Abstract
The growing demand for isobutane as a vital petrochemical feedstock and chemical intermediate has for many decades surpassed industrial outputs that can be supplied through liquified petroleum gases. Alternative methods to resource the isobutane market have been explored, primarily the isomerization of linear n-butane to the substituted isobutane. To date the isobutane market is valued at over 20 billion US dollars, enticing researchers to seek unique and novel catalytic materials to improve on current commercial practices. Two main classes of catalysts have dominated the butane isomerization literature in the last few decades; namely microporous zeolites and sulfated zirconia. Both have been widely researched for butane isomerization, to the point where key catalytic descriptors such as acidity, framework topology and metal doping are becoming well understood. While this provides new researchers with a roadmap for developing new materials, it is has also begun developing into an invaluable tool for diagnosing and understanding the effect of these individual descriptors on catalytic properties. In this review we explore the different factors that influence the active site behavior of particularly zeolites and sulfated zirconia catalysts towards understanding the use of butane isomerization as a diagnostic tool for solid-acid catalysts.
Highlights
The growing demand for isobutane as a vital petrochemical feedstock and chemical intermediate has for many decades surpassed industrial outputs that can be supplied through liquified petroleum gases
Thanks to the in-depth understanding afforded from the mechanistic studies of butane isomerization in these prior works, n-butane isomerization represents a diagnostic tool for understanding solid-acid catalyst characteristics, leading to the development of generalized structure-property relationships for a range of acidic materials [34]
Butane isomerization has been shown to be highly responsive to active site structural descriptors within zeolite frameworks, which may alter the selectivity between the mono- and bi-molecular mechanism
Summary
Liquified petroleum gas (LPG) is a vital and growing industry, used globally as household fuels, motor fuel additives and as a replacement refrigerant for CFCs. The monomolecular pathway is initiated by protonation of n-butane, by Brønsted acid sites (BAS), leading to a secondary carbonium ion, which undergoes dehydrogenation to yield a secondary carbenium ion [26,27,28,29] In some cases, these positively charged intermediates can be stabilized by oxygen atoms in the framework, yielding alkoxide species [30]. The need to form butene in situ for this pathway, is one of the reasons why many industrial catalysts (Table 1) are bifunctional, containing both acidic and noble metal species [20] Once formed these C8 intermediates can undergo either even scission, leading to isomerization, or uneven scission leading to disproportionation. Thanks to the in-depth understanding afforded from the mechanistic studies of butane isomerization in these prior works, n-butane isomerization represents a diagnostic tool for understanding solid-acid catalyst characteristics, leading to the development of generalized structure-property relationships for a range of acidic materials [34]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
