Molecular sieve

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Typical molecular sieves are of the LTA type. They feature sodium aluminosilicates cages (sodium not shown) that have high affinity for water. LTA (cropped).png
Typical molecular sieves are of the LTA type. They feature sodium aluminosilicates cages (sodium not shown) that have high affinity for water.
Vials of mesoporous silica MSN vials.JPG
Vials of mesoporous silica

A molecular sieve is a material with pores of uniform size. These pore diameters are similar in size to small molecules, and thus large molecules cannot enter or be adsorbed, while smaller molecules can. As a mixture of molecules migrates through the stationary bed of porous, semi-solid substance referred to as a sieve (or matrix), the components of the highest molecular weight (which are unable to pass into the molecular pores) leave the bed first, followed by successively smaller molecules. Some molecular sieves are used in size-exclusion chromatography, a separation technique that sorts molecules based on their size. Another important use is as a desiccant. Most of molecular sieves are aluminosilicate zeolites with Si/Al molar ratio less than 2, but there are also examples of activated charcoal and silica gel. [1]

Contents

The pore diameter of a molecular sieve is measured in ångströms (Å) or nanometres (nm). According to IUPAC notation, microporous materials have pore diameters of less than 2 nm (20 Å) and macroporous materials have pore diameters of greater than 50 nm (500 Å); the mesoporous category thus lies in the middle with pore diameters between 2 and 50 nm (20–500 Å). [2]

Materials

Molecular sieves can be microporous, mesoporous, or macroporous material.

Microporous material (<2 nm)

Mesoporous material (2–50 nm)

Macroporous material (>50 nm)

Applications

Molecular sieves are often utilized in the petroleum industry, especially for drying gas streams. For example, in the liquid natural gas (LNG) industry, the water content of the gas needs to be reduced to less than 1 ppmv to prevent blockages caused by ice or methane clathrate.

In the laboratory, molecular sieves are used to dry solvent. "Sieves" have proven to be superior to traditional drying techniques, which often employ aggressive desiccants. [7]

Under the term zeolites, molecular sieves are used for a wide range of catalytic applications. They catalyze isomerisation, alkylation, and epoxidation, and are used in large scale industrial processes, including hydrocracking and fluid catalytic cracking. [8]

They are also used in the filtration of air supplies for breathing apparatus, for example those used by scuba divers and firefighters. In such applications, air is supplied by an air compressor and is passed through a cartridge filter which, depending on the application, is filled with molecular sieve and/or activated carbon, finally being used to charge breathing air tanks. [9] Such filtration can remove particulates and compressor exhaust products from the breathing air supply.

Morphology of molecular sieves

Molecular sieve can be mixed with a clay binder and extruded or formed into beads, which allows operators to handle the material more easily than in its power form. Extrudates-pellets-beads-molecular-sieve-hengye-inc.jpg
Molecular sieve can be mixed with a clay binder and extruded or formed into beads, which allows operators to handle the material more easily than in its power form.

Molecular sieves are available in diverse shape and sizes. Molecular sieve can be used directly in its powered form in many applications, such as in insulated glass or coatings. However, to make handling the material more manageable, especially for regenerative processes, molecular sieve powder is commonly mixed with a clay binder material and formed into an extrudate or a bead before being activated. [10]

Originally, the molecular sieve zeolite and clay binder mixture was extruded into a pellet form. While pellets are still commonly used, manufacturers eventually began forming the mixture into a beaded form, which provides more favorable adsorption characteristics. Depending on the process conditions and the size of the process chamber, both extrudates and beads are available in a range of nominal sizes. For example, industrial ethanol dehydration processes use a larger 4x8 mesh bead because the process chambers are large, up to 40 feet tall or more. [11] On the other end, a portable oxygen concentrator uses a smaller bead size, approximately 20x40 mesh, which allows higher output in a smaller vessel size by improving the adsorption/desorption rate of the molecular sieve. [12]

