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In this paper, a series of cobalt catalysts supported on reduced graphene oxide (rGO) nanosheets with the loading of 5, 15 and 30 wt-% were provided by the impregnation method. The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis (FTS). The prepared catalysts were carefully characterized by nitrogen adsorption-desorption, hydrogen chemisorption, X-ray diffraction, Fourier transform infrared spectro-scopy, Raman spectroscopy, temperature programmed reduction, transmission electron microscopy, and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets. The results showed that with increasing the cobalt loading on the rGO support, the carbon defects are increased and as a consequence, the reduction of cobalt is decreased. The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size. The products selectivity results indicated that the methane selectivity decreases, whereas the C5+ selectivity raises with the increasing of the cobalt particle size, which can be explained by chain propagation in the primary chain growth reactions.

BACKGROUND: The dry reforming of methane (DRM) process has received considerable attention for the production of syngas owing to its great environmental and economic benefits. LaNiO₃ and La₀.₅Sr₀.₅NiO₃ nanoparticles were synthesized with the co‐precipitation procedure using distilled and magnetic distilled water, and examined as catalysts in DRM. RESULTS: The structure and morphology of the prepared nanoparticles were characterized by X‐ray diffraction, the Brunauer–Emmett–Teller method, scanning and transmission electron microscopy, and temperature‐programmed reduction, desorption and hydrogenation techniques. The experimental results proved that the treated La₀.₅Ni₀.₅SrO₃ catalyst had better initial performance in DRM in comparison with the LaNiO₃ catalyst, due to its greater surface basicity. The orientation for deposition of carbon over the surface of the consumed catalysts was as follows: La₀.₅Sr₀.₅NiO₃ ₜᵣₑₐₜₑd > La₀.₅Sr₀.₅NiO₃ ₙₒₙ‐ₜᵣₑₐₜₑd > LaNiO₃ ₙₒₙ‐ₜᵣₑₐₜₑd > LaNiO₃ ₜᵣₑₐₜₑd. CONCLUSION: Among the synthesized catalysts, the treated La₀.₅Sr₀.₅NiO₃ sample exhibited higher initial DRM activity, due to its greater surface basicity. Also, the higher surface basicity of the strontium‐substituted catalyst led to an increase in CO₂ desorption and coke deposition according to the Boudouard reaction. © 2020 Society of Chemical Industry

Introduction:Current challenges to successful clinical translation of therapeutic nanomedicine have discouraged many stakeholders, including patients. Significant effort has been devoted to uncover...

The effect of carbon nanotubes (CNTs) functionalization as a support on cobalt catalyst activity in Fischer–Tropsch synthesis (FTS) was investigated. The CNTs functionalized with hydrogen peroxide and sonicated via a pulsing method with different pulse time. The cobalt catalysts synthesized by the impregnation method. Confinement of concise Co particle inside the functionalized CNTs at a shorter time of sonication (Co/FCNTs-10 with 10-s pulses of sonication) was confirmed by TEM analysis. The Co/FCNTs-10 catalyst show higher FTS activity than nonsonicated Co/CNTs and Co/FCNTs-20 with 20-s pulses of sonication. The activation energies obtained through the kinetic results for FTS reaction over Co/FCNTs-10, Co/FCNTs-20, and Co/CNTs are 92.1, 98.8, and 102.7 kJ/mol. The heat of hydrogen adsorption is calculated −40.8, −34.2, and −21.4 (kJ/mol) for Co/CNTs, Co/FCNTs-20 and Co/FCNTs-10 catalysts, respectively. Co/FCNTs-10 catalyst shows higher hydrogen spillover than nonsonicated Co/CNTs catalyst.

Amine-based solid sorbents represent promising replacements for aqueous alkanolamines for CO2 capture because they reduce significantly the sorbent regeneration energy and avoid instrument corrosio...

