锰铈脱硝催化剂的制备及其再生性能研究

采用等体积浸渍法制备了一系列Mn-Ce-Ox复合氧化物脱硝催化剂用于NH3选择性催化还原(NH3-SCR)NO。考察了Mn/Ce摩尔比、焙烧温度、H2O和SO2对Mn-Ce-Ox复合氧化物脱硝催化剂活性的影响及催化剂中毒再生性能。结果表明:当NH3:NO=1:1,空速为5 000 h-1,550℃焙烧制得的Mn/Ce摩尔比为5∶1的Mn-Ce-Ox复合脱硝催化剂活性最佳,活性温度窗口为100~260℃,在此温度区间内催化剂活性大于90%。200℃时,Mn-Ce-Ox复合催化剂活性最高为97.84%;在10%(V/V)H2O蒸汽和300×10-6SO2共存条件下,200℃时,催化剂活性在开始反应2.5 h内迅速下降至53%左右,并在之后的6 h内没有明显变化;中毒催化剂经常温水洗再生处理、质量分数为3%的硝酸溶液再生处理和550℃焙烧2 h再生处理后200℃活性均能恢复到90%以上,其中中毒催化剂经质量分数为3%硝酸处理后活性恢复率最高。     

铜前驱体对Cu/SSZ-13催化剂选择性催化氧化NH3性能的影响

采用浸渍法制备了一系列Cu/SSZ-13(X)催化剂,考察不同铜前驱体对催化剂选择性催化氧化氨(NH_3-SCO)性能的影响,并通过ICP、N_2吸附-脱附、XRD、XPS、EPR、UV-Vis、NH_3-TPD和H_2-TPR等手段对催化剂进行物化性质表征.活性测试结果表明,不同铜前驱体制备的Cu/SSZ-13催化剂活性顺序为Cu/SSZ-13(N) Cu/SSZ-13(AC) Cu/SSZ-13(Cl) Cu/SSZ-13(O).其中Cu/SSZ-13(N)具有最佳的低温活性,在200℃反应温度下NH_3转化率达85.5%,且N_2选择性达到80%以上.XRD、EPR和UV-Vis分析表明,CuO和孤立Cu~(2+)是Cu/SSZ-13催化剂的主要铜物种.NH_3-TPD分析表明,以硝酸铜为前驱体制备的Cu/SSZ-13(N)具有更多的酸性位点,有利于提高催化剂的NH_3吸附能力.H_2-TPR结果表明,Cu/SSZ-13(N)的氧化还原性最强,具有最优异的NH_3活化能力,从而使催化剂呈现最好的低温NH_3-SCO活性.     

CFB锅炉环保项目SNCR工艺优化提效研究

某炼化企业自备电厂循环流化床锅炉(简称CFB锅炉)环保项目所采用的脱硝方法为选择性非催化还原脱硝(简称SNCR),使用的还原剂为尿素,SNCR系统投用后,虽然能使NOX排放量显著下降,但尿素用量明显过度,增加了企业脱硝成本,并导致脱硫废水氨氮含量超标。为了应对这一情况,本研究主要通过现场调节锅炉运行参数,以及基于CFD建模的方法研究出高效可靠的SNCR工艺优化调整策略及方法,结果表明:在锅炉燃料煤∶焦=4∶1掺烧比例下,氧含量不宜超过3%,有利于降低NOX生成量;控制减少石灰石量有助于提升NOX的脱除效率;通过模拟计算发现下半部喷枪起到主要的脱硝作用,可适当减少上半部喷枪、提升环下半部喷枪的尿素喷入量来提高脱硝效率。为煤焦混烧CFB锅炉脱硝系统的优化提供指导和借鉴作用。     

MANAGEMENT OF WATER QUALITY IN RELEASES FROM SOUTHWESTERN IMPOUNDMENTS1

ABSTRACT. The objective of this investigation was to determine the selectivity of withdrawal which is possible in southwestern reservoirs. Two stratified flow solutions were examined to test their applicability under field conditions. Although both appeared capable of accurate prediction of the outflow velocity profile, the Bohan-Grace solution, which required less input data, was utilized to predict the chemical constituents of single and simultaneous releases from several southwestern impoundments. Prediction of outflow water quality was within fifteen percent for southwestern reservoirs as shallow as fifty-five feet. The withdrawal layer thickness for the subject Texas impoundments included the entire hypolimnion or epilmnion depending on outlet location. The sensitivity of the velocity profile to seasonal changes, reservoir discharge rate and withdrawal port dimensions also is illustrated.     

Copper complexation by tannic acid in aqueous solution

The speciation of titrated copper in a dissolved tannic acid (TA) solution with an initial concentration of 4 mmol organic carbon (OC)/l was investigated in a nine-step titration experiment (Cu/OC molar ratio = 0.0030–0.0567). We differentiated between soluble and insoluble Cu species by 0.45 μm filtration. Measurements with a copper ion selective electrode (ISE) and diffusive gradients in thin films (DGT) were conducted to quantify unbound Cu(II) cations (‘free’ Cu) and labile soluble Cu complexes. For the DGT measurements, we used an APA hydrogel and a Chelex 100 chelating resin (Na form). Insoluble organic Cu complexes (>0.45 μm) was the dominant Cu species for Cu/OC = 0.0030–0.0567 with a maximum fraction of 0.96 of total Cu. At Cu/OC > 0.0100, Cu-catalysed degradation of aggregate structures resulted in a strong increase of free Cu and (labile) soluble Cu complexes with a maximum fraction of 0.28 and 0.32 of total Cu, respectively. Labile (i.e. DGT-detectable) soluble Cu complexes had a relatively high averaged diffusion coefficient (D) in the APA hydrogel (3.50 × 10⁻⁶– 5.58 × 10⁻⁶ cm² s⁻¹).     