Spherical beads have advantages over other shapes as they offer lower pressure drop, are attrition resistant as they do not have any sharp edges, and have good strength, i.e. crush force required per unit area is higher. Certain beaded molecular sieves offer lower heat capacity thus lower energy requirements during regeneration. The other advantage of using beaded molecular sieves is that bulk density is usually higher than other shapes, thus for a given adsorption requirement, the molecular sieve volume required is less. While de-bottlenecking, one may use beaded molecular sieves to load more adsorbent in the same volume while avoiding vessel modifications. [13]

FDA approval

The U.S. FDA has as of April 1, 2012, approved sodium aluminosilicate for direct contact with consumable items under 21 CFR 182.2727. [14] Prior to this approval the European Union had used molecular sieves with pharmaceuticals and independent testing suggested that molecular sieves meet all government requirements but the industry had been unwilling to fund the expensive testing required for government approval. [15]

Regeneration

Methods for regeneration of molecular sieves include pressure change (as in oxygen concentrators), heating and purging with a carrier gas (as when used in ethanol dehydration), or heating under high vacuum. Regeneration temperatures range from 175 °C (350 °F) to 315 °C (600 °F) depending on molecular sieve type. [16]

Adsorption capabilities

NameAliasPore
diameter
(Ångström)		Bulk
density
(g/mL)		Adsorbed
water
(% w/w)		 Attrition
or abrasion
W
(% w/w)		Usage [17]
3AA-3, K-A30.60–0.6819–200.3–0.6 Desiccation of petroleum cracking gas and alkenes, selective adsorption of H2O in insulated glass (IG) and polyurethane, drying of ethanol fuel for blending with gasoline.
4AA-4, Na-A40.60–0.6520–210.3–0.6Adsorption of water in sodium aluminosilicate which is FDA approved (see below) used as a molecular sieve in medical containers to keep contents dry and as a food additive with E-number E-554 (anti-caking agent); preferred for static dehydration in closed liquid or gas systems, e.g. in packaging of drugs, electric components and perishable chemicals; water scavenging in printing and plastics systems and drying saturated hydrocarbon streams. Adsorbed species include SO2, CO2, H2S, C2H4, C2H6, and C3H6. Generally considered a universal drying agent in polar and nonpolar media; [16] separation of natural gas and alkenes, adsorption of water in non-nitrogen sensitive polyurethane
5A-DW50.45–0.5021–220.3–0.6Degreasing and pour point depression of aviation kerosene and diesel, and alkenes separation
5A small oxygen-enriched50.4–0.8≥23Specially designed for medical or healthy oxygen generator[ citation needed ]
5AA-5, Ca-A50.60–0.6520–210.3–0.5Desiccation and purification of air; dehydration and desulfurization of natural gas and liquid petroleum gas; oxygen and hydrogen production by pressure swing adsorption process
10XF-9, Ca-X80.50–0.6023–240.3–0.6High-efficient sorption, used in desiccation, decarburization, desulfurization of gas and liquids and separation of aromatic hydrocarbon
13XF-9, Na-X100.55–0.6523–240.3–0.5Desiccation, desulfurization and purification of petroleum gas and natural gas
13X-AS100.55–0.6523–240.3–0.5 Decarburization and desiccation in the air separation industry, separation of nitrogen from oxygen in oxygen concentrators
Cu-13XCu-X100.50–0.6023–240.3–0.5 Sweetening (removal of thiols) of aviation fuel and corresponding liquid hydrocarbons

Zeolite

Zeolites are captivating minerals that can either occur naturally or be created synthetically to meet specific industrial needs. The natural formation of zeolite entails a fascinating combination of volcanic activity and groundwater. It originates from volcanic ash interacting with alkaline groundwater over thousands of years, resulting in the creation of porous crystalline structures, endowing this material with unique properties that make it valuable in various industrial processes. The volcanic ash, rich in silica and alumina, acts as the building blocks for the porous structures of molecular sieves. As water percolates through these ash deposits, it gradually dissolves some of the minerals and carries them along. Over time, these dissolved minerals recombine under specific conditions to form the crystalline framework that defines zeolite structures. This natural process gives rise to the remarkable adsorption capabilities that zeolite is renowned for. Owing to its natural structure, zeolite has a high affinity for water molecules, making it particularly useful in applications where water removal is essential, such as gas drying processes. [18]

3A

Production

3A molecular sieves are produced by cation exchange of potassium for sodium in 4A molecular sieves.

