Comparative study on properties of nanocellulose derived from sustainable biomass resources

Cellulose - Nanocellulose, a unique and promising nanosized cellulose fibers extracted from renewable biomass, has gained much attention from both the scientific and industrial communities due to...     

Hydrogen yield from water radiolysis in the presence of zeolites

This paper reports a study of the decomposition of water by gamma radiolysis in the presence of zeolites ZSM-5, SAPO-5, and MOR. The irradiation is performed using ⁶⁰Co as a source with 1.12×10¹⁵ Bq activity at a 8.3 kGy/h dose rate. The stable products of radiolysis as well as the other chemical species are measured by mass spectrometry. The calculated radiation yield (G_{H 2}) generally decreases in the order: H-ZSM-5>Na-ZSM-5>H-SAPO-5>MOR under the given experimental conditions; the yield is higher in the presence of these catalysts than in their absence.     

Purification of carbohydrate-containing substrates from plant biomass hydrolysates

Carbohydrate-containing substrates are produced in Russia by means of dilute acid hydrolysis of wood and vegetable residues. Hydrolysates contain 3 to 4% monosaccharides and nearly 1% impurities. The common schemes used to prepare the hydrolysate for fermentation include cooling by self-evaporation; inversion of oligosaccharides; neutralization of sulfuric (and organic) acids; addition of mineral food substances containing nutrient N, P, and K salts; aeration to coagulate colloidal substances; and sedimentation of residues. Our work led to the suggestion that a flocculation step using cationic polyelectrolytes be added to purify more completely the substrates from lignin-huminic substances (LHS). This method permits the transfer of a part of the dissolved and colloidal LHS into a suspended state and the removal of more than 90% of the suspended materials, thereby increasing the yield and quality of ethanol and fodder yeast. Three industrial plants have reported successful results using this method in the past few years. Flocculation has also proven itself capable of clearing waste culture liquids of their dispersed phases by extents of 30–60%, as measured by chemical oxygen demand, color depth, or lignin content parameters, prior to consideration of such wastewater for recycling.     

Influence of ionization density on radiolysis of cyclohexane-benzene mixtures

Cyclohexane-benzene mixtures were irradiated by ²¹⁰Po-α-radiation (LET = 200 eV/nm) with the effective energy of 3 MeV and the results were compared with those obtained by 1.25 MeV λ-irradiation of ⁶⁰Co (LET = 0.2 eV/nm). While during λ-irradiation—similarly to the data known from the literature—the G(c-C₆H₁₀) and the G((c-C₆H₁₁)₂) values were decreased even by a small amount of benzene, the yields of both products obtained by α-irradiation were in the same range practically constant, and began to decrease only above the benzene concentration of 0.3 mol dm^-3 (about 3 electron %).The “protection” in the case of λ-irradiation was interpreted by positive ion scavenging, S₁ excited cyclohexane molecule quenching and thermal H atoms scavenging. The low efficiency of all these three components of “protection” in α-radiolysis is attributed principally to the very high concentration of intermediates in the track/core compared to the relatively low concentration of benzene.The conclusions were also supported by comparison with the data obtained in cyclohexane-iodine systems.     

The yield of solvent excited states in the radiolysis of cyclohexane solutions

It is confirmed by pulse radiolysis that emitting solvent excited states are produced in the radiolysis of n-hexane, methylcyclohexane and cyclohexane. The emission is quenched by benzene and benzene emission appears. Applying stern - volmer kinetics to emissions from solvent, benzene and toluene in cyclohexane a very high energy transfer rate constant, viz., k = 2.8 × 10¹¹M⁻¹ sec⁻¹ is obtained. The yield of the excited state of cyclohexane is not greater than 0.3, and it is concluded that the major part of the excited states of other aromatics produced in cyclohexane solutions comes from ion neutralisation.     

Influence of diluent on radiolysis of amides in organic solution

The radiolytic behavior of N,N,N′,N′-tetraoctyldiglycolamide, N,N′-dimethyl-N,N′-dioctyl-2-(3′-oxapentadecyl)malonamide, and N,N-dioctylhexanamide in n-dodecane was investigated by irradiation with γ-rays and electron pulses. The results showed n-dodecane has a sensitization effect on the radiolysis of these amides, owing mainly to a charge transfer from radical cations of n-dodecane to the amide molecules in the primary process observed in pulse radiolysis. This result was supported by the difference in the ionization potentials between n-dodecane and these amides.     

