Modification of Polyethylene with Activated Natural Zeolite

Abstract

In an attempt to improve its main physical and mechanical characteristics, the modification of high density polyethylene (HDPE) with activated (dehydrated) natural zeolite clinoptilolite, in an attempt to improve its main physical and mechanical characteristics is investigated. After dehydration at 350°C and cooling in an atmosphere of dry air, about 30% of the entire volume of the zeolite particle is freed. This free volume and the ensuing from the specific structure sorption processes-the possibility for sorption of the polymer chain on the surface channel of the zeolite particle-determine the active modification function of dehydrated clinoptilolite.     

Modification of Recycled Polymer Blends with Activated Natural Zeolite

The growing interest in the natural zeolite is based on some specific peculiarities of its structure, which after dehydration enables adsorption processes of some polymer molecules and/or segments to take place on the zeolite surface. The main goal of the study is to investigate the effect of dehydrated zeolite on the flow behavior, mechanical properties and morphology of immiscible blends from unsorted polymer wastes. A tetra-component blend consisting of 40 wt.% polypropylene (PP), 40 wt.% high-density polyethylene (HDPE), 15 wt.% low-density polyethylene (LDPE) and 5 wt.% polystyrene (PS), was studied as a model system of commingled plastic wastes. Compositions from recycled blend and dehydrated zeolite in a wide concentration range (from 0 to 20 wt.%) were prepared using a twin-screw extruder Brabender DSE 35/17D in the temperature range from 140 to 190 °C. The compositions were characterized by capillary rheometry, differential scanning calorimetry (DSC), site-resolved wide-angle X-ray scattering (WAXS) and mechanical tests. The results show a compatibilizing effect of dehydrated zeolite at low concentration levels (1-2 wt.%) and open wide possibilities for utilization of dehydrated zeolite in the recycling of unsorted polymer wastes.     

多级孔无铝Beta分子筛的合成与表征

研究了氟介质条件下,合成参数对前驱体黏度和无铝Beta分子筛晶化过程的影响.X射线衍射结果表明,高水硅比可降低前驱体的黏度,但抑制分子筛的晶化.当合成体系中加入成核促进剂(二氧化锗)和晶化促进剂(高氯酸根或磷酸根)后,即使水硅摩尔比高达20~30,在150℃水热合成4 d,仍可获得高结晶性、微米级球形或多面体形无铝Beta分子筛.热重和能谱分析结果表明,极少量高氯酸根和磷酸根可进入分子筛孔道,并影响模板剂四乙基铵根离子的热分解过程.氮气吸附-脱附、扫描电子显微镜、透射电子显微镜和选区电子衍射分析结果表明,所得无铝Beta分子筛具有多级孔结构,介孔尺寸在3.4~3.8 nm之间,由纳米晶体或纳米棒堆积而成.     

Mechanism of Coagulation Purification of Wastewater with Aluminum Oxochloride

Results of a coagulation purification of solutions modeling weakly contaminated wastewater from dairy shops are presented. The influents of detergents (HNO₃ and NaOH) and aluminum oxochloride on the process of contaminant removal from a milk solution in the pH range 2-12 is considered. Distinctions are noted in the behavior of model milk solutions with contaminant concentration. The results of studies performed at varied doses of aluminum oxochloride by the optical and electrophoretic methods are used to explain the mechanism of coagulation purification of model wastewater.     

复合改性对分子筛性能的影响

对ZSM-5烷基选择性的研究已有较多报道,但在提高对位选择性的同时,往往导致活性的损失,产生"反向效应",本文试图用复合改性来探讨解决这种效应的可能性。     

一氧化碳高效吸附剂CuCl／分子筛

利用自发单层分散原理，将ＣｕＣｌ分散在载体表面制备高效的ＣＯ吸附剂，将ＣｕＣｌ与γ－Ａｌ２Ｏ３，４Ａ，１３Ｘ，ＮａＹ，ＣｕＹ分子筛等高比表在载体混合，在３５０℃焙烧数小时，ＸＲＤ和ＥＸＡＦＳ研究证明ＣｕＣｌ可在载体表面达到原子水平的分散由于Ｃｕ＾＋可与ＣＯ生成配位键。由此可制得对ＣＯ有高吸附容量和选择性的吸附剂，其中ＣｕＣｌ／ＮａＹ和ＣｕＣｌ／Ｃｕ＾＋Ｙ吸附剂的吸附容量在２０℃，ＣＯ分压为６０ｋＰ     