Usage

3A molecular sieves do not adsorb molecules whose diameters are larger than 3 Å. The characteristics of these molecular sieves include fast adsorption speed, frequent regeneration ability, good crushing resistance and pollution resistance. These features can improve both the efficiency and lifetime of the sieve. 3A molecular sieves are the necessary desiccant in petroleum and chemical industries for refining oil, polymerization, and chemical gas-liquid depth drying.

3A molecular sieves are used to dry a range of materials, such as ethanol, air, refrigerants, natural gas and unsaturated hydrocarbons. The latter include cracking gas, acetylene, ethylene, propylene and butadiene.

3A molecular sieve is utilized to remove water from ethanol, which can later be used directly as a biofuel or indirectly to produce various products such as chemicals, foods, pharmaceuticals, and more. Due to the formation of an azeotrope at approximately 95.6 percent concentration by weight, normal distillation alone cannot remove all the water (an undesirable byproduct from ethanol production) from ethanol process streams. To break the azeotrope, molecular sieve is used to separate ethanol and water on a molecular level by adsorbing water into the 3A molecular sieve crystal while allowing the ethanol to pass freely. Once the molecular sieve is saturated with water, temperature or pressure can be manipulated to allow water to release from the molecular sieve in a process called regeneration. [19]

3A molecular sieves should be stored at room temperature, with a relative humidity not more than 90%. They are sealed under reduced pressure, being kept away from water, acids and alkalis.

4A

Production

Production of 4A sieve is relatively straightforward as it requires neither high pressures nor particularly high temperatures. Typically, aqueous solutions of sodium silicate and sodium aluminate are combined at 80°C. The solvent-impregnated product is "activated" by "baking" at 400°C. [20]

Relation to 3A and 5A

4A sieves serve as the precursor to 3A and 5A sieves through cation exchange of sodium for potassium (for 3A) or calcium (for 5A). [21] [22] In effect, this ion exchange allows the selectivity of molecular sieve to differentiate where 3A molecular sieve is more selective than 4A molecular sieve while 5A molecular sieve is less selective than 4A molecular sieve and can adsorb larger molecules. [23]

Usage

Drying solvents

4A molecular sieves are widely used to dry laboratory solvents. [7] They can absorb water and other molecules with a critical diameter less than 4 Å such as NH3, H2S, SO2, CO2, C2H5OH, C2H6, and C2H4. They are widely used in the drying, refining and purification of liquids and gases (such as the preparation of argon).

Bottle of 4A molecular sieves 4A sieves.JPG
Bottle of 4A molecular sieves

Polyester agent additives

These molecular sieves are used to assist detergents as they can produce demineralized water through calcium ion exchange, remove and prevent the deposition of dirt. They are widely used to replace phosphorus. The 4A molecular sieve plays a major role to replace sodium tripolyphosphate as detergent auxiliary in order to mitigate the environmental impact of the detergent. It also can be used as a soap forming agent and in toothpaste.

Harmful waste treatment

4A molecular sieves can purify sewage of cationic species such as ammonium ions, Pb2+, Cu2+, Zn2+ and Cd2+. Due to the high selectivity for NH4+ they have been successfully applied in the field to combat eutrophication and other effects in waterways due to excessive ammonium ions. 4A molecular sieves have also been used to remove heavy metal ions present in water due to industrial activities.

Other purposes

  1. The metallurgical industry: separating agent, separation, extraction of brine potassium, rubidium, caesium, etc.
  2. Petrochemical industry, catalyst, desiccant, adsorbent
  3. Agriculture: soil conditioner
  4. Medicine: load silver zeolite antibacterial agent.

