Effect of BaO on mineral structure and hydration behavior of phosphoaluminate cement

Journal of Thermal Analysis and Calorimetry - Phosphoaluminate cement (PAC) clinker was one new type of special cement, which exhibits good mechanical properties and durability. In this paper, the...     

铁改性水滑石基Pt/BaO/MgFeO催化剂焙烧温度对催化剂结构及NO_x吸附-还原性能的影响

采用共沉淀法和浸渍法制备了贵金属负载均匀的镁铁水滑石基稀燃氮氧化物捕集(LNT)催化剂,并采用多种表征手段研究了焙烧温度对催化剂结构及NO_x吸附-还原反应的影响。结果表明,500-700℃焙烧后催化剂晶相结构稳定,800℃焙烧后催化剂表面出现烧结,Pt颗粒发生团聚;随焙烧温度升高,催化剂的NO_x脱附峰面积先减小后增大,但峰值温度变化不大;与500℃焙烧催化剂相比,800℃焙烧后催化剂表面NO_x吸附物种及吸附路径发生改变,而还原反应产物中氨气/氮气体积比下降,NO_x转化效率由91.7%降为85.2%。     

富钙生物油煅烧过程中孔结构变化特性的研究

在热重分析仪上进行富钙生物油煅烧实验。结果表明,富钙生物油的煅烧过程分为三个阶段,分别是生物油部分组分的脱CO₂和H₂O阶段、有机酸钙盐分解阶段、碳酸钙分解阶段。其中,有机酸钙盐分解对煅烧产物的孔结构有重要影响。在450℃~600℃,气体析出的气蚀作用与生物油中高分子化合物的碳化沉积现象同时存在,两者共同作用,但后者占主导,高分子化合物的碳化沉积主要发生在500℃~600℃。600℃以后,碳酸钙开始分解,释放出CO₂,气蚀作用使煅烧产物内部形成新的微孔,产物具有发达的孔结构。相同煅烧温度下,富钙生物油煅烧产物的孔隙特性明显优于CaCO₃。     

Pt-Rh型三效催化剂中BaO的作用

研究了以浸溃法制备的以BaO为助剂的Pt-Rh型三效催化剂对C3H8，CO，NOx的三效催化活性。主要考察了BaO不同的添加方式对催化剂三效转化活性的影响，并对催化剂样品进行了XRD，H2-TPR和O2-TPD表征。结果表明：BaO的添加方式的不同，直接影响催化剂的活性。特别是Ba与Ce，Zr以共沉淀的方式形成CeO2-ZrO2-BaO固溶体，可促进催化剂在低温时的水汽转换反应，显著降低了催化剂的起燃温度。     

焙烧温度对Fe-Mn催化剂结构和F-T合成性能影响

研究了焙烧温度对Fischer-Tropsch(F-T)合成Fe-Mn催化剂的织构性质、还原行为以及在还原和反应过程中结构变化的影响；在H2/CO=2.0、260 ℃、2.5 MPa和1 000 h－1条件下在固定床反应器上考察了焙烧温度对Fe-Mn催化剂F-T合成反应活性、烃产物选择性和运行稳定性的影响。XRD和TPR结果表明，随着焙烧温度的升高，催化剂中α-Fe2O3晶粒增大，催化剂比表面积降低，促进Mn3+渗入α-Fe2O3晶格中，形成了铁锰固溶体物相，使得催化剂难于还原，当焙烧温度升高到700 ℃时，催化剂中的α-Mn2O3相完全消失。催化剂F-T合成反应评价表明，在不降低催化剂活性的同时，焙烧温度的升高可显著地提高催化剂的反应运行稳定性，并促使烃产物分布向高碳数方向偏移；600 ℃焙烧的Fe-Mn催化剂运行200 h，总体活性高，失活速率较低，对低碳烯烃和中间馏分油段产物选择性好。     

Effect of ZnO on the hydration of Portland cement

ZnO added to the system Portland cement — water changes the kinetics of the hydration process substantially. Amorphous zinc hydroxide is formed and inhibits the reaction of tricalcium silicate with water, resulting in an induction period prolongation. This effect depends on the amount of ZnO added to the hydrated paste. The transformation of zinc hydroxide into calcium hydrozincate provokes the further hydration.

