Dehydrogenation Research Articles

Influence of support properties on the activity of 2Cr-Fe/MgO-MO2 catalysts (M = Ce, Zr, CeZr and Si) for the dehydrogenation of n-octane with CO2

The influence of the support on catalytic activity and stability of supported 2Cr-Fe bimetallic catalysts for the CO2-assisted dehydrogenation (DH) of n-octane has been investigated. Four MgO modified supports viz; MgO-CeO2 (MgCe), MgO-ZrO2 (MgZr), MgO-CeO2-ZrO2 (MgCeZr) and MgO-SiO2 (MgSi) were synthesized by the sol-gel combustion technique. The supported catalysts were in turn prepared by vacuum impregnation and thereafter tested for the CO2-assisted DH of n-octane. The catalysts were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), N2-physisorption, Raman spectroscopy, transmission electron microscopy (TEM), electron dispersive x-ray (EDX), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed reduction and oxidation (H2-TPR and CO2-TPO), electron paramagnetic resonance (EPR) and thermal gravimetric analysis (TGA) techniques. Raman results showed that the CrOx is stabilized as mono- and/or polynuclear Cr(VI) species over the 2Cr-Fe/MgCe catalyst, which are reduced to lower oxidation state species during the DH reaction. The 2Cr-Fe/MgZr, 2Cr-Fe/MgCeZr and 2Cr-Fe/MgSi catalysts stabilized the CrOx as polymerized species, forming the more active Cr-O-Fe polymer units on the catalysts’ surface. XRD, TEM and EDX results showed that the ZrO2-containing supports have smaller particles and stabilized the active metal oxides in a more dispersed amorphous state. The CO2-TPO of the pre-reduced catalysts and EPR of the used catalysts indicated that the 2Cr-Fe/MgCeZr undergoes significant re-oxidation by CO2 during the catalytic process. The 2Cr-Fe/MgCe was the least active, while the 2Cr-Fe/MgZr catalyst showed the best performance and stability over three regeneration cycles. Selectivity to C8 products (octenes and aromatics) was found to strongly depend on the surface basicity of the catalysts. Deactivation of the catalysts was found to follow first order kinetics and coke deposition was identified as the major cause.

Wet torrefaction of biomass waste into levulinic acid and high-quality hydrochar using H-beta zeolite catalyst

Wet torrefaction (WT) is an effective pretreatment method of biomass waste for producing high-quality hydrochar and valuable liquid products. This study delves into how acid catalysts and reaction conditions in WT impact the resulting hydrochar's surface characteristics and elemental composition, as well as the distribution of liquid products. The focus is on utilizing wood cellulose pulp residue (WCPR) as the feedstock with H-Beta zeolite catalyst in a nitrogen-rich environment. The WT process involves a temperature range of 180–260 °C, and reaction durations spanning 15–60 min. The findings reveal that WT conditions, including the catalyst for WCPR, significantly influence the hydrochar's properties and liquid product distribution. With increasing temperature and reaction time, the hydrochar experiences changes, including increased carbon content and reduced oxygen content. The study identifies 260 °C and 30 min as the optimal temperature and time for levulinic acid production, achieving a remarkable selectivity of 62.8% with the H-Beta zeolite catalyst using H2O/WCPR = 10. Various properties of the resulting hydrochar are assessed, including higher heating values (HHVs), decarbonization (DC), dehydrogenation (DH), deoxygenation (DO), enhancement factor, carbon enrichment, surface area, pore diameter, weight loss as well as solid, carbon, hydrogen, and energy yields. The WT + Beta_220 sample, processed at 220 °C for 30 min, exhibited the highest HHV at 30.3 MJ/kg and carbon content at 78.9% in hydrochar compared to various biomass types, with an enhancement factor of 1.51 and carbon enrichment of 1.63, while the sequence of element removal during WT prioritized as DO > DH > DC. Furthermore, it is worth highlighting that the most significant weight loss, increasing from 17.0 to 60.7%, was observed under the same WT conditions. Lastly, a comprehensive reaction pathway is proposed to elucidate the WT of WCPR with the presence of H-Beta zeolite catalyst under these optimized conditions.

