiber through diffusion and when the pressure suddenly releases, creates shear force, hydrolysis of the glycosidic and hydrogen bonds and leads to formation of nanofibers [126]. In 1927, Mason introduced the steam explosion method to defibril-late wood to fiber for board production [127]. The effective parameters of this process are pressure, temperature and time of material being autoclaved. The steam explosion process can be used solely or in combination with other processes. For instance, cellulose nanofibers from banana at 20 lb pressure, 110-120°C, for 1 hour [16] and from pineapple at 20 lb pressure [128] were produced just using steam explosion. 

Yamamoto, Y., Okubo, K., and Fujii, T. (2002) Development of eco-composite using bamboo fibers - FRPP using bamboo fibers extracted by the steam explosion method. Proceedings of the International Workshop on Green Compo, Society of Material Science, Japan, pp. 30-34. 

From recent literature it is known that the disintegration of lignified cell walls can be achieved by steam explosion treatments resulting in solubilization of partially depolymerized hemicelluloses [91,92]. The application of this method on wheat bran yielded feruloylated GAX with different feruUc acid content [93]. Partly depolymerized water-soluble, acetylated AGX was obtained from spruce wood by employing microwave treatment [94]. 

Possible hazards introduced by variations in experimental techniques in Kjeldahl nitrogen determination were discussed [1]. Modem variations involving use of improved catalysts and hydrogen peroxide to increase reaction rates, and of automated methods, have considerably improved safety aspects [2], An anecdote is given of the classic technique when sodium hydroxide was to be added to the sulphuric acid digestion and was allowed to trickle down the wall of the flask. It layered over the sulphuric acid. Gentle mixing then provoked rapid reaction and a steam explosion [3],... 

Production of ammonia (NH ) Anhydrous (dry) ammonia is the fifth most produced industrial compound. The Haber-Bosch process uses steam on hot coke, which is mostly used in South Africa. In the United States, it is mostly produced from partial combustion of natural gas (methane) or by combining several gases using steam. Other methods use coke-oven gas, refinery gas (mostly methane), or even solar energy. Ammonia is toxic if inhaled and has a high pH value when mixed with water (hydration) to form ammonium hydroxide (NH OH), which has many uses, including as a household cleaner. Ammonia forms many compounds, including ammonium nitrate in fertilizer, rocket fuel, and explosives. Ammonia is also explosive when mixed with mercury or silver or when mixed as part of nitrocellulose. 

The steam explosion process is a recent development in wood processing (1,2). Much attention has been paid to this process from the viewpoint of total wood utilization. Cellulose and hemicellulose from this process can be converted into sugars of commercial value by enzymatic methods (3). However, the conversion of lignin from this process (steam explosion lignin) into useful materials continues to present difficulties. Preparation of adhesives from it is considered to be a feasible way to solve this problem. 

Although there are still some problems, such as the ineffective methylo-lation of the phenolated SEL and the selection of a suitable extender, it can generally be concluded that phenolysis is a promising method to develop steam explosion lignin into attractive adhesives comparable to commercial phenolic resin. 

A typical wood-to-ethanol bioconversion process consists of at least three major steps pretreatment, hydrolysis, and fermentation. The pretreatment stage has been shown to be the key step to providing a substrate susceptible to the subsequent hydrolysis. Steam explosion is one of the most intensively studied pretreatment methods for bioconversion of softwood materials (6-10). 

Dekker, R. F. H. 1991. Steam explosion an effective pretreatment method for use in the bioconversion of lignocellulosic materials. In Focher, B., Marzetti, A., and Crescenzi, V. (Eds.), Steam Explosion Techniques Fundamental Principles and Industrial Applications (pp. 277-305). Philadlphia PA Gordon and Breach Scientific Publishers-. 

Biomass material (woodchips or wheat straw) is placed in a high-pressure stainless steel tube and exposed to steam under pressures ranging from 250-650 psi at 200 to 240°C for up to 20 min. The sudden pressure release causes an explosion of biomass material thereby disrupting the lignin and hemicellulose bonding toward cellulose. Many investigators (see [29] for review) have studied the steam explosion of biomass materials. The addition of SO2 enhances the pretreatment effect and also increases the recovery of hemicellulose [34-36]. A refinement of this pretreatment method has recently been reported by Stenberg et al. [37]. 

