铬酸钾-碳酸钾高效分离研究Ⅰ.相图分析与溶解度计算

铬酸钾-碳酸钾的高效分离是铬盐清洁工艺亚熔盐介质再生的重要环节.据K2CrO4-K2CO3-H2O体系溶解度分析,蒸发结晶是该分离过程控制的关键,对此进行了详细的相图分析.选用Pitzer模型的HW公式,以二元电解质溶液的Pitzer参数推算了100℃时K2CrO4-K2CO3-H2O体系相平衡情况,理论计算结果与实验结果吻合较好,最大相对误差为16.26%,平均相对误差为7.39%.     

盐析结晶法分离铬酸钾

关联了不同温度下K2CrO4在K2CrO4-KOH-H2O体系中的溶解度数据,分析了从K2CrO4-KOH-H2O体系中通过盐析结晶方式分离K2CrO4的可能性;通过K2CrO4-KOH-H2O体系中K2CrO4的盐析结晶实验,得出了初级成核现象发生时,体系的最大过饱和度与过饱和速率之间的动力学关系式及结晶过程中盐析剂浓度、盐析结晶终点K2CrO4收率、溶液体积等工艺参数间的关系,探讨了以KOH作为盐析剂,采用盐析结晶方法从K2CrO4-KOH-H2O体系中分离提纯K2CrO4的可行性,为K2CrO4的高效分离提供了一种新思路。     

40℃和75℃下三元体系NH4HCO3-NH4VO3-H2O中NH4VO3溶解度的测定

针对钾系亚熔盐法钒渣钒铬共提清洁生产工艺的中间产品钒酸钙,提出通过碳化铵化/冷却结晶将钒酸钙转化为钒氧化物产品的新方法。分别研究了NH4HCO3-NH4VO3-H2O三元体系在碳化反应温度(75℃)和结晶沉钒温度(40℃)时NH4VO3的溶解度,得到了此时NH4VO3的溶解度数据。40℃时,NH4VO3溶解度随NH4HCO3浓度升高而降低。75℃时,NH4VO3溶解度则随NH4HCO3浓度升高呈U形变化。通过对比两个温度下NH4VO3的溶解度曲线,验证了碳化铵化工艺75℃反应、40℃结晶的设计思路。并经过理论计算,得到NH4VO3的理论一次结晶率为92.71%。再由得到理论结晶率时的反应和结晶NH4HCO3浓度,优化了钾系亚熔盐法钒渣钒铬共提清洁生产工艺中钒转化单元的工艺路线,绘制了工艺原则流程图。     

铬盐清洁工艺亚熔盐介质脱除铝酸钾、碳酸钾研究I.——溶解度

脱除铝酸钾、碳酸钾等杂质是铬盐清洁工艺亚熔盐介质循环利用的重要环节.作者测定了40℃及95℃KOH-K2CO3-Al2O3-SiO2-H2O体系部分溶解度,确定该体系存在K2O·Al2O3·3H2O(即 KAlO2·1.5H2O)与K2CO3·1.5H2O等平衡固相,为亚熔盐介质的冷却结晶除杂过程控制提供了热力学依据和指导.     

铬盐清洁工艺亚熔盐介质脱除铝酸钾、碳酸钾研究Ⅰ．——溶解度

脱除铝酸钾、碳酸钾等杂质是铬盐清洁工艺亚熔盐介质循环利用的重要环节。作者测定了40℃及95℃KOH-K2CO3-Al2O3-SiO2-H2O体系部分溶解度,确定该体系存在K2O.Al2O3.3H2O(即KAlO2.1.5H2O)与K2CO3.1.5H2O等平衡固相,为亚熔盐介质的冷却结晶除杂过程控制提供了热力学依据和指导。     

二次(盐析)结晶技术在铬酸钾清洁生产中的应用研究

介绍了K2CrO4清洁生产中的二次(盐析)结晶工艺技术。根据0℃、30℃和60℃时K2O-CrO3-H2O体系的溶解度数据,拟合出了K2CrO4在KOH溶液中溶解度的解析式;并结合二次(盐析)结晶过程的物料平衡关系,推导出了各工艺参数的估算式。通过对工艺实验结果的分析与对比,验证了估算方法的可靠性以及二次(盐析)结晶工艺路线的可行性。表明二次(盐析)结晶技术在铬盐清洁生产中,具有良好的应用前景。     

铬酸钾电解-结晶制备重铬酸钾的工艺

利用阳离子膜,以K2CrO4电解结晶制备K2Cr2O7,考察了电流密度、温度、阴极液KOH浓度、阳极液K2CrO4浓度等因素对转化率、电流效率和直流能耗的影响;研究了K2Cr2O7不同浓度、不同转化率下的结晶纯度和收率及搅拌速率、降温速率和晶种加入量等对晶体粒度分布和形貌的影响. 结果表明,最佳电解工艺条件为：电流密度0.2 A/cm2,电解温度80℃,阴极液KOH浓度50 g/L,阳极液K2CrO4浓度400 g/L. K2Cr2O7转化率大于90%时,结晶纯度不低于99.8%. 优化的结晶条件为：溶液初始K2Cr2O7浓度500 g/L,搅拌速率300 r/min,降温速率0.5℃/min,不添加晶种. 所得产品符合GB 28657-2012要求.     