V2O5/AC催化剂对氨还原NO的研究

考察了V2O5/AC催化剂对NH3选择催化还原NO的影响，结果表明，以浓硝酸预氧化处理的活性焦为载体对催化剂活性有很大提高，这是由于浓硝酸预氧化后，活性焦表面产生了较多的含氧官能团可能吸附更多的NH3,并且提高了活性组分V2O5的含量，反应气氛中加入SO2后，二都活性都增加，但差异消失，这是由于SO2存在时，反应生成的SO4^2-离子的酸性强于浓硝酸预氧化产生的含氧官能团的酸性，催化剂在使用前经过煅烧和氧化对催化剂活性有很大改善。SO2存在时，V2O5含量为1wt%的催化剂活性提高。     

Ag/Cu3(BTC)2复合催化剂的制备及其NH3-SCR催化性能

采用紫外还原的方法成功制备出Cu₃（BTC）₂（均苯三甲酸合铜）负载贵金属Ag纳米颗粒的Ag/Cu₃（BTC）₂复合催化剂,并用于氨法脱硝反应.应用X射线衍射（XRD）、透射电子显微镜（TEM）、BET测试等手段对催化剂的物理化学性能进行了表征.结果发现Ag纳米颗粒以球状结构高度均匀分散在Cu₃（BTC）₂骨架结构的表面.负载Ag纳米颗粒和Cu-MOF的协同作用,提高了Ag/Cu₃（BTC）₂催化剂的脱硝效率,负载量为15wt%的催化剂表现出最优脱硝效率,在220～260℃达到100%的NO转化率.同时,利用in-situ FTIR技术对NH₃-SCR的反应机理进行了探究.     

Pd/CeZr/TiO2/Al2O3蜂窝状金属丝网催化剂选择催化还原NOX

采用溶胶-凝胶法和浸渍法制备了Pd/CeZr/TiO2Al2O3蜂窝状金属丝网催化剂,并将其应用于在富氧条件下以丙烯选择催化还原NOx的研究.利用扫描电镜(SEM)分析了钛酸四丁酯的含量以及涂敷次数对TiO2涂层的影响,系统地考察了Pd含量、氧气浓度和空速对蜂窝状金属丝网催化剂催化性能的影响.实验结果表明,采用钛酸四丁酯的含量为20.0%的溶胶,涂敷2次,可以在金属丝网载体上氧化铝涂层表面获得均匀、无皲裂的TiO2涂层;Pd含量在0.23%～1.06%的范围内, NOx的转化率随Pd含量的增加而减小, Pd含量为0.23%时, NOx表现最高的NOx转化率;反应气体中氧气浓度从1.5%增加到6.0%, NOx的转化率随氧气浓度的增加而增大,当氧气浓度高于6.0%, NOx的转化率则随氧气浓度的增加而迅速减小; NOx的转化率随着空速的增加而降低,在高温条件下空速对转化率的影响要大于在低温条件下.     

Selective sorption of perfluorooctane sulfonate on molecularly imprinted polymer adsorbents

Perfluorooctane sulfonate (PFOS), as a potential persistent organic pollutant, has been widely detected in water environments, and has become a great concern in recent years. PFOS is very stable and difficult to decompose using conventional techniques. Sorption may be an attractive method to remove it from water. In this study, the molecularly imprinted polymer (MIP) adsorbents were prepared through the polymerization of 4-vinylpyridine under different preparation conditions in order to remove perfluorooctane sulfonate (PFOS) from water. The MIP adsorbents using perfluorooctanoic acid (PFOA) as the template had good imprinting effects and could selectively remove PFOS from aqueous solution. The sorption behaviors including sorption kinetics, isotherms, and effect of pH, salt, and competitive anions were investigated. Experimental results showed that the sorption of PFOS on the MIP adsorbents was very fast, pH-dependent, and highly selective. The achieved fast sorption equilibrium within 1 h was attributed to the surface sorption on the fine adsorbents. The sorption isotherms showed that the sorption selectivity of PFOS on the MIP adsorbents decreased at high PFOS concentrations, which may be due to the double-layer sorption and the formation of PFOS micelles on the sorbent surface. The sorption of PFOS on the MIP adsorbents was mainly dominated by the electrostatic interaction between the protonated vinylpyridine on the adsorbent surface and the anionic PFOS. The prepared MIP adsorbents can potentially be applied in water and wastewater treatment for selective removal of PFOS.     

Synthesis, characterization, and adsorption performance of Pb（Ⅱ）-imprinted polymer in nano-TiO2 matrix

Surface ion-imprinted in combination with sol-gel process was applied to synthesis a new Pb(II)-imprinted polymer for selective separation and enrichment of trace Pb(II) from aqueous solution. The prepared material was characterized by using the infrared spectra, X-ray di ractometer, and scanning electron microscopy. The batch experiments were conducted to study the optimal adsorption condition of adsorption trace Pb(II) from aqueous solutions on Pb(II)-imprinted polymer. The equilibrium was achieved in approximately 4.0 h, and the experimental kinetic data were fitted the pseudo second-order model better. The maximum adsorption capacity was 22.7 mg/g, and the Langmuir equation fitted the adsorption isotherm data. The results of selectivity experiment showed that selectively adsorbed rate of Pb(II) on Pb(II)-imprinted polymer was higher than all other studied ions. Desorption conditions of the adsorbed Pb(II) from the Pb(II)-imprinted polymer were also studied in batch experiments. The prepared Pb(II)-imprinted polymer was shown to be promising for the separation and enrichment of trace Pb(II) from water samples. The adsorption and desorption mechanisms were proposed.