Development of the dimethyl ether-to-olefins process: from fundamentals to the reactor simulation

235 p.Esta tesis estudia el proceso de conversión de dimetil éter en olefinas (DTO) sobre catalizadores de zeolita HZSM-5, abarcando la comprensión del mecanismo de reacción, selección del catalizador, modelado cinético, diseño de reactores alternativos y de un sistema reactor-regenerador con unidades de lecho fluidizado (adecuado para la implantación industrial). Se han realizado contribuciones originales en las metodologías de dos facetas fundamentales, que son de aplicación en otros procesos con desactivación del catalizador: (i) el modelado cinético para esquemas de reacción complejos; (ii) el diseño de reactores con circulación de catalizador. Así, se ha establecido el modelo cinético de lumps para dos catalizadores de zeolita HZSM-5 con diferente acidez, considerando el mecanismo de reacción y desactivación. Se ha procedido igual para el craqueo de n-pentano, seleccionado como compuesto modelo de la fracción mayoritaria de subproductos en el proceso DTO. Los modelos cinéticos se han utilizado para el diseño de diferentes reactores (lecho fijo, móvil y fluidizado sin y con circulación del catalizador). El diseño del sistema reactor-regenerador se ha realizado con un modelo original, considerando la distribución de la actividad en ambas unidades y su relación. El modelo se ha utilizado en el análisis del efecto de las variables (temperatura, tiempo espacial, agua co-alimentada y tiempo medio de residencia), y de la acidez del catalizador, en la conversión, rendimiento de olefinas y subproductos, y desactivación, obteniéndose las condiciones adecuadas del proceso

Development of the dimethyl ether-to-olefins process: from fundamentals to the reactor simulation

235 p.Esta tesis estudia el proceso de conversión de dimetil éter en olefinas (DTO) sobre catalizadores de zeolita HZSM-5, abarcando la comprensión del mecanismo de reacción, selección del catalizador, modelado cinético, diseño de reactores alternativos y de un sistema reactor-regenerador con unidades de lecho fluidizado (adecuado para la implantación industrial). Se han realizado contribuciones originales en las metodologías de dos facetas fundamentales, que son de aplicación en otros procesos con desactivación del catalizador: (i) el modelado cinético para esquemas de reacción complejos; (ii) el diseño de reactores con circulación de catalizador. Así, se ha establecido el modelo cinético de lumps para dos catalizadores de zeolita HZSM-5 con diferente acidez, considerando el mecanismo de reacción y desactivación. Se ha procedido igual para el craqueo de n-pentano, seleccionado como compuesto modelo de la fracción mayoritaria de subproductos en el proceso DTO. Los modelos cinéticos se han utilizado para el diseño de diferentes reactores (lecho fijo, móvil y fluidizado sin y con circulación del catalizador). El diseño del sistema reactor-regenerador se ha realizado con un modelo original, considerando la distribución de la actividad en ambas unidades y su relación. El modelo se ha utilizado en el análisis del efecto de las variables (temperatura, tiempo espacial, agua co-alimentada y tiempo medio de residencia), y de la acidez del catalizador, en la conversión, rendimiento de olefinas y subproductos, y desactivación, obteniéndose las condiciones adecuadas del proceso

Understanding the Adsorption Capacity for CO2 in Reduced Graphene Oxide (rGO) and Modified Ones with Different Heteroatoms in Relation to Surface and Textural Characteristics

Reduced graphene oxide is a material that has a variety of applications, especially in CO2 adsorption. The study of this research is the preparation of reduced graphene oxide with different heteroatoms and how the adsorption capacity is changed. The functionalization with other compounds bearing Si, S, N, and O was before reducing graphene oxide. Different monoliths were prepared by changing the ascorbic acid analogy and the temperature of reduction. The different porosity values, percentages of heteroatoms, and synthetic parameters show that the adsorption capacity is a complex procedure that can be affected by multiple parameters. Microporosity, different functionalities from heteroatoms, and high surface/volume of pores are the significant parameters that affect adsorption. All parameters should establish a balance among all parameters to achieve high adsorption of CO2.This research was funded by Basque Government, grant number GV IT999-16

Characterization and controlled combustion of carbonaceous deactivating species deposited on an activated carbon-based catalyst

The composition of the carbonaceous deactivating species (coke) deposited on a Pt and Pd supported P-containing activated carbon catalyst has been studied. These deactivating species were deposited on the catalyst during the hydrocracking of scrap tire pyrolysis oil at 400-500 degrees C, and it has been selectively characterized by means of temperature-programmed oxidation (TPO), temperature-programmed desorption/gas chromatography (TPD/GC) and laser desorption-ionization/mass spectroscopy (LDI/MS). In addition, the evolution of the textural properties and the acidity of the deactivated catalysts have been evaluated. The high thermal and oxidation resistance of the catalytic support has allowed to combust the coke in the TPO and calculate its intrinsic activation energy as a function of the extent of the combustion. Combined TPO and LDI/MS results have shown that an increase in the hydrocracking temperature attenuates the catalyst deactivation due to the hydrocracking of coke precursors. Coke aging, by evolving towards a more condensed structure, is also favored at higher hydrocracking temperatures. The combustion of the most condensed coke requires of higher temperatures than 375 degrees C, which hinders the complete regeneration of the activated carbon-based catalyst. (C) 2017 Elsevier B.V. All rights reserved