Boosting activity of γ-alumina-supported vanadium catalyst for isobutane non-oxidative dehydrogenation via pure V3+

The vanadium-based dehydrogenation (DH) catalyst is becoming a promise alternative to the industrial used Pt- and Cr-based catalysts, due to lower cost and less environmental threat. However, the low DH activity hampered the industrial application of vanadium-based catalysts. Herein, for the first time, we introduce a method to prepare high-efficiency vanadium-based catalyst by constructing pure V3+ species on γ-Al2O3 through treatment of as-prepared thiovanadate. The V3+ species contributes to not only enhancing the DH activity, but also fabricating the V3+-O/S acid-base pair with ideal strength and stability. The isobutene yield can reach as high as 56.9 wt%. Only Lewis acid is recognized on V3+/Al2O3 catalyst, while no Brønsted acid remains. The side-reactions are consequently inhibited, and the selectivity to isobutene is improved. Besides, with the increase of vanadium loadings, the Lewis acid content increases at first and then decreases, and the content of acid sites in middle strength keeps decreasing. Though the deposited coke on V3+/Al2O3 was just 2.5 wt% during 8.5 h consecutive DH reaction, the valence state of vanadium was still influenced and the fraction of inert V4+ species increased steadily. This study will improve the potential for industrial application of vanadium-based DH catalyst, and offer theoretical guidance for optimization of ideal DH catalysts.

Evaluation of the Optimal Conditions for Oxygen-Rich and Oxygen-Lean Torrefaction of Forestry Byproduct as a Fuel

Wood biomass is an alternative to fossil fuels. However, biomass use has several limitations. Torrefaction, in which reduction conditions prevail to overcome these limitations, has been suggested. Here, torrefaction using different wood chips (Liriodendron tulipifera, Populus canadensis, Pinus rigida, and Pinus koraiensis) was conducted under oxygen-rich and oxygen-lean conditions to determine the effects of oxygen. Torrefaction was conducted at 230–310 °C for 1 h. A mass yield difference of 3.53–20.02% p (percentage point) was observed between oxygen-lean and oxygen-rich conditions. The calorific value increased by a maximum of 50.95% and 48.48% under oxygen-rich and oxygen-lean conditions, respectively. Decarbonization (DC), dehydrogenation (DH), and deoxygenation (DO) occurred in the following order because of dehydration and devolatilization during biomass torrefaction: DO > DH > DC. The calorific value of the torrefied biomass increased linearly with the extent of all three processes. The combustibility index and volatile ignitability were calculated based on proximate composition to suggest the optimal conditions for replacing anthracite and bituminous coal. This study provides suggestions for stable operation in a standard boiler design.

Kinetic analysis to describe Co-operative redox enhancement effects exhibited by bimetallic Au–Pd systems in aerobic oxidation

Recent work has demonstrated that, for bimetallic Au–Pd systems, the rate of catalytic alcohol and formyl dehydrogenation (DH) is intrinsically linked to the rate of oxygen reduction (ORR) within the same system.

Role of Catalyst Support's Physicochemical Properties on Catalytic Transfer Hydrogenation over Palladium Catalysts

AbstractCatalytic transfer hydrogenation (CTH) is a promising reaction for valorisation of bio‐based feedstocks via hydrogenation without needing to use H2. Unlike standard hydrogenation, CTH occurs via dehydrogenation (DHD) of a hydrogen donor (H‐donor) and hydrogenation (HYD) of a substrate. Therefore, the “ideal” CTH catalyst must balance the catalysis of both reactions to maximize the hydrogen transfer between H‐donor and substrate with minimal H2 loss to gas (high atom efficiency). Additionally, the H‐donor must be highly stable to prevent secondary reactions with the substrate.Herein we study the impact of the catalyst's properties on CTH of guaiacol using bicyclohexyl, a liquid organic hydrogen carrier, as a H‐donor. The reaction was promoted by palladium dispersed on three typical support materials (γ‐Al2O3, MgO, and SiO2). The performance of these catalysts in the conversion of bicyclohexyl and guaiacol was evaluated, allowing to estimate the H‐transfer efficiency, as well as the potential for recycling the spent H‐donor (bicyclohexyl). The apparent activation energies for DHD of bicyclohexyl and HYD of guaiacol revealed that slow DHD combined with fast HYD, as is the case with Pd/MgO, favours hydrogen transfer efficiency and selectivity towards hydrogenated products. In addition, an investigation of the DHD of bicyclohexyl and HYD of guaiacol independently showed that the affinity between the organic molecules and the support significantly impacts CTH. Indeed, Pd/SiO2 was highly active for both reactions individually and almost inactive for CTH. Consequently, these findings highlight the importance of the interaction between solvent‐substrate‐support in designing catalysts for transfer hydrogenation.