5A

Production

5A molecular sieves are produced by cation exchange of calcium for sodium in 4A molecular sieves.

Usage

Five-ångström (5A) molecular sieves are often utilized in the petroleum industry, especially for the purification of gas streams and in the chemistry laboratory for separating compounds and drying reaction starting materials. They contain tiny pores of a precise and uniform size, and are mainly used as an adsorbent for gases and liquids.

Five-ångström molecular sieves are used to dry natural gas, along with performing desulfurization and decarbonation of the gas. They can also be used to separate mixtures of oxygen, nitrogen and hydrogen, and oil-wax n-hydrocarbons from branched and polycyclic hydrocarbons.

Five-ångström molecular sieves are stored at room temperature, with a relative humidity less than 90% in cardboard barrels or carton packaging. The molecular sieves should not be directly exposed to the air and water, acids and alkalis should be avoided.

Type 13X

Type 13X molecular sieve has a different crystalline structure than Type A molecular sieve. 13X-molecular-sieve-hengye-inc.jpg
Type 13X molecular sieve has a different crystalline structure than Type A molecular sieve.

Production

Specialized synthesis methods have been developed to tailor the properties of zeolite for diverse industrial applications. By carefully controlling the chemical composition and reaction conditions, manufacturers can modify the size, shape, and surface properties of zeolite to create synthetic 13X molecular sieve, allowing it to be optimized for specific functions. For air separation processes, carefully synthesized 13X molecular sieve can be engineered to selectively adsorb certain gas molecules while allowing others to pass through, making it invaluable in separating and purifying gases on an industrial scale. [24]

Relation to Type A Molecular Sieve

Type X crystals are shaped differently from Type A crystals are tend to offer much larger pore sizes, about 9 Angstroms in diameter. [25]

Usage

In the natural gas and biogas industries, the presence of impurities such as carbon dioxide and hydrogen sulfide can significantly impact the quality and usability of these valuable resources. 13X zeolite is a key component in removing these impurities. Leveraging its high selectivity for carbon dioxide and hydrogen sulfide, 13X effectively purifies natural gas and biogas, ensuring that these resources meet stringent purity standards for safe utilization. Moreover, in air separation applications, the selective adsorption capabilities of 13X come into play by effectively removing impurities from the air. This is particularly crucial in industries where high-purity gases are essential for various processes. The ability of 13X zeolite to selectively capture water molecules and other impurities contributes to achieving the desired purity levels required for industrial applications. Beyond gas separation and purification, 13X zeolite also serves as an invaluable asset in the drying of various gases and liquids. Its exceptional water adsorption capacity makes it an indispensable tool for removing moisture from industrial processes. Whether it’s the drying of natural gas, biogas, or liquid streams, 13X zeolite plays a critical role in maintaining the purity and integrity of these essential substances. [26]

See also

Related Research Articles

<span class="mw-page-title-main">Zeolite</span> Microporous, aluminosilicate mineral

Zeolite is a family of several microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula Mn+
1/n(AlO
2)−
(SiO
2)
x･yH
2O where Mn+
1/n is either a metal ion or H+. These positive ions can be exchanged for others in a contacting electrolyte solution. H+
 exchanged zeolites are particularly useful as solid acid catalysts.

<span class="mw-page-title-main">Moonshine</span> High-proof distilled spirit, generally produced illicitly

Moonshine is high-proof liquor, traditionally made or distributed illegally. Its clandestine distribution is known as bootlegging. The name was derived from a tradition of creating the alcohol during the nighttime, thereby avoiding detection. In the first decades of the 21st century, commercial distilleries have adopted the term for its outlaw cachet and begun producing their own legally sanctioned, novelty "moonshine", including many flavored varieties, that in some sense continue its tradition, generally having a similar method and/or location of production.

<span class="mw-page-title-main">Adsorption</span> Phenomenon of surface adhesion

Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid. While adsorption does often precede absorption, which involves the transfer of the absorbate into the volume of the absorbent material, alternatively, adsorption is distinctly a surface phenomenon, wherein the adsorbate does not penetrate through the material surface and into the bulk of the adsorbent. The term sorption encompasses both adsorption and absorption, and desorption is the reverse of sorption.

