Investigation on preparation of CuO-SnO2 -CeO2γ-Al2O3 catalysts for catalytic wet air oxidation process and their catalytic activity for degradation of phenol

Catalytic Wet Air Oxidation process is an efficient measure for treatment of wastewater with great strength which is not biodegradable. Heterocatalysts now become the key investigation subject of catalytic wet air oxidation process due to their good stability and easy separation. In the paper, CuO-SnO2-CeO2/γ-Al2O3 catalysts are prepared by impregnation method, with SnO2 as a doping component, CuO as an active component, CeO2 as a structure stabilizer, γ-Al2O3 as a substrate. XPS test is carried out to investigate the effect of Sn on the chemical surrounding of Cu and O element on the catalyst surface and their catalytic activity. It is shown that the right doping of Sn can increase Cu content on the catalyst surface, as a result the quantity of adsorption oxygen is also increased. It is found that Cu content on the catalyst surface is one of the primary factors that determin catalytic activity of catalyst through analyzing the catalytic wet air oxidation process of phenol.     

Selective catalytic reduction of NO with NH3 over sol-gel-derived CuO-CeO2-MnOx/γ-Al2O3 catalysts

Granular CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH₃ and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO₂-MnO _x /γ-Al₂O₃ catalysts is 300–400 °C. The catalysts maintain nearly 100% NO conversion at 350 °C. The °C NH₃ oxidation experiments show that both NO and N₂O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH₃, which improves the denitrification activity at low temperature. The over-oxidation of NH₃ at high temperature is the main cause leading to a decrease in the NO conversion. The NH₃ and NO desorption experiments show that NH₃ and NO can be adsorbed on CuO-CeO₂-MnO _x /γ-Al₂O₃ granular catalysts. The transient response of NH₃ and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process. Foundation item: Projects (50776037, 50721005) supported by the National Natural Science Foundation of China     

Effects of drying method on preparation of nanometer α-Al2O3

Ammonium aluminum carbonate hydroxide （AACH） precursor was synthesized by the precipitation reaction of aluminum sulfate and ammonium carbonate. Then the precursor was dealt with five drying methods including ordinary drying, alcohol exchange, vacuum freeze-drying, glycol distillation, n-butanol azeotropic distillation respectively and calcined at 1 200℃ for 2 h to get α-Al2O3. The effects of drying methods on preparation of nanometer α-Al2O3 were discussed, and the optimal drying method was confirmed. The structural properties of powders were characterized by XRD, SEM and BET measurements. The results show that vacuum freeze-drying, glycol distillation and n-butanol azeotropic distillation can prevent the powders from aggregating, and among them the n-butanol azeotropic distillation is the best method. The nanometer α-Al2O3 powder with non-aggregation can be manufactured using n-butanol azeotropic distillation and the average particle size is about 40 nm.     

Effect of anions on preparation of ultrafine α-Al2O3 powder

Ultrafine alumina power was obtained by calcining the precursor at 1 200 ℃ for 2 h, which was prepared by homogeneous precipitation method using aluminium salts and urea as raw materials. The effects of anions on the morphology, particle size, surface area and configuration of the precursors were studied. The results show that the reactions of urea with aluminium nitrate and aluminium chloride result in agglomerates gels with bad filtering performance, the morphology is fibrillar. Aluminium sulphate-urea reactions result in the direct formation of amorphous powders with good filtering performance, of which morphology are regular spherical particles with larger granularity and smaller surface area. The reaction of mutual compound of aluminium sulphate and aluminium nitrate with molar ratio of 40:60 with urea can produce precursor with good filtering performance, spherical morphology, and uniform granularity distribution in the particle size range of 2-3 μm.     

ZnO/γ-Al2O3和CuO/γ-Al2O3催化剂表面酸碱性的研究

文章研究了不同担载量的ZnO或CuO改性的γ-Al2O3样品的酸碱特性以及焙烧温度的影响,并用吸附量热技术测定了其表面酸碱位的强度和数量。     

Sulfation behavior of CuO/γ-Al2O3 sorbent for the removal of SO2 from flue gas

CuO/γ-Al2O3 has been considered as a promising and recycling sorbent to remove sulfur dioxide from flue gas. In this study, a series of CuO/γ-Al2O3 sorbents with different CuO loadings were prepared by impregnation. The monolayer coverage of CuO supported on γ-Al2O3 determined by X-ray quantitative analysis was 0.275 g CuO/g （γ-Al2O3）. Below the monolayer coverage, CuO was found highly dispersed on γ-Al2O3. Thermogravimetric technique was used to study sulfation kinetics and sulfation recycling. It was found that the Langmuir kinetic adsorption model described well the experimental data at the rapid sulfation region of the CuO/γ-Al2O3 sorbent. The adsorption activation energy was 19.98 kJ/mol and the pre-exponential factor was 9.97× 10^-5 s^-1.Pa^-1. The CuO/γ-Al2O3 sorbent has shown good performance on regeneration, but long sulfation time might cause the deactivation of the CuO/γ-Al2O3 sorbent. It was also seen that the sulfated γ-Al2O3 support could not be reduced at 400℃.     

