Influence of support acidity on electronic state of platinum in oxide systems promoted by SO4 2− anions

The electronic state of platinum supported on SO₄/ZrO₂, SO₄/TiO₂, SO₄/Al₂O₃, and SO₄/SiO₂ systems and on systems unpromoted by sulfur was investigated by diffuse-reflectance IR spectroscopy using CO as the probe molecule. The introduction of SO₄ ²⁻ anions increases the electron deficit on platinum particles. This suppresses the formation of bridging CO complexes with the metal, leads to the high-frequency shift of absorption maxima of CO adsorbed in the linear form, and stabilizes positively charged metal species (Pt^δ+ and Pt⁺) during the reduction process. The formation of the positively charged species includes the interaction between the acidic protons and the metal particles yielding [Pt−H]^δ+ adducts. The extent of the influence of the support on the electronic state of the metal increases in the series SO₄/SiO₂<SO₄/Al₂O₃<SO₄/TiO₂<SO₄/ZrO₂ in parallel with an increase in the strength of the acid sites in the system. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1099, June, 1998.     

Optimization of SO2-catalyzed steam pretreatment of corn fiber for ethanol production

A batch reactor was employed to steam explode corn fiber at various degrees of severity to evaluate the potential of using this feedstock as part of an enzymatically mediated cellulose-to-ethanol process. Severity was controlled by altering temperature (150–230°C), residence time (1–9 min), and SO₂ concentration (0–6% [w/w] dry matter). The effects of varying the different parameters were assessed by response surface modeling. The results indicated that maximum sugar yields (hemicellulose-derived water soluble, and cellulose-derived following enzymatic hydrolysis) were recovered from corn fiber pretreated at 190°C for 5 minutes after exposure to 3% SO₂. Sequential SO₂-catalyzed steam explosion and enzymatic hydrolysis resulted in a conversion efficiency of 81% of the combined original hemicellulose and cellulose in the corn fiber to monomeric sugars. An additional posthydrolysis step performed on water soluble hemicellulose stream increased the concentration of sugars available for fermentation by 10%, resulting in the high conversion efficiency of 91%. Saccharomyces cerevisiae was able to ferment the resultant corn fiber hydrolysates, perhydrolysate, and liquid fraction from the posthydrolysis steps to 89, 94, and 85% of theoretical ethanol conversion, respectively. It was apparent that all of the parameters investigated during the steam explosion pretreatment had a significant effect on sugar recovery, inhibitory formation, enzymatic conversion efficiency, and fermentation capacity of the yeast.     

Effect of NO, SO2, and O2 on the conversion of nitrous oxide on iron-containing zeolite catalysts

Conditions were found for facilitation of the conversion of nitrous oxide in the presence of Fe-containing zeolite catalysts by oxidants (NO, SO₂, and O₂). The results were interpreted in the framework of a mechanism involving decomposition of N₂O. The effect of NO_x on the reduction of nitrous oxide by C₃-C₄ alkanes was established. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 241–245, July–August, 2006.     

Effect of sulfuric and phosphoric acid pretreatments on enzymatic hydrolysis of corn stover

The pretreatment of corn stover with H₂SO₄ and H₃PO₄ was investigated. Pretreatments were carried out from 30 to 120 min in a batch reactor at 121°C, with acid concentrations ranging from 0 to 2% (w/v) at a solid concentration of 5% (w/v). Pretreated corn stover was washed with distilled water until the filtrate was adjusted to pH 7.0, followed by surfactant swelling of the cellulosic fraction in a 0–10% (w/v) solution of Tween-80 at room temperature for 12 h. The dilute acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digetibility. Hemicellulose recovery was 62–90%, and enzymatic digestibility of the cellulose that remained in the solid was >80% with 2% (w/v) acid. In all cases studied, the performance of H₂SO₄ pretreatment (hemicellulose recovery and cellulose digestibility) was significantly better than obtained with H₃PO₄. Enzymatic hydrolysis was more effective using surfactant than without it, producing 10–20% more sugar. Furthermore, digestibility was investigated as a function of hemicellulose removal. It was found that digestibility was more directly related to hemicellulose removal than to delignification.     

