在硫酸化氧化物催化剂上二氯甲烷的低温催化降解

采用色谱微反联用技术研究了在硫酸化氧化物催化剂上二氯甲烷的低温催化降解。实验发现，硫酸化氧化物催化剂如ＴｉＯ２－（ＳＯ４）在较低反应温度（如２７５℃）时表现出较高的反应活性，转化率１００％，并且其催化活性次序为：ＴｉＯ２－（ＳＯ４）＞ＺｒＯ２－（ＳＯ４）＞ＣｅＯ２－（ＳＯ４）。实验结果还表明：催化剂的酸性关联降解二氯甲烷的催化活性。同时，水汽的存在明显降低了其催化活性。     

Catalytic decomposition of nitrous oxide over perovskite type solid oxide solutions and supported noble metal catalysts

The catalytic decomposition of nitrous oxide to nitrogen and oxygen has been investigated over various solid oxide solutions (SOS), La_0.8Sr_0.2MO_3– (M=Cr, Fe, Mn, Co or Y), La_1.8Sr_0.2CuO_4– and supported Pd, Pt catalysts. The reaction was carried out in a gradientless recycle reactor at 1 atm pressure with a feed gas containing about 0.5% N₂O (in helium). Among the various solid solutions, La_0.8Sr_0.2CoO_3– showed a maximum N₂O conversion of 90% at 600C. The order of activity observed for N₂O decomposition was La_0.8Sr_0.2CoO_3–>La_0.8Sr_0.2FeO_3–>La_1.8Sr_0.2CuO_4–> La_0.8Sr_0.2MnO_3–La_0.8Sr_0.2CrO_3–La_0.8Sr_0.2YO_3–. The activity of La_0.8Sr_0.2CoO_3– was compared with supported Pd, Pt and also with unsubstituted LaCoO₃ catalysts under similar reaction conditions. Among all the catalysts tested in this study, Pd/Al₂O₃ showed the lowest light-off temperature for N₂O decomposition. The activity of La_0.8Sr_0.2CoO_3– was found to be comparable to Pd/Al₂O₃ catalyst at temperatures above 500 C. The influence of added oxygen (about 4%) in the feed was examined over La_0.8Sr_0.2CoO_3– and Pd/Al₂O₃ catalysts and only in the case of cobalt catalyst was the conversion of N₂O decreased by 13%. By choosing varied sintering conditions, La_0.8Sr_0.2CoO_3– of different BET surface areas were prepared and the light-off temperature was found to decrease with increase in surface area. The results obtained over solid solutions are discussed on the basis of the cation mixed valency and oxygen properties of the catalyst.     

Catalytic decomposition of nitric oxide by perovskites

Catalytic decomposition of nitric oxide has been studied for nearly a century, using materials ranging from noble metals to alkaline earth metal oxides, without much success. Only since about last fifteen years some progress in finding promising materials has been made. Of the numerous catalyst systems studied, very few show tangible decomposition rates : copper substituted zeolites, silver-cobalt mixed oxides, some perovskites, and supported noble metals. Although at 773 K the rates of decomposition over zeolites are two to three orders higher than those over remaining systems, these materials have very low thermal stability, above 773 K. In this respect, perovskites have much higher potential, although so far no composition exhibiting practical decomposition rates has been found. Systematic study of the effect of composition on the performance should help to advance the complete understanding of this important reaction. In this paper a current state of art is outlined, and some latest preliminary results for new specially formulated perovskites are presented.     

过渡金属氧化物催化剂对丙酮氧化的催化性能

以氧氯化锆和过渡金属硝酸盐为原料,溶胶-凝胶法制备氧化锆载体,采用溶液浸渍法制备出负载型纳米复合氧化物催化剂。对过渡金属氧化物(Mn、Ni、Cu、Fe和Co)催化剂进行初步筛选,其中Mn₂O₃/ZrO₂催化活性最佳。考察了活性组分含量、焙烧温度和焙烧时间等对催化剂催化活性的影响。催化剂的最佳制备条件：锰负载量为6%,450 ℃焙烧6 h。丙酮的转化率达62%。通过TEM、SEM、XRD和TG-DTA对催化剂结构进行了表征。结果显示,催化剂颗粒均匀,大小约为20 nm;无定形的Mn2O3是催化剂的活性中心。     

Physicochemical investigation of chemical paint removers: Interactions of methylene chloride with polyurethane coatings

