Multifunctional Reactor Research Articles

Palladium based membranes and membrane reactors for hydrogen production and purification: An overview of research activities at Tecnalia and TU/e

In this paper, the main achievements of several European research projects on Pd based membranes and Pd membrane reactors for hydrogen production are reported. Pd-based membranes have received an increasing interest for separation and purification of hydrogen. In addition, the integration of such membranes in membrane reactors has been widely studied for enhancing the efficiency of several dehydrogenation reactions. The integration of reaction and separation in one multifunctional reactor allows obtaining higher conversion degrees, smaller reactor volumes and higher efficiencies compared with conventional systems. In the last decade, much thinner dense Pd-based membranes have been produced that can be used in membrane reactors. However, the thinner the membranes the higher the flux and the higher the effect of concentration polarization in packed bed membrane reactors. A reactor concept that can circumvent (or at least strongly reduce) concentration polarization is the fluidized bed membrane reactor configuration, which improves the heat transfer as well. Tecnalia and TU/e are involved in several European projects that are related to development of fluidized bed membrane reactors for hydrogen production using thin Pd-based (<5 μm) supported membranes for different application: In DEMCAMER project a water gas shift (WGS) membrane reactor was developed for high purity hydrogen production. ReforCELL aims at developing a high efficient heat and power micro-cogeneration system (m-CHP) using a methane reforming fluidized membrane reactor. The main objective of FERRET is the development of a flexible natural gas membrane reformer directly linked to the fuel processor of the micro-CHP system. FluidCELL aims the Proof-of-Concept of a m-CHP system for decentralized off-grid using a bioethanol reforming membrane reactor. BIONICO aims at applying membrane reactors for biogas conversion to hydrogen. The fluidized bed system allows operating at a virtually uniform temperature which is beneficial in terms of both membrane stability and durability and for the reaction selectivity and yield.

Recent Advances in Pd-Based Membranes for Membrane Reactors.

Palladium-based membranes for hydrogen separation have been studied by several research groups during the last 40 years. Much effort has been dedicated to improving the hydrogen flux of these membranes employing different alloys, supports, deposition/production techniques, etc. High flux and cheap membranes, yet stable at different operating conditions are required for their exploitation at industrial scale. The integration of membranes in multifunctional reactors (membrane reactors) poses additional demands on the membranes as interactions at different levels between the catalyst and the membrane surface can occur. Particularly, when employing the membranes in fluidized bed reactors, the selective layer should be resistant to or protected against erosion. In this review we will also describe a novel kind of membranes, the pore-filled type membranes prepared by Pacheco Tanaka and coworkers that represent a possible solution to integrate thin selective membranes into membrane reactors while protecting the selective layer. This work is focused on recent advances on metallic supports, materials used as an intermetallic diffusion layer when metallic supports are used and the most recent advances on Pd-based composite membranes. Particular attention is paid to improvements on sulfur resistance of Pd based membranes, resistance to hydrogen embrittlement and stability at high temperature.

Recent Advances in Diesel Particulate Emission Control

Diesel Particulate Filters are the most complex component of today’s emission control systems as they need to incorporate different and often conflicting functionalities such as high soot nanoparticle filtration efficiency, low pressure drop behavior, direct catalytic soot oxidation activity, high oxidation activity for Carbon Monoxide, Hydrocarbons and Nitrogen Oxide, as well as ability to reduce Nitrogen Oxides. Significant progress has been made employing both fundamental research as well as applications-oriented approaches. These have led to an improved understanding of the coupled physicochemical transport and reaction phenomena occurring in DPFs. We have researched new materials, designs and control approaches for enhancing the design and reliability of future Diesel Particulate Emission Control systems. An enabling technology has been the development and synthesis of nanostructured catalysts and their incorporation into a multifunctional reactor for Diesel Emission. Apart from the composition, the material morphological characteristics also contribute to the catalytic activity. As an example we present different nanoparticle catalysts characterized with respect to their physical and morphological properties as well as with respect to their catalytic soot oxidation activity. The detailed kinetic data obtained are shown to correlate very well to a composite morphological parameter, derived here for the first time, combining the catalyst particle size, surface area, crystallite size, and porosity. Likewise when sub-micron/micron sized, dense catalyst particles were obtained by milling for various time intervals, resulting in a poly-disperse multimodal distribution, the kinetic data correlate well with the total surface-weighted mean particle size. This study establishes to our knowledge for the first time a quantitative mechanistic link between catalyst particle structure and kinetic parameters, facilitating much the rational estimation of kinetic parameters in simulation studies of catalytic soot oxidation.

