CoMnMgAl Hydrotalcite-like Compounds and their Complex Oxides: Facile Synthesis and FCC SO_x Removal

The X-CoMnMgAl hydrotalcite-like precursors(X-LDHs) were first synthesized by the coprecipitation method using Cl-, CO32-, NO3- and SO42- as the corresponding guest anions, which were further used to prepare X-CoMnMgAl complex oxides(X-LDOs) through calcination. The structure and the surface morphology of the as-prepared samples were characterized by FT–IR, XRD, N2 adsorption-desorption and SEM. These as-prepared X-LDOs could act as sulfur-transfer catalysts for desulfurization. The activity of SOx adsorption and regeneration was evaluated via a self-assembled fixed-bed reactor simulating the conditions found in the fluid catalytic cracking units. These four types of sulfur-transfer catalysts with the same phase but different structure displayed the following order of desulfurization efficiency: CO3-LDO >Cl-LDO >NO3-LDO > SO4-LDO.

Studies on the Synthesis and the Structure of Ferric Aluminum Magnesium Hydrotalcite-like Compounds

The particles of ferric aluminum magnesium hydrotalcite-like compounds (Fe-Al-Mg_HTlc) were synthesized by co-precipitation method. It was found that when n(Fe)/n(Al+Mg+Fe)<0.30 and n(Al)/n(Al+Mg+Fe)<0.30, pure HTlc can be formed; when the molar ratio of Al/ (Fe+Al+Mg)>0.30, Al(OH)3 will emerge; when the molar ratio of Fe/(Fe+Al+Mg) >0.30, the amorphous composition will appear. Hence Fe3+ and Al3+ have no concentration superposition effect on the crystal structure of the samples.

The Isoelectric Point and the Points of Zero Charge of Fe-Al-Mg Hydrotalcite-like Compounds

The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc, which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations.

Ni-Co/Mg-Al catalyst derived from hydrotalcite-like compound prepared by plasma for dry reforming of methane

Ni-Co bimetallic catalysts with different Ni/Co content were derived from cold plasma jet decomposition and reduction of hydrotalcite-like compounds containing Ni,Co,Mg and Al,and their catalytic performance was investigated with dry reforming of methane.Experimental results showed that the hydrotalcite-like precursors could be completely decomposed and partly reduced by cold plasma jet,and the Nicontained catalysts exhibited much higher activity than the catalyst without Ni.Especially,the catalyst with Ni/Co ratio of 8/2 achieved not only the highest conversions of 80.3%and 69.3%for CH4 and CO2,respectively,but also the best stability in 100 h testing.The catalysts were characterized by XRD,XPS,TEM and N2 adsorption techniques,and the results showed that the better performance of the 8Ni2Co bimetallic catalyst was attributed to its higher metal dispersion,smaller metal particle size,as well as the interaction effect between Ni and Co,which were brought by the special catalyst preparation method.

First-principles investigation of the phase stability of MgAl_2 compounds

First-principles have been calculated to investigate the phase stabilities of the intermetallic phase of MgAl2 compounds by electronic structures and the charge distribution maps. The first-prin- ciples employed the norm-conserving pseudo potential density functional method. They were calcu- lated both with the Ceperley and Alder data as parameterized by Perdew and Zunger（CA-PZ） of local-density approximation （LDA） and with the Perdew Burke Eruzerh （PBE） form of gradient-corrected approximation （GGA）. A better method was found by comparing results from these two ultrasoft pseudo potentials. The present calculations indicate that LDA is better than GGA compared with references. This work also compared the lattice parameters, cohesive energy, formation enthalpy and electronic structure between theoretical results and experimental measurements （where available ）. The calculations indicate that the unit cell volume get smaller after optimized and cohesive energy and formation enthalpy of C14 structure is the highest. The calculated structures are stable and the stability is aligned as C36 〈 C15 〈 C14.

