Eugenio Meloni

Influence of operative parameters on microwave regeneration of catalytic soot wff for diesel engines

Wall-Flow Diesel Particulate Filters (DPFs) are considered the most effective devices for the control of diesel particulate emissions; however they need a periodic continuous regeneration. Recently, there has been a lot of interest in using MW energy for DPF regeneration due to its instantaneous and selective heating process. So the objectives of this study were to conduct experiments to: 1. prepare a specifically catalysed SiC DPF with MW absorption properties; 2. demonstrate the efficiency of the microwave regeneration.

Microwave Susceptible Catalytic Diesel Particulate Filter

The diesel internal combustion engine is one of the most environmentally-friendly vehicle devices, because it emits less carbon dioxide and is more fuel efficient than the universal gasoline stoichiometric engine. However, considerable challenges still exist regarding the emission control of particulate matter (PM), commonly known as soot, emitted by the diesel combustion process. These ultrafine particles, which have aerodynamic diameters of less than 2.5 ?m (PM2.5), are problematic as they can cause serious respiratory diseases, including lung cancer and chronic obstructive pulmonary disease. Various filters are commonly used for soot abatement in diesel exhaust, while catalytic oxidation is preferable to intensify burning of soot trapped in filters. The diesel particulate filters (DPFs) are the most important technologies to maintain soot emissions under EU regulations, consisting in alternately plugged parallel square channels, so that the exhaust gases are forced to flow through the porous inner walls: in this way the particles are collected on the surface and in the porosity of the channel walls, progressively blocking the pores. Since the pressure loss increases by the formation of a thick soot cake as the PM is accumulated, the DPF needs to be periodically regenerated by burning off the accumulated soot. The results of our previous deposition and on-line regeneration tests on uncatalysed and Copper-Ferrite catalysed DPF, showed that the simultaneous use of a catalyst properly formulated and microwaves during the regeneration step at lower gas flow rate, allows to reduce the energy supplied and the regeneration time than that required for the uncatalysed filter. Starting by these very promising results, the objectives of this work are to increase the active species load simultaneously modifying the porosimetric characteristics of the support, in order to simultaneously further reduce the PM oxidation temperature and keep low the pressure drop.

Methane steam reforming intensification: Experimental and numerical investigations on monolithic catalysts

Methane steam reforming is still the most economical route for hydrogen production. It generates hydrogen for refining processes, food industry, and recently for fuel cell applications. Recent studies focused on the application of structured catalysts in mass transfer limited-reactions indicated that there are potentially several advantages for monolithic reactor as compared to the packed reactors such as, especially in terms of lower pressure drop and better mass and heat transfer performances. So highly thermal conductive honeycomb structures were proposed as catalyst supports to enhance the heat and material transfer properties of the final catalysts. This work focuses on the experimental testing of the methane steam reforming reaction performed on a Ni-loaded SiC monolith packaged into an externally heated tube. In particular, the two flow configurations of Flow Through and Wall Flow were investigated and compared, the effect of a washcoat deposition was evaluated. The experimental tests indicate that the Wall Flow configuration may overcome the fixed-bed reactor problems, yielding a more uniform temperature distribution and more effective mass transport.

State of the Art of Conventional Reactors for Methanol Production

Abstract Because it is involved in the production of a wide range of added-value chemicals, methanol is one of the most important compounds in the industrial chemistry field. The significant thermodynamic limitations related to methanol synthesis via syngas conversion has intensified interest in this process. Starting with the development of the BASF process at the beginning of the 20th century and the ICI process, introduced in the 1960s, many schemes have been proposed for the overall optimization of the process. This chapter aims to explore the methanol synthesis process and the most relevant technologies available in the methanol industry.

Improved microwave susceptible catalytic diesel particulate filter

Emission standards forced the manufacturers to adopt several aftertreatment devices as effective way to comply with the stringent limits for gaseous and particle emissions. The diesel particulate filter (DPF) is currently the usual aftertreatment system in Diesel engines for soot particle abatement. Among different filter solutions, flow-through filters, such as ceramic foams or open honeycomb structures, are characterized by low pressure drop but by a filtration efficiency of only 40 70%, while wall-flow monoliths, consisting in alternately plugged parallel square channels, so that the exhaust gases flow through the porous inner walls, showed the best balance between filtration efficiency and pressure drop performance. Since pressure loss increases with soot filtration, the DPF needs to be periodically regenerated by burning off the accumulated soot. In our previous work we showed that the simultaneous use of a microwave applicator and a specifically catalysed DPF with a catalyst load up to 30%wt of CuFe2O4, allows to reduce the temperature, the energy and the time required for the filter regeneration with respect to the uncatalysed filter. These results were more evident in particular by adding K to our catalyst formulation and by lowering gas flow rate during the regeneration step. Starting by these very promising results, a procedure to increase the initial medium pore diameter of the bare monoliths was optimized, so aiming at increasing the active species load: in this way the further reduction of soot oxidation temperature is possible, keeping acceptable the pressure drop, and, more important, allowing a decreased regeneration frequency of the filter. The feasibility of the microwave heating technology was also verified by comparing the energy balance of the entire process to the actually employed regeneration technologies.

Catalysts for conversion of synthesis gas

Abstract A more comprehensive exploitation of biosources could be assured by the conversion of biofuels to valuable chemicals. The syngas, obtained by hydrocarbons reforming process, represents the most important reactants mixture for other processes devoted to the production of methanol, higher hydrocarbons (Fischer-Tropsch synthesis), and ammonia. The first two processes are very similar, since they involved main components of syngas in exothermic processes in which a more complex compound is achieved; they are promoted at high pressure and low temperature, for which anyway other side reactions occur (mainly methanation), and each reaction could be considered side-reaction for the other. Such observation remarks the relevance of the catalytic system that should enable desired reactions in the selected operating system. In particular, the Fischer-Tropsch synthesis is widely carried out on cobalt-based catalysts at low temperature, achieving long-chain hydrocarbons as main products; conversely, if low chain is preferred, iron-based catalyst could be employed. Methanol catalysts were effectively developed in the 1960s, in which Cu-ZnO-based formulations appeared very promising both in terms of activity and selectivity. Ammonia synthesis utilized hydrogen obtained by syngas purification (WGS, PROX, and PSA), reducing nitrogen to NH3: such process is thermodynamically promoted at low temperature and high pressure. Iron catalysts are currently used in industrial plants. For all these processes, the very high operating pressure was reflected in a limited catalyst lifetime, so nowadays, studies are focusing in the ability to enlarge catalyst lifetime, by doping active phases or supports. Globally, the exothermic nature of these processes suggests to investigate the effect of highly thermal conductive structured carrier, in order to have a better thermal management in the catalytic volume that could reduce hot spot risks and in turn assure a more stable behavior.

Experimental Investigations on Structured Catalysts in CH4 Steam Reforming Intensification

Highly thermal conductive honeycomb structures were proposed as catalyst supports to enhance the heat and material transfer properties of catalysts. This work focuses on the experimental testing of the methane steam reforming reaction performed on a Ni-loaded SiC monolith packaged into an externally heated tube. In particular, the two flow configurations of Flow Through and Wall Flow were investigated and compared, the impact of a washcoat deposition was evaluated. The experimental tests indicate that the Wall Flow configuration may overcome the fixed-bed reactor problems, yielding a more uniform temperature distribution and more effective mass transport.