去氢枞酸固液溶解度及其反应-结晶耦合单离方法

采用激光监视技术判断平衡终点,由动态法测定了282~325 K去氢枞酸在甲醇、无水乙醇、正丙醇、正丁醇中的固液溶解度;应用λh模型、Wilson模型、简化模型分别对溶解度数据进行关联;采用超/亚临界CO_(2)强化胺化反应-结晶耦合方法单离去氢枞酸,以GC分析、熔点和旋光率检测去氢枞酸纯度。结果表明:去氢枞酸在4种醇类溶剂中的溶解度均随温度的升高而增大,其溶解度大小在不同溶剂中顺序为:正丁醇>正丙醇>无水乙醇>甲醇;去氢枞酸在4种醇类溶剂中的溶解度数据用λh模型、Wilson模型和简化模型关联的平均相对误差最大值分别为1.23%、2.15%和0.87%;通过正交试验得到超/亚临界CO_(2)强化胺化反应-结晶耦合单离去氢枞酸的最优反应条件为:反应时间50 min,反应温度308 K,CO_(2)压强7.5 MPa,溶剂乙醇体积分数50%,搅拌转速400 r/min,所得去氢枞酸的收率为81.85%,纯度为99.62%;去氢枞酸熔点为446.0~446.5 K,旋光率[α]^(20) _(D)为+62.2°。

超声波协同反应-结晶耦合单离脱氢枞酸

以歧化松香和2-乙醇胺为原料、乙醇为溶剂、超声波协同反应-结晶制备脱氢枞酸乙醇胺盐,经萃取、结晶、重结晶、酸化制得脱氢枞酸。通过正交优化实验,考察了溶剂浓度、反应温度、反应时间、超声波功率、搅拌转速对脱氢枞酸收率的影响,确定最佳单离条件为:反应时间50min,反应温度35℃,超声波功率500W,溶剂浓度50%,搅拌转速400r·min-1,在该操作条件下脱氢枞酸的收率达55·37%,纯度达99·53%。并探讨了脱氢枞酸胺化反应-结晶过程相态变化对反应平衡和选择性的影响,当反应温度分别为35℃和70℃时,胺化反应是在非均相和均相下进行,所得脱氢枞酸产品的纯度为99·53%和95·66%。采用GC、GC-MS、元素分析、UV、FT-IR、熔点仪和旋光仪对脱氢枞酸产品进行了分析鉴定,实验值与文献值吻合。

反应-结晶耦合单离脱氢枞酸过程研究?

以歧化松香和2-乙醇胺为原料,采用超声波强化的方法进行反应-结晶耦合单离脱氢枞酸过程研究。考察了反应时间、反应温度、超声波强度、溶剂浓度、搅拌转速、胺盐结晶溶剂浓度、重结晶次数及结晶方式对脱氢枞酸收率的影响,实验结果表明,超声波可以有效地强化歧化松香胺化反应-结晶过程,适宜的反应时间为40min、反应温度为35℃、超声波功率为300W、溶剂浓度为40%、搅拌转速为300r·min-1、胺盐结晶溶剂浓度为40%、胺盐重结晶次数为2~3次、结晶方式为自然结晶,所制得的脱氢枞酸收率为48.59%,纯度为99.28%。并对脱氢枞酸单离过程的收率、纯度和损失率进行了跟踪分析,其中胺化反应-结晶过程脱氢枞酸产品的损失率最大,其次是溶剂萃取过程,二者损失率分别为36.12%和10.94%。

化学反应-结晶法联用分离三苯基膦与三苯基氧膦

用化学反应-结晶联用法从Wittig反应废渣中回收三苯基膦和三苯基氧膦。废渣混合物经过酸处理、重结晶，分别得到三苯基膦和三苯基氧膦。考察了洗涤酸、结晶溶剂等对产品纯度和回收率的影响。结果表明，洗涤酸种类和稀酸浓度对结果无影响，重结晶溶剂选用氯苯较好，分离产物经红外、高效液相色谱和熔点分析，与文献值一致，产物纯度符合工业品要求。

反应-结晶耦合法生产硝酸钾的研究

探索了合成法制备硝酸钾的新工艺路线并对流程进行了模拟,通过将中和反应和结晶两个过程集成在同一结晶器中完成,实现反应-结晶过程的耦合,同时充分利用中和反应热为体系水分的蒸发提供能量,使能量得到更加合理利用,达到节能降耗的目的。

