Characteristics and applications of catalysts in petrochemical products

Petrochemical Catalysts
An important type of product in the catalyst industry, it is used in chemical processing processes in the production of petrochemical products. There are many types of catalysts. According to their catalytic functions, they mainly include oxidation catalysts, hydrogenation catalysts, dehydrogenation catalysts, hydroformylation catalysts, polymerization catalysts, hydration catalysts, dehydration catalysts, alkylation catalysts, and isomerization catalysts. , disproportionation catalyst, etc., the first five are used in larger amounts.
Oxidation Catalyst
Most of the processes used in the petrochemical industry to manufacture oxygen-containing products are selective oxidation processes. Selective oxidation products account for 80% of the total organic chemical products; the catalyst used must first have high catalytic selectivity. Selective oxidation catalysts can be divided into gas-solid phase oxidation catalysts and liquid phase oxidation catalysts.
Take the production of ethylene glycol as an example. Among the production costs of ethylene glycol, the unit consumption costs of oxygen and ethylene account for 85-90% of the cost, and the unit consumption of both oxygen and ethylene mainly depends on the selectivity of the catalyst. Therefore, the core competition of the ethylene glycol unit is the competition of catalysts. Highly selective catalysts not only directly determine the unit cost of raw materials such as ethylene and oxygen, but also produce less by-products and impurities, resulting in higher quality ethylene glycol and ethylene oxide products.
Gas-solid phase oxidation catalyst
Gas-solid phase oxidation catalysts are composed of carrier silicon carbide or α-alumina and active components vanadium-titanium oxides, and are mainly divided into the following five categories:
(1) Silver catalyst for oxidation of ethylene to ethylene oxide, using silicon carbide or α-alumina as a carrier (adding a small amount of barium oxide as a cocatalyst). After continuous improvement of catalysts and process conditions, the weight yield based on ethylene has exceeded 100%.
On October 20, 2010, the highly selective silver catalyst YS-8810 developed by Yanshan Branch was the first to be industrialized in Shanghai Petrochemical’s No. 2 ethylene glycol unit and achieved good operating results. At the same time, the yield of ethylene oxide is greatly improved.
(2) A catalyst made of vanadium-titanium oxide as an active component and sprayed on silicon carbide or corundum, used to oxidize o-xylene to produce phthalic anhydride. A catalyst made by spraying active components of vanadium-molybdenum oxides on corundum, and is used for the oxidation of benzene or butane to produce maleic anhydride.
Oxidation of o-xylene to phthalic anhydride
The improvement of this type of catalyst is towards the development of multi-component catalysts, and eight-component catalysts have appeared. The shape of the carrier has also been changed from spherical to annular, semicircular, etc. to facilitate heat transfer. The general trend is to pursue high load, high yield and high purity of products.
(3) Alcohol is oxidized to aldehydes or ketones, such as methanol to formaldehyde using silver-pumice (or alumina), iron oxide-molybdenum oxide and electrolytic silver catalysts.
(4) Ammonia oxidation catalyst. In the 1960s, a catalyst was developed with a bismuth-molybdenum-phosphorus composite oxide catalytic component supported on silicon oxide. Propylene, ammonia, and air were passed through the catalyst to synthesize it in one step. Acrylonitrile.
Synthesis reaction of acrylonitrile
In order to improve selectivity and yield and reduce environmental pollution, the catalyst is constantly being improved, and some new catalysts contain up to 15 elements.
(5) Oxychlorination catalyst. In the 1960s, a copper chloride-alumina catalyst was developed. Dichloroethane can be obtained by passing ethylene, hydrogen chloride and air or oxygen in an ebullating bed reactor. Dichloroethane is thermally cracked to obtain vinyl chloride monomer. This method is very beneficial to the development of polyvinyl chloride in areas where electricity is expensive and petrochemical industry is developed.
Liquid Phase Oxidation Catalyst
A catalyst used to oxidize aromatic hydrocarbon side chains to aromatic acids. For example, p-xylene is heated in an acetic acid solution with cobalt acetate and a small amount of ammonium bromide, and then oxidized by air to produce terephthalic acid.
To oxidize ethylene and propylene to acetaldehyde and acetone (Wack method), use a copper chloride solution catalyst containing a small amount of palladium chloride, pass in olefins, air or oxygen, and obtain the required oxygen-containing compounds after one or two steps of reaction.
Reaction to produce propylene oxide by chlorohydrin method
The liquid phase oxidation catalyst method severely corrodes the reaction equipment and has been gradually replaced by the organic peroxide method. This method is only used to prepare propylene oxide.