Reduced Graphene Oxide/Polymer Monolithic Materials for Selective CO2 Capture

Polymer composite materials with hierarchical porous structure have been advancing in many different application fields due to excellent physico-chemical properties. However, their synthesis continues to be a highly energy-demanding and environmentally unfriendly process. This work reports a unique water based synthesis of monolithic 3D reduced graphene oxide (rGO) composite structures reinforced with poly(methyl methacrylate) polymer nanoparticles functionalized with epoxy functional groups. The method is based on reduction-induced self-assembly process performed at mild conditions. The textural properties and the surface chemistry of the monoliths were varied by changing the reaction conditions and quantity of added polymer to the structure. Moreover, the incorporation of the polymer into the structures improves the solvent resistance of the composites due to the formation of crosslinks between the polymer and the rGO. The monolithic composites were evaluated for selective capture of CO2. A balance between the specific surface area and the level of functionalization was found to be critical for obtaining high CO2 capacity and CO2/N2 selectivity. The polymer quantity affects the textural properties, thus lowering its amount the specific surface area and the amount of functional groups are higher. This affects positively the capacity for CO2 capture, thus, the maximum achieved was in the range 3.56–3.85 mmol/g at 1 atm and 25 °C.Spanish Government (CTQ2016-80886-R; BES-2017-080221), Basque Government (GV IT999-16) and NATO (SfP project G4255) are gratefully acknowledged for their financial support. The authors would like to acknowledge the contribution of the COST Action CA 15107

Nature and Location of Carbonaceous Species in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl Ether into Light Olefins

The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the mesoand macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition.The financial support of this work was undertaken by the Ministry of Economy and Competitiveness of the Spanish Government, some cofounded with ERDF funds (Project CTQ2013-46172-P, CTQ2013-46173-R and CTQ2016-79646-P projects), by the Basque Government (Project IT748-13) and by the University of the Basque Country (UFI 11/39). M. Ibafiez is grateful for the postgraduate grant from the University of the Basque Country (No. UPV/EHU2016)

Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst During MTH with XRD

publishedVersio

A techno-economic and life cycle assessment for the production of green methanol from CO2: catalyst and process bottlenecks

The success of catalytic schemes for the large-scale valorization of CO2 does not only depend on the development of active, selective and stable catalytic materials but also on the overall process design. Here we present a multidisciplinary study (from catalyst to plant and techno-economic/lifecycle analysis) for the production of green methanol from renewable H2 and CO2. We combine an in-depth kinetic analysis of one of the most promising recently reported methanol-synthesis catalysts (InCo) with a thorough process simulation and techno-economic assessment. We then perform a life cycle assessment of the simulated process to gauge the real environmental impact of green methanol production from CO2. Our results indicate that up to 1.75 ton of CO2 can be abated per ton of produced methanol only if renewable energy is used to run the process, while the sensitivity analysis suggest that either rock-bottom H2 prices (1.5 $kg−1) or severe CO2 taxation (300$ per ton) are needed for a profitable methanol plant. Besides, we herein highlight and analyze some critical bottlenecks of the process. Especial attention has been paid to the contribution of H2 to the overall plant costs, CH4 trace formation, and purity and costs of raw gases. In addition to providing important information for policy makers and industrialists, directions for catalyst (and therefore process) improvements are outlined.The authors gratefully acknowledge financial support from the King Abdullah University of Science and Technology (KAUST). T. Cordero-Lanzac and A.T. Aguayo acknowledge the financial support received from the Spanish Ministry of Science and Innovation with some ERDF funds (CTQ2016-77812-R) and the Basque Government (IT1218-19). T. Cordero-Lanzac also acknowledges the Spanish Ministry of Education, Culture and Sport for the award of his FPU grant (FPU15-01666). A. Navajas and L.M. Gandía gratefully acknowledge the financial support from Spanish Ministerio de Ciencia, Innovación y Universidades, and the European Regional Development Fund (ERDF/FEDER) (grant RTI2018-096294-B-C31). L.M. Gandía also thanks Banco de Santander and Universidad Pública de Navarra for their financial support under ‘’Programa de Intensificación de la Investigación 2018’ initiative

Lignin-derived Pt supported carbon (submicron)fiber electrocatalysts for alcohol electro-oxidation

Lignin fibers, with and without phosphorus, and loaded with platinum have been prepared in a single step by electrospinning of lignin/ethanol/phosphoric acid/platinum acetylacetonate precursor solutions. Thermochemical treatments have been carried out to obtain lignin-based carbon fiber electrocatalysts. The electrospun lignin fibers were thermostabilized in air and carbonized at 900 °C. The effect of phosphorus and platinum content on the porous texture, the surface chemistry and the oxidation/electro-oxidation resistance have been studied. Phosphorus-containing carbon fibers develop a higher surface area (c.a. 1200 m2 g−1), exhibit a lower Pt particle size (2.1 nm) and a better particle distribution than their counterpart without phosphorus (c.a. 750 m2 g−1 of surface area and 9.6 nm Pt particle size). It has been proved that phosphorus improves the oxidation and electro-oxidation resistance of the fibers, avoiding their oxidation during the preparation thermal stages and is responsible of the generation of a microporous material with an unusual wide operational potential window (1.9 V). An important Pt–P synergy has been observed in the oxygen transfer during the oxidation and electro-oxidation of the fibers. The obtained carbon fibers can act directly as electrodes without any binder or conductivity promoter. The fibers with platinum have shown outstanding catalyst performance in the electro-oxidation of methanol and ethanol.This work was supported by the Spanish MINECO under CTQ2015-68654-R project