插层三元锌镁铝水滑石的制备及其在PVC中应用

采用共沉淀-离心-水热法制备出形貌规整且高结晶度的锌镁铝水滑石(ZnMgAl-CO_3LDHs),以此为前驱体通过离子交换反应制备出磷酸二氢根插层锌镁铝水滑石(ZnMgAl-P LDHs),利用XRD、FT-IR、SEM、TG/DTG分析表明磷酸二氢根成功插入到锌镁铝水滑石层间,层间距从0.763 5 nm增加到1.226 0 nm。将磷酸二氢根插层锌镁铝水滑石与聚氯乙烯(PVC)复配,研究其对聚氯乙烯的热稳定性、力学性能及流变性能的影响,研究发现磷酸二氢根插层锌镁铝水滑石能够明显提高PVC的初期抑制变色性能,但是长期热稳定性略有降低;磷酸二氢根插层改性锌镁铝水滑石后提高了在聚氯乙烯基材中的分散性并改善了与聚氯乙烯之间的相容性,聚氯乙烯力学性能提高,但是加工流变性能稍有降低。     

镁铝水滑石的制备与性能研究

采用盐碱共沉淀法制备镁铝水滑石,采用XRD、FT-IR和粒度分析等手段对合成样品进行分析和表征,利用静态热老化法和静态热稳定性实验研究了镁铝水滑石稳定剂在聚氯乙烯（PVC）中的热老化性能和热稳定性 能。实验结果表明：镁铝水滑石是良好的PVC热稳定剂和热老化剂,热稳定剂实验的最佳配方比为m（PVC）∶m（硬脂酸）∶m（镁铝水滑石）= 100∶2∶1.2;热老化实验的最佳配方为m（PVC）∶m［邻苯二甲酸二辛酯（DOP）］∶m（硬脂酸）∶ m（镁铝水滑石）=100∶70∶2∶2。     

反应时间对镁铝水滑石制备及其性能的影响

采用X射线衍射（XRD）和红外光谱（IR）测定液相沉淀工艺制备镁铝水滑石试样的相组成及其结晶状况,利用差热（DTA）-热重（TG）分析测定试样的热性能。研究发现：反应时间对水滑石晶体晶相组成及热分解性能的影响。     

尿素法制备锌镁铝多元水滑石及结构分析

采用尿素法合成了锌镁铝三元水滑石,并通过X射线衍射(XRD)、扫描电镜(SEM)对合成的水滑石进行表征,研究晶化时间、尿素浓度对合成的水滑石结构以及尺寸等的影响。XRD表征结果表明,合成产物均具有水滑石的特征峰。晶化时间过长,水滑石(00l)晶面生长速率降低、结晶度下降、纳米片层分散性变好但片层表面规整度下降;增大尿素浓度,水滑石(00l)和(110)晶面生长速率均下降、结晶度提高、片层分散性变好且表面规整度变高。     

锌镁铝水滑石的制备条件对PVC热稳定性的影响

以硝酸锌、硝酸镁、硝酸铝、氢氧化钠和碳酸氢钠为原料,采用水热合成法制备了锌镁铝水滑石,并对合成产物进行XRD表征。将所制得的镁铝锌水滑石用于PVC热稳定剂中,采用平板硫化法评价其对PVC的热稳定性能,考察锌铝摩尔比、碱量等水滑石制备条件对PVC热稳定性能的影响。结果表明:当n(M~(2+))/n(M~(3+))=2,n(Zn~(2+))/n(Mg~(2+))=1,n(NaHCO_3)/n(Al~(3+))=1.1,n(NaOH)/(2nM~(2+)+3nM~(3+))=0.9,反应温度为90℃,反应时间为24 h时,合成的锌镁铝水滑石对PVC具有较好的初期着色性能、长期热稳定性能。     

不同铝源和制备方法对镁铝水滑石合成的影响

分别以NaAlO2和Al（NO3）3·6H2O为铝源,采用水热法和双滴定法制备了镁铝水滑石。考察了不同铝源、不同制备方法对镬铝水滑石晶形结构以及热稳定性能的影响,并用X射线衍射（XRD）、红外光谱（IR）和粒度分析等手段对合成样品进行分析和表征。结果表明：以NaAlO2和Al（NO3）3·6H2O为铝源均能合成出具有典型水滑石结构的样品,前者具有更好的热稳定性能。此外,水热条件下合成的镁铝水滑石其结构较双滴定法合成的类水滑石更加完整,而后者则表现出更好的热稳定性能。改性后的类水滑石的晶体结构未被破坏,其XRD衍射峰的位置、相对峰高都基本上没有改变。     

