4a molecular sieve
4a分子筛是一种人工合成的、具有微孔型立方晶格的碱金属硅铝酸盐。4a分子筛又叫钠a分子筛，其结构与nacl的类似。由于4a分子筛的有效孔径为0.4nm，故称为4a分子筛，其空间网络结构由硅氧四面体单元（sio4）和铝氧四面体（alo4）单元交错排列而成。4a分子筛根据不同物质分子的极性决定优先吸附的次序，只吸附那些直径小于4a的分子。对于小的极性分子和不饱和分子，极性越大，不饱和度越高，其选择吸附性越强。远影生产的4a分子筛具有吸附速度快、再生次数多、抗碎强度高，抗污染能力强，寿命长等特点。
4a分子筛能吸附水、甲醇、乙醇、硫化氢、二氧化硫、二氧化碳、乙烯、乙烷、丙烯、氨等直径小于4a的分子，不吸附直径大于4a的任何分子（包括丙烷），对水的选择吸附性能高于任何其他分子。
4a分子筛无毒无味，对眼睛、皮肤无刺激，不会导致过敏。在洗涤后沉积于土壤中，不会造成污染，而且还可以改良土壤，是一种天然环保产品。
4a分子筛用于（1）氩气的制取和净化；（2）洗涤剂助剂、香皂的成型剂、牙膏的摩擦剂等；（3）污水处理；（4）冶金工业分离剂；（5）石化工业用作催化剂、干燥剂、吸附剂；（6）农业上用于土壤改良剂；（7）医药上用于载银沸石抗菌剂；（8）家用冷冻系统、药品包装、汽车空调、电子元件、易受潮变质物质、易变质化学品中作为静态干燥剂；（9）可用于r-12和r-22系统中，凡可吸附于3a型分子筛上的分子都能被4a所吸附。
3a、4a、5a、13x分子筛可用加热并同时吹扫或抽空的方法再生。
1）脱除水份：可用干燥气体如氮、空气、氢、饱和碳化氢等加热至150-320℃在0.3-0.5kg/m2压力下通入分子筛床层，持续3-4小时，然后向吸附器通入干燥的冷气体约2-3小时，隔绝空气冷至室温；
2）脱除有机物质：可用水蒸气先将吸附质从分子筛中替代出来后，再按照第一步骤进行；也可在 200-350℃过热蒸气或过惰性气体通过再生；
3）脱除气体物质可用减压脱除法再生。
overview
4a molecular sieve is a kind of synthetic, with micropore cubic lattice of alkali metal aluminosilicate salt. it also called sodium a molecular sieve, its structure is similar to nacl. due to its effective pore diameter is 0.4nm, so it is called 4a molecular sieve, its space network structure is staggered by silicon-oxygen tetrahedron (sio4) and aluminium-oxygen tetrahedron (alo4). 4a molecular sieve decides the adsorption order according to the polarity of different molecules, adsorbs only those with a molecular diameter of less than 4a. for small polar molecules and unsaturated molecules, the greater polarity, the higher degree of unsaturation, the stronger of selective absorption.
in the skeleton of 4a molecular sieve, each oxygen atom is shared by two adjacent tetrahedrons, these structures formed a large crystal cave, positive ions and water molecules can be exchanged and reversible dehydration in the crystal cave. the ion-exchange of 4a molecular sieves is in crystals which have aluminium ions, each of aluminum ions with a negative charge, which can be combined with cations such as sodium, calcium and magnesium. calcium ions and magnesium ions can replace sodium ions and enter crystal caves which were occupied by the sodium ions. it shows that sodium ions can be exchanged by ca2+, mg2+ ions in hard water, so 4a molecular sieve can soften water. 4a molecular sieve also can remove a small amount harmful heavy metal ions (such as pb2+、cd2+、hg2+) in water, it is very important for purifying water.
4a molecular sieve adsorbs those substances which molecular diameter is less than 4a, such as water methanol, ethanol, hydrogen sulfide, sulfur dioxide, carbon dioxide, ethylene, ethane, propylene, ammonia, doesn’t adsorb molecules which diameter are greater than 4a (include propane), the selective adsorption performance to water than any other molecules.
4a molecular sieve is nonpoisonous and tasteless, no irritations to eyes and skin, does not cause allergies. 4a molecular sieve deposition in the soil after washing will not cause pollution, furthermore can improve soil, so it is a natural and environment-friendly product.
yuanying 4a molecular sieve has excellent adsorption performance, high mechanical strength, large specific surface areas and big pore volume.
application
(1) argon gas making and purifying
(2) detergent builder: 4a molecular sieve as a detergent builder mainly used to exchange of calcium ions in water to soften water, remove dirt and prevent dirt deposition. 4a molecular sieve substitute trisodium phosphate as detergent builder is a significant role on solving environmental pollution. 4a molecular sieve also is used for soap plasticizer, toothpaste abrasive, etc.
(3) sewage disposal: 4a molecular sieve as a softening agent instead of domestic widespread sulfonated coal, thereby reducing costs. in sewage 4a molecular sieves can remove ammonia nitrogen, pb2+、cu2+、zn2+、cd2+, etc. in addition to ensure water quality qualified, but also can recycle heavy metal.
(4) metallurgical industry separating agent: separation, extraction of potassium, rubidium and cesium in brine. in the industry it is used for collection, separation and extraction of metals and other processes.
(5) petrochemical industry as catalyst, drying agent, adsorbent: depth drying gas and liquid such as air,  natural gas, lpg, inert gas, hydrocarbons, saturated hydrocarbons, refrigerant; dehydrating agent for paint, polyester, dyes and coatings.
(6) for agricultural soil conditioner.
(7) medicine for silver zeolite antibacterial agent
(8) static desiccant for household refrigerating systems, pharmaceutical packaging, automotive air conditioning, electronic components, easy to wet and deteriorate material, perishable chemicals.
(9) used in the r-12 and r-22 system, molecules adsorbed by 3a molecular sieve can all be adsorbed by 4a molecular sieve.
regeneration:
1. water desorption: for re-use by purging or evacuating at temperatures of 200~350°c and pressure of 0.3~0.5kg/cm2
2. organics desorption: use water vapors replace organics, then water desorption.
storage:
on room temperature, relative humidity not more than 90%; not lay bare in the air; keep away from water, acid and soda

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