abstract
Carbon dioxide is a common compound in the air, and its molecular formula is co? It is formed by connecting two oxygen atoms with a carbon atom through a valence bond * * *. At room temperature, it is a colorless and odorless gas with a density slightly higher than that of air, which can be dissolved in water and produce carbonic acid. Solid carbon dioxide is usually called dry ice. Carbon dioxide is considered as the main source of the greenhouse effect.
Basic information of carbon dioxide
brief introduction
Two. 2. 10 carbon dioxide (CO? )
English name carbon dioxide
Alias carbonic acid gas
Si Nuo. 124-38-9
EINECSno。 204-696-9
InChI code inchi =1/CO2/C2-1-3.
Molecular weight 44
* * * has three nuclei and 22 protons.
The relative molecular mass is 48.
structure
C atoms form δ bonds with sp hybrid orbitals. The molecular shape is linear. Nonpolar molecules. At CO? In molecules, carbon atoms combine with oxygen atoms through sp hybrid orbitals. The two sp hybrid orbitals of C atom form two σ bonds with two O atoms respectively. The two unhybridized P orbitals on the C atom are at right angles to the sp hybrid orbitals, and overlap with the P orbitals of the oxygen atom side by side, respectively, forming two delocalized bonds with three centers and four electrons. Therefore, the distance between carbon atoms and oxygen atoms is shortened, CO? Carbon-oxygen bond has a certain degree of triple bond characteristics. What determines the shape of the molecule is the sp hybrid orbital, CO? It is a linear molecule. Carbon dioxide is denser than air.
Gas state
Relative Molecular Mass Melting Point (Celsius) Boiling Point (Celsius)
44.0 1 -78.48 (sublimation) -56.6(5270 Pa)
Role dissolution
Colorless and odorless gas. It can be dissolved in water at room temperature and partially generates carbonic acid.
Soluble in water (volume ratio 1: 1) to generate carbonic acid.
Relative density of structural formula
O=C=O CO？ Relative density1.101(-37℃)
liquid condition
Surface tension: about 3.0dyn/cm.
Density: 0.8g/cm3
Viscosity: much lower than tetrachloroethylene, so liquid carbon dioxide can penetrate the fiber more. )
The molecular structure of carbon dioxide is very stable, its chemical properties are not active, and it will not react with fabrics.
Low boiling point (-78.5℃), gas at normal temperature and pressure.
Features: no flash point, nonflammable; Colorless, tasteless and nontoxic.
Liquid carbon dioxide is converted into gas by decompression, which can be easily separated from fabric, completely eliminating the complicated post-treatment process brought by traditional solvents.
Liquid CO? And supercritical CO? Can be used as a solvent, although supercritical CO? Compared with liquid CO? Higher solubility (close to the density and high solubility of liquid, low viscosity and high permeability of gas). But it needs more equipment than liquid CO? Tall man. Considering the machine cost and co? As a solvent, the temperature is controlled at about 65438 05℃ and the pressure is about 5MPa.
solid state
Liquid carbon dioxide absorbs a lot of heat when it evaporates; When it absorbs a lot of heat, it will condense into solid carbon dioxide, commonly known as dry ice.
Dry ice is widely used in food, sanitation, industry and catering. Mainly includes:
1. Application scope of dry ice in industrial molds
Tire mold, rubber mold, polyurethane mold, polyethylene mold, PET mold, foaming mold, injection mold, alloy die-casting mold, hot core box for casting and cold core box can remove residual resin, invalid release layer, carbonizing film agent and oil stain, and can open air holes. After cleaning, the mold is as bright as new.
On-line cleaning does not need to cool and disassemble the mold, which avoids the corrosion and damage of the mold by chemical cleaning method, the mechanical damage and scratch of the mold by mechanical cleaning method, and the decline of mold accuracy caused by repeated loading and unloading. Crucially, the two most time-consuming steps of removing the mold and waiting for the mold to cool can be omitted, and the downtime can be reduced by about 80%-95%.
Benefits of dry ice cleaning: dry ice cleaning can reduce downtime; Reduce equipment damage; Very effective cleaning of high-temperature equipment; Reduce or reduce the use of solvents; Improving the safety of staff; Improve maintenance efficiency; Reduce production downtime, reduce costs and improve production efficiency.
