Application of ZSM-5 Molecular Sieve

Application of ZSM-5 Molecular Sieve

4.1 Methanol synthetic gasoline

Using ZSM-5 as a catalyst for methanol synthesis gasoline, methanol can be converted into gasoline, and the obtained gasoline product has a high octane number.It is a high-quality gasoline product that does not contain hydrocarbons above C10, and the gasoline fraction in the hydrocarbon product accounts for about 88%. The conversion rate reached 100%. ZSM-5 structural zeolite containing B2O3 can be used as a catalyst for converting methanol into gasoline. ZSM-5 zeolite (SiO2/Al2O3=27-84) was used for methanol conversion to gasoline, and showed autocatalytic properties. By increasing the reaction temperature from 80°C to 300°C, the production of hydrocarbons increased rapidly.

4.2 Conversion of low-carbon hydrocarbons

Light olefins can be efficiently converted into liquid products rich in light aromatics on HZSM-5 and some modified forms. Equal heteroatom molecular sieves are better than ZSM-5 in this process.

4.3F-T synthesis

In the process of converting syngas into gasoline, modified ZSM-5, heteroatom molecular sieve, modified heteroatom molecular sieve and composite heteroatom molecular sieve have excellent catalytic effect.

4.4 Xylene Isomerization

Para-xylene is an important raw material for polyester fibers, and xylene isomerization is one of the important methods for producing para-xylene. In the xylene isomerization reaction, ZSM-5 with large grains has better selectivity for p-xylene, but its catalytic activity is lower than that of small grains with the same structure. Xylene isomerization on Ni-HZSM-5 suppresses the loss of C8 aromatics and increases the yields of p- and o-xylene by selectively poisoning the acid sites leading to dealkylation and disproportionation with NH3. Isomerization can also be performed on Ni-ZSM-5 and Pt-containing ZSM-5 catalysts. ZSM-5-Pt-Sn- is used for xylene isomerization, the reaction temperature is 250-550 ℃, and Sn in the catalyst inhibits the hydrogenation of benzene ring.

4.5 Selective reformation

ZSM-5 as a catalyst adopts a process similar to selective reforming, which can increase the production of aromatic hydrocarbons and improve the octane number of reformed gasoline. And the concentration of aromatic hydrocarbons in the liquid product reaches 90%, and chemical grade aromatic hydrocarbons can be obtained without solvent extraction. Compared with the ability of ZSM-5 loaded with different metals to generate aromatics, it was found that ZSM-5 loaded with zinc had better effect. The presence of zinc in ZSM-5 significantly improved its aromatization.

4.6 Application in the synthesis of ethylbenzene

Ethylbenzene (BE) is an important compound used to generate polystyrene in petrochemical industry, and it is also an important industrial intermediate. Therefore, ethylbenzene is usually prepared by alkylation of benzene, using ethylene, ethanol, diethyl oxalate, etc. as an alkylating agent. ZSM-5/ZSM-11 co-crystal molecular sieve was prepared in the reaction of benzene and ethylene alkylation to synthesize ethylbenzene, and its acid site was reduced. Coking ability, the ethylene conversion rate can be as high as 95%, and the coke in the catalyst only accounts for 10 (wt)%.

Based on the carbocation mechanism, B acid is the most direct active site in the reaction, and too much B acid and too large grains are very detrimental to the conversion of benzene. In the process of the alkylation of benzene and diethyl oxalate to generate ethylbenzene, the increase of the silicon-alumina ratio in the molecular sieve is used to reduce the acid strength and the number of acid sites in the molecular sieve. According to this factor, the reactant benzene is The conversion and the selectivity of the product ethylbenzene are significantly improved.

4.7 Application in the synthesis of cumene

Cumene (IPB) is an important raw material for the fine chemical industry, mainly used for the production of phenol and acetone. Molecular sieve-type solid acid catalysts are often used in the alkylation of benzene with propane or propylene to produce cumene. Due to the low activity of propane, in the alkylation reaction of benzene and propane, ZSM-5 molecular sieve was modified with Ga, and the two active sites of B acid center and adjacent Ga of the molecular sieve were used to adsorb propane, and the same adsorption in Benzene on these two active sites interacts strongly with it, thereby increasing the conversion of propane. In the alkylation of propylene and benzene to form cumene, using ZSM-5 zeolite molecular sieve, the conversion rate of the reaction is improved, but the selectivity of the product cumene is reduced, and oligomers are formed.

4.8 Diesel Hydrotreating PPD

Most of the crude oil in my country belongs to paraffin-based or intermediate-based crude oil, and the wax content is high, resulting in a high freezing point of distillate oil. Diesel hydrotreating and pour point depressurization technology can not only meet the demand for low pour point diesel in cold regions, but also an effective means to increase the production of diesel.

The technical key of the diesel hydrogenation depressurization process is the hydrogenation depressurization catalyst. The original hydrogenation pour point depressant catalyst was prepared by using ZSM-5 molecular sieve synthesized by organic template agent as a matrix, and the disadvantages were high price, high initial reaction temperature, and environmental problems. Fushun Petrochemical Research Institute uses ZSM-5 molecular sieve synthesized by direct method as the matrix, adopts inorganic acid treatment, impregnation of active metal nickel and high temperature steam treatment and other modification processes to obtain hydrogenation with low cost, no amine pollution and stable reaction performance. FDW-1 (industrial grade 3881) catalyst was the first to achieve industrialization, and it has been widely used in domestic refineries. The application of FDW-1 hydrogenation depressant catalyst in Harbin refinery shows that the raw material is degraded by hydrogen. The shape-selective cracking of the condensing catalyst can reduce the freezing point from 1°C to -55°C, the diesel yield is 92.5%, the gasoline yield is 40%, and the total liquid yield can reach 98.5%.

In 2011, Northeast Petroleum University, ZSM-5 molecular sieve catalyst treated with HPDW-1 hydropour pour point depressant catalyst has the characteristics of strong selectivity and strong ammonia resistance.

4.9 Catalytic dewaxing of lubricating oil

The catalytic dewaxing process of lubricating oil is to use the characteristics of ZSM-5 molecular sieve shape-selective cracking to convert the wax molecules in the raw material into C3-C4 gas and naphtha, and then remove it from the lubricating oil through distillation, so as to reduce the pour point the goal of.

Molecular sieves belong to high silica zeolites, and their acid centers are mainly derived from hydroxyl groups combined with framework aluminum. Since the silicon-alumina ratio of ZSM-5 zeolite can range from 10 to pure silicon (silicalite-1), and the type, strength and distribution of its solid acid can be adjusted, it is widely used in the oil refining industry, especially in diesel pour point depressurization, It is widely used in catalytic dewaxing of lubricating oil and gasoline upgrading.