Simultaneous biofiltration of H<Subscript>2</Subscript>S,NH<Subscript>3</Subscript> and toluene using cork as a packing material

Simultaneous removal of ternary gases of NH₃, H₂S and toluene in a contaminated air stream was investigated over 185 days in a biofilter packed with cork as microbial support. Multi-microorganisms including Nitrosomonas and Nitrobactor for nitrogen removal, Thiobacillus thioparus (ATCC 23645) for H2S removal and Pseudomonas aeruginosa (ATCC 15692), Pseudomonas putida (ATCC 17484) and Pseudomonas putida (ATCC 23973) for toluene removal were used simultaneously. The empty bed residence time (EBRT) was 40–120 seconds and the inlet feed concentration was 50-180 ppmv for NH₃, 30–160 ppmv for H₂S and 40–130 ppmv for toluene, respectively. The observed removal efficiency was 45–100% for NH₃, 96–100% for H₂S, and 10–99% for toluene, respectively. Maximum elimination capacity was 5.5 g/m³/hr for NH₃, >20.4 g/m³/hr for H₂S and 4.5 g/m³/hr for toluene, respectively. During long-term operation, the removal efficiency of toluene gradually decreased, mainly due to depositions of elemental sulfur and ammonium sulfate on the cork surface. The results of microbial analysis showed that nearly the same population density was observed on the surfaces of cork chips collected at each sampling point. Kinetic model analyses showed that there were no particular evidences of interactions or inhibitions among the microorganisms.     

Examining the use of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles to enhance the NH<Subscript>3</Subscript> sensitivity of polypyrrole films

Summary Polypyrrole (PPy) composite films with different contents of Fe₃O₄ were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH₃ vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH₃ vapor. Meanwhile, the response time was reduced with increasing the Fe₃O₄ content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe₃O₄.     

Low-temperature anti-icing reagents in the Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-Mg(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O system and their properties

The polytherms of ice melting in sections of the Ca(NO₃)₂-Mg(NO₃)₂-CO(NH₂)₂-H₂O system with different component ratios were studied in the temperature interval from 0 to −40°C. A series of nitrate and nitrate-carbonate reagents that are promising for the creation of anti-acing reagents were found, which form eutectics with ice at temperatures from −25 to −39°C. Their properties, viz., melting properties with respect to ice and corrosiveness on metals and alloys, were determined. An effective corrosion inhibitor was selected.     

Effective Utilization of the Catalytically Active Phase: NH<Subscript>3</Subscript> Oxidation Over Unsupported and Supported Co<Subscript>3</Subscript>O<Subscript>4</Subscript>

Abstract  

The performance of pellets of unsupported and silica-supported Co₃O₄ in the ammonia oxidation was investigated as a function of the particle size to investigate the utilization of the catalytically active phase in these materials. The obtained activity in terms of ammonia conversion over the silica-supported Co₃O₄ is higher compared to the conversion over the unsupported Co₃O₄, despite a lower cobalt oxide loading and more severe diffusional limitations. The effectiveness factor for the silica-supported catalyst is slightly lower than the effectiveness factor for the unsupported catalyst in the form of pellets of similar size. However, the effective utilization of cobalt within the catalyst is higher for the silica-supported catalyst, mainly due to the higher dispersion of the catalytically active phase.     

Dissolution of colemanite in (NH<Subscript>4</Subscript>)2SO<Subscript>4</Subscript> solutions

Turkey is the country having the richest boron ores in the world, and colemanite, tincal and ulexite are the ores being mined mostly in Turkey. These ores are used in the production of various boron compounds of which the production methods are generally patented. Colemanite ore also is reacted with sulfuric acid to product boric acid. Produced by this method, boric acid contains various impurities which reduce the market value and are difficult to remove. This study investigated the reaction between colemanite and ammonium sulfate as an alternative method to produce boric acid. Particle size, ammonium sulfate concentration, solid to liquid ratio and reaction temperature were chosen as parameters. In results, the conversion rate was increased by decreasing particle size and solid to liquid ratio, by increasing ammonium sulfate concentration and temperature. A semi-empirical model with 40.46 kJmol⁻¹ activation energy representing this process was found as follows: 1−(1−X)^1/3=2.12×10²·C^1.38·R^−0.75·(S/L)^−0.44·e^−4866/T·t^0.61.     

