Heavy metal contamination resistance of catalytic cracking catalysts

Heavy metals (iron, copper, nickel, silver, etc.), alkaline earth metals (sodium, calcium, potassium, etc.) and alkaline nitrides in the feedstock oil have the The catalyst has the ability to contaminate. Heavy metals deposited on the catalyst surface can greatly reduce the activity and selectivity of catalytic lee, resulting in lower gasoline yield and increased gas and coke yields, especially an increase in hydrogen content in the cracking gas and a decrease in C, and C, yields. The heavy metal contamination of the catalyst The degree of contamination of the catalyst by heavy metals is expressed by the contamination index.

Pollution index = 0.1(Fe+Cu+ 14Ni+4V)

Where Fe, Cu, Ni and V are the contents of iron, copper, nickel and vanadium on the catalyst, respectively, expressed as 10^-6. The degree of catalyst contamination can also be expressed as the H2/CH4 ratio in the hydrogen generation factor or cracking gas. Because the deposition of catalyst heavy metals deposited on the catalyst, especially Ni has a catalytic dehydrogenation effect, which increases the H2 yield significantly, while it has little effect on the CH4 yield The effect on CH4 yield is not significant. A high hydrogen generation factor or a high H2/CH4 ratio indicates a high level of catalyst contamination.
Under regeneration conditions, vanadium produces V2O5, which can migrate into the pores of the molecular sieve, blocking the pores and destroying the molecular sieve crystallinity. This material can migrate into the pores of the molecular sieve, blocking the pores and destroying the crystallinity of the molecular sieve. Alkaline nitrides can neutralize the acidic active center of the catalyst, which not only reduces the catalyst cracking activity, but also causes an increase in coke generation. This will not only reduce the catalyst cracking activity, but also cause an increase in coke generation.
To control catalyst contamination, in addition to selecting suitable low-sulfur feedstocks, secondary desalination can be carried out in normal reduced-pressure distillation. in addition to selecting a suitable low sulfur feedstock, secondary desalination in normal reduced pressure distillation, improving the decompression operation, renewing part of the catalyst, improving the catalyst and solvent refining. Metal passivators, increased molecular sieve content in the catalyst, low specific surface area and large pore size matrix can also be used. The heavy metal contamination can also be solved by using metal passivators, increasing the molecular sieve content in the catalyst, using low specific surface area and large pore size matrix.