Cd(Ⅱ)-碘化钾-结晶紫-OP10反应的分光光度研究及应用

〔目的〕为研究灵敏而简便的环境水样中痕量镉测定技术。〔方法〕在表面活性剂OP -10存在下 ,镉与结晶紫、碘化钾形成混配缔合物 ,建立了测定水体中痕量镉的光度法。〔结果〕该缔合物的最大吸收波长在 63 5 .9nm ,表观摩尔吸光系数ε为 1.0 4× 10 6 L mol·cm ,回收试验的相对标准偏差为 1.15 % -2 .68% ,回收率为 99.0 % -10 0 .8% ,在 0 -1.0 μgCd/10ml范围内服从比尔定律。〔结论〕该体系是测定镉的超高灵敏度光度法之一。本方法用于环境水样及中镉的测定 ,获得了满意结果。

A dendritic Cu/Cu_(2)O structure with high curvature enables rapid and efficient reduction of carbon dioxide to C_(2) in an H-cell

Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction(HER).In this study,dendritic Cu/Cu_(2)O with abundant Cu^(0)/Cu^(+)interfaces and numerous dendritic curves was synthesized in a CO_(2)atmosphere,resulting in the high selectivity and current density of the C_(2)products.Dendritic Cu/Cu_(2)O achieved a C_(2)Faradaic efficiency of 69.8%and a C_(2)partial current density of 129.5 mA cm^(-2)in an H-cell.Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field,leading to a localized CO_(2)concentration.Additionally,DRT analysis showed that a dendritic struc-ture with a high curvature actively adsorbed the surrounding high concentration of CO_(2),enhancing the mass transfer rate and achieving a high current density.During the experiment,the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu^(0)/Cu^(+) on the catalyst surface,which resulted in improved ethylene selectivity.Under the optimal atomic ratio of Cu^(0)/Cu^(+),the charge transfer resistance was minimized,and the desorption rate of the intermediates was low,favoring C_(2) generation.Density functional theory calculations indicated that the Cu^(0)/Cu^(+) interfaces exhibited a lower Gibbs free energy for the rate-determining step,enhancing C_(2)H_(4) formation.The Cu/Cu_(2)O catalyst also exhibited a low Cu d-band center,which enhanced the adsorption stability of *CO on the surface and facilitated C_(2)formation.This observa-tion explained the higher yield of C_(2) products at the Cu^(0)/Cu^(+) interface than that of H_(2) under rapid mass transfer.The results of the net present value model showed that the H-cell holds promising industrial prospects,contingent upon it being a catalyst with both high selectivity and high current density.This approach of integrating the structure and composition provides new insights for ad-vancing the CO_(2)RR towards high-current C_(2) products.

Semi-batch Crystallization of 7-Amino-Desacetoxycephalos- poranic Acid

Semi-batch crystallization of 7-amino-desacetoxycephalosporanic acid (7-ADCA) is a complicated process, in which agglomeration occurs together with nucleation and crystal growth. To systematically study such a process, experiments were conducted to estimate the crystallization thermodynamics and kinetics, and then the process was simulated by a numerical method. The application of Monte Carlo concept in the algorithm to describe agglomeration event offers an alternative approach of solving the population balance, the intrinsic simplicity of which allows us to investigate several mechanisms and include several internal coordinates in the analysis. Furthermore, present study may be a valuable paradigm for other semi-batch crystallization processes.

Preparation of boric acid from low-grade ascharite and recovery of magnesium sulfate

Boric acid and kieserite were prepared from low-grade ascharite by sulfuric acid method.This method results in the recovery of 71.06%and 45.03%for boric acid and kieserite,respectively.Meanwhile,the boric acid was precipitated from the filtrate at low temperature and the solution was recycled without discharging waste liquid in the whole process.The influence of amount of sulfuric acid,mass fraction of sulfuric acid,reaction temperature and reaction time on the leaching rate of boric acid were studied. The results show that the leaching rate of boric acid reaches 93.80%under the following conditions:the amount of sulfuric acid is 85%of theoretical dosage;the mass fraction of sulfuric acid is 25%;reaction temperature is 95℃;and the reaction time is 100 min. Meanwhile,the effects of mass fraction of magnesium sulfate,crystallization temperature and crystallization time on the crystallization of kieserite were investigated and the optimal crystallization conditions are obtained:the mass fraction of magnesium sulfate is 28%;the crystallization temperature is 180℃and the crystallization time is 4h.

Secondary Crystallization of Na_2CO_3-Modified HZSM-5 Zeolites with Tetrapropylammonium Hydroxide and Their Catalytic Performance in Thiophene Alkylation Reaction

The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting samples were characterized by a complementary combination of X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, X-ray fluorescence spectroscopy, XPS, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, BET and temperature-programmed desorption techniques. The results showed that the secondary crystallization of the HZSM-5 zeolite could result in migration of non-framework species from the internal channels to the zeolite surface and their transformation into framework species. The catalytic activity of these modified samples for thiophene alkylation was evaluated. Both the activity and stability of the catalysts were improved after secondary crystallization.

