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XANES K-edge spectra of potassium promoter in precipitated Fe catalysts were acquired following activation by carburization in CO and as a function of time on-stream during the course of a Fischer–Tropsch synthesis run for a 100Fe:2K catalyst by withdrawing catalysts, sealed in wax product, for analysis. CO-activated and end-of-run spectra of the catalyst were also obtained for a 100Fe:5K catalyst. Peaks representing electronic transitions and multiple scattering were observed and resembled reference spectra for potassium carbonate or potassium formate. The shift in the multiple scattering peak to higher energy was consistent with sintering of potassium promoter during the course of the reaction test. The catalyst, however, retained its carbidic state, as demonstrated by XANES and EXAFS spectra at the iron K-edge, suggesting that sintering of potassium did not adversely affect the carburization rate, which is important for preventing iron carbides from oxidizing. The method serves a starting point for developing better understanding of the chemical state and changes in structure occurring with alkali promoter.

One-pot carbon-Ferrier rearrangement of glycals with unactivated aryl methyl ketones has been developed under mild Silyl triflate catalysis. Keto methyl group of various aryl methyl ketones without being converted into silyl enol ether could directly attack anomeric position of glycals to form keto functionalized C-glycosides in moderate to good yields with high α-selectivity. The versatility of this method has been extended to the synthesis of a small library of chromanone 3-C-glycosides.

Mn2CoReO6, the fourth known magnetic transition-metal-only double perovskite oxide (space group P21/n) was synthesized at high pressure and temperature (8 GPa, 1350 ?C). Large structural distortions are induced by the small A-site Mn2+ cations. Mn2CoReO6 exhibits complex magnetic properties with a robust antiferromagentic order (TN = 94 K) involving all the cation sublattices .

The effect of co-fed hydrogen chloride (HCl) in syngas on the performance of iron and cobalt-based Fischer–Tropsch (FT) catalysts was investigated in our earlier studies (Ma et al. in ACS Catal 5:3124–3136, 2015; Davis et al., DOE final report, 2011; Gnanamani et al. in Catal Lett 144:1127–1133, 2014). For an iron catalyst, lower HCl concentrations (

The effect of ammonia in syngas on the performance of various supported cobalt catalysts (i.e., Al2O3, TiO2 and SiO2) was investigated during Fischer–Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). The addition of ammonia (10 ppmv NH3) caused a significant deactivation for all supported cobalt catalysts, but the rate of deactivation was higher for the silica-supported catalysts relative to the alumina and titania-supported catalysts used in this work. Ammonia addition had a positive effect on product selectivity (i.e., lower light gas products and higher C5+) for alumina and titania-supported catalysts compared to ammonia free conditions, whereas, the addition of ammonia increased lighter hydrocarbon (C1–C4) products and decreased higher hydrocarbon (C5+) selectivity compared to ammonia-free synthesis conditions for the silica-supported catalyst. For alumina and titania-supported catalysts, the activity almost recovered with mild in-situ hydrogen treatment of the ammonia exposed catalysts. For the silica-supported catalyst, the loss of activity is somewhat irreversible (i.e., cannot be regained after the mild hydrogen treatment). Addition of ammonia led to a significant loss in BET surface area and changes in pore diameter (consistent with pore collapse of a fraction of pores into the microporous range as described in the literature), as well as formation of catalytically inactive cobalt support compounds for the silica-supported catalyst. On the other hand, the pore characteristics of alumina and titania-supported catalysts were not significantly changed. XANES results of the ammonia exposed silica-supported catalysts further confirm the formation of cobalt-support compounds (cobalt silicates).

We appreciate Saudi Basic Industries Corporation (SABIC) for financial support. We gratefully thank Dr. Elodie Guyonnet and Dr. Janet C. Mohandas for helpful discussions. KAUST Supercomputing Laboratory (KSL) is acknowledged for the allocated computing resources.

Palladium catalysed ligand free direct dehydrogenative C-3 alkenylation of pyrones and unprotected pyridones from unactivated alkenes is reported. The process is highly regio- and chemoselective. A wide variety of alkene partners reacted to broaden the substrate scope of the process. The effect of the C-3 substituent on the rate of reaction is also studied.

