Production of Xylose from Meranti Wood Sawdust by Dilute Acid Hydrolysis

Xylitol production by bioconversion of xylose can be economically interesting if the raw material can be recovered from a cheap lignocellulosic biomass (LCB). Meranti wood sawdust (MWS) is a renewable and low-cost LCB that can be used as a promising and economic source of xylose, a starting raw material for the manufacture of several specialty chemicals, especially xylitol. This study aimed to optimize the hydrolysis process of MWS and to determine the influence of temperature, H₂SO₄ concentration, and residence time on xylose release and on by-product formation (glucose, arabinose, acetic acid, furfural, hydroxymethylfurfural (HMF), and lignin degradation products (LDPs)). Batch hydrolysis was conducted under various operating conditions, and response surface methodology was adopted to achieve the highest xylose yield. Xylose production was highly affected by temperature, acid concentration, and residence time. The optimum temperature, acid concentration, and time were determined to be 124 °C, 3.26 %, and 80 min, respectively. Under these optimum conditions, xylose yield and selectivity were attained at 90.6 % and 4.05 g/g, respectively.     

Pyrolysis of Eucalyptus wood in a fluidized-bed reactor

Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300–800 °C and 0.050–0.300 L min^?1 to determine the effects of operation temperature and N₂ flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min^?1), particle size (850 μm), and sweeping flow rate (0.200 L min^?1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N₂ gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg^?1, an empirical formula of CH_1.651O_0.105N_0.042S_0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m^?3, and a viscosity of 61.24 mm² s^?1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements.     

Thermodynamic properties of crystalline phosphate Ba0.5Zr2(PO4)3 over the temperature range from T → 0 to 610 K

The temperature dependence of the heat capacity of crystalline barium zirconium phosphate C _p ^o  = f(T) was measured over the temperature range 6–612 K. The experimental data obtained were used to calculate the standard thermodynamic functions C _p ^o (T), H°(T) ? H°(0), S°(T), G°(T) ? H°(0) over the temperature range from T → 0 to 610 K and standard entropy of formation at 298.15 K. The data on the low-temperature (6 ≤ T/K ≤ 50) heat capacity were used to determine the fractal dimension of Ba_0.5Zr₂(PO₄)₃. Conclusions concerning the topology of the structure of phosphate were drawn. Thermodynamic properties of M_0.5Zr₂(PO₄)₃ (M = Ca, Sr, Ba) were compared.     

Catalytic reforming of tar using corncob char and char-supported potassium catalysts

This work aims to investigate the importance of biomass char and the metal oxides in the ash in tar cracking during the volatile–char interactions. Experiments were carried out in a two-stage fixed reactor, and corncob, one typical agricultural biomass rich in potassium, was chosen as raw material. Results showed that char and char-supported potassium catalysts have good activity for tar elimination due to the good absorbability of char and catalytic property of potassium. In particular, tar conversion efficiency can reach 95.8% by using 1.5 K-char catalyst at 700 °C. The reforming reactions can be significantly enhanced during the volatile–char interactions in the presence of char and char-supported potassium catalysts. As a result, the syngas yield increased significantly with increasing temperature and supported K⁺, particularly the combustible gases including H₂, CO and CH₄. Physical and chemical structure of char changed due to reforming reactions related to the carbon, while the content of potassium was almost unchanged.     

Pyrolysis of pine needles: effects of process parameters on products yield and analysis of products

Pyrolysis of pine needles was carried out in a semi-batch reactor. The effects of pyrolysis parameters such as temperature (350–650 °C), heating rate (10 and 50 °C min^?1), nitrogen flow rate (50–200 cm³ min^?1) and biomass particle size (0.25–1.7 mm) were examined on products yield. Maximum bio-oil yield of 43.76% was obtained at pyrolysis temperature of 550 °C with a heating rate of 50 °C min^?1, nitrogen flow rate of 100 cm³ min^?1 for biomass particle size of 0.6 < d _p < 1 mm. The characterization of pyrolysis products (bio-oil, bio-char) has been made through different instrumental methods like Fourier transform infrared spectroscopy, gas chromatography–mass spectrometry, nuclear magnetic resonance spectroscopy (¹H NMR), X-ray powder diffraction, field emission scanning electron microscope and Brunauer–Emmett–Teller surface area analysis. The empirical formula of the bio-oil and bio-char was found as CH_1.47O_0.36N_0.005 and CH_0.56O_0.28N_0.013 with heating value of 26.25 and 25.50 MJ kg^?1, respectively. Results show that bio-oil can be potentially valuable as a renewable fuel after upgrading and can be used as a feedstock for valuable chemicals production. The properties of bio-char reveal that it can be used as solid fuels, as a cheap adsorbent and as a feedstock for activated carbon production.     

