Time On Stream Research Articles

CrMn‐based catalysts for oxidative dehydrogenation of propane to propylene with CO2

AbstractThe paper investigates the catalytic oxidative dehydrogenation of propane with carbon dioxide (ODH‐CO2) as a promising route for propylene production, an avenue yet to be commercially developed. Utilizing the incipient wetness catalyst preparation method, CrMn catalysts were synthesized on three supports (γ‐Al2O3, ZSM‐5, and SBA‐15). Comprehensive characterization through Brunauer–Emmett–Teller (BET) analysis, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM)/scanning transmission electron microscopy (STEM)‐energy‐dispersive X‐ray spectroscopy (EDS), and hydrogen temperature programmed reduction (H2‐TPR) was conducted to comprehend catalyst behaviour. Among the six catalysts tested, Cr/SBA‐15 was exhibited as the best performer, achieving propane and CO2 conversions of 36.2% and 14.1%, respectively, with a propylene selectivity of 33.4%. Over a 50‐h time on stream (TOS), it demonstrated gradual declines in conversions while retaining 75% of initial values. The incorporation of manganese as a promoter effectively mitigated coke formation, albeit with slight reductions in propane conversion and propylene selectivity.

Hierarchically structured nanospherical fibrous silica-supported bimetallic catalysts: An enhanced performance in methane decomposition

Hydrogen production by methane catalytic decomposition is a promising method that also allows the formation of valuable carbon nanomaterials which can be utilized in transportation fuels, chemical synthesis, and fuel cell technology. In this study, bimetallic 3d transition metal (Ni, Fe, Co) catalysts supported on spherical mesoporous nanofibrous silica (KCC1) were successfully synthesized using a hydrothermal method followed by sono co-impregnation. The catalysts were evaluated for their performance in the catalytic decomposition of methane. Comprehensive characterization of the catalysts was conducted utilizing XRD, FTIR, SEM, TEM, STEM, XPS, H2-TPR, and BET techniques. XRD and TEM analyses confirmed the formation of Ni–Fe, Ni–Co, and Co–Fe bimetallic alloys on the nanofibrous silica without compromising its dendrimeric hierarchical structure. STEM HAADF imaging revealed a uniform dispersion of bimetallic nanoparticles within the spherical fibrous framework. Catalytic tests demonstrated that all bimetallic catalysts showed high stability and activity for methane cracking at 700 °C over 180 min of time on stream (TOS). Among them, Fe-based catalysts Ni–Fe/KCC1 and Co–Fe/KCC1 achieved the highest hydrogen yields of 80% and 60%, respectively. Methane conversion was 1.56 and 2.23 times higher in Ni–Fe/KCC1 compared to Co–Fe/KCC1 and Ni–Co/KCC1, respectively. Post-reaction characterization of the spent catalysts was performed using XRD, Raman spectroscopy, SEM, TEM, and TGA. XRD and Raman spectroscopy were used to evaluate the degree of graphitization and crystallinity in the carbon nanotubes (CNTs) produced on the catalysts, enabling a correlation with the catalyst properties. TEM examination was used to investigate the structural morphology and growth methods of the CNTs, including tip or base growth and chain-like or parallel-wall types. TGA results revealed that all bimetallic catalysts exhibited no amorphous carbon during methane cracking reaction.

Electrolysis of CuCl/HCl aqueous system in Cu–Cl thermochemical cycle for green hydrogen production: Investigations on alternative to platinum anode

The ICT-OEC Cu–Cl cycle is a six-step thermochemical copper-chlorine (Cu–Cl) closed-loop cycle to produce green hydrogen via water splitting. One of the critical steps in this cycle involves the electrolysis of CuCl to generate copper (Cu) and cupric chloride (CuCl2). Using platinum as the anode material in this system is economically disadvantageous and expensive. Consequently, this work investigates the feasibility of alternative anode materials to replace platinum. Mixed Metal Oxide (MMO) coated on Ti mesh (MMO mesh) and Pt coated on Ti mesh (Pt mesh) were evaluated as suitable anode alternatives to pure Pt sheet based on their performance metrics at different voltages. The integration of MMO mesh for a 100-h Time on Stream (TOS) study at a mini-pilot scale demonstrated promising current density and efficiency values. However, performance variations were observed over prolonged operation, potentially due to changes in membrane resistance. After 100 h, the MMO mesh remained undamaged, indicating its durability for extended use. Characterization studies revealed the electrodeposited copper to have a dendritic structure with an FCC phase. The findings suggest that MMO mesh and Pt mesh are viable alternatives to platinum at operating voltages above 0.7 V in this system.

