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.

In situ catalytic upgrading of heavy crude oil through low-temperature oxidation

The low-temperature catalytic oxidation of heavy crude oil（Xinjiang Oilfield,China） was studied using three types of catalysts including oil-soluble,watersoluble,and dispersed catalysts.According to primary screening,oil-soluble catalysts,copper naphthenate and manganese naphthenate,are more attractive,and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil.The heavy oil compositions and molecular structures were characterized by column chromatography,elemental analysis,and Fourier transform infrared spectrometry before and after reaction.An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity-temperature characteristics.Results show that the two oil-soluble catalysts can crack part of heavy components into light components,decrease the heteroatom content,and achieve the transition of reaction mode from oxygen addition to bond scission.The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil（oil viscosity and contents of heavy fractions）.It is found that the temperature,oil composition,and internal molecular structures are the main factors affecting its flow ability.Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.

Low Temperature Preparation and Characterization for PbTiO_3 Ceramics by Sol-Gel Technique

This Paper reports a new system for preparation of lead titanate powders by the Sol Gel method. In this system, basic lead lactate, (CH 3CHOHCOO) 2Pb, is used as the lead precursor instead of the widely used Pb(OOCCH 3) 2·3H 2O and titanium tetrabutoxide monomer. This new system simplifies the chemical processing of precursor solutions of lead titanate, increases their stability in air, and offers good control Pb(Ti stoichiometry. The xerogel, obtained from the precursor solution by aging at low temperature, is found to have a higer inorganic content. Gel to ceramic conversion is achieved by calcining the xerogel from 400℃ to 800℃. The phase purity, particle size, morphology, compositional homogeneity of the gel derived powders are examined by XRD. TEM.IR and the slow reflection spectrum of partides are measured.

Preparation of LaMnO_3 for catalytic combustion of vinyl chloride

LaMnO3was prepared by citrate sol‐gel,coprecipitation,hard template,and hydrothermal methods,respectively,and its catalytic performance for the combustion of vinyl chloride was investigated.N2adsorption‐desorption,X‐ray diffraction(XRD),Raman spectroscopy(Raman),O2temperature programmed desorption(O2‐TPD),H2temperature programmed surface reaction(H2‐TPR)and X‐ray photoelectron spectroscopy(XPS)were used to characterize the physicochemical properties of the LaMnO3samples.The preparation methods had obvious effects on the distribution of oxygen and manganese species on the catalyst surface.The reaction followed the suprafacial mechanism;the activity corresponded with the high amount of Mn4+and adsorbed oxygen species.LaMnO3prepared by the citrate sol‐gel method had the best performance for vinyl chloride combustion with T90of182°C.The optimal activity was attributed to the improved redox capability of Mn4+/Mn3+.More available adsorbed oxygen and Mn4+species on the surface were mainly responsible for the remarkable enhancement of the catalytic activity.

Low-Cost Preparation of Boron Nitride Ceramic Powders

The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the low-cost urea route, and the effects of preparation temperatures, molar ratios of the raw materials and oxidation treatment on the composition, structure and surface morphology of the products were investigated through FT-IR, XRD and SEM. The results show that the products ceramize and crystallize gradually with the increase of the temperature. When the molar ratio and reaction temperature are 3：2 and 850 ℃, respectively, the products have high purity, compact structure and nice shape. The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitride but effectively remove the impurities.

Tin oxide(SnO_2) as effective electron selective layer material in hybrid organic–inorganic metal halide perovskite solar cells

The emergence of hybrid organic-inorganic metal halide perovskite solar cells （PSCs） causes a break through in the solar technology recently due to its fabrication processes. The dramatic enhancenlent in in 2009 to the recent certified record PCE of 22.7% superior optoelectronic properties and the low-cost power conversion efficiency （PCE） of PSCs flom 3.8% ndicates huge potential of PSCs for future high efficiency and large scale photovoltaic manufacturing. The electron selective layer （ESL） plays an important role in electron extraction and hole blocking function in PSCs, and there have been great interest in developing efficient ESL materials. Recently, tin oxide （SnO2） as an ESL has attracted significant research attentions owing to its low temperature preparation processes as well as yielding high PCE and good stability of PSCs. In this perspective article, we focus on the development progress of SnO2 as an ESL m PSCs, and discuss the strategies for preparing SnO2 to achieve PSCs with high efficiency, less hysteresis and good device stability.

