Characteristics and Applications of Catalysts in Petrochemical Products

Characteristics and Applications of Catalysts in Petrochemical Products
Petrochemical catalysts
An important product in the catalyst industry, used in the chemical processing process of petrochemical product production. There are various types of catalysts of this type, which are mainly divided into oxidation catalysts, hydrogenation catalysts, dehydrogenation catalysts, hydroformylation catalysts, polymerization catalysts, hydration catalysts, dehydration catalysts, alkylation catalysts, isomerization catalysts, disproportionation catalysts, etc. according to their catalytic functions. The first five types are used in large quantities. Today, Xiaoqi will take everyone to understand the characteristics and application of these catalysts for your reference!
Oxidation catalyst
The process of producing oxygen-containing products in petrochemical industry is mostly a selective oxidation process. Selective oxidation products account for 80% of the total amount of mechanical and chemical products; The catalyst used first requires high catalytic selectivity. Selective oxidation catalysts can be divided into gas-solid phase oxidation catalysts and liquid-phase oxidation catalysts.

Taking the production of ethylene glycol as an example, the unit consumption cost of oxygen and ethylene accounts for 85-90% of the production cost of ethylene glycol, and the unit consumption of both mainly depends on the selectivity of the catalyst. Therefore, the core competition of ethylene glycol plants is the competition of catalysts. The highly selective catalyst not only directly determines the Unit cost of ethylene, oxygen and other raw materials, but also generates less by-products and impurities, and the quality of ethylene glycol and ethylene oxide products is higher.
Gas solid phase oxidation catalyst
The gas-solid oxidation catalyst consists of a carrier silicon carbide or α－ Aluminum oxide and active component vanadium titanium oxide are mainly divided into the following five categories:
(1) Silver catalyst for the oxidation of ethylene to ethylene oxide, using silicon carbide or α－ Aluminum oxide as the carrier (with a small amount of barium oxide as the co catalyst). Through continuous improvement of catalysts and process conditions, the weight yield of ethylene has exceeded 100%.
On October 20, 2010, the highly selective silver catalyst YS-8810 developed by Yanshan Branch was first industrialized and applied in the Shanghai Petrochemical No.2 ethylene glycol unit, achieving good operational results. At the same time, it greatly improves the yield of ethylene oxide.
(2) A catalyst made by spraying vanadium titanium oxide as the active component on silicon carbide or corundum for the oxidation of ortho xylene to ortho phthalic anhydride. A catalyst made by spraying the active component of vanadium molybdenum oxide on corundum, used for the oxidation of benzene or butane to produce maleic anhydride.

Oxidation of o-xylene to phthalic anhydride reaction
The improvement of this type of catalyst is towards multi-component development, with the emergence of eight component catalysts. The shape of the carrier has also been changed from spherical to circular or semi circular to facilitate heat transfer. The overall trend is to pursue high load, high yield, and high purity of products.
(3) Alcohols are oxidized to aldehydes or ketones, such as silver pumice (or alumina), iron oxide molybdenum oxide, and electrolytic silver catalysts used for the oxidation of methanol to formaldehyde.
(4) Ammoniation oxidation catalyst. In the 1960s, a catalyst was developed using bismuth molybdenum phosphorus composite oxide catalytic components loaded on silicon oxide. Propylene, ammonia, and air were introduced onto this catalyst to synthesize acrylonitrile in one step.
Synthesis reaction of acrylonitrile
In order to improve selectivity and yield, and reduce environmental pollution, the catalyst is constantly being improved, with some new catalysts containing up to 15 elements.
(5) Oxychlorination catalyst, developed in the 1960s as a copper chloride alumina catalyst, can produce dichloroethane by passing ethylene, hydrogen chloride, and air or oxygen in a fluidized bed reactor. Dichloroethane is thermally cracked to obtain vinyl chloride monomer. This method is very beneficial for the development of polyvinyl chloride in areas with expensive electricity and developed petrochemical industries.

Liquid phase oxidation catalyst
Catalysts used for the oxidation of aromatic side chains to aromatic acids, such as adding cobalt acetate and a small amount of ammonium bromide to acetic acid solution to produce terephthalic acid through air oxidation.
Ethylene and propylene are oxidized to acetaldehyde and acetone (Wacker method), using a copper chloride solution catalyst containing a small amount of palladium chloride. Olefins, air, or oxygen are introduced, and the desired oxygenated compound is obtained through one or two steps of reaction.
Reaction of epichlorohydrin production by chlorohydrin method
The liquid phase oxidation catalyst method has severe corrosion on the reaction equipment and has been gradually replaced by the organic peroxide method. Only this method is still used for the preparation of epoxy propane.