Comparative experimental study on reactive crystallization of Ni(OH)2 in an airlift-loop reactor and a stirred reactor

The objective of this work is to study the reactive crystallization in an airlift-loop reactor （ALR） using the precipitation of Ni（OH）2 as a model reaction. The growth of Ni（OH）2 particles in an ALR and a stirred tank was quantified by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, laser particle analyzer, tap densitometer and optical microscope, and the growth process of Ni（OH）2 particles is analyzed. It is found that the Ni（OH）2 particles prepared in an ALR have a better sphericity than those in a stirred tank and the growth of Ni（OH）2 particle tap density mainly depends on the size of crystallites： the bigger the size of crystallites, the bigger the tap density is. Based on these, the growth process of Ni（OH）2 particles in ALR is elaborated. Crystallites precipitated from solution aggregate to form large particles with much void. These constituting crystallites continue to grow up, that takes up the void inside particles and makes the tap densitv increase.

Kinetics of Reaction-Crystallization of Struvite in the Continuous Draft Tube Magma Type CrystallizersmInfluence of Different Internal Hydrodynamics

A laboratory-scale reaction-crystallization process of struvite synthesis from diluted water solution of Mg^2＋, NH^＋ 4 and PO3- ions was studied. The research covered the tests of two original constructions of continuous jet-pump Draft Tube Magma （DTM）-type crystallizers with internal circulation of suspension （upward/downward）. Interactions between constructional, hydrodynamic and kinetic factors were established and discussed. Nucleation and linear growth rates of struvite crystals were calculated on the basis of population density distribution. Kinetic model of idealized Mixed Suspension Mixed Product Removal （MSMPR） crystallizer considering the size-dependent growth mechanism was applied （Rojkowski hyperbolic equation）. For comparison purposes the kinetic data corre- sponded to a simpler, continuous draft tube-type crystallizer equipped with propeller agitator were analyzed. It was concluded that crystal product of larger size was withdrawn from the jet-pump DTM crystallizer of the descending flow of suspension in a mixing chamber.

Enzymatic Hydrolysis of Cellulose with Different Crystallinities Studied by Means of SEC-MALLS

The reactions of exo-cellulase （cellobiohydrolase, CBH） and endo-cellulase （endoglucanase, EG） were investigated by analyzing the insoluble residues of microcrystalline cellulose （MCC） and filter paper cellulose （FPC） during enzymatic hydrolysis. Molecular parameters including molecular weight and its distribution, degree of polymerization, and radii of gyration were measured by size exclusion chromatography coupled with multi-angle laser light scattering. No significant change in MCC chains was found during the whole reaction period, indicating that CBH digestion follows a layer-by-layer solubilization manner. This reaction mode might be the major reason for slow enzymatic hydrolysis of cellulose. On the other hand, the degree of polymerization of FPC chains decreases rapidly in the initial reaction, indicating that EG digestion follows a random scission manner, which may create new ends for CBH easily. The slopes of the conformation plots for MCC and FPC increase gradually, indicating stronger chain stiffness of cellulose during hvdrolvsis

Digestion mechanism and crystal simulation of roasted low-grade high-sulfur bauxite

Low-grade high-sulfur bauxite was pretreated via suspension roasting and muffle furnace roasting to remove sulfur and enhance digestion properties.The results show that sulfur can be efficiently removed,and the alumina digestion properties are significantly improved after suspension roasting.Under optimal conditions(t=70 min,T=280°C,w(CaO)=8%and Nk=245 g/L),the digestion ratios are 94.45%and 92.08%for the suspension-roasted and muffle-roasted ore,respectively,and the apparent activation energies are 63.26 and 64.24 kJ/mol,respectively.Two crystal models were established by Materials Studio based on the XRD patterns.The DFT simulation shows that the existing Al—O bands after suspension roasting can improve alumina digestion.The(104)and(113)planes of Al2O3 after suspension roasting are found to combine with NaOH more easily than those of Al2O3 treated in a muffle furnace.

Rice Husk Ash:A New Silicon Source for Preparing SAPO-34 Catalysts Used in the Methanol-to-Olefins Reaction

SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.