Response surface optimization of hydrogen-rich syngas production by methane dry reforming over bimetallic Mn-Ni/La2O3 catalyst in a fixed bed reactor

The present work utilizes a response surface optimization technique to optimize hydrogen-rich syngas production through the process of methane dry reforming (DRM). This optimization is achieved by employing a bimetallic Mn–Ni/La2O3 catalyst. The study aimed to evaluate the impact of three key parameters, namely reaction temperature, time on stream (TOS), and gas hourly space velocity (GHSV), on the hydrogen to carbon monoxide (H2/CO) ratio in syngas during the DRM. The Mn–Ni/La2O3 catalyst, synthesized using the sequential wet impregnation technique, exhibited suitable physicochemical properties necessary for DRM reaction, as evidenced by the obtained characterization data. Among the five models examined, it was found that the quadratic versus 2FI model substantially fit the experimental data, as evidenced by a p-value <0.05. The analysis of variance (ANOVA) conducted on the quadratic response surface model compared to the 2FI model demonstrated that both the reaction temperature and the TOS had a significant impact on the H2/CO ratio in the syngas. The only significant interaction factor was the relationship between the reaction temperature and the TOS. Under the specified optimal circumstances of 15 000 ml/g.h, 850 °C, and 258.15 min, an H2/CO ratio of 0.98 was achieved. The resulting H2/CO ratio of 0.98 is almost 1, indicating its suitability as a feedstock for methanol production in the Fischer-Tropsch synthesis (FTS).

The Oscillatory Behaviour of Cu-ZSM-5 Catalysts for N2O Decomposition: Investigation of Cu Species by Complementary Techniques.

Copper-exchanged ZSM-5 (Cu-ZSM-5) is a promising catalyst thanks to the Cu redox pair. A particular feature of this material consists in the presence of spontaneous isothermal oscillations which take place during N2O decomposition reaction, depending on the operating conditions. In the present work, a set of five Cu-ZSM-5 catalysts was synthesised by three procedures and three different copper precursor concentrations: i) wet impregnation, ii) single ion exchange, and iii) double ion exchange. Catalytic tests revealed that the ion-exchanged samples exhibit a low catalytic activity and no oscillatory behaviour, except for the twice-exchanged sample which achieves an average N2O conversion of 26 % at 400 °C. Conversely, the impregnated samples reach higher levels of N2O conversion (66 % for Cu5ZSM5_WI and 72 % for Cu10ZSM5_WI) and demonstrate a similar oscillating pattern. Further investigations disclosed that the most active catalysts, characterised by the presence of oscillatory behaviour, have more abundant and easily reducible copper species (ICP, EDX and H2-TPR) which interact better with the zeolitic support (FT-IR). Catalytic tests under a long time on stream (TOS) suggest that either self-organised patterns or deterministic chaos can be achieved during the reaction, depending on the operating conditions, such as temperature and contact time.

Tuning of the acid sites in the zeolite-alumina composite Ni catalysts and their impact on the palm oil hydrodeoxygenation reaction

