Chemistry has not only created wealth for mankind, but also brought danger to mankind. The history of every science is full of exploration and progress. Because of the uncertainty in science, chemists will inevitably synthesize compounds with unknown properties in the research process. Only through long-term application and research can we be familiar with their properties. At this time, new substances may have had an impact on the environment or human life. The traditional chemical industry has brought serious pollution to the environment. At present, the world produces 300 million to 400 million tons of hazardous waste every year, which is harmful to the environment and threatens the survival of mankind. The grim reality makes it necessary for all countries to find a sustainable development path that does not destroy the environment and endanger human survival. Can chemical industry produce chemicals that are harmless to the environment? Even develop a process that does not produce waste? The slogan of green chemistry originated in the United States, where the chemical industry is very developed. 1990, the United States passed the "Pollution Prevention Action" Act. 199 1 year later, "green chemistry" was put forward by the American Chemical Society (ACS) and became the central slogan of the US Environmental Protection Agency (EPA), which immediately received positive responses from all over the world.
Second, green chemistry research.
Green chemistry is a multidisciplinary research field that emerged in 1990s. It can be interpreted as environmentally friendly chemistry, and its core connotation is to minimize or completely eliminate the use and production of harmful substances in the reaction process and chemical production.
1. The core of green chemistry
Using chemical principles to reduce and eliminate environmental pollution caused by industrial production from the source. International journal of green chemistry
According to the principle of green chemistry, the ideal chemical production mode is that all atoms of reactants are transformed into the expected final product.
2. The nature of green chemistry
(1) Make full use of resources and energy, and adopt non-toxic and harmless raw materials; (2) the reaction is carried out under non-toxic and harmless conditions, thus reducing the waste discharge to the environment; (3) Improve the utilization rate of atoms, and try to make all atoms as raw materials be absorbed by products to realize "zero emission"; (4) To produce environmentally friendly products that are beneficial to environmental protection, community safety and human health. Green chemistry poses a new challenge to chemists and is highly valued internationally. From 65438 to 0996, the United States established the "Green Chemistry Challenge Award" to commend those enterprises and scientists who have made outstanding achievements in the field of green chemistry. Green chemistry will change the face of chemical industry and benefit future generations.
3. 12 principles of green chemistry
Green chemistry researchers have summarized the principle of 12 green chemistry, which can be used as a guide and standard for experimental chemists to formulate and evaluate whether a synthetic route, a production process or a compound is green. Prevention of pollution is better than post-treatment of pollution formation. ● When designing the synthesis method, all the materials used should be converted into the final product to the maximum extent. ● The substances used and generated in the reaction are as non-toxic or slightly toxic to human beings and the environment as possible. When designing chemical products, we should try our best to maintain their efficacy and reduce their toxicity. ● Try not to use additives, and use non-toxic substances when necessary. ● The use of energy should be minimized, and its impact on the environment and economy should be considered. The synthesis method should be operated at normal temperature and pressure. ● Maximize the use of renewable raw materials. ● Try to avoid unnecessary derivative steps. ● Catalytic reagents are superior to stoichiometric reagents. ● Chemicals should be designed to be easily degraded into harmless substances after use. ● The analysis method should truly realize online monitoring and control harmful substances before they are formed. The selection and use of various substances in chemical production should minimize the hidden dangers of chemical accidents.
4. Five ways of greening chemical experiments
(1) Carry out green experiments. For example, in the laboratory, H2O2 is decomposed into O2 instead of KClO3, which realizes the greening of raw materials and reaction process. (2) To prevent environmental pollution such as tail gas and waste during the experiment, strengthen tail gas absorption when harmful gases are generated in the experiment, and reuse the experimental products as much as possible. (3) Under the premise of ensuring the experimental effect, reduce the dosage of experimental reagents as much as possible, and make the experiment miniaturized and miniaturized. (4) For dangerous or harsh reaction conditions, serious pollution or expensive instruments and reagents, computer simulation of chemical experiments or watching experimental videos can be used. (5) Properly handle the wastes generated in the experiment to prevent environmental pollution.
5. Atomic economy
The most ideal "atom economy" is that all atoms of the reactant are converted into the expected final target product, and the atom utilization rate is 100%.
6. Chemical reactions that meet the requirements of "green chemistry"
7.5R theory: 1. Reduction-reduction is put forward from the perspective of saving resources and reducing pollution. One of the effective ways to reduce the dosage and how to reduce the dosage while protecting the output is to improve the conversion rate and reduce the loss rate. Reduce the discharge of "three wastes". Mainly to reduce the emission of waste gas, waste water and waste (by-products), which must be lower than the emission standard. 2. Reuse-Reuse Reuse This is the need to reduce costs and waste. Such as catalysts and carriers in chemical industry, we should consider the design of reuse from the beginning. 3. Recovery-recycling recovery mainly includes: recovering unreacted raw materials, by-products, cosolvents, catalysts, stabilizers and other unreacted reagents. 4. Regeneration-Regeneration is an effective way to turn waste into treasure, save resources and energy and reduce pollution. It requires that the recycling of raw materials should be considered in the process design of chemical product production. 5. Rejection-Rejection is the most fundamental way to eliminate pollution. It refers to the refusal to use some irreplaceable, non-recyclable, non-renewable and non-reusable raw materials with obvious toxic and side effects and pollution in the chemical process.