N2O Decomposition over K-Ce Promoted Co-M-AI Mixed Oxide Catalysts Prepared from Hydrotalcite-like Precursors

A series of mixed oxide catalysts with different composition of Co-M-Al and Co-M-Ce- Al （M=Zn, Ni, Cu） were prepared by co-precipitation method from hydrotalcite-like compounds. The experimental results revealed the catalytic activity of Co-Ni-Al is slightly higher than that of Co-Zn-Al and much higher than that of Co-Cu-Al for direct decomposition of N2O. Moreover, addition of small amounts of Ce02 improved the catalytic activity signif- icantly and made the decomposition temperatures at which the N2O conversion was 50% and 90% （T50 and Tgo） both decreased 80 ℃ than those of Co-M-Al catalysts without CeO2 added. Further, potassium-load also promoted the catalytic activity, and the decomposi- tion temperatures of T50 and T90 both decreased approximately 50 ℃. It is significant for decomposing N2O from industries and reducing carbon emission from atmosphere.

Removal of Cu（Ⅱ） from CuSO4 Aqueous Solution by Mg-Al Hydrotalcite-like Compounds

Hydrotalcite-like compound （HTlc） with a Mg/AI molar ratio of 2 ： 1 was synthesized by using a coprecipitation method and the sorption removal of Cu（Ⅱ） by the Mg-AI HTlc sample from CuSO4 solution was investigated. It was found that the Mg-AI HTlc showed a good sorption ability for Cu（Ⅱ） from CuSO4 solution, indicating that the use of hydrotalcite-like compounds as promising inorganic sorbents for the removal of heavy metal ions from water is possible. The sorption kinetics and the sorption isotherm of Cu（Ⅱ） on the HTlc obeyed the pseudo-second order kinetic model and Langmuir equation, respectively. The percent removal of Cu（Ⅱ） by the HT1c was strongly dependent on the initial pH of bulk solution. It increased sharply with the increase of initial pH value in the range of 5-7, and was relatively small in the initial pH range of 4-5, while it reached about 100% after initial pH was higher than 7. The presence of AlCl3 might obviously lower the equilibrium sorption amount （qc） of Cu（Ⅱ） on the HTlc. However, the presences of NaCI and MgCl2 might increase the qe. The presences of ligands （citric acid and EDTA） in the studied concentration range might obviously decrease the qe of Cu（Ⅱ） on the HT1c. The removal mechanism of Cu（Ⅱ） cations by HTlc in the presence of SO4^2- anions may be attributed to the surface-induced precipitation of Cu（Ⅱ） hydroxides and the surface complex adsorption by the linking effect of SO4^2- between the HTlc and Cu（Ⅱ） cations, and the removal ability arising from the surface-induced precipitation is much higher than that from the linking effect of SO4^2-.

纳微尺度层状MgAl固体碱催化解聚木质素磺酸钙制取含氧化合物的研究

在水热合成体系中引入羟基化合物制备纳微尺度层状镁铝水滑石前驱体(MgAl-LDHs),通过正交实验优化合成工艺参数,焙烧后得到固体碱氧化物(MgAlOx);采用X射线衍射(XRD)、扫描电子显微镜(SEM)和二氧化碳程序升温脱附(CO2-TPD)对水滑石前驱体及固体碱氧化物进行晶相、形貌和碱度表征,对MgAlOx解聚木质素磺酸钙(CLS)的催化性能进行评价,采用气相色谱(GC)、气相色谱-质谱联用(GCMS)和凝胶渗透色谱(GPC)对反应后气、液和固三相产物组成规律进行分析.结果表明,在n(Mg)/n(Al)=3,pH=12,180℃,24 h条件下,添加15%(体积分数)C2H5OH时,可以制备晶粒尺寸140~230 nm的层状MgAl-LDHs,在空气气氛下于600℃焙烧6 h得到MgAlOx.水热体系下固体碱氧化物对木质素磺酸钙解聚的优化条件为270℃,4 h,65%C2H5OH,m(MgAlOx)/m(CLS)=1/2,此时其气、液和固三相产物的产率分别为4.50%,58.30%和37.20%,其中液相产物收率比纯木质素磺酸钙解聚提高了13.30%,液相产物主要组成为酚类、芳香类、酯类和其它化合物,含氧化合物总选择性为79.05%(酚类66.06%,酯类12.99%),反应后的MgAlOx经焙烧氧化再生后,循环使用4次仍具有较高的活性和稳定性.

