A kinetic study of methanol steam reforming over bimetallic Pt/In2O3/Al2O3 catalyst was carried out. The kinetic measurements were performed in a microstructured monolithic reactor with an external ...recycle free of temperature and concentration gradients. By the help of residence time distribution measurements it could be verified that the reactor showed the behaviour of an ideal continuous stirred tank reactor (CSTR). The absence of external and internal concentration gradients could be proven by corresponding experiments and theoretical diagnostic criteria.
The kinetic measurements performed by variation of the reactant inlet partial pressures revealed that in the temperature range from 310°C to 355°C the molar rate of methanol consumption mainly depends on the methanol partial pressure, especially at higher temperatures, whereas there is only minor dependence on the water partial pressure. Carbon dioxide has no inhibiting effect, whereas hydrogen showed a weak inhibiting effect.
Two power laws and three Langmuir-Hinshelwood rate equations were created for the modelling of the kinetic data. Power laws could not be fitted to the measured values. Therefore the uses of Langmuir-Hinshelwood rate laws with temperature dependent sorption constants are inevitable for the modelling. The model discrimination revealed that the rate law derived from a mechanism, which assumes the dehydrogenation of an adsorbed methoxy-species as rate determining step, described the measured kinetic data second best. Optimum agreement between observed and predicted molar rates of methanol consumption was obtained when applying a Langmuir-Hinshelwood rate law assuming dissociative methanol and molecular water adsorption on the catalyst surface. Dissociative adsorption of water and methanol at the same active site may be excluded. This leads to a better evaluation of the models that assume molecular water adsorption at the same site where methanol ties or the ones with no participation of water in the rate determining step (RDS) under discrimination.
•Application of a microreactor with external recycle for kinetic measurements.•Advanced kinetic characterization of a previously patented highly active catalyst.•Highly reproducible performance of the catalyst during kinetic measurements.•Determination of starting values for parameter estimation by simulated annealing.•Derivation of a mechanistic rate model by formulation of Langmuir sorption equilibria.
Ni-based (over MgO and Al2O3) and noble metal-based (Pd and Pt over Al2O3) catalysts were prepared by wet impregnation method and thereafter impregnated in microreactors. The catalytic activity was ...measured at several temperatures, atmospheric pressure and different steam to carbon, S/C, ratios. These conditions were the same for conventional, fixed bed reactor system, and microreactors. Weight hourly space velocity, WHSV, was maintained equal in order to compare the activity results from both reaction systems. For microreactor systems, similar activities of Ni-based catalyst were measured in the steam methane reforming (SMR) activity tests, but not in the case of natural gas steam reforming tests. When noble metal-based catalysts were used in the conventional reaction system no significant activity was measured but all catalysts showed some activity when they were tested in the microreactor systems. The analysis by SEM and TEM revealed a carbon-free surface for Ni-based catalyst as well as carbon filaments growth in case of noble metal-based catalysts.
► Hydrogen production from methane and natural gas steam reforming process was studied. ► Two different reaction systems were used: fixed bed reactor and microreactor systems. ► Ni/MgO catalyst was more selective for WGS reaction than Ni/Al2O3 catalyst. ► Ni/Al2O3 catalyst suffered a quick deactivation in natural gas SR process. ► For Pd/Al2O3 and Pt/Al2O3catalysts a very low activity was measured.
•An alternative approach for H2O2 direct synthesis in dense CO2 was investigated.•Highly active and selective Pd-supported batch catalysts were synthesised.•Decreased catalyst performance in dense ...CO2 in batch mode was observed.•Continuous operation in a micro reactor with dense CO2 improved catalyst activity.
An approach for the direct synthesis of hydrogen peroxide with CO2 as solvent has been explored. Both batch and continuous experiments have been performed. The activity of self-prepared Pd-supported catalysts has been verified leading to high productivity of up to 132 gH2O2 gPd−1 h−1 in batch with selectivities of up to 70%. However, the use of dense CO2 in batch set back catalyst activity leading to the formation of H2O as the only product. For the continuous process in dense CO2 increased performance in terms of productivity with up to 26 gH2O2 gPd−1 h−1 with low selectivity were achieved.
•Bimetallic catalysts coated into microchannel reactors were tested for WGS reaction.•High conversion was achieved at VHSV values as high as 400L/(h gcat).•2.5(Pt-Re) showed highest activity and ...lowest selectivity to undesired methane.•The high Pt/Re ratio on the catalyst surface could explain its superior performance.
