Solubility of anthraquinone in alkaline solutions of sodium sulfide

The reduction of anthraquinone (AQ) with alkaline solutions of sodium sulfide, which takes place in the kraft pulping process, has been studied. The reduction product is the disodium salt of 9,10-dihydroxyanthracene (Na₂AQ). A 2⁴ factorial design has been used to check the effects of sodium sulfide, anthraquinone and sodium hydroxide concentrations and temperature on the reaction. From statistical results, it has been concluded that the concentration of reducing agent has a limiting effect on Na₂AQ yield, while the temperature has a negative effect because it favours the oxidation of sodium sulfide in alkaline solutions. Therefore, a maximum reduction of quinone can be obtained with the highest concentration of reagents and low temperatures.     

Ethanol‐based pulping from Cynara cardunculus L

A non‐conventional pulping process based on the delignification of cardoon (Cynara cardunculus L) in ethanol–water mixtures has been studied to evaluate its pulping potential and to establish the optimum pulping conditions for this lignocellulosic material. The variables analyzed were the concentration of ethanol in the cooking liquor, the pulping time and temperature. Variable optimization was performed by a central composite design. High viscosity, low kappa number and acceptable screened yield were used as pulp quality criteria to optimize cooking conditions. Pulps having low kappa numbers and viscosities greater than 900 cm³/g^?1 were obtained. The total pulp yield was low compared with wood pulping due to the high contents of extractives and ash in cardoon. The amount of rejects in the pulp is of importance, especially for pulps with a high kappa number. The most suitable pulping conditions were 188 °C, 135 min and 50% (w/w) ethanol concentration. In these conditions the kappa number of the pulp was around 26, the pulp viscosity greater than 1100 cm³ g^?1 and a screened pulp yield of about 31% was obtained. Copyright © 2005 Society of Chemical Industry     

Preparation and characterization of 4-vinyl pyridine-grafted SBS triblock copolymer

Study on the graft of 4-vinyl pyridine to styrene-butadiene-styrene triblock copolymer by solution polymerization shows that the catalyst concentration, temperature, and reaction time are the major influencing factors. Graft efficiency increases with temperature and time but levels off when temperature is higher than 65°C. Increasing concentration of catalyst also promotes graft, but when it is higher than 1.0 × 10^?2 M, the reaction system begins to gel. A cast film of the graft copolymer was dried, cross-linked with S₂Cl₂ in nitromethane solution, sulfonated, and chloromethylated. The water content of the membrane is 13.5%. Its anionic and cationic exchange capacities are 0.066 mEq per dry gram and 0.273 mEq per dry gram, respectively. The anionic-cationic capacity ratio is thus 0.26. The nitrogen content of the graft copolymers was determined with a CHN elemental analyzer, and qualitative analysis was carried out with infrared spectroscopy. Transmitting electronic microscopy was used to study the morphology and feasibility of preparing a charged mosaic membrane for piezodialysis.     

Infrared Absorption Spectra of Cellulose Pulps of Palm Tree

Palm leaves are used for the production of different cellulose pulps; their properties are investigated, the resulting pulps were bleached by a multistage process, the effects of the addition of solvent during the pulping process on the chemical structure of the pulps are discussed. The strength properties of the paper which is produced from unbleached and bleached pulps increased with increasing cellulose percentage and decreasing lignin content in the pulp. Infrared absorption spectra were recorded for different unbleached and bleached pulp in the frequency range 200–4000 cm^-1 by using the alkali halide disk technique; the factors which affect the experimental technique were calibrated through these studies. The structural units within pulping yield (holocellulose, hemicellulose, cellulose, lignin, and ash) were interpreted within the pulp network structure by the infrared absorption spectra, where different samples of unbleached, bleached soda, and kraft pulps were also elucidated by IR spectra, after preheating at different temperatures and with using different ratios of organic solvents. The addition of organic solvents decreased or increased the crystallinity indices, depending on the type of solvent and the pulping temperature. It was also found that, at the same pulping temperature (155°C) and with the same percent of organic solvents in the pulping liquor, the asymmetry indices also the mean hydrogen bonding strength (A _OH/A_CH) of the unbleached soda pulps (organosolv or nonorganosolv pulping) were less than that of unbleached kraft pulps, except for the pulps obtained by pulping with dioxan at 155°C. The mean hydrogen bond strength of the bleached pulps decreased or increased, depending on the type solvent used and the pulping temperature.     

