Causes of Catalyst Poisoning, What is Catalyst Poisoning

One of the reasons: "cation" poisoning.

1. Composition of cations: metal ions and basic nitrides, ammonia and organic amines in C4 raw materials.

sodium ions and calcium ions brought by incomplete washing of upstream raw materials;

Soluble iron ions and chromium ions generated by equipment pipes or valves;

trace amounts of aluminum ions and silicon ions in FCC molecular sieves;

Basic compounds such as ammonia and methylamine in C4 also belong to the category of cations.

3. Principle and form of poisoning: These cations and SO3OH in the catalyst produce ion exchange and make the catalyst "poisoned". The reaction formula is as follows:

so3oh+m+(na+、ca2+、fe3+、cr4+、al4+、nh4+、ch3nh2+……

Poisoning form: "layer by layer" poisoning, that is: the first contact with the material is poisoned, and then the contact with the material is not poisoned.

Cause 2: Hydrolyzable nitrile and amide poisoning.

In catalytic cracking, C4 and C5 feedstocks usually contain acetonitrile and propionitrile.

In the raw material of vapor cracking C4, there is occasionally DMF for the extraction of upstream butadiene

Reason 3: The catalyst pores of the new water treatment agent are blocked, which inactivates the catalyst.

Reason 4: The catalytic group falls off, which inactivates the catalyst.

The catalyst of the new water treatment agent has a maximum temperature resistance of 120, but when it is operated at this temperature for a long time, the sulfonating group of the catalyst will fall off from the structural skeleton and flow into the liquid phase, resulting in the inactivation of the catalyst.

Catalyst poisoning simply refers to the phenomenon that its reactive active site is occupied by other ions or the surface substance hinders the oxidant and the reducing agent cannot be contacted, resulting in a decrease in denitrification efficiency and activity.

The alkali metal poisoning of the catalyst is generally Na+, K+ produced by the combustion of alkali metals in coal, and this kind of corrosive mixture follows the flue gas into the SCR flue gas denitrification system, such as K+, aerosol particles can directly penetrate into the catalyst and form V-OH with V-OH by a larger surface area and diffusion coefficient, resulting in a decrease in NH3 adsorption, resulting in less reaction between NH3 and NO, and reduced activity.

AS poisoning refers to the oxidation of AS2O3 gas into AS2O5, and at the same time, AS2O3 diffuses into the catalyst and solidifies in the active and inactive regions of the catalyst, which hinders the diffusion of the reaction gas inside the catalyst, resulting in a decrease in activity.

It means that due to the insufficient purity of the raw material, a certain impurity contained in it preempts the active center of the catalyst to form a substance without catalytic ability, which inactivates the catalyst.

According to whether it can be recovered, it is divided into temporary poisoning and permanent poisoning, the impurities that can cause poisoning are called poisons, the poisons are different for different catalysts, and the poisons are not absolute, and the inactivation will be affected by the temperature concentration at the same time, and even some poisons promote the reaction when the concentration is low.

Because most catalysts are accompanied by harmful side reactions in the catalytic process (in other words, the catalyst is not an enzyme, the specificity is not high, and multiple reactions will be catalyzed at the same time), so in order to reduce the side reactions, sometimes artificial poisoning is carried out to inactivate the active center of the side reactions, and only catalyze the main reaction, so as to improve the utilization rate of raw materials and the purity of the products.

Poisons are varied, and for the same catalyst, only in relation to the reaction it catalyzes can it be clearly indicated what is a poison That is, the poison is not only for the catalyst, but also for the reaction catalyzed by the catalyst. During the period of stable activity, catalysts tend to have a significant decrease in activity due to exposure to small amounts of impurities, a phenomenon known as catalyst poisoning. A substance that causes a catalyst to lose its catalytic effect is called a poison of a catalyst.

If the activity can still be restored after the toxic factors are eliminated, it is called temporary poisoning, otherwise it is called permanent poisoning. Some catalysts are poisons in some reactions, some of which are temporary poisons, and some are permanent poisons For example, iron catalysts used in the synthesis of ammonia, water and oxygen are poisons, when this poisoning phenomenon occurs, the catalyst can be reactivated by reducing or heating, and this poisoning is temporary poisoning, or reversible poisoning; The sulfur or phosphorus compounds are also poisons for this catalyst and this reaction, and when they cause poisoning, it is difficult for the catalyst to reactivate, which is permanent poisoning, or irreversible poisoning, and the latter kind of poisoning can be prevented. Poisoning not only affects the activity of the catalyst, causing the activity of the catalyst to decrease, but also affects the selectivity of the catalyst Poisoning is a practical problem often encountered when using catalysts in chemical production, but we are not very clear As for how to prevent poisoning and detoxification, it should be solved through practice

Catalyst poisoning is the catalyst itself due to the presence of some impurities, so that the catalytic activity of the catalyst itself decreases or even loses.

The catalyst reacts with other substances and some of the catalytic effects cannot be carried out normally, thus reducing the efficiency of catalysis.

