N-Doped Fe@CNT for Combined RWGS/FT CO ₂ Hydrogenation

The conversion of CO₂ into chemical fuels represents an attractive route for greenhouse gas emission reductions and renewable energy storage. Iron nanoparticles supported on graphitic carbon materials (e.g., carbon nanotubes (CNTs)) have proven themselves to be effective catalysts for this process. This is due to their stability and ability to support simultaneous reverse water-gas shift (RWGS) and Fischer–Tropsch (FT) catalysis. Typically, these catalytic iron particles are postdoped onto an existing carbon support via wet impregnation. Nitrogen doping of the catalyst support enhances particle–support interactions by providing electron-rich anchoring sites for nanoparticles during wet impregnation. This is typically credited for improving CO₂ conversion and product selectivity in subsequent catalysis. However, the mechanism for RWGS/FT catalysis remains underexplored. Current research places significant emphasis on the importance of enhanced particle–support interactions due to N doping, which may mask further mechanistic effects arising from the presence or absence of nitrogen during CO₂ hydrogenation. Here we report a clear relationship between the presence of nitrogen in the CNT support of an RWGS/FT iron catalyst and significant shifts in the activity and product distribution of the reaction. Particle–support interactions are maximized (and discrepancies between N-doped and pristine support materials are minimized) by incorporating iron and nitrogen directly into the support during synthesis. Reactivity is thus rationalized in terms of the influence of C–N dipoles in the support upon the adsorption properties of CO₂ and CO on the surface rather than improved particle–support interactions. These results show that the direct hydrogenation of CO₂ to hydrocarbons is a potentially viable route to reduce carbon emissions from human activities

Measurement of resistance to solute transport across surfactant-laden interfaces using a Fluorescence Recovery After Photobleaching (FRAP) technique

A noninvasive fluorescence recovery after photobleaching (FRAP) technique is under development to measure interfacial transport in two phase systems without disturbing the interface. The concentration profiles of a probe solute are measured in both sides of the interface by argon-ion laser, and the system relaxation is then monitored by a microscope-mounted CCD camera

Effect of support of Co-Na-Mo catalysts on the direct conversion of CO<inf>2</inf> to hydrocarbons

This study of the effect of support of Co-Na-Mo based catalysts on the direct hydrogenation of CO$_2$ into hydrocarbons (HC) provides guidelines for the design of catalysts for CO$_2$ conversion. We demonstrate that the surface area of the support and the metal-support interaction have a key role determining the cobalt crystallite size and consequently the activity of the system. Cobalt particles with sizes <2 nm supported on MgO present low reverse water gas shift conversion with negligible Fischer-Tropsch activity. Increasing the cobalt particle size to ~15 nm supported on SiO$_2$ and ZSM-5 supports not only substantially increases the CO$_2$ conversion but it also provides high HC selectivities. Further increase of the cobalt particle size to 25–30 nm has a detrimental effect on the global CO$_2$ conversion with HC:CO ratios below 1, however, lower methane selectivity and enhanced formation of unsaturated HC products are achieved. Additionally, the metal-support interaction potentially also has a strong effect on the growth chain probability of the formed hydrocarbons, increasing as the metal-support interaction increases. These evidences demonstrate that CO$_2$ conversion and hydrocarbon distribution can be tuned towards desired products by controlled catalyst design.University of BathThis is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.jcou.2016.06.00

A Fluorescence Recovery After Photobleaching (FRAP) Technique for the Measurement of Solute Transport Across Surfactant-Laden Interfaces

The technique of Fluorescence Recovery After Photobleaching (FRAP) has been applied to the measurement of interfacial transport in two-phase systems. FRAP exploits the loss of fluorescence exhibited by certain fluorophores when over-stimulated (photobleached), so that a two-phase system, originally at equilibrium, can be perturbed without disturbing the interface by strong light from an argon-ion laser and its recovery monitored by a microscope-mounted CCD camera as it relaxes to a new equilibrium. During this relaxation, the concentration profiles of the probe solute are measured on both sides of the interface as a function of time, yielding information about the transport characteristics of the system. To minimize the size of the meniscus between the two phases, a photolithography technique is used to selectively treat the glass walls of the cell in which the phases are contained. This allows concentration measurements to be made very close to the interface and increases the sensitivity of the FRAP technique