Isobutane dehydrogenation over high-performanced sulfide V-K/γ-Al2O3 catalyst: Modulation of vanadium species and intrinsic effect of potassium

Compared with industrial used Pt- and Cr-based catalyst in dehydrogenation (DH) of light alkanes, the sulfide V-K/γ-Al2O3 catalyst reported in this study shows lower cost and toxicity, and significant DH performance. The yield to isobutene reached as high as 52.9%, which is among the highest reported to date. We attribute such high isobutene yield to the precise modulation of polymerization degree for vanadium species via doping of potassium and indicating that the synergy between vanadium species and acid sites is critical to enhance the DH performance. Our previous work showed sulfidation promoted the increase of DH performance for vanadium-based catalyst, and we go further in this study to explore the correlation between increased range of DH performance and the added potassium. The different loaded potassium leads to variation in sulfidation degree, affecting the properties of vanadium species and acid properties consequently. The potassium was distributed uniformly on surface of the sulfide vanadium-based catalyst and was predominantly bonded with the vanadium species rather than with the γ-Al2O3 support. With increasing the potassium amount from 0 to 3 wt%, the acid amount kept decreasing, and some specific strong acid sites appeared once adequate sulfur was introduced in the V-K/γ-Al2O3 catalyst. The characterization and DFT results both revealed that the doped potassium contributes to regulating the vanadium species in the oligomeric state. The synergy between vanadium species and acid properties was regulated by the added potassium simultaneously, and thus the DH performance was enhanced. This study provides promising strategy for preparation of environment-friendly model industrial DH catalyst.

Assessment and comparison of ordered & non-ordered supported metal oxide catalysts for upgrading propane to propylene

Propylene is an important chemical feedstock that is largely produced via cracking of oil-derived naphtha. Direct conversion of propane into propylene may be a more attractive alternative. Specifically, propane dehydrogenation (DH) and oxidative dehydrogenation (ODH) are promising for this transformation, albeit only DH has been industrially implemented. However, even the best DH catalysts (Pt-based) still suffer from deactivation. VOx- and BOx-based ODH catalysts result in significant over-oxidation and lack a mechanistic understanding. A common challenge in developing these catalysts is the broad distribution of surface species caused by the use of non-ordered catalyst supports. This hampers clear structure-performance correlations. Recent progress in the preparation of well-defined active sites on ordered supports has brought about improved catalysts, as well as fundamental insight into the working mechanism. This review will highlight recent advancements in the development of these catalysts and provide direction on the use of ordered supports for propane upgrading.

Upgrading properties of biochar fuel derived from cassava rhizome via torrefaction: Effect of sweeping gas atmospheres and its economic feasibility

Torrefaction is a promising biomass thermal conversion technology to produce biochar due to its ease of operation and mild operating conditions. In this study, cassava rhizome (CR) was torrified under various sweeping gas types (nitrogen (N2), carbon dioxide (CO2), mixture gas (N2 + CO2)) and flow rates (50, 150, 250 mL/min) at 200–300 °C for 30 min. The experimental results show that fuel properties of CR were remarkably upgraded after torrefaction. Sweeping gas has less effect on fuel properties of torrified CR than torrefaction temperature. Torrefaction under CO2 atmosphere produced the biochar with minimum ash content. Torrefaction at 300 °C under 50 mL/min CO2 was recommended as the promising condition to produce biochar replacing lignite coal. Thermal properties and chemical functional groups of the derived biochar suggested that torrefaction process removed mainly oxygen and hydrogen contents which could be achieved through decarbonization (DC), dehydrogenation (DH), and deoxygenation (DO) pathways. Economic feasibility revealed that the torrefaction of CR is cost-advantage under the proposed condition.

Effect of support molding method on the performances of propane dehydrogenation catalyst

Effect of support molding method on the performances of propane dehydrogenation catalyst

Therapeutic Role of Mitochondria Targeted Curcumin against Pseudomonas aeruginosa Induced Oxidative Stress in Thyroid Gland of Female Swiss albino Mice

Bacteria are found universally and contaminate the soil, air and water. Through contaminated air, water and soil bacteria reach inside the body and causes immense harm. The problem of thyroid is that, it affects the public health worldwide. The main purpose of this investigation is to find out the toxic effects of Pseudomonas aeruginosa on thyroid gland and preventive role of mitochondria targeted curcumin in bacterial induced thyroid toxicity in female Swiss albino mice. The animals are separated in different groups. Group I served as control and Group II administered with effective dose of Pseudomonas aeruginosa . Group III co-treated with mitochondria targeted curcumin for the period of 14 days. With the completion of treatment period blood serum and tissue samples were collected for determining the level of thyroid hormones and oxidative stress. In this investigation shows that mice exposed to bacteria have decreased T3 and T4 concentration as compared to control and co-treated mice have some elevated level of T3 and T4 hormones as compared to bacteria treated mice. In the biochemical study it is found that the increased lactate dehydrogenate, catalase activity, superoxide dismutase and lipid peroxidation and decreased glutathione reductase points towards the induced oxidative stress in thyroid gland. It is concluded that the exposure to Pseudomonas aeruginosa causes thyroid problem and treatment with mitochondria targeted curcumin prevents the induced toxicity.