The effect of the reducing agent on the performance of a ruthenium nanoparticle catalyst was investigated during aqueous-phase Fischer–Tropsch synthesis using a 1 L stirred tank reactor in the batch mode of operation. For the purpose of comparison, the activity and selectivity of NaY zeolite supported Ru catalyst were also studied. NaBH4 and hydrogen were used as reducing agents in this study, and hydrogen reduced catalysts exhibited higher activities than the NaBH4 reduced catalysts, because of higher extent of reduction and a relatively lower tendency toward agglomeration of Ru particles. The Ru nanoparticle catalyst displayed higher activities than the NaY zeolite supported Ru catalyst for both reducing agents. NaBH4 reduced catalysts are less active and the carbon dioxide selectivity is higher than the hydrogen reduced catalysts. Nevertheless, the activity of the supported Ru catalyst (Ru/NaY) was 75 % of that of the Ru nanoparticle catalyst, and has the benefit of easy wax/catalyst slurry separation by filtration. The hydrogen reduced supported Ru catalyst exhibited superior selectivity towards hydrocarbons (higher C5+ selectivity and lower selectivity to methane) than all other catalysts tested.

The goal of this work is to explore the ability of the metal-promoted 25%Co/Al 2 O 3 catalyst to maintain good contact between the metal and cobalt and continue facilitating Co oxide reduction after simulated regeneration cycles through oxidation–reduction treatments, an approach designed to simulate the catalyst regeneration process. Unpromoted 25%Co/Al 2 O 3 catalyst was also subjected to treatments and served as a reference. Seven metal promoters were examined in this work, including Pt, Ru, Re, Ag, Au, Rh, and Ir. Fresh and treated catalysts were evaluated by both TPR and XANES spectroscopy, the latter approach utilizing linear combination fittings with appropriate reference compounds. With the unpromoted catalyst, oxidation–reduction cycles tended to have two effects: (1) a fraction of CoO species that lost their interaction with the support emerged and (2) a fraction of more strongly interacting CoO species was formed. A comparison between the freshly calcined sample and samples subjected to simulated regeneration cycles was demonstrated. Pt-, Ru-, Re-, Ag-, and Rh-promoted 25%Co/Al 2 O 3 catalysts maintained their ability to facilitate Co oxide reduction after undergoing oxidation–reduction cycles even up to 3 cycles, while with Ir- and, especially, Au-25%Co/Al 2 O 3 some losses were observed, suggesting some separation between the promoter and cobalt occurred following the treatment cycles. TPR profiles also suggest that some separation of Ru from Co occurs with simulated regeneration cycles, although it does not impact the extent of reduction of Co after three cycles.

The effects of 1% of Cd, In and Sn additives on the physicochemical properties and Fischer-Tropsch synthesis (FTS) performance of a 15% Co/Al2O3 catalyst were investigated. The fresh and spent catalysts were characterized by BET, temperature programmed reduction (TPR), H2-chemisorption, NH3 temperature programmed desorption (TPD), X-ray absorption near edge spectroscopy (XANES), and X ray diffraction (XRD). The catalysts were tested in a 1 L continuously stirred tank reactor (CSTR) at 220 &deg, C, 2.2 MPa, H2/CO = 2.1 and 20&ndash, 55% CO conversion. Addition of 1% of Cd or In enhanced the reduction degree of 15%Co/Al2O3 by ~20%, while addition of 1% Sn slightly hindered it. All three additives adversely impacted Co dispersion by 22&ndash, 32% by increasing apparent Co cluster size based on the H2-chemisorption measurements. However, the decreased Co active site density resulting from the additives did not result in a corresponding activity loss, instead, the additives decreased the activity of the Co catalysts to a much greater extent than expected, i.e., 82&ndash, 93%. The additional detrimental effect on catalyst activity likely indicates that the Cd, In and Sn additives migrated to and covered active sites during reaction and/or provided an electronic effect. XANES results showed that oxides of the additives were present during the reaction, but that a fraction of metal was also likely present based on the TPR and reaction testing results. This is in contrast to typical promoters that become metallic at or below ~350 &deg, C, such as noble metal promoters (e.g., Pt, Ru) and Group 11 promoters (e.g., Ag, Au) on Co catalysts in earlier studies. In the current work, all three additives remarkably increased CH4 and CO2 selectivities and decreased C5+ selectivity, with the Sn and In additives having a greater effect. Interestingly, the Cd, In, or Sn additives were found to influence hydrogenation and isomerization activities. At a similar conversion level (i.e., in the range of 40&ndash, 50%), the additives significantly increased 2-C4 olefin content from 3.8 to 10.6% and n-C4 paraffin from 50 to 61% accompanied by decreases in 1-C4 olefin content from 48 to 30%. The Sn contributed the greatest impact on the secondary reactions of 1-olefins, followed by the In and Cd. NH3-TPD results suggest enhanced acid sites on cobalt catalysts resulting from the additives, which likely explains the change in selectivities for the different catalysts.

