Preparation and characterization of alumina-zirconia composite material with different acid ratios by the sol-gel method

Alumina-zirconia composite materials were produced with different acid ratios by the sol-gel method using aluminum isopropoxide and zirconium chloride. The composites were produced by changing acid/alkoxside ratio in alumina. The composite materials were calcinated at 600°C, 900°C and 1300°C. The effects of acid concentration and calcination temperature on the surface area and pore radius were determined from the nitrogen adsorption isotherm at 77 K. The density of the composites was also measured. The minimum density of produced material was recorded as 1.35 g cm⁻³ at an acid/alkoxside ratio of 0.2. The highest specific surface area and pore diameter of the lightest material are 191.86 m² g⁻¹ and 18.4 Ǻ, respectively. Although pore diameter and specific surface area are not changed at any of the experimental temperatures which were tested by decreasing acid/alkoxside ratio, the density is slightly increased. However, it was observed that the calcination temperature significantly affects the surface area and density of the material.      

多级孔结构WO3/ZrO2固体酸催化剂的烷基化催化性能研究

采用复合模板表面活性剂辅助水热法一步合成WO3/ZrO2体系多级孔固体酸催化剂,探讨了煅烧温度对所合成催化剂试样酸强度及酸量的影响,并考察了催化剂针对苯和十二烯的烷基化反应中的催化性能.结果表明,WO3/ZrO2体系催化剂具有较强的酸强度,并且与催化剂的比表面积和晶化程度有密切关系,比表面积的增大和四方相ZrO2的生成能有效地提高催化剂的酸强度.该催化剂具有优良的烷基化反应催化活性和选择性,其中450℃,5h煅烧的WO3/ZrO2催化剂样品酸性最强,其烷基化催化活性和选择性最优.     

The colloidal stability of raw bentonite deformed mechanically by ultrasound

The present study examined the effect of sonication time on the particle–size and the colloidal stability (i.e. point of zero charge, PZC and zeta potential, ζ) of raw bentonite (RB) from Saudi Arabia. In this study, bentonite suspensions were sonicated for various time intervals (30, 60 and 120 min). The effect of sonication time on specific surface area and the colloidal stability behavior of bentonite at various pH and in presence of different NaCl concentration were investigated. The increased in lightness and brightness of bentonite suspension was observed during sonication experiment which could be attributed to the reduction in the particles size.With increasing sonication time the specific surface area increased and consequently the zeta potential of bentonite suspension increased. Also a shifting in the PZC from pH 3 for raw bentonite to pH 2 after 120 min of sonication.The zeta potential of sonicated bentonite suspension in presence of different concentration of NaCl shows unusual trend compared to the unsonicated bentonite. In conclusion, the stability of raw bentonite suspension was significantly modified due the application of ultrasound with rending the particle-size of the bentonite.     

A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid

Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids.     

Modification of a phase-inhomogeneous alumina support of a palladium catalyst. Part I: effect of the amorphous phase on the textural and acidic characteristics of alumina and methods for controlling its phase homogeneity

The contribution of the amorphous phase in aluminum hydroxide and alumina to their properties was investigated in this work. It was shown that the amorphous phase in aluminum hydroxide is stabilized by alumoxanes, and it is a source of a finely porous component and capable of increasing the surface area by ~78%. In γ-Al₂O₃, amorphous alumina raises the surface area and the acidity. It was established that the method of chemical modification does not change the phase inhomogeneity but allows adjusting the acid properties while maintaining the high specific surface area. It was shown that the amorphous phase is more reactive when processing phase-inhomogeneous aluminum hydroxide with acetic acid. Crystallization of amorphous alumina as a result of high-temperature treatment of phase-inhomogeneous aluminum hydroxide is accompanied by significant decrease in specific surface area and acidity.     

Modeling a solid-phase electrochemical reaction of lithium intercalation in aluminum during a noninstantaneous nucleation of Β-LiAl

The interfacial surface area and the electrode surface coverage by a product during the nucleation and growth of a new phase are modeled numerically and calculated analytically for electrochemical intercalation of lithium in aluminum in the course of which intermetallic compound Β-LiAl forms. As opposed to the theoretical calculation, the model accounts for mutual influence of the new-phase nuclei on their distribution over the cathode surface under conditions of noninstantaneous nucleation. The ordering of such a distribution varies extremally (passes through a maximum) with increasing size of zones where the nucleation probability is low and which surround the nuclei. This makes the dependence of a maximum specific interfacial area on the zone radius extremal as well. The model may be applied for analyzing potentiostatic current transients during cathodic intercalation of lithium in aluminum from a LiClO₄ solution in propylene carbonate.     

