等离子体改性提高PTMSP膜氧氮选择性

膜材料中迄今以聚三甲基硅基丙炔(PTMSP)的透气速率最大,其氧透过速率比PDMS高一个数量级,但氧氮分离系数小,透气性不稳定。改性PTMSP,以提高其透气选择性和透气速率稳定性引起人们的极大关注。本文报道,在外极管式电容耦合反应器中,

大鼠创伤性脑损伤后选择性诱导型一氧化氮合酶抑制剂AG对神经功能影响的实验研究

目的 :研究选择性诱导型一氧化氮合酶 (i NOS)抑制剂 AG在大鼠创伤性脑损伤 (TBI)模型中对大鼠伤后神经功能的影响。方法 :30只 SD大鼠随机分为假创伤性脑损伤组、创伤性脑损伤组、选择性诱导型一氧化氮合酶抑制剂 (NOSI) AG组 (6 0 mg/ kg)、非选择性 NOSI L - NAME10 0 mg/ kg组、非选择性 NOSI L - NAME10 mg/ kg组。其中 AG组、L- NAME组分别于伤后即刻、2 4、4 8、72 h经腹腔注射 L- NAME或 AG。进行平衡实验、避暗回避试验以评价伤后各组大鼠的学习神经功能恢复情况。伤后第 7天采用 Nissl染色及神经元抗核抗体 (Neu N)免疫组化染色观察测量伤侧海马 CA2、CA3区锥体细胞层面积及皮层坏死区面积。结果 :(1) AG组平衡实验、避暗回避试验结果显著好于创伤性脑损伤组 (P<0 .0 5 )。 (2 ) AG组海马 CA2、 CA3区锥体细胞层面积与创伤性脑损伤组比较显著增加 (P<0 .0 1) ,坏死区面积显著减小 (P<0 .0 5 )。(3) AG组神经功能恢复优于 L- NAME组。结论 :适当地应用选择性i NOS抑制剂 AG可促进大鼠脑损伤后神经功能的恢复 ,保护海马神经元 ,其效果优于非选择性 NOS抑制剂。

采用选择性催化还原减氮法机外控制船用柴油机的NO_x排放

选择性催化还原减氮法(SCR,Selective Catalytic Reduction)是船用柴油机NOx排放的机外控制方法之一.国外几家著名的船用柴油机制造厂商研究、开发、应用此方法已有10多年的历史.实践证明,此方法简易实用,能有效执行IMO"MARPOL 73/78公约"附则Ⅵ,能有效保护内河沿岸、港口和海洋的大气环境.

涂敷Al_2O_3的蜂窝状堇青石负载CuO催化剂上NH_3选择性催化还原NO

考察了涂敷γ Al2 O3 的蜂窝状堇青石负载的CuO催化剂的烟气脱硝行为 .实验表明 ,将少量CuO担载到涂敷Al2 O3 的堇青石载体上 ,可制得高活性的烟气脱硝催化剂 .催化剂的预硫化可抑制其上NH3 的过度氧化 ,提高NH3 选择性催化还原(SCR)NO的活性 ,使 35 0～ 4 5 0℃时烟气的脱硝率达 90 %以上 .堇青石的组成对催化剂的活性略有影响 ,碱金属含量低的堇青石适合用于制备烟气脱硝催化剂 ,高温时其上NH3 的过度氧化程度低 ,SCR活性高 .γ Al2 O3 的涂敷方法对催化剂的脱硝活性没有影响 ,涂敷 2 5 %Al2 O3 的堇青石即可做催化剂载体 .

钌催化剂存在下的氨湿法氧化反应条件与N_2选择性

在完全除去铵离子的湿法氧化反应中，一种钌催化剂能够将文献报道的反应条件从５４３Ｋ，７－０ ＭＰａ 缓和为４５３ Ｋ，３－０ ＭＰａ． 但是，在相对温和的反应条件下， Ｎ２ 选择性不够理想，并受到操作条件如ｐＨ、反应温度、空填充压力及催化剂用量等的影响． 在所试验的条件范围内， Ｎ２ 选择性在８５－６ ％ ～９８－１ ％ 间变化，而氨转化率却接近１００％ ． 对Ｎ２ 选择性和反应条件之间的关系进行了讨论，并通过正交试验找到了一个最佳反应条件，从而在温和的反应条件下， 使氨的氧化能够有效地向着生成Ｎ２ 的方向进行．