Palladium catalyzed intramolecular Sonogashira and Heck coupling reactions have been applied for diversity-oriented synthesis of sulfur containing carbohydrate based medium sized ring macrocycles. The process involves design and synthesis of building blocks with predisposed functional units prerequisite for C–C coupling. Both cis- and trans-fused benzannulated medium sized macrocyles with different ring sizes (8–13-membered) fused at different positions of furannose and pyranose moiety have been achieved.

Palladium catalysed ligand free direct dehydrogenative C-3 alkenylation of pyrones and unprotected pyridones from unactivated alkenes is reported. The process is highly regio- and chemoselective. A wide variety of alkene partners reacted to broaden the substrate scope of the process. The effect of the C-3 substituent on the rate of reaction is also studied.

Hydrogenation of carbon monoxide was investigated for cobalt carbide synthesized from Co3O4 by CO carburization in a fixed-bed reactor. The cobalt carbide synthesized was characterized by BET surface area, X-ray diffraction, scanning electron microscopy, X-ray absorption near edge spectroscopy, and extended X-ray absorption fine structure spectroscopy. The catalysts were tested in the slurry phase using a continuously stirred tank reactor at P = 2.0 MPa, H2/CO = 2:1 in the temperature range of 493–523 K, and with space velocities varying from 1 to 3 Nl h–1 gcat–1. The results strongly suggest that a fraction of cobalt converts to a form with greater metallic character under the conditions employed. This was more pronounced on a Fischer–Tropsch synthesis run conducted at a higher temperature (523 versus 493 K).

Coniuga et impera: A bifunctional solid catalyst is prepared by combining acid and base functions on mesoporous silica supports (see picture). The co-existence of these functions is shown by a two-step reaction sequence in one pot. Excellent product yields, which cannot be obtained by separated acid and base functions in one pot, show the validity of our concept.

The effect of CO conversion on hydrocarbon selectivities (i.e., CH4, C5+, olefin and paraffin), H2/CO usage ratios, CO2 selectivity, and catalyst stability over a wide range of CO conversion (12–94%) on 0.27%Ru–25%Co/Al2O3 catalyst was studied under the conditions of 220 °C, 1.5 MPa, H2/CO feed ratio of 2.1 and gas space velocities of 0.3–15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH4, C5+, and CO2 on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH4 selectivity experienced a change in the trend, and began to increase, and CO2 selectivity experienced a rapid increase. H2/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12–94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels.

Dihydropyran and glycals are readily converted to the corresponding trans-2-deoxy-2-haloazide derivatives in excellent yields within a few minutes using NIS/NBS-TMSN3 at rt in the absence of any catalyst. The use of stoichiometric amounts of the reagents under mild experimental conditions together with the simplicity of the reaction protocol is the notable feature of this transformation.

Co/Al 2 O 3 Fischer–Tropsch synthesis catalysts promoted with different quantities of Group 11 metals (Cu, Ag, Au) were characterized and tested. The presence of relatively small quantities of such metals enhanced Co reducibility and, in the cases of Ag and Au, improved the surface Co metal active site densities. EXAFS experiments with the most loaded catalyst samples show that only Co–Co and Me–Me (Me = Cu, Ag and Au) coordination could be observed. This suggests that the greater fraction of the metals form different phases. However, the reduction promoting effect of the Group 11 metal is severely hampered once the catalyst receives a mild passivation treatment following primary reduction. An explanation in terms of promoter segregation during primary reduction is proposed. At lower promoter levels (0.83%Ag and 1.51%Au) and higher Ag levels (2.76%), significant gains in Co active site densities were achieved resulting in improved CO conversion levels relative to the unpromoted catalyst. Moreover, slight decreases in light product (e.g., CH 4 ) selectivity and slight increases in C 5 + selectivity were achieved. At high Au loading (5.05%), however, too much Au was loaded which, although significantly increasing the fraction of Co reduced, blocked Co surface sites and resulted in decreased CO conversion rates. While Cu facilitated Co reduction, the increased fraction of reduced Co did not translate to improved active site densities. It appears that a fraction of Cu tended to cover the rim of Co clusters, resulting in decreases in CO conversion rates and detrimental increases in light product selectivity.

