Influence Of Pretreatment Temperature Research Articles

Evaluating performance of CrCl3-catalyzed ethanol pretreatment of poplar on cellulose conversion

As green and effective depolymerization processes, CrCl3 and CrCl3-catalyzed ethanol pretreatment were comprehensively investigated to improve cellulose conversion from pretreated residues in poplar in the present study. The influence of pretreatment temperature on delignification, structural characteristics of lignin, and the yield of glucose and ethanol was comparatively analyzed to emphasize the synergy effect of CrCl3 and ethanol solvent. Particularly, CrCl3-catalyzed ethanol pretreatment at 200 °C resulted in the pretreated substrates with >94% removal of hemicellulose and lignin, consequently reaching 88.88% and 56.11% yields of glucose and ethanol, respectively. Lignin's structural change was observed by Gel permeation chromatography and 2D nuclear magnetic resonance spectroscopy and its relationship with the efficiency of enzymatic hydrolysis and fermentation was determined. Results indicated that the increased pretreatment temperature enhanced the lignin depolymerization with smaller molecular weight, fewer β-O-4 linkages, and higher S/G ratio, especially in CrCl3-catalyzed ethanol pretreatment, which was positively associated with poplar cellulose conversion. In addition to offering a comprehensive illustration of the sugar/ethanol generation during CrCl3-catalyzed organosolv pretreatment, this work also provided theoretical support for biofuel and biochemical production from poplar.

Impact of hydrothermal pretreatment on anaerobic digestion efficiency for lignocellulosic biomass: Influence of pretreatment temperature on the formation of biomass-degrading byproducts

Anaerobic digestion (AD) of lignocellulosic biomass is appealing because of the abundance and ease of obtaining the biomass locally. However, the recalcitrance of lignocellulosic biomass presents an obstacle in the hydrolysis step of AD and lowers the process efficiency. In this study, sunflower, which is a model lignocellulosic biomass, was pretreated by thermal (hydrothermal pretreatment, HTP) and non-thermal (milling) methods; the methane yield and biodegradability of the pretreated biomass were determined using a series of batch tests. The thermal pretreatment method showed a significantly higher methane yield (213.87–289.47 mL g−1 VS) and biodegradability (43–63%) than those of the non-thermally pretreated biomass, and the optimum pretreatment effect was observed at an HTP temperature of 180 °C. However, at an HTP temperature exceeding 200 °C, the induced formation of 5-hydroxymethylfurfural and furfural significantly lowered the methane yield and biodegradability. This study revealed that the HTP temperature is closely related to the formation of lignocellulosic biomass-degrading byproducts, which potentially hinder the methanogenesis step in AD; severe HTP conditions may have the opposite effect on the AD performance of lignocellulosic biomass.

Evaluation of the Influence of Pre-treatment Temperature of Leucaena leucocephala in the Biosorption of 5G Blue Dye

Leucaena leucocephala is an invasive exotic tree plant, and because of these characteristics, it becomes an environmental problem. In this sense, the main objective of the present study was to evaluate the adsorption capacity of 5G blue dye, using dry L. leucocephala leaves under different temperatures. Drying kinetic, centesimal composition and micrographs after drying of the leaves were also evaluated. For drying, the Valcan model best described the process kinetics, presenting a correlation coefficient of 99.4% and an average error of 1.41%. For the centesimal composition, 3.9% of moisture, 7.5% of ash, 23.8% of crude protein, 29.5% of crude fiber, 3.9% of ethereal stratum and 31.4% of soluble carbohydrate were obtained. In the evaluation of the adsorptive capacity, the temperature of 40 °C was the one that produced the largest adsorbed amount of dye mass/leaf mass, 9.4 mg g -1 . The qualitative results obtained agreed with the one observed in the micrographs, so that the leaves of L. leucocephala have, therefore, industrial application with biosorbent. DOI: http://dx.doi.org/10.17807/orbital.v11i6.1266

Preparation of new photocatalytic materials using ion implantation method

The materials containing titanium supported on stainless steel foil 12X18N10T (AISI 321) were prepared by low temperature ion implantation method. Samples were investigated by means of XRD, SAXS, AFM, XPS and SEM methods. Any reflexes of titanium compounds were determined (XRD) but XPS data permit to identify the presence of titanium nitride, its oxide and oxynitride on surface samples. It was shown, that the synthesized samples are more active in visible range than under UV irradiation in photodegradation of benzene in aqueous solutions. Influence of pretreatment temperature on photoactivity of the samples is connected with nitrogen removal from synthesized composites.

