Metal foam-supported Pd–Rh catalyst for steam methane reforming and its application to SOFC fuel processing

Pd–Rh/metal foam catalyst was studied for steam methane reforming and application to SOFC fuel processing. Performance of 0.068 wt% Pd–Rh/metal foam catalyst was compared with 13 wt% Ni/Al₂O₃ and 8 wt% Ru/Al₂O₃ catalysts in a tubular reactor. At 1023 K with GHSV 2000 h⁻¹ and S/C ratio 2.5, CH₄ conversion and H₂ yield were 96.7% and 3.16 mol per mole of CH₄ input for Pd–Rh/metal foam, better than the alumina-supported catalysts. In 200 h stability test, Pd–Rh/metal foam catalyst exhibited steady activity. Pd–Rh/metal foam catalyst performed efficiently in a heat exchanger platform reactor to be used as prototype SOFC fuel processor: at 983 K with GHSV 1200 h⁻¹ and S/C ratio 2.5, CH₄ conversion was nearly the same as that in the tubular reactor, except for more H₂ and CO₂ yields. Used Pd–Rh/metal foam catalyst was characterized by SEM, TEM, BET and CO chemisorption measurements, which provided evidence for thermal stability of the catalyst.     

Steam reforming of ethanol over bimetallic RhPt/La2O3: Long-term stability under favorable reaction conditions

Recently, the steam reforming of biofuels has been presented as a potential hydrogen source for fuel cells. Because this scenario represents an interesting opportunity for Colombia (South America), which produces large amounts of bioethanol, the steam reforming of ethanol was studied over a bimetallic RhPt/La₂O₃ catalyst under bulk mass transfer conditions. The effect of temperature and the initial concentrations of ethanol and water were evaluated at space velocities above 55,000 h⁻¹ to determine the conditions that maximize the H₂/CO ratio and reduce CH₄ production while maintaining 100% conversion of ethanol. These requirements were accomplished when 21 mol% H₂O and 3 mol% C₂H₅OH (steam/ethanol molar ratio = 7) were reacted at 600 °C. The catalyst stability was assessed under these reaction conditions during 120 h on stream, obtaining ethanol conversions above 99% during the entire test. The effect of both H₂ and air flows as catalyst regeneration treatments were evaluated after 44 and 67 h on stream, respectively. The results showed that H₂ treatment accelerated catalyst deactivation, and air regeneration increased both the catalyst stability and the H₂ selectivity while decreasing CH₄ generation. Fresh and spent catalyst samples were characterized by TEM/EDX, XPS, TPR, and TGA. Although the Rh and Pt in the fresh catalyst were completely reduced, the spent samples showed a partial oxidation of Rh and small amounts of carbonaceous residue. A possible Rh–Pt–Rh₂O₃ structure was proposed as the active site on the catalyst, which was regenerated by air treatment.     

Combined dry reforming and partial oxidation of methane to synthesis gas on noble metal catalysts

In this paper CO₂ reforming of methane combined with partial oxidation of methane to syngas over noble metal catalysts (Rh, Ru, Pt, Pd, Ir) supported on alumina-stabilized magnesia has been studied. The catalysts were characterized by using BET, XRD, SEM, TEM, TPR, TPH and H₂S chemisorption techniques. The H₂S chemisorption analysis showed an active metal crystallite size in the range of 1.8-4.24 nm for the prepared catalysts. The obtained results revealed that the Rh and Ru catalysts showed the highest activity in combined reforming and both the dry reforming and partial oxidation of methane. The obtained results also showed a high catalytic stability without any decrease in methane conversion up to 50 h of reaction. In addition, the H₂/CO ratio was around 2 and 0.7 over different catalysts for catalytic partial oxidation and dry reforming, respectively.     

Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/γ-Al2O3-based mixed oxides on hydrogen production

Autothermal reforming (ATR) of iso-octane in the presence of Rh-based catalysts (0.5 wt% of Rh) supported onto γ-Al₂O₃, CeO₂, and ZrO₂ were initially carried out at 700 °C with a S/C ratio of 2.0, an O/C ratio of 0.84, and a gas hourly space velocity (GHSV) of 20,000 h⁻¹. The activity of Rh/γ-Al₂O₃ was found to be higher than Rh/CeO₂ and Rh/ZrO₂, with H₂ and (H₂ + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/γ-Al₂O₃ material, however, was potentially susceptible to carbon coking and produced 3.5 wt% of carbon deposits following the reforming reaction, as evidenced by C, H, N, and S elemental analysis. In contrast, Rh/CeO₂ catalyst exhibited lower activity but higher stability than Rh/γ-Al₂O₃, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/γ-Al₂O₃ with high stability from Rh/CeO₂, Rh/CeO₂/γ-Al₂O₃ catalysts with different CeO₂ contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/γ-Al₂O₃, the newly prepared Rh/CeO₂/γ-Al₂O₃ catalysts (0.5 wt% of Rh and 20 wt% of CeO₂) showed even enhanced activity during 10 h, and H₂ and (H₂ + CO) yields were calculated to be 2.08 and 2.62 mol/mol C, respectively. In addition, as observed with Rh/CeO₂, the catalyst was further found to be stable with less than 0.3 wt% of carbon deposition after 10 h. The Rh/γ-Al₂O₃ and Rh/CeO₂/γ-Al₂O₃ catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/γ-Al₂O₃ catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO₂/γ-Al₂O₃ catalyst proved to be excellent in terms of stability against coke formation as well as activity towards the desired reforming reaction, maintaining its ability for H₂ production for 100 h.     

CNT-based catalysts for H2 production by ethanol reforming

Hydrogen production by steam reforming of ethanol (SRE) was studied using steam-to-ethanol ratio of 3:1, between the temperature range of 150–450 °C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al₂O₃). The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures. The idea to develop CNT-based catalysts that have high selectivity for H₂ is one of the driving forces for this study. The catalytic performance was evaluated in terms of ethanol conversion, product gas composition, hydrogen yield and selectivity to hydrogen. The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied. Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 °C. The highest hydrogen yield of 2.5 is, however, obtained over the Co/CNT catalyst at 450 °C. The formation of CO and CH₄ was very low over the Co/CNT catalyst compared to all the other tested catalysts. The Pt and Rh CNT-based catalysts were found to have low activity and selectivity in the SRE reaction. Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e.g. the fuel cell applications.     

Ni/Ru–Mn/Al2O3 catalysts for steam reforming of toluene as model biomass tar

The catalytic steam reforming of the major biomass tar component, toluene, was studied over two commercial Ni-based catalysts and two prepared Ru–Mn-promoted Ni-base catalysts, in the temperatures range 673–1073 K. Generally, the conversion of toluene and the H₂ content in the product gas increased with temperature. A H₂-rich gas was generated by the steam reforming of toluene, and the CO and CO₂ contents in the product gas were reduced by the reverse Boudouard reaction. A naphtha-reforming catalyst (46-5Q) exhibited better performance in the steam reforming of toluene at temperatures over 873 K than a methane-reforming catalyst (Reformax 330). Ni/Ru–Mn/Al₂O₃ catalysts showed high toluene reforming performance at temperatures over 873 K. The results indicate that the observed high stability and coking resistance may be attributed to the promotional effects of Mn on the Ni/Ru–Mn/Al₂O₃ catalyst.     

Effect of preparation methods on the performance of Ni/Al2O3 catalysts for aqueous-phase reforming of ethanol: Part I-catalytic activity

The effect of preparation method on the performance of Ni/Al₂O₃ catalysts for aqueous-phase reforming of ethanol (EtOH) has been investigated. The first catalyst was prepared by a sol–gel (SG) method and for the second one the Al₂O₃ support was made by a solution combustion synthesis (SCS) route and then the metal was loaded by standard wet impregnation. The catalytic activity of these catalysts of different Ni loading was compared with a commercial Al₂O₃ supported Ni catalyst [CM (10%)] at different temperatures, pressures, feed flow rates, and feed concentrations. Based on the product distribution, the proposed reaction pathway is a mixture of dehydrogenation of EtOH to CH₃CHO followed by C–C bond breaking to produce CO + CH₄ and oxidation of CH₃CHO to CH₃COOH followed by decarbonylation to CO₂ + CH₄. CH₄(C₂H₆ and C₃H₈) also can form via Fischer–Tropsch reactions of CO/CO₂ with H₂. The CH₄ (C₂H₆ and C₃H₈) reacts to form hydrogen and carbon monoxide through steam reforming, while CO converts to CO₂ mostly through the water–gas shift reaction (WGSR). SG catalysts showed poorer WGSR activity than the SCS catalysts. The activation energies for H₂ and CO₂ production were 153, 155 and 167 kJ/mol and 158, 160 and 169 kJ/mol for SCS (10%), SG (10%), and CM (10%) samples, respectively.     