2. Application scope of dry ice in petrochemical industry
Clean the main fan, air compressor, fume hood, steam turbine, blower and other equipment to remove coking and carbon deposition in various heating furnaces and reactors. Clean the PVC resin on the heat exchanger; Remove oil stains, rust, hydrocarbons and dirt on the surfaces of various pressure vessels such as compressors, storage tanks and boilers; Cleaning the reaction kettle and condenser; Complex biological purification; Furnace tube cleaning, etc.
3. Application scope of dry ice in food and pharmaceutical industries
It can successfully remove baking residues, colloidal substances and oil stains in the oven, as well as the mixture of fresh products before baking. Effectively clean ovens, mixing and stirring equipment, conveyor belts, molded products, packaging equipment, stoves, stoves, containers, rollers, refrigerator inner walls, biscuit stoves, etc.
Benefits of dry ice cleaning: put an end to the use of harmful chemicals, and avoid production equipment contacting with harmful chemicals and generating secondary garbage; Prepare or remove bacteria such as Salmonella and Listeria, and disinfect and clean more thoroughly; Eliminate the damage of water jet cleaning to electronic equipment; Minimum equipment decomposition; Reduce downtime.
4. Application scope of dry ice in printing industry
It is difficult to remove ink, and the accumulation of ink on gears and guide rails will lead to poor printing quality. Dry ice cleaning can remove all kinds of oil-based and water-based inks and varnishes, clean up oil stains, accumulated inks and dyes on gears, guide rails and nozzles, and avoid the discharge of harmful wastes and solutions and personal injuries caused by harmful solvents.
5. Application scope of dry ice in electric power industry
Can clean electric boilers, condensers and various heat exchangers; Can directly clean indoor and outdoor transformers, insulators, power distribution cabinets, live wires and cables (below 37KV); Generator, motor, rotor, stator and other parts are clean and free from damage; Clean the rust, hydrocarbon and adhesive powder on turbines, impellers, blades and other parts, without disassembling the blades and readjusting the dynamic balance of the blades.
Benefits of dry ice cleaning: effectively decompose pollutants to be cleaned; Because these pollutants are removed, the power loss is reduced; The maintenance cost of external equipment and its basic equipment is reduced; Improve the reliability of power system; Keep the insulator intact and non-abrasive clean; More suitable for preventive maintenance.
6. Application scope of dry ice in automobile industry
Cleaning the doorskin, roof, carriage, car bottom and other oil stains will not cause water pollution; Cleaning of automobile carburetor and removal of automobile surface paint; Remove carbon deposits from the engine. If the carbon deposit is treated, it will take a long time to treat it with chemical agents, at least more than 48 hours, which is harmful to human body. Dry ice cleaning can completely solve the problem of carbon deposition within 10 minute, saving time and reducing cost, and the scale removal rate reaches 100%.
7. Application scope of dry ice in electronic industry
Clean the grease and dirt inside robots and automation equipment; Clean the integrated circuit board, post-welding flux, pollution coating, resin, solvent coating, protective layer and photosensitive corrosion inhibitor on the printed circuit board.
8. Application scope of dry ice in aerospace
Pre-coating treatment and final assembly of missiles and aircraft; Paint removal of composite molds and special aircraft: engine carbon cleaning; Maintenance and cleaning (especially the landing gear-wheel well area); Depainting of aircraft shells: jet engine conversion system. Can work directly in the body, saving time.
9. Application scope of dry ice in shipbuilding industry
Hull; Seawater suction valve; Seawater condenser and heat exchanger; The machine room, machinery and electrical equipment are cleaner than ordinary high-pressure water jet cleaning.
10, application scope of dry ice in nuclear industry
If the nuclear industry equipment is cleaned by traditional cleaning methods such as water, sand blasting or chemical detergent, the media such as water, sand blasting or chemical detergent will also be polluted by radioactive elements, so it takes time and money to treat these secondary polluted media. In the process of dry ice cleaning, dry ice particles are directly sprayed on the object to be cleaned, which instantly sublimates, and there is no problem of secondary pollution. All that needs to be treated is the cleaned waste with nuclear pollution and scale.
1 1. Application scope of dry ice in beauty industry
Some dermatologists use dry ice to treat acne, which is called cryotherapy. Because it will slightly freeze the skin.
There is a frozen substance for treating acne, which is made of ground dry ice and ethyl ketone, and sometimes some sulfur is added. Liquid nitrogen and solid dry ice can also be used as cryotherapy materials. Cryotherapy can reduce inflammation. Some time ago, the news reported that Liu Xiang used this cryotherapy to treat acne on his face. This method can reduce the generation of acne scars, but it is not used to remove scars.
