What is zeolite desiccant.

Aluminosilicate compound having a cubic lattice, is mainly composed of silicon aluminum attached through an oxygen bridge consisting of the open framework structure, there are a lot of uniform pore size and neat in pore structure, large surface area of the inner hole. It also contains a low price and a larger ionic radius of metal ions and the chemical form of water. Since the water molecules in the continuous loss of heat, but the same crystal framework structure, the formation of many of the same size of the cavity, the cavity there are many of the same diameter connected pores, the diameter of these small pores of uniform size, pore ratio can diameter smaller molecules adsorbed into the interior of the cavity in the past, and the ratio of pores too large molecular exclusion, and thus able to molecular diameter different shapes, different degree of polarity of the molecule, the boiling point of different molecules, the different degree of saturation of molecular separation open, that has the effect of "screening" elements, so called molecular sieves. Currently #zeolite #desiccant widely used in the metallurgical, chemical, electronics, petrochemical and natural gas industries.

Variety of zeolite

Zeolite nature have been found more than 30 kinds, more common well-synthetic zeolite powder supplier, chabazite, calcium, heulandite, sodium zeolite, mordenite, Stilbite, etc., are to calcium, sodium based. How much of their water content varies with ambient temperature and humidity changes. Crystals belong to crystal system with different mineral species varies, with monoclinic and orthorhombic (orthorhombic) majority. Analcime, chabazite often has equiaxed crystal form, heulandite, Stilbite form of a plate, erionite, mordenite acicular or fibrous, phillipsite and boiling Danshuang Jing Hui common. Pure various zeolites are colorless or white, but may be due to a variety of light-colored impurities and mixing. Shiny glass. Cleavage varies with the crystal structure. Mohs hardness medium. The proportion ranged from 2.0 to 2.3, containing barium is up from 2.5 to 2.8. zeolite molecular sieve formed in the epithermal stage, common in extrusive rock pores, also found in hydrothermal deposits and the modern spa deposition. The zeolite may be the action of water by diafiltration to exchange cations, the ingredients sodium, calcium ions can be exchanged with an aqueous solution of potassium and magnesium ions to soften hard water industry. The crystal structure of the zeolite comprises silicon (Al) oxy connected into a three-dimensional tetrahedral framework, grid has a variety of different sizes of holes and channels with large open. Alkali metal or alkaline earth metal ions and water molecules are located in the holes and channels, to contact grid is weak. Different ion exchange on the zeolite structure has little effect, but the nature of the 4a zeolite powder so that change. Present in the crystal lattice of different size cavities, can absorb or filter elements of different sizes other substances. Industrially often as a molecular sieve, to purify or separate components of the mixed material, such as gas separation, oil purification, treatment of industrial pollution.

X and Y-type zeolite is wider application of two kinds of zeolite

X and Y-type dehydration of natural gas is used widely two zeolites, they all belong to the faujasite type, its crystal structure is identical, the difference lies in Al ratio (SiO2 / Al203) are different. While the unit cell contains 192 silicoaluminophosphate atoms, but Y-type silicon content is higher, closer to faujasite. Precisely because of the different silica to alumina ratio of these two types of molecular sieves are the difference in acid resistance, thermal stability and so on. 
Faujasite-type crystal structure similar to that of diamond structure. Diamond crystals are composed of carbon atoms, it has four chemical bonds of carbon atoms in space at an angle to each other (about 109.), a chemical bond between the carbon atoms are connected to each other. In terms of cutting angle octahedral (ie β cages) instead of diamond crystals all the carbon atoms between adjacent β cage by six-membered rings are interconnected by six oxygen bridge (chamfered octahedron has eight six-membered ring, only use one of the four, and one by one, to connect with each other across). Faujasite structure is so connected together, that is, the crystal structure of X-type and Y-type molecule. 
And A-type zeolite as described above when the β cages connected to each other, but also the formation of two new cages, the cage is a cage when two β through six-membered rings are interconnected by an oxygen bridge formed, which cage is actually a hexagonal prism, hexagonal column called cage, the volume of hexagonal pillar cage cages smaller than β; another new cage called "faujasite cage", which is surrounded by a hexagonal columnar β cages and cage made. Faujasite cage by eighteen four rings, four six rings and four twelve ring posed. Faujasite cage and faujasite cage through twelve ring communication, its volume is much greater than β cages, cavity volume of 850 Å 3 and an average diameter of 12.5 Å. 
Faujasite cage is the main hole X and Y type zeolite, through six-membered ring or a four-membered ring and a cage surrounding the β communication, connected by four-membered ring and a cage surrounding the hexagonal column, more importantly twelve by four adjacent ring and around the other four interlinked faujasite cage. Twelve-membered ring diameter is 8-9 angstroms, is the main channel X and Y-type zeolite. 
X and Y type zeolite unit cell contains 192 silica (including aluminum oxide) tetrahedron, the equivalent of eight β cages. Typical X-type zeolite 13x unit cell formula 
Na86 [(AlO2) 86 (SiO2) 106] • 264H20 
Indeed Depending SiO2 / Al203 ratio of the unit cell formula is also a difference. Typical Y zeolite unit cell formula 
Na56 [(AlO2) 56 (SiO2) 136] • 264H20 
Faujasite zeolite cations often distributed in a predetermined position, the position of some commonly used symbols. For sodium faujasite type, the cations have three positions (SI, SII, SIII), SI cage located hexagonal columns, each cell has 16 positions; β cages located near the SII six-membered ring, each crystal Cellular has 32 ​​positions; SIII is located on a four-membered ring β cages, each cell has 48 locations. 
In the process of exchange of sodium ions in the faujasite with other metal ions found more cationic distribution locations, which are generally in the cubic unit cell diagonal to S1, S2, S3, S4, S5 private U and other symbols. Table 1 lists the names and numbers of these locations. 
It should be noted, these six cation distribution location above three cation is not entirely correspond to the distribution location. Due to the location of the different metal ions in the crystal, its performance is also different.