Pathways of ethanol steam reforming over ceria-supported catalysts

Ceria-supported Pt, Ir and Co catalysts are prepared herein by the deposition–precipitation method and investigated for their suitability in the steam reforming of ethanol (SRE) at a temperature range of 250–500 °C. SRE is tested in a fixed-bed reactor under an H₂O/EtOH molar ratio of 13 and 20,000 h⁻¹ GHSV. Possible pathways are proposed according to the assigned temperature window to understand the different catalysts attributed to specific reaction pathways. The Pt/CeO₂ catalyst shows the best carbon–carbon bond-breaking ability and the lowest complete ethanol conversion temperature of 300 °C. Acetone steam reforming over the Ir/CeO₂ catalyst at 400 °C promotes a hydrogen yield of up to 5.3. Lower reaction temperatures for the water–gas shift and acetone steam reforming are in evidence for the Co/CeO₂ catalyst, whereas the carbon deposition causes its deactivation at temperature over 500 °C.     

Production of syngas from steam reforming and CO removal with water gas shift reaction over nanosized Zr0.95Ru0.05O2−δ solid solution

This study presents the synthesis, characterization, and kinetics of steam reforming of methane and water gas shift (WGS) reactions over highly active and coke resistant Zr_0.95Ru_0.05O_2−δ. The catalyst showed high activity at low temperatures for both the reactions. For WGS reaction, 99% conversion of CO with 100% H₂ selectivity was observed below 290 °C. The detailed kinetic studies including influence of gas phase product species, effect of temperature and catalyst loading on the reaction rates have been investigated. For the reforming reaction, the rate of reaction is first order in CH₄ concentration and independent of CO and H₂O concentration. This indicates that the adsorptive dissociation of CH₄ is the rate determining step. The catalyst also showed excellent coke resistance even under a stoichiometric steam/carbon ratio. A lack of CO methanation activity is an important finding of present study and this is attributed to the ionic nature of Ru species. The associative mechanism involving the surface formate as an intermediate was used to correlate experimental data.     

Autothermal reforming of ethanol on noble metal catalysts

Autothermal reforming of ethanol on zirconia-supported Rh and Pt mono- and bimetallic catalysts (0.5 wt-% total metal loading) was studied as a source of H₂-rich gas for fuel cells. The results were compared with those obtained on a commercial steam reforming catalyst (15 wt-% NiO/Al₂O₃). The Rh-containing catalysts exhibited the highest selectivity for H₂ production and were stable in 24 h experiments. The formation of carbonaceous deposits was lower on the noble metal catalysts than on the commercial NiO/Al₂O₃ catalyst. Thus, the Rh-containing catalysts are more suitable than the commercial NiO/Al₂O₃ catalysts for the ATR of ethanol.     

Hydrogen production by oxidative ethanol reforming on Co, Ni and Cu ex-hydrotalcite catalysts