铬酸钾-碳酸钾高效分离研究Ⅱ.结晶工艺实验研究

针对铬酸钾碳化法生产重铬酸钾母液利用过程,研究了K2CO3-K2CrO4-H2O体系蒸发-冷却结晶过程工艺条件。发现控制过饱和度的产生速率是过程控制的关键,少量铝、硅杂质的存在会在一定程度上抑制成核。铬酸钾的回收率可达95%以上,实现了碳酸钾与铬酸钾的高效分离。     

熔盐法活化处理含铬红土镍矿浸出液的铬铝分离及碱液循环

基于Na2CO3, Na2CrO4, NaAlO2在NaOH溶液中的溶解度及NaAlO2的性质,采用蒸发结晶、碳化沉铝、苛化等方法对浸出液中铬、铝进行了分离,并实现了碱液循环. 结果表明,采用分步结晶,一次蒸发排盐终点控制碱液浓度在40%(w),结晶相中为大量NaAlO2和少量Na2CrO4;二次蒸发碱液浓度控制在50%(w),结晶相中为大量Na2CrO4和少量Na2CO3. 一次排盐结晶相溶解后通过碳化方式将铝分离,深度碳酸化后NaAlO2分解率达90.8%;二次排盐结晶相溶解后在90℃、苛化1 h、加钙量为理论量的1.2倍时,苛化率达79.2%,苛化液蒸发后过滤得到较纯的Na2CrO4晶体.     

由铬酸钾制备铬酸钠结晶分离过程研究

以铬酸钾中间体为原料,系统地研究了采用结晶分离等常规手段制备铬酸钠产品的清洁制备方法。应用等温法分别测定了KNO3在Na2CrO4水溶液中和Na2CrO4在KNO3水溶液中的相平衡数据,绘制了溶解度曲线,确定采用先冷却结晶后蒸发结晶的方法制备铬酸钠晶体产品。考察了冷却结晶终点温度和物料配比,分析了分步蒸发结晶产品,确定了结晶最佳操作条件:K2CrO4与NaNO3的质量比在1∶(0.9～1.2),冷却结晶的终点温度控制在4℃。提出铬酸钾通过结晶方式转化为铬酸钠的整体工艺流程,并进行了全流程循环实验。采用重结晶法对铬酸钠产品进行精制,获得高纯度的铬酸钠晶体,质量分数由81.4%提高到92.2%,且粒径较大,粒度均匀。     

维生素K_4的合成

以２－甲基－１，４－萘醌、醋酸酐为主要原料一步合成维生素Ｋ４。考察了回流温度与回收率的关系，用水代替部分乙醇（９５％）精制的精制方法及经济效益。得出了用１０％水代替乙醇精制是可行的，给出了实际操作时各主要原料的投入比。实验表明此合成路线简单，回收率高达７０％～７４％。     

Thermal behavior of mullite between 4 K and 1320 K

The evolution of metric parameters of 2:1 and 3:2 mullites have been measured between 4 K and 1320 K using neutron and X‐ray powder diffraction. Negative thermal expansion was observed at low temperature for the a‐cell parameter and consequently for the cell‐volume, which is more pronounced for 2:1 mullite than those for 3:2 mullite. Each parameter is simulated using Grüneisen first‐order approximation for the zero pressure equation of state at 0 K, where the vibrational energy was calculated using microscopic approach. While the b‐ and c‐cell parameters require only one Debye term, a second Debye spectrum with negative Grüneisen parameter was required to fit the a‐cell parameter as well as the cell volume. At 4 K, 300 K and 1320 K the model, respectively, calculates the volume thermal expansion coefficients of 0.09x10^?6 K^?1, 9x10^?6 K^?1, and 17.3x10^?6 K^?1 for 2:1 mullite, and 0.09x10^?6 K^?1, 8.7x10^?6 K^?1, and 17.3x10^?6 K^?1 for 3:2 mullite. Temperature‐dependent Raman spectra and phonon density of states hint for the possible microscopic sources of the cell contraction at low temperature. A simple polynomial approach is presented to calculate the elastic stiffness coefficients of the 3:2 mullite, which are not available from experiments.     

Phase transition in K2SO4 AT 56 K

Specific heat and dielectric constant of K₂SO₄ were measured below room temperature down to liquid helium temperature. A phase transition was detected at 56 K, which is accompanied with a slight λ-type anomaly in specific heat and a break on dielectric constant vs. temperature curve. Evidence for the incommensurate or super structure was not confirmed by neutron diffraction.     

