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.

Temperature-dependent Hydrothermal Synthesis of Two Distinct Three-dimensional Copper Complexes

Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.

Influences of Low-Temperature Hydrothermal Fluids on the Re-distributions and Occurrences of Associated Elements in Coal——A Case Study from the Late Permian Coals in the Zhijin Coalfield, Guizhou Province. Southern China

The occurrences of associated elements and their genetic factors in the No. 30 coal seam in the Zhijin Coalfield were studied using instrumental neutron activation analysis, inductively coupled plasma-atomic emission spectroscopy, and a scanning electron microscope equipped with an energy-dispersive X-ray analyzer. And, a microscope photometer system (Leitz MPV-Ⅲ) was used to observe the characteristics of coal petrology. According to the influence degree by the siliceous low-temperature hydrothermal fluids, the organic matter is divided into four types: A, B, C, and D of the hydrothermally-altered organic matter (HAOM). The study shows that the high content of Fe (2.31%) is not from pyrite, but mostly from the siliceous low-temperature hydrothermal fluids. The occurrences of the associated elements in the four organic matter types are different. The contents of Fe, Si, and Al are decreasing, but S and Cu are increasing in the order of the HAOM-A, HAOM-B, HAOM-C, and HAOM-D. The losing rate of sulfur in organic matter is 0.35% and the content of Fe taken from the low-temperature hydrothermal fluids into the organic matter is 0.794% during the siliceous low-temperature hydrothermal fluids invading the coal seam. The above facts indicate that the low-temperature hydrothermal fluids play a crucial role in the re-distributions and occurrences of associated elements in coal.

Characterization of Pr-CeO_2 Nano-crystallites Prepared by Low-temperature Combustion&Hydrothermal Synthesis

Pr-CeO2 Nano-crystalline red pigments were prepared by low-temperature combustion with a later hydrothermal treatment using Ce（NO3）3·6H2O and Pr6O11 as raw materials. The phase composition, coloring mechanism and morphology of pigments were analyzed by XRD, SEM, EDS and XPS. Results showed that Pr-CeO2 solid solution with a fluorite structure was obtained by the diffusion of Pr^＋3 into CeO2 crystal lattice during the synthesis process. XPS analysis indicated that Pr^＋3 substitutes Ce^＋4 in CeO2 and is compensated by oxygen vacancies. Compared with low-temperature combustion synthesis, the Pr-CeO2 pigments prepared with a subsequent hydrothermal treatment have an average grain size of about 16.70 nm, and the crystallinity and red tonality are improved.

Study on the High Precision Acoustic Measurement Techniques for Determining Temperature Field Around Seafloor Hydrothermal Vent

This paper presents the basis of acoustic method used for temperature field measurement of seafloor hydrothermal vent and two techniques of the parabolic interpolation and the bending compensation of propagation paths of acoustic signal are introduced. Experimental research is performed to exactly rebuild the temperature field around hot springs on the floor of Qiezishan Lake, Yunnan, China. The accuracy of the travel time estimation has been improved based on the aforementioned technique and method. At the same time, by comparison of the results of temperature field with different means, the max absolute error, the maximum relative error and the root mean square error are given. It shows that the technique and the method presented in the paper can be applied to the temperature field measurement detector around the seafloor hydrothermal vent. It also has a good accuracy.

Hydrothermal Synthesis and Characterization of a Novel Low Temperature Phase K_4InTi_4O_(11) (OH)·5H_2O

A novel low temperature phase K4InTi4O11 (OH)'5H2O was prepared by thehydrothermal method. The product was characterized by XRD, SEM, TG, DTA and ICP. Theresults indicated that the product crystallizes in a cubic system with a cell parameter a=0.7868 um.Moreover, it ecomposes to an amorphous phase after calcining at 340 ℃.

Low Temperature Synthesis of Nano Porous 12CaO?7Al_2O_3 Powder by Hydrothermal Method

Single-phase insulating 12CaO？7Al_2O_3（C12A7） powder was synthesized using an optimized hydrothermal method. Pure phase of C12A7 was got at a comparatively lower temperature（c.a. 300 ℃） than that has been previously reported. The crystallite size of the synthesized C12A7 powder was 7±2 nm. The surface area values calculated for all the samples at a synthesis temperature range of 250-800 ℃ for 5 h were in the range of about 19-24 m^2/g, with pore sizes of 12-20 nm. This low-temperature-based synthetic strategy along with nano porous structures and a high surface area value can facilitate catalyst application.