氟化铵对HZSM—5分子筛改性的研究

利用XRD,IR,MAS-NMR,TEM,XPS和SIMs等方法研究了经不同浓度NH_4F浸渍后的HZSM-5分子筛结构和表面性质的变化,并用NH_3-TPD和吡啶吸附的IR光谱研究了分子筛表面酸性的变化。发现NH_4F对HZSM-5分子筛有脱铝和脱硅作用,并有羟基氟化铝微晶生成。经改性后的HZSM-5表面富铝,F以取代O或OH的形式与分子筛中的Si或Al结合。NH_4F使HZSM-5总酸量减少,酸性减弱,B酸比例增加。经改性后,HZSM-5分子筛对甲苯歧化反应的催化性能将得到改善,乙苯-乙醇烷基化反应稳定性和二乙苯收率得到提高。     

球形TiO2-Al2O3的制备、结构和理化性能研究

将Ti(SO₄)₂溶于稀盐酸合成酸性钛溶胶，再将其与铝溶胶和六次甲基四胺溶液混合后采用油柱成型法制备了球形TiO₂-Al₂O₃复合氧化物。通过XRD、低温氮吸附-脱附与NH₃-TPD等手段对样品进行表征，结果表明600 ℃焙烧得到的球形TiO₂-Al₂O₃中TiO₂以无定型形式存在;随TiO₂含量的增加，球形TiO₂-Al₂O₃的比表面积、孔容和平均孔径呈增加趋势;TiO₂的引入没有对球形TiO₂-Al₂O₃的强酸和弱酸中心的强度产生影响，弱酸中心数量显著增加，强酸中心数量稍有增加;球形TiO₂-Al₂O₃的堆密度和压碎强度随TiO₂含量的增加而减小，颗粒直径基本保持不变。     

球形TiO2-Al2O3的制备、结构和理化性能研究

将Ti(SO4)2溶于稀盐酸合成酸性钛溶胶,再将其与铝溶胶和六次甲基四胺溶液混合后采用油柱成型法制备了球形TiO2-Al2O3复合氧化物。通过XRD、低温氮吸附-脱附与NH3-TPD等手段对样品进行表征,结果表明600℃焙烧得到的球形TiO2-Al2O3中TiO2以无定型形式存在;随TiO2含量的增加,球形TiO2-Al2O3的比表面积、孔容和平均孔径呈增加趋势;TiO2的引入没有对球形TiO2-Al2O3的强酸和弱酸中心的强度产生影响,弱酸中心数量显著增加,强酸中心数量稍有增加;球形TiO2-Al2O3的堆密度和压碎强度随TiO2含量的增加而减小,颗粒直径基本保持不变。     

氨基硅烷偶联剂对蒙脱石的修饰改性研究

研究了氨基硅烷偶联剂对蒙脱石的修饰改性,并和长链烷基硅烷偶联剂作对比.通过改性前后蒙脱石的傅立叶红外光谱(FT-IR),广角X射线衍射(WAXD),热失重分析(TGA)研究发现,在冰醋酸的处理下,氨基硅烷偶联剂不但能够对蒙脱石进行表面偶联修饰而且能够以插层剂的形式进入蒙脱石的层间.初步的浸润/分散性实验结果表明:氨基硅烷插层/表面修饰改性的蒙脱石在弱极性乙醇溶剂中的分散性能明显提高.     

Curing Characteristics and Tear Properties of Bentonite Filled Ethylene Propylene Diene (EPDM) Rubber Composites

The effect of bentonite clay loading on curing characteristics and tear strength of bentonite filled ethylene propylene diene monomer (EPDM) composite were studied. Compounding was carried out on two-roll mill and vulcanization was done at 150⁰C. Torque values, scorch time and optimum cure time of the prepared rubber compound were assessed by using Mosanto Disc Rheometer (MDR 2000). Results indicated that the maximum torque of EPDM/Bt composite decreases at high bentonite loading. Increasing in values with increasing bentonite loading was recorded for minimum torque and optimum cure time of EPDM/Bt composite. The increase is related with the increase in viscosity due to the increasing of bentonite clay loading in EPDM matrix. Scorch time was found to be decreasing up to 30 phr bentonite clay. Results also show that tear strength of EPDM/Bt composite increased with increasing bentonite loading up to 90 phr. The reason is probably due to agglomeration occur causes the reduction in properties at high loading above 90 phr bentonite clay. The scanning electron microscopy (SEM) of tear fracture surface of EPDM/Bt composite illustrated that with increasing bentonite loading up to 90 phr bentonite clay, a better dispersion of bentonite clay is achieved as compared to lower loading, resulting in high tear strength value for EPDM/Bt composite.     