Hydrogenation Catalyst
Such catalysts are used in product production processes and are also widely used in the refining processes of raw materials and products. It is divided into three categories according to different hydrogenation conditions:
1
Selective hydrogenation catalyst
When ethylene and propylene obtained by cracking petroleum hydrocarbons are used as polymerization raw materials, they must first be selectively hydrogenated to remove trace impurities such as alkynes, dienes, carbon monoxide, carbon dioxide, and oxygen, without causing any loss of olefins. The catalyst used is generally palladium, platinum or nickel, cobalt, molybdenum, etc. supported on alumina. By controlling the amount of active material, the carrier and the manufacturing method of the catalyst, selective hydrogenation catalysts with different properties can be obtained. Others, such as the refining of pyrolysis gasoline and the hydrogenation and reduction of nitrobenzene to aniline, also use selective hydrogenation catalysts.
2
Non-selective hydrogenation catalyst
Catalyst for deep hydrogenation to saturated compounds. Such as the nickel-alumina catalyst used for hydrogenating benzene to produce cyclohexane, the hydrogenation of phenol to produce cyclohexanol, and the skeleton nickel catalyst used for hydrogenating adiponitrile to produce hexamethylenediamine.
3
Hydrogenolysis Catalyst
The process of producing higher alcohols through hydrogenation and hydrogenolysis of oils using copper chromite as a catalyst.
Dehydrogenation Catalyst
High temperature dehydrogenation catalytic technology
For example, iron oxide-chromium oxide-potassium oxide can dehydrogenate ethylbenzene (or n-butene) into styrene (or butadiene) at high temperature and in the presence of large amounts of water vapor.
Low temperature dehydrogenation catalytic technology
Since dehydrogenation generally requiresom.cn/wp-content/uploads/2022/07/1657846374395.jpg” width=”500″ height=”500″ srcset=”https://www.bdma.com.cn/wp-content/uploads/2022 /07/1657846374395.jpg 500w, https://www.bdma.com.cn/wp-content/uploads/2022/07/1657846374395-350×350.jpg 350w, https://www.bdma.com.cn/wp -content/uploads/2022/07/1657846374395-200×200.jpg 200w, https://www.bdma.com.cn/wp-content/uploads/2022/07/1657846374395-300×300.jpg 300w, https://www .bdma.com.cn/wp-content/uploads/2022/07/1657846374395-220×220.jpg 220w” sizes=”(max-width: 500px) 100vw, 500px” title=”Characteristics and application illustrations of catalysts in petrochemical products 1″ alt=”Characteristics and Application Illustrations of Catalysts in Petrochemical Products 1″ />
Isomerization Catalyst
The action or process of interconversion of one isomer into another. A process that changes the structure of a compound without changing its composition and molecular weight. Generally refers to changes in the position of atoms or groups in organic compound molecules. Often carried out in the presence of a catalyst.
Catalysts mainly fall into the following categories:
① Friedel-Crafts type catalyst, commonly used are aluminum trichloride-hydrogen chloride, boron fluoride-hydrogen fluoride, etc. This type of catalyst has high activity and low reaction temperature, and is used for liquid phase isomerization, such as the isomerization of n-butane into isobutane, the isomerization of xylene, etc.
②Precious metal catalysts with solid acid as carrier, such as platinum-alumina, platinum-molecular sieve, palladium
-Aluminum oxide, etc. This type of catalyst is a dual-functional catalyst, in which the metal component plays the role of hydrogenation
And dehydrogenation, solid acid plays an isomerization effect.
When using this type of catalyst, the reaction needs to be carried out in the presence of hydrogen, so it is also called a hydroisomerization catalyst and is used for gas phase isomerization. Isomerization of alkanes, alkenes, aromatics, and cycloalkanes can also be used. In particular, only this type of catalyst is effective for the isomerization of ethylbenzene into xylenes and naphthenes. Its advantages are less coking and long service life.
③ Non-noble metal catalysts using solid acids as carriers, such as nickel-molecular sieves, etc., generally require the presence of hydrogen for gas phase isomerization, but cannot isomerize ethylbenzene into xylene.
④ZSM-5 molecular sieve catalyst is mainly used for the gas phase or liquid phase isomerization of xylene.
Disproportionation Catalyst
By applying the disproportionation process, one hydrocarbon can be converted into two different hydrocarbons. Therefore, disproportionation is one of the important methods to regulate the supply and demand of hydrocarbons in industry. Important applications are the disproportionation of toluene to increase the production of xylene and simultaneously produce high-purity benzene, and the triolefin process of propylene disproportionation to produce polymer-grade ethylene and high-purity butenes (mainly cis and trans-2-butene).
Toluene disproportionation reaction
Silica-alumina catalysts are generally used to convert toluene into benzene and xylene. Currently, molecular sieve catalysts are popular in research, such as mordenite-type silk molecular sieves.