Preparation and Characterization of PANI/PET Composite Conductive Fabric

Polyaniline /Polyester( PANI /PET) composite conductive fabric is prepared through in-situ polymerization process using aniline as monomer and PET fabric as matrix,which is treated with alkali deweighting and low temperature plasma. The property of PANI /PET composite conductive fabric is studied and characterized,including scanning electron microscope( SEM), infrared spectroscopy, conductivity, wash fastness and mechanical properties. The results show that the optimal polymerization conditions: the molar ratio of ammonium persulfate and aniline is1∶ 1,the concentration of sulfuric acid is 1 mol /L and reaction time is 90 min. Under optimum conditions,the surface resistivity of PANI /PET composite conductive fabric is about 170 Ω. After washed 5 times, the surface resistivity of PANI /PET composite conductive fabric is stable at 1 450 Ω. The breaking strength and breaking elongation of PANI /PET composite conductive fabric decrease compared with PET fabric.

碳纳米管增强TiNi复合钎料的制备与表征

针对CNTs增强TiNi复合钎料制备中存在CNTs的均匀分散性差、结构完整性差、碳基团与基体易反应而导致基体材料污染等问题,采用PECVD方法低温原位在Ni-TiH2基体上制备CNTs/TiNi复合钎料,采用XRD,SEM,Raman,TEM等对制备的复合钎料进行表征与分析.结果表明,该方法不仅保证了复合钎料中CNTs的结构完美和均匀分散性,而且保证了TiH2不会因温度过高分解,避免了复合钎料体系中钛与碳之间反应,真正意义上实现了CNTs对TiNi复合钎料的强化.通过复合钎料中CNTs的增强效果,缓解钎焊接头的残余应力,提高钎焊接头的力学、热学及高温性能,可实现陶瓷、复合材料与金属复合构件的可靠连接及高温使用.

BaTiO_(3)陶瓷的低温冷烧结制备及性能研究

近年来,冷烧结低温制备陶瓷引起了很大关注,并在BaTiO_(3)陶瓷的制备上取得了一定进展。为了提高冷烧结BaTiO_(3)陶瓷性能,本研究采用水热法制备了分散性好、粒径为100 nm的四方相(晶格参数c/a为1.0085)BaTiO_(3)粉末。采用0.1 mol/L的乙酸在100℃/1 h的条件下对粉末进行水热活化处理。以质量分数10%Ba(OH)_(2)·8H_(2)O为熔剂,在350 MPa、400℃/1 h的条件下对粉体进行冷烧结,最后经600℃/0.5 h退火获得了相对密度为96.62%、晶粒尺寸为180 nm,常温介电(ε_(r))为2836,介电损耗(tanδ)低至0.03的BaTiO_(3)陶瓷。乙酸处理后高活性粉末表面形成的非晶钛层有效促进了陶瓷的致密化,抑制了杂相的生成和晶粒长大,提高了介电性能,大幅改善了冷烧结BaTiO_(3)陶瓷出现的介电弥散现象,从而实现了BaTiO_(3)陶瓷的低温冷烧结制备。

Analytical Investigation of Prior Austenite Grain Size Dependence of Low Temperature Toughness in Steel Weld Metal

Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased.However,low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study.By direct tracking of the morphological evolution during phase transformation,it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite,whereas small austenite grain size leads to grain boundary nucleation of bainite.This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.

Performance and mechanism study for low-temperature SCR of NO with propylene in excess oxygen over Pt/TiO_2 catalyst

A 0.5 wt.% Pt/TiO2 catalyst was prepared and used for the low-temperature selective catalytic reduction （SCR） of NO with C3H6 in the presence of excess oxygen. The effects of Pt loading and 02 concentration on Pt/TiO2 catalytic performance for low-temperature SCR were investigated. It was found that optimal Pt loading was 0.5 wt.% and excess 02 favored low-temperature SCR of NOx. The mechanism of low-temperature SCR of NO with C3H6 was investigated with respect to the behavior of adsorbed species over Pt/TiO2 at 150~C using in situ DRIFTS. The results indicated that surface nitrosyl species （Pt~＋-NO and Ti3＋-NO） and pt2＋-CO are main reaction intermediates during the interactions of NO, C3H6 and 02. A simplified NO decomposition mechanism for the low-temperature SCR of NO with C3H6 was proposed.