K2NiF4结构固溶体颜料的研究

基于稀土铝酸盐铬掺杂的研究，扩展到了对Ｋ２ＮｉＦ４结构的ＣａＮｄＡｌ１－ｘＣｒｘＯ４固溶体的研究，Ｃｒ３＋取代部分Ａｌ３＋离子后，固溶体的颜色加强     

石膏两步法制硫酸钾中CaCO3及K2SO4结晶动力学研究

本文实验研究了石膏与氯化钾两步转化法生产硫酸钾中停留时间、进料质量分数及搅拌速率等重要操作参数对CaCO3、K2 SO4 结晶动力学的影响规律 ,得到相应的二次成核动力学方程式 ,其结果可为石膏两步法制硫酸钾工业化结晶器的设计与放大提供基础数据     

K2SO4-Na2SO4系统相变材料的热物性分析

利用已有的热力学数据,对硫酸钠和硫酸钾相变材料的热力学稳定性、饱和蒸汽压等热物性进行了计算分析,探讨了莫来石作为硫酸盐相变材料基体的可行性.由热力学计算和分析可以看出,硫酸钠和硫酸钾在1100℃的高温下发生分解反应的平衡常数都极小,很难发生分解.硫酸钠即使在1200℃的饱和蒸气压也很低,是一种很有前途的相变材料,同时混合熔盐也表现出了非常低的蒸气压,计算数据和实验的热失重分析相吻合.研究结果表明,通过热物性相关参数的设计计算可以为相变储能材料的实际应用提供依据.     

K3PO4-mediated one-pot synthesis of symmetrical trithiocarbonates

A new procedure has been developed for synthesis of symmetrical trithiocarbonates by one-pot reaction of carbon disulfide, and various alkyl halides in dimethylformamide using K₃PO₄ as an inexpensive and effective reagent.     

INFLUENCE OF K+ AND NA+ IONS ON DIRECT ELECTROSYNTHESIS OF SOLID K2FEO4 AND COMPARISON OF THE PHYSICOCHEMICAL PROPERTIES OF K2FEO4 SAMPLES

The influence of K⁺ and Na⁺ ions on the direct electrosynthesis of solid K₂FeO₄ was investigated in 14 M OH^? solutions. At 50 or 60°C, the maximum current efficiency of electrosynthesis is obtained in 9 M KOH +5 M NaOH solution. The maximum current efficiency of 64.9% is obtained at 60°C in 9 M KOH +5 M NaOH solution, similar to the maximum value of 63.9% at 70°C in 14 M KOH solution in the temperature ranges studied. The result shows that the temperature at which the maximum current efficiency is obtained in 9 M KOH +5 M NaOH is much lower than that in 14 M KOH. Solid K₂FeO₄ powders directly electrosynthesized in 9 M KOH +5 M NaOH and 14 M KOH solutions were characterized by Fourier transform-infrared spectrometry (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), and their electrochemical performance was investigated by means of galvanostatic discharge. The result shows that the two samples have similar physical properties and discharge performance.     

Determination and correlation solubility of 4-nitroimidazole in twelve pure solvents from 278.15 K to 323.15 K

In this paper, the solubility of 4-nitroimidazole in twelve pure solvents (toluene, benzene, 1,4-dioxane, acetonitrile, ethyl acetate, acetone, GBL, ethanol, methanol, n-butanol, DMF and NMP) were determined by using the laser monitoring system from 278.15 K to 323.15 K under 101.1 kPa, which are 0.00018-0.00070, 0.00021-0.00073, 0.00034-0.00092, 0.00038-0.00142, 0.00047-0.00120, 0.00126-0.00303, 0.00225-0.00517, 0.00310-0.00724, 0.00467-0.00982, 0.00453-0.01940, 0.01947-0.04652, and 0.04670-0.07452, respectively. At constant temperature, the mole fraction solubility of 4-nitroimidazole were increased as the following order: toluene < benzene < 1,4-dioxane < (ethyl acetate or acetonitrile) < acetone < GBL < ethanol < (methanol or nbutanol) < DMF < NMP, and the solubility of 4-nitroimidazole in (ethyl acetate, acetonitrile) and (methanol, n-butanol) had an intersection point at 297.55 K and 281.85 K, respectively. The solubility of 4-nitroimidazole could be increased with increasing temperature in twelve pure solvents. The ideal model, modified Apelblat equation, polynomial empirical equation, and λh equation were used to correlate the experimental values. The experimental solubility values were employed to calculate the standard dissolution enthalpy, standard dissolution entropy and Gibbs energy. The dissolution of 4-nitroimidazole could be an endothermic process in twelve pure solvents. The determination and fitting solubility of 4-nitroimidazole have important guiding significance for the purification and crystallization of its preparation process.