H2 from biofuels and carriers: A concerted homo-heterogeneous kinetic model of ethanol partial oxidation and steam reforming on Rh/Al2O3

Investigating bioethanol as a renewable energy source is crucial in the context of H2-based economy. Ethanol partial oxidation and steam reforming on Rh/Al2O3 represent promising processes that have already proved to be highly tangled reacting systems. In this work, a significant step forward has been done towards the development of an engineering tool that can capture all the relevant features of the process; a combined homo-heterogeneous kinetic scheme was developed and validated against experimental data, informative of the catalytic and thermal activation of the C2-alcohol. In particular, a 36-species reduced homogeneous scheme was developed, able to cap -ture observed trends with a limited computational load. On the other side, a macro-kinetic heterogeneous scheme with six molecular reactions (ethanol oxidative dehydrogenation, total oxidation, decomposition, dehydrogenation, steam reforming and acetaldehyde post -reforming) was tuned to accurately describe ethanol/O2 and ethanol/H2O reacting systems.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Microwave-assisted, performance-advantaged electrification of propane dehydrogenation

Nonoxidative propane dehydrogenation (PDH) produces on-site propylene for value-added chemicals. While commercial, its modest selectivity and catalyst deactivation hamper the process efficiency and limit operation to lower temperatures. We demonstrate PDH in a microwave (MW)–heated reactor over PtSn/SiO2 catalyst pellets loaded in a SiC monolith acting as MW susceptor and a heat distributor while ensuring comparable conditions with conventional reactors. Time-on-stream experiments show active and stable operation at 500°C without hydrogen addition. Upon increasing temperature or feed partial pressure at high space velocity, catalysts under MWs show resistance in coking and sintering, high activity, and selectivity, starkly contrasting conventional reactors whose catalyst undergoes deactivation. Mechanistic differences in coke formation are exposed. Gas-solid temperature gradients are computationally investigated, and nanoscale temperature inhomogeneities are proposed to rationalize the different performances of the heating modes. The approach highlights the great potential of electrification of endothermic catalytic reactions

Microwave-assisted, performance-advantaged electrification of propane dehydrogenation

Nonoxidative propane dehydrogenation (PDH) produces on-site propylene for value-added chemicals. While commercial, its modest selectivity and catalyst deactivation hamper the process efficiency and limit operation to lower temperatures. We demonstrate PDH in a microwave (MW)–heated reactor over PtSn/SiO2 catalyst pellets loaded in a SiC monolith acting as MW susceptor and a heat distributor while ensuring comparable conditions with conventional reactors. Time-on-stream experiments show active and stable operation at 500°C without hydrogen addition. Upon increasing temperature or feed partial pressure at high space velocity, catalysts under MWs show resistance in coking and sintering, high activity, and selectivity, starkly contrasting conventional reactors whose catalyst undergoes deactivation. Mechanistic differences in coke formation are exposed. Gas-solid temperature gradients are computationally investigated, and nanoscale temperature inhomogeneities are proposed to rationalize the different performances of the heating modes. The approach highlights the great potential of electrification of endothermic catalytic reactions.The initial part of this work was supported by the Department of Energy (DOE)’s Office of Energy Efficient and Renewable Energy’s Advanced Manufacturing Office under award number DE-EE0007888-8.3. The latter part was supported by the US DOE award number DE- SC0024085. The Delaware Energy Institute gratefully acknowledges the support and partnership of the State of Delaware toward the RAPID (Rapid Advancement in Process Intensification Deployment) projects.Peer reviewe

Catalytic behavior of chromium oxide supported on nanocasting-prepared mesoporous alumina in dehydrogenation of propane

