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The new crown pneumonia epidemic struck, ECMO has repeatedly appeared in emergency scenes and entered the public eye.
ECMO is an extracorporeal membrane oxygenation therapy device, commonly known as "artificial lung".
ECMO is currently the core support method for severe cardiopulmonary failure.
It is known as The "last straw" for critically ill patients with new coronary pneumonia
.
ECMO membrane lung
Membrane lung is the core component of ECMO system and undertakes the function of blood oxygenation.
At present, membrane lung materials mainly use PMP (poly4-methyl 1-pentene) hollow fiber membrane, membrane-forming resin PMP (poly4-methyl 1-pentene) -Pentene) is first obtained by propylene dimerization to obtain 4-methyl-1-pentene (4MP1) monomer polymerization, and propylene dimerization has not been industrialized in China so far
.
Alkali metal catalysis is the main method for propylene dimerization
Alkali metal catalysis is the main method for propylene dimerizationIn the 1960s, after BP built the world's first 4-methyl-1-pentene production unit with a scale of 2,000 tons per year, Japan, the former Soviet Union and the United States successively built 20,000 to 100,000 tons per year.
production equipment
.
Dimerization of propylene under the catalysis of alkali metal catalysts supported on anhydrous K2CO3 carriers is almost the only way to obtain 4-methyl-1-pentene (4MP1) in industry at present.
Catalyst, some other components are added to the carrier, so that the strength, activity and life of the catalyst are improved.
The metal carbonate is used as the carrier, supplemented by graphite, and the pore expander is introduced, and the composite metal is used as the active group.
It can improve catalyst activity, selectivity, strength and life
.
4-methyl-1-pentene (4MP1) process flow chart
The new solid super base K/K2CO3 catalyzes the dimerization of propylene into 4-methyl-1-pentene (4MP1).
The conversion rate of propylene is 43%, the selectivity of the dimerization product is 95%, and the selectivity of 4MP1 is 86%
.
Reaction mechanism of propylene dimerization to 4MP1
Reaction mechanism of propylene dimerization to 4MP1The currently recognized reaction mechanism of the alkali metal system catalyzing the dimerization of propylene into 4MP1 is that propylene enters the super base site of the catalyst through diffusion, is abstracted by proton and combines with the alkali metal on the surface of the catalyst to form an active active intermediate-allyl anion, propylene The π electrons on the molecular double bond are not uniformly distributed on the α and β carbons, and the electron cloud density on the β carbon connected to the methyl group is small.
Under the reaction conditions, the allyl anion easily reacts with the β carbon with a methyl group The unstable 4MP1 anion is generated, and the 4MP1 anion will continue to undergo a hydrogen exchange reaction with the propylene molecule to generate a more stable allyl anion and the target product, forming a cyclic catalytic process
.
4-Methyl-1-pentene product quality index
Inhibits dimerization side reactions
Inhibits dimerization side reactionsTwo types of side reactions are mainly involved in the reaction process in which the catalyst catalyzes the dimerization of propylene into 4MP1, one is the oligomerization side reaction, and the other is the isomerization side reaction
.
The main reaction of solid base-catalyzed propylene dimerization has a high selectivity to 4MP1.
The main factor affecting the selectivity of the final reaction product 4MP1 is the isomerization of 4MP1 during the reaction process.
To reduce the side effects of propylene dimerization to 4MP1 For the reaction, it is necessary to speed up the desorption rate of the product from the active site of the catalyst.
K2CO3 has a lower specific surface area and a simple pore structure.
The alkali metal supported on K2CO3 is an excellent catalyst for the synthesis of 4MP1 for dimerization of propylene, and has a relatively low specific surface area and simple pore structure.
For the low isomerization activity, the optimization of the catalyst with K2CO3 as a carrier is to improve its pore structure and increase its pore size, so that it has no effect on the isomerization activity on the basis of improving the conversion effect
.
A product chain has become a country's obvious injury
A product chain has become a country's obvious injuryPropylene dimer 4-methyl-1-pentene (4MP1) is further polymerized under the action of "Ziegler-Natta" catalyst to form PMP resin, PMP (poly4-methylpentene-1) resin It was first developed by the British ICI company in 1965, and began commercial mass production in 1968.
Japan's Mitsui Chemicals Co.
, Ltd.
obtained the authorization of ICI, and began production and entered the market in 1973.
At present, Japan's Mitsui Chemicals Co.
, Ltd.
is a The only PMP resin manufacturer in the world, PMP hollow fiber membranes are currently only manufactured and supplied exclusively by Membrana, a subsidiary of 3M Company.
Therefore, the entire product chain of propylene dimer 4MP1-PMP resin-PMP membrane cannot be produced independently, which restricts the production of PMP hollow fiber membranes.
Localization of ECMO
.
Since all ECMOs rely on imports, there are only about 400 units in the country.
After the outbreak of the new crown pneumonia in Hubei, the demand for "artificial lungs" has increased The equipment supports Hubei.
On February 27, 16 ECMOs were urgently imported from Frankfurt, Germany and transported to Wuhan, Hubei.
The most expensive consumables in use are membrane lungs, that is, membrane lung materials PMP hollow fiber membranes
.
The outbreak of the new crown pneumonia has made the propylene dimer 4MP1-PMP resin-PMP hollow fiber membrane independent, from a hidden worry in an industry chain to a country's obvious injury
.
The foundation of not being "stuck in the neck" is the ability to deal with the worst situation at any time!