Five Co, Ni and Cu oxides derived from hydrotalcite-like precursors (ex-LDHs) were prepared and tested in the oxidative steam reforming reaction of ethanol under autothermal conditions. Highly crystalline LDH-precursors were obtained using urea hydrolysis method and both the precursors and the calcined ex-LDH oxides were characterized with several physical and chemical techniques. It has been shown that the particle size of the segregated active metal oxide decreases upon increasing the crystallinity of the LDH-precursor. Moreover, these small particle sizes favour the strong interactions between active metals and the amorphous matrix of Al-modifying cations, which cause a high stabilization of the active metal phases.All the ex-LDH catalysts (Co-Zn-Al, Co-Mg-Al, Co-Al, Ni-Mg-Al and Cu-Mg-Al) were tested in the oxidative steam reforming of ethanol with EtOH/H₂O molar ratio (nH₂O/nEtOH) of 2.28 and O₂/EtOH molar ratio (nO₂/nEtOH) of 0.36, at temperatures of 848-898-948 K. All ex-LDH catalysts, apart from Cu-catalyst, reached the full ethanol conversion in the temperature range, and H₂ and CO₂ were the main reaction products. Thus, high absolute H₂ production values of 14.5 L(STP) h⁻¹ g_cat⁻¹ at 848 K with CoZnAl ex-LDH catalyst and nearly 18 L(STP) h⁻¹ g_cat⁻¹ at 948 K with CoAl and CoMgAl catalysts were reached, which means H₂ selectivity values of 85% at 848 K and 89% at 948 K, respectively.     

Ni/MgAl2O4 catalyst for low-temperature oxidative dry methane reforming with CO2

Oxidative dry reforming of methane has been performed for 100 h on stream using Ni supported on MgAl₂O₄ spinel at different loadings at 500–700 °C, CO₂/CH₄ molar ratio of 0.76, and variable O₂/CH₄ molar ratio (0.12–0.47). Syngas with an H₂/CO ratio of 1.5–2.1 has been produced by manipulating reforming feed composition and temperature. The developed oxidative dry reforming process allowed high CH₄ conversion at all conditions, while CO₂ conversion decreased significantly with the lowering of the reforming temperature and increasing O₂ concentration. When considering both greenhouse gas conversions and H₂/CO ratio enhancement, the optimal reforming condition should be assigned to 550 °C and O₂/CH₄ molar ratio of 0.47, which delivered syngas with H₂/CO ratio of 1.5. Coke-free operation was also achieved, due to the combustion of surface carbon species by oxygen. The 3.4 wt% Ni/MgAl₂O₄ catalyst with a mean Ni nanoparticle diameter of 9.8 nm showed stable performance during oxidative dry reforming for 100 h on stream without deactivation by sintering or coke deposition. The superior activity and stability of MgAl₂O₄ supported Ni catalyst shown during reaction trials is consistent with characterization results from XRD, TPR, STEM, HR-STEM, XPS, and CHNS analysis.     

Novel zeolite-supported rhodium catalysts for ethanol steam reforming

Renewable bioethanol is an interesting hydrogen source for fuel cells through steam reforming, but its C–C bond promotes parallel reactions, mainly coke and by-products formation. In this way, good ethanol reforming catalysts are still needed, which explains current research and development efforts around the world. Most catalysts proposed for ethanol reforming are based on oxide-supported noble metals with surface area below 100 m² g⁻¹ and reaction temperatures above 500 °C. Novel Rh and Rh–K catalysts supported on NaY zeolite with surface area above 440 m² g⁻¹ are presented in this work. Reaction temperature was fixed at 300 °C and H₂O/EtOH molar ratio and reagent flow were varied. Ethanol conversion varied from 50 to 99%, with average increase of 50% due to K promoter, and hydrogen production yield achieved 68%.     

Hydrogen production from steam reforming of ethanol using a ceria-supported iridium catalyst: Effect of different ceria supports

Catalytic activity of a ceria-supported Iridium (Ir/CeO₂) catalyst was investigated for steam reforming of ethanol within a temperature range of 300–500 °C. Three types of ceria were chosen to prepare the catalyst: commercial [assigned as CeO₂(C)] and prepared [using a simple reduction–oxidation method, CeO₂(R), and another combined with ultrasonic irradiation, CeO₂(U)] ceria. The Ir/CeO₂ catalyst with Ir loading of 2 wt.% was prepared by deposition–precipitation using iridium chloride (IrCl₃) as a precursor at 75 °C and pH = 9 (adjusted with 0.25 M Na₂CO₃). Catalytic activities toward the steam reforming of ethanol (SRE) were tested in a fixed-bed reactor. In order to better understand the effect of activation conditions of a catalyst on the reforming of ethanol, reduction pretreatment at 200 and 400 °C (assigned as H₂ and H₄) were conducted. The results indicated that only less sintering influences the catalytic activities for high temperature reduction. The ethanol conversion approached completion around 450 °C via reduction pretreatment for Ir/CeO₂(U) and Ir/CeO₂(C) samples under H₂O/EtOH molar ratio of 13 and 22,000 h⁻¹ GHSV. Not only was a high dispersion of both catalysts present but also no impurities (e.g., boron) interfered with the catalytic activities. The hydrogen yield (H₂ mole/EtOH mole) exceeds 5.0 with less content of CO and CH₄ (<2%).     