The hydrodeoxygenation (HDO) of bio-oil is one of the potential approaches to produce green diesel. However, HDO catalyst requires the development of bifunctionality which translates to the simultaneous presence of acidic and metal sites for desired catalytic activity and selectivity. Zeolites and their composites are attractive candidates for the conversion of biomass to fuels. In the present work, a series of Ni-incorporated Al2O3-zeolite beta bifunctional composite catalysts with distinct Al2O3 (25–75 wt%) and Ni contents (5–15 wt%) were synthesized via a facile one-pot method directly from nickel acetate, nano-boehmite (γ-AlO(OH)) and the NH4+ form of beta zeolite (NH4+-BZ). The nano-boehmite particles, due to the positive charges on their surface, electrostatically attract negatively charged beta zeolite crystals, which leads to the assembly of a hierarchical pore structure upon calcination. Interestingly, the composite catalysts synthesized were quite homogeneous with uniform dispersion of Ni particles. All composite catalysts were thoroughly characterized using XRD, SEM-EDX, SEM-mapping, HR-TEM, H2-TPR, H2-TPD, NH3-TPD, XPS, 31P MAS NMR, 27Al MAS NMR and N2 sorption analysis. The synthesized composite catalysts with distinct Al2O3 contents showed diverse textural properties, distinct nature of acid sites and improved performance in hydrodeoxygenation of palm oil. Particularly, the Ni/BZ-Al50 (with BZ:Al2O3 = 50:50) composite catalyst significantly enhanced the conversion of palm oil (up to 90%) and yield of n-C15-C18 hydrocarbons (up to 69%) at moderate temperature of 375 °C as compared to 10Ni/BZ catalyst (Conv. = 75%, yield of n-C15-C18 = 52%). The higher catalytic performance realized with composite catalysts can be ascribed to its hierarchical pore structure, moderate acidity (chemisorption studies), tuned acid sites nature (solid state NMR) and homogeneous distribution of active Ni sites (H2 chemisorption) which helps to improve product selectivity by minimizing side reactions. The time-on-stream (TOS) experiments were carried out up to 20 h which clearly showed that composite catalysts are more stable suggesting the lower amount of coke deposition (TPO studies) and suppression of metal sintering.

Selective Hydrogenation of Diethyl Malonate to 1,3-Propanediol Over Ga-Promoted Cu/SiO2 Catalysts With Enhanced Activity and Stability.

Cu catalysts with different compositions and different Cu and promoter contents were prepared by precipitation-gel method and studied for the selective hydrogenation of syngas or biomass-based diethyl malonate (DEM) to valuable 1,3-propanediol (1,3-PDO). The Ga-promoted 70Cu6Ga/SiO2 catalyst was found to exhibit the highest catalytic performance, achieving 100 % DEM conversion and 76.6 % 1,3-PDO selectivity under reaction conditions of 160 °C and 8 MPa H2. The 70Cu6Ga/SiO2 bimetallic catalyst also presented obviously better stability than that of the monometallic 70Cu/SiO2 catalyst in a continuous flow reactor over 180 h time-on stream. Characterization results showed that the incorporation of Ga increased the interaction between Cu and Ga species, hindered the full reduction of Cu2+ species, and thus increased the proportion of Cu+ and the number of Lewis acidic sites on the catalyst surface. The synergistic effect between Cu0 and Cu+ enhanced the adsorption and activation of ester carbonyl groups and their subsequent hydrogenation, eventually contributed to the outstanding performances of the CuGa/SiO2 bimetallic catalysts.

Long‐Term Stability of Ammonia Decomposition over Nickel‐Based Catalysts

Green hydrogen can be used as the backbone of a novel energy system and as a feedstock for renewable chemistry. H2 storage and transport are challenging, but ammonia as a hydrogen carrier could potentially solve these inefficiencies. Many studies focus on high catalytic activities, but the long‐term stability is often insufficiently investigated. This work reports on the stability of a nickel‐based reference catalyst and a coprecipitated Ni/Al2O3 catalyst over 800 h time on stream (TOS) in 98% NH3 at atmospheric pressure. An automated temperature control is necessary to adjust the temperature of the heat source to compensate for the changing heat demand resulting from catalyst activation or deactivation. Under reaction conditions the reference catalyst first undergo an activation phase before reaching its maximum conversion of 91.9% after 250 h TOS followed by a minor decrease in conversion. In comparison, the Ni/Al2O3 catalyst shows lower activity and undergo a continuous deactivation due to sintering. Overall, the activity loss at 534 °C amounted to only 1.5% for the reference catalyst and to 13.5% for the Ni/Al2O3 catalyst compared with the maximum conversion level. Thus, the Ni‐based reference catalyst proves to be very stable under industrially relevant NH3 decomposition conditions.