Polyesterification and isomerization of maleic anhydride and 1,6-hexane diol as studied by 1H and 13C n.m.r.

The polyesterification and isomerization reaction of 1,6-hexane diol and maleic anydride in a melt without catalyst was studied by ¹³C and ¹H n.m.r. spectroscopy. The structure and concentration of oligoester species during the polyesterification and isomerization were determined depending on the reaction temperature and time. According to the number and configuration of repeating units determined from ¹H n.m.r. spectra kinetics of both reactions were also considered. The degree of isomerization is continuously increasing in the investigated reaction range.     

Dissolving pulps from Egyptian bagasse. II. Low temperature cooking

Bagasse was pulped by the prehydrolysis-soda process. Increasing the concentration during prehydrolysis or pulping had a favourable effect on pulp properties. Further improvement in these properties was attained when the increase in concentration was accompanied by lowering the temperature. The effects of increasing the concentration and lowering the temperature of prehydrolysis and pulping were compared.     

Oxidation of cyclohexanone to adipic acid with a cobalt acetate/oxygen/acetic acid system

The liquid phase oxidation of cyclohexanone to adipic acid at 378 K using oxygen as the oxidising agent and cobalt acetate as the catalyst in an acetic acid medium was investigated both at atmospheric pressure and at a pressure of 0.5MN m⁻². The effects of catalyst concentration, solvent concentration and partial pressure of oxygen, were studied at a constant stirrer speed of 535 rev min⁻¹. Increasing the solvent concentration and decreasing the catalyst concentration (up to 0.113×10⁻³ kmol m⁻³) had positive effects on the overall first order reaction rate constant. It was also found to vary linearly with gas flow rate.     

Kinetics of oxidation of pseudocumene in the vapor phase

The kinetics of pseudocumene oxidation in the vapor phase with tin vanadate as catalyst have been studied over the following ranges of the variables: Oxygen concentration, 0.909 to 2.857 mole/m³; pseudocumene concentration, 0.071 to 0.125 mole/m³; temperature, 260 to 320°C; space time, 22.5 to 90 × 10⁴ g. catalyst/mole sec. Oxidation-reduction models have been found to describe the kinetics adequately. The mechanism is found to remain the same throughout the temperature range covered.     

Polymerization of propylene using MgCl2 (ethoxide type)/TiCl4/diether heterogeneous Ziegler–Natta catalyst

Heterogeneous Ziegler–Natta catalyst of MgCl₂ (ethoxide type)/TiCl₄/diether was prepared. 2,2‐Diisobutyl‐1,3‐dimethoxy propane (DiBDMP), diether, was used as internal donor. Slurry polymerization of propylene was carried out using the catalyst in dry heptane while triethylaluminium (TEA) was used as co‐catalyst. The co‐catalyst effects, such as catalyst molar ratio, polymerization temperature, H₂ pressure, external donor, triisobutylaluminium (TiBA) and monomer pressure, on the activity of the catalyst and isotacticity index (II) of the polymers obtained were studied. Rate of polymerization versus polymerization time is of a decay type with no acceleration period. There are an optimum Al/Ti molar ratio and temperature to obtain the highest activity of the catalyst. The maximum activity was obtained at 60 °C. Increasing the monomer pressure to 1 010 000 Pa linearly increased the activity of the catalyst. Addition of hydrogen to 151 500 Pa pressure increased activity of the catalyst from 2.25 to 5.45 kg polypropylene (PP) (g cat)^?1 h^?1 using 505 000 Pa pressure of monomer. The II decreased with increasing Al/Ti ratio, monomer pressure, hydrogen pressure and increased with increasing temperature to 60 °C, following with decrease as the temperature increases. Productivity of 11.55 kg (PP) (g cat)^?1 h^?1 was obtained at 1 010 000 Pa pressure of monomer and temperature of 60 °C. Addition of methyl p‐toluate (MPT) and dimethoxymethyl cyclohexyl silane (DMMCHS) as external donors decreased the activity of the catalyst sharply, while the II slightly increased. Some studies of the catalyst structure and morphology of the polymer were carried out using FTIR, X‐ray fluorescence, scanning electron microscopy and Brunauer–Emmett–Teller techniques. Copyright © 2005 Society of Chemical Industry     

