SORPTION PROCESSES OF NATURAL IRANIAN BENTONITE EXCHANGED WITH CD2+, CU2+, NI2+, AND PB2+ CATIONS

Experimental studies on the retention of cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), and lead (Pb²⁺) by bentonite samples from Iran were conducted using single- and multiple-component solutions. Based on the sorption capacity of bentonite the following order was obtained for single- and multiple-component solutions: Pb²⁺ > Cd²⁺ > Ni²⁺ > Cu²⁺. The maximum adsorption capacities of bentonite with metals in single- and multiple-component solutions were 29.5%, 22.5%, 19.2%, and 17.1% and 13.5%, 13.4%, 12.1%, and 9.1% for Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺, respectively. Desorption isotherms of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ deviated significantly from the sorption isotherms, thereby indicating irreversible or very slowly reversible sorption. Finally, soil solution saturation indices and metal speciation were assessed using the Visual MINTEQ 2.6 program and the probability of mineral precipitation was supported by scanning electron microscopy.     

Simple microwave synthesis of TiO2/NiS2 nanocomposite and TiO2/NiS2/Cu nanocomposite as an efficient visible driven photocatalyst

Approximately 47% of solar-terrestrial radiation is visible. It is a great achievement to produce a highly efficient visible driven photocatalyst. Here TiO₂/NiS₂/Cu nanocomposite was prepared as a highly active visible driven photocatalyst. TiO₂/NiS₂/Cu nanocomposite was prepared by microwave method. It degrades 92%, 86%, 87%, and 88% of Rhodamine B (RhB), Methyl orange (MO), Acid Black 1 (AB1), and Acid Brown 214 (AB214), respectively. Adding NiS₂ and Cu to TiO₂ dramatically increased the degradation efficiency from 17% for bare TiO₂ to 92% for TiO₂/NiS₂/Cu nanocomposite under visible light. As-prepared TiO₂/NiS₂/Cu nanocomposite was characterized by SEM, TEM, XRD, DRS, BET, and EDX.     

Li2O-ZrO2-SiO2/Al2O3 nanostructured composites for microelectronics applications

Nanostructured composites of the LZS (19.58Li₂O.11.10ZrO₂.69.32SiO₂) and LZS (19.58Li₂O.11.10ZrO₂.69.32SiO₂) + (1, 2.5, 5 vol.%) Al₂O₃ systems were obtained through a colloidal approach using nanoparticulate oxides as precursors. Stable suspensions containing 40 vol.% of solids were obtained, after deagglomeration for 24 h in a ball mill with 4% ammonium polyacrylate as a deflocculant and 15% of polymethylmethacrylate as a binder to achieve green tapes with high uniformity, easy handling and without macroscopic defects. The fired tapes displayed relative densities between 69 and 81% of their theoretical values and very low dielectric constants and loss tangents, which would allow the application of these materials in microelectronics. The addition of alumina allowed the tuning of the thermal expansion coefficients of the produced tapes, which in turn enabled the co-firing of the materials with a silicon wafer. The interfacial region between the materials is pristine and free of cracks, thus highlighting the versatility of the utilized approach towards producing fine-tuned dielectrics for advanced microelectronics applications.     

Thermal properties of ZrB2-TiB2 solid solutions

Zirconium diboride ceramics were prepared with additions of up to 50 vol.% TiB₂. The resulting (Zr,Ti)B₂ ceramics formed complete solid solutions based on x-ray diffraction. The addition of TiB₂ resulted in grain size decreasing from 22 μm for nominally pure ZrB₂ to 7 μm for ZrB₂–50 vol.% TiB₂. The thermal conductivity at 25°C ranged from 93 W/m⋅K for nominally pure ZrB₂ to 58 W/m⋅K for ZrB₂–50 vol.% TiB₂. Thermal conductivity was as high as 67 W/m⋅K for nominally pure ZrB₂ at 2000°C, but dropped to 59 W/m K with the addition of 50 vol.% TiB₂. Electrical resistivity measurements were used to calculate the electron contribution to thermal conductivity, which was 76 W/m⋅K for nominally pure ZrB₂ decreasing to 57 W/m⋅K when 50 vol.% TiB₂ was added. The phonon contribution to thermal conductivity did not change significantly for ≤10 vol.% TiB₂. Additions of ≥25 vol.% TiB₂ reduced the phonon contribution to nearly zero for all temperatures.     

