Time On Stream Research Articles

Role of promoters over yttria‐zirconia supported Ni catalyst for dry reforming of methane

AbstractDry reforming of methane (DRM) bears great hope for the catalytic community as well as environmentalists for its potential to convert two greenhouse gases, CH4 and CO2, together into synthetic feedstock “syngas”. The stable tetragonal zirconium yttrium oxide phase over the “Yttria‐zirconia supported Ni” catalyst (Ni/YZr) brings >70% CH4 conversion against 50% CH4 conversion over zirconia supported Ni catalyst) in 7 h time‐on‐stream (TOS). The use of the second metal oxide (MOx; M = Ho, Ga, Gd, Ba, Cs) in a small amount (4 wt%) over Ni/YZ catalyst is found to promote the catalytic activity further. Herein, we have prepared such metal‐promoted yttria‐zirconia supported Ni catalyst, employed them for DRM and characterized them with surface area porosity, X‐ray diffraction, spectroscopic techniques, temperature programmed techniques and transmission electron microscopy. A fine correlation of characterization results with catalytic activity brings out various useful information that would be useful for establishing yttria‐zirconia supported Ni catalyst for DRM. Ni stabilized over cubic zirconium holmium oxide phase in 5Ni4Ho/YZr catalyst, cubic zirconium gadolinium oxide phase in 5Ni4Gd/YZr catalyst and cubic zirconium barium oxide phase in 5Ni4Ba/YZr catalyst perform excellent toward DRM. Catalytically, 5Ni4Ho/YZr catalyst achieves CH4 conversion as high as ~85% whereas 5Ni4Ba/YZr and 5Ni4Gd/YZr show CH4 conversions of about ~80%. Even in 30 h TOS study, 5Ni4Ho/YZr catalyst showed >81% CH4 conversion with retaining highest H2/CO (0.97).

Ni-Based Hydrotalcite (HT)-Derived Cu Catalysts for Catalytic Conversion of Bioethanol to Butanol.

Catalytic conversion of biomass-derived ethanol into n-butanol through Guerbet coupling reaction has become one of the key reactions in biomass valorization, thus attracting significant attention recently. Herein, a series of supported Cu catalysts derived from Ni-based hydrotalcite (HT) were prepared and performed in the continuous catalytic conversion of ethanol into butanol. Among the prepared catalysts, Cu/NiAlOx shows the best performance in terms of butanol selectivity and catalyst stability, with a sustained ethanol conversion of ~35% and butanol selectivity of 25% in a time-on-stream (TOS) of 110 h at 280 °C. While for the Cu/NiFeOx and Cu/NiCoOx, obvious catalyst deactivation and/or low butanol selectivity were obtained. Extensive characterization studies of the fresh and spent catalysts, i.e., X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Hydrogen temperature-programmed reduction (H2-TPR), reveal that the catalysts' deactivation is mainly caused by the support deconstruction during catalysis, which is highly dependent on the reducibility. Additionally, an appropriate acid-base property is pivotal for enhancing the product selectivity, which is beneficial for the key process of aldol-condensation to produce butanol.

Direct steam reforming of the product gas from ethanol gasification with supercritical water

A continuous process for producing hydrogen from the gasification of ethanol with supercritical water (SCWG) is investigated, which involves a fixed bed steam methane reforming (SMR) reactor downstream of the SCWG reactor. Increasing temperature and decreasing space velocity in the SMR reactor resulted in increased hydrogen concentration and methane conversion. The catalyst activity was more affected at low than high pressures, presumably due to the kinetics of the SMR reaction. The significant increase in total hydrogen yield based on ethanol in the feed showed the importance of installing the reformer after gasification. The excessive steam from the SCWG reactor helped to prevent carbon formation, but it might have resulted in the sintering of the active metal. A long-time experiment proved the stability of the catalyst up to 49 h of time on stream (TOS) with a minor decrease in methane conversion from 84% to 78%.

Methane Catalytic Combustion under Lean Conditions over Pristine and Ir-Loaded La1-xSrxMnO3 Perovskites: Efficiency, Hysteresis, and Time-on-Stream and Thermal Aging Stabilities.