Carbon Dioxide Destruction with Methane Reforming by a Novel Plasma-Catalytic Converter

A novel plasma-catalyst converter (NPCC) was engineered in applying the carbon capture utilization technology for the destruction of carbon dioxide (CO₂), which is a cause of global warming and is generated from the combustion of fossil fuels. The NPCC has an orifice-type baffle to improve an amount of gas feed with the higher CO₂ destruction for a stationary point sources application . To examine its ability for the CO₂ destruction, the performance analysis was conducted on the effects of methane additive, nozzle injection velocity, total gas feed, and catalyst type. The product gas from the NPCC was combustible components like CO, H₂, CH₄, THCs. The CO₂ destruction and the CH₄ conversion at a 1.29 CH₄/CO₂ ratio were 37 and 47 %, respectively, and the energy decomposition efficiency was 0.0036 L/min W. The nickel oxide catalyst among other catalysts showed the most effectiveness for the CO₂ destruction and CH₄ conversion at a lower temperature. The carbon-black produced without the catalytic bed has carbon nanoparticles with diverse shapes, such as spherical carbon particles and carbon nanotubes; and its high conductivity and specific surface area were suitable for special electronic materials, fuel cells, and nanocomponents.     

Acid Hydrolysis of Hemicellulose in Green Liquor Pre-Pulping Extract of Mixed Northern Hardwoods

Forest biomass is a promising resource for future biofuels and bioproducts. Pre-pulping extraction of hemicellulose by alkaline (Green Liquor) pretreatment produces a neutral-pH extract containing hemicellulose-derived oligomers. A near-term option for use of this extract is to hydrolyze the oligomers to fermentable monomer sugars. Chips of mixed northern hardwoods were cooked in a rocking digester at 160 °C for 110 min in Green Liquor at a concentration of 3% Na₂O equivalent salts on dry wood. The mass of wood extracted into the Green Liquor extract was approximately 11.4% of the debarked wood mass, which resulted in a dilute solution of oligomeric hemicelluloses sugars. The concentration of the extract was increased through partial evaporation prior to hydrolysis. Dilute sulfuric acid hydrolysis was applied at conditions ranging from 100 to 160 °C, 2% to 6% (w/v) H₂SO₄, and 2- to 258-min residence time. The maximum fermentable sugar concentration achieved from evaporated extract was 10.7 g/L, representing 90.7% of the maximum possible yield. Application of the biomass pretreatment severity function to the hydrolysis results proved to offer a relatively poor prediction of temperature and reaction time interaction. The combined severity function, which incorporates reaction time, temperature, and acid concentration, did prove to provide a useful means of trading off the combined effects of these three variables on total sugar yields.     

Thermodynamic properties of crystalline magnesium zirconium phosphate

Heat capacity $ C_{\text{p}}^{^\circ } $ (T) of crystalline magnesium zirconium phosphate was measured between 6 and 815 K. The experimental data obtained were used to calculate the standard thermodynamic functions $ C_{\text{p}}^{^\circ } $ (T), H°(T) ? H°(0), S°(T), G°(T) ? H°(0) over the temperature ranging from T → 0 to 810 K and standard entropy of formation at 298.15 K. The fractal dimension of Mg_0.5Zr₂(PO₄)₃ was calculated from experimental data on the low-temperature (6 ≤ T/K ≤ 50) heat capacity, and the topology of the phosphate’s structure was estimated. Thermodynamic properties of structurally related phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) were compared.     

