同位素水精馏非稳态过程制备低氘水的研究与应用

根据水精馏过程中氢、氧稳定同位素的分离特性,以及同位素精馏的稳态和非稳态级联过程的理论分析和研究,应用于水精馏法生产重氧(18O)水的分离过程,在连续生产重氧(18O)水的同时,间歇副产低氘水,使一套同位素分离装置能同时制备二种同位素产品,开发了同位素水的综合制备的技术,提高了分离装置的有效利用率.     

水精馏法浓缩O~(18)研制小结

本实验是根据化工部(78)化二字733号文下达任务,建立水精馏法分离隐定性同位素O~(18)实验装置,并制备28％O~(18)产品。一、一般情况介绍自然界中,氧有三种稳定性同位素,质量数分别为16、17、18,它们的含量分别为99.765％、0.036％、0.199％。氧稳定性同位素的主要用途是做示踪原子,因为无放射性,对人体无损害,所以被人们广泛采用做际记化合物。     

重氢重氧水制备重氧水，副产重水的方法研究

以重氢重氧水(D:35.1 atom%;~(18)O:97.2 atom%)为同位素原料,先通过氢氧气发生器获得D_2和~(18)O2,再将D_2、~(18)O_2分别通入石英管在催化剂催化作用下与过量高纯氧气/高纯氢气反应,合成得到35.1 atom%重水和97.2 atom%重氧水。结果表明,该方法具有同位素丰度稀释少,易调节的优点,可以作为水精馏法生产重氧水的后处理工艺,并可以副产一定丰度重水。     

NiO/α-Al2O3催化剂用于模拟汽油选择性加氢脱二烯反应的性能

以微波辐射法制得的大比表面积α-Al₂O₃为载体,负载一定量NiO制备得到NiO/α-Al₂O₃催化剂,采用固定床微反实验装置评价NiO/α-Al₂O₃催化剂用于模拟汽油选择性加氢脱二烯反应的性能,并对载体和催化剂进行XRD和BET表征。结果表明,用微波辐射法制得的Al₂O₃具有α-Al2O3的物相和大比表面积,负载NiO后的NiO/α-Al₂O₃催化剂对模拟汽油选择性加氢脱二烯具有较好的反应性能,适宜的NiO负载质量分数为24%。通过对反应条件的考察,得出24%NiO/α-Al2O3催化剂的适宜反应条件为反应温度80 ℃,常压,空速5.5 h^-1,氢油体积比100∶1。     

计算机模拟在甲醇——水精馏塔设计中的应用

利用化工通用模拟软件对甲醇——水精馏过程进行设计计算,通过灵敏度分析功能对操作条件进行优化,当采用25块理论板,回流比取1.43,在第12块塔板进料,塔顶馏出液采出率为0.427时,可以达到较好的分离效果。     

乙醇-水体系分离提纯过程新技术的研究

首先拟合了Aspen Plus中乙醇-水的二元交互参数,使其计算结果更符合实际。其次通过分析乙醇-水精馏二塔(C31103)与新型吸附系统工艺流程,计算了C31103与吸附系统的主要能耗,得到了二者关于C31103塔顶采出中乙醇质量分数x_D的关系式。并计算得到淡酒量和塔顶采出量关于x_D的关系式。运用Aspen Plus软件对C31103进行稳态优化,计算出x_D在0.945～0.88之间时的能耗与x_D的关系,确定最适宜x_D为0.9～0.92,并通过模拟得到各x_D下的淡酒量和塔顶采出量等结果,比较淡酒量的计算结果和模拟结果,得到相对误差小于4%,证实了能耗模型的准确性。     

达比加群酯-d3的合成

研究抗凝血药物达比加群酯-d₃的合成工艺。以4-氯-3-硝基苯甲酸甲酯为起始原料，氘代甲胺盐酸盐为氘代试剂，经氘代甲基化、取代、还原、缩合、环合、水解、亲核等反应得到关键氘化中间体3-{[(2-{[(4-氰基苯基)氨基]甲基}-1-(甲基-d₃)苯并咪唑-5-基)氧亚基](吡啶-2-基)氨基}丙酸乙酯，而后再经氨解和亲核反应，成功制备稳定的达比加群酯-d₃,8步反应总产率为6.4%,目标化合物结构经NMR和MS确认，同位素丰度达99.7%。该合成方法原料简单易得、操作简便、重现性好，可用于达比加群酯-d₃的合成。     