Preferential CO oxidation over Pt–SnO2/Al2O3 in hydrogen rich streams containing CO2 and H2O (CO removal from H2 with PROX)

The effects of reaction gases including CO₂ and H₂O and temperature on the selective low-temperature oxidation of CO were studied in hydrogen rich streams using a flow micro-reactor packed with a Pt–SnO₂/Al₂O₃ sol–gel catalyst that was initially designed and optimized for operation in the absence of CO₂ and H₂O. 100% CO conversion was achieved over the 1 wt% Pt–3 wt% SnO₂/Al₂O₃ catalyst at 110 °C using a feed composition of 1.0% CO, 1.5% O₂, 25% CO₂, 10% H₂O, 58% H₂ and He as balance at a space velocity of 24,000 cm³/(g h). CO₂ in the feed was found to decrease CO conversion significantly while the presence of H₂O in the feed increased CO conversion, balancing the effect of CO₂.     

Phase formation and lattice distortion of Lu2O3-doped ZrO2 in comparison with Y2O3-doped ZrO2

Lu₂O₃ and Y₂O₃ doping of 8, 11, and 18 mol% in ZrO₂ were prepared by solid solution reaction, aiming to study the phase stabilization of Lu₂O₃-doped ZrO₂ and Y₂O₃-doped ZrO₂ in terms of phase formation and lattice distortion. The Rietveld refinement results indicated that Lu₂O₃-doped ZrO₂ and Y₂O₃-doped ZrO₂ followed the same trend in terms of cubic phase fraction, increasing from 25%–30% (8 mol%) to 95%–100% (11 and 18 mol%). This phase formation was confirmed by observing the same diffraction ring pattern observed for the Lu₂O₃-doped ZrO₂ and Y₂O₃-doped ZrO₂. The Vickers hardness of the Lu₂O₃-doped ZrO₂ was 4.3% higher than that of Y₂O₃-doped ZrO₂ at 8 mol%, but 9.7% and 14.8% lower at 11 and 18 mol%, respectively. This was likely caused by the lattice distortion effect of Y₂O₃ doping overpowering the field strength difference between Lu³⁺ and Y³⁺.     

Preferential CO oxidation over activated carbon supported catalysts in H2-rich gas streams containing CO2 and H2O

Selective CO oxidation (PROX) was studied at 423 K over 1% Pt–0.25% SnO_x and 1% Pt–1% CeO_x catalysts supported on un-oxidized and oxidized activated carbon (AC) using feed mixtures simulating the reformate coming from fuel processors. Effects of the addition of 15% CO₂ or (15% CO₂ + 10% H₂O) into feed mixtures containing 1% CO, 1% O₂, 60% H₂ and He were determined for nine different AC-supported catalysts, and the results were compared with those obtained with pure H₂-rich feed. Unlike other PROX catalysts having oxide supports, introduction of CO₂ into pure feed drastically increased CO conversion on all nine catalysts supported on oxidized or un-oxidized AC regardless of impregnation strategy.1% Pt–0.25% SnO_x supported on HNO₃-oxidized AC stands out as a potential candidate for commercial use in PROX since it yields 100% CO conversion under realistic feed conditions. 1% Pt–1% CeO_x catalysts prepared by sequential or co-impregnation and supported on air-oxidized AC also give 100% CO conversion in H₂-rich feed containing (CO₂ + H₂O) during extended run times and hence hold promise as PROX catalysts.     

Ozone/H2O2 Performance on the Degradation of Sulfamethoxazole

This work aims to analyze the contribution of H₂O₂ on ozonation of Sulfamethoxazole (SMX). A single ozonation was able to totally remove SMX. TOC and COD depletion rates after a transferred ozone dose of 60 mg/L was related to the formation and decomposition of H₂O₂. An increase on O₃ gas inlet concentration from 10 g/m³ to 20 g/m³ improved COD abatement from 11% to 36%. When the presence of H₂O₂ at the beginning of ozonation was tested, it was verified that COD and TOC degradation were enhanced, attaining maximum values of 76% and 32%, respectively, when compared with 35% and 15% reached in a single ozonation.     

