Advancement of Fischer‐Tropsch synthesis via utilization of supercritical fluid reaction media

Abstract

in Wiley InterScience (www.interscience.wiley.com).The Fischer Tropsch Synthesis (FTS) reaction has been studied and for nearly a century for the production of fuels and chemicals from nonpetroleum sources. Research and utilization have occurred in both gas phase (fixed bed) and liquid phase (slurry bed) operation. The use of supercritical fluids as the reaction media for FTS (SCF-FTS) now has a 20-year history. Although a great deal of progress in SCF-FTS has been made on the lab scale, this process has yet to be expanded to pilot or industrial scale. This article reviews the research activities involving supercritical Keywords: Fischer-Tropsch synthesis, supercritical fluids, reaction engineering, cobalt catalyst, iron catalyst, ruthenium catalyst Introduction to supercritical fluids for catalysisThe concept of using supercritical fluids (SCFs) as solvents has been in circulation since their discovery in the nineteenth century.1 Industrial utilization of SCFs has received considerable attention since the early 1980s, starting with the development of technologies for extraction of commodity chemicals and fuels.2 By the mid 1980s, research on new applications of SCFs shifted toward more complex and valuable substances that undergo a much broader range of physical and chemical transformations.2 A great deal of research activities have taken place in studies of reactions, separations, and materials processing of polymers, foods, surfactants, pharmaceuticals, and hazardous wastes.3 SCFs are recognized as a unique medium for chemical reactions, offering single phase operation, a density that is sufficient to afford substantial dissolution power, a higher diffusivity, and lower viscosity than in liquids. These properties can result in significant enhancement of mass transfer and/or heat transfer. Additionally, conducting chemical reactions at near-critical conditions affords excellent opportunities to tune the reaction environment (solvent properties) through modest changes in temperature and pressure. These properties can help to eliminate transport limitations on reaction rates, integrate reaction and product separation processes, 4 and enhance in situ extraction of low volatility products (e.g., heavy hydrocarbons) from porous catalysts. 5The main areas of heterogeneously catalyzed hydrogenation reactions were classified by Hyde et al. 6 according to the following categories: (1) the hydrogenation of food compounds such as fatty acids or oils to produce higher value derivatives; (2) the formation of precursor building blocks for pharmaceuticals and fine chemicals, and (3) asymmetric hydrogenation. In their book, McHugh and Krukonis, 2 address the uniqueness of applying a supercritical medium to many of the above classes of heterogeneous reactions, as well as to homogenous reactions such as selective oxidations, hydrogenations, hydroformylations, alkylations, and

Monte Carlo simulations of phase behavior and microscopic structure for supercritical CO2 and thiophene mixtures

“…Due to the ability to uniformly change from vapor-like to liquidlike densities, supercritical fluids (SCFs) act as powerful solvents and their properties can be tuned easily by changing the temperature or pressure or by addition of co-solvents [6][7][8]. Owing to these excellent properties, SCFs are used as solvents in a wide range of applications such as chemical reactions, extractions, and cleaning processes [9,10]. Supercritical CO 2 (ScCO 2 ) is potentially an environmentally benign solvent with nontoxic and nonflammable characteristics and has readily accessible critical temperature of 304.3 K and moderate critical pressure of 73.8 bar [11,12].…”

Investigation of Supercritical Isooctane as a Reaction Medium in the Conversion of Methanol to Hydrocarbons over H-ZSM-5

“…Between 4 and 24 h TOS, the suppression in light olefin and paraffin selectivity under SC MTH conditions compared to GP MTH is attributed to the lower methanol conversion to hydrocarbons observed in the presence of supercritical isooctane ( Figure 2). The appearance of DME in the initial product distribution may be due to the extractive effects of the SCF medium, 12 which can remove primary products, such as DME, from the catalyst surface before they can undergo subsequent conversion. Although DME breakthrough occurs earlier in SC MTH than in GP MTH, the appearance of DME in the product distribution is not accompanied by an abrupt drop in methanol conversion, as was observed for GP MTH at 370°C.…”

Modeling the Fixed-Bed Fischer-Tropsch Reactor in Different Reaction Media

“…This work represents a first step towards developing a comprehensive model for FTS capable of accounting for the presence of different reaction media such as supercritical fluid (SCF) solvents, which have been shown to provide several advantages over operation in the conventional gas-phase FTS (Elbashir et al 2010). We attempt to validate the model under typical gas-phase FTS conditions using experimental data generated from our high-pressure FTS reactor unit.…”