Structural and Operational Optimality of Adsorptive Reactors

AbstractAdsorptive reactors represent a promising genre of multifunctional reactors combining the highly compatible adsorptive and reactive functionalities. Although they offer multiple benefits to the overall process flowsheet, overcoming the low space time yields, which are an inherent drawback of their cyclic operation, and unwanted functionality interference remain a challenge. The potential of temperature profiling to expedite the macrostructuring of adsorptive reactors for performance optimization is presented. Two industrially relevant reactions have been investigated as test cases: the Claus reaction for recovering sulfur from acid gas and the Deacon reaction for the plant‐internal recycling of chlorine via HCl oxidation.

Chemical Looping for Energy Technology: A Special Issue

Chemical Looping for Energy Technology: A Special Issue

Comment on ‘hydrogen/methanol production in a novel multifunctional reactor with in situ adsorption: modeling and optimization’

Comment on ‘hydrogen/methanol production in a novel multifunctional reactor with in situ adsorption: modeling and optimization’

Catalysis in Multifunctional Reactors

A multifunctional reactor is broadly defined as a multifaceted reactor system that combines a conventional reactor with any physical process to enhance the overall performance of the process to bring cost-effectiveness and/or compactness to a chemical plant. This multi-functionality can exist either on micro (catalyst) level or on macro (reactor) level [1]. There is substantial information available on several ways to achieve this task. Combining reaction with separation is one such popular approach. Here, when separation is performed in situ, several benefits like an increase in per-pass conversion and/or selectivity, energy integration, longer catalyst life, etc. are attained. When a separation process – e.g. distillation, adsorption, etc. – is to be performed simultaneously with a reaction, it imposes more restrictions on the reactor design so as to meet possible conflicting requirements that result from the reaction and separation. The existence of multiple phases as well as problems associated with heat and momentum transfer, mixing issues, etc. make the process complex, thereby attracting the attention of experts in reaction engineering, catalysis, modeling and simulation, and process design. Since catalysts are an integral part of a reactor system, many efforts have been made to manipulate its design to meet the above-mentioned challenges. A few examples are inserting special catalyst-filled envelopes into a distillation column to reduce pressure drop, manipulating the hydrophobicity of ion exchange resin in reactive chromatography for selective separation, grafting the catalyst in membrane material, etc. In this chapter, we review the recent literature on catalysts and their modified forms used in multifunctional reactors that combine reaction and separation. We restrict ourselves to the four most studied multifunctional reactors: reactive distillation, reactive stripping, membrane reactors and chromatographic reactors.

Autothermal reforming of impure glycerol for H2 production: Thermodynamic study including in situ CO2 and/or H2 separation

In the present work, thermodynamics was applied to study the autothermal reforming (ATR) of impure glycerol (mixture of glycerol and methanol) to generate pure hydrogen. The equilibrium compositions were calculated using the Gibbs free energy minimization method and simulations were performed in a wide range of conditions of pressure (1–20 atm), temperature (600–1000 K), oxygen to glycerol feed molar ratio (0.0–3.0), and water to glycerol feed molar ratio (3–12). The effect of in situ CO2 and/or H2 removal was investigated as well, in the perspective of reaction/separation process integration in a hybrid multifunctional reactor. Whatever the composition of the glycerol fed, the in situ separation of H2 and CO2 in ATR process maximizes the hydrogen yield and completely eliminates methane, carbon monoxide and carbon dioxide formation. At 700 K, it is possible to improve the H2 yield, with respect to the traditional reactor, up to 186% when CO2 removal is considered, up to 152% when only H2 removal is implemented, and by 195% when both H2 and CO2 removal are considered in the hybrid reactor.From the investigation of the energetically neutral conditions, it was found that in the sorption-enhanced process, with or without in situ H2 separation, no partial oxidation reactions are needed to provide the required heat to maintain the isothermal reformer at the desired temperature, and consequently the yield of hydrogen can be improved up to 6.93, which is close to the stoichiometric theoretical value of 7.

Multifunctional nanoreactor for comprehensive characterization of membrane proteins based on surface functionalized mesoporous foams.