Enhanced Bio-BTX Formation by Catalytic Pyrolysis of Glycerol with In Situ Produced Toluene as the Cofeed.

The catalytic coconversion of glycerol and toluene (93/7 wt %) over a technical H-ZSM-5/Al2O3 (60-40 wt %) catalyst was studied, aiming for enhanced production of biobased benzene, toluene, and xylenes (bio-BTX). When using glycerol/toluene cofeed with a mass ratio of 93/7 wt %, a peak BTX carbon yield of 29.7 ± 1.1 C.% (at time on stream (TOS) of 1.5-2.5 h), and an overall BTX carbon yield of 28.7 C.% (during TOS of 8.5 h) were obtained, which are considerably higher than those (19.1 ± 0.4 C.% and 11.0 C.%) for glycerol alone. Synergetic effects when cofeeding toluene on the peak and overall BTX carbon yields were observed and quantified, showing a relative increase of 3.1% and 30.0% for the peak and overall BTX carbon yield (based on the feedstock). These findings indicate that the strategy of cofeeding in situ produced toluene for the conversion of glycerol to aromatics has potential to increase BTX yields. In addition, BTX production on the catalyst (based on the fresh catalyst during the first run for TOS of 8.5 h and without regeneration) is significantly improved to 0.547 ton ton-1catalyst (excluding the 76% of toluene product that is 0.595 ton ton-1catalyst for the recycle in the cofeed) for glycerol/toluene cofeed, which was 0.426 ton ton-1catalyst for glycerol alone. In particular, this self-sufficient toluene product recycling strategy is advantageous for the production and selectivity (relative increase of 84.4% and 43.5% during TOS of 8.5 h) of biobased xylenes.

Heavy oil atmospheric residue: HDS performance and life test using ARDS catalysts system

The objective of this study is to evaluate the catalyst by introducing atmospheric residue of heavy crude (H-AR) that secures full comprehensive characteristics and converts into a petroleum product, namely low sulfur fuel oil (LSFO). Furthermore, to estimate the catalyst’s lifespan under hydroprocessing conditions by monitoring its deactivation rate and maintaining consistent sulfur in LSFO products through gradual increases in reaction temperature. Prior to the hydrotreating test, the heavy crude oil underwent desalting, dewatering, and atmospheric distillation to obtained atmospheric residue (H-AR, i.e., 350°C+) for use as feedstock. The pilot plant employed a catalyst system comprising both hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts, distributed across two fixed-bed reactors. The results showed the lifespan approximately 3.0 months as a function of time-on-stream (TOS). The H-AR feed, with its high sulfur, metals, asphaltenes, and micro carbon residue (MCR) content, poses several challenges including carbon deposition at start of run (SOR). The observed deactivation rate is attributing to the feedstock’s poor quality and its impact associated deposition of coke and metals (V and Ni) deposition with TOS.

Efficient conversion of glycerol into 1,2-propanediol over Cu/SiO2 catalyst prepared through impregnation assisted with crown ether

Abstract A highly efficient and stable Cu/SiO2 catalyst was prepared via 12-crown-4-ether (12C4)-assisted impregnation and used in the vapor-phase conversion of glycerol to 1,2-propanediol (propylene glycol, PG) via acetol formation in an ambient hydrogen flow. The 12C4-Cu/SiO2 catalyst gave a PG yield of &amp;gt;97% due to a low rate of C–C cleavage to generate ethylene glycol. Under optimum conditions, the high catalytic performance was maintained for 98 h of time on stream.

Dry reforming of methane over Ni/fibrous Zeolite-Y: optimization and regeneration studies