Numerical analysis for permafrost temperature field in the short term of permafrost subgrade filling

Purpose-It is of great significance to study the influence of subgrade filling on permafrost temperature field in permafrost area for the smooth construction and safe operation of railway.Design/methodology/approach-The paper builds up the model for the hydrothermal coupling calculation of permafrost using finite element software COMSOL to study how permafrost temperature field changes in the short term after subgrade filling,on which basis it proposes the method of calculation for the concave distortion of freezing front in the subgrade-covered area.Findings-The results show that the freezing front below the subgrade center sinks due to the thermal effect of subgrade filling,which will trigger hydrothermal erosion in case of sufficient moisture inflows,leading to the thawing settlement or the cracking of the subgrade,etc.The heat output of soil will be hindered the most in case of July filling,in which case the sinking and the distortion of the freezing front is found to be the most severe,which the recovery of the permafrost temperature field,the slowest,constituting the most unfavorable working condition.The concave distortion of the freezing front in the subgrade area increases with the increase in temperature difference between the filler and ground surface,the subgrade height,the subgrade width and the volumetric thermal capacity of filler,while decreases with the increase of the thermal conductivity of filler.Therefore,the filler chose for engineering project shall be of small volumetric thermal capacity,low initial temperature and high thermal conductivity whenever possible.Originality/value-The concave distortion of the freezing front under different working conditions at different times after filling can be calculated using the method proposed.

Effects of heat treatment conditions and Y-doping on structure and phase transition temperature of VO2 powders

The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 precursor.Increasing temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of VO2.Due to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined obviously.DSC curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.

Modeling Hydrothermal Transfer Processes in Permafrost Regions of Qinghai-Tibet Plateau in China

Hydrothermal processes are key components in permafrost dynamics; these processes are integral to global wanning. In this study the coupled heat and mass transfer model for （CoupModel） the soil-plant-atmosphere-system is applied in high-altitude permafrost regions and to model hydrothermal transfer processes in freeze-thaw cycles. Measured meteorological forcing and soil and vegetation properties are used in the CoupModel for the period from January 1, 2009 to December 31, 2012 at the Tanggula observation site in the Qinghai-Tibet Plateau. A 24-h time step is used in the model simulation. The results show that the simulated soil temperature and water content, as well as the frozen depth compare well with the measured data. The coefficient of determination （R2） is 0.97 for the mean soil temperature and 0.73 for the mean soil water content, respectively. The simulated soil heat flux at a depth of 0-20 cm is also consistent with the monitored data. An analysis is performed on the simulated hydrothermal transfer processes from the deep soil layer to the upper one during the freezing and thawing period. At the beginning of the freezing period, the water in the deep soil layer moves upward to the freezing front and releases heat during the freezing process. When the soil layer is completely frozen, there are no vertical water ex- changes between the soil layers, and the heat exchange process is controlled by the vertical soil temperature gradient. During the thaw- ing period, the downward heat process becomes more active due to increased incoming shortwave radiation at the ground surface. The melt water is quickly dissolved in the soil, and the soil water movement only changes in the shallow soil layer. Subsequently, the model was used to provide an evaluation of the potential response of the active layer to different scenarios of initial water content and climate warming at the Tanggula site. The results reveal that the soil water content and the organic layer provide protection against active layer deepening in summer, so climate warming will cause the permafrost active layer to become deeoer and permafrost degradation.

Structural Changes of Y Zeolites with Different Initial SiO_2/Al_2O_3 Ratios during Hydrothermal Treatment

The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.

GROUND TEMPERATURE AND ROCK THERMOPHYSICAL PROPERTIES IN FILDES PENINSULA

During 1985-1986, 1986-1987, and 1988-1989 expeditions on Fildes Peninsula the ground temperature was measured. A total number of 218 ground temperature data were obtained. The thermal conductivity measurements were made on 121 rock samples collected during expedition. This article gives a brief analysis and summarization of these data.