Synthesis and Crystal Structure of 2-(Diphenylphosphine oxide)-3-(diphenylphosphine oxide ethynyl) spiro [bicyclo[2.2.1]hepta-2,5-diene-7,1'-cyclopropane]

The Diels-Alder reaction of bis(diphenylphosphine oxide)butadiyne (BDPPOB) with spiro[2.4]hepta-4,6-diene affords the title compound, 2-(diphenylphosphine oxide)-3-(diphen- ylphosphine oxide ethynyl)spiro[bicyclo[2.2.1] hepta-2,5-diene-7,1-cyclopropane] (DDSHC, C35H28O2P2, Mr = 542). Its crystal structure belongs to monoclinic system, space group P21/n with a =12.708(3), b = 14.666(4), c = 15.048(4) ? = 93.903(5) ? V = 2798.1(13) ?, Z = 4, Dc = 1.288g/cm3, F(000)=1136, (MoK? = 0.187mm-1, final R = 0.0626 and wR= 0.1422 for 4685 independent reflections with I > 2(I). Structural analyses reveal that the title compound is nonplanar and the dihedral angles between two phenyl rings around each phosphorus atom are 71.7(2) and 70.7(3)? respectively.

Non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends

The non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. The results show that the crystallization onset temperature(T onset) and crystallization peak temperature(T p) decrease with the increase of the content of reactive microgel, while ΔT(T onset–T p), the crystallization half-time(t1/2) and the crystallization enthalpy(ΔH c) increase. The required cooling rates of blends are higher than that of neat nylon6 in order to achieve the same relative crystallinity in a unit of time. The crystallization activation energies of the reactive microgel/nylon 6 blends are greater than those of the neat nylon 6. When the content of reactive microgel is 30%, the relative crystallinity(X t) reaches the maximum.

Research on Reactivities of Mo Cluster. A Selective Substitution Reaction of the Bridging (dtp) Ligand and Structure of Tetranuclear Molybdenum Cluster Compound [Mo_4S_4(μ-O_2CC_6H_5)_2(dtp)_4]

The cluster compound [Mo4S4 (μ-O2CC6H5)2(dtp)4] (dtp = S2P (OEt)2)was obtained by the ligand substitution reaction of tetranuclear molybdenum cluster [Mo4S4(μ-dtp)2(dtp)4] in the mixed solvent of acetone, ethanol and water in the presence of C6H5CO2Na. It is monoclinic and crystallizesin space group C2/c, Mr =1495. 09, a=12. 175 (5) , b=22. 01 (1) , c=20.875(9) ,β=99. 04(4)°; V=5570(5) ; Z=4; Dc= 1. 78g/cm3;μ(MoKα) = 14. 52 cm-1; F(000) =2984. Final R factor is 0. 066. The result reveals that the [Mo4S4] cluster core and t-(dtp)1ligands are retained and onlyμ-bridged (dtp)1- ligands are substituted by (C6H5CO2)1in the substitution reaction, thus producing the title cluster compound,the structure of which contains two species of bidentate ligand.

Phase Transitions and Dielectric Properties of Lead-Free Bi0.5K0.5TiO3-BaTiO3 Piezoelectric Ceramics

Abstract： Lead-free piezoelectric ceramics of （1 - x） Bi0.5K0.5TiO3-BaTiO3 （BKT-BT） were fabricated by the solid state reaction method with normal sintering. The influence of BT addition on the crystal structure, phase transition and dielectric properties was investigated. The crystal structure and ferroelectric phase transition were studied by XRD （X-ray diffraction） and dielectric measurements. The complete solid solution of BKT-BT was observed for all compositions. In XRD results, all compositions showed a single phase perovskite structure with tetragonal symmetry at room temperature. With increasing BT content, the separation between diffraction peaks corresponded to increasing tetragonality. The phase transition temperature of ferroelectric tetragonal-paraelectric cubic （Tc） decreased with increasing BT content. As the amount of BT concentration increased, the ceramic became denser, and almost no porosity was finally obtained.

三苯基膦与三苯基氧膦分离

研究了用化学反应-结晶联用法从w ittig反应废渣中回收三苯基膦(TPP)和三苯基氧膦(TPPO)的分离技术,探讨了各种条件对产品纯度和回收率的影响。结果表明,洗涤酸对样品中的TPP和TPPO无影响;处理量的大小对产品无影响;洗涤过的干燥样品与浓硫酸反应生成沉淀,抽滤,滤液用饱和碳酸氢钠洗至中性,旋干,用氯苯重结晶,得TPP,收率为92%,滤渣用氯苯和饱和碳酸氢钠处理,将有机层浓缩,得TPPO,收率为98%。产品经红外分析、高效液相色谱和熔点测定,与文献值一致。