---

Zusammenfassung Durch den Zusatz von ZnO zum System Portlandzement-Wasser wird die Kinetik des Hydratationsprozesses grundlegend verändert. Amorphes Zinkhydroxid wird gebildet, was einen Inhibitor für die Tricalciumsilikatreaktion mit Wasser darstellt, wodurch die Induktionsperiode verlängert wird. Dieser Effekt hängt von der Menge ZnO ab, die dem Zementbrei zugesetzt wurde. Die Umwandlung von Zinkhydroxid zu Calciumhydrozinkat führt eine weitere Hydratation herbei.

     

Effect of reaction conditions on the hydration of isoprene

Effect of conditions (partial pressure of isoprene, temperature, catalyst concentration, medium) on the rate and selectivity of reactions occurring in interaction of isoprene with water in the presence of orthophosphoric acid as a catalyst was studied at elevated temperatures and pressures in the liquid phase. The reaction orders with respect to isoprene were determined for reactions in which 3-methylbutanone-2,2-methylbutanal, and 2,2-dimethylpropanal are formed. The applicability of various acidity characteristics for describing the rates of the reactions under study are considered.     

Effect of calcination atmosphere on the structure and photocatalytic properties of titania mesoporous powder

In the work presented here, mesoporous titania (MTO) powders are synthesised by the sol?Cgel method using amphiphilic triblock copolymer as a template in two different calcination atmospheres, N₂ and air. Various techniques such as sequential thermal analysis (STA), small-angle X-ray diffraction (SAXRD), wide-angle X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)?Cvisible spectroscopy, high-resolution transmission electron microscopy (HRTEM) and N₂-adsorption/desorption analysis were utilised to study the prepared samples. Furthermore, the photocatalytic activities of the prepared samples were evaluated from the photo-degradation analysis of methylene blue (MB). For the sample calcined at N₂, the formation of an ordered mesostructure with a high specific surface area (172?m²?g^?1), mesoporosity (48%) and enhanced photocatalytic activity were obtained compared to that of the sample calcined in air. The observed increased MB degradation for the latter is mainly attributed to the formation of higher specific surface area and mesoporosity. The availability of highly ordered open-pore channels could provide increased contacts between reactants in the solution and the active sites on the surface of titania mesoporous particles. Considering the photoactivities of the samples, it is revealed that the photocatalytic activity is enhanced, together with an increase in the surface defects in N₂ atmosphere.     

BaO对Pd/Al2O3催化性能的影响

以 Pd(C2 H3O2 ) 2 为前身 ,制备了系列 Ba O- Al2 O3复合氧化物负载钯的催化剂 .用质量滴定法 ,测定了复合载体的零电荷点 (pzc) .结果表明 ,体系的 pzc随 Ba O含量的增加而增大 ,在 5 %～ 10 %之间存在一拐点 ,并与XRD所测 Ba O在 Al2 O3上的单层分散阈值相对应 .复合载体在制备中发生固相反应 ,所生成的 Ba Al2 O4可以阻止 Al2 O3的相变 ,并极大地提高载体的热稳定性 ,其中 5 % Ba O的作用最为明显 .Ba O的引入 ,增强了 Pd/Al2 O3对 CO的氧化能力 ,同时 ,提高了其热稳定性     

Effect of hydration on the stability of fullerene-like silica molecules

The hydration of fullerene-like silica molecules was studied by the density functional method (exchange-correlation functional B3LYP, basis set 6-31G**). It was demonstrated that completely coordinated structures transform to more stable hydroxylated ones during hydrolysis. These in turn react with H₂O molecules with the formation of hydrogen bonds.     

Effect of hydration on the dielectric properties of C-S-H gel

The behavior of water dynamics confined in hydrated calcium silicate hydrate (C-S-H) gel has been investigated using broadband dielectric spectroscopy (BDS; 10(-2)-10(6) Hz) in the low-temperature range (110-250 K). Different water contents in C-S-H gel were explored (from 6 to 15 wt%) where water remains amorphous for all the studied temperatures. Three relaxation processes were found by BDS (labeled 1 to 3 from the fastest to the slowest), two of them reported here for the first time. We show that a strong change in the dielectric relaxation of C-S-H gel occurs with increasing hydration, especially at a hydration level in which a monolayer of water around the basic units of cement materials is predicted by different structural models. Below this hydration level both processes 2 and 3 have an Arrhenius temperature dependence. However, at higher hydration level, a non-Arrhenius behavior temperature dependence for process 3 over the whole accessible temperature range and, a crossover from low-temperature Arrhenius to high-temperature non-Arrhenius behavior for process 2 are observed. Characteristics of these processes will be discussed in this work.     