高铝沸石的钙离子交换动力学研究

由于含磷洗涤剂的使用所带来的环境危害日益严重，高铝沸石作为洗涤剂助剂三聚磷酸钠的替代品已获得广泛的应用。作为洗涤剂助剂，沸石的Ca２＋、Mg２＋离子交换性能是影响其助洗效果的主要因素之一犤１，２犦。但目前对沸石的离子交换性质的研究多集中在离子交换平衡等温线的研究犤３～６犦，涉及沸石离子交换动力学的研究却鲜有报道。作为硬水的软化剂，洗涤剂用沸石对Ca２＋、Mg２＋离子的交换速率大小对洗涤效果的意义更为重要犤１犦。沸石的离子交换过程包括离子由溶液中扩散到沸石表面，再由沸石表面扩散到沸石孔道中的离子位等步骤…     

β分子筛的改性研究进展

近年来，随着人们环保和节能意识的增强，一些强无机质子酸催化剂由于腐蚀设备、难以分离、回收再生工艺复杂和污染环境等缺点而逐渐被各种固体酸催化剂所取代．这是由于固体酸催化剂具有容易分离、可回收再生及对环境无污染等优点，被认为是一种“绿色”催化剂。β分子筛作为固体酸催化剂中极为重要的一员，也越来越为人们所熟知和使用。     

沸石分子筛的表面改性技术进展

沸石分子筛的改性技术与这类材料的合成及应用一样相当大地推动了沸石化学的发展。本篇文章引用了至少90篇文献概括地介绍了最近发展起来的三种沸石表面改性方法:沸石内配位化学、化学蒸汽沉积和沸石的表面有机金属化学。     

沸石的孔口改性与气体吸附分离

沸石由干具有独特的微孔结构和表面性质，对物质的吸附表现出高度的选择性，已被广泛用于许多工业吸附分离过程．在气体分离方面，最常见的是利用沸石制造纯净的稀有气体和富氧空气．Niwa等［‘－‘］和本实验室［‘’］已成功地采用出（OCH小化学气相沉积方法对HM和Hi8M七沸石进行孔径精细调变，改善了沸石的择形吸附分离和催化性能．本文试图进一步研究沸石孔口改性在气体吸附分离方面的应用潜力．我们选择的H元气体混合物体系是NZ／OZ和CH。川。，因为O。，NZ和CH。三种分子的动力学直径分别为0．346O．364和0．380urn，相差甚…     

Defects of Zeolite Membranes: Characterization,Modification and Post-treatment Techniques

Characterization of zeolite membrane defects including SEM, dye permeation, bubble point and permporometry methods are presented. Experimental setup, governing equations and step by step procedure for obtaining pore sizes are discussed for the most useful method, i.e., the permporometry. A complete review on the techniques for elimination of defects including chemical vapor and liquid depositions, coke deposition, surface coatings, and hydrothermal treatments is presented. For each method, experimental setup, various modification conditions as well as performance enhancement of the membranes are comprehensively discussed. Finally, comparison between different methods is performed to find the more efficient techniques.     

Surface Modification of Water Purification Membranes

Polymeric membranes are an energy‐efficient means of purifying water, but they suffer from fouling during filtration. Modification of the membrane surface is one route to mitigating membrane fouling, as it helps to maintain high levels of water productivity. Here, a series of common techniques for modification of the membrane surface are reviewed, including surface coating, grafting, and various treatment techniques such as chemical treatment, UV irradiation, and plasma treatment. Historical background on membrane development and surface modification is also provided. Finally, polydopamine, an emerging material that can be easily deposited onto a wide variety of substrates, is discussed within the context of membrane modification. A brief summary of the chemistry of polydopamine, particularly as it may pertain to membrane development, is also described.     

Modification of a Nakhchivan Natural Zeolite in the Alkaline Environment

Using a Nakhchivan natural mineral as a base, zeolites of different structural types are synthesized. Natural zeolite is modified under hydrothermal conditions in aqueous solutions of LiOH, KOH, NaOH, and Ca(OH)₂, as well as in the presence of mineralizers (LiCl, KCl, NaCl, CaCl₂) in an autoclave. Based on the data of IR-spectroscopic, X-ray phase, and elemental analyses, it is shown that during the hydrothermal treatment, natural zeolite is transformed into other minerals of the zeolite group that are important in practice. It is found that mordenite retains the structure’s stability in the alkaline solutions with a concentration of 1 N at a temperature of up to 100°C for 10 h. When the conditions of hydrothermal treatment change, natural zeolite gradually transforms into hydrosodalite through the mineral phases: chabazite, heulandite, clinoptilolite, analcime, phillipsite, faujasite, scapolite, zeolite M, gismondine, leucite, and kalsilite. The presence of mineralizers in the environment leads to the production of structural types of zeolites that differ from those obtained in a thermal solution.