12, Application scope of dry ice in food industry
A adding dry ice to wine, cocktail or beverage is cool and delicious when drinking, and the cup is full of smoke, which is very pleasant.
B when making ice cream, dry ice is added, and the ice cream is not easy to melt. Dry ice is especially suitable for cold storage of takeaway ice cream.
Seafood dishes made in C-star hotels and restaurants, with dry ice, can create a white smoke landscape and improve the banquet level, such as making lobster sashimi.
D lobster, crab, shark fin and other seafood are frozen and refrigerated. Dry ice will not change water, and it is cleaner than water-cooled storage. Widely used in Europe, America, Japan and other countries.
13, Application scope of dry ice in refrigerated transportation field
Cryopreservation and transportation of special drugs for medical use, such as plasma and vaccines.
B. Long-distance and short-distance transportation of electronic cryogenic materials and precision parts.
C. preservation and transportation of high-grade foods such as high-grade beef and mutton.
14, Application scope of dry ice in entertainment field
Widely used in stage, theater, film and television, wedding, celebration, party effect and so on. For example, some programs in the National Theatre are made of dry ice.
15, application scope of dry ice in fire protection industry
Dry ice is used for fire fighting, such as some low-temperature fire extinguishers, but the application of dry ice in this respect is less, that is, the market level is low;
Precautions for using dry ice:
Remember to be careful every time you touch dry ice. Touch dry ice with thick cotton gloves or other shelter! If it is in direct contact with the skin for a long time, it may cause cell freezing and similar minor or extremely serious burns. Dry ice cannot be used in cars, cabins and other places, because sublimated carbon dioxide will replace oxygen, which may lead to shortness of breath or even suffocation!
1. Never let children touch dry ice alone!
2. The temperature of dry ice is extremely low, please don't put it in your mouth to prevent frostbite!
3. When taking dry ice, be sure to use thick cotton gloves, clips and other shelter (plastic gloves have no shelter! )
4. Please use dry ice in a well-ventilated place and avoid in a closed space with dry ice!
5. Dry ice cannot be mixed with liquid.
Basic attribute
One of carbon oxides is an inorganic substance, which is a colorless and odorless gas at room temperature. Its density is slightly higher than that of air, and it can be dissolved in water to generate carbonic acid. (The basic principle of carbonated drinks) can make clear limewater turbid, which can be used in the experiment of producing carbon dioxide by products of respiration.
Preparation or source
Carbon can be used in excess air or marble, limestone and dolomite (mainly CaCO? ) calcination or reaction with acid. It is a by-product of industries such as lime and fermentation.
The use of carbon dioxide
Gaseous carbon dioxide is used in alkali industry, sugar industry, quenching of steel castings and manufacturing of lead white.
Carbon dioxide is widely used in welding field.
For example, carbon dioxide gas shielded welding is the most widely used method in production.
Solid carbon dioxide, commonly known as dry ice, can absorb a lot of heat when sublimating, so it is used as a refrigerant, such as artificial rainfall, and is often used to make smoke on the stage. Carbon dioxide generally does not burn and does not support combustion. Its density is slightly higher than that of air at room temperature, and it will gather on it when heated and expanded. It is also commonly used as a fire extinguishing agent, but it cannot be used when burning magnesium, sodium and potassium. Put out the fire because: 2Mg+CO? = = Ignition == 2MgO+C, 4Na+CO? = = Ignition ==2Na? O + C、4K + CO？ = = Ignition == 2K? O + C .
Carbon dioxide is an indispensable raw material for photosynthesis of green plants and is often used as fertilizer in greenhouses. Total reaction of photosynthesis: CO? + H？ O- chloroplast, illumination → C6H 12O6+O? Note: The oxygen released by photosynthesis comes from water, and the products of photosynthesis are not only sugar, but also amino acids (excluding protein) and fats, so the products of photosynthesis should be organic.