A variety of thermal and spectroscopic techniques have been used to investigate interactions of the widely-used paint-stripping solvent methylene chloride upon model polyurethane coatings. Thermal analysis reveals that methylene chloride penetrates and swells the polymer film and leads to a slight depression in the glass transition temperature (T_g) after drying. The ¹H NMR spectra and T₁ and T_1ρ relaxation times show that methylene chloride is responsible for increased polymer segmental motion in the polymer due to swelling, and indicate intimate contact between the methylene chloride molecules and the polymer, with no liquid-like pools of the solvent observed. The quadrupolar-echo ²H NMR spectra of CD₂Cl₂ in the polyurethane over a temperature range of 24 °C to −27 °C reveal a lengthening of the rotational correlation times of the methylene chloride by over four orders of magnitude compared to the neat liquid, indicating restricted mobility due to an interaction with the polymer. Although this interaction is likely due to the electric dipoles in the solvent and the polymer backbone, the absence of significant residual nuclear quadrupole couplings due to a high degree of ordering or solvent immobilization shows that the interaction strength is weak compared to thermal energy (kT). Raman spectroscopy indicates that methylene chloride causes swelling by interacting with the carbonyl group responsible for inter-chain bonding, thus permitting dilation. FTIR and Raman spectroscopy demonstrated that methylene chloride leads to no irreversible chemical changes in the coating. A common cellulosic chemical stabilizer used in commercial paint removers has been found by XPS to deposit as a thin conformal but heterogeneous coating on the surface of the polymer, suggesting a possible important function to retard evaporation while allowing some permeation.     

Catalytic degradation and dechlorination of PVC-containing mixed plastics via Al-Mg composite oxide catalysts

A alumina-magnesium composite oxide catalyst (Al-Mg) was synthesized for catalytic degradation of poly vinyl chloride (PVC) containing polymer mixtures, i.e. polypropylene (PP)/PVC, low-density polyethylene (LDPE)/PVC, polystyrene (PS)/PVC, and LDPE/PP/PS/PVC. In the catalytic degradations the Al-Mg composite oxide catalyst accelerated the rate of polymer degradation and lowered the carbon distribution of liquid products. In addition, it showed good effect on the fixation of evolved HCl and greatly decreased the chlorine content in the oil. These results suggested that the Al-Mg composite oxide catalyst can be effectively used for catalytic degradation and dechlorination of PVC-containing mixed plastics.     

Conversion of used vegetable oils to liquid fuels and chemicals over HZSM-5, sulfated zirconia and hybrid catalysts

Thailand’s food manufacturing uses about 47 Million liters per year of vegetable oil. Used vegetable oil is classified as waste, but has potential for conversion into liquid fuel. This research studied the catalytic conversion of used vegetable oil to liquid fuel, where investigation was performed in a batch microreactor over a temperature range of 380–430 °C, initial pressure of hydrogen gas over 10–20 bars, and reaction time of 45–90 minutes. Catalysts such as HZSM-5, Sulfated Zirconia and hybrid of HZSM-5 with Sulfated Zirconia were used to determine the conversion and yield of gasoline fraction. The major products obtained were liquid products, hydrocarbon gases and small amounts of solids. Liquid products were analyzed by simulated distillation gas chromatograph and the product distribution was obtained. Hybrid catalyst HZSM-5 with Sulfated Zirconia showed the highest yield of gasoline with a 26.57 wt% at a temperature of 430 °C, initial hydrogen pressure at 10 bars, and reaction time of 90 minutes in the ratio of hybrid HZSM-5 with Sulfated Zirconia at 0.3: 0.7.     

二氯甲烷在CrO3／Al2O3和Pd／Al2O3催化剂上的催化氧化

二氯甲烷在ＣｒＯ_３／Ａｌ_２Ｏ_３和Ｐｄ／Ａｌ_２Ｏ_３催化剂上的催化氧化张立庆（杭州应用工程技术学院化工系杭州３１００１２）姜玄珍，莫亦平（浙江大学化学系杭州３１００２７）关键词二氯甲烷；催化降解；负载型催化剂１引言随着有机化工，氯制品化工的迅速发展?..     

Cu-Mn氧化物催化N_2O直接分解性能

分别以Cu(NO_3)_2·3H_2O和50%Mn(NO_3)_2水溶液为铜源和锰源,K_2CO_3为沉淀剂,采用沉淀法和共沉淀法制备单一Cu、Mn氧化物催化剂和Cu-Mn-O复合氧化物催化剂,用于催化N_2O直接分解反应,并利用N_2物理吸附-脱附、XRD、FT-IR和TPR等进行表征。结果表明,单一Cu和Mn氧化物分别以体相CuO和Mn2O_3物相形式存在,Cu-Mn-O复合氧化物中除形成CuMn_2O_4尖晶石物相外,还有一定量小晶粒CuO,较单一氧化物具有更加优异的还原性能,表现出较高的催化N_2O直接分解活性。在空速10 000 h~(-1)和N_2O体积分数0.1%条件下,Cu-Mn-O复合氧化物催化剂可在440℃催化N_2O完全分解,分别较单一Cu和Mn氧化物催化剂降低了40℃和60℃。     