Synergistic effects of CO2 on ex situ catalytic pyrolysis of lignocellulosic biomass over a Ni/SiO2 catalyst

This work laid emphasis on catalytic pyrolysis of Styrax japonicus to construct a biomass-to-energy conversion platform. CO2 was particularly chosen to enhance the catalytic pyrolysis of the biomass waste, in reference to N2-purged pyrolysis. The specific roles of CO2 on pyrolysis of S. japonicus in line with synergistic effect of Ni-based catalysts was investigated. It was shown that CO2 played as an oxidant for CO formation via homogeneous gas phase reaction of CO2 with volatile organic carbons (VOCs) liberated from the thermolysis of S. japonicus. Ni/SiO2 catalyst expedited dehydrogenation (DH) of the VOCs, resulting in significant H2 generation and alteration of aromaticity in VOCs. Each CO2 and Ni catalyst independently enhanced CO and H2 formation, respectively, and their synergistic effects were shown at ≥ 600 °C. Coke deposition on the Ni/SiO2 catalyst was confirmed after catalytic pyrolysis, while the suppression of coke formation on the catalyst surface was achieved under the CO2 environment.

Formic Acid Dehydrogenation by a Cyclometalatedκ3‐CNN Ruthenium Complex

Hydrogen utilization as a sustainable energy vector is of growing interest. We report herein a cyclometalated ruthenium complex [Ru(κ3‐CNN)(dppb)Cl], originally described by Baratta, to be active in the selective dehydrogenation (DH) of formic acid (FA) to H2and CO2. TON's of more than 10000 were achieved under best conditions without observation of CO (detection limit 10 ppm). The distinguished behavior of the catalyst was explored varying the starting conditions. Our observation revealed the complex [Ru(κ3‐CNN)(dppb)(OOCH)] as key species in the catalytic cycle.

Fuel properties of biochar from torrefaction of ground coffee residue: effect of process temperature, time, and sweeping gas

Ground coffee residue (GCR) was torrified under nitrogen or carbon dioxide atmosphere. Effect of torrefaction parameters on fuel properties of biochar was investigated by varying process temperature, residence time, and sweeping gas flow rate over the range of 200–300 °C, 30–60 min, and 50–250 mL/min, respectively. Severe torrefaction (300 °C) short residence time (30 min) under low carbon dioxide flow rate (50 mL/min) was determined as a promising condition to produce biochar as solid fuel. H/C and O/C atomic ratios, HHV, and energy yield of the obtained biochar were 0.94 and 0.14, 31.12 MJ/kg, and 48.04%, respectively, which were comparable with the properties of sub-bituminous coal. The calculated decarbonization (DC), dehydrogenation (DH), and deoxygenation (DO) indicated that torrefaction led to major losses of oxygen and hydrogen. The analysis of thermal decomposition properties and surface chemical functional groups revealed that temperature substantially affected biochar properties, while the effect of sweeping gas was only marginal.

Co-Production of 1,2-propandiol and Ethyl Lactate from the Conversion of Glycerol co-fed with Bio-Ethanol over Reduced Cu 0 . 3 Mg 1 . 7 Al LDH-derived Oxide Catalyst without External Hydrogen

Usually, the hydrogenolysis of glycerol into 1,2-propandiol requires H2 supply in the acetol hydrogenation step to 1,2-propandiol. However, in-situ hydrogen can be generated from glycerol dehydrogenation and glycerol reforming using metal catalysts. Moreover, ethanol can be co-fed as a hydrogen donor for this reaction and produce ethyl lactate via esterification with lactic acid which is by-product from glycerol conversion. In this study, the promotion effect of Cu partially-substituted Mg1.7Al mixed oxide was investigated on the conversion of glycerol co-fed with bio-ethanol in a PARR-reactor at 180 oC for 4 h without hydrogen feeding. Then, the products were analyzed using GC-MS/TOF. The catalysts were characterized using BET, XRD, XPS, XRF, and TPDRO. As a result of the Mg2AlO based catalyst, the glycerol can be converted to 1,2-propaniol, acetone, and acetaldehyde without ethyl lactate production at this condition. The reduced Cu0.3Mg1.7Al LDH-derived catalyst significantly enhanced the selectivity of 1,2-propandiol and ethyl lactate to 47.3 and 22.8 %. 1,2-Propandiol and ethyl lactate as specialty chemicals were found to be co-produced from co-feeding glycerol and bio-ethanol using the reduced Cu0.3Mg1.7Al LDH-derived catalyst.