The increasing use of natural gas as an efficient, reliable, affordable, and cleaner energy source, compared with other fossil fuels, has brought the catalytic CH4 complete oxidation reaction into the spotlight as a simple and economic way to control the amount of unconverted methane escaping into the atmosphere. CH4 emissions are a major contributor to the 'greenhouse effect', and therefore, they need to be effectively reduced. Catalytic CH4 oxidation is a promising method that can be used for this purpose. Detailed studies of the activity, oxidative thermal aging, and the time-on-stream (TOS) stability of pristine La1-xSrxMnO3 perovskites (LSXM; X = % substitution of La with Sr = 0, 30, 50 and 70%) and iridium-loaded Ir/La1-xSrxMnO3 (Ir/LSXM) perovskite catalysts were conducted in a temperature range of 400-970 °C to achieve complete methane oxidation under excess oxygen (lean) conditions. The effect of X on the properties of the perovskites, and thus, their catalytic performance during heating/cooling cycles, was studied using samples that were subjected to various pretreatment conditions in order to gain an in-depth understanding of the structure-activity/stability correlations. Large (up to ca. 300 °C in terms of T50) inverted volcano-type differences in catalytic activity were found as a function of X, with the most active catalysts being those where X = 0%, and the least active were those where X = 50%. Inverse hysteresis phenomena (steady-state rate multiplicities) were revealed in heating/cooling cycles under reaction conditions, the occurrence of which was found to depend strongly on the employed catalyst pre-treatment (pre-reduction or pre-oxidation), while their shape and the loop amplitude were found to depend on X and the presence of Ir. All findings were consistently interpreted, which involved a two-term mechanistic model that utilized the synergy of Eley-Rideal and Mars-van Krevelen kinetics.

Iron-promoted zirconia-alumina supported Ni catalyst for highly efficient and cost-effective hydrogen production via dry reforming of methane

Developing cost-effective and high-performance catalyst systems for dry reforming of methane (DRM) is crucial for producing hydrogen (H2) sustainably. Herein, we investigate using iron (Fe) as a promoter and major alumina support in Ni-based catalysts to improve their DRM performance. The addition of iron as a promotor was found to add reducible iron species along with reducible NiO species, enhance the basicity and induce the deposition of oxidizable carbon. By incorporating 1 wt.% Fe into a 5Ni/10ZrAl catalyst, a higher CO2 interaction and formation of reducible "NiO-species having strong interaction with support" was observed, which led to an ∼80% H2 yield in 420 min of Time on Stream (TOS). Further increasing the Fe content to 2wt% led to the formation of additional reducible iron oxide species and a noticeable rise in H2 yield up to 84%. Despite the severe weight loss on Fe-promoted catalysts, high H2 yield was maintained due to the proper balance between the rate of CH4 decomposition and the rate of carbon deposit diffusion. Finally, incorporating 3 wt.% Fe into the 5Ni/10ZrAl catalyst resulted in the highest CO2 interaction, wide presence of reducible NiO-species, minimum graphitic deposit and an 87% H2 yield. Our findings suggest that iron-promoted zirconia-alumina-supported Ni catalysts can be a cheap and excellent catalytic system for H2 production via DRM.

Dry reforming of methane over supported Rh and Ru catalysts: Effect of the support (Al2O3, TiO2, ZrO2, YSZ) on the activity and reaction pathway

The effect of Al2O3, TiO2, ZrO2 and Yttria-Stabilized Zirconia (YSZ) supports on the activity of the dry reforming of CH4 towards syngas production was investigated for Rh and Ru catalysts. Ruthenium-based catalysts were found to generally be more active than Rh leading H2/CO ratios close to unity above 700 °C. Methane conversion turnover frequency (TOF) over Rh catalysts becomes optimum for Rh/YSZ followed by Rh/TiO2 and Rh/ZrO2, and finally Rh/Al2O3, which exhibited the lowest activity. The performance order is different for Ru catalysts, with TOF being increased in the order Ru/Al2O3<Ru/TiO2<Ru/YSZ < Ru/ZrO2. Time-on-stream (TOS) stability tests showed that Rh/ZrO2 is stable for 30 h, whereas Ru/ZrO2 exhibits a slight decrease of both reactants’ conversions. DRIFTS studies indicated that the reaction proceeds via a bifunctional mechanism involving both the metal and the support in the reaction pathway. The population and adsorption sites of produced carbonyls are strongly influenced by the metal-support combination determining the catalytic activity.