Effects of temperature and water limitation on the germination of Stipagrostis ciliata seeds collected from Sidi Bouzid Governorate in Central Tunisia

Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indeed, the majority of steppe ecosystems are characterized by a low density of perennial grass species at present. This study evaluated the effects of temperature and water limitation on the seed germination of Stipagrostis ciliata（Desf.） de Winter, a perennial grass species. The seeds were collected from the Bou Hedma Park, Sidi Bouzid Governorate, Central Tunisia. The thermal time and hydrothermal time models were used to describe the seed germination of S. ciliata under different water potentials and temperatures. The germination response of S. ciliata seeds in darkness was evaluated over a range of temperatures（15°C, 20°C, 25°C, 30°C and 35°C） and across a wide range of osmotic potentials（0.0, –0.2, –0.6, –1.2, –1.6 and –2.0 MPa） of the polyethylene glycol（PEG6000） solutions at each temperature level. Among the tested temperatures, 25°C was found to be the optimal temperature to the germination of S. ciliata seeds. The final germination percentage（75.2%） was obtained with distilled water. The progressive decrease of osmotic potential of the PEG6000 solutions inhibited the seed germination. However, the number of days to first germination was increased with a reduction of osmotic potential. A significant positive relationship was identified between final germination percentage of S. ciliata seeds and osmotic potential of the PEG6000 solutions, with R^2 ranging from 0.5678 to 0.8761. Furthermore, a high degree of congruency between predicted and observed germination time course curves was observed. In general, S. ciliata exhibits a significant adaptation capacity for water limitation and high temperature in arid ecosystems.

Synthesis of SAPO-34/graphite composites for low temperature heat adsorption pumps

Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive grapbitic supports, aiming at the development of highly pertbrming adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.

Effect of operating temperature on aged single lap bonded joints

In recent decades,designers have increasingly focused on the stability of assemblies in composite materials over time,particularly when used in structural applications.The use of structural adhesives allows for realising assemblies without mechanical fasteners.In fact,bonding is an assembly technique that prevent corrosion,ensures uniform stresses in the joint,and grows the specific resistance of the assembly.The knowledge of the behaviour of bonded joint is necessary to ensure the reliability of this technique over time,especially in aggressive environments.The aim of this wo rk consists in investigating the combined effect of hydrothermal ageing and temperature test on the lap shear strength of single lap joints realised in CFRP.The results showed a higher influence of the ageing on paste adhesive compared to film adhesive.However,the ageing,combined with the operating temperature,played a fundamental role on the shear strength of the bonded joints.

水热反应温度对ZnIn_(2)S_(4)/Bi_(2)WO_(6)复合催化剂的影响研究

为解决传统半导体光催化剂可见光响应能力弱、光生电子空穴复合快、能带结构导致载流子氧化还原能力弱等问题,采用水热法制备ZnIn_(2)S_(4)/Bi_(2)WO_(6)(ZlS@BW)复合催化剂并系统研究水热反应温度对其结构性能的影响。当水热温度从80℃升高到160℃,ZlS@BW复合光催化剂结晶度提高,形貌转变为致密核壳结构,比表面积和光电性能先降低再升高,氟伐他汀去除率逐步上升。而当温度升高到200℃时,核壳结构遭到了破坏,比表面积和光电性能变差,氟伐他汀的降解效果降低,光催化性能下降。结果表明,水热温度为160℃时,制备的ZlS@BW复合光催化剂晶型结晶程度较高,且形貌致密,比表面积最大,产生的瞬态光电流最大,阻抗半径最小,具有最优光催化性能。对污染物氟伐他汀降的降解效率最高,可达到75.47%。

渗流作用下粗粒土冻结壁交圈规律及预测模型探索

由于渗流作用下的冻结壁发育规律不明等原因,部分冻结法施工工程依靠人工经验,缺乏科学的预测模型,与精准化设计和控制还有很长的距离。为探索渗流作用下冻结法施工中粗粒土层冻结壁的演化规律,本文首先建立冻结法施工数值模型,并通过室内模型试验反演验证所建立模型的有效性和适用性。之后,考虑渗流速度、冻结管间距、环境温度、含水率和导热系数等五个因素,开展冻结壁形成正交数值试验,确定冻结壁交圈时间和厚度的主控因素。最后,通过数值模拟研究主控因素作用下冻结壁的发育和演化规律。基于结果建立临界流速、冻结壁厚度、冻结壁交圈时间的预测模型,给出冻结法施工参数的选择方案。结果表明,建立的冻土水热相变耦合模型可有效模拟渗流条件下土体冻结过程,能够满足冻结壁发育过程计算分析的需要。基于正交数值试验结果发现,渗流速度对冻结壁厚度和交圈时间的贡献百分比分别为78%和52%,是影响冻结壁能否交圈和最终厚度的主控因素。当渗流速度超过一定阈值时,冻结壁无法交圈。本文将这一阈值定义为冻结法施工中的临界流速。当冻结壁能够交圈,其最终形成的冻结壁厚度也主要由渗流速度决定,二者呈负指数函数关系。冻结管间距对冻结壁最终厚度影响不大,但是对冻结壁交圈时间影响较大,它们之间存在负指数函数关系。本文给出了0~6 m·d^(-1)条件下的临界流速、冻结壁厚度、冻结壁交圈时间计算模型,它们可为粗粒土地层的冻结法施工参数选择和施工工艺设计提供理论指导。