An integrated protocol is proposed here for efficient analysis of membrane proteins based on surface functionalized mesoporous graphene foams (MGF). The inherent hydrophobic nature of MGF and surface modification with hydrophilic chitosan (CS) make it highly suitable for the enrichment of hydrophobic membrane proteins from organic solvent, while remaining well-dispersed in aqueous solution for subsequent proteolysis. Therefore, such a multifunctional reactor ensures a facile solvent adjustment route. Furthermore, as a chitosan modified nanoporous reactor, it also provides a biocompatible nanoenvironment that can maintain the stability and activity of enzymes to realize efficient in situ digestion of the enriched membrane proteins. The concept was first proved with a standard hydrophobic membrane protein, bacteriorhodopsin, where a high number of identified peptides and amino acid sequence coverage were achieved even at extremely low protein concentration. The mesoporous reaction system was further applied to the analysis of complex real-case proteome samples, where 931 membrane proteins were identified in triplicate analyses by 2D LC-MS/MS. In contrast, with in-solution proteolysis, only 73 membrane proteins were identified from the same sample by the same 2D LC-MS/MS. The identified membrane proteins by the MGF-CS protocol include many biomarkers of the cell line. These results suggest that the multifunctional MGF-CS protocol is of great value to facilitate the comprehensive characterization of membrane proteins in the proteome research.

Stabilization of pyrolysis oil: Comparison of reactive distillation and reactive chromatography

The present study, evaluates the applicability of reactive distillation and reactive chromatography for stabilization of bio-oil, obtained from pyrolysis of wood. Bio-oil, along with several oxygenated organic compounds, contains substantial amounts of carboxylic acids (e.g., acetic acid, 5–10%). The presence of acids results in a shorter shelf life of bio-oil, as it catalyzes condensation reactions of furfural-like components leading to an increase in viscosity over a time period. Thus, we investigate the ability of multifunctional reactor for stabilization of bio-oil through esterification of acid with suitable alcohol in the presence of ion-exchange resin catalyst. Reactive distillation is performed at higher a temperature which is dictated by the bubble point of the mixture, reactive chromatography allows one to perform reaction at relatively low temperatures and with lower alcohols. It results in an improvement in the characteristic properties of bio-oil, thereby increasing the shelf life. The main limitation of this approach is that the catalyst used for esterification also catalyzes simultaneous polymerization of furfural-like components which deactivate the catalyst. Deactivation of Amberlyst-15 with ethanol after 20h of continuous run in a fixed-bed chromatographic-reactor was found to be less compared to RD making RC a promising candidate for this particular application.

Long-Term n-Caproic Acid Production from Yeast-Fermentation Beer in an Anaerobic Bioreactor with Continuous Product Extraction

Multifunctional reactor microbiomes can elongate short-chain carboxylic acids (SCCAs) to medium-chain carboxylic acids (MCCAs), such as n-caproic acid. However, it is unclear whether this microbiome biotechnology platform is stable enough during long operating periods to consistently produce MCCAs. During a period of 550 days, we improved the operating conditions of an anaerobic bioreactor for the conversion of complex yeast-fermentation beer from the corn kernel-to-ethanol industry into primarily n-caproic acid. We incorporated and improved in-line, membrane liquid-liquid extraction to prevent inhibition due to undissociated MCCAs at a pH of 5.5 and circumvented the addition of methanogenic inhibitors. The microbiome accomplished several functions, including hydrolysis and acidogenesis of complex organic compounds and sugars into SCCAs, subsequent chain elongation with undistilled ethanol in beer, and hydrogenotrophic methanogenesis. The methane yield was 2.40 ± 0.52% based on COD and was limited by the availability of carbon dioxide. We achieved an average n-caproate production rate of 3.38 ± 0.42 g L(-1) d(-1) (7.52 ± 0.94 g COD L(-1) d(-1)) with an n-caproate yield of 70.3 ± 8.81% and an n-caproate/ethanol ratio of 1.19 ± 0.15 based on COD for a period of ∼55 days. The maximum production rate was achieved by increasing the organic loading rates in tandem with elevating the capacity of the extraction system and a change in the complex feedstock batch.

