Activation of Pozzolanic Reaction of Hydrated Portland Cement Fly Ash Pastes in Sulfate Solution

The activation of the pozzolanic reaction of fly ash in portland cement paste immersed in sulfate solution has been studied. Mixtures of two Spanish fly ashes (ASTM class F) with 0%, 15%, and 35% replacement of portland cement by fly ash were immersed in Na₂SO₄ solution, of 2880 ppm SO₄²⁻ concentration, for a period of 90 days. The resistance of the different mixtures to the sulfate attack was evaluated using the Koch-Steinegger test. The results showed that all of the mixtures were sulfate resistant, despite the high Al₂O₃ content of the fly ash. The diffusion of SO₄²⁻ and Na⁺ ions through the pore solution activated the pozzolanic reactivity of the fly ashes, causing microstructural changes, which were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition.     

Anodic Reaction of Arsenopyrite in Ammoniacal Solution

1 INTRODUCTIONArsenopyrite is the most common sulfide mineral in arsenic refractory gold ores. The ore refractoriness mainly results from dissemination of fine grained gold in arsenopyrite and other sulphide minerals. Oxidation of sulfides by either pyro-metallurgical or hydrometallurgical tech- niques to render these ores amenable to the standard cyanidation is therefore universally effective in gold extraction. A newly developed pretreating technology for arsenopyrite-type ores is oxyge…     

季戊四醇反应液HPLC分析

季戊四醇反应液成分复杂,检测困难是长期未能解决的课题,经多种方法对比,不断探索,找到HPLC检测条件:固定相用ODS(YWG-C18),柱温为30℃,移动相是0.4%HAC水溶液,流速1.00mL/min,折光示差检测器。结果具有高准确性和良好重现性     

Nickel Activation for Hydrogenolysis Reaction on USY Zeolite

The effects of the SAR (14 and 38) and of the methodology of introduction of nickel (wetness impregnation and ion exchange) on catalyst activation were investigated in Ni/USY model catalysts submitted to two activation treatments: reduction (A) and reduction/calcination/reduction, successively (B). the catalysts prepared by wetness impregnation, a marked increase in the catalytic activity after treatment B was observed. On the basis of the catalyst efficiency toward ethane hydrogenolysis, the lower SAR catalyst presents a threefold higher activity. On the contrary, the catalysts prepared by ion exchange, as well as a model catalyst prepared by wetness impregnation over a USY exhaustively exchanged with nickel ions, do not present measurable increasing of the catalytic activity under the same activation conditions. Monitoring the catalyst activation by EXAFS indicates the formation of nickel clusters in the impregnated catalysts after activation treatment B, which should be responsible for the high catalytic activity. However, TEM images reveal a bimodal particle size distribution, with large (ca. 20 nm) and small nickel particles. Temperature-programmed reduction performed under the same conditions of catalyst activation suggests that only the small nickel particles are activated under the experimental conditions adopted in this work.     

反相高效液相色谱法分析甲锭反应液中甲锭含量

用反向高效液相色谱方法建立了甲锭的分析检测方法,并分离了甲锭及其衍生物.以甲醇:水=40:60为流动相,流量0.12 mL·min-1,在Thermo-Hypersil ODS柱(2.1mm100 mm,3 tan),检测波长276 nm的色谱条件下,甲锭及其衍生物得到了很好的分离.在选用的色谱条件下,甲锭在0.5～10 nlg·mL-1检测范围内有良好的线性关系(R2=0.9998).在0.5 nag·mL-1、2.5 mg·mL-1和10 nag·mL-13个甲锭浓度,其相对标准偏差分别为1.311%、1.780%和0.861%.通过加标试验,甲锭在1 mg·mL-1和10 mg·mL-1两个浓度的相对标准偏差分别为2.717%和1.818%.本法操作简便、快速、准确,可适用于甲锭化合物的定性与定量研究.     

Reaction of Glasses with Hydrofluoric Acid Solution

The gravimetric method was used to study the reaction between fused silica and silicate glasses with HF acid solution. The reaction was found to be transport-controlled. Additions of Al₂O₃, CaO, or both to fused silica caused a reduction in corrosion resistance of the resulting glasses.     

Davy甲醇合成塔反应不均衡问题分析与解决

Davy甲醇合成塔反应不均衡,通过对相关现象进行分析,找出其原因为中心管分布器堵塞导致气体分布不均,解决了催化剂床层温度分布不均,产量低、压差高等问题。     

Reaction of SDS with Ozone and OH Radicals in Aqueous Solution

Ozone can be used as an antiseptic in cleaning systems. SDS (Sodium Dodecyl Sulfate) has proved to be a suitable surfactant in such systems. However, kinetic studies have showed that SDS reacts with ozone at high concentrations. In contrast, the natural decomposition of ozone to oxygen is retarded at low SDS concentrations. NMR spectroscopic analyses of SDS solutions being continuously treated with ozone and OH radicals, respectively, have been performed. ¹H-, ¹³C-, COSY-, HMBC- and HSQC-NMR spectra were recorded showing that small carboxyl acids were formed at exposure to ozone. Randomly positioned carbonyl groups were also found along the hydrocarbon chain. However, the largest product was caused by direct reaction of SDS with ozone. The predominant product most likely is a SDS-peroxide. ¹H –NMR spectra of the samples treated with OH radicals also show the formation of small carboxylic and carbonyl groups. However, there is no indication of oxidation of the sulphate group.     