某锂矿低温熟化—水浸提锂和提纯高纯石英新工艺

皖南低品位热液蚀变型锂矿Li_(2)O含量0.21%,属于新类型锂矿资源,主要矿物成分有长石、石英、白云母、绿泥石,锂主要以晶格形式赋存于锂绿泥石中。新工艺采用-1 mm原矿筛分,+0.425 mm粒级进入磨矿,制备-0.425+0.074 mm合格粒级。脱泥后合格粒级产品经磁选得云母精矿,非磁性物浮选得到长石精矿和石英精矿,长石精矿和云母精矿分别进行提锂,石英精矿进行酸处理提纯得高纯石英。将原矿筛出的-0.074 mm细泥、再磨产生的-0.074 mm细泥、合格粒级搅拌擦洗产生的-0.074 mm细泥,合并为总泥进行后续提锂。试验结果表明:总泥、云母、长石分别采用低温熟化—水浸工艺提锂,累计得Li_(2)O浸出率88.78%,酸浸后石英精矿含SiO_(2)99.942%,Fe 4.38 mg/kg,达到高纯石英低端产品要求,提锂后的长石和云母浸渣产率54.48%,可用于建筑材料。浸出前后样品的XRD和SEM分析表明,硫酸低温熟化破坏了锂绿泥石晶格结构,H+代替锂绿泥石中Li+,将锂释放出来。新工艺降低了磨矿成本,锂浸出率高,兼顾云母、石英、长石的回收,减少了尾矿排放,提高了低品位热液蚀变型锂矿的综合利用水平。

小晶粒高硅铝比NaY分子筛低温合成研究

采用自制的偏铝酸钠为合成导向剂,在低温下水热晶化合成出了小晶粒高硅铝比的NaY分子筛。考察了合成导向剂的陈化温度、陈化时间、晶化碱度、晶化温度和晶化时间对产品的影响,得到了制备NaY分子筛最佳的工艺条件,并进行了放大制备。在此条件下,NaY分子筛结晶度(峰面积)≥90%,结晶度(峰高)≥85%,硅铝比≥5.5,晶粒尺寸均在(100~200)nm,不仅优于工业标样的指标要求,且易于放大。

花岗岩类锂矿床中锂辉石和锂云母共生性的实验模拟研究

锂是一种稀有金属元素,锂辉石和锂云母是最重要的硬岩型锂矿矿石矿物,探究二者的共生性及条件,对揭示锂元素在不同锂矿石矿物中的赋存机制以及花岗岩类锂矿床的形成机制具有重要意义。本文应用热液金刚石压腔开展了锂辉石-锂云母-H_(2)O体系的原位观测结晶实验,10组实验产物均为锂辉石和白云母,锂辉石结晶集中在500~780℃、350~1300MPa的温压条件下,白云母结晶集中在440~710℃、180~1100MPa的温压条件下。结合前人实验得到的锂云母结晶条件(500~650℃、100~450MPa),以及实验产物云母的激光拉曼线扫结果,可以得到以下认识:锂辉石与白云母结晶温压条件具有较高的重叠度,与二者可在伟晶岩中广泛共生的现象一致;锂辉石和锂云母的结晶主要受到压力影响,温度和体系F含量的影响居于次要地位;透锂长石和锂云母形成于相似的温压条件,但体系F含量的高低分别促进锂云母和透锂长石的产出;在富Li体系中,随着压力的降低可以发生白云母到锂云母的转化,指示出自然界中白云母的锂云母边可能形成于熔体或热液结晶过程中,不一定是热液蚀变的结果。