Thermodynamic Equilibrium Analysis of Methanol Conversion to Hydrocarbons Using Cantera Methodology

Duminda A Gunawardena,Sandun D Fernando

doi:10.1155/2012/125460

Abstract

Reactions associated with removal of oxygen from oxygenates (deoxygenation) are an important aspect of hydrocarbon fuels production process from biorenewable substrates. Here we report the equilibrium composition of methanol-to-hydrocarbon system by minimizing the total Gibbs energy of the system using Cantera methodology. The system was treated as a mixture of 14 components which had CH3OH, C6H6, C7H8, C8H10 (ethyl benzene), C8H10 (xylenes), C2H4, C2H6, C3H6, CH4, H2O, C, CO2, CO, H2. The carbon in the equilibrium mixture was used as a measure of coke formation which causes deactivation of catalysts that are used in aromatization reaction(s). Equilibrium compositions of each species were analyzed for temperatures ranging from 300 to 1380 K and pressure at 0–15 atm gauge. It was observed that when the temperature increases the mole fractions of benzene, toluene, ethylbenzene, and xylene pass through a maximum around 1020 K. At 300 K the most abundant species in the system were CH4, CO2, and H2O with mole fractions 50%, 16.67%, and 33.33%, respectively. Similarly at high temperature (1380 K), the most abundant species in the system were H2 and CO with mole fractions 64.5% and 32.6% respectively. The pressure in the system shows a significant impact on the composition of species.

Highlights

Methanol is the simplest alcohol which has a tremendous importance as an industrial feedstock [1, 2]
Methanol conversion process in the industry has branched into two paths, namely, methanol to olefins (MTO) and methanol to gasoline (MTG)
The outcome of the optimization routine is the mole fraction of each of the fourteen compounds in the mixture at each pressure and temperature. Since it is a gas phase system, the partial pressure of each component is proportional to mole fraction and results are analyzed in those terms

Summary

Introduction

Methanol is the simplest alcohol which has a tremendous importance as an industrial feedstock [1, 2]. Catalyst upgrading to make deoxygenation reaction more selective toward gasoline products such as benzene, toluene, ethylbenzene, and xylene (BTEX) is one such approach [6, 7]. Another approach is to alter the reaction conditions such as temperature, pressure, and residence time to augment the desired product spectrum [6, 8]. For this purpose, understanding the energetics of the MTG reaction pathway by thermodynamic analysis is an important step. Process consists of a mixture of paraffins, aromatics, and olefins, and for the thermodynamic system, are treated as equilibrium products in this analysis

Thermodynamic Equilibrium Analysis

Results and Discussion

Conclusions