Investigation on The Thermal Properties of Fe2O(SO4)2. Part II

Fe₂O(SO₄)₂ is a secondary product of the decomposition of FeSO₄⋅H₂O. Part I of this study presents results on the synthesis of Fe₂O(SO₄)₂ in gaseous environment containing either low or high concentration of oxygen. In this paper the existence of differences between the structures of Fe₂O(SO₄)₂ and Fe₂(SO₄)₃ is proved on the basis of a detailed thermal study of Fe₂O(SO₄)₂ upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous environments as well as by presenting kinetic data on the processes of decomposition of both compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

The PVT properties of concentrated aqueous electrolytes IX. The volume properties of KCl and K2SO4 and their mixtures with NaCl and Na2SO4 as a function of temperature

The densities of KCl and K₂SO₄ were measured from dilute solutions to saturation from 5 to 95°C. The data were combined with literature data to produce density and apparent molal volume, V_φ, equations from 0 to 100°C and to saturation. The standard deviations of the density equations were 30×10⁻⁶ g-cm⁻³ and 32×10⁻⁶ g-cm⁻³, respectively, for KCl and K₂SO₄. Pitzer equations were used to fit the V_φ data. The resulting infinite dilute partial molal volumes, V^o, were in reasonable agreement with literature data. The densities of the mixtures of the six combinations of the salts KCL, K₂SO₄ NaCl and Na₂SO₄ were measured at I=2.0 and t=5, 25, 55 and 95°C. The resulting volumes of mixing were fitted to equations of the form

Steam pretreatment of acid-sprayed and acid-soaked barley straw for production of ethanol

Barley is an abundant crop in Europe, which makes its straw residues an interesting cellulose source for ethanol production. Steam pretreatment of the straw followed by enzymatic hydrolysis converts the cellulose to fermentable sugars. Prior to pretreatment the material is impregnated with a catalyst, for example, H₂SO₄, to enhance enzymatic digestibility of the pretreated straw. Different impregnation techniques can be applied. In this study, soaking and spraying were investigated and compared at the same pretreatment condition in terms of overall yield of glucose and xylose. The overall yield includes the soluble sugars in the liquid from pretreatment, including soluble oligomers, and monomer sugars obtained in the enzymatic hydrolysis. The yields obtained differed for the impregnation techniques. Acid-soaked barley straw gave the highest overall yield of glucose, regardless of impregnation time (10 or 30 min) or acid concentration (0.2 or 1.0 wt%). For xylose, soaking gave the highest overall yield at 0.2 wt% H₂SO₄. An increase in acid concentration resulted in a decrease in xylose yield for both acid-soaked and acid-sprayed barley straw. Optimization of the pretreatment conditions for acid-sprayed barley straw was performed to obtain yields using spraying that were as high as those with soaking. For acid-sprayed barley straw the optimum pretreatment condition for glucose, 1.0 wt% H₂SO₄ and 220°C for 5 min, gave an overall glucose yield of 92% of theoretical based on the composition of the raw material. Pretreatment with 0.2wt% H₂SO₄ at 190°C for 5 min resulted in the highest overall xylose yield, 67% of theoretical based on the composition of the raw material.     

SO2 absorption of the CO2- laser emission measured by the photoacoustic technique

Spectra of coincidence of SO₂ IR absorption with CO₂-laser emission at pressure of 50,100 and 450 Torr were recorded by the use of a photoacoustic detection method in the whole range of CO₂-laser emission. The spectra show that SO₂ absorbs many CO₂-laser lines in the range 1084–1071 cm⁻¹ with the strongest absorption at 1082.29cm⁻¹, laser line R(26). The intensities of all absorptions rise with increasing pressure, but some absorptions change their relative intensity with respect to one another. In addition, the fine structure of line spectra, characteristic of lower pressure samples, disappear as pressure is increased.     

H2SO4/Silicagel: Highly Efficient Catalyst for the Synthesis of α-Aminonitriles Using Trimethysilyl Cyanide

Summary. The multicomponent Strecker reaction using trimethylsilyl cyanide was performed at room temperature and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of H₂SO₄ adsorbed on silica gel.     

Removal of SO2 from Gas Streams by Oxidation using Plasma-Generated Hydroxyl Radicals

The key problem for the removal of SO₂ by electrical discharge methods is how to obtain the hydroxyl radicals at high concentration and large production rates. With the micro-gap discharge method, O₂ and H₂O in simulated gas streams (N₂/O₂/H₂O/SO₂) are ionized into a large number of OH^. radicals to oxidize SO₂ into SO₃ which reacts with H₂O forming H₂SO₄ droplets at 120 °C in the absence of any catalyst or absorbent. The droplets are captured with an electrostatic precipitator. As a result, conversion of SO₂ to primarily H₂SO₄ is limited by the generation of OH^. radicals. By increasing the reduced field and concentrations of O₂ and H₂O, the amount of OH^. radicals increase resulting in more removal of SO₂ from gas streams. The removal efficiency of SO₂ reaches 100% when the residence time is only 0.74 s. Therefore, a new gas-phase oxidation method for removal of SO₂ without NH₃ additive is found.     

