Savvas Vasileiadis

The enhancement of reaction yield through the use of high temperature membrane reactors

Abstract Membrane reactors combine reaction and separation in a single unit operation, the membrane selectively removing one or more of the reactant or product species. Most commonly these reactors have been used with reactions, whose yields are limited by thermodynamic equilibrium. For such reactions, membrane reactors seem to offer potential advantages over more traditional reactors. Membrane reactors have also been proposed for other applications; for increasing the yield of enzymatic and catalytic reactions by influencing, through the membrane, the concentration of various intermediate species; for selectively removing species, which would otherwise poison or deactivate the reaction; and for providing a controlled interface between two or more reactant species. Membrane reactors are currently being tested with a number of catalytic reactions. Reactions studied by our group include catalytic dehydrogenation of ethane, and methane steam reforming. Theoretical models have also been developed for these re...

ALTERNATIVE GENERATION OF H2, CO AND H2, CO2 MIXTURES FROM STEAM-CARBON DIOXIDE REFORMING OF METHANE AND THE WATER GAS SHIFT WITH PERMEABLE (MEMBRANE) REACTORS

Abstract A new process is proposed which converts CO2 and CH4 containing gas streams to synthesis gas, a mixture of CO and H2 via the catalytic reaction scheme of steam-carbon dioxide reforming of methane or the respective one of only carbon dioxide reforming of methane, in permeable (membrane) reactors. The membrane reformer (permreactor) can be made by reactive or inert materials such as metal alloys, microporous ceramics, glasses and composites which all are hydrogen permselective. The rejected CO reacts with steam and converted catalytically to CO2 and H2 via the water gas shift in a consecutive permreactor made by similar to the reformer materials and alternatively by high glass transition temperature polymers. Both permreactors can recover H2 in permeate by using metal membranes, and H2 rich mixtures by using ceramic, glass and composite type permselective membranes. H2 and CO2 can be recovered simultaneously in water gas shift step after steam condensation by using organic polymer membranes. Produc...

Environmentally benign hydrocarbon processing applications of single and integrated permreactors

Publisher Summary This chapter investigates the methane-steam reforming and the propane dehydrogenation reaction in various catalytic inorganic permreactors. The proposed permreactors can be beneficially used as reactant or product recycling and distributing devices. Enhanced conversions and yields can be achieved for various types of permreactor operation for the methane steam reforming and propane dehydrogenation. The chapter also presents new process designs employed for steam hydrocarbon reforming, the water gas shift, and paraffin dehydrogenation in inorganic, metal, and organic-polymer permreactors and permeators. These constitute the basis for designing improved, environmentally benign, integrated hydrocarbon upgrading, and in situ CO 2 abatement systems for hydrogen, H 2 –CO 2 , synthesis gas, and hydrogen rich hydrocarbon generation. The permeated or combined product gases can be utilized inline for synthesis or as feed in molten carbonate and other types of hydrogen based fuel cells, and in power generation systems. In the case of a dehydrogenator, rejected olefin streams such as propylene, ethylene, and n/i-butene can be used for polymer production or in other chemical synthesis.

REACTOR-MEMBRANE PERMEATOR CASCADE FOR ENHANCED PRODUCTION AND RECOVERY OF H2 AND CO2 FROM THE CATALYTIC METHANE-STEAM REFORMING REACTION

The catalytic reforming of methane by steam is an important industrial process that produces H2, CO and CO2, thus chemically transforming natural gas, coal gas and light hydrocarbon feedstocks to synthesis gas or hydrogen fuel. Methane-steam reforming may consist of a number of reactions depending on the reforming catalyst, operating conditions and feedstock composition, The typical industrially desirable reactions are the reverse of methanation (CH4 + H2O = CO + 3H2) and the water-gas shift (CO + H2O = CO2 + H2). Both reactions are equilibrium limited and the composition of the mixture that exits the reformer is in accordance with the one calculated thermodynarmically. Removal of reaction products at the reactor exit by means of selective membrane permeation can offer improved CH4 conversions and CO2 and H2 yields, assuming the subsequent utilization of the reject streams by a second methane-steam reformer. We numerically investigated the feasibility of a system of two tubular methane-steam reformers, in...