Green Cycle: Sulfate Sorption from Natural Water on Anionic Clay Compound Obtained from Industry Wastewater

In this paper we are describing a green cycle process. The first step was a novel hydrotalcite-like compound (HTLC) synthesized by a co-precipitating method, under standard ambient temperature and pressure, using chemical industry wastewater rich in divalent and trivalent cations, activated by a thermal treatment and finally characterized by scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDS) and thermogravimetric analysis (TGA). The second step was a series of batch sorption tests performed with this activated HTLC and untreated underground sulfurous water from the state of Puebla, México. The HTLC calcined at 500°C/3 h exhibited the best sorption ability for ions, demonstrated a decrease of the hardness and sulfate ions to below the regional legal standards for drinking water. Once inactive after being used in water treatment, the sorbed ions were removed by ion exchange in a carbonate-containing solution, resulting in an 80% recycling of the material which upon activation demonstrated a retained capacity for water treatment. This recyclability suggests the exciting possibility of this novel compound as an efficient “green” technology in water treatment processes.

Preparation and characterization of a novel strong-fluorescent hydrotalcite-like compound (Al-HTLc)

A novel strong-fluorescent hydrotalcite-like compound (Al-HTLc) was synthesized by coprecipitation. In the sample, the content of aluminum(III) in the layers was decreased to a proper value. The Al3+ ions coordinated with 8-hydroxyquinolines (8-HQ) which were dispersed into the anions in the interlayer region. The sample was characterized by XRD, XPS, FT-IR, TG-DSC, UV-Vis, and fluorescence spec- troscopy; its composition and structure were also determined. The results indicate that the sample can emit fluorescence (487 nm) with a strong fluorescence intensity (4.9×105 (a.u.)). The fluorescent lifetime and fluorescence quantum yield of Al-HTLc were measured to be 21.24 ns and 67%, respectively, higher than those of pure 8-hydroxyquinoline aluminum (Alq3). The result of TG-DSC measurement clearly shows the enhanced thermal stability of Al-HTLc compared with that of MgAl-LDH and pure Alq3. Al-HTLc may be used as a novel luminescent functional material.

Synthesis and characterization of a strong-fluorescent Eu-containing hydrotalcite-like compound

A novel strong-fluorescent Eu-containing hydrotalcite-like compound (Eu-HTlc) was synthesized using the coprecipitation method,in which aluminum(III) was partially substituted by Europium (III) in the hydrotalcite-like layers,and thenoyltrifluoroacetone,1,10-phenanthroline were dispersed into the anions in the interlayer region.The sample was characterized by XRD,XPS,FT-IR,ICP,TG-DSC,TEM and fluorescence spectra,and its composition and structure were determined.The results indicated that the sample exhibited a characteristic red light (614 nm).The fluorescent lifetime and fluorescence quantum yield of Eu-HTlc were measured to be respectively 893 -s and 66.44%,higher than those of Eu(III)-thenoyltrifluoroacetone1,10-phenanthroline complex [Eu(TTA)3phen].The result of TG-DSC measurement showed the enhanced thermal stability of Eu-HTlc compared with that of MgAl-LDHs and Eu(TTA)3phen.With excellent photoluminescent property and thermal stability,low contents of rare earth ions and ligands,the Eu-HTlc may become one of the novel fluorescent materials with potential applications.

