In this work biogas valorization – a renewable resource – for synthesis gas and hydrogen generation through dry reforming or tri-reforming (TR) is studied. Several Ni-based catalysts and a bimetallic ...Rh–Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 were used. For all the experiments, a synthetic biogas (molar composition: 60% CH4 and 40% CO2) was fed and the catalytic activities were measured in two different experimental facilities: a bench-scale fixed bed reactor system and a microreactor reaction system, at 1073 K and atmospheric pressure. Those catalysts which achieved high activity and stability in the fixed-bed reactor were impregnated in a microreactor to explore possible process intensification. For TR processes, different steam to carbon ratios, S/C, from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were used. The high methane and carbon dioxide conversions reached in the fixed bed reactor were also achieved in the microreactor operating at much higher WHSV. In addition, process intensification improved catalysts stability. Physicochemical characterization of catalyst samples by ICP-OES, N2 physisorption, H2 chemisorption, TPR, SEM and XPS showed differences in chemical state, metal–support interactions, average crystallite sizes and redox properties of nickel and rhodium metal particles, indicating the importance of the morphological and surface properties of metal phases in driving the reforming activity.
► High methane and carbon dioxide conversions were reached in biogas DR process. ► For TR process at O2/CH4 = 0.25 and S/C = 1.0 the highest hydrogen yields were reached. ► The Rh–Ni/Ce–Al2O3 catalyst achieved the highest hydrogen production yield. ► Similar conversions were achieved at much higher WHSV in microreactors. ► Higher TOF and PROD values were obtained operating with microreactors.
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.
Nickel catalysts supported on Al
2
O
3
, Al
2
O
3
-CeO
2
, Al
2
O
3
-La
2
O
3
, and Al
2
O
3
-CeO
2
-La
2
O
3
were synthesized
via
the sol-gel method in acidic solution. The influence of the chemical ...composition and textural properties of the catalysts on oxidative steam reforming of methane was studied. Methane, oxygen, nitrogen and steam were fed into a fixed bed reactor and tested under atmospheric pressure at 550 °C, with O/C ratio = 0.3, S/C ratio = 1.0, and WHSV = 170.8 h
−1
. During 6 h of reaction, methane conversion and hydrogen selectivity were determined. Although lanthanide oxides are known to have excellent features, the addition of ceria or lanthana did not improve the catalytic performance of the Ni/Al
2
O
3
system. Nevertheless the addition of both dopants was needed to end up with a stable catalyst. Characterization results revealed a low crystallite size (40 Å), a high fraction of accessible Ni
0
species (73.6%), migration of nickel and ceria from the bulk to the surface during activity tests, and a very low amount of coke deposited (4.7 mg C per g catalyst) on the Ni/Al
2
O
3
-CeO
2
-La
2
O
3
catalyst that resulted in high catalytic activity.
Nickel supported on Al
2
O
3
-CeO
2
-La
2
O
3
provided excellent catalytic features and high coking resistance in oxidative steam reforming of methane.
In this work, a renewable source, biogas, was used for synthesis gas and hydrogen generation by steam reforming (SR) or oxidative reforming (OR) processes. Several Ni-based catalysts and a bimetallic ...Rh–Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 were used. For all the experiments, a synthetic biogas which consisted of 60% CH4 and 40% CO2 (vol.) was fed and tested in a fixed bed reactor system and in a microreactor reaction system at 1073 K and atmospheric pressure. The catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. For the SR process different steam to carbon ratios, S/C, varied from 1.0 to 3.0 were used. In the case of OR process the O2/CH4 ratio was varied from 0.125 to 0.50. Comparing conventional and microreactor reaction systems, one order of magnitude higher TOF and productivity values were obtained in the microreactors, while for all the tested catalysts a similar activity results were achieved. Physicochemical characterization of catalysts samples by ICP-AES, N2 physisorption, H2 chemisorption, TPR, SEM, XPS and XRD showed differences in chemical state, metal–support interactions, average crystallite sizes and redox properties of nickel and rhodium metal particles, indicating the importance of the morphological and surface properties of metal phases in driving the reforming activity.
► In biogas SR process lower CO2 conversions were measured increasing the S/C ratio. ► In biogas OR process at O2/CH4 = 0.25 the best operation conditions were measured. ► Rh–Ni/Ce–Al2O3 and Ni/Ce–Zr–Al2O3 catalysts were the most active catalysts. ► In microreactors, at higher WHSV similar conversions were achieved.
