青霉素酰化酶在介孔分子筛MCM-41上的固定化研究

通过改变酶固定化时的pH值、温度、时间以及酶用量,研究了固定化条件对MCM-41载体上固定化青霉素酰化酶的酶活及其稳定性的影响,明确了酶活及其稳定性随固定化条件的变化规律,初步分析了青霉素酰化酶在介孔分子筛MCM-41上的固定化过程。     

自制Ti/W-MCM-41介孔分子筛催化制备乳酸戊酯

采用自制的介孔分子筛Ti/W-MCM-41催化乳酸与正戊醇的酯化反应,合成了乳酸正戊酯;利用红外光谱仪分析了催化剂的化学特征,考察了分子筛的WO3质量分数、催化剂用量、醇酸物质的量比、反应时间、催化剂重复使用性能等因素对目标产物酯化率的影响.结果表明,在nSi∶nTi=30∶1,WO3质量分数10%,550℃下焙烧6h条件下制得的催化剂具有良好的催化性能;其催化合成乳酸正戊酯适宜的反应条件为:0.2mol乳酸,催化剂用量0.5g,n(正戊醇)∶n(乳酸)=1.6∶1,反应时间100min,酯化率可达94.4%.该催化剂使用7次酯化率仍可达86.6%.     

MCM-41分子筛的改性、表面结构与吸附性质的研究

用三甲基氯硅烷、二甲基二氯硅烷、甲基三氯硅烷、四氯化硅与甲基碘改性高硅MCM-41中孔分子筛。XRD,^2^9SiMASNMR,^1^3CMASNMR,以及N~2、水与环己烷吸附的表征,显示改性不同程度地改变了分子筛的表面组成与结构,减小孔径,增加孔壁厚度,因而影响吸附行为,减小吸附容量。硅烷化减少了MCM-41的表面硅羟基含量,增加其疏水性。用CH~3I改性使孔径减小1.4nm,而硅羟基含量并未显著减少。硅烷化以及用CH~3I改性可提高MCM-41分子筛的热稳定性。SiCl~4的改性作用相对不明显。样品的水及环己烷吸附容量与其表面硅羟基含量呈现不同的线性关系,揭示高硅MCM-41分子筛表面吸附中心的本性。     

MCM-41分子筛和催化剂的特殊吸附等温线

测定了MCM-41中孔分子筛和催化剂的吸附等温线, 发现它们形状非常特殊, 不仅可逆部分分两段, 并且还存在两个滞后环, 在相对压力0.4以前出现的第一个滞后环可归属于中孔孔道内的毛细凝聚, 在饱和压力附近出现的第二个滞后环可归属于分子筛颗粒之间的毛细凝聚。利用吸附和XRD数据, 可有效地表征MCM-41分子筛和催化剂的结构有序度和孔道畅通情况。     

Solid-state NMR study of MCM-41-type mesoporous silica nanoparticles

A systematic study of the surface of MCM-41-type mesoporous silica nanoparticles prepared under low surfactant concentration was carried out using high-resolution solid-state nuclear magnetic resonance spectroscopy. The structures and concentrations of various species present during dehydration and rehydration of mesoporous silicas between -25 and 500 degrees C were detailed by employing one-dimensional and two-dimensional (1)H, (13)C, and (29)Si NMR, including (1)H signal intensity measurements, (1)H-(1)H homonuclear correlation experiments (double quantum, exchange, and RFDR), and (1)H-(29)Si heteronuclear correlation NMR. These experiments employed high MAS rates of up to 45 kHz. The study shows that the surfactant (CTAB) was almost completely removed by acid extraction. The residual molecules assumed prone positions along the pores, with the tailgroup being most mobile. The weakly adsorbed water was hydrogen bonded to the silanol groups, all of which were involved in such bonds under ambient humidity. Specific structures involving water and silanol groups were proposed for various stages of thermal treatment, which included dehydration, dehydroxylation, and subsequent rehydration.     

Synthesis, characterization, and catalytic properties of stable mesoporous molecular sieve MCM-41 prepared from zeolite mordenite

Mesoporous molecular sieves (denoted as M-MCM-41) with ordered hexagonal structure have been successfully synthesized from the assembly of precursors from preformed zeolite Mordenite with CTAB surfactant micelle in alkaline media. The samples were characterized by XRD, N₂ adsorption, IR and DTG. The materials exhibit highly hydrothermal stability, as compared with conventional MCM-41. Characterization results indicate that the mesoporous walls of M-MCM-41 contain the secondary building units similar to those in microporous crystal of zeolite Mordenite. In catalytic dealkylation of C10⁺ aromatic hydrocarbon, M-MCM-41 shows higher activities in comparison with Mordenite and MCM-41, which would be ascribed to the combination of advantages of both MCM-41 (large pores) and Mordenite (strong acidity). Furthermore, this synthesis strategy could be used as a new general method for the preparation of hydrothermally stable mesoporous aluminosilicate materials under alkaline conditions.     