Catalytic activity of hydrodesulfurization catalysts prepared by two methods

Two sets of samples, ranging from molybdenum sulfide to cobalt sulfide, were prepared by two different methods: homogeneous sulfide precipitation (HSP), and a new preparation method of CoMo and NiMo bulk sulfides, called impregnated thiosalt decomposition (ITD). Hydrodesulfurization of thiophene was measured at temperatures between 533 K and 593 K in a conventional flow system. The products were analyzed by gas chromatography. Both sets of samples (HSP and ITD) present the typical volcano curve of specific activity with larger values for catalysts prepared by HSP than those by ITD. Samples prepared by ITD present comparable intrinsic activities than those prepared by HSP. Activation energies for both methods of preparation are larger for promoted catalysts with a value of 23 for HSP and 12.6 kcal/mol for ITD.     

NO分解催化剂的研究进展

直接催化分解被公认是消除NO污染最有吸引力的方法。从贵金属、金属氧化物、复合氧化物和Cu-ZSM-5分子筛等方面综述了国内外有关NO催化分解的研究进展。指出了NO催化分解催化剂研究中存在的问题及其发展方向。     

一种新的氯化钠热化学分解循环

提出了一种新的氯化纳热分解循环,研究了循环中各主要化学反应的适宜条件,并从热力学计算出了循环体系中能量流动过程,用ＴＧ法研究了循环中多相反应的动力学问题,实验和理论证明了该循环具有很大的节能优势,有取代传统电解法的广阔前景。     

负载型钴锰复合金属氧化物催化剂催化分解N_2O

以ZrO_2为载体,采用浸渍法制备负载型钴锰复合金属氧化物催化剂,研究催化剂活性组分负载量、Co与Mn物质的量比、焙烧条件及含H_2O气氛对N_2O转化率的影响。结果表明,催化剂最佳制备条件为:活性组分Co负载质量分数3%,Co与Mn物质的量比为1∶1,焙烧升温速率2℃·min-1,焙烧温度900℃。该条件制备的负载型钴锰复合金属氧化物催化剂在反应温度850℃时,N_2O转化率达98.7%。当反应气氛中H_2O体积分数小于20%条件下,850℃时N_2O转化率高于90%,表明催化剂具有较强的抗水性能。     

Degradation of cationic dye methylene blue by ozonation assisted with kaolin

An enhanced ozonation process, methylene blue (MB) wastewater treated by MnO₂/O₃ assisted with kaolin in a slurry reactor, at room temperature and atmospheric pressure, MB wastewater can be effectively purified, a chemical oxygen demand (COD) of 88.3% and a decoloration rate of 98.9% were obtained in 10 min at pH 11. Compared with MnO₂/O₃ catalytic ozonation (16.0% of decoloration and 33.3% of COD reduction), decoloration and COD reduction were markedly increased, indicating that kaolin can significantly improve the catalytic ozonation process. According to the experimental results, the hypothetical mechanism of degradation and the reaction kinetics were also proposed. COD reduction can be described by a second-order model and the reaction rate constant in the presence of kaolin was higher than that of absence of kaolin.     

Ce-Zr-V-O复合氧化物对二氯甲烷催化燃烧性能

用共沉淀法制备不同铈锆比及V掺杂量的Ce-Zr-V-O复合氧化物催化剂,在常压固定床反应器上对复合氧化物催化剂用于二氯甲烷催化燃烧的活性进行评价,采用BET、XRD、XPS和H₂-TPR等方法对复合氧化物催化剂进行表征。结果表明,V与Ce-Zr形成了Ce-Zr-V-O固溶体,V掺杂提高了催化剂的比表面积和孔径,形成了更多的晶格缺陷和活性中心,使催化剂具有更高的催化活性和稳定性。n(Ce)∶n(Zr)∶n(V)=7∶3∶0.5时,Ce_0.7Zr_0.3V _0.05 O _2-λ催化剂活性最好,小于300 ℃,连续反应200 h,二氯甲烷转化率大于98%。     

Catalytic decomposition of biomass tars with iron oxide catalysts

Catalytic gasification of wood (Cedar) biomass was carried out using a specially designed flow-type double beds micro reactor in a two step process: temperature programmed non-catalytic steam gasification of biomass was performed in the first (top) bed at 200–850 °C followed by catalytic decomposition gasification of volatile matters (including tars) in the second (bottom) bed at a constant temperature, mainly 600 °C. Iron oxide catalysts, which transformed to Fe₃O₄ after use possessed catalytic activity in biomass tar decomposition. Above 90% of the volatile matters was gasified by the use of iron oxide catalyst (prepared from FeCl₃ and NH_3aq) at SV of 4.5 × 10³ h^?1. Tar was decomposed over the iron oxide catalysts followed by water gas shift reaction. Surface area of the iron oxide seemed to be an important factor for the catalytic tar decomposition. The activity of the iron oxide catalysts for tar decomposition seemed stable with cyclic use but the activity of the catalysts for the water gas shift reaction decreased with repeated use.     

