The vast majority of petrochemical oxygenated products manufacturing process for the selective oxidation. Selective oxidation products accounted for 80% of the total organic chemical products; the catalyst used first requires a high catalytic selectivity. Selective oxidation catalyst can be divided into gas-solid phase oxidation catalyst and liquid phase oxidation catalyst. (See catalyst selectivity)
Gas-solid oxidation catalyst
① ethylene oxide to ethylene oxide with silver catalyst to silicon carbide or α-alumina as a carrier (plus a small amount of barium oxide as a cocatalyst). After the continuous improvement of the catalyst and the process conditions, the weight yield in terms of ethylene has exceeded 100%.
② vanadium - titanium oxide as the active component, spraying on silicon carbide or corundum made of catalyst for the oxidation of ortho-xylene phthalic anhydride. Vanadium - molybdenum oxide active component sprayed on corundum made of catalyst for the oxidation of benzene or butane to maleic anhydride. Improvements of this type of catalyst are toward the development of multicomponent catalysts and the emergence of eight-component catalysts. Carrier shape from spherical to ring, semicircle, etc. to facilitate heat transfer. The general trend is the pursuit of high load, high yield and high purity of the product.
③ alcohol oxidation of aldehydes or ketones, such as the oxidation of methanol to formaldehyde with silver - pumice (or alumina), iron oxide - molybdenum oxide and silver catalyst.
④Ammoxidation catalyst, developed in the 1960s with bismuth - molybdenum - phosphorus composite oxide catalytic component on silica supported on the catalyst, the catalyst through the propylene, ammonia, air, one-step synthesis of acrylonitrile . In order to improve the selectivity and yield, reduce environmental pollution, all countries are on the catalyst continuous improvement, and some new catalyst contains up to 15 kinds of elements. ⑤ oxychlorination catalyst, developed in the 60s copper chloride - alumina catalyst, in the ebullated bed reactor through ethylene, hydrogen chloride and air or oxygen available dichloroethane. Dichloroethane thermal cracking of vinyl chloride monomer. This method is very advantageous for the development of polyvinyl chloride in areas where the electricity is expensive and the petrochemical industry is developed.
Liquid phase oxidation catalyst
Mainly: ① Ethylene, propylene oxidation of acetaldehyde, acetone (Wacker), with a small amount of palladium chloride solution of copper chloride catalyst, access to olefins, air or oxygen, after one or two steps to get the required Oxygenates. The disadvantage is that the reaction equipment is seriously corroded. ② aromatic side chain oxidized to aryl acid catalyst, such as p-xylene in acetic acid solution plus cobalt acetate and a small amount of ammonium bromide heating, air oxidation to produce terephthalic acid, but serious corrosion of the reaction equipment.
In addition to hydrogenation catalyst used in the production process, but also widely used in refining raw materials and products. According to the different hydrogenation conditions are divided into three categories: ① selective hydrogenation catalyst, such as petroleum hydrocarbon cracking of ethylene, propylene used as raw materials for polymerization, the hydrogenation must be selected, to remove alkyne, dienes, carbon monoxide, carbon dioxide, oxygen And other trace impurities, but no loss of olefin. The catalysts used are typically palladium, platinum or nickel, cobalt, molybdenum and the like on alumina. Control of the amount of active material, the carrier and the catalyst manufacturing method can be obtained with different performance selection hydrogenation catalyst. Others such as pyrolysis gasoline refining, nitrobenzene hydrogenation reduction to aniline, but also the choice of hydrogenation catalyst. ② non-selective hydrogenation catalyst, that is, a catalyst for deep hydrogenation into a saturated compound. Such as benzene hydrogenation of cyclohexane with nickel - alumina catalyst, hydrogenation of phenol to cyclohexanol, adiponitrile hydrogenation has been used to prepare the skeleton of nickel catalyst. ③ hydrogenolysis catalyst, such as copper chromite catalyst for hydrogenolysis of hydrogenolysis of higher alcohol production.
For example, iron oxide-chromium oxide-potassium oxide can dehydrogenate ethylbenzene (or n-butene) to styrene (or butadiene) in the presence of high temperature and large amounts of water vapor. Since dehydrogenation generally takes place in the presence of high temperature, reduced pressure or a large amount of diluent, the energy consumption is large. In recent years, the development of a catalyst for oxidative dehydrogenation at lower temperatures has been developed. Such as n-butene with bismuth - molybdenum metal oxide catalyst by oxidative dehydrogenation of butadiene.
It is the earliest complex catalyst in industrial production. With alkenes and syngas (CO + H2) in the presence of a catalyst to form an aldehyde with more than one carbon atom. Such as the use of ethylene, propylene as the raw material by hydroformylation (commonly known as carbonyl synthesis) obtained propionaldehyde, butyraldehyde. Hydroformylation process used in the past with cobalt carbonyl complexes as catalysts in the liquid under high temperature and pressure. In recent years, with carbonyl rhodium phosphine complex catalyst, the reaction pressure from the original 20MPa down to 5MPa, and increased the selectivity of normal aldehyde, saving energy and reducing costs. Currently, research on the recovery of rhodium and the search for other inexpensive, readily available, and efficient catalysts for rhodium substitution and the investigation of supported complex catalysts simplify the separation process.
Polyethylene is mainly divided into two kinds of low density and high density. In the past, the former use high-pressure method (100 ~ 300MPa) production, oxygen, organic peroxides as a catalyst. The latter are mostly produced by the medium-pressure method or the low-pressure method. The medium-pressure method uses chromium-molybdenum oxide as the catalyst on the silica gel, the low-pressure method uses the Ziegler-type catalyst (titanium tetrachloride and triethyl aluminum system ), Polymerization at low temperature and pressure. In recent years, the development of a new type of highly efficient catalyst, although the plant has its own unique new catalyst, but more with magnesium compounds as a carrier of titanium - aluminum catalyst system, has now reached per gram of titanium can be obtained more than hundreds of thousands of grams of polyethylene level , Due to the very few residual catalyst in the polymer, it can eliminate the purification of the polymer and reduce the cost. In addition, the process of producing linear low-density polyethylene at low pressure has also been developed.
Polypropylene production also developed a supported titanium-aluminum system efficient catalyst, per gram of titanium can be produced more than 1000kg of polypropylene.
In addition, there are also sulfuric acid or phosphoric acid catalysts for olefin hydration such as ethylene to ethanol;? -alumina catalysts for alcohol dehydration such as ethanol dehydration to ethylene; anhydrous trichloride for alkylation such as benzene and ethylene to produce ethylbenzene Aluminum-hydrogen chloride catalysts; isomerization catalysts such as lithium phosphate catalysts for the conversion of propylene oxide to allyl alcohols; and mordenite-type molecular sieve catalysts for disproportionation catalysts such as toluene to benzene and xylene.