In this work Pt based mono and bimetallic catalysts were deposited into microchannel testing reactors and tested under conditions of water-gas shift (WGS). All the catalysts contained 25% of CeO2 and a metal loading of 2.5% or 5.0% (nominal wt.%). The bimetallic catalysts contained 2.5% Pt and 2.5% of Me where Me=Ni, Co, Mo, Pd, Fe, Re, Y, Cu or Zn. The feed gas composition amounted to 46.23% H2, 8.82% CO2, 7.94% CO and 37.02% H2O (vol.%). The tests were performed at reaction temperatures between 300°C and 450°C. 2.1Pt–2.1Re was identified as the catalyst formulation of highest activity. The composition and the preparation method of this catalyst were then modified for further activity and stability improvement. All the catalysts under investigation were characterized applying the following techniques: inductively coupled plasma atomic emission spectroscopy (ICP-AES), N2 physisorption, temperature programmed reduction (TPR), CO chemisorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The activity of the benchmark 3.6Pt catalyst was improved by the 2.1Pt–2.1Re catalyst and the stability of this catalyst was further improved by increasing slightly the nominal Pt content up to 3.33%. Therefore, a significant reduction of the Pt content compared to the benchmark 3.6Pt catalyst was achieved through the incorporation of Re.
Micro-structured fuel processors are under development at IMM for different fuels such as methanol, ethanol, propane/butane (LPG), gasoline and diesel. The target application are mobile, portable and ...small scale stationary auxiliary power units (APU) based upon fuel cell technology. The key feature of the systems is an integrated plate heat-exchanger technology which allows for the thermal integration of several functions in a single device. Steam reforming may be coupled with catalytic combustion in separate flow paths of a heat-exchanger. Reactors and complete fuel processors are tested up to the size range of 5
kW power output of a corresponding fuel cell. On top of reactor and system prototyping and testing, catalyst coatings are under development at IMM for numerous reactions such as steam reforming of LPG, ethanol and methanol, catalytic combustion of LPG and methanol, and for CO clean-up reactions, namely water-gas shift, methanation and the preferential oxidation of carbon monoxide. These catalysts are investigated in specially developed testing reactors. In selected cases 1000
h stability testing is performed on catalyst coatings at weight hourly space velocities, which are sufficiently high to meet the demands of future fuel processing reactors.
► Complete microstructured reactor systems for fuel processing. ► Cheaper fabrication methods for microstructured fuel processors. ► Brief description of complete systems running on LPG, ethanol and ...methanol.
Fuel cell technology has a crucial role to play in future sustainable and distributed energy generation. With the issue of a reliable hydrogen supply in mind, fuel processing of fossil and renewable fuels is a viable option. Mobile and portable power generation systems require a compact hydrogen source when fuel cell technology is applied especially in applications focused on the small scale stationary level. Fuel processing is a feasible option to meet the limited space demands of auxiliary power units (APUs) due to the high energy density of liquid fuels. Many critical issues need to be addressed when microstructured reactors are applied. The most crucial of these are scale-up with respect to system integration, careful control of heat management and an increase in the durability of the catalyst.
Pt–W and Pt–Mo based catalysts were evaluated for methane combustion using a sandwich-type microreactor. Alumina washcoated microchannels were impregnated with platinum in combination with and ...promoted with tungsten and molybdenum and compared with commercially available Pt/Al
2O
3 catalysts. Catalysts were tested in the range of 300–700
°C with flow rates adjusted to GHSV of 74,000
h
−1 and WHSV of 316
L
h
−1
g
−1. Catalysts containing tungsten were found to be the most active and the most stable possibly due to a metal interaction effect. A Pt–W/γ-Al
2O
3 containing 4.6
wt% Pt and 9
wt% W displayed the highest activity with full conversion at 600
°C and a selectivity to CO
2 of 99%.
Different synthesis methods (seeded and unseeded liquid phase hydrothermal synthesis, steam-assisted crystallization) have been employed to prepare zeolite films as catalytic coatings on the channels ...of stainless steel microreactors. The best results were obtained using seeded steam-assisted crystallization (SAC) which under suitable conditions led to well-crystallized zeolite films whose growth was confined to the channel spaces. Liquid phase synthesis yielded higher catalyst loads but was less effective in confining crystal growth to the desired regions. Once the zeolite films were formed, conventional ion-exchange procedures were used to produce a homogeneous distribution of Pt in the zeolite films.
The reaction between ethanol and water was studied in the temperature range of 400–600°C at atmospheric pressure over supported catalysts in a microchannel reactor. The supported catalysts prepared ...by washcoating and impregnation were active in the ethanol steam reforming but differ in their performance. The metal nature, metal loading and type of the carriers markedly influence the catalytic activity and selectivity of the catalysts. Among them Rh-based catalysts exhibited the highest catalytic activity, as compared to Co and Ni-based catalysts. Bimetallic Rh-Ni catalysts exhibit significant improvement in terms of ethanol conversion and hydrogen selectivity and the promoting role of the Ni and CeO2 addition is discussed. The bimetallic Rh-Ni catalyst promoted by CeO2 was stable for at least 100h without any detectable degradation in performance.