Thixotropy of Aqueous Suspensions Containing Mg-AI Hydrotalcite-like Compound and Low-substituted Cationic Starch： Comparison between Oscillatory Shear and Thixotropic Loop Measurements

The rheological properties of aqueous suspensions consisting of positively charged aluminum magnesium hydrotalcite-like compound （HTlc） and low-substituted cationic starch （LCS） were investigated. Special emphasis was placed on the thixotropic phenomenon. Thixotropic behavior was investigated by two thixotropic methods： thixotropic loop and oscillatory shear measurements. LCS molecules could be adsorbed onto HTlc particles due to the hydrogen bonding between ether groups or hydroxyl groups of LCS and hydroxyl groups of HTlc. The elastic dynamic response of the HTlc/LCS suspension increased with increasing mass ratio （R） of HTlc and a three-dimensional network structure could be formed in the suspension with higher R value. The thixotropic type of the HTlc/LCS suspension transformed from negative to positive and then to complex thixotropy when R changed from 0 to 0.5. By comparing between the thixotropic results obtained by thixotropic loop and oscillatory shear measurements, it was validated that the thixotropic loop for the suspension showing complex thixotropy had a crossover point.

Novel Co-Mg-Al-Ti-O catalyst derived from hydrotalcite-like compound for NO storage/decomposition

Catalysts of Co1.5Mg1.5/Al0.9Ti0.1O and Co1.5Mg1.5/AlO were successfully prepared by calcinations of corresponding hydrotalcite-like compounds at 800°C for 4 hr. The derived oxides were of spinel phase and a small quantity of Ti substitution did not change the crystal purity. Their catalytic performance for the NO storage/decomposition was investigated. Ti incorporation enhanced the NO decomposition activity while has an opposite effect on the storage capacity of catalyst. In situ FT-IR spectra of the catalysts showed that the final adsorption species on the catalysts was coordinated nitrates/nitrites. In addition, NO storage/decomposition mechanism has been discussed on the basis of these observations.

钴铝\镁铝水滑石的热稳定性能及其氧化物的结构研究

采用溶液共沉淀法合成了CoAl-HT和MgAl-HT水滑石,在800℃下煅烧4h得到了钴铝和镁铝尖晶石氧化物粉体。利用XRD、FT-IR和TG对水滑石及其氧化物粉体的结构和热稳定性能进行了表征分析。从XRD和FT-IR分析结果可知,所得产品为层板水滑石物质,且结晶性良好,从CoAl-HT和MgAl-HT结果对比可知,镁铝组合更容易形成水滑石结构;由氧化物粉体的XRD分析结果可知,在800℃下两者都形成了尖晶石结构,且钴铝氧化粉体尖晶石无杂相,结晶性更好;TG曲线呈现了两个样品的水滑石热学性能,通过对比可知,MgAl-HT在216和372℃下分解而CoAl-HT在197和243℃下分解说明MgAl-HT比CoAl-HT具有更好的热稳定性能。

Synthesis of HTLcs modified by K_(3)PO_(4) for side chain alkylation of toluene with methanol

A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for synthesis of ethylbenzene and styrene.The catalysts were characterized by X-ray diffraction(XRD),N_(2)physical adsorption-desorption,Fourier-transform infrared spectroscopy(FT-IR),Scanning electron microscopy(SEM),X-ray photoelectron spectrometry(XPS),NH_(3)temperature-programmed desorption(NH_(3)-TPD)and CO_(2)temperature-programmed desorption(CO_(2)-TPD).It was found that the selectivity of styrene was highest(39.25%)when the K_(3)PO_(4)loading was 7.5 wt%.And the total yield of styrene and ethylbenzene could reach 65.08%with 10 wt%K_(3)PO_(4)loading.This might due to the fact that the addition of K_(3)PO_(4)could adjust the acid and basic sites of catalysts.In addition,appropriate strength and amount of basic sites were favorable to producing more styrene.