Reaction at each step: 2H? O- illumination → 2[H+]+O? (Photolytic water) NADP++2e-+H+ → NADPH (hydrogen transfer) ADP+Pi —→ ATP (energy transfer) CO? +C5 compound →C6 compound (carbon dioxide fixation) C6 compound -—ATP, NADPH→(CH? O)n+C5 compound (formation of organic matter)
The density of liquid carbon dioxide is 1. 1g/cm3. Liquid carbon dioxide can be condensed into solid carbon dioxide when it is evaporated or cooled under pressure, commonly known as dry ice, which is a low-temperature refrigerant with a density of 1.56g/cm3. Carbon dioxide can be dissolved in water. At 20℃, 88 volumes of carbon dioxide can be dissolved per 100 volume of water, and some of them react with water to generate carbonic acid. Chemically stable, non-flammable, generally does not support combustion, but active metals can burn in carbon dioxide, such as ignited magnesium rods can burn in carbon dioxide to generate magnesium oxide and carbon. Carbon dioxide is an acidic oxide, which can react with alkali or alkaline oxide to form carbonate. React with ammonia water to generate ammonium bicarbonate. Non-toxic, but when the carbon dioxide content in the air is too high, it will also make people suffocate due to lack of oxygen. Green plants can synthesize organic matter from carbon dioxide and water under photosynthesis. Carbon dioxide can be used to make ammonium bicarbonate, baking soda, soda ash, urea, lead white pigment, beverages, fire extinguishers and quenching steel castings. Carbon dioxide accounts for about 0.03% of the total volume in the atmosphere, and carbon dioxide accounts for about 4% in the gas exhaled by people. In the laboratory, hydrochloric acid reacts with marble to produce carbon dioxide. In industry, carbon dioxide is obtained from the fermentation gas of calcined limestone or wine making.
Generation of carbon dioxide
(1) All organic matter (including animals and plants) can release CO during decomposition, fermentation, decay and deterioration. .
(2) During the combustion of petroleum, paraffin, coal and natural gas, carbon monoxide should also be released? .
(3) In the process of producing chemical products, oil and coal will also release CO? .
(4) All feces and humic acid can also release CO during fermentation and maturation. .
(5) All animals breathe oxygen and spit out CO? .
(6) All green plants absorb carbon monoxide? Oxygen is released for photosynthesis. CO？ Gas, in this way, circulates silently in the natural ecological balance.
Preparation method of carbon dioxide
Industrial law
Calcined limestone at high temperature
CaCO？ = = high temperature == CaO+CO? ↑
Laboratory preparation method
When marble or limestone reacts with hydrochloric acid, it is usually necessary to remove impurities and dry the gas. Hydrochloric acid will volatilize hydrogen chloride (HCl) gas, so saturated sodium bicarbonate (NaHCO? ) a solution that removes hydrogen chloride from a gas. The reaction in the solution will bring out water vapor when the gas overflows, so it is strictly required or necessary to dry the gas. Generally, a washing tank filled with concentrated sulfuric acid is used.
CaCO？ + 2HCl ==== CaCl？ + H？ O + CO？ ↑
In addition, sodium carbonate and hydrochloric acid can not be used for preparation, because the reaction speed is too fast and it is not easy to collect; Calcium carbonate can't react with concentrated hydrochloric acid, because concentrated hydrochloric acid volatilizes a lot of hydrogen chloride gas, so that sodium bicarbonate can't be completely removed, and the purity of the prepared carbon dioxide will be reduced; Nor can it be collected by the reaction of calcium carbonate with dilute sulfuric acid, because the reaction will produce insoluble calcium sulfate, and sulfate radicals will adhere to the surface of calcium carbonate, which will hinder the contact between calcium carbonate and acid and affect the continuation of the reaction.
Folk legal system
Sodium bicarbonate reacts with white vinegar.
NaHCO？ + CH？ COOH ==== CH？ COONa + H？ O + CO？ ↑
Carbon dioxide fertilizer
In a certain range, the higher the concentration of carbon dioxide, the stronger the photosynthesis of plants, so carbon dioxide is the best gas fertilizer. On a farm in New Jersey, American scientists have done a lot of experimental research on different crops at different growth stages with carbon dioxide. They found that carbon dioxide is most effective when used in the vigorous growth and maturity of crops. During these two periods, if carbon dioxide gas is sprayed twice a week for 4-5 times, the yield of vegetables, rice, soybeans and sorghum can be increased by 90%, 70%, 60% and 200% respectively.
The prospect of gas fertilizer is bright, but it is difficult for scientists to determine how much carbon dioxide each crop absorbs to achieve the best effect. Besides carbon dioxide, can other gases be used as gas fertilizer?