This study optimized the catalytic performance of Ni/Fibrous Zeolite-Y (Ni/FHY) toward dry reforming of methane (DRM). The optimization study was conducted under three independent variables employing the response surface methodology (RSM), trailed by a regeneration and stability studies. The study focused on the independent parameters of reaction temperature (A) (700 °C–900 °C), gas hourly space velocity (GHSV) (B) (15,000 mL/gcat −1.h−1 – 35,000 mL/gcat −1.h−1), and CH4/CO2 ratio (C) (1.0–3.0). The catalyst exhibited excellent activity (CH4 conversion = 94.5%, CO2 conversion = 88.3%, and H2/CO = 1.05) when all the parameters were under these optimum conditions (A = 833 °C, B = 24,962 mL/gcat −1.h−1, and C = 2.08). The catalytic stability study revealed an excellent performance of Ni/FHY where there was no indication of catalyst deactivation up to 30 h of time-on-stream (TOS). The outcome of the excellent catalytic activity can be explained by Ni-metal inclusion that enabled a substantial increase in the interaction between FHY and Ni, hence, subdued carbon formation. The regeneration study showed a good performance of regeneration owing to the capability of air to regenerate the catalyst completely, thus resulting in an excellent performance with 90 h TOS.

Tailoring Cu/Hydroxyapatite Catalysts for Selective Hydrogenolysis of Biomass Derived Levulinic Acid to γ-Valerolactone Biofuel Additive

Background: Sustainable synthesis of γ-valerolactone (GVL) from levulinic acid (LA) offers a sustainable approach to converting biomass-derived feedstocks into valuable chemicals and fuel additves. Cu-Hydroxyapatite (Cu-HAp) catalysts are potential candidates for vapor-phase hydrogenation of LA to GVL due to their enhanced catalytic activity and selectivity through Cu nanoparticle support. Objective: This study aimed to investigate the catalytic performance of Cu-HAp catalysts in the hydrogenation of levulinic acid to γ-valerolactone. The primary goal was to optimize reaction conditions and assess the enhanced catalytic activity and selectivity Methods: The influence of copper loading, reaction temperature, and catalyst stability was evaluated. Moreover, the effect of time on stream (TOS) on LA conversion and GVL selectivity was examined by the best optimised Cu/HAp catalyst. Results: Cu-HAp catalysts exhibited favorable catalytic performance, with optimal conditions at approximately 5wt% copper loading. At this loading, maximum LA conversion (60%) and GVL selectivity (90%) were achieved after 8 hours on the stream at 265°C and 0.1 MPa conditions. Conclusion: The study demonstrates the efficacy of Cu-HAp catalysts for the hydrogenation of levulinic acid to γ-valerolactone. The findings indicate that as the copper loading increases from 2 to 20 wt%, the conversion of LA and the selectivity to GVL both decline. The analysis further implies that the dispersion of Cu species corresponds directly to the activity observed during the LA hydrogenation. The conversion of LA rises with a higher reaction temperature ranging from 250-320°C, although the selectivity of GVL decreases above 265°C. The catalyst's stability is crucial for maintaining efficient catalytic activity over time, with observed deactivation attributed to Cu metal particle aggregation and coke formation on active sites. The findings contribute to the development of robust catalyst systems for biomass-derived chemical transformations.

A Review of DME Manufacturing: Process and Catalyst Studies

Consumption of fossil-based energy is increasing every year which has an impact on air, water and soil pollution. Therefore, alternative energy is needed to replace fossil fuels. Dimethyl Ether (DME) is considered suitable to replace LPG because of its better physical and chemical properties than LPG. This review article discusses the differences between direct and indirect DME synthesis methods and studies their reaction mechanisms. In addition, the types of promoter addition and their effects on the characteristics and performance of the catalyst are also studied in this article. The final part of this article discusses the effect of operating conditions (temperature, pressure, time on stream (TOS), room velocity, and H2/CO ratio) on catalyst performance, which is sourced from several literatures. It is hoped that this article can obtain an effective DME manufacturing method both in terms of process and catalytic

Elucidating metal composition–coking relationships and coke formation pathways during gas-phase oxydehydration of glycerol over clay mineral-supported Mo-V-O catalysts