Controlling the reaction network of Ni/silica derived conversion of bio-oil surrogate guaiacol

Replacing fossil carbon sources with green bio-oils is a promising route to switch to a sustainable chemical industry, although their high oxygen contents are challenging. Catalytic hydrodeoxygenation is a favored route to upgrade bio-oils to renewable fuels and basic chemicals. In this work, we investigated Ni/SiO2 catalysts with differing metal dispersity in continuous mode conversion of guaiacol with a statistical experimental design for 250 °C to 400 °C, 2 h up to 5 h time on stream (ToS) and subsequently different residence time besides other parameters. While low temperature (250 °C) promotes cyclohexanol formation from guaiacol, high temperature (400 °C) inhibits hydrogenation, leading to phenol and methane. For medium temperature (340 °C), the selectivity for cyclohexanone increases. Cyclohexanol and cyclohexanone (KA-oil) are the industrial basis for polyamide 6. Furthermore, we clarified the role of 2-methoxycyclohexanol (2MC) in the reaction network towards KA-oil for continuous-mode operation. Statistical analysis was used to predict and optimize product selectivity and yield, leading to the best yield of cyclohexanone/-ol at 327.5 °C, low ToS, medium residence time, high particle dispersity, and medium hydrogen pressure (15 bar(g)).

Single‐step conversion of levulinic acid to valeric acid over bimetallic Ni‐Co/H‐ZSM‐5 catalysts

AbstractSingle‐step conversion of levulinic acid (LA) to valeric biofuel is extremely promising for the development of bio‐refineries. Direct conversion of LA to valeric acid (VA) was investigated over H‐ZSM‐5 supported Ni, Co, and Ni−Co (different Ni/Co wt. % ratios) catalysts under ambient reaction conditions (543 K and atmospheric pressure) in the gas phase. Compared with supported monometallic catalysts, bimetallic Ni−Co catalysts exhibited more activity and selectivity toward VA production. Among Ni−Co/H‐ZSM‐5 catalysts, 15Ni‐5Co/H‐ZSM‐5 catalyst is optimum with 97.5 % conversion of LA and 63 % selectivity to valeric acid even after 6 h time‐on‐stream (TOS). The active metallic sites are responsible for the hydrogenation of LA to γ‐valerolactone (GVL), and acidic sites catalyze the conversion of GVL to VA. All the catalysts were characterized using the XRD, H2‐TPR, N2‐adsorption‐desorption isotherms, NH3‐TPD, Py‐IR, SEM, HR‐TEM and XPS techniques.

Direct hydrogenation of CO2 into valuable aromatics over K/Fe-Cu-Al @HZSM-5 tandem catalysts: Effects of zeolite surface acidity on aromatics formation

Direct hydrogenation of carbon dioxide (CO2) to value-added aromatics can not only provide a sustainable aromatics synthesis route but also realize CO2 mitigation. However, it remains a great challenge to identify the optimal surface acidity and regulate the selective formation of aromatics during CO2 hydrogenation. Herein, we designed and prepared a series of K/Fe-Cu-Al@HZSM-5 tandem catalysts, and deeply investigated the effects of zeolite surface acidity on the catalytic performance, by changing the SiO2/Al2O3 ratios of HZSM-5 from 25 to 400. It was found that the surface acidity, especially for the Brønsted acidity, plays a crucial role in the aromatics formation. With an increasing Brønsted acidity from 0 to 290 μmol/g, the CO2 conversion keeps relatively stable (around 44%), however, the aromatics yield monotonously increases from 0.9 to 12.8%, indicating a distinct correlation with the Brønsted acidity. Among the obtained aromatics, the majority ones are C6–8 light aromatics, accounting for c.a. 30–60% within time on stream (TOS) of 24 h, but their proportion tends to gradually decrease with TOS, probably due to the catalyst deactivation by coking. Moreover, the possible reaction pathways for aromatics formation over the prepared K/Fe-Cu-Al@HZSM-5 tandem catalysts were also proposed.