Recently, the German geologist Ehrenster discovered that plants are particularly flourishing wherever natural gas comes out of the ground. So he sent liquefied natural gas into the soil through a special pipeline. As a result, this special gas fertilizer has been effective for two years. It turned out that methane gas, the main component of natural gas, played a role. Methane is used to help the reproduction of soil microorganisms, improve soil structure and help plants fully absorb nutrients.
Polycarbonate carbon dioxide
A new synthetic material is under study. After being highly activated by bimetallic coordination PBM catalyst, carbon dioxide reacts with epoxide to produce aliphatic polycarbonate (PPC), and carbon dioxide resin material is obtained after post-treatment. Carbon dioxide resins with different chemical structures can be obtained by adding other reactants in polymerization. Carbon dioxide polymer has flexible molecular chains, and its properties can be easily adjusted by changing its chemical structure. It is easy to decompose under the action of heat, catalyst or microorganism, but it can also be controlled by certain measures: low permeability to oxygen and other gases. The following products can be developed: 1. Polyurethane materials prepared from aliphatic polycarbonate and polyisocyanate have better hydrolysis resistance than ordinary polyester polyurethane. 2. Ternary polymerization with maleic anhydride as the third monomer; The product is unsaturated resin containing carbonate group and ester group, which can be crosslinked and cured, and can also be compounded with fibers and other solids. It is a new material similar to ordinary unsaturated polyester. 3. Aliphatic polycarbonate can be mixed with various polymers to obtain various properties. It can be used as toughening agent, plasticizer or processing aid for epoxy resin and PVC plastics. 4. The polymer of carbon dioxide and ethylene oxide, and the terpolymer of carbon dioxide, propylene oxide and succinic anhydride can be completely decomposed by microorganisms, leaving no residue, which is a promising biodegradable material. 5. Carbon dioxide polymer has excellent biocompatibility. Specially designed * * * polymers are expected to be used as anticoagulant materials or drug sustained-release agents. 6. Some carbon dioxide polymers can be used as surface treatment agents for solid pigments or fillers, oxygen barrier materials, surfactants, ceramic adhesives, hot melt adhesives, etc. 7. The mixture of polypropylene carbonate and nitrile rubber * * * has good oil resistance, thermal oxidation resistance and aging resistance, and its mechanical properties are better than ordinary nitrile rubber, so it is an excellent new oil-resistant rubber. The cost per ton of carbon dioxide resin in this project is about the raw material price of propylene oxide, which is equivalent to 3-30% of foreign technology, and it has great development opportunities abroad. The cost. Compared with pure NBR, PPC/NBR oil-resistant rubber can be reduced by about 10%, and the cost per ton of product can be reduced by more than 1000 yuan.
Other attributes
Carbon dioxide is colorless, slightly irritating and slightly sour at normal temperature and pressure. CO？ The molecule has 16 valence electrons, and its ground state is linear, belonging to D∞h point group. CO？ The bond length of carbon-oxygen bond in the molecule is 1 16pm, which is between carbon-oxygen double bond (the bond length of C=O in acetaldehyde is 124pm) and carbon-oxygen triple bond (the bond length of C≡O in CO molecule is 1 12.8pm). Therefore, some people think that in CO? There may be delocalized large π bonds in the molecule, that is, two large π bonds with three centers and four electrons are formed in addition to oxygen atoms in carbon atoms.
1At the beginning of the 7th century, the Belgian chemist J.B. van Helmont (1577 ~ 1644) discovered carbon dioxide when detecting the by-product gas in the process of charcoal combustion and fermentation. 1757, J. Black was the first to study this gas by quantitative method. 1773, lavoisier heated carbon in oxygen to obtain what he called "carbonic acid". The measured mass composition is 23.5~28.9% of carbon and 7 1. 1~76.5% of oxygen. 1823, michael faraday discovered that pressurized carbon dioxide gas can be liquefied. 1835, M. Thilorier made solid carbon dioxide (dry ice). 1884, the first factory to produce liquid carbon dioxide was built in Germany.
Carbon dioxide is abundant in nature and is a part of the atmosphere. Some associated gases of natural gas or oil fields and carbonate-formed ores also contain carbon dioxide. Carbon dioxide in the atmosphere is 0.03~0.04% (volume ratio), and the total amount is about 2.75×10/2 t, which is mainly produced by the combustion of carbonaceous materials and animal metabolism. In all sectors of the national economy, carbon dioxide has a very wide range of uses. Carbon dioxide products are mainly extracted and recovered from process gas, fermentation gas, lime kiln gas, acid neutralization gas, ethylene oxidation by-product gas and flue gas. At present, the purity of commercial products is not less than 99% (by volume).