Catalyst deactivation by carbon deposition (coking) remains a major obstacle in many important industrial processes, such as catalytic gas-phase oxydehydration of glycerol. Understanding the chemical nature and development of coke species during the time-on-stream (TOS) of the catalytic solids is therefore crucial for mitigating the extent of coking and in the design of regeneration process of the coked catalysts. In this study, multiple analytical techniques, including SEM, XRD, FTIR, Raman, GC-MS, XPS, and 13C solid-state MAS NMR were employed to gain insights into the coking behavior of acid-activated montmorillonite (HMMT) supported Mo-V-O catalysts with modulated metal ratios, along with soluble and insoluble coke compositions and their evolution over time. Insoluble coke was comprised of polycyclic aromatic compounds with 5 or more fused-benzene rings containing different types of oxygen-bonded groups, such as −OCH3, −COOH, −CHO, and −OH. The major chemical constituents of soluble coke were mononuclear aromatic derivatives (i.e., xylenes, 2,4-di-tert-butylphenol, and 1-hydroxycyclohexyl phenyl ketone) and paraffinic hydrocarbons with 12–18 carbon atoms. The latter coke species is thought to be formed via the deoxygenation of linear oligoglycerols. The insights presented in this study may aid in understanding the carbon deposition process during gas-phase oxydehydration of glycerol for improved design of supported Mo-V-O catalyst materials with high coking resistance.

Aging studies of Dual functional materials for CO2 direct air capture with in situ methanation under simulated ambient conditions: Ru thrifting for cost reduction

Dual function materials (DFMs) comprised of 0.25 %Ru, 6.1 %Na2O/γ-Al2O3//monolith were evaluated for about 250 hours time-on-stream (TOS) at various simulated ambient climate capture conditions followed by temperature swing methanation to 280 °C. This paper focuses on the impact of thrifting Ru to low levels and the impact on performance. Results showed both stable CO2 capture capacity and CH4 production with 0.25 % Ru DFM deposited on a ceramic monolith. The CO2 conversion to CH4 production was decreased slightly by the Ru decrease from 1 % to 0.25 %. The capture capacity decreased since a lower Ru content reduces the complete decomposition of the Na2CO3 precursor producing fewer active adsorption sites (“Na2O”). The deployment of a low Ru DFM monolith would significantly decrease the overall capital cost and give more potential for a large-scale direct air capture and methanation (DACM) application.

Decoupling reaction network and designing robust VOx/Al2O3 catalyst with suitable site diversity for promoting CO2-mediated oxidative dehydrogenation of propane

Detailed thermodynamic analysis was utilized to decouple the complex reaction network of CO2-mediated oxidative dehydrogenation (CO2-ODH) of propane and unravel critical catalyst design requirements. Inspired by the unmatched ability of boron-based catalysts in limiting cracking and overoxidation reaction pathways, we exploited controlled integration of both VOx and BOx active phases onto a γ-Al2O3 support and constructed a highly efficient CO2-ODH catalyst via scalable mechanochemical synthesis route. The solvent- and template-free synthetic design strategy regulated crucial properties of the catalysts and endowed suitable site diversity as evidenced from N2-adsorption analysis, XRD, HRTEM, Raman analysis, NH3-TPD, H2-TPR, and UV–Vis diffuse reflectance spectroscopy. Consequently, excellent propane conversion and propylene yield of 61 and 34 % respectively over 12 h time on stream (TOS) at 650 °C were realized with a catalyst composed of 5 wt% vanadium and 7 wt% boron. In situ DRIFT measurement revealed insight into the dynamic changes on the catalyst surface and the corresponding evolution of reaction intermediates during the CO2-ODH process. Overall, the thermodynamic investigation re-emphasized the critical importance of effective kinetic control while the synthetic protocol illustrated a promising avenue for rational design of CO2-ODH catalysts to harness the unique advantages of boron and metal oxide-based catalysts simultaneously.

One-Step Conversion of n-Butanol to Aromatics-free Gasoline over the HZSM-5 Catalyst: Effect of Pressure, Catalyst Deactivation, and Fuel Properties as a Gasoline.