AFEX is the pretreatment method that utilizes steam explosion techniques using ammonia as the chemical reagent [38-41]. The intended biomass material is placed in a pressure vessel with liquid ammonia (1 1 basis) and treated... 

Com stover used for this study was harvested in 2003 at the Kramer Farm in Wray, Colorado. The stover was pretreated either in-house at the National Renewable Energy Laboratory or received via subcontract fiom the CAFI [12] pretreatment group members. The samples selected for this study were pietreated by alkaline peroxide (NREL), sulfite steam explosion (UBC), ammonia fiber explosion (MSU), and dilute sulfuric acid (NREL) methods. The composition of the pretreated stover was determined by a two-stage sulfuric acid hydrolysis treatment according to the NREL Laboratory Analytical Procedure titled Determination of Stmctural Carbohydrates and Lignin in Biomass [13]. The pretreatment conditions and compositional information for each substrate are listed in Table 2. 

In cellulosic ethanol production processes, a pretreatment procedure is needed to disrupt the recalcitrant structure of the lignocellulosic materials so that the cellulose can be more efficiently hydrolyzed by cellulase enzymes [2], These pretreatments include physical, biological, and chemical ways, such as uncatalyzed steam explosion, liquid hot water, dilute acid, flow-through acid pretreatment, lime, ammonium fiber/freeze explosion, and ammonium recycle percolation [3, 4], Most of these methods involve a high temperature requirement, which is usually achieved through convection- or conduction-based heating. 

Commercially, most cellulose is extracted from wood by one of two methods, the kraft (sulfate) process or the steam explosion process. The product of these reactions is wood pulp, which consists primarily of cellulose. In the kraft process, wood chips are treated with a solution of sodium hydroxide (NaOH) and sodium sulfide (Na2S) at temperatures of about 175°C (35o°F) for two to six hours. This process usually results in a yield of about 40 to 45 percent wood pulp. The pulp is then treated with a bleaching agent, such as calcium or sodium hypochlorite (Ca(0Cl)2 or NaCIO) or chlorine dioxide (C102) to remove the color of lignin and other impurities. 

Common chemical pre-treatment methods use dilute acid, alkaline, ammonia, organic solvent, sulphur dioxide or other chemicals.Some pre-treatment methods can use only water such as steam explosion or liquid hot water (LKW). " Steam explosion is one of the most promising methods to make biomass more accessible to cellulose attack. The material is heated using high-pressure steam (20-50 bar, 210-290 °C) for a few minutes these reactions are then stopped by sudden decompression to atmospheric pressure. 

The pretreatment of any lignocellulosic biomass is cmcial before enzymatic hydrolysis. The objective of pretreatment is to decrease the crystallinity of cellulose which enhances the hydrolysis of cellulose by cellulases (17). Various pretreatment options are available to fractionate, solubilize, hydrolyze and separate cellulose, hemicellulose and lignin components (1,18-20). These include concentrated acid (27), dilute acid (22), SOj (25), alkali (24, 25), hydrogen peroxide (26), wet-oxidation (27), steam explosion (autohydrolysis) (28), ammonia fiber explosion (AFEX) (29), CO2 explosion (30), liquid hot water (31) and organic solvent treatments (52). In each option, the biomass is reduced in size and its physical structure is opened. Some methods of pretreatment of Lignocellulose is given in Table I. 

However, not all of these methods are desired for pretreatment of the lignocellulosic materials because of technical or economic feasibility. In some cases, a mediod is used to increase the efficiency of another method. For instance, milling could be applied to create a better steam explosion by reducing the chip size (8). Furthermore, it should be noticed that the selection of pretreatment method should be compatible widi the selection of hydrolysis. For example, if acid hydrolysis is to be applied, a pretreatment with alkali may not be beneficial. The most commonly applied pretreatment methods will be discussed here. 

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