Production of 2-methyl furan, a promising 2nd generation biofuel, by the vapor phase hydrodeoxygenation of biomass-derived furfural over TiO2 supported Cu[sbnd]Ni bimetallic catalysts

This work investigates the vapor phase hydrodeoxygenation (HDO) of FFR to 2-MeF over a series of TiO2-supported mono and bimetallic Cu-Ni catalysts with a fixed Cu content (10 wt%) and varying Ni content (0–20 wt%). The catalysts were synthesized through a simple wet impregnation method, and their properties were studied in depth through an array of analytical techniques such as X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), Scanning Electron Microscopy (SEM), N2-physisorption, Raman spectroscopy, and NH3-temperature programmed desorption (TPD). The catalyst characterizations revealed that the addition of Ni in progressively larger amounts resulted in greater dispersion of Cu species and an increase in the surface area & porosity of the bimetallic catalysts, arising from the strong interactions between NiO and CuO species. Detailed studies were carried out to evaluate the effect of various process parameters such as Ni content, temperature, and contact time on the selectivity of 2-MeF. Ni content of the bimetallic catalysts and temperature played a significant role in product distribution than the contact time. The bimetallic catalyst with the composition 10%Cu-10%Ni was observed to be the optimum, providing a FFR conversion of 100%, and a 2-MeF selectivity of 84.5% at 200 °C, H2/FFR molar ratio = 15, and WHSV = 0.87 gFFR h−1 gcatalayst−1 after 6 h time-on-stream (TOS). During the long-term catalytic activity evaluation, the catalyst exhibited a stable 100% FFR conversion and ∼ 85% selectivity towards 2-MeF over a period of 12 h. Even after a period of 15 h, conversion and selectivity values remained >90% and 70%, respectively.

Synergistic effect of transition metals substitution on the catalytic activity of LaNi0.5M0.5O3 (M = Co, Cu, and Fe) perovskite catalyst for steam reforming of simulated bio-oil for green hydrogen production

Hydrogen is considered an excellent source of renewable and sustainable energy which can be produced from inexpensive starting materials such as biomass. The present study aims at developing a stable catalytic system for bio-oil steam reforming process to produce green hydrogen. The perovskite catalysts LaNi0.5M0.5O3 (M = Co, Cu, and Fe) were synthesized using sol-gel method and their catalytic performance towards hydrogen production and bio-oil conversion was evaluated in a fixed bed tubular reactor. A wide array of techniques such as XRD, BET, NH3 and CO2 -TPD, FE-SEM, XPS, TGA and pyridine-FTIR were used to analyze the material properties of the synthesized catalysts. The results of these analyses verified the successful formation of the highly sought-after perovskite structure with good amount of surface oxygen vacancies as well as medium-strength acidic and basic sites. To establish an efficient catalytic system, process parameter (space-time and reaction temperature) optimization and time on stream (TOS) studies were conducted. The TOS results displayed that LaNi0.5Co0.5O3 perovskite catalyst is stable up to 12 h at 700 °C for space-time of 17.4 kgcat. h/kgmolbio-oil. In-depth characterizations (FE-SEM, TGA, RAMAN spectroscopy and XRD) of spent catalyst after the reaction not only gave further insights about the excellent activity exhibited by the chosen catalyst but also revealed information about the nature of the coke deposited on the surface.

Improving the Coke Resistance of Ni-Ceria Catalysts for Partial Oxidation of Methane to Syngas: Experimental and Computational Study.

The synthesis of syngas (H2 : CO=2) via catalytic partial oxidation of methane (CPOM) is studied over noble metal doped Ni-CeO2 bimetallic catalysts for CPOM reaction. The catalysts were synthesized via a controlled deposition approach and were characterized using XRD, BET-surface area analysis, H2 -TPR, TEM, Raman and TGA analysis. The catalysts were experimentally and computationally studied for their activity, selectivity, and long-term stability. Although the pure 5Ni/CeO2 catalyst showed high initial activity (∼90%) of CH4 conversion, it rapidly deactivates around 20% of its initial activity within 140 hours of TOS. Doping of Ni/CeO2 catalyst with noble metal was found to be coke resistant with the best-performing Ni-Pt/CeO2 catalyst showed ∼95% methane conversion with >90% selectivity at a temperature of 800 °C, having exceptional stability for about 300 hours of time-on-stream (TOS). DFT studies were performed to calculate the activation barrier for the C-H activation of methane over the Ni, Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces showed nearly equal activation energy over all the studied surfaces. DFT studies showed high coke formation tendency of the pure Ni (111) having a very small C-C coupling activation barrier (14.2 kJ/mol). In contrast, the Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces show appreciably higher C-C coupling activation barrier (∼70 kJ/mol) and hence are more resistant against coke formation as observed in the experiments. The combined experimental and DFT study showed Ni-Pt/CeO2 as a promising CPOM catalyst for producing syngas with high conversion, selectivity and long-term stability suited for future industrial applications.