Studies of dehydration kinetics of Li2SO4·H2O by the master plots method

The kinetics of Li₂SO₄·H₂O dehydration in static air atmosphere was studied on the basis of nonisothermal measurements by differential scanning calorimetry. Dehydration data were subjected to an integral composite procedure, which includes an isoconversional method, a master plots method and a model-fitting method. Avrami-Erofeev equation was found to describe all the experimental data in the range of conversion degrees from 0.1 to 0.9. The determined activation energy equals 65.45 kJ·mol⁻¹ with standard deviation ±0.47 kJ·mol⁻¹. The estimated value of parameter m in Avrami-Erofeev equation is 2.15 with standard deviation ±0.11. Also, the obtained pre-exponential factor is 7.79×10⁵ s⁻¹ with standard deviation ±0.55×10⁵ s⁻¹. The results show that the present integral composite procedure gives self-consistent kinetic parameters.     

Steam pretreatment of Salix with and without SO2 impregnation for production of bioethanol

In the wood-to-ethanol process, pretreatment of the material is necessary prior to enzymatic hydrolysis to obtain high overall yields of sugar and ethanol. Steam pretreatment of fast-growing Salix either with or without SO₂ impregnation has been investigated by varying different parameters. Overall glucose yields of above 90% and overall xylose yields higher than 80% were obtained both with and without impregnation. However, the most favorable pretreatment conditions for the separate yields of glucose and xylose differed to a lower degree using SO₂-impregnated wood chips, resulting in higher total sugar yield than that obtained with non-impregnated wood chips.     

Preparation of ethyl levulinate from wheat stalk over Zr(SO4)2/SiO2

A series of Zr(SO₄)₂/SiO₂ solid acid catalysts with different Zr(SO₄)₂ loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N₂, and temperature-programmed desorption of NH₃. The results showed that the active component Zr(SO₄)₂ was successfully adhered to the mesoporous SiO₂, and the acid amount of Zr(SO₄)₂/SiO₂ increased with the increasing of the Zr(SO₄)₂ loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO₄)₂/SiO₂ to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO₄)₂/SiO₂ exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO₄)₂ loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation.     

Ce(SO4)2‐Mediated Nitration of N,N‐Dialkylanilines with NaNO2 in Water

Ce(SO₄)₂‐mediated nitration of N,N‐dialkylanilines with NaNO₂ using water as the solvent has been achieved in good to excellent yields. The nitrating reaction proceeded smoothly at ambient temperature.     

一种SO2固定及用于制备BaSO3或BaSO4的方法

在常温常压下,由乙二胺（EDA）和乙二醇及其衍生物（EGs）组成的混合体系可捕集SO₂并转化为一种SO₂储集材料（SO₂SM）。EDA+EGs体系呈现了强的捕集性能（0.364~0.662 g_SO2·gabsorbent^-1）。FTIR,XPS和XRD结果确证了SO₂SM为一种烷基亚硫酸盐。以EG-SO₂SM为原料制备具有多种形貌的BaSO₃或BaSO₄,在此过程中,EG-SO₂SM不仅提供了原材料,而且可以释放EDA和EG用作表面活性剂,调控晶体的结晶化过程。     

Removal of SO2 and the simultaneous removal of SO2 and NO from simulated flue gas streams using dielectric barrier discharge plasmas

A gas-phase oxidation method using dielectric barrier discharges (DBDs) has been developed to remove SO₂ and to simultaneously remove SO₂ and NO from gas streams that are similar to gas streams generated by the combustion of fossil fuels. SO₂ and NO removal efficiencies are evaluated as a function of applied voltage, temperature, and concentrations of SO₂, NO, H₂O_(g), and NH3. With constant H₂O_(g) concentration, both SO₂ and NO removal efficiencies increase with increasing temperature from 100 to 160°C. At 160°C with 15% by volume H₂0_(g), more than 95% of the NO and 32% of the S0₂ are simultaneously removed from the gas stream. Injection of NH₃ into the gas stream caused an increase in S0₂ removal efficiency to essentially 100%. These results indicate that DBD plasmas have the potential to simultaneously remove SO₂ and NO from gas streams generated by large-scale fossil fuel combustors.     