<span class="mw-page-title-main">Silica gel</span> Chemical compound

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel.

<span class="mw-page-title-main">Desiccant</span> Substance used to induce or sustain dryness

A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccants for specialized purposes may be in forms other than solid, and may work through other principles, such as chemical bonding of water molecules. They are commonly encountered in foods to retain crispness. Industrially, desiccants are widely used to control the level of water in gas streams.

<span class="mw-page-title-main">Activated alumina</span>

Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material; this material can have a surface area significantly over 200 m2/g. The compound is used as a desiccant (to keep things dry by adsorbing water from the air) and as a filter of fluoride, arsenic and selenium in drinking water. It is made of aluminium oxide (alumina; Al2O3). It has a very high surface-area-to-weight ratio, due to the many "tunnel like" pores that it has. Activated alumina in its phase composition can be represented only by metastable forms (gamma-Al2O3 etc.). Corundum (alpha-Al2O3), the only stable form of aluminum oxide, does not have such a chemically active surface and is not used as a sorbent.

<span class="mw-page-title-main">Sodium aluminate</span> Chemical compound

Sodium aluminate is an inorganic chemical that is used as an effective source of aluminium hydroxide for many industrial and technical applications. Pure sodium aluminate (anhydrous) is a white crystalline solid having a formula variously given as NaAlO2, NaAl(OH)4 (hydrated), Na2O·Al2O3, or Na2Al2O4. Commercial sodium aluminate is available as a solution or a solid.
Other related compounds, sometimes called sodium aluminate, prepared by reaction of Na2O and Al2O3 are Na5AlO4 which contains discrete AlO45− anions, Na7Al3O8 and Na17Al5O16 which contain complex polymeric anions, and NaAl11O17, once mistakenly believed to be β-alumina, a phase of aluminium oxide.

Rectified spirit, also known as neutral spirits, rectified alcohol or ethyl alcohol of agricultural origin, is highly concentrated ethanol that has been purified by means of repeated distillation in a process called rectification. In some countries, denatured alcohol or denatured rectified spirit may commonly be available as "rectified spirit", because in some countries the retail sale of rectified alcohol in its non-denatured form is prohibited.

Sodium aluminosilicate refers to compounds which contain sodium, aluminium, silicon and oxygen, and which may also contain water. These include synthetic amorphous sodium aluminosilicate, a few naturally occurring minerals and synthetic zeolites. Synthetic amorphous sodium aluminosilicate is widely used as a food additive, E 554.

<span class="mw-page-title-main">Pressure swing adsorption</span> Method of gases separation using selective adsorption under pressure

Pressure swing adsorption (PSA) is a technique used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material. It operates at near-ambient temperature and significantly differs from the cryogenic distillation commonly used to separate gases. Selective adsorbent materials are used as trapping material, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorb the adsorbed gas.

<span class="mw-page-title-main">Sorbent</span> Material that absorbs or adsorbs

A sorbent is a material that either absorbs or adsorbs liquids or gases.

<span class="mw-page-title-main">Nanoporous materials</span>

Nanoporous materials consist of a regular organic or inorganic bulk phase in which a porous structure is present. Nanoporous materials exhibit pore diameters that are most appropriately quantified using units of nanometers. The diameter of pores in nanoporous materials is thus typically 100 nanometers or smaller. Pores may be open or closed, and pore connectivity and void fraction vary considerably, as with other porous materials. Open pores are pores that connect to the surface of the material whereas closed pores are pockets of void space within a bulk material. Open pores are useful for molecular separation techniques, adsorption, and catalysis studies. Closed pores are mainly used in thermal insulators and for structural applications.

Mesoporous silicates are silicates with a special morphology.