Selective Catalytic Hydrogenation in a Structured Compact Multifunctional Reactor

Selective hydrogenation is an important class of chemical reactions for the production of speciality chemicals, pharmaceuticals and petrochemicals. The challenges in this type of reactions are to control selectivity in hydrogenation of poly-functional molecules, and avoid the possible risk of reaction runaway due to the high exothermisity. In this project the fundamentals of liquid-phase hydrogenation reactions in a structured compact multifunctional reactor were investigated. This technology represents an advance over the existing hydrogenation technologies because it exploits the effects of reduced characteristic paths of mass and heat transfer, attained in compact reactor architecture with mm-scale reaction channels and integrated static mixers and micro-heat exchangers. Catalysts based on mesoporous synthetic carbons were developed especially for preparing micro-packed beds in the compact reactor. The investigation resulted in fundamental information on reactor performance for selected model reactions, heat transfer efficiency of the integrated micro-heat exchangers, development of continuous tandem reaction, and evaluation of developed catalysts for hydrogenation and hydrodehalogenation reactions under the continuous flow conditions being used. The results demonstrate that the structured compact multifunctional reactor might be a promising technology to transfer conventional heterogeneous catalysis to flow regime.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Sintesis dan Karakterisasi Komposit Fe 3 O 4 @Zno dengan Metoda Presipitas

SYNTHESIS AND CHARACTERIZATION OF Fe3O4@ZnO COMPOSITE THROUGHPRECIPITATION METHOD. Fe3O4@ZnO composite has been synthesized trough precipitationmethod with the ratio between Fe3O4 and ZnO are 1:1, 1:2, dan 1:3. Characterization of the samplewas performed using X-ray diffractometer (XRD), scanning electron microscope (SEM) equipped withenergy dispersive spectrophotometer (EDS), vibrating sample magnetometer (VSM) andtransmission electron microscope (TEM). The XRD pattern shows that the sample consisted of Fe3O4 nanoparticles and ZnO phases. Magnetic saturation value (Ms) of Fe3O4were measured by VSMobtained about 62.92 emu / g, but then the value of Ms dropped to13.60 emu/g with the addition ofZnO content. TEM observation showed a spherical structure of Fe3O4 aggregate about 20 nm Indiameter, and embedded in the ZnO shell. EDS spectrum revealed that the Fe3O4@ZnO compositeswere only observed three types of elements, namely Fe, Zn and O. This shows evidence that thecoating on the surface of Fe3O4nanoparticles is the outer shell of ZnO. Fe3O4@ZnO composites withFe3O4and ZnO ratio is 1: 2 shows a more homogeneous coating ZnO

Valorization of CO2 through the Synthesis of Cyclic Carbonates Catalyzed by ZIFs

One way to exploit CO2 is to use it as a feedstock for the production of cyclic carbonates via its reaction with organic epoxides. As far as we know, there is still no heterogeneous catalyst that accelerates the reaction in a selective, efficient and industrially usable way. Cobalt and zinc-based zeolitic imidazole frameworks (ZIFs) have been explored as heterogeneous catalysts for this reaction. In particular, we have prepared ZIF-8 and ZIF-67 catalysts, which have been modified by partial replacement of 2-methylimidazole by 1,2,4-triazole, in order to introduce uncoordinated nitrogen groups with the metal. The catalysts have shown very good catalytic performance, within the best of the heterogeneous catalysts tested in the cycloaddition of CO2 with epichlorohydrin. The catalytic activity is due ultimately to defects on the outer surface of the crystal, and varies in the order of ZIF-67-m > ZIF-67 > ZiF-8-m = ZIF-8. Notably, reactions take place under mild reaction conditions and without the use of co-catalysts.The authors acknowledge financial support by MINECO (Spain) through the projects MAT2017-86992-R and CTQ2017-88171-P, “Ministerio de Ciencia e innovación” (PID2020-116998RB-I00), Ministerio de Educación y Formación Profesional (PRX21/00407), and Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital (CIPROM/2021/022, MFA/2022/048)