选择性iNOS抑制剂1400W对大鼠肠黏膜上皮细胞凋亡保护作用的研究

目的探讨选择性诱导型一氧化氮合酶(iNOS)抑制剂1400W对大鼠肠黏膜上皮细胞凋亡的保护作用及其作用机制。方法实验于2016年10月—2017年2月在湖北省第三人民医院药理实验所实施。选取50只SD大鼠,随机将SD大鼠均分5组:创伤模型组(T组)、低剂量组(L组)、中剂量组(M组)、高剂量组(H组)和假手术组(C组)各10只,其中T组、L组、M组和H组采用盲肠结扎穿孔(CLP)法模拟肠黏膜上皮细胞凋亡模型,C组只开腹腔不进行盲肠穿孔。术后1h,接受CLP法的L、M和H组分别给予不同剂量的iNOS抑制剂1400W(100、200、400μg/L)进行腹腔注射治疗,T组和C组予以等量生理盐水,观察免疫组化切片下肠黏膜上皮细胞凋亡情况;采用TUNEL法检测肠黏膜上皮细胞凋亡指数(AI),采用QRT-PCR检测各组肠黏膜组织凋亡相关蛋白Caspase-3 mRNA表达。结果T、L、M和H组肠黏膜上皮细胞均观察到不同程度的细胞凋亡,T组最严重,M组、H组明显减少,C组仅少量凋亡的上皮细胞集中在肠绒毛顶端及中下部等处;接受CLP的各组AI明显高于C组,T组AI明显高于L、M和H组,差异具有统计学意义(P<0.05),接受1400W治疗的L、M和H组AI依次降低,差异具有统计学意义(P<0.05)。T、L、M和H组肠黏膜Caspase-3 mRNA表达量均高于C组,其中T组最高,L、M和H组依次降低,差异具有统计学意义(P<0.05)。结论选择性iNOS抑制剂1400W可显著地抑制SD大鼠肠黏膜细胞凋亡,保护肠黏膜屏障。

铜镍合金电极电化学脱除硝酸盐氮的研究

针对高盐水中硝酸盐氮难脱除问题,用电沉积方法制备了三维铜镍合金电极,并系统考察了电化学脱除硝酸盐氮的影响因素。结果表明:铜镍合金电极具有良好的NO_(3)^(-)—N去除能力,增加阴极面积可以提升NO_(3)^(-)—N的去除效果,增加阳极面积则有利于提高气态氮选择性;当电流密度40 mA/cm^(2)、时间2 h时,NO_(3)^(-)—N可实现100%的去除;Na_(2)SO_(4)浓度对NO_(3)^(-)—N去除影响不大,而杂离子的存在会抑制NO_(3)^(-)—N的去除,且阳离子对总氮去除的抑制作用明显强于阴离子;Cl^(-)的引入增加了气态氮的选择性,且最佳投加时间为15 min。

Fe-Mn/Al_2O_3 catalysts for low temperature selective catalytic reduction of NO with NH_3

A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.

Promotional effects of Zr on K^+-poisoning resistance of CeTiO_x catalyst for selective catalytic reductionof NO_x with NH_3

CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.

High selectivity to p-chloroaniline in the hydrogenation of p-chloronitrobenzene on Ni modified carbon nitride catalyst

A nanocomposite composed of Ni modified carbon nitride was synthesized and used in the hydro- genation of p-chloronitrobenzene. H/D exchange demonstrated that the hydrogen chemisorbed on the surface of this nanocomposite catalyst had a hydrogen atom density of 0.65/nm2. It was active for hydrogenation but its activity was inferior to the hydrogen adsorbed on a Ni/Al2O3 catalyst. Catalytic tests showed that this catalyst possessed a lower activity than Ni/AhO3 but the selectivity towards p-chloroaniline was above 99.9%. Even at high conversion, the catalyst maintained high selectivity, which was attributed to the unique surface property of the catalyst and the absence of a site for the adsorption ofp-chloronitrobenzene, which prevents the C-Cl bond from breaking.

Synthesis of a chabazite-supported copper catalyst with full mesopores for selective catalytic reduction of nitrogen oxides at low temperature

A series of meso‐microporous copper‐supporting chabazite molecular sieve（CuSAPO‐34） catalysts with excellent performance in low‐temperature ammonia selective catalytic reduction（NH3‐SCR）have been synthesized via a one‐pot hydrothermal crystallization method. The physicochemical properties of the catalysts were characterized by scanning electron microscopy, transmission electron microscopy, N2 adsorption‐desorption measurements, X‐ray diffraction, 27 Al magic angle spinning nuclear magnetic resonance, diffuse reflectance ultraviolet‐visible spectroscopy, inductively coupled plasma‐atomic emission spectroscopy, X‐ray photoelectron spectroscopy, temperature‐programmed reduction measurements, and electron paramagnetic resonance analysis. The formation of micro‐mesopores in the Cu‐SAPO‐34 catalysts decreases diffusion resistance and greatly improves the accessibility of reactants to catalytic active sites. The main active sites for NH3‐SCR reaction are the isolated Cu^2＋ species displaced into the ellipsoidal cavity of the Cu‐SAPO‐34 catalysts.