Influence of pretreatment temperature on catalytic performance of rutile TiO2-supported ruthenium catalyst in CO2 methanation

Catalytic hydrogenation of CO2 to methane was investigated over Ru/rutile TiO2, focusing on the influence of the pretreatment temperature on the activity. Rutile TiO2 stabilized Ru nanoparticles even after pretreatment at 800°C; therefore it was possible to establish the structure–activity relationship without considering the particle size effect. The CO2 turnover frequency initially increased with increasing pretreatment temperature from 300 to 800°C, and reached a maximum value of 1.59s−1 on Ru/rutile TiO2 pretreated at 600°C; it decreased to 1.16s−1 for the sample pretreated at 800°C. The characterization results indicated that the activity depended on both the extent of encapsulation of Ru particles by TiOx layers and the number of hydroxyl groups on the TiOx surface. The mechanism of CO2 methanation was discussed based on in situ diffuse-reflectance infrared Fourier-transform spectroscopy results.

Comparison of dilute mineral and organic acid pretreatment for enzymatic hydrolysis of wheat straw

The efficiencies of fumaric, maleic, and sulfuric acid in wheat straw pretreatment were compared. As a measure for pretreatment efficiency, enzymatic digestibility of the lignocellulose was determined. Monomeric glucose and xylose concentrations were measured after subsequent enzymatic hydrolysis, as were levels of sugar degradation products furfural and hydroxymethylfurfural after pretreatment. The influence of pretreatment temperature and of wheat straw loading was studied. It is shown that, at 150 °C and 20–30% (w/w) dry wheat straw, the pretreatment with dilute fumaric or maleic acid can be a serious alternative to dilute sulfuric acid pretreatment.

Influence of Pretreatment Temperature on the Bimetallic Interactions in Pt-Re/Al2O3 Reforming Catalysts Studied by X-Ray Absorption Spectroscopy

The influence of pretreatment temperature on the metal function of a commercial Pt-Re/Al2O3 reforming catalyst was studied by X-ray absorption spectroscopy. By simultaneously examining the rhenium LIII and platinum LIII EXAFS data, the bimetallic interaction and the metal-support interaction can be distinguished from the overall spectrum. The results show that if the catalyst is dried in air at temperatures ≤500°C before reduction at 480°C, bimetallic particles of platinum and rhenium are formed. Drying at higher temperatures and in absence of air inhibits the transport of mobile (rhenium) species on the surface causing no intimate contact between the two metals. Platinum LIII EXAFS data show that the average particle size of the bimetallic particles on the alumina surface is less than 10 Å. The results from the rhenium LIII EXAFS analysis confirm that rhenium is not completely reduced to metallic rhenium after reduction, with a significant fraction of the rhenium present in low, positive oxidation states and in intimate contact with the support. The EXAFS data are consistent with a structural model of rhenium metal particles 1–3 nm wide with smaller platinum particles situated within or at the boundary of the rhenium particles, and that moderate heating in presence of air (i.e., moist) provides the best conditions for transport of mobile rhenium species on the surface, and hence alloy formation.

The adsorption of VO(acac)(2) on a mesoporous silica support by liquid phase and gas phase modification to prepare supported vanadium oxide catalysts

Supported vanadium oxide catalysts are prepared by adsorption and subsequent calcination of the vanadyl acetylacetonate complex on silica by liquid phase and gas phase modification. The influence of the pretreatment temperature and the effect of the solvent in the liquid phase are discussed. Two types of gas phase deposition processes are used: flow-type reactions and vacuum deposition. The bonding mechanism, the influence of pretreatment temperature of the support and the influence of the reaction temperature are investigated by FTIR, XRD, TGA and chemical analysis. After calcination the obtained vanadium oxide layer is characterized by XRD and UV-Vis diffuse reflectance spectroscopy. The gas phase modification enables the creation of well dispersed supported VOx catalysts. Loadings up to 1.4 mmol g-1 (7 wt% V) without the formation of a crystalline fraction can be achieved. The selective oxidation of methanol to formaldehyde is used as a probe reaction to assess the catalytic activity and selectivity of the catalysts. It is shown that not the concentration of vanadium species, but their surface configuration is the determining factor in catalytic reactions.

Studies on Anaerobic Digestion Mechanism: Influence of Pretreatment Temperature on Biodegradation of Waste Activated Sludge

The effect of thermal pretreatment on hydrolysis, acidogenesis and methanogenesis during anaerobic digestion of waste activated sludge (WAS) was investigated. Pretreatment temperature of WAS ranged from 60°C to 120°C and the holding times were 5, 10, 20, 30 and 60 minutes. WAS was fed into the laboratory-scale anaerobic digesters, after thermal pretreatment. The preliminary conversion step (such as death/lysis of cell and hydrolysis of WAS) was promoted through thermal pretreatment, and consequently efficiencies of acidogenic and methanogenic steps were also markedly enhanced. Thermal pretreatment at lower temperature resulted in a significant increase in methane generation and destruction of organic matter. At 60°C, when hydraulic retention time (HRT) was 8 days, an increase in approximately 52.1 % in methane generation (ml. l−1. d−1) and 26.6% in organic matter destruction was achieved (Series-I). In addition, HRT necessary for anaerobic digestion could be reduced by thermal pretreatment.