Crystal structure and thermal expansion of ammonium pentaborate NH<Subscript>4</Subscript>B<Subscript>5</Subscript>O<Subscript>8</Subscript>

Anhydrous ammonium pentaborate NH₄B₅O₈ has been synthesized by thermal dehydration of larderellite NH₄[B₅O₇(OH)₂] · H₂O at a temperature of 290°C for 7 h. The crystal structure has been determined from the X-ray powder diffraction data: a = 7.58667(5) Å, b = 12.00354(8) Å, c = 14.71199(8) Å, R _p = 6.23, R _wp = 7.98, R _B = 12.7, R _F = 8.95, and β-KB₅O₈ structure type. The double interpenetrating framework is formed by pentaborate groups, each consisting of a boron-oxygen tetrahedron and four triangles, in which all oxygen atoms are bridging. The thermal behavior of the NH₄B₅O₈ compound has been investigated using thermal X-ray diffraction. As for other pentaborates of this type, the thermal expansion of the NH₄B₅O₈ compound is anisotropic and reaches a maximum along the a axis. The thermal expansion coefficients are as follows: α _a = 39 × 10^?6, α _b = 6 × 10^?6, α _c = 20 × 10^?6, and α _V = 65 × 10^?6 °C^?1.     

Effects of preparation methods for V<Subscript>2</Subscript>O<Subscript>5</Subscript>-TiO<Subscript>2</Subscript> aerogel catalysts on the selective catalytic reduction of NO with NH<Subscript>3</Subscript>

A series of V₂O₅-TiO₂ aerogel catalysts were prepared by the sol-gel method with subsequent supercritical drying with CO₂. The main variables in the sol-gel method were the amounts of V₂O₅ and when the vanadium precursor was introduced. V₂O₅-TiO₂ xerogel and V₂O₅/TiO₂ (P-25) were also prepared for comparison. The V₂O₅-TiO₂ aerogel catalysts showed much higher surface areas and total pore volumes than V₂O₅-TiO₂ xerogel and impregnated V₂O₅/TiO₂ (P-25) catalysts. The catalysts were characterized by N₂ physisorption, X-ray diffraction (XRD), FT-Raman spectroscopy, temperature-programmed reduction with H₂ (H₂-TPR), and temperature-programmed desorption of ammonia (NH₃-TPD). The selective catalytic reduction of NOx with ammonia in the presence of excess O₂ was studied over these catalysts. Among various V₂O₅-TiO₂ catalysts, V₂O₅ supported on aerogel TiO₂ showed a wide temperature window exhibiting high NOx conversions. This superior catalytic activity is closely related to the large amounts of strong acidic sites as well as the surface vanadium species with characteristics such as easy reducibility and monomeric and polymeric vanadia surface species. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Simultaneous absorption of CO<Subscript>2</Subscript> and SO<Subscript>2</Subscript> into aqueous AMP/NH<Subscript>3</Subscript> solutions in binary composite absorption system

To enhance the absorption rate for CO₂ and SO₂, aqueous ammonia (NH₃) solution was added to an aqueous 2-amino-2-methyl-1-propanol (AMP) solution. The simultaneous absorption rates of AMP and a blend of AMP+ NH₃ for CO₂ and SO₂ were measured by using a stirred-cell reactor at 303 K. The process operating parameters of interest in this study were the solvent and concentration, and the partial pressures of CO₂ and SO₂. As a result, the addition of NH₃ solution into aqueous AMP solution increased the reaction rate constants of CO₂ and SO₂ by 144 and 109%, respectively, compared to that of AMP solution alone. The simultaneous absorption rate of CO₂/SO₂ on the addition of 1 wt% NH₃ into 10 wt% AMP at a p _A1 of 15 kPa and p _A2 of 1 kPa was 5.50×10⁻⁶ kmol m⁻² s⁻¹, with an increase of 15.5% compared to 10 wt% AMP alone. Consequently, the addition of NH₃ solution into an aqueous AMP solution would be expected to be an excellent absorbent for the simultaneous removal of CO₂/SO₂ from the composition of flue gas emitted from thermoelectric power plants.     

