Acetonitrile Synthesis via Ammoxidation: Mo/zeolites Catalysts Screening

Faouzi Ayari Faouzi Ayari,Gérard Delahay Gérard Delahay,Emna Mannei Emna Mannei,Esther Asedegbega-Nieto Esther Asedegbega-Nieto,Mourad Mhamdi Mourad Mhamdi

doi:10.37256/fce.112020117.16-30

Abstract

Mo/zeolites catalysts were investigated in ethane and ethylene ammoxidation into acetonitrile. The catalysts were prepared either in solid‒solid or liquid‒solid interface after varying different parameters. The stabilization of Mo species upon the exchange is dependent on the hydrophilic/hydrophobic character of the zeolite and the type of Mo precursor. In fact, zeolites with low Si/Al molar ratios should be avoided due to their higher dehydration enthalpy values (Δdehyd.H). On the other hand, the use of MoOCl4, Mo(CO)6 and MoCl3 precursors and zeolites with high Si/Al ratios led to inefficient [Mo7O24]6‒ species and amorphous MoO3 which catalyzes the combustion reaction. Nevertheless, the use of MoCl5, MoO3 and MoO2(C5H7O2)2 led to promising activities. In catalysis, [MoO4]2‒ species are required to activate C2H6 into C2H4, while [MoxO3x+1]2‒ (x =1, 2) species catalyze the ammoniation of C2H4 and the ethylamine dehydrogenation into CH3CN. Interestingly, active catalysts could be obtained by humid impregnation and a simultaneous oxidative treatment. Such a treatment improves the dispersion state of crystalline MoO3, which activate ethane molecules. It is judicious to perform C2H6 oxidative dehydrogenation before ammoxidation since the interference between the different investigated parameters could be noted.

Highlights

Will the world have enough ethane?According to the statistics, 80% of the global production of C2H6 comes from 10 nations
Ethylene is easier to convert into valuables liquids such as nitriles and the activation of C2H6 is a crucial step in the ethane-to-liquids technology
The samples were prepared by solid-state ion exchange (SSIE), which consists on grinding the zeolite and the Mo salt before being heated under a carrier gas from 30 to 500°C (2°C min–1) and kept isothermally for 12h at 500°C

Summary

Introduction

80% of the global production of C2H6 comes from 10 nations. Ethane is difficult to transport and ~660 Trillion BTU of this hydrocarbon is either rejected in the natural gas or flared, leading to a waste of valuable resources[1, 2]. Efforts were consented in the conversion of ethane to liquid hydrocarbons inside the natural gas deposits. Ethylene is easier to convert into valuables liquids such as nitriles and the activation of C2H6 is a crucial step in the ethane-to-liquids technology. Our group[3,4,5] has reported Mo/zeolites as efficient catalysts for ethane ammoxidation (Eq 1) into acetonitrile (AN). The reaction in Eq (1) is the sum of Eqs.

Objectives

Methods

Results

Discussion

Conclusion