搪玻璃设备大面积爆瓷原因及应对措施

搪玻璃反应釜是化工企业的通用设备,爆瓷是其使用过程中较常见的问题。分析了由于设备本身的制造质量、使用操作不当等原因引起的大面积爆瓷现象,并针对不同原因造成的大面积爆瓷,提出了相应的预防和改进措施。     

丙烯腈气体与氢氧化钠溶液反应动力学

研究了鼓泡反应器中丙烯腈气体与氢氧化钠溶液的吸收反应过程.实验考察了丙烯腈气体在反应液中停留时问、反应温度及氢氧化钠溶液浓度对反应的影响,得到了该反应速率方程.其气液反应速率与丙烯腈气体浓度的1次方成正比,与NaOH溶液浓度的0.5次方成正比,反应活化能Ea值为36 kJ/mol,指前因子ko值为3.95×105s-1.     

粉煤灰提铝硅渣碱溶脱硅反应及其动力学

以内蒙古某酸法粉煤灰提铝硅渣为对象,研究了其在NaOH溶液中的非晶态SiO2的脱硅行为,通过脱硅反应中脱硅率随时间的变化,研究搅拌速度、反应温度、NaOH溶液浓度对脱硅率的影响.通过拟合实验数据,确定脱硅反应的动力学规律和宏观动力学方程,并计算相应的表观活化能.结果表明:搅拌速度对脱硅率影响较小,提高反应温度和NaOH...     

Trifunctional Squaramide Catalyst for Efficient Enantioselective Henry Reaction Activation

A new class of trifunctional squaramide catalyst acting by means of multiple interactions has been found in a study of the Henry reaction. Enantiomerically enriched nitroaldol products were obtained in good yields and high enantioselectivities under mild conditions using one of the smallest amounts of organocatalyst reported so far for this reaction (0.25 mol%). The catalyst was able to generate hydrogen bonding and anion‐π/hydrogen‐π interactions with the substrates, responsible of the improvement in the reactivity and the enantioselectivity of this process. Computational calculations support a mechanistic hypothesis based on an anion‐π effect, this being the first example reported in asymmetric catalysis.

     

固定床一维对流-扩散-非线性反应方程的数值解析

考虑内扩散和化学反应联合控制时的情况,将单一固体颗粒的综合速率方程推广到微元体,导出了化学反应项的更适用形式,建立了一维对流-扩散-非线性反应数学模型,求出了该模型的数值解,并以铁矿石的间接还原为例,讨论了不同条件下的反应转化进程. 结果表明,颗粒大小、对流是影响反应转化的重要因素,其影响程度可用Thiele数和传质Pe*数衡量. 由于Thiele数y与反应器长度的平方成正比,而传质Pe*与反应器长度成正比,因此反应器长度也是影响其自身性能的重要因素. 当比值y/Pe*增大时,对流作用下降,气体转化率增高.     

反相高效液相色谱法测定甲锭反应液中甲锭含量

用反向高效液相色谱方法建立了甲锭的分析检测方法,并分离了甲锭及其衍生物.以甲醇:水=40:60为流动相,流量0.12 mL/min,在Therrno Hypersil ODS柱(2.1x100mm,3um),检测波长276 nn的色谱条件下,甲锭及其衍生物得到了很好的分离.在选用色谱条件下,甲锭在0.5ug/mL～10ug/mL检测范围内有良好的线性关系(R2=0.9998).通过该方法的精密度考察,在O.5ug/mL,2.5ug/mL和10ug/mL三个甲锭浓度,其相对标准偏差分别为1.311%、1.780%和0.861%.通过加标试验,甲锭在1ug/mL和10ug/mL两个浓度的相对标准偏差分别为2.717%和1.818%.     

稳定亚氯酸钠溶液的活化研究

以稳定的亚氯酸钠溶液为研究对象,考察不同活化剂、活化pH及活化方式等因素对其活化率的影响。实验结果表明:选取活化能力强的盐酸作为活化剂,当稳定性亚氯酸钠溶液pH为0.5,活化时间为10min时,稳定性亚氯酸钠溶液的活化率高达91.59%;两种活化方式对最终活化率的影响较小。     

二甲戊乐灵反应液的高效液相色谱分析

采用HPLC法,以C18柱为固定相,甲醇-水(体积比7∶3)为流动相,检测器检测波长为250 nm,外标法定量,在室温条件下分离反应液中的3,4-二甲基苯胺、3-戊酮、二甲戊乐灵及其他组分,并准确测定其含量.3,4-二甲基苯胺的变异系数为19.15‰,回收率为97%～102%,线性范围为0.2～10 g/L;3-戊酮的变异系数为15.30‰,回收率为96%～102%,线性范围为0.2～10 g/L;二甲戊乐灵的变异系数为26.86‰,回收率为98%～104%,线性范围为0.2～10 g/L.     

偏高岭土在NaOH溶液中的反应过程与结构演变研究

从NaOH激发偏高岭土材料具有较低的力学强度这一问题入手,以偏高岭土和NaOH溶液为主要原材料,制备碱激发偏高岭土净浆.研究在不同温度下,不同搅拌时间对试样反应产物的影响以及微观结构的变化.本研究结果表明在-20℃、0℃和20℃三个温度下,随着搅拌时间的延长,最终的反应产物均为凝胶结构以及具有较高结晶度的沸石结构.     

气相色谱法同时测定缩合反应液中二苯基二氯硅烷和三苯基氯硅烷

建立了气相色谱同时测定缩合反应液中二苯基二氯硅烷和三苯基氯硅烷的方法。该方法以甲苯为内标物,在迪马DIKMA DM-5毛细管色谱柱上进行分离,氢火焰离子化检测器。方法的回收率98.5%~102%,相对标准偏差小于1.5%。