催化氨氧化2-甲基吡嗪合成2-氰基吡嗪的研究

实验采用自制的Sb2O3-V2O5-TiO2/SiO2型催化剂,研究了以2-甲基吡嗪为原料氨氧化催化合成2-氰基吡嗪的工艺条件,通过对反应温度、液时空速、氨气流率、空气流率等影响因素的考察,确定了适合该催化剂的工艺条件:催化剂装量19mL,进料液时空速0.79h-1,n(2-MP)∶n(NH3)∶n(Air)为1∶5.9∶36,温度370°C。2-甲基吡嗪的转化率达到90%以上,选择性达到70%以上,产品收率达到60%以上。并对其反应原理及工业化问题进行了初步的探讨。     

REFRACTIVE INDICES OF SOME GLASSES IN THE TERNARY SYSTEM K2O 4SiO2-Fe2O3-SiO2*

In the course of some phase-rule investigations of the ternary system K₂O-4SiO₂-Fe₂O₃-SiO₂ by the “quenching method” of Shepherd, Rankin, and Wright, the refractive indices of 30 glasses were measured by the usual petrographic immersion method. The refractivities varied from 1.438 for a K₂O-7SiO₂ glass to 1.621 for the most ferriferous glass which contained 32.3% Fe₂O₃. The maximum FeO content reached a value of 0.33 % in a glass originally containing 25 % Fe₂O₃. Along the sections K₂O 4SiO₂, K₂O-5SiO₂, K₂O-6SiO₂, and K₂O-7SiO₂, the relation between the Fe₂O₃ content of the glasses and the refractive index is apparently linear. The isofracts, however, in the ternary system are curved lines.     

2D/2D SnS2/MoS2 layered heterojunction for enhanced supercapacitor performance

Two-dimensional (2D) SnS₂/MoS₂ heterojunction with a 2D/2D novel structure was used as electrode material for enhanced supercapacitor performance. Compared with the sole SnS₂, the as-prepared 2D/2D SnS₂/MoS₂ layered heterojunction has exhibited great improvement in supercapacitor properties. This novel structure can effectively prevent agglomeration and stacking in electrochemical process, and 2D/2D structure is beneficial to intercalation and desorption of ions in electrochemical processes. The experiment result shows that MoSn₅ (samples with 5% MoSn5 mole ratios) display a specific capacitance of 466.6 F/g at the current density of 1 A/g in 0.5 mol/L potassium hydroxide solution, an impressive cycling stability with 88.2% capacitance retention at current density of 4 A/g. In addition, the as-fabricated symmetric supercapacitor exhibited high energy density of 115 Wh kg⁻¹ at the power density of 2230 Wh kg⁻¹. This work provides a fundamental investigation of 2D/2D layered material synergistic effect on the electrochemical process.     

Highly selective vapor phase Fries rearrangement of phenyl acetate to 2-hydroxyacetophenone using H3PO4/ZrO2–TiO2

ZrO₂–TiO₂ mixed oxides with a Ti and Zr molar ratio of 1/1 were prepared with and without surfactant by the sol–gel method. Catalysts containing 5–35% H₃PO₄ were prepared using these mixed oxides and the catalytic performance of each material for vapor phase Fries rearrangement of phenyl acetate (PA) to 2-hydroxyacetophenone (2-HAP) was determined. At optimized conditions, the conversion of PA over 15 wt.% H₃PO₄/TiO₂–ZrO₂-surf and 15 wt.% H₃PO₄/TiO₂–ZrO₂varied between 91% and 85.2% and selectivity to 2-HAP was between 81.9% and 48.3%, respectively. In all cases, the formation of 2-HAP was clearly favored in comparison to that of para isomer. The 4-HAP in the improved conditions was about 1.1%. In comparison with other catalysts, the percentage of phenol in the optimized condition was lower than 16%. The solvent effect on Fries rearrangement was investigated and dichloromethane showed better results. The Fries rearrangement was carried out in the temperature range of 473–673 K.     

