Ethylbenzene (EB) is a critical raw material in the production of styrene and many other useful products.ethylbenzene synthesis catalyst EB is produced by the acid-catalyzed alkylation of benzene with ethylene. This process produces a wide variety of polyethylbenzenes that must be transalkylated to EB in commercial processes (297). New oxidative dehydrogenation (ODH) catalyst systems are being developed to improve the conversion and selectivity of EB. One method involves the catalytic directional depolymerization of lignin into aromatic monomers in a first step and then the selective alkylation of these monomers in a second step. The process aims to reduce energy consumption and feedstock costs. In order to compare the performance of different EB catalysts, pilot and demonstration reactors were constructed to simulate industrial conditions (temperature, feedstock composition, and olefin space velocity).
Research on new EB processes began in the 1960s, but the development of a gas-phase process using zeolite ZSM-5-based catalysts did not occur until 1980 (297).ethylbenzene synthesis catalyst The Mobil-Badger process used a dedicated second reactor for benzene transalkylation and a low ethylene/benzene ratio to avoid polalkylation and ethylbenzene polymerization. A liquid-phase EB process was later developed by Lummus Crest/Unocal and UOP and employed a single reactor with both ODH and styrene transalkylation.
A recent study showed that SEB-08 is a highly active catalyst for ethylbenzene dehydrogenation with a high selectivity to EB.ethylbenzene synthesis catalyst This catalyst was prepared by co-precipitating ZSM-5 with beta molecule and MCM-22 molecular sieves in a hydrofluoric acid solution and then calcined to prepare a pre-reduced SEB-08 powder. Its performance was compared to other zeolite-based EB catalysts by evaluating its activity in a laboratory styrene-to-ethylene reaction using an olefin space velocity of 22,500 mL g c a t -1 h-1 and a gas hourly space velocity of 3.0 MPa (Table 1).
The results show that the SEB-08 catalyst is capable of performing ODH at a higher charge than previous catalysts and maintains high conversion and a long service life.ethylbenzene synthesis catalyst It is also capable of transalkylating a greater variety of polyethylbenzenes. In addition, the SEB-08 catalyst shows good stability to the formation of ethylene oxide.
The results indicate that the calcination of the catalyst significantly increases its surface area. The increased surface area allows a larger amount of gold to be exposed and thus improves the EB conversion and product selectivity. However, XRD did not detect the presence of copper and aurum in this catalyst, suggesting that the pore structure is still the dominant factor in the reactivity of this catalyst. This is supported by the fact that the calcined catalyst had a lower particle size distribution than the uncalcined catalyst. The size distribution of the particles increased as the concentration of gold increased, but the pore volume and the crystallinity of the zeolite did not change. The calcination of the zeolite also improved the overall conversion of EB by increasing the selectivity to styrene. The SEB-08 catalyst is currently being tested in a styrene plant and is expected to be available for commercial production.
Tags:palladium catalyst | zeolite catalyst