Thermal exfoliation of electrochemically synthesized graphite intercalation compound with perrhenic acid

In present work, we describe the synthesis of graphite intercalation compounds with perrhenic acid (HReO₄-GIC) through the anodic oxidation of graphite in aqueous perrhenic acid solution and their thermal exfoliation. Due to electrochemical treatment of graphite in perrhenic acid solution, ReO₄⁻ ions are intercalated into interlayer spaces of graphite. Anodic oxidation of graphite in HReO₄ solution leads to the formation of 3-stage GIC. Simultaneously, some amount of perrhenic acid becomes deposited on the graphite surface and edges. In the next step, thermal treatment of the previously synthesized GIC was performed, causing both the exfoliation of graphitic structure and transformation of perrhenic acid into rhenium oxides on the surface of graphene layers. The yielded product was exfoliated graphite-ReO₂/ReO₃ composite. The obtained composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Additionally, specific surface area of the exfoliated materials was measured.

     

Novel composite in situ obtained from coal gasification coarse slag and its mechanism of removing phosphate

A novel low-cost hematite–silicon mesoporous composite (HSMC) was synthesized in situ from coal gasification coarse slag (CGCS) via acid modification and its potential for phosphate removal from wastewater was studied. Calcium, aluminum and iron in CGCS were activated by hydrochloric acid, and formed crystalline hematite on the quartz and silicates substrates. Compared with traditional methods of preparing hematite, this in-situ preparation method effectively utilized the iron in CGCS instead of requiring added iron salts, which is highly cost-effective. The specific surface area increased from 4 m²/g for CGCS to 67 m²/g for HSMC, greatly enhancing the phosphate removal ability of HSMC. The maximum adsorption capacity of HSMC for phosphate was 28.62 mg/g, which is more than 28 times higher than that of CGCS. The HSMC had a high point of zero charge (pH_PZC) of 7.5, providing good phosphate removal performance over a wide pH range. The phosphate removal mechanism of HSMC mainly involves ligand exchange induced by the large number of hydroxyl groups, inner-sphere complexation induced by the presence of major metal (hydr)oxides, the precipitation of calcium and aluminum with phosphate groups, and some electrostatic adsorption induced by the positively charged surface. The contribution of precipitation to the phosphate removal ability was approximately 27 %. This study provides a new method for the development of phosphate adsorbents while recycling CGCS.     

镁铝复合氧化物载体的制备与性质研究

以硝酸镁和硝酸铝为原料，用氨水溶液作为pH调节剂，采用共沉淀法制备了镁铝复合氧化物载体，研究了制备过程中镁铝比、pH调节剂种类、水解过程pH值的大小、反应温度、焙烧温度及回流晶化温度对复合氧化物载体理化性质的影响。并以RFCC汽油加氢脱硫为探针反应，考察了以镁铝复合氧化物为载体的催化剂选择性加氢脱硫性能。实验结果表明，在镁铝分子比为10、反应温度为80℃、pH值为9.5条件下制备的镁铝复合氧化物载体具有适宜的比表面积和均匀的孔分布，且晶型较完整，结晶度高。以该复合氧化物为载体制备的催化剂具有良好的RFCC汽油选择性加氢脱硫反应性能。     

Controlled fluorination of clays

The fluorination of clays by a mild fluorinating reagent, HPF₆ was investigated using a sample of bentonite. The reaction resulted in the fluorination at the aluminum sites to form octahedral aluminum oxyfluoride species. This led to considerable modification of the surface characteristics such as surface area, porosity and particle size of nano-clay particles. The fluorinated clay was characterized by X-ray powder diffraction, XPS, SEM, EDS, infrared spectroscopy and solid-state NMR.     

有机相化学镀铝法制备Al/石墨烯复合材料粉末

采用有机相化学镀法制备了Al/石墨烯复合材料粉末。使用傅里叶红外光谱仪、拉曼光谱仪、ASAP2020全自动快速比表面与孔隙度分析仪和配备EDS能谱的扫描电子显微镜表征样品。结果表明,镀铝后,石墨烯表面的含氧基团基本消失,发生空间弯曲折叠形成包覆结构,导致中孔和大孔的形成,石墨烯层间距变大。此外,氮气吸附-脱附结果显示,Al/石墨烯复合材料粉末的孔道以微孔和中孔为主,Brunauer-Emmett-Teller比表面积为91 m~2·g~(-1);通过Barret-Joyner-Halenda解吸模型计算得到的平均孔径为8.77 nm,孔体积为0.45 cm~3·g~(-1)。X射线衍射分析并没有发现Al_4C_3晶体结构的出现,表明镀铝过程并未或生成很少(小于检测下限)脆相Al_4C_3。最后,微观表面分析表明,当加入的NaH量略大于理论值时,实验结果与理想体系基本吻合,镀铝效果最佳。     