Synergistic effects in N‐K_2Ti_4O_9/UiO‐66‐NH_2 composites and their photocatalysis degradation of cationic dyes

N-K2Ti4O9/UiO-66-NH2 composites synthesized by a facile solvothermal method have a core-shell structure with UiO-66-NH2 forming the shell around a N-K2Ti4O9 core.Their photocatalytic activities in the degradation of dyes under visible light irradiation were investigated.The N-K2Ti4O9/UiO-66-NH2 composites exhibited higher photocatalytic activity than the pure components.This synergistic effect was due to the high adsorption capacity of UiO-66-NH2 and that the two components together induced an enhanced separation efficiency of photogenerated electron-hole pairs.The mass ratio of N-K2Ti4O9 to ZrCl4 of 3：7 in the composite exhibited the highest photocatalytic activity.Due to the electrostatic attraction between the negatively charged backbone of UiO-66-NH2with the positively charged groups of cationic dyes,the composites were more photocatalytically active for cationic dyes than for anionic dyes.

Influence of sulfation on CeO_2-ZrO_2 catalysts for NO reduction with NH_3

CeO2‐ZrO2 (CeZr) and sulfated CeO2‐ZrO2 (S‐CeZr) catalysts were prepared for the selective catalytic reduction of NO with NH3. The CeZr catalysts exhibited higher activity at low temperatures (< 200°C) and lower activity at high temperatures (> 200 °C) than the S‐CeZr catalysts. The sulfation ofCeZr was studied in terms of surface acidity, redox properties and NO adsorption‐desorption bytemperature‐dependent experiments and in situ infrared spectroscopy. S‐CeZr displayed high concentrationsof acidic sites and increased surface acidities, but poor reducibility compared with CeZr.The high acidity of S‐CeZr was attributed to the presence of Br?nsted acid sites, arising mainly fromthe surface sulfates. Because the surface was covered with sulfate species, S‐CeZr showed lower NOadsorption and weaker oxidation ability than CeZr. The adsorption of NH3 on the Br?nsted acid sites restricted the reaction with NO at low temperatures, but the selective catalytic reduction cycle occurred easily at relatively low temperatures (150 °C), and the weakly bound nitrite was partially activated on the S‐CeZr catalyst at relatively high temperatures (300 °C). The catalytic mechanisms for the CeZr and S‐CeZr catalysts at 150 and 300 °C were also studied.

Recent advances in heterogeneous catalytic hydrogenation and dehydrogenation of N-heterocycles

The selective hydrogenation of quinolines to 1,2,3,4-tetrahydroquinolines(py-THQ) and its derivatives has attracted a considerable amount of attention as they show great versatility in many pharmaceuticals, agrochemicals, and fine chemicals. Over the past few decades, great breakthroughs have been achieved in the controlled synthesis of efficient heterogeneous catalysts used for the selective hydrogenation of functionalized quinoline compounds, which allow one to correlate the structure-property relationships. In this review, we will summarize the recent significant progress achieved in this field covering the synthetic strategies, microstructural and chemical features, catalytic performance, and internal relationships. State-of-the-art noble metal-based single(Pd, Pt, Ru, Rh, Ir and Au) and bi/multi-metallic catalysts(RuCu, AuPd, and PdNi) are first introduced, followed by a summary of earth-abundant metal-based catalysts(Co, Fe, Ni, and Cu). Finally, the dehydrogenation of N-heterocycles is introduced to form a reversible hydrogenation/dehydrogenation system for H2 storage, which can be employed in a liquid organic hydrogen system. Furthermore, the reaction mechanism and future research direction in these areas are also discussed. This review will deepen our understanding of the catalytic transformation of N-heterocycles and provide guidance for researchers on the rational design of catalysts.