The adult myocardium has a limited regenerative capacity following heart injury and the lost cells are primarily replaced by fibrotic scar tissue. Suboptimal efficiency of current clinical therapies to resurrect the infarcted heart results in injured heart enlargement and remodeling to maintain its physiological functions. These remodeling processes ultimately leads to ischemic cardiomyopathy and heart failure (HF). Recent therapeutic approaches (e.g., regenerative and nanomedicine) have shown promise to prevent HF post-myocardial infarction in animal models. However, these preclinical, clinical, and technological advancements have yet to yield substantial enhancements in the survival rate and quality of life of patients with severe ischemic injuries. This could be attributed largely to the considerable gap in knowledge between clinicians and nano-bioengineers. Development of highly effective cardiac regenerative therapies requires connecting and coordinating multiple fields, including cardiology, cellular and molecular biology, biochemistry and chemistry, and mechanical and materials sciences, among others. This review is particularly intended to bridge the knowledge gap between cardiologists and regenerative nanomedicine experts. Establishing this multidisciplinary knowledge base may help pave the way for developing novel, safer, and more effective approaches that will enable the medical community to reduce morbidity and mortality in HF patients.

This paper focuses on the development of a rigorous model for isothermal CO2 adsorption columns which describes the spatiotemporal dynamics of CO2 concentrations in the bulk and solid bed by a set of partial and location-varying ordinary differential equations. By considering both dispersion and convection phenomena, the model provides the spatiotemporal behavior of the adsorption rate and circumvents the unphysical simplifying assumptions of linear driving force and uniform adsorption rates through the column length invoked in previous modeling efforts. The proposed model is then employed to compute physical quantities originating from material conservation laws such as the adsorption rate constant and CO2 adsorption capacity from a set of experimental data without using empirical parameter assumptions invoked in previous research. The spatiotemporal dynamics of CO2 adsorption in an aminosilica packed bed are successfully predicted by the proposed model. The adsorption rate constant and capacity of the b...

Protein unfolding induced by nanoparticles (NPs) can lead to exposure of cryptic epitopes that might dictate biological identity and affect NP biological fate (e.g., blood circulation time, biodistribution, and tumor accumulation). Here, we monitor the conformation of fluorescence resonance energy transfer (FRET)-labelled fibronectin (FN) on corona-coated gold NPs. We found that the labelled FN proteins, which directly accessed the gold NP surface, underwent more pronounced conformational changes than those associated with the protein corona via protein-protein interactions. FRET and liquid chromatography-mass spectrometry analyses demonstrated that NP size/concentration, pH change, and the level of surface coverage by the corona can tune the accessibility of labelled FN to the gold NP surface. Although some subsequently adsorbing proteins accessed the NP surface thanks to incomplete surface coverage and protein exchange (the Vroman effect), most outer-layer proteins could not directly bind to the NP surface, blocked by pre-adsorbed corona layers. This finding was also partially confirmed by isothermal titration calorimetry (ITC) analysis. These results suggest the proof-of-concept that outermost-layer proteins with modestly changed conformation rather than unfolded proteins at the gold NP surface effectively create the NPs' biological identity, which might have important implications on biological fates of gold NPs.

Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.

In this study the effect of catalyst nanoparticle size on the Fischer–Tropsch synthesis (FTS) activity is investigated on iron catalyst. A series of iron oxide particles doped by adding cupper and lanthanum were prepared as a catalyst via precipitation by microemulsion method. Because of the role of iron carbide in FTS reaction by iron catalysts, the iron carbide particle sizes was evaluated after activation and considered as active phase in this paper. The catalytic results indicated that FTS activity increased and passed through a maximum when the iron particle size increased. A size-dependent kinetic model for FTS rates was developed using a thermodynamic analysis method. The model parameters measured by experimental results and the effect of various active sizes on these parameters was evaluated. Calculated size dependent model parameters were employed for evaluation of surface tension energy (σ) for iron catalyst and size-independent activation energy for FTS reaction.