<span class="mw-page-title-main">Mesoporous silica</span> Nano-scale porous silica compound

Mesoporous silica is a form of silica that is characterised by its mesoporous structure, that is, having pores that range from 2 nm to 50 nm in diameter. According to IUPAC's terminology, mesoporosity sits between microporous (<2 nm) and macroporous (>50 nm). Mesoporous silica is a relatively recent development in nanotechnology. The most common types of mesoporous nanoparticles are MCM-41 and SBA-15. Research continues on the particles, which have applications in catalysis, drug delivery and imaging. Mesoporous ordered silica films have been also obtained with different pore topologies.

<span class="mw-page-title-main">Zeolitic imidazolate framework</span> Class of metal-organic frameworks

Zeolitic imidazolate frameworks (ZIFs) are a class of metal-organic frameworks (MOFs) that are topologically isomorphic with zeolites. ZIF glasses can be synthesized by the melt-quench method, and the first melt-quenched ZIF glass was firstly made and reported by Bennett et al. back in 2015. ZIFs are composed of tetrahedrally-coordinated transition metal ions connected by imidazolate linkers. Since the metal-imidazole-metal angle is similar to the 145° Si-O-Si angle in zeolites, ZIFs have zeolite-like topologies. As of 2010, 105 ZIF topologies have been reported in the literature. Due to their robust porosity, resistance to thermal changes, and chemical stability, ZIFs are being investigated for applications such as carbon dioxide capture.

<span class="mw-page-title-main">ZSM-5</span> Zeolite used as a catalyst in oil refining

ZSM-5, Zeolite Socony Mobil–5 (framework type MFI from ZSM-5 (five)), is an aluminosilicate zeolite belonging to the pentasil family of zeolites. Its chemical formula is NanAlnSi96–nO192·16H2O (0<n<27). Patented by Mobil Oil Company in 1975, it is widely used in the petroleum industry as a heterogeneous catalyst for hydrocarbon isomerization reactions.

<span class="mw-page-title-main">SSZ-13</span>

SSZ-13 (framework type code CHA) is a high-silica aluminosilicate zeolite possessing 0.38 × 0.38 nm micropores. It belongs to the ABC-6 family of zeolites as well as offretite, cancrinite, erionite and other related small-pore zeolites. The framework topology is the same as that of chabazite but SSZ-13 has a high silica composition with Si/Al > 5, which leads to low cation exchange capacity. The typical chemical formula of the unit cell can be described as QxNayAl2.4Si33.6O72•zH2O (1.4 < x <27)(0.7 < y < 4.3)(1 < z <7), where Q is N,N,N-1-trimethyladamantammonium. The material was patented by Chevron research Company in 1985, and could potentially be used as a solid catalyst for the methanol-to-olefins (MTO) process and the selective catalytic reduction (SCR) of NOx.

Mesoporous organosilica are a type of silica containing organic groups that give rise to mesoporosity. They exhibit pore size ranging from 2 nm - 50 nm, depending on the organic substituents. In contrast, zeolites exhibit pore sizes less than a nanometer. PMOs have potential applications as catalysts, adsorbents, trapping agents, drug delivery agents, stationary phases in chromatography and chemical sensors.

A zeolite membrane is a synthetic membrane made of crystalline aluminosilicate materials, typically aluminum, silicon, and oxygen with positive counterions such as Na+ and Ca2+ within the structure. Zeolite membranes serve as a low energy separation method. They have recently drawn interest due to their high chemical and thermal stability, and their high selectivity. Currently zeolites have seen applications in gas separation, membrane reactors, water desalination, and solid state batteries. Currently zeolite membranes have yet to be widely implemented commercially due to key issues including low flux, high cost of production, and defects in the crystal structure.

