Electrical Oligomerization of Small Hydrocarbons Activated by Collision with High Energy Electrons at Ambient Conditions

Abstract

Isomerization and polymerization are two essential chemical processes that produce valuable chemicals and high quality fuels. However, they hardly occur at ambient conditions due to the activation energy barrier of multiple chemical reactions. Thermal activation of those reactions by catalysts or high temperature and pressure or both are very costly and emits a vast amount of greenhouse gases (GHG). Here, we show a greener method that uses electricity and high energy electrons to efficiently activate small molecules at ambient conditions. Activated fragments and radicals cross-link and produce larger and more valuable compounds without use of any catalysts. One small hydrocarbon (C5H12) was irradiated by a high energy electron beam at the liquid state. About 5% conversion, iso-paraffin (85%) and n-paraffin (15%), in a C6–C15 range was observed using 400 kJ/kg energy input (0.8% of pentane’s energy content). We propose that collisions between high energy electrons and small molecules at the liquid state create radicals very efficiently by nonselective cleavage of carbon–carbon and carbon–hydrogen bonds. Radicals then undergo random pairing reactions and selectively produce large branched species. The energy cost of this method is comparable with thermal methods. This method is electrical and easily adaptable to renewable energy sources with potentially zero GHG emissions.

Electric production of high-quality fuels via electron beam irradiation under ambient conditions

“…The product pattern was successfully modeled by a random second order pairing reaction mechanism in our previous paper. 27 The mass distribution of each carbon group in the C 6 -C 10 range was also studied and compared to the simulated results. The mass distribution of paraffin isomers at each carbon group was quantified.…”

“…A statistical model used to predict product distribution was developed in our previous paper. 27 A brief description of the modeling and simulation approach is that it assumes equal probability dissociation of all carbon-carbon and carbonhydrogen bonds for all saturated hydrocarbons, and then allows for free pairing of radicals resulting from molecule dissociation. The model describes the statistics of the type of distribution.…”

“…Products are generated via free pairing reactions of a series of alkane radicals with different chain lengths. Bond rupture pathways and pairing reactions among different radicals are explained in detail in our previous paper 27 and ESI Scheme S1. † When cyclohexane was irradiated by the ebeam, electron impact induced dissociation occurs at all bonds.…”

“…Liquid pentane was converted to branched paraffins which could serve as high quality fuels. 27 Heavy oils upon irradiation converted to gasoline and diesel range fuels via cracking. 25 Clearly, both polymerization and cracking could be activated by ebeam.…”