Nanocrystalline TiO_(2) thin film electrodes prepared by common pressure hydrothermal method at low temperature

Nanocrystalline TiO2 thin film electrodes have been prepared from mixed pastes of tetrabutyl titanate and nanocrystalline TiO2 particles by common pressure hydro- thermal method at low temperature. The tetrabutyl titanate was hydrolyzed and crystallized into anatase TiO2 to inter- connect nanocrystalline TiO2 particles and adhere them to conductive substrates, obtaining highly porous and me- chanically stable TiO2 nanocrystalline film. The conversion efficiencies of the dye-sensitized solar cells based on prepared electrodes on conductive glass substrates and flexible sub- strates were 4.8% and 1.9% under illumination of 100 mW/cm2, respectively.

压力对稠油拟组分氧化的影响

为进一步明确稠油火驱过程中的反应动力学行为和产出原油组分变化规律,通过实沸点蒸馏法将新疆红浅1井区稠油划分为不同沸程的拟组分,研究了体系压力对沸程高于350℃的稠油拟组分氧化行为的影响,并在线性升温条件下进行燃烧池实验,研究体系压力对稠油各拟组分与空气反应时的产气体积分数、温度和放热量的变化规律。结果表明:体系压力对低温氧化阶段的加氧反应和脱羧反应有显著影响,且对低沸程拟组分的影响更加明显;沸程为350~420℃的拟组分在体系压力为3.0 MPa时的CO+CO_(2)生成量是其在1.0 MPa时的10倍;高沸程拟组分虽然受体系压力影响较小,但沸程大于500℃的拟组分的放热量可高达12.26 kJ/g;稠油火驱的改质效果取决于重质组分的消耗量和裂解反应。研究结果为火驱过程中稠油组分的缺失情况和油藏温度的合理分析及预测提供了借鉴。

高反射率釉膜及耐环境性能的研究

高反射率釉膜作为背板光伏玻璃上的无机烧结材料,低温制备和高反射率是其关键指标。介绍了经济实用的钠钙硅酸盐熔块(a),部分磷替代硅的磷硅酸盐熔块(b),以及用硼全部替代磷的硼硅酸盐熔块(c),考察了熔块组成与熔融温度和附着力之间的关系。然后将各种熔块和氧化钛分别按1∶1在720℃下保持95 s烧成不同系列的反射釉膜,并测定了其反射率和表面粗糙度。结果表明,获得的(c)熔块的反射釉膜,其反射率为73.95%,进一步对(c)熔块的反射釉膜进行退火和冷冻处理以研究其耐环境性能,其反射率几乎未发生变化。

低温流通肉类预制菜的品质影响因素与控制技术研究进展

随着生活节奏加快和消费习惯的变化,人们对餐饮的需求也发生了转变,快捷、方便的餐饮品类越来越受消费者的青睐,预制菜市场也日渐火热。低温流通的肉类预制菜是预制菜中的重要品类之一,由于品类丰富、食材新鲜、操作便捷,成为人们预制菜消费的新选择。但预制菜目前仍存在加工技术不成熟、冷链物流体系不完善、产品生产标准及操作规范流程不统一等问题,从而导致预制菜感官品质不稳定、安全性不足,降低人们的消费信心。因此需要对低温肉类预制菜的工艺流程和相应的加工技术进行升级转换,为低温肉类预制菜行业的高质量发展提供技术支持。本文主要综述了低温肉类预制菜的研究现状,加工过程对预制菜品质和安全性的影响,以及可应用于低温肉类预制菜的快速冷却与冷冻、冷链物流、杀菌、智能与活性包装等新型食品加工技术,以期为预制菜的创新与可持续发展提供参考。

不同杀菌方式对白切香猪肉品质和挥发性成分的影响

为了研究低温调理白切香猪肉在不同杀菌过程中品质和挥发性成分的变化,该文采用气相色谱-离子迁移谱技术对未杀菌、水浴巴氏杀菌、高静水压杀菌、辐照杀菌和高温高压处理香猪肉的挥发性组分进行定性分析,共鉴定出63种挥发性风味化合物,包括醛类5种、酮类10种、醇类11种、酯类13种、醚类6种、呋喃类4种、吡嗪类4种、噻唑类2种,其他类8种。根据各组挥发性化合物的相对含量,高静水压组的香猪肉比水浴巴氏杀菌组更接近于对照组。利用扫描电镜比较了香猪肉在4种杀菌方式下的微观结构,辐照杀菌和高静水压杀菌能较好保留原样品的肌纤维结构。综合分析,高静水压杀菌较好地保持了产品原有的品质和风味,在低温调理类肉制品以及预制菜肴的杀菌领域具有较好的应用前景。