Catalyst poisoning should be caused by the reaction of the catalyst.

Summary. Acid catalysis refers to the catalytic process in which a catalyst and a reactant molecule react to form an active positive carbon ion intermediate compound (the main mode of activation) by donating protons or accepting electron pairs, and then decompose into a product. Alumina, molecular sieves are commonly used solid acid catalysts.

Acid catalysts are generally used for the activation of olefins and the cracking of alkyl aromatic hydrocarbons. The catalytic mechanism of superacid catalysts is not a positive carbon ion mechanism.

Hello, I am glad to answer for you that the acid catalyst can be revived after treatment with hydrogen, water vapor, oxygen, etc.

Acid catalysis refers to the catalytic process in which the catalyst and the reactant molecule form an active positive carbon ionizer intermediate compound (the main mode of activation) by donating protons or accepting electron pairs, and then decompose into a product. Alumina, molecular sieves are commonly used solid acid catalysts. Acid catalysts are generally used for the activation of olefins and the cracking of alkyl aromatic hydrocarbons.

The catalytic mechanism of the super-acid cluster catalyst does not belong to the positive carbon ion mechanism.

Can you revive with steam after alkaline nitrogen poisoning.

Dear, yes.

In 1916, Langmuir went one step further by proposing an explanation for the catalytic effects of substances such as platinum: they are so difficult to react that they cannot be expected to participate in general chemical reactions.

Langmuir argues that there are redundant chemical bonds on the surface of platinum metal.

Able to grasp hydrogen molecules and oxygen molecules. When hydrogen and oxygen molecules are bound to a surface very close to platinum, they are easier to synthesize into water molecules than if they were ordinary free gaseous molecules.

Once the water molecules are formed, they are pushed away from the surface of the platinum by the hydrogen and oxygen molecules. Platinum captures hydrogen and oxygen, oxidizes hydrogen and oxidizes to form water, releases the water, captures hydrogen and oxygen, and forms water, and the process can go on endlessly.

This process is called surface catalysis. Naturally, a given mass of metal, the finer the powder, the surface area that can provide.

The larger the larger, and therefore the more efficient it is to carry out catalysis. Of course, if any foreign substance adheres firmly to the platinum surface, the catalyst will lose its efficacy, which is also called catalyst poisoning.

The phenomenon of poisoning is different for different metals. For example, sodium poisoning is a significant decrease in activity, and the phenomenon is a significant increase in oil refining, a decrease in dry gas, no conversion of products, and a decrease in the density of oil slurry. For example, calcium poisoning has a certain effect on activity, but the catalyst is sticky and the inclined tube delivery is unstable.

After heavy metal poisoning, the activity and selectivity of the catalyst decreased, resulting in an increase in hydrogen and coke yields, a decrease in light oil yields, and an increase in the unsaturation of the product. The molar ratio of hydrogen to methane increased.

Heavy metals such as Fe

Ni, Cu, V, etc. are deposited on the surface of the cat, which reduces the selectivity of the cat, increases the coke yield, reduces the yield of the target product, increases the unsaturation of the product, and the carbon in the gas.

Third, the reduction of the carbon four component, especially the increase in hydrogen yield.

At present, catalytic poisoning is still analyzed for nickel and vanadium metal content, because the pollution index is also the main measure of them. After poisoning, it is first reflected in the distribution of products, there are more products at both ends, that is, there are more dry gas and coke, and at the same time, the hydrogen methane ratio in the dry gas is also significantly increased. In particular, changes in raw materials can be reflected immediately.

In addition, the pollution index of the catalyst is also best tracked.

Catalyst poisoning is mainly nickel, vanadium, sodium, iron and other metal poisoning, after poisoning is mainly reflected in the distribution of products, dry gas and coke are more, while the ratio of hydrogen and methane in dry gas has increased significantly.

This statement is not very accurate, and catalyst poisoning is.

The trace impurities contained in the reaction raw materials significantly reduce or lose the activity and selectivity of the catalyst. The essence of the phenomenon of poisoning is the formation of inactive species by a certain chemical action of trace impurities and the active center of the catalyst. In the gas-solid heterogeneous catalytic reaction, adsorption complexes are formed.

One is that if the effect of the poison and the active component is weak, the activity can be restored by a simple method, which is called reversible poisoning or temporary poisoning. The other type is irreversible poisoning, which cannot be reactivated by simple methods.

So toxic gases don't necessarily poison catalysts.

Similarly, non-toxic can also poison the catalyst.

Toxic vs. non-toxic is for people.

Different catalysts will be different. Ask about the specific catalyst.

For example, the iron catalyst used in the synthesis of ammonia, water and oxygen are poisons, when poisoning, the catalyst can be reactivated by reducing or heating, this poisoning is temporary poisoning, or reversible poisoning; Sulfur or phosphorus compounds are also poisons to the catalyst and this reaction, and when poisoning is caused by them, it is difficult for the catalyst to reactivate, which is permanent poisoning, or irreversible poisoning.