Silica-supported Pd and shell/core PdAu nanoparticles of a similar size were evaluated for neopentane conversion. Monometallic Pd exhibited poor neopentane isomerization selectivity in favor of high selectivity to primary and secondary hydrogenolysis products. Similarly sized PdAu catalysts of increasing Pd weight loading were synthesized to evaluate the effect of increasing Pd monolayers on neopentane conversion. All PdAu catalysts had neopentane conversion selectivity within the range of monometallic Pd catalysts from previous work (~5–30%). However, there was an inverse relationship between Pd weight loading and neopentane isomerization selectivity. The increase in isomerization selectivity did not correlate to a decrease in heats of adsorption as seen with monometallic Pd catalysts, but was correlated with the catalyst surface structure which suggests a geometric effect as the cause for changes in catalytic performance rather than an electronic effect.

The detailed kinetics of Fischer-Tropsch synthesis over an industrial Fe/Cu/La/Si catalyst was studied in a continuous spinning basket reactor under the conditions relevant to industrial operations. Reaction rate equations were derived on the basis of Langmuir-Hinshelwood-Hougen-Watson type models for Fischer-Tropsch synthesis based on possible reactions sets originated from the carbide, enolic and combined enol/carbide mechanisms. Kinetic model candidates were evaluated by the global optimization of kinetic parameters, which were realized by first minimization of multi-response objective functions with conventional Levenberg-Marquardt method. It was found that an enolic mechanism based model could produce a good fit of the experimental data. The activation energy for paraffin formation is 95 kJ·mol −1 which is smaller than that for olefin formation (121 kJ·mol −1 ).

The kinetic modeling of the water-gas-shift (WGS) reaction over a Fe/Cu/La/Si catalyst under Fischer–Tropsch synthesis (FTS) reaction condition was investigated. A number of Langmuir–Hinshelwood–Hougen–Watson type rate expression based on possible reaction sets, originated from the formate and direct oxidation mechanisms, were derived. Four models were used to fit the experimental data over a wide range of reaction condition. WGS rate expressions based on the formate mechanism were found to provide an improved description for WGS kinetic data. Experimental kinetics results showed that the WGS reaction under FTS reaction conditions was far from equilibrium.

The effects of Mg, La and Ca promoters on primary and secondary CO2 and H2O formation pathways during Fischer-Tropsch synthesis on precipitated Fe/Cu/SiO2 catalysts are investigated. The chemisorbed oxygen atoms in the primary pathway formed in the CO dissociation steps reacted with co-adsorbed hydrogen or carbon monoxide to produce H2O and CO2, respectively. The secondary pathway was the water-gas shift reaction. The results indicated that the CO2 production led to an increase in both primary and secondary pathways, and H2O production decreased when surface basicity of the catalyst increased in the order Ca > Mg > La.

A series of Ce-promoted Mn-Na 2 WO 4 /SiO 2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane (OCM) was investigated at atmospheric pressure in a micro-quartz-tube reactor. The catalysts were characterized by X-ray diffraction (XRD), temperature program reduction (TPR) and BET surface area. Ce promoter increased surface area and Na 2 WO 4 species dispersion, which enriched the amount of the surface species. In addition, Ce promoter increased the Na/W species reduction, but the reduction peak shifted to higher temperature. Stability test of 5wt%Ce catalyst indicated suitable performance and stability. The selectivity and yield of C 2+ hydrocarbons after 50 h operation reached 65.5% and 19.6%, respectively, at 840 °C over 5wt%Ce-2wt%Mn-5wt%Na 2 WO 4 /SiO 2 catalyst.

Fe-HZSM-5 bifunctional catalyst activity and products selectivity in Fischer–Tropsch synthesis (FTS) were investigated. HZSM-5 zeolite and iron catalyst were become near to each other step-by-step. In first step, zeolite just affected gaseous products after FTS reaction on iron catalyst. In other conditions, zeolite was incorporated in FTS process to be included in cracking and aromatization reactions. The results revealed that role of zeolite in overall reaction were increased from completely separated condition to physically mixed condition. Addition of binder in physically mixed condition was led to cover the active sites of bifunctional iron–zeolite catalyst and decrease activity of zeolite and iron catalyst. Also, decreasing amounts of Bronsted acid sites after FT reaction was related to zeolite incorporation in overall reaction that was decreased by closing the zeolite to the iron catalyst. HZSM-5 addition to FT catalyst suppressed the formation of oxygenates, which are converted to hydrocarbons on the zeolite acid sites. Furthermore, zeolite increased CO 2 selectivity slightly because of oxygenate decomposition into CO 2 as a side reaction that showed by co-feeding of light alcohol (with 14 C) to FTS in previous works.