萃取法从盐湖卤水提取铷实验研究

研究了t-BAMBP［4-叔丁基-2-（α-甲基苄基）苯酚］/磺化煤油萃取体系,从提铯后的母液中,萃取分离钾铷的过程。考察了萃取时间、萃取剂浓度、萃取相比等萃取条件、水洗条件和反萃取条件对铷钾分离的影响。确定了适宜的工艺条件为：t-BAMBP浓度为0.7 mol/L,相比O/A=3∶1,萃取时间为5 min;以0.1 mol/L氯化钠溶液为洗涤剂,洗涤相比O/A=4∶1;以0.5 mol/L 氯化氢溶液为反萃剂,反萃相比O/A=5∶1。经过5级逆流反萃,铷的反萃率达到95.6%以上,铷钾的分离系数较高,实现了铷钾分离。     

LPCE法同位素分离制备低氘水的工艺研究

液相催化交换(LPCE)法是一种操作方便高效的氢同位素分离方法。本文对LPCE法同位素分离制备低氘水的工艺进行了深入的实验研究。通过研究发现,在液相催化交换方法(LPCE)生产低氘水过程中,如果气液比达到1.5,随着温度的递增,总体积传质的系数Kya值会先升高后降低。而当反应温度一旦超过60℃,这一系数会持续地下降,因此,60℃被认为是最佳的反应温度。此外,LPCE方法在制备低氘水时候,最优气液比会因交换反应温度的不同而有所变化。气液比的增大会导致总体积传质系数Kya值上升,但是过高的气液比可能会导致气液带动,可能进一步引发液泛,从而使交换反应效率反而下降。     

H2/HD/HT电解-精馏级联分离过程理论分析

为研究电解精馏级联氢同位素分离过程的规律性,建立了理论模型,并以H2/HD/HT为对象计算研究了系统分离行为。获得了电解和精馏过程系统的浓集行为： 电解池中HDO浓度从2.88×10-4 增长到 8.35×10-4, HTO浓度从1.0×10-6 增长到6.34×10-6;精馏柱再沸器中HD浓度达到0.033,HT浓度达到6.06×10-5。由于H/D和H/T电解池分离因子的差异,63.4%的HTO仍然留在电解池中,造成精馏柱再沸器中HT浓缩倍数不如HD。随时间的增长,脱氘（氚）率下降。     

The steady-state and dynamic simulation of cascade distillation system for the production of oxygen-18 isotope from water

Accurate simulation of water distillation system for oxygen-18(18O) isotope separation is necessary to guide industrial practice, since both deuterium(D) and oxygen-18 isotope get enriched and interfere with each other. In the present work, steady-state and dynamic distillation models are established based on a classic method and a cascade distillation system with 5 towers is introduced to test the models. The theoretical expressions of separation factor αH/Dfor protium/deuterium and separation factor α~(16)O/~(18) O.for oxygen-16/oxygen-18 were derived,with the existence of deuterium and oxygen-18, respectively. The results of the steady-state simulation by the classical method proposed in the present work agreed well with the results of the lumping method. The dynamic process could be divided into 5 stages. Impressively, a peak value of product withdraw was observed before the final steady state, which was resulted from the change of ~(16)O/~(18) O separation factor and isotope distribution. An interesting low concentration zone in the towers of T2–T5 existed at the beginning of the dynamic process and it required industrial evidence.     

Multistage Process of Deuterium and Heavy Oxygen Enrichment by Membrane Distillation

Abstract

Deuterium and oxygen-18 isotope enrichment in water by membrane distillation were studied in a 4-stage cascade. Two configurations of membrane distillation (MD) employing PTFE-flat-sheet membranes were investigated, including direct contact MD and air gap MD. The first, direct contact MD is more efficient. It is characterized by high distillate flow rate. The temperature polarization coefficients were higher for direct contact MD. H/D and ¹⁶O/¹⁸O separation factors were determined in the 4-stage cascade.     

Process design considerations and steady-state operational data for the separations of isotopes of oxygen

Operational data for the separation of oxygen isotopes are given on flow rates, concentrations and concentration profiles of the isotope separation plant of the Weizmann Institute of Science which has reached steady-state operational conditions with regard to the rare and more difficult to separate oxygen-17 isotope. This plant consists of two sections, namely packed distillation columns and thermal diffusion columns. Data on the columns and packing characteristics are given. The concentrations reached in the distillation section are up to 98% of oxygen-18 and up to 20% of oxygen-17. In the thermal diffusion section, concentrations of oxygen-18 up to 99.9% and of oxygen-17 up to 96% have been attained.     