Jinshan District of Shanghai Petrochemical production safety inspection group to check the street drinking water source enterprise

Recently, the area of ​​production safety joint law enforcement inspection team on the streets of drinking water sources and petrochemical companies to conduct joint law enforcement inspection. Law enforcement officers were widely distributed within the company of Shanghai Petrochemical street renovation scope ash yard drinking water sources, such as six companies conduct special inspections, in the immediate vicinity of Shanghai GF moat companies ash yard, a large number of open dumps dehydration of natural gas, employee job protection measures in place, damaged docks along the river dikes, heavy rain can easily fly ash burst river, law enforcement officers of the company out of a rectification notice, order business for rectification. Aetna Steel Co., Ltd. in Shanghai, law enforcement officers also found a violation electric wire connection box, oxygen, propane gas safety distance is not enough, painting smoking area employees and other security risks.
It is understood that, for security risks and needs rectification of problems found in the inspection, the next one, law enforcement agencies will be reviewed, the safety accidents to a minimum. (Jinshan television reporter Fan Guoqing)

Knowledge of the structure and characteristics of zeolite molecular sieves collection

Molecular sieve is a silicate or a crystalline aluminosilicate, and formed of silicon oxide or aluminum oxide tetrahedra linked by oxygen bridges tetrahedron. Molecular size (typically 0.3 ~ 2.0 nm) of the pore and cavity system, so as to have characteristics of solid molecules. However, with the synthesis and application of molecular sieve-depth study, researchers found that the aluminophosphate molecular sieves and sieve skeleton elements (silicon or aluminum or phosphorus) may be composed of B, Ga, Fe, Cr, Ge, Ti, V , Mn, Co, Zn, Be and Cu, substituted, its pore size and the cavity may reach 2 nm or more, the zeolite framework elements can be divided according to type aluminosilicate zeolite, aluminophosphate molecular sieves and molecular sieve framework heteroatoms ; divided by pore size, pore size of less than 2 nm, 2 ~ 50 nm and the molecular sieve is larger than 50 nm are referred to as micropores, mesopores and large pore molecular sieves. Because of the larger aperture size becomes larger carrier molecules react well, but the pore walls of mesoporous materials are amorphous, resulting in the hydrothermal stability and thermal stability still can not meet the required conditions for petrochemical applications demanding .
molecular sieve molsiv sieves contain a lower price due to the larger ionic radius and water, the #water #molecules are continuously lost after heating and combined state of the metal ion, but the same crystal framework structure, the formation of many of the same size of the cavity, the cavity there are many the same diameter of pores connected to these tiny hole diameter uniform pores smaller than molecules can adsorb to the internal diameter of the cavity in the past, but larger than the pores of the molecular exclusion, which can diameter molecules of different shapes Different degrees of polar molecules, the boiling point of different molecules, different degrees of saturation molecules separated, that has the effect of "screening" elements, so called molecular sieves. Currently zeolite 5a widely used in the metallurgical, chemical, electronics, petrochemical and natural gas industries.