Investigation of low-temperature hydrothermal stability of Cu-SAPO-34 for selective catalytic reduction of NO_x with NH_3

The low‐temperature hydrothermal stabilities of Cu‐SAPO‐34samples with various Si contents and Cu loadings were systematically investigated.The NH3oxidation activities and NH3‐selective catalytic reduction(SCR)activities(mainly the low‐temperature activities)of all the Cu‐SAPO‐34catalysts declined after low‐temperature steam treatment(LTST).These results show that the texture and acid density of Cu‐SAPO‐34can be better preserved by increasing the Cu loading,although the hydrolysis of Si-O-Al bonds is inevitable.The stability of Cu ions and the stability of the SAPO framework were positively correlated at relatively low Cu loadings.However,a high Cu loading(e.g.,3.67wt%)resulted in a significant decrease in the number of isolated Cu ions.Aggregation of CuO particles also occurred during the LTST,which accounts for the decreasing NH3oxidation activities of the catalysts.Among the catalysts,Cu‐SAPO‐34with a high Si content and medium Cu content(1.37wt%)showed the lowest decrease in NH3‐SCR because its Cu2+content was well retained and its acid density was well preserved.

Influence of preparation methods on the physicochemical properties and catalytic performance of MnO_x-CeO_2 catalysts for NH_3-SCR at low temperature

This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.

Selective catalytic reduction of NO_x by H_2 over Pd/TiO_2 catalyst

Pd/TiO2 catalysts prepared by three different methods(impregnation,deposition-precipitation,and polyethylene glycol reduction)were investigated in the selective catalytic reduction of NOx by H2(H2-SCR).It was found that the preparation method exerted a significant effect on the activity of the Pd/TiO2 catalyst,and that the catalyst prepared by the polyethylene glycol reduction method exhibited the highest activity in the reduction of NOx.Characterization of the catalyst showed that,in the Pd/TiO2 catalyst prepared by the polyethylene glycol reduction method,the existing Pd species was Pd0,which is the desirable species for the H2-SCR of NOx.In situ DRIFTS studies demonstrated that over this catalyst,more chelating nitrite and monodentate nitrite species formed,both of which are reactive intermediates in the H2-SCR of NOx.All of these factors account for the high activity of Pd/TiO2 prepared by the polyethylene glycol reduction method.

Promotional effects of Er incorporation in CeO_2(ZrO_2)/TiO_2 for selective catalytic reduction of NO by NH_3

A series CeO2（ZrO2）/TiO2 catalysts were modified with Er using a sol-gel method.The catalytic activity of the obtained catalysts in the selective catalytic reduction（SCR） of NO with NH3 was investigated to determine the appropriate Er dosage.The catalysts were characterized using X-ray diffraction,N2 adsorption,NH3 temperature-programmed desorption,H2 temperature-programmed reduction,photoluminescence spectroscopy,electron paramagnetic resonance spectroscopy,and X-ray photoelectron spectroscopy.The results showed that the optimum Er/Ce molar ratio was 0.10;this catalyst had excellent resistance to catalyst poisoning caused by vapor and sulfur and gave more than 90% NO conversion at 220–395 ℃ and a gas hourly space velocity of 71 400 h^-1.Er incorporation increased the Ti^3＋ concentrations,oxygen storage capacities,and oxygen vacancy concentrations of the catalysts,resulting in excellent catalytic performance.Er incorporation also decreased the acid strength and inhibited growth of TiO2 and CeO2 crystal particles,which increased the catalytic activity.The results show that high oxygen vacancy concentrations and oxygen storage capacities,large amounts of Ti^3＋,and low acid strengths give excellent SCR activity.

小型CFB锅炉烟气脱硝改造两步法应用及探讨

由于循环流化床(CFB)锅炉特有的结构和燃烧方式,其氮氧化物排放低于其它炉型,有清洁炉型之称,但随着烟气污染物排放标准的进一步提高,其氮氧化物的排放已不能满足新的排放需要。选择性非催化还原法(SNCR)工艺+低氮燃烧(LNB)脱硝技术具有投资费用少、运行成本低、锅炉改造范围小等优势,而CFB锅炉具有烟气在炉内停留时间长、便于还原剂在炉内混合等特点,该脱硝改造两步法在小型循环流化床锅炉脱硝改造中被广泛应用。本文以75t/h循环流化床锅炉为模型,并采用环保性较高的尿素作为脱硝还原剂,通过低氮燃烧(LNB)+SNCR工艺两步法脱硝技术改造方式,进一步提高脱硝效率,并对锅炉进行针对性的改进以提高其出力,最终使烟气中NO_x排放达到新的国家标准要求。主要从实施背景、技术路线、疑难问题解决及改造后的效果分析、存在问题等进行分析探讨。