Effect of ternesite on the hydration and properties of calcium sulfoaluminate cement

Journal of Thermal Analysis and Calorimetry - Ternesite is an intermediate phase formed during clinkering of calcium sulfoaluminate (CSA) cement. This paper presents an experimental study on the...     

Effect of calcination conditions on the properties of a catalyst for ethylbenzene dehydrogenation

Summary The effects of calcination conditions on the properties of the catalyst for dehydrogenation of ethylbenzene were studied by using TG, DTA, and XRD. The formation temperature of polyferrite was higher than 600°C. The strength of the catalyst changed during calcination. Higher temperature enhanced the strength and improved the activity of catalyst. The calcination model has great influences on the catalyst performance. Multi-stage calcination improved the catalyst activity.     

焙烧温度对钼锡催化剂结构和二甲醚氧化性能的影响

采用水热法制备了Mo/Sn物质的量比为1:2的Mo1Sn2催化剂,通过改变焙烧温度(400?700℃),调控了钼锡催化剂的结构,并研究了催化剂结构变化对二甲醚(DME)选择氧化制甲酸甲酯(MF)性能的影响.发现400℃焙烧的Mo1Sn2催化剂具有良好的催化氧化二甲醚生成甲酸甲酯的性能,在110℃、常压条件下,DME转化...     

BaO对Pd/Al2O3上CH4催化燃烧性能的影响

以醋酸钯为前身盐, BaO-Al2O3复合氧化物为载体制备了系列负载型钯催化剂. BET和XRD表征结果表明,复合氧化物在制备过程中发生固相反应所生成的BaAl2O4 可以阻止γ-Al2O3向α相的转变,显著增强Al2O3的热稳定性.以甲烷燃烧为模型反应的评价结果表明, BaO的引入提高了催化剂上甲烷燃烧反应的活性和稳定性.     

Effect of hydration andpH on the thermal stability of proteinase K

The effect of hydration andpH on the thermal stability of proteinase K was studied in the temperature range 310–450 K by differential scanning calorimetry. The dependences of the denaturation temperatureT _d, the specific enthalpy of denaturation H _d and the maximum of excess apparent specific heat capacityC _ex ^max upon the degree of hydrationh and thepH of the buffers used are presented. The relation betweenT _d andh is of the Flory-Garrett's type. By means of Ooi's model, the two components of the denaturation enthalpy arising from hydration and conformational change, respectively, were estimated. The fact that the specific denaturation enthalpy of proteinase K is very low may be attributed to its very low enthalpy of conformational change per heavy atom.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthdayThis major project was supported by the National Natural Science Foundation of China.     

ZnCr基催化剂煅烧温度对异丁醇合成性能的影响

研究了煅烧温度对ZnCr基催化剂合成异丁醇性能的影响。结果表明,随着煅烧温度的升高,催化剂的活性和产物分布都发生了较大的变化。催化剂在较低的温度下煅烧,液相产物中醇主要是甲醇和异丁醇;在较高的温度下煅烧,液相产物醇的分布符合A-S-F方程。用BET、XRD、H₂-TPR、XPS等技术手段对催化剂织构参数、体相结构、还原性能、表面组成进行表征。结果表明,在300℃煅烧时,催化剂中的ZnO和Cr₂O₃未完全形成非计量尖晶石Zn_xCr_2/3(1-x)O;400℃煅烧时,催化剂中形成了最多量非计量尖晶石Zn_xCr_2/3(1-x)O;当煅烧温度高于400℃时,随着煅烧温度进一步升高,非计量尖晶石Zn_xCr_2/3(1-x)O逐步发生了分解,生成了更多量的ZnO和Cr₂O₃,导致催化剂的活性随之下降。进一步证明了非计量尖晶石Zn_xCr_2/3(1-x)O是该催化反应活性相。     

Effect of phase change materials on the hydration reaction and kinetic of PCM-mortars

The phase change materials are considered an attractive way to reduce energy consumption thanks to their heat storage capacity. Their incorporation in the construction materials allows the energy to be an integral part of the building structure. Even though PCMs have shown their reliability from a thermal point of view, some drawbacks linked to their use were emphasized such as the loss of the compressive strength of the PCM-material. This paper attempts to provide an explanation by the investigation of the hydration kinetic of PCM-mortars. The semi-adiabatic Langavant test was adapted to this case. The numerical diffuse element method was used for the computation of the heat flux, which is a compulsory step for the determination of the hydration degree. The results showed a lower heat released by the PCM mortars compared to a control mortar as well as a delay in the hydration progress with the addition of PCMs.