References

  1. ↑ "Molecular Sieve Definition - Definition of Molecular Sieve - What Is a Molecular Sieve?". Chemistry.about.com. 2013-12-18. Archived from the original on 2014-02-21. Retrieved 2014-02-26.
  2. ↑ J. Rouquerol; et al. (1994). "Recommendations for the characterization of porous solids (Technical Report)" (free download pdf). Pure Appl. Chem. 66 (8): 1739–1758. doi: 10.1351/pac199466081739 . S2CID   18789898.
  3. ↑ "Coated Molecular Sieve – Patent application". Faqs.org. 2010-03-18. Retrieved 2014-02-26.
  4. ↑ Brindley, George W. (1952). "Structural mineralogy of clays". Clays and Clay Minerals. 1 (1): 33–43. Bibcode:1952CCM.....1...33B. doi: 10.1346/CCMN.1952.0010105 .
  5. ↑ "Desiccant Types". SorbentSystems.com. Retrieved 2014-02-26.
  6. ↑ Mann, B. F.; Mann, A. K. P.; Skrabalak, S. E.; Novotny, M. V. (2013). "Sub 2-μm Macroporous Silica Particles Derivatized for Enhanced Lectin Affinity Enrichment of Glycoproteins". Analytical Chemistry. 85 (3): 1905–1912. doi:10.1021/ac303274w. PMC   3586544 . PMID   23278114.
  7. 1 2 Williams, D. B. G., Lawton, M., "Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants", The Journal of Organic Chemistry 2010, vol. 75, 8351. doi : 10.1021/jo101589h
  8. ↑ Pujadó, P. R.; Rabó, J. A.; Antos, G. J.; Gembicki, S. A. (1992-03-11). "Industrial catalytic applications of molecular sieves". Catalysis Today. 13 (1): 113–141. doi:10.1016/0920-5861(92)80191-O.
  9. ↑ Archived April 16, 2012, at the Wayback Machine
  10. ↑ "Regenerating Adsorbents". www.hengyeinc.com. Hengye Inc. 21 January 2020. Retrieved 23 May 2024.
  11. ↑ Binns, Mark (12 June 2017). "How Not to Kill the Molecular Sieve". Ethanol Producer Magazine. Retrieved 23 May 2024.
  12. ↑ "Molecular Sieve for Oxygen Concentrator". www.hengyeinc.com. Hengye Inc. 19 February 2024. Retrieved 23 May 2024.
  13. ↑ Burkes, Kolten (28 February 2018). "Does Size Really Matter?". www.hengyeinc.com. Hengye Inc. Retrieved 23 May 2024.
  14. ↑ "Sec. 182.2727 Sodium aluminosilicate". U.S. Food and Drug Administration. 1 April 2012. Retrieved 10 December 2012.
  15. ↑ "Molecular Sieve Desiccant". DesiccantPacks.net. Retrieved 2014-02-26.
  16. 1 2 "Molecular Sieves". Sigma-Aldrich . Retrieved 2014-02-26.
  17. ↑ "Molecular Sieve, Yiyuan Molecular Sieves". Chemicalpackingcorp.com. Retrieved 2014-02-26.
  18. ↑ "13X Zeolite - Uncovering Its Versatile Uses, Applications and Benefits". www.hengyeinc.com. 30 January 2024. Retrieved 23 May 2024.
  19. ↑ Binns, Mark; Burkes, Kolten (September–October 2017). "Removing Water from Ethanol". Biofuels International. 11 (5): 38–39. Retrieved 10 July 2015.
  20. ↑ US 3433588,Max Michel&Denis Papee,"Method for the preparation of 4 angstrom unit zeolites",published 1969-03-18,issued 1969-03-18
  21. ↑ Zeochem
  22. ↑ Intraglobal
  23. ↑ Burkes, Kolten (20 July 2017). "3A, 4A, 5A, 13X... What's the Difference?". Hengye Inc. Retrieved 22 May 2024.
  24. ↑ "13X Zeolite - Uncovering Its Versatile Uses, Applications and Benefits". www.hengyeinc.com. 30 January 2024. Retrieved 23 May 2024.
  25. ↑ Burkes, Kolten (20 July 2017). "3A, 4A, 5A, 13X... What's the Difference". www.hengyeinc.com. Retrieved 23 May 2024.
  26. ↑ "13X Zeolite - Uncovering Its Versatile Uses, Applications and Benefits". www.hengyeinc.com. 30 January 2024. Retrieved 23 May 2024.
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