插层改性锰镁铝水滑石对EVA阻燃及力学性能的影响

乙烯-醋酸乙烯共聚物（EVA）易燃烧,且燃烧产物含有一氧化碳。采用微波晶化法分别用碳酸根、硬脂酸、硼酸根、十二烷基硫酸根及其混合阴离子合成插层组装的锰镁铝水滑石,FT-IR和XRD结果显示插层组装的样品进行了成功制备。将改性的水滑石分别按5%和20%比例与EVA混合制备成复合材料,并对其进行阻燃性能和力学性能的测定。测试结果表明：插层组装的锰镁铝水滑石有助于提高EVA的阻燃性能,且插层阴离子对EVA的断裂拉伸率及拉伸强度均有不同程度的影响。     

片层状镁铝复合阻燃剂的制备工艺研究

通过共沉淀法合成了片层状镁铝复合阻燃剂,采用正交试验研究了反应温度、反应时间、镁离子起始浓度对层间距及生长机制的影响。结果表明,反应温度为85 ℃,反应时间为1 h,镁离子起始浓度为1.5 mol/L时,得到层间距d（003）达到0.797 89 nm的层状镁铝复合阻燃剂。同时采用透射电镜（TEM）、热重-差热分析（TG-DTA）对最优化产品进行表征。结果显示,产品为片状卷曲结构,分散性好,热分解温度高。     

纳米镁铝水滑石热分解机理及其动力学

以尿素为沉淀剂制备纳米镁铝水滑石(LDH),结合X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)和热重-差热分析(TG-DTA)表征方法,研究了纳米LDH的热分解过程及其动力学。结果表明,纳米LDH热分解存在两个阶段:当热分解温度在410～527 K时,纳米LDH失去表面吸附水和层间结合水,其热分解动力学方程为随机核化Aurami方程Ⅰ;当温度在604～768 K时,纳米LDH Brucite层脱去羟基,CO_3~(2-)以CO_2形式逸出,其热分解动力学方程为三维扩散球形对称Jander方程。     

原位还原镍镁铝水滑石的活化机制与制氢性能(英文)

采用共沉淀法合成了镍镁铝水滑石(NiMgAl-layered double hydroxides,NiMgAl-LDHs),将其分别在500,550,600℃焙烧,得到镍镁铝复合氧化物。用X射线粉末衍射和氢气程序升温还原技术对层状水滑石前躯体和衍生复合氧化物的结构与还原特性进行表征,并通过质谱对NiMgAl-LDHs原位还原过程进行了分析。结果表明NiMgAl-LDHs原位还原过程包括3个步骤:首先,水滑石层间水分子脱除;其次,层板中的Ni2+被直接还原为Ni0,同时水滑石发生羟基脱水和碳酸根脱除得到NiMgAl(O);最后,NiMgAl(O)中Ni在高温下被还原。NiMgAl-LDHs通过原位氢气还原活化得到的镍基金属负载型催化剂,相比传统方法(先焙烧后还原)具有更高的制氢催化活性。     

The impact of the “memory effect” on the catalytic activity of Mg/Al; Mg,Zn/Al; Mg/Al,Ga hydrotalcite-like compounds used as catalysts for cycloxene epoxidation

The epoxidation of cyclohexene by hydrogene peroxide and benzonitrile, in methanol as solvent on solid base catalysts, hydrotalcites (HT) and corresponding mixed oxides (C-HT) was investigated. The employed catalysts were as-synthesized Mg/Al; Mg,Zn/Al; Mg/Ga,Al hydrotalcites, their derived mixed oxides and the corresponding reconstructed hydrotalcite forms (R-HT) obtained via the “memory effect” upon a rehydration treatment of C-HT. The catalysts were characterized by XRD, CO₂-TPD and N₂ adsorption–desorption measurements.

The reconstructed HT samples exhibit higher activity in comparison to the as-synthesized carbonated HT samples. A tentative correlation of the catalytic properties with the base strength of the active sites, the structural and textural characteristics of the catalysts, has been explored.     

