A review of recent advances on process technologies for upgrading of heavy oils and residua

Alternatives to petroleum-derived fuels and chemicals are being sought in an effort to improve air quality and increase energy security through development of novel technologies for the production of synthetic fuels and chemicals using renewable energy sources such as biomass. In this context, ethanol is being considered as a potential alternative synthetic fuel to be used in automobiles or as a potential source of hydrogen for fuel cells as it can be produced from biomass. Renewable ethanol can also serve as a feedstock for the synthesis of a variety of industrial chemicals and polymers. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, especially those containing six carbons, whereas 5-carbon sugars and lignin, which are also present in the biomass, remain unusable. Gasification of biomass to syngas (CO + H2), followed by catalytic conversion of syngas, could produce ethanol in large quantities. However, the catalytic conversion of syngas to ethanol remains challenging,...

A Review of Recent Literature to Search for an Efficient Catalytic Process for the Conversion of Syngas to Ethanol

The review is a summary and analysis of the data characterizing CO adsorption on surface cationic sites of oxides including supported materials and microporous and mesoporous materials. The contributions of various types of CO bonding to the IR frequency shifts of carbon-bonded molecules are analyzed, namely, the increase of the CO stretching frequency in cases of electrostatic and σ bonding and the decrease of the frequency with π bonding. Polycarbonyls, bridging CO, oxygen-bonded CO, and tilted CO are also considered. The main part of the review is a collection of the experimental results characterizing carbonyls of individual metal ions. The spectral behavior of CO bonded to metal atoms is also assessed in the cases when the metal ions are easily reduced to metal (Cu, Ag, Au, Pd, or Pt) or cationic carbonyls are produced after CO adsorption on supported metals (Ru, Rh, Ir, and Os). The interaction of CO with surface OH groups is also considered. It is demonstrated that IR spectroscopy of adsorbed CO is an efficient methodology to characterize cationic surface sites in terms of their nature, oxidation states, coordination environment and coordinative unsaturation, and location at faces, edges or corners of microcrystallites. When applied to materials with surface hydroxyl groups CO undergoes hydrogen bonding and information can be collected on the proton acid strength.

Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule

Recent developments on particle formation from polymers using supercritical fluids have been reviewed with an emphasis on articles published during 2000–2003. First, a brief description of the basic operating principles of the various particle formation processes is presented. These include the rapid expansion of supercritical solutions (RESS), the gas antisolvent process (GAS), supercritical antisolvent process (SAS) and its various modifications, and the particles from gas-saturated solution (PGSS) processes. An account of the general review articles that have been published in previous years is then provided. The publications that have appeared over the past 4 years have been reviewed under two groupings, one involving the production of particles from pure polymers, and the other involving the production of polymer particles that contain active ingredients, especially those that pertain to pharmaceuticals. The majority of the efforts in the current supercritical particle formation technology is indeed on the production of polymer particles that are of pharmaceutical significance. In each grouping, the publications were further categorized according to the primary role played by the supercritical fluid in the process, namely whether it was used as a solvent, or as an antisolvent, or as a solute. This review is the first comprehensive review specifically focused on the formation of particles from polymers.

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Formation of polymer particles with supercritical fluids: A review

The thermal and catalytic processes of converting waste plactics into fuels are promising techniques to eliminate the refuse which otherwise is harmful to the enivironment, and decrease the dependence on fossil fuels. Thermal degradation decomposes plastic into three fractions: gas, crude oil, and solid residue. Crude oil from non-catalytic pyrolysis is usually composed of higher boiling point hydrocarbons. The optimization of conversion parameters such as the choice of catalyst, reactor design, pyrolysis temperature, and plastic-to-catalyst ratio plays a very important role in the efficient generation of gasoline and diesel grade fuel. The use of a catalyst for thermal conversion lowers the energy required for conversion, and the catalyst choice is important for efficient fuel production. The suitable selection of catalysts can increase the yield of crude oil with lower hydrocarbon content. Co-pyrolysis of plastics with coal or shale oil improves crude oil quality by decreasing its viscosity. A large number of publications have appeared on various processes, and continued improvements and/or innovations are expected in the future. Further investigations on the catalytic systems are required in order to advance the field, particularly to enhance the added value of fuels and to minimize the use of energy. This review aims to provide both the highlights of the remarkable achievements of this field and the milestones that need to be achieved in the future.

Plastics to fuel: a review

An extensive infrared investigation of the CO/Rh/Al2O3 system has revealed the presence of eight different CO/Rh species including two which have not been observed previously. It has been shown that Rh loading on an alumina support is more critical than reduction temperature in effecting infrared spectral changes in the 1800–2200 cm−1 region. The oxidation state of Rh for the various CO/Rh species has been discussed; it has been postulated that for several of the species the oxidation state of Rh is greater than O. Furthermore, this work indicates that there is significant atomic dispersion on Rh/Al2O3 catalysts prepared from RhCl3⋅3H2O/Al2O3 by a procedure described originally by Yang and Garland. These catalysts retain appreciable amounts of chlorine even following hydrogenation at 673 K.

The oxidation state of dispersed Rh on Al2O3

Effect of reaction parameters and catalyst type on waste plastics liquefaction and coprocessing with coal

The effect of support material on Rh/X catalysts has been studied by using CO as a probe molecule for chemisorption and ir spectroscopy as the analytical method. Support materials including TiO/sub 2/, Al/sub 2/O/sub 3/, SiO/sub 2/, kaolinite, and montmoroillonite have been compared as to their tendencies to produce the various CO/RH/X species generally attributed to this catalytic system. The TiO/sub 2/ and SiO/sub 2/ supports enable the most facile reduction of a rhodium precursor material to rhodium metal. Although all of the Rh/X catalysts contain some Rh(I) sites, alumina-supported ones contain the most nonmetallic rhodium. Kaolinite and montmorillonite may contain impurities which tend to poison the Rh sites for CO chemisorption. The CO/Rh/SiO/sub 2/ infrared bands are much less intense than for alumina- or titania-supported rhodium. This is probably due to weak metal/support interaction for Rh/SiO/sub 2/ because the silica employed was of high purity. 3 figures.

Effect of support material on rhodium catalysts

The infrared spectra of the CO/Rh/Al2O3 system have been examined following several different means of preparing the supported rhodium catalyst. Rhodium precursor materials including RhCl3 ⋅ 3H2O, Rh(NO3)3 ⋅ 2H2O, Rh6(CO)16, [Rh(OCOCH3)2]2, and Rh2(SO4)3 have been compared as to their tendencies to produce upon reduction the various CO/Rh/Al2O3 species generally attributed to this catalytic system. The nitrate and carbonyl precursors are most easily reduced to rhodium metal. The acetate and sulfate anions poison the Rh/Al2O3 surface through decomposition during reduction leading to very minimal CO adsorption. The catalytic properties of Rh/Al2O3 could be quite dependent upon the nature of rhodium precursor chosen.

Christine W. Curtis

Papers

The oxidation state of dispersed Rh on Al2O3

Effect of reaction parameters and catalyst type on waste plastics liquefaction and coprocessing with coal

Effect of support material on rhodium catalysts

The effect of rhodium precursor on Rh/Al2O3 catalysts

Thermal and catalytic coprocessing of Illinois No. 6. coal with model and commingled waste plastics