A pilot plant study for catalytic decomposition of PCDDs/PCDFs over supported chromium oxide catalysts

Chromium oxide catalysts supported on TiO₂ and Al₂O₃ were examined in a fixed-bed flow reactor system for the removal of PCE (perchloroethylene), a simulant of 2,3,7,8-TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), and in a pilot plant employing actual flue gas from a sintering plant for the removal of PCDDs/PCDFs (poly-chlorinated dibenzo-dioxin/poly-chlorinated dibenzo-furan). The 12.5 wt.% chromium oxides supported on TiO₂ and Al₂O₃ revealed excellent stability and performance of PCE removal in the feed gas stream containing water vapor. In a pilot plant study, the catalysts washcoated on the honeycomb reactor revealed 93–95% of PCDDs/PCDFs removal activity over CrO_x/Al₂O₃-HC20 (CrO_x/Al₂O₃ catalyst washcoated on 20 cell-honeycomb), and more than 99% of the decomposition activity over CrO_x/TiO₂-HC20 (CrO_x/TiO₂ catalyst washcoated on 20 cell-honeycomb) at 325 °C and 5000 h⁻¹ of reactor space velocity without the de novo synthesis of PCDDs/PCDFs. In particular, CrO_x/TiO₂-HC20 showed 94% of PCDDs/PCDFs decomposition activity even at 280 °C reaction temperature. The catalyst also exhibited significant NO removal activity. The chromium oxide seems to be a promising catalyst for the removal of PCDDs/PCDFs and NO_x contained in the flue gas.     

复分解法氯化铵生产中冷却结晶过程研究

研究了硝酸铵和氯化钾复分解法制取氯化铵的冷却结晶过程,考察了降温速率、搅拌速率、晶种添加量等因素对氯化铵产品的纯度及晶体粒度分布的影响。研究结果表明,采取适宜的降温速率、搅拌速率及适宜的晶种添加能有效地改善氯化铵晶体粒度,提高分离效果;氯化铵冷却结晶适宜操作条件为：降温速率为0.3 K/min、搅拌速率为350 r/min、添加晶种粒度为150~180 μm、添加晶种量为1.88%,在此条件下制得的氯化铵产品晶体粒度均一性好,平均粒径更大。     

Catalytic decomposition of HCFC22 (CHClF2)

The catalytic decomposition of CHClF₂ was studied over various acidic metal oxides in a fixed-bed reactor. The Cr₂O₃ZrO₂ exhibited the highest activity. The presence of water vapor in the reaction system suppresses the transformation of oxides to fluorides, progresses the formation of CO₂, and it improves the catalysts life.     

Effects of methane and oxygen on decomposition of nitrous oxide over metal oxide catalysts

Catalytic activities of various metal oxides for decomposition of nitrous oxide were compared in the presence and absence of methane and oxygen, and the general rule in the effects of the coexisting gases was discussed. The reaction rates of nitrous oxide were well correlated to the heat of formation of metal oxide, i.e., a V-shaped relationship with a minimum at −ΔH_f⁰ around 450 kJ (O mol)⁻¹ was observed in N₂O decomposition in an inert gas. In the case of metal oxides having the heat of formation lower than 450 kJ (O mol)⁻¹, CuO, Co₃O₄, NiO, Fe₂O₃, SnO₂, In₂O₃, Cr₂O₃, the activities were strongly affected by the presence of methane and oxygen. On the other hand, the activities of TiO₂, Al₂O₃, La₂O₃, MgO and CaO were almost independent. The reaction rate of nitrous oxide was significantly enhanced by methane. The promotion effect of methane was attributed to the reduction of nitrous oxide with methane: 4N₂O+CH₄→2N₂+CO₂+2H₂O. The activity was suppressed in the presence of oxygen on the metal oxides having lower heat of formation. On the basis of Langmuir–Hinshelwood mechanism, the effect of oxygen on nitrous oxide decomposition was rationalized with the strength of metal–oxygen bond.