马来酸酐酰化β-环糊精柱撑Zn/Al-CO_3型水滑石的制备及表征

通过酯化反应合成马来酸酐酰化β-环糊精(β-CD),采用成核/晶化隔离法制备了Zn/Al水滑石(LDHs),并以水滑石为前驱体,用返混法进行插层组装合成马来酸酐酰化β-CD柱撑Zn/Al水滑石,利用XRD、FTIR对其结构进行表征。结果表明,利用返混法进行插层组装,可以成功的将马来酸酐酰化β-CD阴离子插入Zn/Al水滑石层间,其层间距由原来的0.76 nm增大为3.43 nm。     

超声辐射下n(Mg)∶n(Al)水滑石催化合成

通过低饱和共轭沉淀法制备了不同n(Mg)∶n(Al)的水滑石，并用XRD和BET等技术对催化剂前驱体进行了表征。XRD表征表明，水的加入使得水滑石的结构能够得到部分重建。同时水的加入使水滑石表面的O^2- 生成了相应的B碱(OH^-)，大大提高了催化活性。BET表征结果表明，水滑石作为碱性催化剂的活性位点主要存在于暴露的板层边缘。以制备的水滑石为催化剂在超声辐射下合成了含有强吸电子取代基4,4′-二硝基查尔酮，并考察了超声、催化剂的组成、水合质量和溶剂对催化性能的影响。结果表明，当催化剂的n(Mg)∶n(Al)＝3.0、水合质量为其前驱体的35％和溶剂为甲醇时，在超声辐射下具有最高的催化活性，收率达91.3%，选择性为100%。     

Mg/Al复合氧化物催化丙酮和碳酸二甲酯合成乙酰乙酸甲酯

利用先共沉淀后水热处理的方法制备出水滑石前体,将其焙烧后,得到具有不同Mg/Al摩尔比的复合氧化物,并借助电感耦合等离子原子发射光谱、XRD、CO2-TPD和氮气吸脱附等手段对其进行表征。结果表明,Mg/Al摩尔比对催化剂的结构和碱性质有较大的影响,并且在催化丙酮和碳酸二甲酯合成乙酰乙酸甲酯的反应中,其比单纯的氧化镁和氧化铝表现出了更高的催化活性。进一步的研究表明,在该反应中是复合氧化物的中强碱性位起催化活性的作用,当Mg/Al摩尔比为2时,催化剂具有最高的活性。此外,重复性实验表明,这些催化剂具有较好的稳定性和重复使用性。     

Zr4+掺杂对Mg/Al水滑石磷吸附行为的影响

采用共沉淀法制备了系列不同Zr4+含量的Mg/Al/Zr三元类水滑石材料，研究了其对废水中磷酸根离子的吸附性能。采用XRD、DRIFTS、氮气吸脱附实验等手段对材料的结构及织构性质进行了表征，并研究了溶液初始pH以及竞争阴离子对磷吸附量的影响。结果表明：掺杂Zr4+能提高类水滑石层板正电荷密度以及增大层间距，有利于磷酸根阴离子的吸附；Mg/Al/Zr类水滑石对磷的吸附过程符合准二级动力学模型，吸附等温线符合Langmuir模型，当n(Zr4+)/(Al3++Zr4+)为0.3时，理论饱和吸附量最大，达到76.6 mg/g，比Mg/Al水滑石高出28.7%；酸性环境有利于磷酸根的吸附，而二价阴离子的竞争吸附作用会显著降低磷吸附效果。Mg/Al/Zr类水滑石对磷的吸附机理为静电吸引和阴离子交换协同作用。     

Cation composition during recrystallization of layered double hydroxides from mixed (Mg, Al) oxides

Changes in cation composition and M²⁺/M³⁺ ratio during hydrotalcite regeneration were studied. Regenerated hydrotalcites were obtained by recrystallization of mixed (Mg, Al) oxides in solutions of divalent (Mg, Zn, Co, Ni, Cu) or trivalent (Al, Fe) cations.Heating Mg–Al–CO₃ hydrotalcites with Mg/Al=2, 3 and 3.7, at 600 °C for 2 h yielded periclase-like mixed (Mg, Al) oxides (HT-P). The hydrotalcite structure was restored by dispersing oxides 48 h in water or aqueous solutions of different cations.The presence of Mg²⁺, Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ salts or of low soluble hydromagnesite increased the M²⁺/Al ratio, reaching a maximum value of 3.8. An incorporation of Zn²⁺, Ni²⁺, Co²⁺ and Cu²⁺ cations in the newly formed hydrotalcite was detected, while Mg²⁺ remained in solution. In the presence of soluble Al salts or freshly precipitated Al(OH)₃, the M²⁺/Al ratio approximated the minimal possible value of 2.The Mg/Al ratio of a hydrotalcite crystallized from a mixture of two HT-P samples with different Mg/Al ratios is equal to the weighted average value.The results obtained support the conception of the dissolution–crystallization mechanism of hydrotalcite regeneration from mixed (Mg, Al) oxides contrary to the widely accepted concept of topotactic processes.     