Photoluminescence study of mesoporous MCM-41 and Ti-grafted MCM-41

Photoluminescence combined with diffuse reflectance UV—Vis spectroscopy was used to characterise both the pure siliceous MCM-41 and Ti-MCM-41 containing tetrahedral Ti(IV) species anchored onto the inner walls of the siliceous MCM-41. Both Ti-MCM-41 and MCM-41 showed complex photoemission signals and this study allows, for the first time, the distinction of the emission signals of tetrahedral Ti9IV) ions from those due to silica surface centres.     

杂原子介孔Co-MCM-41分子筛的制备及其吸附脱氮性能

采用水热法合成了介孔MCM-41和Co-MCM-41分子筛,并利用XRD、FT-IR、低温N₂吸附-脱附和NH₃-TPD等方法对合成的分子筛进行了表征。考察了晶化时间、晶化温度、陈化时间对合成介孔Co-MCM-41分子筛的影响,确定较适宜的合成条件为陈化时间1 h,晶化温度110 ℃,晶化时间2 d。XRD 和FT-IR表征结果说明,Co原子已经进入MCM-41的骨架。MCM-41和Co-MCM-41的平均孔径均为2.82 nm,BET比表面积分别为986.42和 637.69 m²/g,孔容分别为0.762 1和0.537 2 m³/g。NH₃-TPD的表征结果表明,MCM-41和Co-MCM-41的酸性都较弱,但Co-MCM-41的酸性明显强于MCM-41。在此基础上,利用合成的MCM-41和Co-MCM-41吸附脱除氮含量为1 737.35 μg/g的模拟燃料中的喹啉。喹啉分子尺寸的模拟结果为0.711 6 nm × 0.500 2 nm,说明其可以很容易地进入MCM-41和Co-MCM-41的介孔孔道中。Co-MCM-41分子筛的氮脱除率明显高于MCM-41,这是由于其较强的酸性及与喹啉之间的化学吸附,而且,Co-MCM-41吸附脱氮具有较好的再生性能。     

Anchoring of 1,8-naphthalimide derivative into mesoporous MCM-41 molecular sieves

The fluorescent dye molecules, 4-piperidine-1,8-naphthalimide, were successfully fixed into the amino modified pore channel of mesoporous MCM-41 type materials by in situ reaction of 4-piperidinyl-1,8-naphthalic anhydride with the amino group. The formation of amide bonds on the pore surface was verified by infrared spectra. The maximum fluorescence emission peak of this hybrid material has a red shift of 13 nm compared to that of a naphthalimide derivative in ethanol solution. Moreover, the fluorescence intensity of dye molecules grafted into Ce-doped MCM-41 is higher than that in pure silica MCM-41. This phenomenon is attributed to the inhibited internal electron transfer from piperidine to naphthalimide groups by Ce⁴⁺, thus improving the fluorescence intensity of the naphthalimide group. The unique fluorescence behavior of the 1,8-naphthalimide derivative doped hybrid mesoporous material makes it a good candidate for the metal ions microdetection.     

外围为柔性链状取代基团Ni-酞菁配合物的合成及其在MCM-41中的装载

合成了外围具有柔性链状基团的2（3）,9（10）,16（17）,23（24）-四-（N,N-二乙胺基乙氧基）Ni-酞菁配合物（2）．以正硅酸乙酯为硅源,十六烷基三甲基溴化铵为模板剂,水热法将该Ni-酞菁配合物（2）装载到MCM-41中．利用UV-Vis-NIR,FT-IR,XRD,TEM,FESEM及N2吸附-脱附等温线对制备的样品进行了表征．研究表明制备的样品中Ni-酞菁配合物（2）主要以单体和二聚体的形式存在于MCM-41中．通过不同制备酞菁浓度的装载研究表明,较高制备酞菁浓度有利于制备结晶度及孔道有序性较高的介孔分子筛样品．     

Characteristics of molecular sorption on template containing mesoporous molecular sieves of type MCM-41

Template containing materials of type MCM-41 have properties of microporous substances. On absorption into the micropores of such materials the dependence of the characteristic absorption energies on the molecular mass of the sorptive is extreme, and the specific absorption volume decreases with increased molar volume of the sorptive. A model is proposed to explain the peculiarities of the absorption properties of the template containing materials. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 6, 367–372, November–December, 1999.     

Effect of rehydration on the porosity of MCM-41 mesoporous molecular sieves

In distinction from aluminosilicates, the porosity of the detemplated silicous MCM-41 is significantly reduced after several cycles of dehydration-rehydration. The stability of Si-MCM-41 is not changed by absorption-desorption of nonpolar hexane. An explanation is proposed for the effect of rehydration on the porosity of MCM-41. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 50–55, January–February, 1999.     