Hydrogenation catalyst
This type of catalyst is used in the production process of products and is also widely used in the refining process of raw materials and products. According to the different hydrogenation conditions, it can be divided into three categories:
1 Selective hydrogenation catalyst
When ethylene and propylene obtained from petroleum hydrocarbon cracking are used as polymerization raw materials, selective hydrogenation must be carried out first to remove trace impurities such as acetylene, diene, carbon monoxide, carbon dioxide, oxygen, etc., without loss of olefins. The catalysts used are generally palladium, platinum, nickel, cobalt, molybdenum, etc. loaded on alumina. By controlling the amount of active substances, the manufacturing method of carriers and catalysts, different performance selective hydrogenation catalysts can be obtained. Other catalysts such as refining cracked gasoline and hydrogenation of nitrobenzene to aniline are also used for selective hydrogenation.
2 Non selective hydrogenation catalysts
Catalysts used for deep hydrogenation to form saturated compounds. For example, nickel alumina catalysts are used for the hydrogenation of benzene to cyclohexane, skeleton nickel catalysts are used for the hydrogenation of phenol to cyclohexanol, and the hydrogenation of adiponitrile to adipic amine.
3 Hydrogenolysis catalyst
The process of producing higher alcohols through the hydrogenation of oils and fats using copper chromate as a catalyst.
Dehydrogenation catalyst
High temperature dehydrogenation catalytic technology
Iron oxide chromium oxide potassium oxide can dehydrogenate ethylbenzene (or n-butene) to styrene (or butadiene) at high temperatures and in the presence of a large amount of water vapor.
Low temperature dehydrogenation catalytic technology
Due to the fact that dehydrogenation generally requires high temperature, reduced pressure, or the presence of a large amount of diluent, energy consumption is high. In recent years, catalytic technologies for oxidative dehydrogenation have been developed at lower temperatures. For example, polyethylene is prepared by oxidative dehydrogenation using a bismuth molybdenum based metal oxide catalyst to produce butadiene.
Hydroformylation catalyst
This type of catalyst is the earliest complex catalyst used in industrial production. The reaction of olefins with synthetic gas (CO+H2) in the presence of a catalyst generates an aldehyde with an additional carbon atom. If ethylene and propylene are used as raw materials for hydroformylation (commonly known as carbonylation synthesis) to produce propanal and butyraldehyde.
Various transition metal carbonyl complexes have catalytic effects on hydroformylation reactions. But only carbonyl complexes of cobalt and rhodium are used for industrial production. The hydroformylation process used to be carried out using carbonyl cobalt complexes as catalysts under high temperature and pressure in the liquid phase. In recent years, the use of carbonyl rhodium phosphine complex catalysts has reduced the reaction pressure from the original 20MPa to 5MPa, improved the selectivity of normal aldehydes, saved energy, and reduced costs.
At present, research is being conducted on the recovery methods of rhodium and the search for other cost-effective and efficient catalysts to replace rhodium, as well as on supported complex catalysts to simplify the separation process.
Polymerization catalyst
Polyethylene is mainly divided into two types: low density and high density.
Polyethylene made from Ziegler type catalyst
In the past, the former was mostly produced by high-pressure method (100-300MPa), using oxygen and organic peroxides as catalysts. The latter is mostly produced using medium pressure or low pressure methods. The medium pressure method uses chromium molybdenum oxide and other catalysts loaded on silicon aluminum adhesive as catalysts, while the low pressure method uses Ziegler type catalysts (represented by titanium tetrachloride and triethylaluminum systems) for polymerization at low temperature and low pressure.
In recent years, new and efficient catalysts have been developed. Although each factory has its own unique new catalyst, titanium aluminum system catalysts supported on magnesium compounds are often used. Currently, they have reached the level where tens of thousands of grams of polyethylene can be produced per gram of titanium. Due to the minimal residual catalyst in the polymer, purification treatment of the polymer can be avoided, reducing costs. In addition, a process for producing linear low-density polyethylene under low pressure has been developed.
Polypropylene production has also developed a loaded titanium aluminum system efficient catalyst, which can produce over 1000kg of polypropylene per gram of titanium.
Hydration catalyst
Hydration reaction refers to the reaction process in which water combines with another substance molecule to form one molecule. Water molecules form new compounds by adding their hydrogen and hydroxyl groups to the unsaturated bonds of substance molecules, and the substances that play a catalytic role in this process are called hydration catalysts. This synthesis method has been applied in organic chemical production.