Sustainable production of gasoline-range hydrocarbon fuels from biomass is critical in evading the upgradation of combustion engine infrastructures. The present work focuses on the selective transformation of n-butanol to gasoline-range hydrocarbons free from aromatics in a single step. Conversion of n-butanol was carried out in a down-flow fixed-bed reactor with the capability to operate at high pressures using the HZSM-5 catalyst. The selective transformation of n-butanol was carried out for a wide range of temperatures (523-563 K), pressures (1-40 bar), and weight hourly space velocities (0.75-14.96 h-1) to obtain the optimum operating conditions for the maximum yields of gasoline range (C5-C12) hydrocarbons. A C5-C12 hydrocarbons selectivity of ∼80% was achieved, with ∼11% and 9% selectivity to C3-C4 paraffin and C3-C4 olefins, respectively, under optimum operating conditions of 543 K, 0.75 h-1, and 20 bar. The hydrocarbon (C5-C12) product mixture was free from aromatics and primarily olefinic in nature. The distribution of these C5-C12 hydrocarbons depends strongly on the reaction pressure, temperature, and WHSV. These olefins were further hydrogenated to paraffins using a Ni/SiO2 catalyst. The fuel properties and distillation characteristics of virgin and hydrogenated hydrocarbons were evaluated and compared with those of gasoline to understand their suitability as a transportation fuel in an unmodified combustion engine. The present work further delineates the catalyst stability study for a long time-on-stream (TOS) and extensive characterization of spent catalysts to understand the nature of catalyst deactivation.

Nanocrystallite Zeolite BEA for Regioselective and Continuous Acetyl Functionalization of Anisole Using Acetic Anhydride: Catalyst Deactivation Studies.

Ultrasonic pretreatment of gel composition followed by hydrothermal synthesis produces the nanocrystallite zeolite beta (ZB) with crystal sizes of 10.3, 22.6, and 9.1 nm for ZB-1, ZB-2, and ZB-3, respectively. The effect of ultrasonic pretreatment and the (SiO2/Al2O3) ratio of gel composition on physical, textural properties, and also on the catalytic activity of ZB catalysts with increasing time on stream (TOS) was investigated. The specific surface area and mesopore volume for ZB-1, ZB-2, and ZB-3 are 438, 380, and 429 m2/g and 0.17, 0.05, and 0.14 cm3/g, respectively. The activity studies of ZB-1 and ZB-3 catalysts were confirmed that the anisole conversion initially increased with TOS until it attained the maximum value and then started decreasing further with TOS due to the deactivation of the catalyst caused by the strong interaction of the product with the acidic sites in the mesopore region. However, in the case of ZB-2, the anisole conversion (>45%) was sustained for a longer TOS due to its smaller particle size, low mesopore volume, and more acidic sites in the micropore volume that are inclusively made for retardation in the catlytic deactivation rate. The CHNS and TGA analysis of the spent catalysts confirm that ZB-1 and ZB-3 catalysts are susceptible for a significant coke formation attributed due to strong product retention in their large mesopore volume, which lead to the catalytic deactivation.

Catalytic Performance of Bimetallic Cobalt–Nickel/Graphene Oxide for Carbon Dioxide Reforming of Methane

The design of economical and robust catalysts is a substantial challenge for the dry reforming of methane (DRM). Monometallic nickel-based catalysts used for DRM reactions had comparable activity to noble metals. However, they turned out to be less stable during the reactions. As a continuation of the interest in synthesizing catalysts for DRM, this paper evaluates the catalytic performance of bimetallic Co–Ni catalysts regarding their synergy effect, with graphene oxide (GO) as support for the first time. The synthesized bimetallic catalysts prepared via the wet-impregnation method were characterized using N2 physisorption analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The catalytic test was performed in a stainless-steel tubular reactor in atmospheric conditions with a reaction temperature of 800 °C, time-on-stream (TOS) of 300 min and CH4: CO2 being fed with a ratio of 1:1. The bimetallic 10 wt%Co–10 wt%Ni/GO and 20 wt%Co–10 wt%Ni/GO catalysts had a similar BET specific surface area in N2 physisorption analysis. The XRD pattern displayed a homogeneous distribution of the Co and Ni on the GO support, which was further validated through SEM–EDX. The conversion of CO2, CH4, and H2 yield decreased with reaction time due to the massive occurrence of side reactions. High conversions for CO2 and CH4 were 94.26% and 95.24%, respectively, attained by the bimetallic 20 wt%Co–10 wt%Ni/GO catalyst after 300 min TOS, meaning it displayed the best performance in terms of activity among all the tested catalysts.