Synthesis of aromatic amine curing agent containing non-coplanar rigid moieties and its curing kinetics with epoxy resin

A kind of aromatic diamine, 4′, 4″-(2, 2-diphenylethene-1, 1-diyl)dibiphenyl-4-amine (TPEDA), was successfully synthesized via Suzuki coupling reaction. The TPEDA containing nonplanar rigid moieties can be used as epoxy resins curing agent to improve the complex properties of cured composites. The curing kinetics during thermal processing of E51/TPEDA system was investigated by nonisothermal differential scanning calorimeter. The average activation energy (E _α), pre-exponential factor (lnA), and reaction order (n) calculated from the Kissinger, the Ozawa, the Friedman and the Flynn–Wall–Ozawa methods were 55.8 kJ mol^?1, 9.4 s^?1 and 1.1, respectively. By the aid of estimated kinetic parameters, the predicted heat generation vs temperature curves fit well with the experimental data, which supported the validity of the estimated parameters and the applicability of the analysis method used in this work. By the introduction of nonplanar rigid moieties, the cured epoxy resins with TPEDA exhibited a higher glass transition temperature (T _g = 258 °C), good thermal stability (≈395 °C at 10 % mass-loss), and high char yield (36.6 % at 700 °C under nitrogen) compared with conventional curing agents.     

Hydrogen production by glycerol reforming in supercritical water over Ni/MgO-ZrO2 catalyst

Nano ZrO₂ and MgO-ZrO₂ were prepared by a self-assembly route and were employed as the support for Ni catalysts used in hydrogen production from glycerol reforming in supercritical water (SCW). The reforming experiments were conducted in a tubular fixed-bed flow reactor over a temperature range of 600–800 °C. The influences of process variables such as temperature, contact time, and water to glycerol ratio on hydrogen yield were investigated and the catalysts were charactered by ICP, BET, XRD and SEM. The results showed that high hydrogen yield was obtained from glycerol by reforming in supercritical water over the Ni/MgO-ZrO₂ catalysts in a short contact time. The MgO in the catalyst showed significant promotion effect for hydrogen production likely due to the formation of the alkaline active site. Even when the glycerol feed concentration was up to 45 wt%, glycerol was completely gasified and transfered to the gas products containing hydrogen, carbon dioxide, and methane along with small amounts of carbon monoxide. At a diluted feed concentration of 5 wt%, near theoretical yield of 7 mole of H₂/mol of glycerol could be obtained.     

Catalytic removal of soot particles over MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> catalysts prepared by the auto-combustion method

Soot removal for exhaust gas from diesel engine has been addressed due to the more stringent legislation and environmental concerns. MnCo₂O₄ catalysts were systematically prepared using glucose as a fuel via the auto-combustion method and applied for soot removal. The as-prepared samples were characterized by X-ray diffraction (XRD), O₂-temperature-programmed oxidation (TPO) reaction and H₂-temperature-programmed reduction reaction (H₂-TPR). The catalytic activities for soot combustion were evaluated by micro activity test (MAT) with a tight contact mode between soot and catalysts. Compared with catalysts prepared by the solid state method without glucose, auto-combustion method in the presence of glucose can decrease the synthetic temperature, avoiding high temperature treatment and sintering. The catalysts prepared with glucose could catalyze soot oxidation effectively and the derived values of T₁₀, T₅₀, and T₉₀ were 326, 408, and 468 °C in a tight contact mode, respectively, showing a significant drop of T₁₀, T₅₀, and T₉₀ by 156, 177, and 178 °C for non-catalytic reaction.     

