Molecular Dynamics Simulation of Rutile TiO_2 and Potassium Hexatitanate (K_3Ti_6O_(13)) Crystal

This paper presents the results of molecular dynamics (MD) simulation on the rutile titanium dioxide and potassium hexatitanate (K2O.6TiO2 or K2Ti6O13) crystal. The interaction of atoms is described by two-body central force interatomic potential, which includes Coulombic term, Gilbert-type repulsion term, van der Waals term and Morse-type potential. The optimized crystal structure of rutile TiO2 is in very good agreement with the experimental data in the literature. The present MD simulation also gives several physical properties, including volume thermal expansivity and elastic bulk modulus.     

K-doped CuO/ZnO with dual active centers of synergism for highly efficient dimethyl carbonate synthesis

The application of heterogeneous catalysts in dimethyl carbonate (DMC) synthesis from methanol is hindered by low activation efficiency of methanol to methoxy intermediates (CH₃O*), which is the key intermediate for DMC generation. Herein, a catalyst of alkali metal K anchored on the CuO/ZnO oxide is rationally designed for offering Lewis acid–base pairs as dual active centers to improve the activation efficiency of methanol. Characterizations of CO₂-TPD, NH₃-TPD, XPS, and DRIFTS revealed that the addition of Lewis base K observably boosted the dissociation of methanol and combined with Lewis acid CuO/ZnO oxide to adsorb the formed CH₃O* stably, thus synergistically promoted the transesterification. Finally, the CuO/ZnO-9%K₂O catalyst exhibited the optimal catalytic activity, achieving a high yield of 74.4% with an excellent selectivity of 98.9% for DMC at a low temperature of 90°C. The strategy of constructing Lewis acid–base pairs provides a reference for the design of heterogeneous catalysts.     

Superfine Spherical Hollow Ammonium Dihydrogen Phosphate Fire-Extinguishing Particles Prepared by Spray Drying

Superfine spherical hollow ammonium dihydrogen phosphate fire-extinguishing particles are prepared by spray drying and modified in situ with silicon oil emulsion. The results show that the amount of rough particles increased observably when the proportion of silicon oil emulsion is increased from 9 to 15 wt%, while no significant difference is detected when the proportion of silicon oil emulsion was varied from 0 to 9 wt%. The flowability of particles is improved with an increase in the proportion of silicon oil emulsion; 9.0 wt% is the optimal proportion of silicon oil emulsion for improving the hydrophobic performance of particles. Fire-extinguishing tests show that the fire-extinguishing capability of spray-dried superfine spherical hollow ammonium dihydrogen phosphate fire-extinguishing particles is much better than the two varieties of existing superfine dry chemical fire-extinguishing agents.     

碳酸钾生产中除氨新工艺实验研究

现有碳酸钾生产工艺中采用蒸发除氨,由于除氨不彻底,导致蒸发二次蒸汽中含有大量氨气和二氧化碳,使蒸发器的传热系数大大降低,从而增加了蒸发能耗;另一方面,挥发出的氨气和二氧化碳又难以集中回收,造成资源浪费,且增加原料成本费用。采用解吸法除氨,对料液温度、气液比、喷淋密度、气提时间、初始浓度等因素进行研究。实验结果表明,对于定量的处理料液,料液温度、气液比、喷淋密度、气提时间对碳酸氢铵分解影响较大,初始浓度对其影响较小。最佳工艺参数：料液温度为85 ℃、气液体积比为30∶1、喷淋密度为55 m³/（m²·h）,汽提时间为2.5 h,此时除氨率为95.48%。     

一种钾钙肥中钾、钙的溶出行为研究

以水和一定浓度的酸溶液为浸取液,测定了钾钙肥中的钾、钙在不同振荡温度、不同振荡时间和不同pH值下的溶出率,并分析其溶出规律;模拟植物吸收养分,测定了钾、钙的累积溶出率,验证了其缓释性,为钾钙肥的使用提供依据.     

合成氨装置苯菲尔脱碳工艺改造总结

阐述大型合成氨装置脱碳系统的改造情况,分析改造前脱碳系统运行中存在的问题,介绍脱碳系统改造内容及改造后的运行情况,并总结改造后的工艺效果。     

重铬酸钾标准滴定制备液浓度的不确定度评定

依照国标JJF1059—1999《测量不确定度评定与表示》等规范的规定,对重铬酸钾标准滴定制备液浓度进行不确定度评定,以期找出影响制备该溶液浓度不确定度的主要因素,提高制备质量,并为下一步使用该溶液对样品进行检测做不确定度评定时提供必要的上一级不确定度信息。经评定,制备C（1／6K2Cr207）=0．05000mol·L^-1。溶液浓度扩展不确定度为0．00007mol·L^-1,K=2。不确定度评定结果表明,对本制备液浓度不确定度贡献最大的是溶液体积,其次是重铬酸钾基准物质的纯度,在制备时应加以重视。     

火焰光度法测定亚硝酸钾中钠离子分析方法的探讨

火焰光度法测定亚硝酸钾中钠离子,由于标准溶液与待测溶液基体不一致,钾对钠的分析结果带来较大误差。为了抑制钾对钠的干扰,在配制钠标准溶液时,采用钾与钠之比与试样中的比例接近。     

Differential Activity of Plasma and Vacuolar Membrane Transporters Contributes to Genotypic Differences in Salinity Tolerance in a Halophyte Species,Chenopodium quinoa

Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd.), a facultative C3 halophyte species, can efficiently control the activity of slow (SV) and fast (FV) tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na⁺ is safely locked in the vacuole (Bonales-Alatorre et al. (2013) Plant Physiology). This work extends these finding by comparing the properties of tonoplast FV and SV channels in two quinoa genotypes contrasting in their salinity tolerance. The work is complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue. Our results suggest that multiple mechanisms contribute towards genotypic differences in salinity tolerance in quinoa. These include: (i) a higher rate of Na⁺ exclusion from leaf mesophyll; (ii) maintenance of low cytosolic Na⁺ levels; (iii) better K⁺ retention in the leaf mesophyll; (iv) a high rate of H⁺ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v) the ability to reduce the activity of SV and FV channels under saline conditions. These mechanisms appear to be highly orchestrated, thus enabling the remarkable overall salinity tolerance of quinoa species.     

高铁酸钾的制备工艺研究与表征

高铁酸钾是一种新型绿色高效的水处理剂,为了探索经济、高效的制备高铁酸钾的工艺,以次氯酸钙为主要原料通过氧化反应制备高铁酸钾,考察反应时间、反应温度、次氯酸钙用量、重结晶温度和碱度等因素对产率的影响,并采用红外光谱对产物高铁酸钾进行表征。实验结果如下：当反应温度为25 ℃,次氯酸钙的用量为理论值的1.2倍,反应时间为40 min,在冰水浴中重结晶时,反应产率可达75%以上;红外光谱（FT-IR） 对产物的结构表征证明合成产物为高铁酸钾。结果表明以次氯酸钙代替次氯酸钠制备高铁酸钾的工艺是可行的。