There are two kinds of synthetic zeolite molecular sieve zeolite and natural. Most ① natural zeolite formed by volcanic tuffs occur and tuffaceous sedimentary rocks in marine or lacustrine environment reaction. Has been found to have more than 1000 kinds of zeolite mineral, the more important ones are 35 kinds, often with clinoptilolite, mordenite, erionite and chabazite, etc. Mainly in the United States, Japan, France and other countries, China also found that a large number of mordenite and clinoptilolite deposits, Japan is the most natural zeolite molecular sieves mined large country. ② due to natural zeolite subject to resource constraints, from the beginning of the 1950s, a large number of synthetic zeolites (see Table).

Goods zeolite crystal structure common prefixes Digital classify the different molecular sieves, such as type 3A, 4A type, 5A zeolite. 4A Class A type that table, aperture 4 & Aring ;. A type containing Na + sieve recorded as Na-A, if one Na + is K + replacement, pore size of about 3 & Aring ;, is the 3A molecular sieve; as Na-A has more than 1/3 of Na + was Ca2 + exchange, aperture is about 5 & ​​Aring ;, is the 5A molecular sieve.

Preparation of synthetic zeolite

According to Japan's "plaster and lime" magazine: synthetic zeolite powder generally use sodium silicate solution and sodium aluminate solution, and Na: O, 510:, AI: 03 and according to the provisions of the proportions of each component generated H20 aluminum silicate condensate glue, heated, crystallized synthesis. The synthesis conditions such as changing the mixing ratio of the respective components, the heating temperature and the like can be prepared by stirring a wide variety of synthetic zeolites. Synthetic zeolite has a unique crystal structure, pore size, surface field, adsorption separation energy, energy, and other physical and chemical properties of solid acidic ion-exchange, it is used as a functional substance is used as adsorbents, molecular sievess, ion exchangers, catalyst. Production of synthetic zeolite between 1957 and 1959 in Japan, such as the table below. The maximum demand of synthetic zeolite is used as a washing powder. Secondly, as an adsorbent, the amount of catalyst required is large, such as the 1989 production for other uses 8500 tons, the sorbent is 3500 tons, 3,000 tons of catalyst. Recently, the use of synthetic zeolite crystalline uniformity characteristics of particle shape and size as the plastic filler with an amount increasing. Other also as paper, rubber filler, deodorant, preservatives, anti-bacterial agent. Especially as pharmaceuticals, electronic materials, high functional materials have been partially practical

The country has made great breakthroughs of the zeolite molecular sieve materials research

Zeolite is a crystalline aluminosilicate hydrate of metal salt, defined by the formula: Mx / m [(AlO2) x · (SiO2) y] · zH2O. M represents a cation, m represents the number of its valence, z is a hydration number, x and y are integers. After the activation of zeolites, the water molecules are removed, the remaining atoms to form a cage-like structure, a pore size of 3 ~ 10 & Aring ;. Molecular sieve crystals have a number of holes with a diameter (also called "window") is connected between a plurality of holes of a certain size, a hole. Because molecular sieve can adsorb molecules smaller than the pore diameter into the hole inside, but larger than the pore size of the molecular exclusion in its hole, but played the role of screening molecules, so named molecular sieves.
Progress made series FJIRSM CAS researcher Zhang Jian led the research team recently on the zeolite molecular sieve oxysiv materials research. Research group designed and synthesized a series of metal organic zeolite material not only has a higher specific surface area and pore structure excellent regulation performance, and hydrogen storage, carbon dioxide capture and catalysis research shows potential applications.

The Task Force also benefit organic framework compounds successfully synthesized molecular sieve type case has MTN topology fluorescent molecular sieve materials development provides a new idea. In addition, they are still the class of molecular sieve material gas adsorption and catalytic properties of the series has also made progress in other chiral porous materials developed for CO2 adsorption capacity of porous material than has been reported.
Zeolite adsorption has two characteristics:
(1) Lewis center polar surface on strong;
(2) zeolite cages or channels of small size makes them very strong gravitational field. Therefore, the adsorption capacity of the adsorbate molecules is far more than other types of adsorbents. Even adsorbate partial pressure (or concentration) is low, the adsorption capacity is still considerable. Zeolite adsorption separation not only with the size and shape of the adsorbate molecules, but also on their polarity, and therefore, zeolitic molecular sieves can also be used to separate substances of similar size.