Hydrogen production by methanol steam reforming on a cordierite monolith reactor coated with Cu–Ni/LaZnAlO<Subscript>4</Subscript> and Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The performance of Cu–Ni/LaZnAlO₄ and Cu–Ni/γ-Al₂O₃ catalysts in the methanol reforming process in a monolith reactor in the temperature range of 200–350 °C, feed flow rate of WHSV = 20.8 h^?1 and atmospheric pressure has been investigated. In order to perform a more thorough investigation, surface area, morphology and crystalline structure of the synthetic catalysts have been studied using BET, FE-SEM, TPR, FT-IR, TEM, TGA and XRD analyses. The results have shown that Cu–Ni/LaZnAlO₄ catalyst synthesized by combustion reaction method under ultrasound irradiation has a very high efficiency and catalytic activity, low reduction temperature, high mechanical resistance and large pore sizes. The latter causes a higher percentage of active metal impregnation and better distribution on the support, greater resistance against sintering and maintenance of catalyst inertness at temperatures over 1000 °C, in comparison with conventional catalysts such as Cu–Ni/γ-Al₂O₃. This make its substitution for currently used catalysts affordable.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

CO<Subscript>2</Subscript> Biofixation and Growth Kinetics of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and <Emphasis Type="Italic">Nannochloropsis gaditana</Emphasis>

CO₂ biofixation was investigated using tubular bioreactors (15 and 1.5 l) either in the presence of green algae Chlorella vulgaris or Nannochloropsis gaditana. The cultivation was carried out in the following conditions: temperature of 25 °C, inlet-CO₂ of 4 and 8 vol%, and artificial light enhancing photosynthesis. Higher biofixation were observed in 8 vol% CO₂ concentration for both microalgae cultures than in 4 vol%. Characteristic process parameters such as productivity, CO₂ fixation, and kinetic rate coefficient were determined and discussed. Simplified and advanced methods for determination of CO₂ fixation were compared. In a simplified method, it is assumed that 1 kg of produced biomass equals 1.88 kg recycled CO₂. Advance method is based on empirical results of the present study (formula with carbon content in biomass). It was observed that application of the simplified method can generate large errors, especially if the biomass contains a relatively low amount of carbon. N. gaditana is the recommended species for CO₂ removal due to a high biofixation rate—more than 1.7 g/l/day. On day 10 of cultivation, the cell concentration was more than 1.7?×?10⁷ cells/ml. In the case of C. vulgaris, the maximal biofixation rate and cell concentration did not exceed 1.4 g/l/day and 1.3?×?10⁷ cells/ml, respectively.     

Steam pre-reforming of natural gas over nanostructured Ni/12CaO–7Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for hydrogen production: effect of support preparation method

Calcium aluminate (12CaO–7Al₂O₃) powder was synthesized using three methods, viz. Pechini, coprecipitation, and a new novel facile decomposition route starting from activated alumina and calcium nitrate precursors, then used as a support to prepare a series of 31 wt%Ni/12CaO–7Al₂O₃ catalysts by deposition–precipitation method. The resultant catalysts were tested in steam pre-reforming of natural gas at 400–550 °C, low steam-to-carbon (S/C) molar ratio of 1.5, and atmospheric pressure. The obtained samples were characterized by Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), hydrogen chemisorption, and CO₂–temperature-programmed desorption (TPD). Experimental results showed that the basicity and morphology of the supports depended significantly on the synthesis method. Calcium aluminate synthesized using the new decomposition procedure showed surface area of 6.23 m² g^?1, while the surface area of those prepared by the Pechini and coprecipitation method were 1.38 and 3.76 m² g^?1, respectively. The catalytic properties of the 31 wt%Ni/12CaO–7Al₂O₃ catalysts were strongly influenced by the support preparation approach. The highest specific surface area (about 230 m² g^?1), smallest Ni particle size (8.86 nm), and highest nickel dispersion (7.48%) were observed for the catalyst whose support was synthesized by the decomposition method. Even at high gas hourly space velocity (GHSV) of 2 × 10⁵ mL \({\text{g}}^{ - 1}_{\text{catalyst}}\) h^?1, this catalyst exhibited around 100% C₂H₆ and C₃H₈ conversion at temperature above 500 °C. High catalytic stability during 60 h time on-stream was also shown. The TPO profiles of the spent catalyst demonstrated high resistance to carbon formation.     

Hydrogenolysis of dimethyl disulfide in the presence of bimetallic sulfide catalysts

The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160–400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S-S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C-S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al₂O₃ catalyst in hydrogenolysis at the S-S and C-S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al₂O₃ catalyst is twice as active as the Ni/Al₂O₃ + Mo/Al₂O₃ or the cobalt-molybdenum bimetallic catalyst.     