Template-free synthesis of hierarchically macro-mesoporous Mn-TiO<Subscript>2</Subscript> catalysts for selective reduction of NO with NH<Subscript>3</Subscript>

This study described a template-free method for the synthesis of hierarchically macro-mesoporous Mn-TiO₂ catalysts. The promoting effect of Mn doping and the hierarchically macro-mesoporous architecture on TiO₂ based catalysts was also investigated for the selective reduction of NO with NH₃. The results show that the catalytic performance of TiO₂ based catalysts was improved greatly after Mn doping. Meanwhile, the Mn-TiO₂ catalyst with the hierarchically macro-mesoporous architecture has a better catalytic activity than that without such an architecture.

Open image in new window

     

Synthetic spinels of the system MgO-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

Synthetic spinels of the system MgO-Cr₂O₃-Al₂O₃-Fe₂O₃ are considered and the desirability of organizing their production for the refractory industry is demonstrated. Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008.     

Mild-thermal fabrication and phase conformation of chopped glass fiber-reinforced low-density unsaturated polyester resin with NH<Subscript>4</Subscript>HCO<Subscript>3</Subscript>

Chopped glass fiber-reinforced low-density unsaturated polyester resin product (CFR-LDUPRP) was fabricated utilizing chopped glass fiber and ammonium bicarbonate through an innovative mild-thermal process featuring an ideal phase conformation. Based on the mild-thermal mechanism and preliminary experiments, an orthogonal experiment was conducted to obtain the optimal conditions of CFR-LDUPRP fabrication. The optimal fabrication temperature of 76.0 °C, 20.00 phr of 3 mm chopped glass fiber, 2.50 phr of NH₄HCO₃ and 1.50 phr of tert-butylperoxy benzoate (TBPB) comprised the optimal conditions for CFR-LDUPRP fabrication. Under this condition, the density (ρ), compressive strength (P), and specific compressive strength (P_s) of CFR-LDUPRP specimen were 0.63?±?0.02 g cm^??3, 24.29?±?0.73 MPa, and 38.56?±?1.02 MPa g^??1 cm³, in the given order. The analyses of nonisothermal DSC and semi-quantitative FTIR revealed that NH₄HCO₃ neutralized the residual acid in the resin, leading to an early polymerization of resin and a prolonged curing process of UPR. The endothermic decomposition of NH₄HCO₃ and the vaporization of water enabled a mild-thermal mechanism, which was beneficial for the growth of bubbles and for the distribution of chopped glass fiber in the resin. Proper phase conformation of the resin, bubbles, chopped glass fiber together with cracks and microvoids in the resin matrix, characterized by SEM and ¹H NMR, facilitated the polymerization of UPR and improved properties of CFR-LDUPRP. Bubbles diameter ranged from 0.27 to 0.61 mm without linking or destroyed bubbles.     

Adsorption of CO<Subscript>2</Subscript> and CO on H-zeolites with different framework topologies and chemical compositions and a correlation to probing protonic sites using NH<Subscript>3</Subscript> adsorption

Adsorption of CO₂ and CO at 25 °C has been conducted using commercially-available (Y, ZSM-5) and laboratory-synthesized (SSZ-13, SAPO-34) H-zeolites with different framework topologies and chemical compositions, and their textual and surface properties have been characterized by N₂ sorption and NH₃ adsorption techniques. All the zeolites were microporous, although ZSM-5 and SSZ-13 apparently showed a mesoporous sorption behavior due to the interparticle spaces. The zeolites had Si/Al values in the order of SSZ-13 (16.44) > ZSM-5 (16.08) ? Y (2.82) ? SAPO-34 (0.19). Regardless, high CO₂ adsorption capacity was obtained for SSZ-13 and SAPO-34 with a CHA framework. The FAU zeolite Y with the highest micropore volume showed less CO₂ adsorption than the CHA zeolites and the MFI-type ZSM-5 yielded the poorest performance. Probing acid sites in the H-form zeolites using NH₃ disclosed that these all contain both weak and strong acid sites with significant dependence of their strengths and amounts on the topology. The acid strength of the weak acid sites in the CHA zeolites was the weakest, which might allow a stronger interaction with CO₂. The H-zeolites gave CO₂/CO selectivity factors that were in the range of 4.61–11.0, depending on the framework topology.     