Investigation on the thermal decomposition of aged La2O3

The thermal decomposition process of air-aged La203 in argon atmosphere was studied using nonisothermal TG-DSC. X-ray diffraction and TG-DSC analysis showed that the aged powder was composed of La（OH）3 with small amounts of oxycarbonate. The decomposition process of air-aged La2O3 involves the two-step decomposition of La（OH）3 and the decomposition of oxycarbonate. The kinetic analysis of the two-step decomposition of La（OH）3 was carried out using Coats-Redfern and isoconversion （Ozawa） methods. The kinetics of the two-step decomposition can be described in terms of the nucleation and growth model A （m=1.5, m is the model parameter） and A （m=2.5）, respectively. The apparent activation energy for the first step is 136-144 （Coats-Redfern） and 137-164 kJ/mol （isoconversion）. The apparent activation energy for the second step is 191-194 （Coats-Redfern） and 186-213 kJ/mol （isoconversion）.     

Microstructure and isothermal oxidation of 3Al2O3·2SiO2/SiC coating on high and low density carbon-carbon composites

Carbon-carbon composite (C/C) materials are prone to severe oxidation and volatilization problems. To address these issues, mullite (3Al2O3·2SiO2 )/silicon carbide (SiC) coatings were deposited on C/C composite substrates characterized into high and low densities. The coatings were applied by a two-step approach: pack cementation and silica sol based slurry coating processes. The relationship between the microstructure of 3Al2O3·2SiO2 /SiC coatings and C/C substrates during isothermal oxidation cycle at 1 500 oC was investigated using X-ray diffractometer (XRD) and scanning electron microscope (SEM) mounted with energy dispersive spectrometer (EDS). The results indicate that the density of the substrates has a marked effect on the coatings. Dense, thick and well-bonded coatings are obtained in the high density substrate. After 106 h of isothermal oxidation, the high density substrate with 3Al2O3·2SiO2 /SiC coating offers effective protection as compared to low density substrate suffering recession.     

Effect of nucleating agents on microstructure and mechanical properties of SiO2-Al2O3-ZrO2 glass-ceramics

SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength （120 MPa） than others.     

Preparation and characterization of hydroxyapatite/γ-Fe2O3 hybrid nanostructure

The hybrid particles composed of hydroxyapatite (HAp) and ferrite (γ-Fe₂O₃) were synthesized by two-step precipitation method. The effect of reaction temperature on the morphology of the hybrids was also studied. The resultant hybrids were characterized by transmission electron microscopy (TEM) and X-ray diffraction analysis(XRD). It was found that γ-Fe₂O₃ nanoparticles dispersed within the HAp matrix and these hybrids had a feather-like or spherical morphology when synthesized at 90 °C or room temperature, respectively. The magnetic properties of the hybrid showed good superparamagnetic feature, and they could be controlled by the external magnetic field.     

Preparation, characterization and photocatalytic behavior of WO3-TiO2/Nb2O5 catalysts

TiO2/Nb2O5 photocatalyst loaded with WO3 (WO3-TiO2/Nb2O5) was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiO2/Nb2O5 by using Fe3 as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 μmol/(L·h).     

Preparation and characterization of V-K catalysts supported on porous α-alumina ceramic substrate for diesel soot oxidation

The V-K catalysts were produced on porous α-alumina substrate by a solution impregnation route and the compositions and catalytic activities for soot oxidation were studied by XRD, TG/DTG, DSC and TPR. According to the catalytic activity studies, the catalytic activity of the crystalline phases is in the order: KNO₃+KVO₃>K₃V₅O₁₄+KVO₃. The appearance of excessive KHCO₃ phase will lead to the deterioration of catalytic activity when the catalysts contain higher KNO₃ content. It is also found that when the K:V molar ratio is higher than 1:1, the prepared catalysts show a strong CO₂ absorption characteristic and this behavior will become gradually significant with the increasing of K:V molar ratio. Considerable amount of absorbed CO₂ are strongly bonded to the crystal lattice with onset desorption temperature of 200 °C.     

