Heterogeneous catalysts include solid acid catalysts, organic base catalysts, metal catalysts, metal oxide catalysts, composite catalysts, rare earth catalysts, molecular sieve catalysts, biocatalysts, nano-catalysts, etc. According to the reaction type, it can be divided into polymerization, polycondensation, esterification, acetalization, hydrogenation, dehydrogenation, oxidation, reduction, alkylation, isomerization and other catalysts. According to the function, it is divided into main catalyst and cocatalyst.
Therefore, the biological detergent that uses enzymes to decompose stains on clothes is the most effective at low temperature. Enzymes are of great significance in physiology, medicine, agriculture and industry. At present, the application of enzyme preparation is increasingly extensive.
The common catalysts in chemistry are oxygen: manganese oxide MnO2, iron oxide Fe2O3, cobalt oxide CoO, nickel oxide NiO, copper oxide CuO, cuprous oxide Cu2O and zinc oxide ZnO.
Extended data:
definition
A substance that can change the chemical reaction rate (increase or decrease) of reactants in a chemical reaction without changing the chemical equilibrium, and its quality and chemical properties have not changed before and after the chemical reaction is called a catalyst (solid catalyst is also called a catalyst).
Characteristics of catalytic reaction
There are four basic characteristics of catalytic reaction, which can be deduced according to the definition, which is very important for understanding the role of catalysts.
1, the catalyst can only accelerate the thermodynamically possible reaction. When it is necessary to develop a new catalyst for chemical reaction, thermodynamic analysis should be carried out to see if it is a thermodynamically feasible reaction.
2. The catalyst can only accelerate the reaction to reach equilibrium, and cannot change the equilibrium position (equilibrium constant) of the reaction.
3. The catalyst is selective to the reaction. When the reaction may have many different directions, the catalyst only accelerates one direction, and the reaction rate and selectivity are unified.
4. Service life of catalyst. The catalyst can change the rate of chemical reaction, and it does not enter the reaction itself. Under ideal conditions, the catalyst will not be changed by the reaction. However, in the actual reaction process, the catalyst will react chemically when heated for a long time, and some unpredictable physical and chemical changes will also occur.
According to the definition and characteristic analysis of catalyst, catalyst has three important indexes: activity, selectivity and stability.
Catalyst discovery
This catalyst was first discovered by Swedish chemist Bezerius. /kloc-More than 0/00 years ago, there was a story about the magical "God Cup".
One day, the Swedish chemist Bezelius was busy doing experiments in the chemistry laboratory. In the evening, his wife Maria prepared food and wine for friends and relatives to celebrate her birthday. Bezelius was so immersed in the experiment that he completely forgot about it. It was not until Maria pulled him out of the laboratory that he suddenly realized and hurried home.
On entering the room, the guests raised their glasses to congratulate him. He took a glass of peach wine and drank it without washing his hands. When he filled the second glass of wine to drink, he frowned and shouted, "Maria, why did you bring me vinegar!" " "Maria and the guests were stunned. Maria looked at the bottle carefully and poured out a cup to taste. It's really a mellow pink wine!
Bezerius casually handed the glass of wine he poured. Maria took a sip and almost spit it out. She also said, "Why did the liqueur suddenly turn into acetic acid?" The guests approached each other to observe and guess the strange things that happened in this "God Cup".
Bezerius found a small amount of black powder in the original glass. He looked at his hands and found that they were covered with platinum black when grinding platinum in the laboratory. He gulped down the glass of sour wine excitedly.
It turns out that the magic of turning wine into acetic acid comes from platinum powder, which can accelerate the chemical reaction between ethanol (alcohol) and oxygen in the air to produce acetic acid. Later, people called this action catalysis or catalysis, which means "untie" in Greek.
1836, he also published a paper in Yearbook of Physical Chemistry, and put forward the concepts of "catalysis" and "catalyst" used in chemical reactions for the first time.
Catalyst composition
Most catalysts have three distinguishable components: active component, carrier and cocatalyst.
effective constituent
The active component is the main component of the catalyst, sometimes composed of one substance and sometimes composed of many substances.
carrier
The carrier is a dispersant, adhesive or carrier for catalytically active components, and it is the skeleton for loading active components. A catalyst prepared by loading an active component and a cocatalyst component on a carrier becomes a supported catalyst.
initiator
Co-catalyst is a small amount of substance added to the catalyst, which is an auxiliary component of the catalyst. It has little or no activity, but after they are added to the catalyst, the chemical composition, chemical structure, ionic valence, acidity and alkalinity, lattice structure, surface structure, pore structure, dispersion state and mechanical strength of the catalyst can be changed, thus improving the activity, selectivity, stability and life of the catalyst.
preparation method
Mechanical mixing, precipitation, impregnation, spray evaporation, hot melting, leaching and ion exchange.
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