Related chemical equations of carbon dioxide
Carbonic acid is unstable and easy to decompose;
h？ CO？ = =δ= = H？ O + CO？ ↑
So 2HCl+CaCO? ==== CaCl？ + H？ O + CO？ ↑
Carbon dioxide can be dissolved in water to form carbonic acid;
CO？ + H？ O ==== H？ CO？
Adding carbon dioxide to clear limewater will form white calcium carbonate;
CO？ +Ca (oh)? ==== CaCO？ ↓ + H？ O
If there is too much carbon dioxide, there will be:
CaCO？ + CO？ + H？ O ==== Ca(HCO？ )?
Carbon dioxide will deteriorate caustic soda;
2NaOH + CO？ ==== Na？ CO？ + H？ O
If carbon dioxide is excessive:
Na？ CO？ + CO？ + H？ O ==== 2NaHCO？
Namely:
NaOH + CO？ ==== NaHCO？
Reaction of carbon dioxide with metallic magnesium;
2Mg + CO？ (Excess) = = Ignition == 2MgO+C
Mg + CO？ (small amount) = = ignition == MgO+CO
Industrial method: Calcining limestone at high temperature;
CaCO？ = = high temperature == CaO+CO? ↑
Laboratory methods:
CaCO？ +2HCI=CaCl？ + H？ O + CO？ ↑
Fixation of carbon dioxide
CO2+C5→ (enzyme) 2C3
In the dark reaction stage of photosynthesis, a molecule of CO? React with a five-carbon compound molecule to generate two three-carbon compound molecules.
Harm of carbon dioxide
Now the temperature on the earth is getting higher and higher, which is caused by the increase of carbon dioxide. Because carbon dioxide has the function of heat preservation, there are more and more members in this group, which makes the temperature rise. In the past 100 years, the global temperature has increased by 0.6℃. At this rate, it is predicted that the global temperature will rise by 1.5-4.5℃ by the middle of the 20th century.
Sea level rise is also caused by the increase of carbon dioxide. In the past 100 years, the sea level will rise by 14 cm. By the middle of 2 1 century, the sea level will rise by 25- 140 cm. As the sea level rises, the Amazon rainforest will disappear and all the ice in the polar ocean will melt. All these changes are tantamount to disaster for wildlife.
The air contains about 0.03% carbon dioxide. However, due to the influence of human activities (such as burning fossil fuels), the carbon dioxide content has soared in recent years, leading to the greenhouse effect, global warming, melting glaciers and rising sea levels ... The Kyoto Protocol, which aims to curb excessive carbon dioxide emissions, has come into effect and is expected to curb the greenhouse effect through international cooperation.
Carbon dioxide dry-cleaning
At present, the most common dry cleaning technology is to use hydrocarbons (petroleum) and chlorinated hydrocarbons (such as tetrachloroethylene) as solvents. However, petroleum solvents have low flash point, are explosive, flammable and slow to dry. Chlorinated hydrocarbons are pungent and toxic (generally, the content in the air is limited to below 50ppm). The dry cleaning industry, especially some countries in Europe and America, has been looking for a clean, hygienic, safe and efficient cleaning solvent. At present, there are new cleaning agents such as Greenearth, RYNEX and liquid carbon dioxide. The smectite is a clear and odorless liquid, and its KB value (cleaning rate) is close to that of petroleum solvent, but lower than that of tetrachloroethylene, and it is expensive. The KB value of RYNEX is similar to that of tetrachloroethylene, but the water content is high, evaporation is too slow, it is not easy to recycle, and the dry cleaning cycle is long. The KB value of liquid carbon dioxide is higher than that of petroleum solvent and slightly lower than that of tetrachloroethylene, but it is better than that of tetrachloroethylene in color bleeding and preventing dirt from re-agglutinating.
As a metabolite and industrial by-product of life activities, carbon dioxide exists in nature, mainly from thermal power generation, building materials, steel, chemicals, automobile exhaust and natural carbon dioxide gas fields. It is the main gas causing the "greenhouse effect". Liquid carbon dioxide dry cleaning solvent is an industrial by-product, which is only used before returning to nature and will not increase the concentration of carbon dioxide in the atmosphere. China has the second largest carbon dioxide emission in the world (about 3 billion tons). In order to make full use of this resource, China has set up many research projects.