Comparative Study of Different Acidic Surface Structures in Solid Catalysts Applied for the Isobutene Dimerization Reaction

Abstract

Dimerization of isobutene (IBE) to C8s olefins was evaluated over a range of solid acid catalysts of diverse nature, in a fixed bed reactor working in a continuous mode. All catalytic materials were studied in the title reaction performed between 50–250 °C, being the reaction feed a mixture of IBE/helium (4:1 molar ratio). In all materials, both conversion and selectivity increased with increasing reaction temperature and at 180 °C the best performance was recorded. Herein, we used thermogravimetry analysis (TGA) and temperature programmed desorption of adsorbed ammonia (NH3-TPD) for catalysts characterization. We place emphasis on the nature of acid sites that affect the catalytic performance. High selectivity to C8s was achieved with all catalysts. Nicely, the catalyst with higher loading of Brønsted sites displayed brilliant catalytic performance in the course of the reaction (high IBE conversion). However, optimum selectivity towards C8 compounds led to low catalyst stability, this being attributed to the combined effect between the nature of acidic sites and structural characteristics of the catalytic materials used. Therefore, this study would foment more research in the optimization of the activity and the selectivity for IBE dimerization reactions.

Mechanism and Kinetics of Acetone Conversion to Isobutene over Isolated Hf Sites Grafted to Silicalite-1 and SiO2

“…Isobutene is an important chemical intermediate used to produce a broad range of products. These include octane blending components for gasoline (e.g., isooctane, methyl- tert -butyl ether (MTBE), and ethyl- tert -butyl ether (ETBE)), butyl rubber, methyl methacrylate, methacrolein, and acrylics. − The primary sources of isobutene today are steam cracking of naphtha, isomerization and dehydrogenation of petroleum-derived butane, and separation from the butane–butene fraction produced by catalytic cracking of petroleum. , However, growing concerns with global warming caused by the combustion of products derived from petroleum have motivated the search for routes to isobutene based on biomass as the starting material. − An attractive approach for doing so is the condensation of acetone, produced by the fermentation of glucose to a mixture of acetone, butanol, ethanol (so-called ABE fermentation) or the ketonization of acetic acid. If acetic acid produced as a byproduct of acetone condensation is converted back to acetone and CO 2 , the overall reaction for the synthesis of isobutene from acetone is This reaction is thermodynamically favorable (Δ G 298 o = −35 kJ/mol) and has a carbon utilization efficiency of 88.9%.…”

Recent Progress on Sulfated Nanozirconia as a Solid Acid Catalyst in the Hydrocracking Reaction

“…Sulfation with optimum sulfate concentration can increase the catalytic activity of the catalyst, while the decrease in catalyst acidity with increasing temperature occurs due to dehydration of protonic sites and loss of SO 4 2− groups on the surface of the catalyst [38][39][40]. Qualitatively, the number of Brønsted and Lewis acid sites can be observed absorption spectra intensity that denotes the interaction between the catalyst acid sites and NH 3 [41]. Figure 5 presents the FTIR spectra of the catalyst after the acidity test.…”

Zeolite-based catalysis for isobutene conversion into chemicals and fuel additives. A review

“…Dimerization is highly exothermic (∆H = −87.3 kJ/mol) and as a result, important side reactions, leading to iso-C 12 and iso-C 16 olefins, occur. Various solid acid materials including resins, zeolites, and metal oxides are effective catalysts for the isobutene dimerization [51][52][53]. In this section, representative dimerization studies performed on zeolites as catalysts will be examined.…”