Effect of precipitating agents on activity of co-precipitated Cu–MgO catalysts towards selective furfural hydrogenation and cyclohexanol dehydrogenation reactions

The major industrial application and study of hydrogenation of furfural-to-furfural alcohol and dehydrogenation of cyclohexanol to cyclohexanone, over different precipitating agents namely K2CO3, Na2CO3, KOH, NH3 and (COOH)2.2H2O was carried out in vapour phase reactor. Efforts were made to study the effect of these different precipitating agents on Cu–MgO catalyst and its activity towards the hydrogenation and dehydrogenation reactions due to its industrial applications. The prepared co-precipitated Cu–MgO catalysts were characterized by using various modern analytical and spectroscopic techniques which include FE-SEM, BET, XRD, XPS, TPR and DTA. The characterization data revealed that different precipitating agents strongly influenced the physiochemical properties of the developed heterogeneous catalysts. Additionally, FE-SEM images revealed that employing different precipitating agents resulted in various morphologies for the final catalysts. The hydrogenation and dehydrogenation reactions over the Cu–MgO catalyst revealed that the catalyst prepared by K2CO3 as precipitating agent exhibited high catalytic activity. Meanwhile, The presence of more Cuo/Cu+ species on this catalyst with smaller Cu crystallite size as evidenced by XPS and XRD results seems to be accountable for its high activity towards the formation of furfural alcohol and cyclohexanone compared to the other catalysts with different precipitating agents. Additionally, the time on stream (T.O.S) studies performed and it revealed that the catalyst was fairly stable for 300 min showing consistency in its activity towards both reactions. The yield obtained for furfural alcohol and cyclohexanone was 97% and 64%, respectively.

Fuzzy modeling system based on GA fuzzy rule extraction and hybrid of differential evolution and Tabu search approaches: Application in synthesis gas conversion to valuable hydrocarbons process

In the present study, a fuzzy approach is employed in order to develop a model for the conversion of synthesis gas to valuable hydrocarbon process. The fuzzy rules are extracted by clustering technique in this study. The numbers of fuzzy sets for input and output variables are optimized by genetic algorithm (GA) so that the number of data which follows the inconsistent rules, is minimized. Firstly, the center values of clusters are estimated by a proposed logarithmic distance method and the clusters and their centers are then calculated by k-means method. The prediction of CO conversion and olefin and paraffin selectivities is performed based on five input variables: H2/CO content, Time on Stream (TOS), temperature, Weight Hourly Space Velocity (WHSV) and phosphorous content by the proposed fuzzy model so that the parameters of which are optimized by combination of Differential Elevation and Tabu Search optimization approaches (DETS). The comparison of the performance of the designed approaches with two other models (i.e. fuzzy and GA fuzzy models) is executed and the results clearly demonstrate that the developed DETS- GA clustering fuzzy model can be defined as a powerful tool in modeling of the conversion of synthesis gas to hydrocarbons process with regression analysis (R2) of over 96%.

Intensifying gasoline production in the hydrocracking of pre-hydrotreated light cycle oil by means of Pt and Pd supported on a spent FCC catalyst

Motivated by the necessity of intensifying the valorization of secondary refinery streams and of extending the life cycle of the catalysts, this study aims to obtain high quality gasoline in the hydrocracking of a pre-hydrotreated light cycle oil (HT-LCO) using noble metals catalysts supported on a spent fluid catalytic cracking (FCC) catalyst. Hydrocracking runs have been carried out in a fixed bed reactor with two different catalysts (Pt/FCC and Pd/FCC) under the following conditions: 320–400 °C; 80 bar; hydrogen to HT-LCO ratio, 1000 NmL mL−1; weight hourly space velocity (WHSV), 4.48 h−1; and time on stream (TOS), 8 h. The results have exposed that 400 °C is the optimal temperature for hydrocracking the HT-LCO, since the yield of gasoline is clearly maximized (yielding up to 80 wt%) at the same time that the formation of gases is minimized. Comparing both catalysts, the Pt/FCC catalyst has offered better performance as its high hydrogenation capacity has allowed for obtaining an isoparaffinic gasoline fraction with a RON of 93.0. These good results lay on two facts that avoid the blocking of the micropores of the zeolite HY by the deposition of coke: (i) the hydrocracking of the coke precursors; and (ii) the matrix of the FCC catalyst where a fraction of the coke is deposited. In this way, after an initial deactivation period, the catalysts have reached a pseudo-stable state with a notorious remaining catalytic activity (higher for the Pt/FCC catalyst).