Estimation of deuterium recoveries from each component of water-isotope mixture in continuous-flow thermal diffusion columns

The present study deals with the estimation of deuterium recovery from the separation of water-isotope mixture (H₂O-HDO-D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O-HDO-D₂O system were derived. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O. The most important assumption in this work was that the concentrations of each component were at local equilibrium within the thermal diffusion column, i.e. H₂O + D₂O ? 2HDO. It was found that D₂O preferably transfers to the bottom end of the column, while HDO does the same for dilute feed concentration, but then transfers to the top of the column when the feed concentration of D₂O, C_3F, increases to 0.3. The maximum total recovery of deuterium from HDO and D₂O occurs at C_3F = 0.25.     

Analysis of oxygen sources and reaction pathways of carbon support corrosion at the cathode in PEMFC using oxygen-18 DEMS

Oxygen gas, water used to humidify the gases, and surface oxides originated from the carbon black and catalyst preparation are the three possible oxygen sources contributing to carbon support corrosion (CSC) at the cathode in proton exchange membrane fuel cells (PEMFC). To discriminate among them, oxygen was isotopically labeled by replacing regular water with oxygen-18 (¹⁸O) enriched water (H₂¹⁸O, 98%) in differential electrochemical mass spectrometry (DEMS). The DEMS spectra of the cathode exhaust gases O₂, O¹⁸O, ¹⁸O₂, CO₂, CO¹⁸O and C¹⁸O₂ (m/z equal to 32, 34, 36, 44, 46 and 48 correspondingly), sampled by a mass spectrometer during cyclic voltammetry (potential cycled for 100-1400 mV at the rate of 10 mV s⁻¹) and chronoamperometry, were analyzed to identify the sources of oxygen, identify mechanistic pathways, and classify the surface oxides on carbon for CSC.It was found that water is the main direct oxygen source for CSC. Water reacts with carbon to produce at least three types of carbon surface oxides, which are then further oxidized with water to produce CO₂ in different potential ranges.     

Preparation and characterization of Zn18O/Zn16O isotope heterostructure thin films

An oxygen isotope-based heterostructure zinc oxide (ZnO) thin film, Zn¹⁶O/Zn¹⁸O/Zn¹⁶O, was made by pulsed laser deposition on an a-face sapphire substrate. The isotope-enriched Zn¹⁸O layer was made by irradiation of the isotope oxygen radical (¹⁸O^*). The isotopic ratio in the heterostructure film was analyzed via secondary ion mass spectroscopy (SIMS). The ratio of exchange from ¹⁶O to ¹⁸O was approximately 70% when the oxygen isotope was irradiated as a radical, while it was approximately 10% when the oxygen isotope was supplied as ¹⁸O₂ gas.     

The effect of additives on the practical electrolytic separation of hydrogen and deuterium. II. Separation factor at Hg in aqueous and non-aqueous media

Studies of the effects of additives on the electrolytic H/D separation factor,S _H/D, previously reported in Part I [2] for Pt and Fe electrodes, are extended to the case of Hg for which the mechanism of cathodic H₂ evolution is well established. The behaviour of urea and guanidine was investigated. In the case of urea, the separation factor at Hg is enhanced but decreases with increasing current density or cathodic potential. The dependence ofS _H/D on current density can be correlated with the diminishing surface excess of urea with increasing negative potential. Experiments with proton sources other than H₂O in liquid water were investigated by making measurements ofS _H/D from solutions of H₂O/HOD, CH₃COOH/CH₃COOD and CF₃COOH/CF₃COOD in CH₃CN with NaClO₄ as electrolyte. An interesting inverse H/D isotope effect arises with trifluoroacetic acid (TFA) as proton source; the effect is interpreted in terms of competitive reactions of H and D with TFA rather than unusual bonding and vibrational characteristics of the TFA activated complex. The results suggest that useful isotopic separations can be made by use of selective competitive reactions. A kinetic analysis of the inverse isotope effect is given.     

Separation of water–isotopes mixture in continuous-flow thermal diffusion columns for recovery of deuterium

The present study deals with the estimation of deuterium recovery from the separation of water–isotopes mixture (H₂O–HDO–D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O–HDO–D₂O system were derived by following the same procedure performed in the previous work. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O and confirmed with the experimental results.