SO2-Assisted Simultaneous Reduction of SO2 and NO by CO on SnO2-TiO2 Solid Solution

Sn_0.5Ti_0.5O₂ shows excellent catalytic performance both for the CO-SO₂ reaction and the CO-SO₂-NO reaction. At 350 ° C, 525 ppm SO₂/520 ppm NO/2085 ppm CO, SV = 3000 h^-1, the conversion of SO₂ is nearly complete in the CO-SO₂ reaction and above 89% in the CO-SO₂-NO reaction; NO conversion is above 98% in the latter reaction. The selectivities of S and N₂ are both close to 100%. SO₂ shows a significant promoting effect on the activity of the Sn_0.5Ti_0.5O₂ catalyst for NO reduction by CO. Combining transient response experiments, catalytic tests and TPD results, we propose a SO₂-assisted NO-CO reaction concept. The existence of a surface sulfur species, which was formed during the CO-SO₂ or CO-SO₂-NO reaction, is proved by XPS analysis. It is the active site for NO reduction in the CO-SO₂-NO reaction, and through which SO₂ accomplishes its promoter role. On the basis of the results obtained, the SO₂-assisted redox mechanism of simultaneous reduction of SO₂ and NO by CO is proposed.     

SO2/O2 dehydrogenation of ethylbenzene

In the SO₂ dehydrogenation of ethylbenzene to styrene using alkalized alumina or titania catalysts, addition of small amounts of oxygen results in (1) higher styrene yields at equivalent SO₂ concentrations, or (2) equivalent styrene yields with lower SO₂ requirements. By staging the oxygen additions, styrene yields of greater than 80% are achieved at SO₂ levels as low as 0.15 mole/mole ethylbenzene when 0.45 mole O₂ is added in increments of 0.15 mole. The low SO₂ concentration and staging of the oxygen result in a high selectivity (94%) for the reaction to styrene by minimizing both byproduct formation and combustion.     

Preparation of core-shell structured Ni2P/Al2O3@TiO2 and its hydrodeoxygenation performance for benzofuran

Highly active Ni₂P catalyst supported on core-shell structured Al₂O₃@TiO₂ for hydrodeoxygenation (HDO) of benzofuran (BF) was prepared and the effect of water on the performance for BF HDO over as-prepared catalyst was studied. The hydrophobic TiO₂ shell can enhance the catalytic activity, water resistance and HDO stability of the Ni₂P/Al₂O₃ catalyst. The Ni₂P/A@T exhibited the highest HDO activity of 95% with O-free products yield of 87%, which is an increase of 40% when compared with that found for Ni₂P/Al₂O₃ (47%).     

The molecular structures and reactivity of V2O5/TiO2/SiO2 catalysts

A series of V₂O₅/TiO₂/SiO₂ catalysts were structurally investigated byin situ Raman spectroscopy and chemically probed by methanol oxidation in order to determine the molecular structure-reactivity relationships of the V₂O₅/TiO₂/SiO₂ catalysts. Only surface TiO _x species are present on the 3% TiO₂/SiO₂ catalysts, and the surface TiO _x species as well as bulk TiO₂ (anatase) particles coexist on the 40% TiO₂/SiO₂ catalyst. The deposition of 1–3% vanadium oxide onto 3% TiO₂/SiO₂ and 4% vanadium oxide onto 40% TiO₂/SiO₂ forms only a surface vanadium oxide phase.In situ Raman studies reveal that the surface vanadium oxide species preferentially exist on the titania sites of the TiO₂/SiO₂ system. The interaction between the surface vanadia and the surface titania overlayer on SiO₂ increases the methanol oxidation reactivity by two orders of magnitude relative to V₂O₅/SiO₂. In the presence of bulk TiO₂ (anatase) particles on the SiO₇ support, the reactivity of the surface vanadia further increases by an order magnitude relative to the catalysts containing only surface titania, and is close to that of surface vanadia on bulk TiO₂. This suggests that the surface VO _x -TiO₂ (bulk) interactions results in a more active site than the surface VO _x -TiO _x -SiO₂ interactions. In addition, the V₂O₅/TiO₂/SiO₂ catalysts exhibit high selectivity towards HCHO because redox sites are predominant on the surface of these catalysts with essentially no acid site present.     