Combustion synthesis of lanthanum oxide supported Cu, Ni, and CuNi nanoparticles for CO2 conversion reaction

The reverse water gas shift (RWGS) process is considered a feasible method for lowering greenhouse gas emissions by utilizing CO2 and converting it to CO. Herein, we evaluated the catalytic conversion of CO2 through the RWGS reaction over transition metal nanoparticles supported on lanthanum. Catalysts of selected active metals (Cu, Ni, and CuNi) on lanthanum oxide support were investigated in a packed bed tubular reactor within a temperature range of 100–600 °C to assess their catalytic activity and selectivity towards CO. The results of the catalyst's activity and stability experiments showed maximum CO2 conversions of 57%, 68% and 74% for Cu–La2O3, Ni–La2O3, and CuNi–La2O3, respectively, at 600 °C and excellent stability over a 1440-min time on stream (TOS) with a carbon deposition rate of less than 3 wt%. However, among all investigated catalysts, only the 1 wt% Cu–La2O3 catalyst displayed a CO selectivity of 100% at all the studied temperatures, whereas the nickel-containing catalysts showed selectivity for methane along with carbon monoxide. Furthermore, the morphological properties of the support and catalysts, as well as the effect of the reaction conditions on the catalysts surface, were studied using a variety of techniques, including XRD, TEM, SEM-EDX and TPR. The results showed promising potential for the application of transition metal catalysts on lanthanum oxide support for RWGS that could be extended to other hydrogenation reactions.

Steam reforming of bio-alcohols over Ni-M (Cu, Co, Pt)/MCF-S (MgO, La2O3, CeO2) for renewable and selective hydrogen production: Synergistic effect of MCF silica and basic oxides on activity and stability profiles

In the current investigation, highly active, and stable catalyst-support systems were developed by employing the benefits of the 3D mesoporous arrangement of MCF silica and O2− Lewis basic sites of MgO, La2O3, and CeO2 in a single system for renewable and selective H2 production via steam reforming (SR) of bio-alcohols, viz., ethanol (SRE), glycerol (SRG), n-butanol (SRB), and ethylene glycol (SREG). The impact of aging time [24, 48, and 72 h ] on structural and surface features of MCF silica was also investigated to develop novel type of mesoporous materials with the best textural properties, viz., Cu-Ni-Co/MCF-MgO for SRE, Ni-Cu/MCF-La2O3 for SRG, Pt-Ni-Cu/MCF-La2O3 for SRB and Ni-Cu/MCF-CeO2 for SREG which were characterized by several physio-chemical techniques; for instance, BET, H2-TPD, H2-TPR, TGA, XRD, TEM, SEM, EDX as well as high-resolution XPS analysis. The efficacy of the combination of MCF silica with basic metal oxides was evident from the results showing nearly complete reactant conversion, no coke formation, high selectivity (>84 % H2 yield), and long-term stability beyond 680 h (> 68 h time on stream (TOS) for one cycle over > 10 cycles) for all bio-alcohols whereas MCF silica without any basic metal oxides, i.e. Ni-Cu/MCF was stable only up to ≤ 64 h (≤ 16 h TOS for one cycle up to ≤ 4 cycles) due to the absence of O2− Lewis basic sites leading to coking. Such a huge difference in catalytic stability between MCF-S (MgO, La2O3, CeO2) and Ni-Cu/MCF catalysts clearly justifies the synergistic effect of the 3D mesoporous structure of MCF silica and O2− Lewis basic sites on high metal dispersion, strong metal-support interaction (SMSI), coke inhibition. It proved their efficacy as potential commercial SR catalysts for sustainable H2 production from bio-alcohols. Finally, catalytic reaction mechanisms were developed for SRE, SRG, SRB, SREG and intrinsic reaction kinetics were studied over their corresponding catalyst-support systems in the absence of external mass transfer and intra-particle diffusion resistancs. The apparent activation energies for SRE, SRG, SRB, and SREG were calculated as 7.2, 11.2, 10.5, and 12.1 kcal/mol, respectively.