Kinetics of the reaction: H+HI→H2+I at 298 K and very low pressures

The reaction \scriptfont4=\seveni \scriptscriptfont4=\fivei

New Integrated Catalytic Membrane Processes for Enhanced Propylene and Polypropylene Production

\rm H+HI\mathop\rightarrow\limits ^{1}H_{2}+I

Pretreated Landfill Gas Conversion Process via a Catalytic Membrane Reactor for Renewable Combined Fuel Cell-Power Generation

was studied at 298 K and millitorr pressures employing the “Very Low Pressure Reactor” (VLPR) kinetic technique. H-atoms were generated by dissociating H2 molecules (of a H2/Ar mixture) in a microwave discharge cavity that preceded the very low pressure well-mixed reaction vessel. Quadrupole mass spectrometry was used to analyze molecules and atoms. The mass signal intensities of I and HI were measured at both 20 and 40 eV ionizing potentials while those of H and H2 were measured at 40 eV due to the very weak signal of these species at lower ionization potentials. Three different exit flow orifices were utilized in the reported VLPR experiments of about 2, 3, and 5 mm inner diameter to vary the species concentration under steady-state reaction conditions. A rate constant of k1=(2.1±0.2)×10−11 cm3/molecule.s was determined for the forward reaction at 298 K, which lies between the two previously reported values directly measured at 298 K. Satisfactory mass balance relations were obtained for the iodine atoms (from the HI and I species) which were better than 90% for most of the experiments. The value of the reported rate constant (k1) is 14.3% higher than the value measured by Umemoto et al. [6], and 33.3% lower than the value measured by Lorenz et al. [4]. Based on this comparison, the activation energy E1 of the forward reaction probably lies between those two previously reported values of 580 and 720 cal/mol. Transition State Calculations of A1 and A2 for the reaction of \scriptfont4=\seveni \scriptscriptfont4=\fivei

Reactor-membrane permeator process for hydrocarbon reforming and water gas-shift reactions

\rm H+I_{2}\mathop\rightarrow\limits ^{2}HI+I

American Transactions on Engineering & Applied Sciences

are in good agreement with the data on both reactions and suggest an activation energy of about 500±100 cal/mol for E2.© 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 915–925, 1997.

Methane and Methanol Steam Reforming in a Membrane Reactor for Efficient Hydrogen Production and Continuous Fuel Cell Operation

Newly reported integrated processes are discussed for aliphatic (paraffin) hydrocarbon dehydrogenation into olefins and subsequent polymerization into polyolefins (e.g., propane to propylene to polypropylene, ethane to ethylene to polyethylene). Catalytic dehydrogenation membrane reactors (permreactors) made by inorganic or metal membranes are employed in conjunction with fluid bed polymerization reactors using coordination catalysts. The catalytic propane dehydrogenation is considered as a sample reaction in order to design an integrated process of enhanced propylene polymerization. Related kinetic experimental data of the propane dehydrogenation in a fixed bed type catalytic reactor is reviewed which indicates the molecular range of the produced C1-C3 hydrocarbons. Experimental membrane reactor conversion and yield data are also reviewed. Experimental data were obtained with catalytic membrane reactors using the same catalyst as the non-membrane reactor. Developed models are discussed in terms of the operation of the reactors through computational simulation, by varying key reactor and reaction parameters. The data show that it is effective for catalytic permreactors to provide streams of olefins to successive polymerization reactors for the end production of polyolefins (i.e., polypropylene, polyethylene) in homopolymer or copolymer form. Improved technical, economic, and environmental benefits are discussed from the implementation of these processes.