Comparison of reactive chromatography and reactive distillation for the synthesis of C1–C4 acetates

This work compares two multifunctional reactors, reactive distillation and chromatographic reactors, for the production of C1–C4 carboxylic esters. Both the processes have been simulated using appropriate simulators; and near optimal operating conditions are found based on the conceptual design and non-dominated sorting genetic algorithm (NSGA II) methodologies. The energy consumptions per kg of esters produced in both the processes are compared, and it has been found that for ethyl alcohol, reactive chromatography performs at par with reactive distillation. In the other cases (methanol, n-propanol and n-butanol), the reactive distillation is much more attractive.

Dynamics of reactive chromatographic columns of inert core/hollow/film coated spherical packing: An analytical solution and applications

The transient behavior of reactive-diffusive fixed-bed (chromatographic columns or reactors) packed with inert core/shell core/hollow/thin film coated monodisperse spherical rigid particles is investigated. We modeled the reactive sorption system with linear mass exchange law between the flowing and the stationary phases. The coupled governing partial differential equations were integrated analytically using Laplace transformations. The analytical closed form solution involves two infinite integrals. The closed form solution was integrated numerically and the breakthrough curves of the system were studied under the influence of the system parameters. The limiting cases are discussed, a simple asymptotic closed form solution for fixed-bed desorbers with monodisperse spherical particles is obtained, and results are generalized for similar kinetics of reactive chromatographic columns (fixed-beds) for diffusion/absorption into the inert core spherical packing. Further, potential applications of the mathematical model and results in processes such as liquid vapor extraction, various forms of chromatography, reactive sorption, multifunctional reactors, process intensification, and regeneration of ion exchange columns are briefly discussed.

Simulated Moving Bed Reactor for the Synthesis of 2-Ethylhexyl Acetate. Part II: Simulation Based Design

A simulated moving bed reactor (SMBR) is a multifunctional reactor wherein the reaction and chromatographic separation take place simultaneously. The positions of the inlet and outlet ports are switched at periodic intervals to simulate a true moving bed system. The design exercise for these units is a challenging task due to the large number of degrees of freedom such as the column volume, SMBR configuration (i.e., number of beds in each section), sectional flow rates, switch time, desorbent concentration and feed concentration. In this work, we propose a simulation based design methodology for the SMBR process that is employed for heterogeneously catalyzed reversible reactions, in which one of the reactants works as a solvent and the catalyst also plays the role of adsorbent. The objectives are productivity (PR) maximization and desorbent consumption (DC) minimization which have a direct impact on the total annualized cost of the process. The performance parameters such as conversion, raffinate purity, ...

CAMURE-9 &amp; ISMR-8: 9th International Symposium on Catalysis in Multiphase Reactors and 8th International Symposium on Multifunctional Reactors (Lyon, France, December 7–10, 2014)

Article CAMURE-9 & ISMR-8: 9th International Symposium on Catalysis in Multiphase Reactors and 8th International Symposium on Multifunctional Reactors (Lyon, France, December 7–10, 2014) was published on August 1, 2014 in the journal Green Processing and Synthesis (volume 3, issue 4).

Are Intensified Processes Safer and More Reliable than Traditional Processes? An emblematic Case Study

One of the best ways of preventing accidents is to avoid hazards by inherently safer design. As many processes, particularly those in the chemicals, nuclear and oil industries, involve the production, handling and use of hazardous substances, process intensification (PI) apparently offers to the plant managers many benefits such as safer, cleaner, smaller, and cheaper equipments. Process Intensification could lead to a higher process flexibility, increased inherent safety and energy efficiency, distributed manufacturing capability, and ability to use reactants at higher concentrations. These goals are achieved by multifunctional reactors, e.g. reactive distillation or membrane reactors, and miniaturization that can be done by employing micro reactors and/or improving heat and mass transfer. Within the benefits of process intensification with reference to process safety the following can be considered: The use of process intensification can reduce the number of process operations, which leads to fewer transfer operations and less pipework, preventing source of leakages; It can be easier to design a smaller vessel to contain the maximum pressure of any probable explosion; For exothermic reactions, the enhanced specific surface area of intensified plants makes heat transfer, and thus heat removal, easier, minimising the triggering potential of a runaway reaction. Process intensification has thus the potential to be a significant factor in the implementation of inherent safety practices Although safety can benefit from process intensification, it should be ensured that new hazards are not created. This can be obtained applying at a early design stage the reliability and safety analysis that are traditionally used in process risk assessment. In this paper in particular the above techniques are applied to a VOC (Volatile organic compound) treatment plant, comparing the traditional plant (a fixed bed reactor) to the intensified reverse flow reactor. From the results of the application of a recursive operability analysis and the successive fault trees fully quantified, some conclusions are drawn from the point of view of the reliability of intensified processes and from the adequateness of risk assessment methodologies