Catalytic hydroprocessing of waste cooking oil for the production of drop-in aviation fuel and optimization for improving jet biofuel quality in a fixed bed reactor

Waste cooking oil (WCO) is a bio-waste with significant potential for developing improved transportation fuel, specifically for the aviation industry. This work investigates the catalytic hydrocracking of WCO over commercial hydrocracking catalyst (Ni-Mo/silica-alumina) in a continuous flow fixed bed reactor to produce jet range hydrocarbons (HCs). The aim was to convert WCO into sustainable aviation and automotive fuel to get the maximum benefit from waste oil with high selectivity towards paraffins, naphthenes, minimal aromatics, and high isomerization (isomer to normal (i/n) ratio) in a single-step process using a single catalyst composition. The higher i/n ratio boosts specific energy, thermal stability and provides a low freezing point to the fuel. The results show that WCO conversion of 96.6 % with 55.6 % selectivity of jet range HCs was obtained at 420 °C temperature, 1 h−1 LHSV, 10 MPa pressure, and 2200 NLgas/Lliquid H2/oil ratio. In addition, isomer yield of 82.9 %, i/n ratio of 4.8, and selectivity of kerosene range HCs based on paraffins (43.6 %), naphthenes (8.2 %), and aromatics (3.73 %) was obtained at optimum reaction conditions. After hydroprocessing, the major fraction of heteroatoms (N = 99.9 %, S = 94.3 %, O = 99.9 %) was removed from WCO. Finally, the time on stream (TOS) study showed no deactivation of the catalyst up to 590 h, indicating the long life and stability of the catalyst, which is one of the highest lifetimes reported so far. Bio-jet fuel properties were tested according to the ASTM D-1655 standard. This research will aid in developing novel catalysts for the selective conversion of WCO into jet range HCs in a single step process.

Partial oxidation of methane over high coke-resistant bimetallic Pt-Ni/CeO2 catalyst: Profound influence of Pt addition on stability

We have developed a bimetallic Pt-Ni/CeO2 catalyst by straightforward citric acid complex combustion method for low-temperature partial oxidation of methane. Furthermore, we also compared the catalytic performance of bimetallic Pt-Ni/CeO2 with monometallic Ni/CeO2 catalysts. The bimetallic 0.5%Pt-2.5%Ni/CeO2 (PNC2.5) catalyst exhibited >99% conversion of methane with a H2/CO ratio of 2, whereas monometallic 2.5%Ni/CeO2 (NC2.5) catalyst showed ∼92% methane conversion with a H2/CO ratio of 1.9 at 700 °C. In addition, the PNC2.5 catalyst does not show any deactivation and structural changes during 500 h time-on-stream (TOS), also confirmed by TEM, Raman, and TGA analysis. Conversely, a substantial activity loss (∼61%) was noticed in the NC2.5 catalyst owing to the coking and sintering of Ni species. The excellent performance of the PNC2.5 catalyst can be attributed to the modified electronic-structural properties. The activation of CH4 molecules was studied by DFT calculation over Pt-Ni/CeO2(111) and Ni/CeO2(111) model systems, which explain the promotional effect of Pt in the methane C-H bond activation with ∼8 kcal/mol reduction in the activation barrier.

Boron-promoted Ni/MgO catalysts for enhanced activity and coke suppression during dry reforming of methane

The dry reforming of methane (DRM) provides an attractive solution for the utilization of CH4 and CO2 and its performance highly depends on the catalyst. In this study, DRM to syngas was studied using a series of Ni/MgO catalysts modified by B2O3 (0.1–2.0 wt%). The results demonstrated that introducing only 0.25 wt% B2O3 to 4Ni/MgO catalyst significantly improved its activity, stability, and carbon resistance. After 40 h time on stream (TOS), the activity of 4Ni0.25B/MgO catalyst almost unchanged and was approximately 20% higher than that of the unmodified 4Ni/MgO catalyst. The 4Ni0.25B/MgO catalyst also showed the least carbon deposits (0.3 wt%) among all samples. The characterization tests suggest that B2O3 substantially enhanced the Ni reducibility during DRM without weakening the Ni–MgO interaction, thereby improving the activity without sacrificing the dispersion and stability of the Ni nanoparticles (NPs). Intermetallic nickel boride was formed when B2O3 interacted with metallic Ni, which suppressed the formation of filamentous and graphitic carbon. In addition, excess B2O3 has a slight influence on the formation of amorphous carbon.