The active phase of NaCo/ZnO catalyst for ethanol steam reforming: EXAFS and in situ XANES studies

The NaCo/ZnO catalyst was prepared by a co-precipitation method and the active phase for the catalyst was studied. Extended X-ray absorption fine structure (EXAFS) studies were used to obtain structural parameters of the active phase of the catalyst. In situ X-ray absorption near edge structure (XANES) studies were also employed to better understand the phase transition of the catalyst in the course of H₂-temperature-programmed reduction followed by ethanol steam reforming. The XANES analysis confirmed that the oxidic precursor of Co₃O₄ phase was transformed to CoO followed by Co metal in the course of H₂-TPR, and the Co metal phase remained stable during the reaction. The EXAFS analysis for the fresh and spent catalyst samples revealed that the characteristic features corresponding to Co–Co distance of Co metallic phase were being developed during reaction, which demonstrated that Co phase is most likely the active phase of NaCo/ZnO catalyst for the ethanol steam reforming. The catalytic activity in ethanol steam reforming for hydrogen production over the oxidized and reduced catalyst samples was measured at 773 K and 1 atm in a fixed bed reactor using a model liquid feed containing 21 vol% ethanol in water. The prereduced NaCo/ZnO catalyst gave high ethanol conversion of 99% with product distributions of 73.0% H₂, 2.2% CO, 22.1% CO₂, and 2.7% CH₄, while the calcined oxidic one exhibited poor ethanol conversion below 44% at 773 K.     

Study on hydrogen-rich syngas production by dry autothermal reforming from biomass derived gas

In this study, the H₂-rich syngas (H₂ + CO) production from biomass derived gas (BDG) by dry autothermal reforming (DATR) is investigated. Methane and carbon dioxide is the major composition of biomass derived gas. DATR reaction combined benefits of partial oxidation (POX) and dry reforming (DR) reaction was carried out in this study. The reforming parameters on the conversion of methane and syngas selectivity were explored. The reforming parameters included the fuel feeding rate, CO₂/CH₄ and O₂/CH₄ molar ratios. The experimental results demonstrated that it not only supplied the energy required for self-sustained reaction, but also avoided the coke formation by dry autothermal reforming. It has a wide operation region to maintain the moderate production of the syngas. During the reforming process, the reformate gas temperature was between 650 and 900 °C, and energy loss percentage in reforming process was between 15 and 30%. Further, high CO₂ concentration in the reactant had a considerable influence on the heat release of oxidation, and thereby decreased the reformate gas temperature. It caused the reduction of synthesis gas concentration and assisting/impeding combustion composition (A/I) ratio. However, it was favorable to CO selectivity because of the reverse water-gas shifting reaction. The H₂/CO molar ratio between 1 and 2 was achieved by varying CO₂/CH₄ molar ratio. However, the syngas concentrations were affected by CO₂/CH₄ and O₂/CH₄ molar ratio.     