Green Process Engineering as the Key to Future Processes

Growing concern for the environment, increasing stringent standards for the release of chemicals into the environment and economic competiveness have led to more environmentally friendly approaches that have resulted in greater pollution prevention via waste reduction and efficiency maximisation. Green process engineering (GPE) is an important tool that could make significant contributions in the drive toward making hazardous and wasteful processes more sustainable for the benefit of the economy, environment and society. This article highlights the guidelines that could be used by scientists and engineers for designing new materials, products, processes and systems. Few examples of current and future applications of GPE, particularly in the areas of biofuels, supercritical fluids, multi-functional reactors and catalytic processes, have been presented.

Engineering reactors for catalytic reactions

Catalytic reactions are ubiquitous in chemical and allied industries. A homogeneous or heterogeneous catalyst which provides an alternative route of reaction with lower activation energy and better control on selectivity can make substantial impact to process viability and economics. Extensive studies have been conducted to establish sound basis for design and engineering of reactors for practising such catalytic reactions and for realizing improvements in reactor performance. In this article, application of recent (and not so recent) developments in engineering reactors for catalytic reactions is discussed. Some examples where performance enhancement was realized by catalyst design, appropriate choice of reactor, better injection and dispersion strategies and recent advances in process intensification/ multifunctional reactors are discussed to illustrate the approach. Catalytic reactions are ubiquitous in chemical and allied industries. Some aspects of engineering of catalytic reactors (which include evolving best possible hardware and operating protocol for transformation of raw materials into value added products) are discussed here along with some real life examples of performance enhancement.

Combined physico-chemical treatment of secondary settled municipal wastewater in a multifunctional reactor

In this paper, the physico-chemical treatment of municipal wastewater for the simultaneous removal of pollutant indicators (chemical oxygen demand (COD) and total coliforms) and organic contaminants (total phenols) was investigated and assessed. A secondary settled effluent was subjected to coagulation, disinfection and absorption in a multifunctional reactor by dosing, simultaneously, aluminum polychloride (dose range: 0-150 μL/L), natural zeolites (dose range: 0-150 mg/L), sodium hypochlorite (dose range: 0-7.5 mg/L) and powder activated carbon (dose range: 0-30 mg/L). The treatment process was optimized using computational fluid dynamics (CFD) and response surface methodology. Specifically, a Latin square technique was employed to generate 16 combinations of treating agent types and concentrations which were pilot tested on an 8 m(3)/h multifunctional reactor fed by a secondary effluent with COD and total coliform concentrations ranging from ≈20 to 120 mg/L and from 10(5) to 10(6) CFU/100 mL, respectively. Results were promising, indicating that removal yields up to 71% in COD and 5.4 log in total coliforms were obtained using an optimal combination of aluminum polychloride (dose range ≈ 84-106 μL/L), powder activated carbon ≈ 5 mg/L, natural zeolite (dose range ≈ 34-70 mg/L) and sodium hypochlorite (dose range ≈ 3.4-5.6 mg/L), with all treating agents playing a statistically significant role in determining the overall treatment performance. Remarkably, the combined process was also able to remove ≈ 50% of total phenols, a micropollutant known to be recalcitrant to conventional wastewater treatments.

Analysis of a nonisothermal simulated moving‐bed reactor

Simulated moving‐bed reactor (SMBR) is a multifunctional reactor wherein in situ separation of the products facilitates the reversible reaction to completion beyond thermodynamic equilibrium and at the same time obtaining products of high purity. In this work, we investigate the feasibility of introducing variances in adsorption strength, which has recently been proven to effectively improve SMB performance for pure separation, into an SMB system to include reactions. Synthesis of methyl acetate catalyzed by amberlyst 15 is considered as model system. Numerical simulations were carried out for an SMBR unit consisting of four columns and operated with various temperature distributions in the range of 308–323 K. SMBR productivities were evaluated and compared under the constraints of complete conversion and complete product separation. The effects of kinetics, heat transfer efficiency and adsorption strength of reactant were systematically investigated. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4705–4714, 2013