Hydrocracking of Polyethylene to Jet Fuel Range Hydrocarbons over Bifunctional Catalysts Containing Pt- and Al-Modified MCM-48

Yanyong Liu

doi:10.3390/reactions1020014

Abstract

A low-density polyethylene was hydrocracked to liquid hydrocarbons in autoclave reactors over catalysts containing Pt- and Al-modified MCM-48. Two kinds of Al-modified MCM-48 were synthesized for the reaction: Al-MCM-48 was synthesized using a sol–gel method by mixing Al(iso-OC3H7)3 with Si(OC2H5)4 and surfactant in a basic aqueous solution before hydrothermal synthesis, and Al/MCM-48 was synthesized using a post-modification method by grafting Al3+ ions on the surface of calcined Al/MCM-48. X-ray diffraction (XRD) patterns indicated that both Al-MCM-48 and Al/MCM-48 had a cubic mesoporous structure. The Brunauer–Emmett–Teller (BET) surface areas of Al-MCM-48 and Al/MCM-48 were larger than 1000 m2/g. 27Al Magic Angle Spinning-NMR (MAS NMR) indicated that Al3+ in Al-MCM-48 was located inside the framework of mesoporous silica, but Al3+ in Al/MCM-48 was located outside the framework of mesoporous silica. The results of ammonia temperature-programmed desorption (NH3-TPD) showed that the acidic strength of various samples was in the order of H-Y > Al/MCM-48 > Al-MCM-48 > MCM-48. After 4 MPa H2 was charged in the autoclave at room temperature, 1 wt % Pt/Al/MCM-48 catalyst showed a high yield of C9−C15 jet fuel range hydrocarbons of 85.9% in the hydrocracking of polyethylene at 573 K for 4 h. Compared with the reaction results of Pt/Al/MCM-48, the yield of light hydrocarbons (C1−C8) increased over Pt/H-Y, and the yield of heavy hydrocarbons (C16−C21) increased over Pt/Al-MCM-48 in the hydrocracking of polyethylene. The yield of C9−C15 jet fuel range hydrocarbons over the used catalyst did not decrease compared to the fresh catalyst in the hydrocracking of polyethylene to jet fuel range hydrocarbons over Pt/Al/MCM-48.

Highlights

The consumption of fossil fuels in transportation causes an increase of total CO2 emission in the world
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Pt/MCM-48 showed a low total C1–C22 yield of 7.1% after reaction at 573 K for 4 h. Both Pt/Al-MCM-48 and Pt/Al/MCM-48 showed high total C1–C22 yields and formed C9–C15 jet fuel range hydrocarbons as the main products after reaction at 573 K for 4 h. These results indicate that the solid acid sites are important for the hydrocracking of polyethylene over Pt-loaded catalysts

Summary

Introduction

The consumption of fossil fuels in transportation causes an increase of total CO2 emission in the world. The use of biomass-derived fuels (called biofuels) instead of fossil fuels is an effort to decrease CO2 emissions because the biomass absorbs CO2 during the growth process [1]. Bioethanol and biodiesel (fatty acid methyl esters) are the main transportation biofuels produced in the world at present [2,3]. These oxygen-containing biofuels are not suitable for current jet engines, which have been designed using hydrocarbons as fuel. Biofuels with a chemical composition of hydrocarbons (called drop-in biofuels) have been researched because they are suitable for the current engines. Biomass-to-liquid fuel (BTL) and hydrotreatment processes are the main methods for producing drop-in biofuels at present. In the BTL process, the woody biomass is converted to syngas by gasification, and the formed syngas is converted to mixed hydrocarbons by Fisher-Tropsch (F-T)

Methods

Results

Conclusion