Modeling of the simulated countercurrent moving-bed chromatographic reactor used for the oxidative coupling of methane

The oxidative coupling reaction of methane (OCM) is a potential industrial reaction for the efficient production of ethylene. Replacement of current technologies requires significant product yield improvements. An experimental novel reactor design, the modified simulated countercurrent moving-bed chromatographic reactor (SCMCR), has reported improved ethane and ethylene product yields over other reported values. An understanding of the reactor operation is aided by concurrent mathematical modeling. The model mimics the exact experimental reactor configuration. Four sections are used; each section contains a reaction column and two separation columns connected in series. The feed is switched from section to section at discrete intervals. Reaction occurs in the first column and is followed by product and reactant separation in the ensuing section columns. Langmuir adsorption isotherms are used. The model does not incorporate the realistic and complex kinetics rising, from the OCM, rather a simplified reaction term is used to qualitatively gain insight into the operation of the modified SCMCR. A unimolecular reaction network is used in the model. The rate constants are set to permit a small fractional conversion, 5% per pass, at the concentrations during the first cycle. Similarly to the experimental reactor, the model adds a make-up feed (defined as percentage of the original feed, where excess methane is fed during the first cycle of the experimental reactor) to augment lost reactants

Microstructured catalytic hollow fiber reactor for methane steam reforming

Microstructured alumina hollow fibers, which contain a plurality of radial microchannels with significant openings on the inner surface, have been fabricated in this study and used to develop an efficient catalytic hollow fiber reactor. Apart from low mass-transfer resistance, a unique structure of this type facilitates the incorporation of Ni-based catalysts, which can be with or without the aged secondary support, SBA-15. In contrast to a fixed bed reactor, the catalytic hollow fiber reactor shows similar methane conversion, with a gas hourly space velocity that is approximately 6.5 times higher, a significantly greater CO2 selectivity, and better productivity rates. These results demonstrate the advantages of dispersing the catalyst inside the microstructured hollow fiber as well as the potential to reduce the required quantity of catalyst

Impact of catalysis on the production of the top 50 US commodity chemicals

Information on each chemical is stored in an accompanying Excel{trademark} 4.0 spreadsheet (``top5Ochem.xcl``). This analysis tool allows the user to make assumptions about process yield improvements and evaluate the corresponding impact on the process and feedstock energy. Many scenarios have been investigated and are reported in the text. If all of the catalytic processes associated with the top 50 chemicals were raised to their maximum process yields, the corresponding process and feedstock energy savings would exceed 0.47 quads per year. More realistic process yield improvements of 1%, 5%, and 10% where possible, would save 0.03, 0.14, and 0.23 quads per year. Many of the commodity chemicals face limitations from both the current catalyst and process. Catalysis is vital, but catalysis alone is not the answer to maximizing energy savings. Integration of catalysis development with process engineering research can lead to significant energy savings during the production of the top 50 chemicals

The top 50 commodity chemicals: Impact of catalytic process limitations on energy, environment, and economics

The production processes for the top 50 U.S. commodity chemicals waste energy, generate unwanted byproducts, and require more than a stoichiometric amount of feedstocks. Pacific Northwest Laboratory has quantified this impact on energy, environment, and economics for the catalytically produced commodity chemicals. An excess of 0.83 quads of energy per year in combined process and feedstock energy is required. The major component, approximately 54%, results from low per-pass yields and the subsequent separation and recycle of unreacted feedstocks. Furthermore, the production processes, either directly or through downstream waste treatment steps, release more than 20 billion pounds of carbon dioxide per year to the environment. The cost of the wasted feedstock exceeds 2 billion dollars per year. Process limitations resulting from unselective catalysis and unfavorable reaction thermodynamic constraints are the major contributors to this waste. Advanced process concepts that address these problems in an integrated manner are needed to improve process efficiency, which would reduce energy and raw material consumption, and the generation of unwanted byproducts. Many commodity chemicals are used to produce large volume polymer products. Of the energy and feedstock wasted during the production of the commodity chemicals, nearly one-third and one-half, respectively, represents chemicals used as polymer precursors. Approximately 38% of the carbon dioxide emissions are generated producing polymer feedstocks

Indirect liquefaction of biomass: A fresh approach

Indirect liquefaction of biomass is accomplished by first gasifying it to produce a synthesis gas consisting of hydrogen and oxides of carbon, which in turn are converted to any one of a number of liquid fuels and/or chemicals by suitable choice of catalyst, synthesis gas composition and reaction conditions. This approach to producing synthetic fuels and chemicals has been extensively investigated where coal is the carbonaceous feed material, but less so for biomass or other feedstocks. It is generally recognized that the gasification to produce the synthesis gas posses one of the major technical and economic challenges to improving this technology. Herein, is reported a different slant on the indirect liquefaction that could lead to improvements in the efficiency and economics of the process

Advanced Emulsions: Enabling Advanced Emulsion With Microchannel Architecture

An innovative emulsification technology that produces modern emulsions at a reasonable cost has been demonstrated. This process is useful for producing conventional emulsions, and so-called surfactant free emulsions, which are stabilized by particles and/or amphipathic polymers. Such emulsions present significant formulation and processing challenges because conventional emulsification techniques rely upon shear force to break up the droplets formed by the discontinuous phase and to transport the emulsifier to the interface. Microchannel emulsification technology is unlike traditional methods that use high-shear forces to form small droplets. This technology, which consists of intervening microchannels with apertured substrates, adds the discontinuous to the continuous phase, one droplet at a time, and provides better control than conventional methods. The droplet size distribution is controlled by adjusting critical process parameters (mixing energy, mixing time), and precise heating and/or cooling