     

NaA型分子筛膜的合成及分离性能的研究

在自制的片状多孔陶瓷载体上,通过多次原位水热晶化合成出ＮａＡ型分子筛膜,通过扫描电子显微镜观测,发现在某些区域,小颗粒的ＮａＡ型分子筛以非常紧密的形式畸晶孪生在一起,其致密度远好于由分子筛晶粒松散无规律堆积而形成的膜排列经类膜生长形式可能是获得取致密无缺陷型分子筛膜的一种途径,单组分及双组分气体渗透测试结果表明,在所合成的分子筛膜上,晶粒间隙孔可能是主要的膜扩散通道,可凝聚气体异丁烷因发生毛细管凝     

SSZ-13分子筛膜的制备方法及其气体分离

SSZ-13分子筛具有CHA构型和3维八元环孔道结构,窗口尺寸约0.38 nm×0.38 nm。相比CH₄和N₂,SSZ-13分子筛对CO₂具有优先吸附选择性,适用于CO₂/CH₄、CO₂/N₂等体系的气体分离。SSZ-13分子筛膜的制备方法主要有原位晶化法、二次生长法、微波合成和分子筛转晶法等。高硅SSZ-13分子筛膜的疏水性随着硅铝比的增加而增加,膜层变得更加致密,缺陷减少,气体分离选择性增加。本文梳理了高硅SSZ-13分子筛膜的制备方法和气体分离的机理,分析了支撑体、合成条件、Si/Al比、测试条件和分离体系等因素对高硅SSZ-13分子筛膜气体分离的影响,展望了高硅SSZ-13分子筛膜今后的发展方向。     

CaO对ZSM-5沸石选择性催化作用的影响

为了进一步闸明ZSM-5沸石的选择性催化作用,本文利用CaO对其改性,从实验和理论计算方面探讨对二甲苯选择性的变化,得到一些有意义的结果。(一)实验及结果ZSM-5沸石原粉,经HCl交换成HZSM-5沸石,再和CaO按一定比例混合在一定温度下焙烧数小时,即为改性的催化剂HZSM-5-CaO。     

Highly Selective Zeolite Topologies for Flue Gas Separation

The separation of carbon dioxide from flue gas is essential for the reduction of greenhouse gas emissions. In adsorptive methods, the challenge lies in the choice of suitable porous materials. Among all zeolite topologies, a number of adsorbents with pore dimensions in the range of the guest molecules were identified to allow an excellent separation by diffusion, and MRE and AFO zeolite topologies appear to be the best candidates based on equilibrium adsorption. Also, it was found that the behavior of this gas mixture in DFT and APD zeolites differed from the normal behavior.     

Extra‐Framework Aluminum Species of Zeolite that Surrogate the Growth of Metal Organic Framework from Zeolite Matrix

Constructing a robust hybrid material with a porous inorganic and a porous organic framework is highly intriguing owing to its diverse functionality and porosity. However, the line of synthesis is not straightforward, since their nucleation and crystal growth processes are incompatible. Here, a simple method for the fabrication of hybrid zeolite/metal–organic framework of different framework structures is developed wherein the less‐useful extra‐framework aluminum species present in the zeolite surrogate the growth of metal organic framework (MOF) from the zeolite matrix in the presence of organic linkers of the corresponding MOF. An NMR study confirms that all the octahedral Al species are converted to Al‐MOF. TGA analysis shows that 32 % Al of H‐Beta is converted to Al‐MOF. Furthermore, NH₃ TPD analysis shows that most of the weak acid sites disappear but strong acid sites are preserved suggesting the utilization of weakly bound Al species of H‐Beta in the growth of Al‐MOF. The synthesis strategy is successfully demonstrated using H‐Beta, H‐ZSM‐5, and H‐Y zeolites for the growth of MIL‐53 and MIL‐96 MOFs from the zeolite matrix. This synthesis strategy enables application‐based engineering of the framework structures, functionality, and porosity of the materials.     

Modification Study of Aluminum sec-Butoxide by Acrylic Acid

A new way of modifying aluminum sec-butoxide (Al(OBu^s)₃) is proposed. This synthesis is carried out by reacting Al(OBu^s)₃ dissolved in tetrahydrofuran with an unsaturated acid, viz. acrylic acid.The structure evolution of Al(OBu^s)₃ with increasing acrylic acid amounts is investigated by infrared, ¹H NMR, ¹³ C NMR, and ²⁷Al NMR spectroscopies and viscosity measurements. Information obtained suggests that the exchange reaction occurring between butoxy groups and acrylate ligands is stopped for an acid/alkoxide molar ratio within the range 1.6–1.7. This value leads us to assume that the dominant trimeric species of precursor is preserved after modification. Moreover, ²⁷Al NMR analysis only reveals the presence of hexacoordinated Al sites in the structure of the modified Al(OBu^s)₃.Evidence of the acrylic acid reaction with sec-butanol released during the alkoxide modification is also proved by the infrared and ¹³ C NMR data. However the produced ester amount can be considered as negligible.