Effects of hydrochloric acid treatment on structure characteristics and C<Subscript>2</Subscript>H<Subscript>4</Subscript> adsorption capacities of Ünye bentonite from Turkey: a combined FT-IR,XRD, XRF,TG/DTA and MAS NMR study

In this study, a bentonite sample from Ünye, Turkey was treated with various HCl solutions (0.1, 1.0 and 5.0 M) at 90 °C during 3 and 6 h. X-ray diffraction (XRD), X-ray fluorescence (XRF), differential thermal analysis (DTA), thermogravimetric analysis (TG), Fourier transform infrared (FT-IR), magic angle spinning nuclear magnetic resonance (²⁹Si and ²⁷Al MAS NMR) and surface area measurement methods were employed in order to investigate the structural and thermal changes occurring as a result of the acid activation. The data for the adsorption of C₂H₄ obtained at 273 K and pressures up to 100 kPa correlated with structural properties of the acid treated bentonite samples. With the increase of both concentration of acid solution and treatment time, the specific surface area values and the retentions of C₂H₄ gas of bentonite samples increased. Bentonite treated with 5.0 M HCl for 6 h adsorbed C₂H₄ most effectively.     

Selective intercalation of charge neutral intercalators into GG and CG steps: implication of HOMO-LUMO interaction for sequence-selective drug intercalation into DNA

We have synthesized naphthopyranone epoxide 4 from D-isoascorbic acid together with its three diastereoisomers. DNA alkylation of ODNs containing 5'XGT3' and 5'TGY3' by 4 (11R, 13R), where X and Y are any nucleotide bases, occurred at all G residues except at G of the 5'TGC3' sequence. In contrast, the three other diastereoisomers of 4 showed only weak G alkylation activity. Differential (1)H NMR NOE of the 4-G adduct confirmed the G-N7 alkylation at the epoxide carbon of 4 with concomitant S(N)2 ring opening of the epoxide. Quantitative HPLC analysis of G alkylation efficiency for 4 showed the order of G alkylation susceptibility as TGGT approximately CGT > TGA > AGT > TGT > TGC. The order was fully consistent with those reported for aflatoxin B(1) oxide and kapurimycin A(3), suggesting that the sequence selectivity observed for these DNA alkylating agents is not structure dependent but most likely due to the intrinsic property of DNA sequences. We found that the order of G alkylation susceptibility obtained for 4 completely matched the calculated HOMO energy level of G-containing sequences. These results underscore that 4 is a unique molecular probe for ranking the HOMO level of G-containing sequences by well-known G alkylation chemistry and suggests that the intercalation of charge neutral intercalators is a HOMO-controlled process.     

The dynamic process in the formation of Tyr/LDH nanohybrids

The dynamic intercalation process of tyrosine (Tyr) into layered double hydroxide (LDHs) by co-precipitation method was investigated by powder X-ray diffractometry, Fourier transform infrared spectroscopy, specific surface area measurements, pore size distributions as well as thermal analysis. The nanohybrids were found to have an expanded layered structure indicating that amino acid anions were intercalated into the gallery space. Two kinds of arrangements such as mono- or bilayers of the tyrosinate anions could be deduced from the XRD patterns. The arrangement changed from monolayer to bilayer, then again to monolayer with increasing aging time of the synthesis solution. The diffraction intensity increased then decreased with aging time, because of the variation in the orientation and ordering of the particles. TG analysis and the varying M²⁺/M³⁺ results revealed that the amount of tyrosinate anions in the gallery first decreased then increased with the increase of aging time. In addition, the morphology results showed that the degree of ordering also increased then decreased with aging time. On all accounts, the intercalation of the tyrosinate anions was a typical dynamic process. At the beginning numerous biomolecules entered the gallery space, giving rise to increased basal spacings and BET surface areas. Later the increase of aging time led to the escape of amino acid anions from the gallery space, hence to the decrease of basal spacing and surface areas.     

Study on fluorescence and DNA-binding of praseodymium(III) complex containing 2,2'-bipyridine

Bentonite samples collected from vicinity of Petrovac and Aleksinac were treated with different sulfuric acid molarities. Acid attack dissolved the octahedral sheets by interlayer and edge attack. The effects of the H₂SO₄ acid caused an exchange of Al³⁺, Fe³⁺ and Mg²⁺ with H⁺ ions leading to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheets promoted the dispersion of corresponding layers and formation of amorphous silicon. The activated bentonites, after the treatment of sulfuric acid, exhibited a lower cation-exchange capacity (CEC) and significant increase of specific surface area from 6 to 387 m² g⁻¹ (bentonite from Petrovac) and from 11 to 306 m² g⁻¹ (bentonite from Aleksinac). The acid reaction caused a splitting of particles within the octahedral sheet which led to an increase in specific surface area and decrease in CEC in both bentonites.