Reaction of Ethylene Hydration to Produce Ethanol
Catalysts used in industrial ethylene to ethanol production
The hydration process is one of the organic synthesis methods, but as an important production method, it is still limited to a few types of products, such as ethanol and diols.
Dehydration catalyst
Dehydration can be carried out under the action of heating or catalyst, or in reaction with a dehydrating agent. Dehydration reaction is the reverse process of hydration reaction, which is usually endothermic reaction. Generally, high temperature and low pressure are conducive to the reaction. In addition, the majority of the dehydration process must be carried out in the presence of a catalyst. The catalyst used in the hydration process – acid catalyst – is also suitable for dehydration, commonly used are sulfuric acid, phosphoric acid, aluminum trioxide, etc.
Dehydration process of alcohol
(1) Reaction of Dehydration of Ethanol to Ethylene
Using sulfuric acid or γ－ Aluminum oxide is used as a catalyst.
(2) Reaction of Dehydration of Butanol to Olefins
Different catalysts have different main products and exhibit extremely high selectivity.
Alkylation catalyst
Alkylation is the process of transferring alkyl from one molecule to another. It is a reaction in which alkyl groups (methyl, ethyl, etc.) are introduced into a compound molecule. Commonly used alkylating agents in industry include olefins, haloalkanes, sulfates, etc.
In standard refining processes, the alkylation system combines low molecular weight olefins (mainly composed of propylene and butene) with isobutane under the action of catalysts (sulfonic acid or hydrofluoric acid) to form alkylates (mainly composed of higher octane and side chain alkanes).
Alkylation reactions can be divided into two types: thermal alkylation and catalytic alkylation.
Due to the high temperature of thermal alkylation reaction and the tendency to produce side reactions such as pyrolysis, catalytic alkylation is commonly used in industry. The main catalytic alkylation methods include:
① Alkylation of alkanes, such as using isobutylene to alkylate isobutane to obtain high octane gasoline components:
② Alkylation of aromatic hydrocarbons, such as alkylation of benzene with ethylene:
Anhydrous aluminum trichloride hydrogen chloride catalyst for the reaction of benzene and ethylene to produce ethylbenzene
③ Alkylation of phenols, such as alkylation of p-cresol with isobutene:
Due to the strong acidity of sulfuric acid and hydrofluoric acid, the corrosion of equipment is quite severe. Therefore, from the perspective of safety production and environmental protection, neither of these catalysts is an ideal catalyst. At present, there are many studies using solid superacids as alkylation catalysts, but so far they have not reached the stage of industrial application.
Isomerization catalyst
The act or process of converting an isomer into another isomer. The process of changing the structure of a compound without altering its composition and molecular weight. It generally refers to the change in the position of atoms or groups in organic compound molecules. It is often carried out in the presence of a catalyst.
Catalysts mainly include the following categories:
① Fred Crawford type catalysts commonly used include aluminum trichloride hydrogen chloride, boron fluoride hydrogen fluoride, etc. This type of catalyst has high activity and requires low reaction temperature, and is used for liquid-phase isomerization, such as the isomerization of n-butane to isobutane, and the isomerization of xylene.
② Precious metal catalysts supported on solid acids, such as platinum alumina, platinum molecular sieve, palladium
-Aluminum oxide, etc. This type of catalyst belongs to the category of bifunctional catalysts, where the metal components start hydrogenation
With dehydrogenation, solid acids undergo isomerization.
When using this type of catalyst, the reaction needs to be carried out in the presence of hydrogen, so it is also known as a hydroisomerization catalyst for gas-phase isomerization. Isomerization of alkanes, olefins, aromatics, and cycloalkanes can also be used. Especially for the isomerization of ethylbenzene to xylene and cycloalkanes, only such catalysts are effective. Its advantages are less coking and long service life.
③ Non precious metal catalysts supported on solid acids, such as nickel molecular sieves, generally also require the presence of hydrogen for gas-phase isomerization, but cannot isomerize ethylbenzene into xylene.
④ ZSM-5 molecular sieve catalyst is mainly used for the gas or liquid phase isomerization of xylene.
Disproportionation catalyst
The application of disproportionation process can transform one hydrocarbon into two different hydrocarbons, therefore disproportionation is one of the important methods for regulating the supply and demand of hydrocarbons in industry. The most important applications are toluene disproportionation to increase xylene production and simultaneously produce high-purity benzene, as well as propylene disproportionation to produce polymer grade ethylene and high-purity butene (mainly cis and trans 2-butene) in the process of polyolefins.
Toluene disproportionation reaction
The conversion of toluene to benzene and xylene usually uses silica alumina catalysts. At present, molecular sieve catalysts, such as mordenite type filamentary molecular sieves, are more popular.