环烷基稠油火驱开发中焦炭生成规律及物理化学特征

为明确环烷基稠油在火驱过程中生成焦炭的规律和石油焦炭基本性质,应用动态气流氧化原油装置,开展了环烷基稠油注空气燃烧生成焦炭过程的研究,并对生成的石油焦炭进行了组成和结构表征。研究表明:环烷基稠油在250~300℃开始生成焦炭,随着反应温度升高,焦炭产率逐渐增加,温度达到450℃时,焦炭产率最高,为10.8%;温度为500~600℃时,焦炭的燃烧反应加剧,焦炭收率降至4.6%。电镜观察焦炭为0.05~1.00μm碳层叠加的致密片层结构,以400℃为分界点可以将焦炭分为2类。300~350℃生成焦炭的H/C为0.78~0.82,为含有大量烷基链的氧化焦炭;400℃时裂解反应加剧,稠油成焦过程由加氧反应为主转变为裂解反应为主;400~600℃生成焦炭的H/C为0.33~0.47,为芳香度和石墨化程度更高的裂解焦炭。该研究对环烷基稠油火驱开发点火及火线控制具有一定指导意义。

聚乙烯醇缩丁醛的制备及应用技术进展

聚乙烯醇缩丁醛(PVB)是重要的高分子材料,由聚醋酸乙烯酯或者聚乙烯醇与正丁醛缩合反应而成。PVB具有很好的透明度、黏合力、成膜相容性,适用于耐光、耐热、耐寒、耐水、耐冲击等环境,主要应用于安全玻璃、光伏领域。PVB的制备工艺复杂,一般方法难以获得高纯产品,核心技术为国外所垄断。低温下,PVB的物理性能较差,常采用优势互补法,对其进行接枝改性、复合和共混,来提高材料的综合性能。近些年来,有关PVB的应用研发已成热点。简介了近年来聚乙烯醇缩丁醛的制备工艺,重点阐述了研发与应用PVB对其他功能材料进行改性、复合及共混的技术进展。

碳纳米管-聚苯胺/聚乙烯醇复合气凝胶的制备及其吸波性能

为了获得高性能复合气凝胶吸波材料,以螺旋碳纳米管(Helical carbon nanotubes,HCNTs)和聚苯胺(Polyaniline,PANI)为吸波剂,聚乙烯醇(Polyvinyl alcohol,PVA)为基体,采用定向冷冻法和低温原位聚合法制备了高性能螺旋碳纳米管-聚苯胺/聚乙烯醇复合气凝胶(HCNTs-PANI/PVA composite aerogels,HPPA)。采用扫描电子显微镜、红外光谱仪、拉曼光谱仪和X射线衍射仪对HPPA复合气凝胶的形貌与结构进行表征,并使用矢量网络分析仪测定HPPA复合气凝胶的电磁参数和吸波特性。结果表明:所制备的HPPA复合气凝胶具有优异的吸波性能,最小的反射损耗为-69.08 dB,有效吸收带宽为4.20 GHz;HPPA复合气凝胶优异的吸波性能主要归因于其定向的多孔结构和非均匀介质界面形成的良好阻抗匹配特性和多重极化协同效应。该文为构建高性能复合气凝胶吸波体系提供了新思路。

SIAPES的合成及低温油藏原位乳化驱油体系构建与性能

W/O型乳液驱油是一项有效提高老油田采收率技术。但低温条件下常用的乳化体系不能同时满足形成W/O型乳液和降低界面张力。本文合成并表征了异构十三醇聚氧乙烯醚磺酸钠(SIAPES),并与椰子油烷基二乙醇酰胺(CEDA)复配构建了低温油藏原位乳化驱油体系,评价了体系的乳化性能、降低了油水界面张力并改善了岩石润湿性能力。同时利用在线NMR驱替系统揭示了原位乳化驱油体系在低温油藏条件下提高采收率的潜力。结果表明:原油-地层水自乳化相变点为60%,利用原位乳化驱油体系对油水自乳化进行干预后,乳液相变点提高到65%,且发生相变后乳液黏度明显高于自乳化乳液的黏度,流度控制能力增强;原位乳化驱油体系能将油水界面张力由12.00 mN/m降低至0.12 mN/m,改善亲油岩心润湿性至亲水;在渗透率级差为12,水驱至经济极限的条件下,0.6 PV的原位乳化驱油剂驱和后续水驱使采收率提高了26.8%。