In this work carbon dioxide methanation was performed in order to produce methane. This process is known as “Power-to-Gas”, which uses the excess of electricity produced from renewable sources to ...generate hydrogen via water electrolysis. This hydrogen can react with carbon dioxide, obtained from different industrial processes, to generate methane that can be stored, burned or injected into the existing natural gas grid. Thus, different catalysts supported on alumina and cerium/zirconium modified alumina were prepared, using nickel as main active metal and with the addition of small amounts of noble metals, rhodium and ruthenium, in order to increase their catalytic activity. Addition of noble metals increased the dispersion and the reducibility of the nickel species, whilst support modifiers increased the amount of nickel oxide with moderate interaction with the support and non-stoichiometric nickel aluminate species. These species proved to be related with the catalytic activity. For the catalysts tested, promising results were obtained between 640 and 700 K with a methane yield of 70%.
•Thermodynamic equilibrium reached at high temperatures.•Noble metals enhanced catalytic activity at low temperatures.•Nickel oxide and non-stoichiometric nickel aluminate proved to be the active phases for methanation reaction.
•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.
In this work, Pt based mono and bimetallic catalysts were tested under conditions of tri-reforming (TR). All the catalysts contained 25% of CeO
2
and a metal loading of 2.5 or 5.0% (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. For all the experiments, a synthetic biogas which consisted of 60% CH
4
and 40% CO
2
(vol.) was mixed with water, S/C = 1.0, and oxygen, O
2
/CH
4
= 0.25, and fed to a fixed bed reactor (FBR) system or a microreactor. The 2.5Pt catalyst was used in order to compare the performance of each reaction system. The tests were performed at reaction temperatures between 700 and 800 °C, and at volume hourly space velocities (VHSV) between 100 L
N
/(h g
cat
) and 200 L
N
/(h g
cat
) for the FBR system and between 1000 L
N
/(h g
cat
) and 2000 L
N
/(h g
cat
) for the microreactor, at atmospheric pressure. Then, all catalysts were deposited into microchannel reactors and tested at a constant VHSV of 2000 L
N
/(h g
cat
) and reaction temperatures between 700 and 800 °C. Catalysts under investigation were characterized applying the following techniques: inductively coupled plasma optical emission spectroscopy (ICP-OES), N
2
Physisorption, Temperature Programmed Reduction (TPR), CO chemisorption, Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The microreactor was identified as the most efficient and promising reaction system, and the 2.5(Pt–Pd) catalyst as the bimetallic formulation with the highest activity. Therefore its activity and stability was compared with the reference 5.0Pt catalyst at 700 °C and VHSV of 2000 L
N
/(h g
cat
) for more than 100 h. Although slightly lower activity was measured operating with the 2.5(Pt–Pd) catalyst, a significant reduction of the Pt content compared to the reference 5.0Pt catalyst was achieved through the incorporation of Pd.
In this paper, the hydrogen storage capacity of some synthetic and natural iron oxides is presented. The results of the activity tests and characterization techniques of natural and synthetic iron ...oxides (N
2
adsorption–desorption isotherms, temperature-programmed reduction, X-ray diffraction, and plasma atomic emission spectroscopy) suggest that the use of chromium on iron oxide systems improved their hydrogen storage capacity. This is related to the capacity of chromium to modify the iron oxide reduction profile when Cr was incorporated. A direct reduction from Fe
3
O
4
to Fe was observed as the mechanism for H
2
storage. In addition, natural oxides as commercial Superfine and Densinox-L oxides are proved to be suitable materials to store and purify H
2
due to their high stability during different cycles of reduction and oxidation. The best results among the natural ones were Densinox-L and among the synthetic ones Fe–10Cr.
Testing water meters is essential for efficient management of water resources, and compliance with regulations, water utilities should have a regular testing schedule to ensure that they are ...providing accurate readings. This highlights the importance of creating and installing water meter test benches that enable accurate calibration for laboratories, industries, and water meter manufacturers. The diverter is an essential part of a flow meter calibration system, and its compliance with standards, is crucial. These standards emphasize the need for quick diversion of flow without changing the flow-rate during the measuring interval. To accomplish this, complex, expensive and large flow diverters are typically utilized, which incorporate a manifold that homogenizes the liquid and produces a sheet of water at atmospheric pressure. This work presents a new diverter switch valve that fulfils with the technical characteristics of a flow diverter established in the international standards, it does not require any nozzle or fishtail transition and it works without long atmospheric liquid sheet. The experiments carried out with different diversion systems compare the results using a conventional design and the new valve. Good repeatability and acceptable uncertainty are obtained using both systems. Hence, this innovative diverter valve presents an opportunity to minimize the size and lower the costs of facilities, thereby enabling a reevaluation of the design, installation, and commissioning of laboratories dedicated to flow meter calibration.
•This novel valve offers the possibility of minimizing the size of the facilities.•The valve does not require nozzle or fishtail transition and works under pressure.•Two diverting systems were compared in the same experimental facility.•The valve fulfils the international standards for a flow diverter.