SO2 prehydrolysis for high yield ethanol production from biomass

The advantages of the use of SO₂ in steam pretreatment are described. Two different large scale continuous reactors, the Stake and the Wenger, have been used for this purpose. Pine, aspen and corn stover were prehydrolysed by SO₂ in these reactors and hydrolysed by enzymes. The solution of hexoses and pentoses so obtained were fermented byPichia stipitis R, yielding 372, 346 and 388 L ethanol/tonne for the 3 feedstocks, respectively. When a mixed culture ofP. stipitis R, which is an excellent pentose fermenter, andBrettanomyces clausenii which is an excellent cellobiose fermenter, was used in a simultaneous saccharification-fermentation made with SO₂-prehydrolysed aspen, the yield rose to 384 L/tonne. These are higher yields than have been reported in the literature to date.     

Influence of drying method on the material properties of nanocellulose I: thermostability and crystallinity

The effect of drying method on selected material properties of nanocellulose was investigated. Samples of nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNC) were each subjected to four separate drying methods: air-drying, freeze-drying, spray-drying, and supercritical-drying. The thermal stability and crystallinity of the dried nanocellulose were evaluated using thermogravimetric analysis (TGA) and X-ray diffraction. Supercritical-drying produced NFCs with the least thermal stability and the lowest crystallinity index. Air-drying or spray-drying produced NFCs which were more thermally stable compared with freeze-dried NFCs. The CNCs dried by the three methods (air-drying, freeze-drying, and spray-drying) have similar onset temperature of thermal degradation. The different drying methods resulted in various char weight percentages at 600 °C for the dried NFCs or CNCs from TGA measurements. The dried NFCs are pure cellulose I while the dried CNCs consist of cellulose I and II. The calculated crystallinity indices differ with each drying method. The cellulose II content in CNCs changes as a function of drying method. For the application of nanocellulose in non polar thermoplastics, spray-dried products are recommended according to their higher thermal stability and higher crystallinity index.     

Application of catalysts for producing organic compounds from plant biomass

Experimental data on acid-base and oxidation-reduction catalysis in the conversion of wood carbohydrates and lignin to levoglucosenone, levulinic acid, aromatic aldehydes and other fine chemicals are presented and discussed.     

Effect of catalysts on the yield of products formed in biomass gasification

The effect of catalysts on the yield of products formed in thermal treatment of wood in the filtration combustion mode was experimentally studied. Natural zeolite of TsPS brand and K₂CO₃ were used as catalysts. The products were analyzed and the results were compared with those for noncatalytic systems. With the catalysts, the combustion temperature decreased by 100–200°C. The yield of liquid products formed in wood pyrolysis decreased with increasing amount of a catalyst in the mixture, and the appearance of unburned carbon on catalyst particles was also observed.     

Radical products from the radiolysis of 2,2,3,3-tetramethylbutane

Radiolysis of the pure title compound gives ESR signals only for neutral radical fragments, as estabhshed by Shiraishi et al.. and by Gerola et al. However, in the presence of a range of electron scavengers a novel species is detected by ESR spectroscopy which is tentatively identified as the parent cation, [Me₃C - CMe₃]⁺     

抽提物对生物质热裂解机理的影响研究

利用惰性溶剂从生物质中提取得到相应抽提物,在热重红外联用仪上研究了抽提物的热裂解行为,并探讨了其对生物质热裂解的影响。结果表明,因不同种类生物质中木质素结构单元中紫丁香基和愈创木基数量不同,从而导致抽提物成分存在差异,相应的热裂解产物分布也不一致。水曲柳抽提物因含有较多的酚类物质而在热解高温段生成了甲醇和甲烷。相比于原样,抽提残渣反应活化能增加,且主要产物析出时间提前,同时酸类物质和直链烷烃析出量减少,而水、CO2、CO和醛类物质的产量则有所增加。     

Influence of feed characteristics on the microwave-assisted pyrolysis used to produce syngas from biomass wastes

A series of biomass wastes (sewage sludges, coffee hulls and glycerol) were subjected to pyrolysis experiments under conventional and microwave heating. The influence of the initial characteristics of the raw materials upon syngas production was studied. Glycerol yielded the highest concentration of syngas, but the lowest H₂/CO ratio, whereas sewage sludges produced the lowest syngas production with the highest H₂/CO molar ratio. Coffee hull displayed intermediate values for both parameters. Microwave heating produced greater gas yields with elevated syngas content than conventional pyrolysis. Moreover, microwave pyrolysis always achieved the desired effect with temperature increase upon the pyrolysis products, whatever biomass material was employed. This could be due to the hot spot phenomenon, which only occurs under microwave heating. In addition, a comparison of the energy consumption of the traditional and microwave-assisted pyrolysis is also presented. Results point at microwave system as less time and energy consuming in comparison to conventional system.