Alkylation—Heterogeneous

Abstract

Alkylate or alkylation gasoline is produced by reacting isobutane with light olefins, generally the C 3 –C 4 cut from catalytic cracking (FCC) units, in the presence of a strong acid catalyst. The alkylate product is mostly composed of a mixture of high octane isoparaffins being almost free of sulfur, olefins, and aromatics, thus making it a valuable component of reformulated gasoline. Unfortunately, today's commercial alkylation processes rely on the use of noxious HF and H 2 SO 4 liquid acids as catalysts and this imposes serious limitations, especially in the case of HF‐catalyzed processes, to expanding the worldwide alkylation capacity to the levels one might ideally envisage. This prompted to an intensive research work in the past 30 years in both academy and industry looking for alternative environment friendly solid acid catalysts that overcome the limitations of the current alkylation technologies. Since then, different types of solid acids, among which zeolites have deserved particular attention, have been investigated leading to outstanding advances in both catalyst and process design as well as in fundamental knowledge (nature of active sites, mechanism, etc.) that allowed several solid acid alkylation technologies being, at present, offered for commercialization. Unfortunately, refiners are still reluctant to assume the economic risks associated with the installation of a new alkylation technology, even if competitive, unless tighter environmental regulations become operational. In this article, the latest achievements in the use of green solid acid catalysts as potential alkylation catalysts are reviewed. After a short introduction, the main features of the different solid acids so far studied, including supported Brønsted and Lewis acids, acid resins both supported and unsupported, zeolites, sulfated and tungstated transition metal oxides, and heteropolyacids and related materials, in the alkylation reaction are addressed. Although they cannot be considered as true solid acids, the potential of ionic liquids as alkylation catalysts is also discussed. Finally, a brief description of the different solid acid alkylation processes so far developed is included, with special emphasis on the catalyst and reactor designs.

New Insights into the Progress on the Isobutane/Butene Alkylation Reaction and Related Processes for High-Quality Fuel Production. A Critical Review

“…It also implies a high consumption of water that must be treated to eliminate the remaining hydrocarbons and higher refrigeration costs. 114 In recent decades, ionic liquids (ILs) have been widely explored as catalyst alternatives to obtain alkylation gasoline. This section will review the characteristics and properties of the ILs and their potential as alternatives for application to the alkylation reaction.…”

“…Although the process is less efficient than using HF, a large amount of catalyst is required (70–100 kg to obtain 1 ton of alkylate) and the yield of TMPs is lower. It also implies a high consumption of water that must be treated to eliminate the remaining hydrocarbons and higher refrigeration costs . In recent decades, ionic liquids (ILs) have been widely explored as catalyst alternatives to obtain alkylation gasoline.…”

Hydride Transfer versus Deprotonation Kinetics in the Isobutane–Propene Alkylation Reaction: A Computational Study

“…Acid-catalyzed alkylation of isobutane with light alkenes is one of the cornerstone technologies to produce high-octane gasoline in petroleum refineries. , The main challenge to the alkylation chemistry is to develop a solid acid catalyst for this process, which can compete with current highly optimized technologies based on liquid mineral acids such as HF and H 2 SO 4 . A wide range of solid acids has been investigated, including supported Brønsted and Lewis acids, exchange resins, zeolites, sulfated transition-metal oxides, and heteropolyacids and their derivatives. , Ionic liquids, although not true solid acids, have also been explored for the development of greener alkylation processes .…”

Effective and Intrinsic Kinetics of the Two-Phase Alkylation of i-Paraffins with Olefins Using Chloroaluminate Ionic Liquids As Catalyst

“…The alkylation of i-paraffins with light olefins (e.g., 1- and 2-butene with i-butane) forming highly branched paraffins (e.g., 2,2,4-trimethylpentane) is an important refinery process since the products of this reaction provide a high octane number and can be considered to be free of sulfur and aromatics. , In the future, the importance of alkylation may even grow: Catalytic reforming of heavy naphtha, which is today still the most important process for high octane gasoline production, yields a gasoline rich in aromatics, but their content in gasoline for sale is more and more limited. Hence, processes like alkylation and isomerization may become increasingly important.…”