Combined pre-reformer/reformer system utilizing monolith catalysts for hydrogen production

The pre-reforming of higher hydrocarbon, propane, was performed to generate hydrogen from LPG without carbon deposition on the catalysts. A Ru/Ni/MgAl₂O₄ metallic monolith catalyst was employed to minimize the pressure drop over the catalyst bed. The propane pre-reforming reaction conditions for the complete conversion of propane with no carbon formation were identified to be the following: space velocities over 2400 h⁻¹ and temperatures between 400 and 450 °C with a H₂O/C₁ ratio of 3. The combined pre-reformer and the main reformer system with the Ru/Ni/MgAl₂O₄ metallic monolith catalyst was employed to test the conversion propane to syngas where the reaction heat was provided by catalytic combustors. Propane was converted in the pre-reformer to 52.5% H₂, 27.0% CH₄, 17.5% CO, and 3.0% CO₂ with a 331 °C inlet temperature and a 482 °C catalyst outlet temperature. The main steam reforming reactor converted the methane from the pre-reformer with a conversion of higher than 99.0% with a 366 °C inlet temperature and an 824 °C catalyst outlet temperature. With a total of 912 cc of the Ru/Ni/MgAl₂O₄ metallic monolith catalyst in the main reformer, the H₂ production from the propane reached an average of 3.25 Nm³h⁻¹ when the propane was fed at 0.4 Nm³h⁻¹.     

Autothermal reforming study of diesel for fuel cell application

Diesel is one of the best hydrogen storage systems, because of its very high hydrogen volumetric density (100 kg H₂ m⁻²) and gravimetric density (15% H₂). In this study, several catalysts were selected for diesel reforming. Three experimental catalysts (Pt on gadolinium-doped ceria, Rh and Ru on the same support) and two commercial catalysts (FCR-HC14 and FCR-HC35, Süd-Chemie, Inc.) were used to reform diesel. The effects of operating conditions, such as temperature, O₂/C16 and H₂O/C16 on autothermal reforming (ATR) were investigated. In addition, by analyzing the concentrations of products and the temperature profiles along the catalyst bed, we studied the reaction characteristics for a better understanding of the ATR reaction. The fuel delivery and heat transfer between the front exothermic part and the rear endothermic part of the catalyst bed were found to be significant. In this study, the characteristic differences between a surrogate fuel (C₁₆H₃₄) and commercial grade diesel for the ATR were also examined.     

Potassium promoted Ru/meso-macroporous SiO2 catalyst for the preferential oxidation of CO in H2-rich gases

A series of potassium promoted Ru/meso-macroporous SiO₂ catalysts were prepared and used for the preferential oxidation of CO (CO-PROX) in H₂-rich gases. The catalysts were characterized by using techniques of TEM, SEM TPR, XPS, and N₂ adsorption/desorption. The catalytic activity of Ru/meso-macroporous SiO₂ was markedly improved by the introduction of potassium. The catalyst of K-5 wt.% Ru/meso-macroporous SiO₂ with molar ratio of K:Ru = 5:7 exhibited relatively high activity and selectivity for CO-PROX. Nanoparticles of ruthenium species can be highly dispersed on the meso-macroporous SiO₂ support by the simple impregnation method. The addition of potassium weakened the interaction between metallic Ru and the silica support. Lowering the reduction temperature of ruthenium ions could keep ruthenium in the state of metallic Ru, and it was proposed that potassium acted as an electron donating agent. The electron donating effect of potassium improved the low temperature activity for CO oxidation and increased the selectivity of O₂ for CO oxidation, thus K-modified Ru/meso-macroporous SiO₂ catalyst showed obviously a wide temperature window for CO elimination from H₂-rich gases, meanwhile the related mechanism was discussed.     

Hydrogen production via steam reforming of methanol over Cu/(Ce,Gd)O2−x catalysts

Hydrogen production via steam reforming of methanol is carried out over Cu/(Ce,Gd)O_2−x catalysts at 210–600 °C. The CO content in reformate is about 1% at 210–270 °C, which are the typical temperature for hydrogen production via steam reforming of methanol. Largest H₂ yield and CO₂ selectivity and smallest CO content are obtained at 240 °C. The formation rate of CO increases with increasing temperature. The average formation rate of CO becomes larger than that of CO₂ at about 450 °C. The H₂ yield, the CO₂ selectivity and the CO content become constant at about 550 °C. At 240 °C, the smallest CO content is obtained with a catalyst weight of 0.5 g and a Cu content of 3 wt%. The H₂ yield, defined as H₂/(CO + CO₂) in formation rates, at 240 °C is always 3 and not affected by the variations of either the catalyst weight or the Cu content.