Synthesis and transformations of Ti-containing structures on the surface of silica gel

The influence of pretreatment temperature ( T 0) of the support (silica gel SchSK and KSS-4) and chemisorption temperature ( T s) on the composition of produced structures is examined by chemical analysis, gravimetric study, and IR-spectroscopy. During chemisorption at room temperature, TiCl 3 groups are formed (molar ratio is Cl/Ti ≈ 3). The rise of the temperature ( T s) from 25 to 600°C with a step of 100° is accompanied by a decrease in the Cl/Ti ratio to 1.67. This indicates the formation of TiCl 2 and TiCl surface groups. The content of Ti chemisorbed at 25°C is 0.67 mmol/g SiO 2, and it increases to 0.75 mmol/g SiO 2 at 200°C, and then it is reduced to 0.49 mmol/g SiO 2 at T s=400−600°C. Interactions between functional groups during the calcination process at temperatures above 100°C are supposed. This causes the release of TiCl 4 molecules in the gas phase and the increase of the number of (SiO) n TiCl 4− n ( n = 2, 3) groups. We suppose that the structure of Ti-oxochloride groups is the most important factor for the stability of the SiOTi bonds at the stage of vapour hydrolysis. One of the most important reasons for bond destruction is HCl formed during the treatment of chlorine-containing structures by water vapour.

Influence of pretreatment temperature on the selectivity of H,Na−MOR in xylene isomerization and disproportionation

Acidity of synthetic (NH4)0.98Na0.02−MOR samples pretreated at different temperatures has been characterized by differential adsorption heat distribution of ammonia. A fairly good correlation has been found between the number of acid sites of different strengths formed at increasing temperatures, and the catalytic activity and selectivity for xylene isomerization and disproportionation.

Influence of pretreatment temperature and pressure on the char reactivity during hydrogasification

The kinetics of hydrogasification of char may be influenced by the pyrolysis conditions, such as maximum carbonization temperature, pressure and type of gaseous atmosphere. To investigate these effects a German bituminous coal was pyrolysed at temperatures up to 900 °C under pressures between 0.2 and 4 MPa in He. The reactivity of the resulting char was measured in hydrogen (4 MPa, 900 °C) using a thermogravimetric apparatus.

The influence of pre-treatment temperature on the thermal sensitivity of a mouse tumour.

The response of tumours to hyperthermia was tested by giving graded heat treatments and assessing local control at 90 days. Mice were divided into three groups which were pre-treated for 3 days in ambient temperatures of 4, 21 or 35 degrees C. This enabled the mean tumour resting temperature to be varied by up to 11 degrees C, before subsequent heat treatment. For the heat treatments, the tumours were clamped in order to eliminate blood flow, resulting in uniform temperature distributions and hence more uniform thermal sensitivity. TCD50 values were used to construct Arrhenius plots. For all three pre-treatment temperatures, these plots demonstrated a factor of 1.6 increase in heating time per degree Celsius reduction in heating temperature. However, tumours kept in a 4 degrees C environment before treatment were more thermally sensitive than those kept in 21 degrees C conditions, while those in a 35 degrees C environment were more resistant. Pretreatment at 4 degrees C was equivalent to an increase of either 0.5 degree C in heating temperature or 28 per cent in heating time, compared with pre-treatment at 21 degrees C. Pre-treatment at 35 degrees C was equivalent to a reduction of either 0.6 degree C in heating temperature or 25 per cent in heating time. These data indicate that the pre-treatment tumour temperature is an important parameter, but the effect of heat treatment is more closely related to absolute heating temperature rather than to the increase in temperature above the normal resting level.

Efficacy, Persistence, and Phytotoxicity of Aldicarb Applied as a Pretransplant Treatment to Eggplant for Colorado Potato Beetle (Coleoptera: Chrysomelidae) Protection

Aldicarb was applied pretransplant to potted eggplant, Solanum melongena L., to determine the duration of Colorado potato beetle, Leptinotarsa decemlineata Say, control and residues in fruit relative to aldicarb application time and dose. The influence of pretreatment temperature on aldicarb phytotoxicity was also investigated. Eggplants, treated 1 week pretransplant with 0.4, 0.8, or 1.6 g of aldicarb 15G per 425 cm3 of potting soil, were protected from L. decemlineata for >3 weeks after transplanting; no residues of aldicarb were detected in first-harvest fruit. Foliage protection for this period would eliminate three to five of the foliar sprays currently being applied for early-season L. decemlineata control. Aldicarb phytotoxicity to eggplant was acclimation temperature dose dependent. Plants exposed to high acclimation temperatures (21–30°C) displayed significantly greater phytotoxicity when treated with 0.8 g of aldicarb compared with 0.4 g. Regardless of dose, little phytotoxicity was observed on plants exposed to low acclimation temperatures (13–18°C); thus, aldicarb phytotoxicity to eggplant can be eliminated by acclimating plants at temperatures ranging from 13 to 18°C for 1 week before treatment.