Cu-MgO/γ-Al2O3丙酮一步法合成甲基异丁基酮

采用等孔体积浸渍法制备Cu MgO/γ Al2O3丙酮常压气相加氢制MIBK催化剂.通过XRD及BET表面积测定表征催化剂.研究碱性组分及反应条件对转化率和选择性的影响,经筛选得到催化剂体系的最佳组成为:wCu=4%,wMgO=5%,适宜的反应条件为:常压,200℃,H2/丙酮摩尔比为2.5,进料速率为1.5ml·h-1·g-1cat.在该条件下,丙酮转化率达65.26%,MIBK选择性达57.49%.     

微湿空气法处理SiO2/γ-Al2O3催化剂制润滑油基础油

利用微湿空气法对SiO2／γ-Al2O3催化剂进行处理,将其用于制取润滑油基础油。利用BET法对催化剂的结构进行测定,考察了微湿空气处理催化剂的最佳处理条件及活性组分的最佳负载量,在微型反应装置上应用该催化剂进行了α-烯烃聚合反应实验。结果表明,采用温度为170℃,压力为6．0 MPa,体积空速为0．5 h-1的最佳聚合工艺条件,微湿空气温度为45℃,处理温度为800℃,活性组分的质量分数为12％时,催化剂具有较好的催化活性和优良的经济性。润滑油的运动粘度为38．19 mm2／s,溴价为5．78 g(Br)／100 g,凝点为-43．0℃。     

纳米CeNi/γ-Al2O3加氢催化剂的活性与稳定性

以甲苯气相加氢反应为探针,在微反-色谱装置上测定了纳米CeNi/γ-Al2O3加氢催化剂的活性和稳定性.通过TEM和DSC-TG对催化剂进行了表征.实验证明:纳米CeNi/γ-Al2O3加氢催化剂比工业用加氢催化剂节约活性组分约70%,经1 200 h连续运转后,甲苯加氢转变为甲基环己烷的转化率仍保持在99%以上,表明该纳米加氢催化剂具有很高的加氢活性和良好的稳定性.     

Na-KOH/γ-Al2O3型固体超强碱催化剂的性能研究

对Na KOH/γ Al2O3型固体超强碱催化剂的催化性能进行了研究,以VNB异构化为ENB的反应为例证明:该固体碱具有很高的催化活性,可使VNB异构化为ENB的转化率达到近100%,反应选择性也接近100%.     

Preparation,characterization of superacid SO4 2−/ZrO2-SiO2 and its activity on catalytic synthesis of methyl p-nitrobenzoate

Solid superacid SO42-/Zr O2-SiO2 was prepared by dip-impregnation method, and its catalytic activity was tested with esterification of p-nitrobenzoic acid and methanol. The optimum conditions were also found, that is, the molar ratio between silica and zirconia was 10:1, the calcination temperature was 550 ℃ and the soaked consistency of H2SO4 was 1.0 mol?L-1. Under the conditions that the ratio of methanol to acid(m L/g) was 12:1, the amount of catalyst was 0.5 g, the reaction time was 5 h and the stirring speed was 800 r?min-1, the yield of methyl p-nitrobenzoate could reach up to 90.5%. Then the characterizations of cataslyst, including the acidity and types of acidic centers, specific surface area and surface structure was respectively examined by Hammett indicator, in-situ pyridine IR, BET method, FT-IR(KBr), transmission electron microscope(TEM), and X-ray diffraction(XRD). The results showed that the catalyst SO42-/Zr O2-SiO2 was superacid with high specific surface area due to Ho-12.70. It contained acidic sites of Lewis and BrΦnsted, and its surface structure changed after esterification. The zirconia crystal was mainly tetragonal and silica crystal was not found.     

Preparation and Gas Permeation of Supported γ-Al2O3 Membranes Used as Substrate Layer for Microporous Membranes

γ-Al₂O₃ membranes were successfully deposited on the top of porous α-Al₂O₃ support by sol-gel process and characterized by means of XRD, SEM, N₂ adsorption and gas permeation. The γ-Al₂O₃ membranes, free of pin-holes and cracks, adhere tightly to the supports and have a thickness of about 7 μm. When sintered at 400°C, γ-Al₂O₃ membranes have a narrow pore size distribution, with a pore diameter of 3.6nm, and the transport of both H₂ and CO₂ in supported γ-Al₂O₃ membrane is governed by Knudsen mechanism, with H₂ permeance of 3.3×10⁻⁶ molm⁻² Pa⁻¹ s⁻¹ and H₂/CO₂ permselectivity close to the ideal Knudsen value at 50°C. The γ-Al₂O₃ membranes are suitable for being used as the substrates of microporous membranes. Founded by the Doctor Science Foundation of Chinese Education Ministry (Grant No. 98053301).