Nano-structure Fe2O3, CuO and La2O3 components were prepared by micro-emulsion method and then Fe/Cu/La/SiO2 nano-structure catalyst was prepared by mixing and re-slurring the mixture by tetraethylorthosilicate (TEOS). The catalyst composition was designated in term of the atomic ration as: 100Fe/5.64Cu/0.1La/19Si. Structural characterization of nano-structured Fe2O3, CuO and La2O3 components was performed by Transmission Electron Microscopy (TEM), powder X-ray diffraction, Temperature Programmed Reduction (TPR) techniques. Particle size for obtained components was about 20, 21.6 and 12.6 nm for Fe2O3, CuO and La2O3 respectively determined by using XRD pattern (Scherrer equation) and TEM images. Catalytic activity and product selectivity were conducted in a fixed-bed stainless steel reactor and compared with conventional iron catalyst. The results reveal that reducing particle size of catalyst increased the catalyst performance. Also, olefin/paraffin ratios decreased in comparison with conventional catalyst.

Oxidative coupling of methane is a direct way to obtain C2 hydrocarbon, and Mn-Na-W/SiO2 catalyst is the most promising among all the catalysts. The 2%Mn/5%Na2WO4/SiO2 catalyst was prepared by the incipient wetness impregnation method. A 7-step heterogeneous reaction model of the oxidative coupling of methane to C2 hydrocarbons was conducted by co-feeding methane and oxygen at a total pressure of 1 bar over the catalyst. The kinetic measurements were carried out in a micro-catalytic fixed bed reactor. The kinetic data were obtained at the appropriate range of reaction conditions (4 kPa CH 4

The effects of Mg, La and Ca promoters on the structure, surface area, reduction, carburization and catalytic behavior of precipitated Fe/Cu/SiO2 Fischer–Tropsch synthesis (FTS) catalysts were investigated. The catalysts are characterized using X-ray diffraction (XRD), H2 and CO temperature-programmed reduction (TPR) techniques. The catalysts were assessed in terms of their FTS activity and product selectivity using two superimposed Anderson–Schulz–Flory (ASF) models. The performance of the catalysts was tested in a fixed-bed reactor at 563 K, 1.7 MPa and feed (syngas with H2/CO molar ratio of 1) flow rates of 4.9 and 13.3 nl h−1 g(Fe)−1. It was found that Mg, La and Ca promoters have negligible effects on the textural properties of the catalyst. Promoter addition enhanced the surface basicity of the catalyst in the order Ca > Mg > La. Addition of the promoters with the atomic ratio of X/Fe = 0.02 (X = Ca, Mg and La) improved the reduction and carburization during the reduction and FTS reaction in the order of Ca > Mg > La. The promoters suppressed the rate of hydrogenation reaction in the order of Ca > Mg > La. The results also indicate that Mg, La and Ca promoters can improve the CO conversion and WGS reaction, suppress the formation of methane, enhance the selectivities to olefin and higher molecular weight products, enhance the break in ASF distributions in the order of Ca > Mg > La due to increasing the catalyst surface basicity and dropping the reducibility.

A physical mixture of alkali-promoted iron catalyst with binder based on Fischer-Tropsch synthesis and an acidic co-catalyst (HZSM5) for syngas conversion to hydrocarbons was studied in a fixed bed micro reactor. Deactivation data were obtained during the synthesis over a 1400 h period. The deactivation studies on iron catalyst showed that this trend followed the phase transformation Fe2.2C (ɛ) → Fe5C2 (χ) → Fe3C (θ), and the final predominant phase of the catalyst was Fe3C (θ). Deactivation of zeolite component in bifunctional catalyst may be caused by coking over the zeolitic component, dealumination of zeolite crystals, and migration of alkali promoters from iron catalyst under synthesis conditions. The deactivation rate of iron catalyst was also obtained.