Mo-MCM-48中孔分子筛微波辐射合成的研究

在微波辐射下快速合成含Mo离子的MCM-48分子筛,考察了微波反应釜压力和反应时间对Mo-MCM-48合成的影响,并用XRD,TEM,FT-IR和N2吸附进行表征。结果表明：微波辐射下能快速合成结晶良好的Mo-MCM-48分子筛;合成时以0.481MPa压力、反应2h为宜;Mo离子进入MCM-48分子筛的骨架;焙烧结果表明Mo-MCM-48热稳定性较好。苯乙烯催化氧化结果表明Mo-MCM-48具有一定的催化氧化活性。     

Synthesis and catalytic performance of ZSM-5/MCM-41 composite molecular sieve from palygorskite

ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterification of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template. XRD patterns, N₂ adsorption and desorption data, and TEM images show that the composite obtained in the secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase. Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetalization and esterification reaction.     

Effect of titanium on the structure and properties of mesoporous MCM-41 molecular sieves

Mesoporous MSM-41 titanium silicate molecular sieves with high titanium content were synthesized. The hexagonal structure along with high specific surface and pore volume are retained up to Si/Ti≥5. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 177–182, May–June, 1999.     

MSU-x介孔分子筛的改性研究

以脂肪醇聚氧乙烯醚为模板剂,正硅酸乙酯为Si源,分别以偏钨酸铵,硫酸铝作为W源和Al源进行改性,合成出W-MSU-x以及Al-MSU-x介孔分子筛.并且通过X射线扫描、N_2吸附-脱附、原位红外表征考察W和Al的加入对介孔分子筛的影响.结果得到,W的加入提高了分子筛的有序度,Al的加入使介孔分子筛的孔径减小,比表面积增大.     

Sulfonic acid functionalized mesoporous MCM-41 silica as a convenient catalyst for Bisphenol-A synthesis

Sulfonic acid groups anchored to the surface of mesoporous MCM-41 silica have been identified with S K-edge XANES spectra and the material is an efficient catalyst for the liquid phase condensation of phenol with acetone to form Bisphenol-A with high selectivity.     

杂原子介孔Co-MCM-41分子筛的制备及其柴油深度吸附脱碱氮性能

以硝酸钴为钴源,采用水热法合成了MCM-41和不同Co含量的Co-MCM-41分子筛,并利用XRD、FT-IR和低温N2吸附-脱附等方法对合成的分子筛进行表征。当加入的Co/Si物质的量比达到0.1时,依然能够成功合成具有规整有序的介孔结构的Co-MCM-41。MCM-41和Co-MCM-41静态吸附脱除0#柴油中碱氮的实验结果表明,Co/Si物质的量比为0.06的Co-MCM-41(2)分子筛的吸附容量最大,达到5.324 mg(N)/g分子筛,明显高于MCM-41分子筛的吸附容量2.532 mg(N)/g,说明Co进入MCM-41分子筛骨架后显著提高了分子筛的吸附脱除碱氮能力。当加入的Co/Si物质的量比大于0.06时,分子筛吸附脱除柴油中碱氮的能力反而下降,这是由于加入过多Co会使其以Co3O4形式高度分散在分子筛孔道中,堵塞了吸附活性位,使其无法与碱性氮化物接触造成吸附脱氮能力下降。动态吸附脱除0#柴油中碱性氮化物的结果表明,每克CoM CM-41(2)分子筛可将35 m L柴油的碱氮从147.54μg/g吸附脱除到10μg/g以下,吸附容量为4.2 mg(N)/g(吸附剂),由于动态吸附的接触时间较短使MCM-41失去了吸附脱氮能力,说明Co-MCM-41(2)对柴油中的碱氮具有较好的选择性。     

Hydrogenation of naphthalene on noble-metal-containing mesoporous MCM-41 aluminosilicates

Aromatic saturation of oil fractions is a key process in the refining industry due to increasing demand for cleanest distillates with superior performances. In this study, the behavior of different catalysts containing 1 wt.% of noble-metal inside a mesoporous MCM-41 (Si:Al=20) framework was investigated in the hydrogenation of naphthalene, as preliminary step to investigate bimetallic catalysts. While at atmospheric pressure only Rh and Pd showed a low hydrogenation activity, in the tests performed at 6.0 MPa the catalytic activity grew, exhibiting the following order: Pt>RhPd>>>Ru≈Ir. However, all the catalysts required a large H₂ excess, to avoid a decrease in hydrogenation and ring-opening activity, and gave rise to the best performance for a contact time of 6.8 s, favouring at lower values the partial hydrogenation to tetralin and at higher values cracking reactions. Finally, all the catalysts showed low thio-tolerance, with significant deactivation already feeding 100 ppm wt. of dibenzothiophene (DBT), with a partial reversibility only for the Pt-containing catalyst (CAT 3).     

Epoxidation of cyclohexene on modified Ti-containing mesoporous MCM-41

Ti-MCM-41, B-Ti-MCM-41 and Ti-grafted MCM-41 were synthesized, characterized and studied in the epoxidation of cyclohexene. The synthetic methods and the effect of water in the oxidant are discussed.