Mesoporous alumina with narrow pore size distribution centered in the range of 4.4–5.0 nm and with a specific surface area as high as 270 m2·g−1 was prepared via the nanocasting approach using a CMK-3 carbon replica as a hard template. Based on this support, a series of catalysts containing 1, 5, 10, 20 and 30 wt % of chromium was prepared by incipient wetness impregnation, characterized, and studied in the dehydrogenation of propane to propene (PDH). Cr species in three oxidation states—Cr(III), Cr(V) and Cr(VI)—were found on the oxidized surface of the catalysts. The concentration of these species varied with the total Cr loading. Temperature-programmed reduction (H2-TPR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) studies revealed that Cr(VI) species dominated at the lowest Cr content. An increase in the Cr loading resulted in an appearance of an increasing amount of Cr(III) oxide. UV-Vis-DRS measurements performed in situ during the PDH process showed that at the beginning of the catalytic test Cr(VI) species were reduced to Cr(III) redox species. A crucial role of the redox species in the PDH process over the catalysts with the low Cr content was confirmed. The stability test for the catalyst containing 20 wt % of Cr showed that this sample exhibited the reproducible catalytic performance after the first four regeneration–dehydrogenation cycles. Moreover, this catalyst had higher resistance on deactivation during the PDH process as compared to the reference catalyst with the same Cr loading, but was supported on commercially available alumina

Development and integration of new processes consuming carbon dioxide in multi-plant chemical production complexes

New, energy-efficient and environmentally acceptable, catalytic processes have been identified that can use excess high purity CO2 as a raw material from the sources available in a chemical production complex. The chemical complex in the lower Mississippi River Corridor has been used to show how these new plants can be integrated into this existing infrastructure using the Chemical Complex and Cogeneration Analysis System. Eighty six published articles of laboratory and pilot plant experiments were reviewed that describe new methods and catalysts to use CO2 for producing commercially important products. Reactions have been categorized as hydrogenation reactions; hydrocarbon synthesis reactions; amine syntheses reactions; and hydrolysis reactions. A methodology for selecting the new energy-efficient processes was developed. The selection criteria included operating conditions, energy requirement for reactions, ΔH° and equilibrium conversion based on Gibbs free energy, ΔG°; and thermodynamic feasibility of the reactions, catalyst conversion and selectivity, cost and life, and methods to regenerate catalysts. Also included were demand and potential sales of products and market penetration. In addition, cost of raw materials, energy, environmental, sustainable and other manufacturing costs were evaluated along with hydrogen consumption for hydrogenation reactions. Based on the methodology, twenty processes were identified as candidates for new energy-efficient and environmentally acceptable plants. These were simulated using HYSYS, and a value added economic analysis was evaluated. From these, fourteen of the most promising were integrated in the superstructure. A base case of existing plants in a chemical complex in the lower Mississippi River Corridor was developed that included thirteen multiple plant production units plus associated utilities for power, steam and cooling water and facilities for waste treatment. The System was used with the base case and new plants for CO2, and an optimal configuration of plants was determined for three different case studies. These results illustrated the capability of the System to select an optimum configuration of plants in a chemical complex and incorporate economic, environmental and sustainable costs. The System has been developed by industry-university collaboration, and is available from the LSU Minerals Processing Research Institute’s web site www.mpri.lsu.edu at no charge

A Review of Packed Bed Reactor and Gradient-less Recycle Reactor for Determination of Intrinsic Reaction Kinetics

Intrinsic reaction kinetics is an essential information in catalytic reaction engineering. This paper reviews the two laboratory reactors, i.e., the packed-bed reactor and gradient-less recycle reactor commonly employed for determining the intrinsic reaction kinetics of heterogeneous catalysts. Although both reactors have been well-known for kinetic studies for a long time, there are still efforts to address some essential issues and to further develop the reactors. For example, a new design of the gradient-less recycle reactor was developed to broaden the operating window for intrinsic kinetic studies at low pressure. Furthermore, the intrinsic kinetic modeling in the gradient-less recycle reactor and packed-bed reactor, including the effects of mass transfer and axial dispersion, was also investigated. This review article provides in detail the types of both reactors, the development of both packed-bed reactor and gradient-less recycle reactor, intrinsic kinetic modeling, and the methods for determining heat- and mass- transfer limitations. All of these point out the suitable methods for determining intrinsic kinetics and perspectives for future works