Study on SO42−/ZrO2-MoO3 in the integrative transformation of cottonseed oil deodorizing distillate

With the integrative transformation of non α-tocopherols, glycerides, free fatty acids, and methyl alcohol in cottonseed oil deodorizing distillate as the target reaction, we prepared highly catalytic SO₄^2?/ZrO₂-MoO₃ solid acid catalyst by precipitation–wet impregnation. The optimal conditions for catalyst preparation were then determined by varying sulfuric acid concentration, MoO₃ loading factor, calcination temperature, and calcination time. The structure of SO₄^2?/ZrO₂-MoO₃ solid acid catalyst was then examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurements, scanning electron microscopy, and other methods. Results show that the MoO₃ loading factor (percentage weight ratio of MoO₃ to ZrO₂), impregnation concentration of sulfuric acid, and calcination temperature were the most important factors that influenced catalytic activity. The optimal conditions for catalyst preparation were an MoO₃ loading factor of 20%, a sulfuric acid impregnation concentration of 0.75 mol/L, a calcination temperature of 550 °C, and a calcination time of 6 h. The obtained catalyst exhibited the highest catalytic activity under these conditions.     

Effect of Alkaline Hemicellulose Extraction on Kraft Pulp Fibers from Eucalyptus Grandis

Abstract

The alkaline extraction of hemicelluloses from hardwoods prior to pulping, for further conversion to value-added products, seems to be a promising pathway for paper mills to increase profit and improve sustainability. However, the amount of hemicellulose extracted will be limited by the requirement to maintain pulp quality and pulp yield in comparison to existing pulping processes. The effects of NaOH concentration, temperature, and time on hemicellulose extraction of Eucalyptus grandis were studied using a statistical experimental design. Extracted wood chips were subjected to kraft pulping to evaluate the effect of the extraction on cooking chemicals, pulp quality, and handsheet paper strengths. The selective xylan recovery (12.4% dry mass) from E. grandis combined with low-cooking, active alkali charge, and less cooking time advantaged the xylan extraction and subsequent modified kraft pulping process under the studied conditions. Pulp viscosity, breaking strength, and tensile index of handsheets were slightly improved.     

Chemical nature of coal hydrogenation oils part I. The effect of catalysts

Hydrogenation of the same coal was carried out with no catalyst and with 1, 5, 10 and 15% stannous, zinc and ferrous chloride catalysts. The oils (hexane soluble portion) were fractionated by silica gel chromatography and by extraction with acid and base. The oils and fractions derived from them were investigated by ¹³C- and ¹H-nuclear magnetic resonance, infrared, ultraviolet, fluorescence and phosphorescence spectroscopy. Increasing the amount of catalyst used decreased the percentage of polar compounds in the oil while the “gross” hydrocarbon structure showed little change with catalyst concentration. The decrease in the percentage of polar compounds in the oil resulted in a reduction in the viscosity of the oil due to decreased hydrogen bonding, which was shown by infrared and nuclear magnetic resonance studies.     

Application of response surface methodology for optimization of biodiesel production by transesterification of soybean oil with ethanol

In this paper, the transesterification of soybean oil with ethanol is studied. The transesterification process can be affected by differing parameters. The biodiesel production process was optimized by the application of factorial design 2⁴ and response surface methodology. The combined effects of temperature, catalyst concentration, reaction time and molar ratio of alcohol in relation to oil were investigated and optimized using response surface methodology. Optimum conditions for the production of ethyl esters were the following: mild temperature at 56.7 °C, reaction time in 80 min, molar ratio at 9:1 and catalyst concentration of 1.3 M.     