A monitor for atmospheric sulphur dioxide,based on enrichment of SO2 by a polydispersive water aerosol

A monitor for continuous analysis of sulphur dioxide in the atmosphere at the ppb v/v level (1 ppb v/v = 2.62 g/m³ SO₂) is described. The apparatus operates on the principle of equilibrium accumulation of sulphur dioxide from the air by a polydispersive water aerosol which continuously transfers SO₂ from an air-flow of l/min into microlitre volumes of water condensate. High sensitivity (1 ppb v/v), low relative error (± 5% at 4 ppb v/v SO₂), high selectivity (CO₂ does not interfere at a concentration of 2 × 10³ ppm v/v, interference by NO _x and H₂S is acceptably low), and low response delay (10 s) are provided by a compact coupling of the enrichment procedure with conductivity detection of SO₂ in the film of water aerosol condensate formed directly on the wire-gauze sensor. The reliability of the method has been studied under simulated conditions, with spectrophotometric method as reference. The analyser is computer-controlled, and the detector response is processed on-line and displayed (as g/m³) in real-time on a screen or is transmitted telemetrically to a control centre. It is portable and suitable for use in both stationary and moving locations.The paper is dedicated to the 65th anniversary of the birthday of Prof. Josef F. K. Huber     

Investigation on The Thermal Properties of Fe2O(SO4)2. Part I

The data on the thermal decomposition of FeSO₄?H₂O upon various regimes of heating and gaseous environment prove the formation of intermediate products of the types Fe₂O(SO₄)₂ and FeOHSO₄, their stability and amount being determined mainly by temperature and oxygen-reduction potential.

This communication aims at presenting results on the synthesis and characterization of Fe₂O(SO₄)₂. The synthesis was carried out using a laboratory thermal equipment operating under isothermal conditions in the temperature range 713–813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe₂O(SO₄)₂ is stable are established. The effect of three basic parameters on the synthesis of Fe₂O(SO₄)₂ is clarified: the oxygen partial pressure, the ratio P_H2O/P_O2 and the temperature and the mode of heating. Mössbauer spectroscopy and X-ray diffraction data for Fe₂O(SO₄)₂ are presented.

     

Impact of rice crop residue burning on levels of SPM,SO2 and NO2 in the ambient air of Patiala (India)

Ground-based ambient air monitoring was conducted at five different locations in and around Patiala city (29°49′–30°47′N Latitude, 75°58′–76°54′E Longitude) in Northern India in order to determine the impact of open burning of rice (Oriza sativa) crop residues on concentration levels of suspended particulate matter (SPM), sulphur dioxide (SO₂) and nitrogen dioxide (NO₂). Covering sensitive, residential, agricultural, commercial and urban areas, sampling of these pollutants was organised during August 2006 to January 2007 and August 2007 to January 2008 casing two rice crop residue burning periods (October–November) using a high volume sampling technique combined with gaseous sampling systems. Gravimetric analysis was used in the estimation of total suspended particulate matter (TSPM) whereas SO₂ and NO₂ concentration was determined using spectrophotometer (Specord205, Analytikjena). Monthly average concentrations of SPM, SO₂ and NO₂ have shown significant up and down features at all the selected sampling sites during the study period. Monthly average concentrations (24 hour) of SPM, SO₂ and NO₂ varied from 100 ± 11 µg m^?3 to 547 ± 152 µg m^?3, 5 ± 4 µg m^?3 to 55 ± 34 µg m^?3 and 9 ± 5 µg m^?3 to 91 ± 39 µg m^?3. Substantially higher concentrations were recorded at the commercial area site as compared to the other sampling sites for all the targeted air pollutants. Levels of SPM, SO₂ and NO₂ showed clear increase during the burning months (October–November) incorporated with the effect of meteorological parameters especially wind direction, precipitation and atmospheric temperature.     

Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Ce(SO4)2-SiO2 as a Heterogeneous and Recyclable Catalyst

A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported ceric sulfate [Ce(SO₄)₂-SiO₂] as a heterogeneous catalyst from an aldehyde, 1,3-dicarbonyl compound, and urea or thiourea at 110 °C under solvent-free conditions. Compared with the classical Biginelli reaction, this new method consistently has better yields, short reaction time, easy separation, and tolerance toward various functional groups.