Effect of Ce-doping on catalysts derived from hydrotalcite-like precursors for COS hydrolysis

In order to investigate the effect of Ce-doping on the catalysts derived from hydrotalcite-like precursors for carbonyl sulfide(COS) hydrolysis,a series of Zn-Ni-Al-Ce hydrotalcite-like compounds were prepared by co-precipitation method and the catalytic activity of their derived composite oxides were studied at 50 oC.The effect on the structural properties caused by Ce doping was studied by the X-ray diffractometer(XRD),scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS).The catalytic activities results showed that addition of Ce enhanced the catalytic activities significantly,but excessive Ce-doping had a negative effect on COS hydrolysis.XRD,SEM and EDS results illustrated that,compared with the Ce-free sample,the particle size of oxide solids decreased and the degree of dispersion increased due to Ce doping.

Improved methanol synthesis performance of Cu/ZnO/Al_(2)O_(3)catalyst by controlling its precursor structure

Methanol,a versatile chemical,fuel additive and potential H_(2) carrier,has attracted great attention.Despite of the wide industrialization,improvement of Cu-based methanol-synthesis catalysts is highly anticipated.Accordingly,a series of Cu/ZnO/Al_(2)O_(3) with designed precursor structures were prepared,and its structure-function relationship was investigated to make progress on this area.Results showed the catalyst derived from highly zinc-substituted malachite demonstrated the best catalytic performance in this work.It was found that the well-behaved catalyst possessed relatively high Cu specific surface area and exposed Cu concentration,and the well Cu/ZnO synergy.CuZn alloy was found by In-situ XRD tests,and its effect on the catalyst's thermostability was discussed.Fractional precipitation,which facilitated the Cu^(2+) substitution by Zn^(2+) in malachite lattice,could be an efficient preparation method of the Cu/ZnO/Al_(2)O_(3) catalyst.

Urea Decomposition Method to Synthesize Hydrotalcites

The urea decomposition property at high temperature has been used to control the pH value in the synthesis of layer compounds. The hydrotalcites of Mg-Al and Ni-Al with high crystallinity were synthesized by using this property.

Influence of Mg/Al Molar Ratio on the Structures and Properties of Ru-Mg Alx Catalysts for Isomerization Linoleic Acid

With the knowledge on the significant effect of basic site and Ru on the catalytic performance of heterogeneous catalysts in the isomerization of linoleic acid to conjugated linoleic acid,a series of Ru-Mg Alx compounds with different basicity have been prepared by controlling the Mg/Al molar ratio. The results showed the catalysts with different basicity markedly influence the structure,the Ru dispersion,properties and catalytic performances for the isomerization reaction. The strong basic site is conductive to the high yield of CLA products. The strong basic site and the well-dispersion RuO2synergetic catalysis for the isomerization reaction,basic site and the well-dispersion RuO2synergetic effect are possibly via a Mg-O-Ru linkage.

Catalytic reduction of NO_x by CO on hydro-talcites-derived mixed oxides Co AIM and MgAlM (M = Cr, Mn, Fe, Co, Ni, Cu)

Two series of mixed oxides, CoAlM and MgAlM (M= Cr, Mn, Fe, Co, Ni, Cu) , were prepared by calcining their corresponding hydrotalcite-like compounds (HTLc) . The ratio of Mg: Al: M (or Co: Al: M) was 3:1:1. The catalytic activity of all samples for the reaction of NO + CO was investigated. The results showed that the activity of CoAlM was much higher than that of MgAlM. The structure and the property of redox were characterized by XRD and H2-TPR. The results indicated that only MgO phase was observed after calcining MgAlM hydrotalcites, and the transition metals became more stable. The spinel-like phase appeared in all of CoAlM samples after the calcination, and the transition metals were changed to be more active, and easily reduced . The activities of three series of mixed oxides CoAlCu obtained from different preparation methods, different ratio of Co:Al:Cu and at different calcination temperatures, were studied in detail for proposing the mechanism of reaction. The ability of adsorption of NO and CO were investigated respectively for supporting the mecha-