Statistical optimization of process conditions for photocatalytic degradation of phenol with immobilization of nano TiO<Subscript>2</Subscript> on perlite granules

Response surface methodology (RSM) using D-optimal design was applied to optimization of photocatalytic degradation of phenol by new composite nano-catalyst (TiO₂/Perlite). Effects of seven factors (initial pH, initial phenol concentration, reaction temperature, UV irradiation time, UV light intensity, catalyst calcination temperature, and dosage of TiO₂/perlite) on phenol conversion efficiency were studied and optimized by using the statistical software MODDE 8.02. On statistical analysis of the results from the experimental studies, the optimum process conditions were as follows: initial pH, 10.7; initial phenol concentration, 0.5 mM; reaction temperature, 27 °C; UV irradiation time, 6.5 h; UV light intensity, 250 W; catalyst calcination temperature, 600 °C; and TiO₂/perlite dosage, 6 g/L. Analysis of variance (ANOVA) showed a high coefficient of determination (R²) of 91.8%.     

Sequential Treatment of Tequila Industry Vinasses by Biopolymer-based Coagulation/Flocculation and Catalytic Ozonation

This article describes the study of the treatment of tequila industry vinasses based on the sequential application of coagulation-flocculation and heterogeneous catalytic ozonation. Coagulation-flocculation treatment used biopolymers to reduce the nondissolved organic matter and to reduce the degree of color units in effluent. Among six different substances, chitosan was the most efficient biopolymer to remove the highest chemical organic demand (COD) concentration (84.0%). The response surface technique was used to obtain the best attainable operation conditions of coagulation-flocculation process. The initial organic matter concentration, the reaction period and biopolymer concentration were selected as the independent variables. Two levels of analysis were performed: optimally and sensibility. The best reaction conditions were 3.23 × 10⁴ mg L^?1 of initial COD, 125.4 mg L^?1 of chitosan concentration, and 60.0 min of reaction. Ozonation process was performed on the effluent of coagulation-flocculation treatment. A batch reaction with 30 mg L^?1 of ozone in gaseous phase and a flow of 0.1 L min^?1 was implemented. Nickel oxide (100 mg L^?1) was used as the catalyst of the ozonation reaction. Twice larger COD concentration removal was obtained when the catalyst participated in the reaction compared to the so-called conventional ozonation (12.00% in conventional case vs 26.70% in catalyst presence). An ultraviolet-visible (UV-Vis) spectroscopy study was conducted to obtain a preliminary evaluation of organic compounds removal by effect of the sequential method proposed in this study. A significant total organics removal from the tequila industry wastewater (measured as the integral of UV-Vis spectrum) of 398.6 conditional units was obtained when the conventional ozonation was used after coagulation-flocculation, but that value was increased up to 1609.12 conditional units when the catalyst was inserted into the reaction.     

Kinetics of 2,2,6,6‐Tetramethylpiperidine Oxidation over Sn2+ on Ion Exchange Resin

The oxidation of 2,2,6,6‐tetramethylpiperidine (TEMP) over Sn²⁺ on ion exchange resin is carried out in a batch reactor. The influence of the reactant concentrations, reaction temperature and catalyst amount is investigated. Within the temperature range studied, 303–323 K, the reaction follows the second order kinetic equation ‐r_TEMP = kC_TEMPC_H2O2, with reaction rate constant k = 2.2 × 10⁷exp (‐51200/RT) L/mol h. We propose a reaction mechanism different from that for catalyzation by tungstate. The catalyst likely forms complexes with hydroxyl radicals, keeping their concentration steady. At the same time, the catalyst also decreases the decomposition of hydrogen peroxide caused by high temperatures and the reactant 2,2,6,6‐tetramethylpiperidine itself.     