A mesoporous SiO2/TiO2 composite used for various emulsions separation

A mesoporous SiO₂-TiO₂-x composite without any modification was obtained to separate oil-in-water and water-in-oil emulsions solely by gravity. To simulate the actual pollution treatment process in sewage treatment plants, adsorption and degradation properties were studied after the initial emulsion separation. The research result indicates that the reported mesoporous SiO₂ can be employed as an excellent absorbent and catalyst carrier. After light irradiating for 120 min, the degradation efficiency of SiO₂-TiO₂-4 for Rhodamine B, methyl orange, methylene blue, and ciprofloxacin hydrochloride reaches 99.3%, 91.5%, 98.7%, and 96.2%, respectively.     

An Integrated Process of H2O2 Production through Isopropanol Oxidation and Cyclohexanone Ammoximation

The possibility of the integration of the processes of H₂O₂ production through isopropanol partial oxidation and the direct ammoximation of cyclohexanone with H₂O₂ and NH₃ catalyzed by TS‐1 was investigated. The results of isopropanol partial oxidation showed that around 7.5 % yield of H₂O₂ was obtained at 110 °C, 10 atm, 2 h, and after fractionation, a H₂O₂ solution with the typical composition 25.2 wt.‐% H₂O₂, 10.3 wt.‐% isopropanol, 0.29 wt.‐% acetone, 0.45 wt.‐% phosphoric acid and 0.43 wt.‐% acetic acid was obtained. The presence of these impurities up to the above levels did not appreciably influence the ammoximation of cyclohexanone in terms of the conversion of cyclohexanone and the selectivity to cyclohexanone oxime. The results indicate that the processes of H₂O₂ production through isopropanol partial oxidation and the ammoximation of cyclohexanone can be integrated.     

聚丙烯酸酯/TiO2-SiO2纳米杂化材料性能的研究

采用具有核-壳结构的纳米TiO2-SjO2与热固性聚丙烯酸酯原位复合，通过溶胶-凝胶法制得了有机-无机纳米杂化材料，并对材料的结构和性能进行了表征。结果表明：聚丙烯酸酯基纳米SiO2包覆TiO2的有机-无机纳米杂化材料在无机组分质量分数低于8％时是透明的；随着TiO2-SiO2用量的增加，纳米杂化材料的附着力是先增后降，而热稳定性则是逐渐增加；拉伸强度和冲击强度随TiO2-SiO2用量的增加都是先增后降，当TiO2-SiO2质量分数为5．10％时，拉伸强度达到最大值，提高了25％；当TiO2-SiO2质量分数为3．45％时，无缺口冲击强度达到最大值，提高了27％。     

Thermomechanical properties of ceramics in the systems Al2O3-TiO2 and Al2O3-TiO2-mullite

Conclusions We studied certain properties of ceramics in the systems Al₂O₃-TiO₂ and Al₂O₃-TiO₂-mullite, obtained by the use of the double-stage synthesis of aluminum titanate.We established the nature of the change in the high-temperature strength in relation to the ratio of Al₂O₃ and aluminum titanate. The maximum high-temperature strength (bending) at 1200°C is possessed by ceramic with a corundum matrix and a volume proportion of aluminum titanate equal to 40–45%.It is established that the addition of CaO + SiO₂ made in amounts of up to 1.0–1.5% contributes to the partial breakdown of the aluminum titanate in the compositions Al₂O₃-TiO₂ and the production of a ceramic with a bending strength of 160–190 N/mm² at 20–200°C, thermal-shock resistance 650–800°C, and thermal conductivity of 1.9–2.1 W/(m·K).We studied the effect of the mullite concentration on the properties of the ceramic in the system Al₂O₃-TiO₂-mullite. The introduction of mullite in amounts of not more than 50%, containing up to 3% of impurities, contributes to an increase in the ceramic's strength in the range 20–1300°C and in the thermal shock resistance.Translated from Ogneupory No. 2, pp. 22–26, February, 1988.