Oxidative Dehydrogenation of Ethylbenzene into Styrene by Fe-Graphitic Catalysts.

Carbon-based catalysts have attracted much attention for the dehydrogenation (DH) of organic molecules, due to their rich active sites, high conversion efficiency, and selectivity. However, because of their poor stability at high operation temperature and relatively high cost, their practical applications have been limited. Here, we report a simple ball-milling-induced mechanochemical reaction which can introduce iron (Fe) and different functional groups (mostly stable aromatic C═O after heat-treatment) along the edges of graphitic nanoplatelets. The resulting Fe-graphitic nanoplatelets (Fe-XGnPs, X = H, C, N, or V) provide active sites for the oxidative dehydrogenation (ODH) of ethylbenzene into styrene. Among them, Fe-NGnPs (X = N) displayed the highest performance for styrene production at low temperature (∼11.13 mmol g-1 h-1, 450 °C) with high selectivity and durability.

Catalytic Dehydrogenation of Formic Acid with Ruthenium‐PNP‐Pincer Complexes: Comparing N‐Methylated and NH‐Ligands

AbstractComplexes Ru(H)(Cl)(CO)(HN{CH2CH2P(iPr)2}2) 7 and Ru(H)(Cl)(CO)(CH3N{CH2CH2P(iPr)2}2) 8 were compared for the selective dehydrogenation (DH) of formic acid (FA) at different pH values. Remarkably, highest activities were observed in acidic environment (pH 4.5). Under all investigated conditions, the N‐methylated complex 8 showed improved performance compared to 7. These observations can be mechanistically explained with protonation of 4H/3Me being the key step in formic acid DH for both complexes.

Electrolyte-Assisted Hydrogen Storage Reactions

Use of electrolytes, in the form of LiBH4/KBH4 and LiI/KI/CsI eutectics, is shown to significantly improve (by more than a factor of 10) both the dehydrogenation and full rehydrogenation of the MgH...

Highly Energy-Efficient Combination of Dehydrogenation of Methylcyclohexane and Hydrogen-Based Power Generation

Hydrogen, H2, has been well known as one of potential energy storages in utilization of renewable energy with its intermittent characteristic. However, H2, which is in gas phase at standard pressure and temperature, has challenging problem of storage, transportation, and low volumetric energy density. As one of the solution, H2 storage in (C7H8)/methylcyclohexane (MCH, C7H14) cycle is one of the effective and reversible methods. In this study, an integrated power generation cycle is investigated, including the the dehydrogenation process and the combined cycle power generation. Comprehensive analysis on heat circulation was performed through an enhanced process integration to ensure the high energy-efficiency system. Thermal energy required for highly endothermic dehydrogenation reaction was supplied from air-fuel combustion to ensure the effective heat recovery of the system. The performance of proposed system is compared to the Graz cycle-based system, one of the cycle of power generation cycle from H2. The comparison result shows that the proposed integrated system has a significantly higher power-generating efficiency. Additionally, with dehydrogenation included in the system, the proposed system showed a system efficiency of 53.7 %, compared with the Graz cycle based system at 22.7 % under the same operating condition.

Lactate in cardiogenic shock - current understanding and clinical implications.

Adenosine triphosphate (ATP) is an essential substrate metabolite in human beings. Mitochondrial oxidative phosphorylation provides > 95% of ATP with the remainder derived from glycolysis or tricarboxylic acid cycle (TCA). In normal hearts, acetyl-CoA is synthesized from the β-oxidation of free fatty acids (FFA) and the oxidation of pyruvate. Pyruvate is synthesized from glycolysis and can be submitted either for decarboxylation to acetyl-CoA or for dehydrogenation to lactate. Moreover, pyruvate, as well as lactate, plays a key role in aerobic glucose metabolism which is highly dependent on ubiquitous regulatory mechanisms. Many recent advances in molecular biology, genetics, and physiology have revealed new insights into the metabolic flux of lactate. The initial perception characterized by increased lactate production and accumulation in peripheral tissues in anaerobic conditions has been recently contested. The paradigm of increased lactate concentration in the anaerobic setting is discussed according to contemporary reports. Nevertheless, the clinical role of lactate as a prognostic factor in cardiovascular diseases is undisturbed, especially in the field of innovative technology of left/bi ventricular-assist devices and biochips where it reassured its diagnostic and prognostic impact on the cardiovascular system.