A solid-state 13C nuclear magnetic resonance study of cured,unsaturated polyester resins

The styrene sequence distributions and amount of reacted fumarate units in cured, unsaturated polyester resins were studied by solid-state ¹³C nuclear magnetic resonance. Increasing the styrene content and molar ratio of styrene to the double bonds in the polyester chain increased the amount of diad and n-ad sequences and decreased the amount of monad sequences. At the same time, the amount of reacted fumarate units increased. The glass transition temperature was almost constant for resins with the same composition but different styrene contents. Changing the composition affected the glass transition temperature, which could not be detected for highly crosslinked resins. The mechanical properties were improved with increasing styrene content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 563–571, 1999     

BEHAVIOR OF EUCALYPTUS GLOBULUS LIGNIN DURING KRAFT PULPING. II. ANALYSIS BY NMR,ESI/MS,AND GPC

ABSTRACT

Residual and dissolved lignin from different phases of kraft delignification of Eucalyptus globulus wood were isolated and characterized by 1D and 2D ¹H NMR, ¹³C NMR, Electrospray Ionization Mass Spectrometry (ESI/MS), and gel permeation chromatography (GPC). During the temperature rise period, below 70°C, about 20% of the lignin was dissolved without significant structural changes. Above 70°C, the lignin suffered significant degradation/fragmentation in the cell wall prior to dissolution. The lignin ether-linked syringyl units were the most susceptible to alkaline degradation. Through the course of pulping, the residual lignin (RL) revealed a gradual increase of aliphatic moieties of unknown structure, as well as a decrease of native structures such as phenylcoumaran and pino-/syringaresinol lignin units. A significant decrease of the β-O-4 structures content in RL was detected only at the final cooking temperature. The lignin dissolved in the black liquor (BL) consisted of highly branched oligomers with rather low molecular weight (average mass 800–1000 u). A part of BL (about 30%) was chemically linked to carbohydrates and possessed a large molecular weight distribution (500–4000 u). BL showed a progressive decrease in β-O-4 and pino-/syringaresinol structures and formation of enol ether and stilbene structures. The GPC analyses showed a continuous decrease of the molecular weight of both the residual and dissolved lignins during the pulping process, particularly in the residual stage.     

Polymerization of butadiene and isoprene with the NdCl3 · 3TBP-TIBA catalyst system

The isoprene and butadiene polymerization processes with the NdCl₃ · 3TBP-TIBA catalyst system (TBP: tributylphosphate, TIBA: triisobutylaluminium) are studied in detail using an original and very accurate experimental technique. The influences of the initial monomer concentration, the polymerization temperature and the catalyst and cocatalyst concentrations on the conversion, the average molar masses, the polydispersity and the microstructure of the polymers are discussed and explained considering the allylic complexes formed between the neodymium atom and the last monomer unit in the macromolecular chain. A first-order reaction with respect to the monomer was obtained. The calculated value of the activation energy (25.58 kJ mol^?1) is lower than for classical Ziegler-Natta catalysts, thus demonstrating the higher catalytic activity of the NdCl₃ · 3TBP-TIBA catalyst system used. Two types of active centers are possible, as confirmed by GPC data. One of them, which includes aluminium, is more stable and favors the transformation from “anti” allylic units to “syn” allylic units. Thus, the 1,4-cis unit content of the prepared polymers is mainly determined by the TIBA concentration. The catalyst does not react by transfer reactions as TIBA does. The obtained conversions are always higher for butadiene than for isoprene due to a higher tendency of the former to complexate with the neodymium atom and forming allylic complexes.     

Iron catalyst for ammonia synthesis doped with lithium oxide

Iron catalysts doped with Al₂O₃, CaO were obtained by melting iron oxide with 2.2 wt.% of Al₂O₃, 2.1 wt.% of CaO. The reduced catalyst was impregnated with lithium hydroxide water solution. Activity measurements were carried out in the laboratory installation in the temperature range 623–773 K under the pressure of 10 MPa. The activity of catalyst containing 0.79 wt.% of Li₂O and reduced at 773 K was similar to the activity of an industrial iron catalyst doped with potassium oxide. After reduction at 923 K the catalyst containing 0.48 wt.% of Li₂O was about 15% more active than the industrial catalyst. Increasing Li₂O concentration results in the decrease of the surface area of a catalyst reduced at 923 K. The most active catalysts doped with lithium oxide were more active than the industrial catalyst when their activity was calculated and scaled down to surface area units.