The Effect of CH<Subscript>4</Subscript> on NH<Subscript>3</Subscript>-SCR Over Metal-Promoted Zeolite Catalysts for Lean-Burn Natural Gas Vehicles

We present a systematic investigation of the deNO_x activity of two commercial metal exchanged zeolite NH₃-SCR catalysts, a Cu-SAPO and a Fe-BEA, in view of their application to the exhaust after-treatment systems of lean-burn natural gas vehicles. The catalytic activity data collected under realistic operating conditions, representative of the after-treatment system of lean-burn vehicles, were compared to those obtained adding methane to the gas feed stream in order to assess the impact of this hydrocarbon, which is usually emitted from natural gas engines, on the NH₃-SCR catalytic chemistry. Our results indicate a negligible impact of methane on the SCR activity at all conditions, but in the presence of a large excess of NO₂ at T?>?400 °C due to methane oxidation by NO₂. The data collected over the two individual metal-promoted zeolites were also compared with those obtained combining both catalysts in sequential arrangements, in order to take advantage of their complementary high activities in different temperature ranges. The Fe-zeolite?+?Cu-zeolite sequence outperformed the two individual components in terms of both overall deNOx efficiency and N₂O selectivity, and was equally insensitive to methane.     

CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> catalyst prepared by physical mixing for NH<Subscript>3</Subscript> selective catalytic reduction: Evidence about the migration of sulfates from TiO<Subscript>2</Subscript> to CeO<Subscript>2</Subscript> via simple calcination

A mechanical mixture of CeO₂ and TiO₂ powder with a small amount of sulfate was applied for the selective catalytic reduction (SCR) of NO with NH₃. After calcination at 500 oC, the mixed sample showed significantly enhanced activity and selectivity compared to the uncalcined one and, moreover, demonstrated even higher activity than the conventional V₂O₅/TiO₂ catalyst above 300 °C. Combined characterization results revealed that the main active sites were newly formed sulfate species on CeO₂, the number of which increased with calcination. Temperatureresolved DRIFT spectra provided convincing evidence about the migration of sulfate species from TiO₂ to CeO₂, as confirmed from the shift of v(S=O) band as a result of the mechanical mixing and the subsequent calcination.     

Properties of unsupported MoS<Subscript>2</Subscript> species produced in the preparation of MoS<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> using a sonochemical method

Unsupported MoS₂ particles, which were produced in the preparation of MoS₂/Al₂O₃ using a sonochemical method, were successfully separated from the prepared sample catalyst by adding oleylamine as an agent for dispersing the unsupported particles. The fraction of the unsupported MoS₂, which was estimated based on Mo balance, varied between 0.03 and 0.4, independent of the Mo loading levels investigated (6–54 wt% of Mo). The activity of the unsupported MoS₂ for the hydrodesulfurization of dibenzothiophene was nearly the same as that of the Al₂O₃-supported MoS₂, indicating that the activity of the prepared catalyst was not affected by the presence of the unsupported MoS₂ particles.     

Effect of vanadium surface density and structure in VOx/TiO<Subscript>2</Subscript> on selective catalytic reduction by NH<Subscript>3</Subscript>

We investigated the correlation between vanadium surface density and VOx structure species in the selective catalytic reduction of NOx by NH₃. The properties of the VOx/TiO₂ catalysts were investigated using physicochemical measurements, including BET, XRD, Raman spectroscopy, FE-TEM, UV-visible DRS, NH₃-TPD, H₂-TPR, O₂-On/Off. Catalysts were prepared using the wet impregnation method by supporting 1.0-3.0 wt% vanadium on TiO₂ thermally treated at various calcination temperatures. Through the above analysis, we found that VOx surface density was 3.4 VOx/nm², and the optimal V loading amounts were 2.0-2.5 wt% and the specific surface area was 65-80m²/g. In addition, it was confirmed that the optimal VOx surface density and formation of vanadium structure species correlated with the reaction activity depending on the V loading amounts and the specific surface area size.     

Electrical conductivity of CuI-AsI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> and CuI-SbI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of chalcogenide semiconductor films in the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ systems, which have been prepared by chemical deposition from mono-n-butylamine, has been studied as a function of the temperature and film composition. It has been established that the electrical conductivity of the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ films is predominantly determined by the copper iodide content. It has been demonstrated that the electrical properties of the chalcogenide glasses and the related films are characterized by the same values to within the experimental error, which is explained by the same model of dissolution of vitreous semiconductors in amines with the retention of the electrical properties of chalcogenide glasses after the deposition of films from their solutions.