Selective oligomerization of isobutylene in mixed C₄ catalyzed by supported Fe(NO₃)₃/β catalyst

Abstract

BACKGROUND Methyl tert‐butyl ether (referred to as MTBE) is harmful to the environment and hence its use is limited in China. To avoid the waste of isobutylene as MTBE raw material and improve the utilization rate of isobutylene in mixed C4 fraction, supported Fe(NO3)3/β molecular sieve catalysts with different active components were prepared by the equal volume impregnation method. The catalysts were analyzed by X‐ray diffraction (XRD), Thermogravimetric analysis (TG), Temperature programmed desorption of NH3, Brunauer–Emmett–Teller analysis and scanning electron microscopy, and the catalytic performance of catalysts with mixed C4 fractions as raw materials and different active component loadings for selective oligomerization of isobutylene was investigated in a fixed bed reactor. RESULTS The results show that the catalyst has the best catalytic performance when the active component loading was 6%, the reaction temperature was 60 °C, the reaction pressure was 1 MPa and the reaction space velocity was 1.5 h−1. CONCLUSION The conversion rate of isobutylene was >90%, the selectivity of C8 olefin was ≈80% and there was almost no loss of n‐butene. © 2021 Society of Chemical Industry (SCI).

Supported Metal Sulfate Catalysts FexZny/SiO2 for Selective Dimerization of Isobutene in Mixed C4 to Isooctenes

“…Zn 2.0 /SiO 2 exhibits a better isobutene conversion than Fe 2.0 /SiO 2 , Fe 1.0 /SiO 2 , and Fe 1.0 Zn 1.0 /SiO 2 , suggesting that weak Lewis acid Zn 2+ is milder and propitious to stable conversion. The Fe 2+ species may play an important role in C 8 = selectivity because it can prevent chain growth and favor the formation of dimers with easy‐to‐lose electrons [27] . During the catalytic process, isobutene molecules are absorbed and carbocations are formed on Brönsted or Lewis acid sites (Scheme 1), then Fe 2+ inhibits the carbon chain growth to afford C 8 = , leading to a significant improvement in dimer selectivity.…”

“…Zn 2.0 /SiO 2 exhibits a better isobutene conversion selectivity because it can prevent chain growth and favor the formation of dimers with easy-to-lose electrons. [27] During the catalytic process, isobutene molecules are absorbed and carbocations are formed on Brönsted or Lewis acid sites (Scheme 1), then Fe 2 + inhibits the carbon chain growth to afford C 8 = , leading to a significant improvement in dimer selectivity.…”

Effect of ethanol on selective oligomerization of isobutene and the simulation of reactive distillation process

“…The specific preparation method can be found in previous literature. 21,33 Based on the preparation methods and performance evaluation of the catalysts in the literature, we selected two supported β molecular sieve catalysts. The first catalyst is a Fe 2 O 3 -N/β molecular sieve catalyst with a ferric nitrate impregnation amount of 6% and a calcination temperature of 550 C. The second catalyst is a Fe 2 O 3 -Cl/β molecular sieve catalyst with a ferric chloride impregnation amount of 3% and a calcination temperature of 550 C.…”

“…Traditional liquid catalysts such as HF or H 2 SO 4 9,10 have been eliminated due to their ability to corrode equipment and cause pollution. In recent years, various solid acid catalysts have emerged, such as sulfated titanium dioxide, 11,12 modified sulfate zirconia, 5,13 ion-exchange resin, 3,14-17 modified molecular sieve, [18][19][20][21] heteropolyacid, 22,23 and metal-organic frameworks (MOFs). [24][25][26] These modified catalysts change the acid content of the catalyst, generate C 8 olefins through Bronsted acid sites or Lewis acid sites, and improve selectivity.…”

“…The catalysts were selected from two supported β molecular sieve catalysts that were previously studied. 21,33 The isobutene oligomerization reaction was simulated and optimized using the reactive distillation process. Sensitivity analysis was conducted on operating parameters such as reflux ratio, the number of theoretical plates in the column, and feeding position to obtain the optimal operating parameters.…”