复原镁铝水滑石固体碱在Aldol反应中的应用

以镁铝水滑石为前体焙烧制得镁铝复合氧化物,在含水体系中水合催化取代苯甲醛和丙酮的aldol反应。结果显示,水滑石前体经过复原处理后活性高于普通Mg/Al水滑石;Mg/Al比为4∶1,NaOH/Na2CO3为沉淀剂,镁铝的硝酸盐作为金属盐来源制备的催化剂对对硝基苯甲醛和丙酮之间的aldol反应具有最好的催化效果。     

碳酸根型镁铝复合氢氧化物的合成和表征及其催化性能

以恒定pH值共沉淀法合成碳酸根型镁铝水滑石,用XRD、IR、TG-DTA和SEM等手段进行表征。XRD衍射表明，Mg与Al物质的量比为1∶1、3∶1、4∶1和6∶1的合成物均有水滑石结构。热重-差热分析(TG-DTA)显示，水滑石有两个吸热峰值:第一吸收峰值在200～250 ℃, 第二吸热峰值在400～450 ℃,最大损失重量在2780%～33.41%。SEM分析可知，样品呈层状、棒状、针状和蜂窝状等结构。并对镁铝复合氢氧化物作为催化剂用于生物柴油制备作了研究。结果表明，Mg与Al物质的量比为3∶1的水滑石可使甲酯收率达到90%左右，且可重复使用。产品达到德国生物柴油质量标准。     

Reusable high performance of calcined Mg/Al hydrotalcite for the removal of Navy Blue and Yellow F3G dyes

Water pollution with dye chemicals from apparel industries is a serious problem in the world.Since most of dyes are potentially have toxic and carcinogenic effects on human,it is important to remove them before they are discharged to the environment.Among many methods available for dyes removal in water,adsorption is the easiest and economically feasible that has no major obstacle for practical appli-cations.In the present study,we tested calcined Mg/Al hydrotalcite (Mg/Al CHT) prepared by co-precipitation technique as an adsorbent for the removal of Navy Blue (NB) and Yellow F3G (YF3G) dyes.Mg/Al CHT was characterized by using a Fourier transform infrared (FTIR) spectrometer,an X-ray diffrac-tometer (XRD) and a scanning electron microscope (SEM).The results showed that Mg/Al CHT was highly effective as an adsorbent for the removal of NB and YF3G under mild-acidic condition (pH 4) with removal capacities (b) according to Langmuir isotherm model were 7.97 × 10-4 and 5.80 × 10-4 mol·g-1,respectively.Kinetics study showed that the adsorption of NB and YF3D on Mg/Al CHT followed pseudo-second order with rate constant (kp2) 11.57 × 103 and 11.75 × 103 g·mol-1·min-1,respectively.The spent adsorbent can be easily regenerated by simply calcining it at 450 ℃ for 3 h.Adsorption test on the mix-ture of NB and YF3G showed that the adsorption capacity of Mg/Al CHT was eightfold higher than that of Mg/Al HT and the value was maintained with repeated use.     

Synthesis of cyclohexanone-formaldehyde resin catalyzed by rehydrated Mg–Al hydrotalcite

Cyclohexanone-formaldehyde resin (CFR) was synthesized over rehydrated Mg–Al hydrotalcite (HT). Therein, Mg–Al HT was rehydrated from Mg–Al HT of good crystallinity using a liquid method. Rehydrated Mg–Al HT (HT-r) shows certain catalytic activity for aldol condensation and catalytic activity is dramatically improved in the presence of hexadecyl trimethyl ammonium bromide (CTAB) because CTAB as a phase transfer catalyst is helpful to enhance the mass transfer among three phases. Both higher temperature and longer reaction time are preferable to increase the molecular weight of CFR. Though the catalytic activity of HT-r decreases as the reutilization cycle increases, the deactivated HT-r can be easily regenerated upon calcining and rehydrating.