Lewis acid mediated one-pot transformation of D-glucal in the presence of nucleophiles leads to the formation of racemic alpha-substituted alpha-hydroxymethyl furfuryl derivatives, versatile synthons for biologically active molecules. Transformations using O-, S-, C-, and N-nucleophiles could be achieved readily under mild and scalable conditions. Indium triflate proved to be the catalyst of choice in terms of conversion and regioselectivity.

Increasing the Au loading had a significant positive impact on the catalytic activity. The partial reduction of ceria is necessary for generating bridging OH groups on the surface of ceria, which serve as the active sites. The surface shell reduction process in H2 was monitored by TPR, XANES, and in situ DRIFTS spectroscopy. Either the oxygen deficiencies are first formed, followed by dissociative adsorption of H2O to generate the Type II bridging OH groups or, they may be formed directly by spillover of dissociated H2 from the metal to the ceria surface. For each pair of bridging OH groups formed, two cerium atoms in the surface shell change from the Ce4+ to Ce3+ oxidation state. Addition of Au facilitates the surface reduction process and thereby decreases the reduction temperature from 450 °C for the unpromoted catalyst to 100 °C for the 5% Au/ceria catalyst. A systematic decrease in the required temperature for ceria surface shell reduction was observed by increasing the Au promoter loading as follows: 0.1, 0.25, 0.5, 1, 2.5, 5%. Gold and platinum promoted catalysts were compared in a suitable reaction temperature range after first ensuring that metal–oxide interactions were overcome (ca. 5% metal loading). Approximately 20 times the amount of 5% Au/ceria catalyst was required to achieve a lightoff curve similar to that of a 5% Pt/ceria in the temperature range 200–300 °C, and 5% Pt/ceria also exhibited higher steady-state activity (about double that of Au) at 175 °C. This result suggests that, in addition to the role the metal plays in facilitating the formation of the active site bridging OH groups, it also influences the intrinsic rate of the WGS reaction. Transient formate decomposition experiments carried out at 140 °C indicated that the rate of formate decomposition was approximately 20 times higher for 2.5% Pt/ceria than that of 2.5% Au/ceria, suggesting that the metal (in addition to the promoting effect of H2O previously reported) plays a role in facilitating the decomposition of surface formate intermediates, the proposed rate limiting step of the reaction mechanism.

In this investigation, isotope switching from H2O to D2O was used to validate the possibility that the decomposition of formate could be the rate limiting step for the water gas shift mechanism over metal promoted ceria, as was proposed earlier by Shido and Iwasawa. The surface species were followed stepwise by in-situ DRIFTS, while the conversion was monitored by GC to quantify the conversions. A normal kinetic isotope effect was observed, consistent with a link between the activation energy barrier of the rate limiting step and the breaking of the formate C–H bond.

Anomeric gem-diallylation, mono-β-crotylation and mono-β-propargylation of sugar 1,5 and 1,4 lactones have been achieved under Barbier reaction conditions using Zn powder and a catalytic amount of TMSCl as an activator. Ring closing olefin metathesis of the synthesized gem-diallyl derivatives furnished C-spiro cyclopentene glycosides. Finally, the cyclopentene rings were converted into carbohydrate based tricyclic morpholine fused triazole glycoconjugates as potential SGLT2 inhibitors.

A highly stereoselective rapid C-glycosylation reaction has been developed between glycal and unactivated alkynes in the presence of coppertriflate and ascorbic acid at low catalyst loading and at room temperature. A wide variety of glycals and aryl acetylenes participate in the reaction smoothly. TfOH generated during the reduction of Cu(OTf)2 by ascorbic acid may be the active catalyst for the glycosylation.