Catalytic conversion of raw <Emphasis Type="Italic">Dioscorea composita</Emphasis> biomass to 5-hydroxymethylfurfural using a combination of metal chlorides in <Emphasis Type="Italic">N,N</Emphasis>-dimethylacetamide solvent containing lithium chloride

We synthesized 5-hydroxymethylfurfural (HMF) from carbohydrates using metal chloride catalysts. A 33.2 % yield of HMF was obtained from raw Dioscorea composita biomass with high starch by using a catalyst system composed of CrCl₃·6H₂O and LaCl₃·6H₂O at 120 °C for 4 h in N,N-dimethylacetamide containing lithium chloride. The catalyst system is also cost-effective for the conversion of soluble starch into HMF. In addition, levulinic acid was not formed in the reactions.     

A kinetic and statistical model for carbon deposition on Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in the steam methane reforming

An experimental and statistical study was performed for the carbon deposition on Ni/Al₂O₃ catalyst in the methane steam reforming process. Carbon deposition plays a significant role in the catalyst deactivation. Thus, applying a statistical model and a kinetic rate for carbon deposition is so valuable. The central composite design (CCD) was used for the modeling of the carbon deposition process. The statistical analysis of model, as obtained from the CCD method, revealed that a polynomial equation with the F-value = 456.94, the p value < 0.0001, and the R ² = 0.9919, could appropriately predict the experimental data. Based on the established models, an increase in steam to methane ratio (S/C) caused carbon deposition sharply decreased. As pressure increased from 1.81 to 4.19 bar, carbon deposition slightly increased. When temperature varied from 540 to 600 °C, whisker carbon was produced and its activity increased with temperature. As temperature exceeded 600 °C, carbon deposition slightly increased that can be attributed to formation of pyrolytic carbon. The minimum of carbon deposition was occurred in low pressure, high S/C and at 600 °C. So, the kinetic rate of carbon deposition was suggested in these conditions using generalized reduced gradient nonlinear method. The proposed kinetic rate of methane decomposition reaction can accurately predict the experimental rate data.     

Thermogravimetric analysis of co-combustion of biomass and biochar

The co-combustion of biomass and biochar was investigated by thermogravimetric analysis. Several thermal parameters and mean reactivity index (R _M) for different blends were used to evaluate co-combustion features. As the biomass content increased from 30 to 90 mass%, volatile releasing temperature (T _v), burnout temperature (T _b), and the temperature at the maximal peak (T _max) generally reduced, while average mass loss rates (R _a) and R _M increased, the maximum mass loss rate (R _max) initially decreased and then increased. Results showed that biochar additions enhanced biomass fuel reactivity over weighted average in main combustion region. Besides, blends with 10–30 mass% of biochar behaved better than those with higher biochar ratio. Synergy exists between the two components and better combustibility is feasible by co-firing biochar with biomass.     

Non-isothermal crystallization kinetics of a Si–Ca–P–Mg bioactive glass

In this work, the crystallization process of a SiO₂–3CaO·P₂O₅–MgO glass was studied by non-isothermal measurements using differential thermal analysis carried out at various heating rates. X-ray diffraction at room and high temperature was used to identify and follow the evolution of crystalline phases with temperature. The activation energy associated with glass transition, (E _g), the activation energy for the crystallization of the primary crystalline phase (E _c), and the Avrami exponent (n) were determined under non-isothermal conditions using different equations, namely from Kissinger, Matusita & Sakka, and Osawa. A complex crystallization process was observed with associated activation energies reflecting the change of behavior during in situ crystal precipitation. It was found that the crystallization process was affected by the fraction of crystallization, (x), giving rise to decreasing activation energy values, E _c(x), with the increase of x. Values ranging from about 580 kJ mol^?1 for the lower crystallized volume fraction to about 480 kJ mol^?1 for volume fractions higher than 80 % were found. The Avrami exponents, calculated for the crystallization process at a constant heating rate of 10 °C min^?1, increased with the crystallized fraction, from 1.6 to 2, indicating that the number of nucleant sites is temperature dependent and that crystals grow as near needle-like structures.