The advantages of the title reaction are a high regioselectivity, the use of a broad range of substrates and a mild, inexpensive, and nontoxic catalyst, functional-group tolerance, mild reaction conditions, scalability (20 g), easy handling, and a wide application range.

Controlling active sites of metal-free catalysts is an important strategy to enhance activity of the oxygen evolution reaction (OER). Many attempts have been made to develop metal-free catalysts, but the lack of understanding of active-sites at the atomic-level has slowed the design of highly active and stable metal-free catalysts. A sequential two-step strategy to dope sulfur into carbon nanotube–graphene nanolobes is developed. This bidoping strategy introduces stable sulfur–carbon active-sites. Fluorescence emission of the sulfur K-edge by X-ray absorption near edge spectroscopy (XANES) and scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) mapping and spectra confirm that increasing the incorporation of heterocyclic sulfur into the carbon ring of CNTs not only enhances OER activity with an overpotential of 350 mV at a current density of 10 mA cm−2, but also retains 100% of stability after 75 h. The bidoped sulfur carbon nanotube–graphene nanolobes behave like the state-of-the-art catalysts for OER but outperform those systems in terms of turnover frequency (TOF) which is two orders of magnitude greater than (20% Ir/C) at 400 mV overpotential with very high mass activity 1000 mA cm−2 at 570 mV. Moreover, the sulfur bidoping strategy shows high catalytic activity for the oxygen reduction reaction (ORR). Stable bifunctional (ORR and OER) catalysts are low cost, and light-weight bidoped sulfur carbon nanotubes are potential candidates for next-generation metal-free regenerative fuel cells.

Novel one-pot three- and four-component transformations of D-glucal to furan-based hydroxy triazole glycoconjugates have been achieved by sequential addition of reagents in the presence of Cu(OTf)(2)-Cu powder as catalysts. In general the carbohydrate-derived products were formed with high diastereomeric purity.

Lewis acid mediated one-pot transformation of d-glucal in the presence of nucleophiles leads to the formation of racemic α-substituted α-hydroxymethyl furfuryl derivatives, versatile synthons for biologically active molecules. Transformations using O-, S-, C-, and N-nucleophiles could be achieved readily under mild and scalable conditions. Indium triflate proved to be the catalyst of choice in terms of conversion and regioselectivity.

Anomeric gem-diallylation, mono-β-crotylation and mono-β-propargylation of sugar 1,5 and 1,4 lactones have been achieved under Barbier reaction conditions using Zn powder and a catalytic amount of TMSCl as an activator. Ring closing olefin metathesis of the synthesized gem-diallyl derivatives furnished C-spiro cyclopentene glycosides. Finally, the cyclopentene rings were converted into carbohydrate based tricyclic morpholine fused triazole glycoconjugates as potential SGLT2 inhibitors.

A highly stereoselective rapid C-glycosylation reaction has been developed between glycal and unactivated alkynes in the presence of coppertriflate and ascorbic acid at low catalyst loading and at room temperature. A wide variety of glycals and aryl acetylenes participate in the reaction smoothly. TfOH generated during the reduction of Cu(OTf)2 by ascorbic acid may be the active catalyst for the glycosylation.

A fast, solvent-free solid acid mediated synthetic strategy for the synthesis of bisindolylmethanes has been developed. The process is applicable to a wide range of substrates with different protecting group survival properties. Reusability of Fe/Al pillared clay for more than 5 cycles without significant loss of catalytic activity adds to the features of the reaction.

A novel in situ time-resolved synchrotron X-ray absorption spectroscopy (XAS) was introduced for the dynamic studies during fast chemical and electrochemical delithiation of LiFePO(4). The lithium diffusion in LiFePO(4) and the reaction mechanisms for both processes were investigated. This approach opens new opportunities for dynamic studies of various energy storage systems.

Cu–Mn spinel oxide catalyst has been investigated for the ligand-free Huisgen [3+2] cycloaddition. The copper(I) species required in the cycloaddition reaction has been stabilized in the tetrahedral site of the spinel without the need of a stabilizing agent. The new catalyst is robust and can be reused several times under MW conditions with negligible loss in catalytic activity.