Confinements on growth sites are recognized as essential principle of Fischer-Tropsch synthesis. Chain branching is sensitive against chain size. Similarities between FT-growth-sites and homogeneous pincer-complex catalysts are realized. In house developed methods for time resolved investigation of activity and selectivity are applied. An advanced ASF-model is defined, and on this basis probabilities of branching are calculated from experimental product distributions. Chain-length dependence in branching is quantified as branching pattern. Confinements on branching are studied for iron- and cobalt catalyst at varied CO partial pressure and during catalyst restructuring. With cobalt, FT-growth sites are observed as of dynamic nature, CO being involved. With iron, growth sites are stable, even during catalyst carbiding. The basic parameter to constitute a FT-growth site, be it on iron or cobalt, are specific confinements, regardless of differences in chemical or structural nature. Results and discussion of this work are aiming at disclosing the miracle of “gasoline synthesis from CO + H2 at normal pressure”, invented by Franz Fischer and Hans Tropsch, as the methylene insertion on homogeneous-complex-alike sites on the catalyst surface.

Time- and space resolved selectivity in methanol conversion on zeolites has been investigated and exploited for insight about the reaction mechanism. Particular focus is directed to constraints on diffusion and reaction provided by the pore structure. 3 zeolites with well-ordered voids and channels of different size have been used comparatively. Novel experimental tools have been developed. Product composition is normalized, providing a deactivation pattern, which reflects the reaction mechanism, as changing with time and characterizing essential constraints. The higher product complexity, the more information is present about the mechanism. But in methanol conversion on zeolites, there are difficulties in making use this wealth of information—selectivity meaning a mixture of many compounds, ranging from gases to liquids and substances retained on the catalyst. As catalysts, zeolites with 8-, 10- and 12-ring channels and distinct void’s size have been used in a specifically designed fixed bed reactor, applying ampoule product sampling and advanced chromatography. On catalyst retained substances are taken in account and deactivation is elucidated profoundly. Progress about the mechanism of hydrocarbon formation concerns autocatalysis, constraints with zeolite topologies and changes with time when “C-Retained” accumulates in the pores or on surface of the zeolite crystallites. A surprising reanimation regime with zeolite HZSM5 has been observed and disclosed as thermodynamically controlled arene alkylation with olefins. At low temperature with HZSM5, a different reaction mechanism—as compared with application at high temperature—is noticed, with regimes of incubation, acceleration, and deactivation—at short catalyst live time. The novel experimental techniques allow revealing chemistry in the migrating reaction zone—and in the zones of deactivated catalyst behind, and of fresh catalyst in front. Comparing the results with the 3 zeolite topologies provides insight about controlling constraints.

Nico Fischer opened discussion of the paper by Ding Ma: After the ethylene treatment of your model catalyst, do you observe any cobalt carbide formation? Ding Ma answered: No, we did not observe the formation of cobalt carbide in its XRD pattern. Hans Niemantsverdr

Wolf, M o ri tz a n d v a n H e e r d e n , Tr a c ey 2 0 1 7. C a t aly sis fo r fu els: g e n e r al di s c u s sio n.F a r a d a y Dis c u s sio n s 1 9 7 , p p . 1 6 5-2 0 5. 1 0.

Stephen McCord opened a general discussion of the paper by Avelino Corma: A key phase of your process is the pyrolysis of biomass. Did you investigate the impact of varying the heating rate applied to the biomass during pyrolysis? It has been previously reported that high heating rates have res

Nitrogen-doped carbon nanotubes (NCNTs) were used as a support for iron (Fe) nanoparticles applied in carbon dioxide (CO2) hydrogenation at 633K and 25 bar (1 bar = 105 Pa). The Fe/NCNT catalyst promoted with both potassium (K) and manganese (Mn) showed high performance in CO2 hydrogenation, reaching 34.9% conversion with a gas hourly space velocity (GHSV) of 3.1L·(g·h)−1. Product selectivities were high for olefin products and low for short-chain alkanes for the K-promoted catalysts. When Fe/NCNT catalyst was promoted with both K and Mn, the catalytic activity was stable for 60h of reaction time. The structural effect of the Mn promoter was demonstrated by X-ray diffraction (XRD), temperature-programmed reduction (TPR) with molecular hydrogen (H2), and in situ X-ray absorption near-edge structure (XANES) analysis. The Mn promoter stabilized wüstite (FeO) as an intermediate and lowered the TPR onset temperature. Catalytic ammonia (NH3) decomposition was used as an additional probe reaction for characterizing the promoter effects. The Fe/NCNT catalyst promoted with both K and Mn had the highest catalytic activity, and the Mn-promoted Fe/NCNT catalysts had the highest thermal stability under reducing conditions.

An iron based catalyst supported on an N-functionalized carbon nanotube (NCNT) was promoted with potassium and manganese as follows: Fe/NCNT, K/Fe/NCNT, Mn/Fe/NCNT, and K/Mn/Fe/NCNT for CO2 hydrogenation. Time-resolved reduction X-ray absorption near edge spectroscopy (XANES) showed mixed phases of Fe, FeO, Fe2O3, and Fe2O3 resulting from K/Fe/NCNT, and of FeO and Fe2O3 resulting from Mn/Fe/NCNT. The product distributions and growth probability of n-alkanes during CO2 hydrogenation indicated that the potassium-promoted iron catalysts performed Fischer-Tropsch (FT) synthesis under steady state at 60 h. 1-Alkenes desorbed from the FT sites with the potassium-promoted catalysts, (K/Fe/NCNT and K/Mn/Fe/NCNT), with low methane formation. Small amounts of 1-alkene, along with high methanation, were produced from the potassium-unpromoted catalysts, (Fe/NCNT and Mn/Fe/NCNT), indicating high local H-2:CO ratios on the catalyst surfaces. K/Fe/NCNT and K/Mn/Fe/NCNT catalysts also produced ethanol. Thus, potassium is a key promoter providing active species of the catalysts for alkene and ethanol formation. Reduced surrounding of the NCNT support, potassium as an electronic promoter together with manganese as a structural promoter made the iron-active phase well suitable for CO2 hydrogenation producing mainly alkenes and ethanol. (C) 2016 Elsevier B.V. All rights reserved.

Large reserves of natural gas are causing high actual interest for olefins and automotive fuels via methanol conversion on zeolite HZSM5. The chemistry of this process involves spatial constraints in the zeolite pores and a set of reacting compounds hosted dynamically in the pores. The kinetic scheme of reactions in this pool regime is a matter of current debate––a problem being the complexity of product composition and its temporal changes. However, the multi-compound product composition, if measured accurately and even time-resolved––including the compounds retained in/on the catalyst––is a profound source of information. Methanol conversion has been studied with zeolite HZSM5 and zeolite HY accordingly. The pool mechanism has been developed further, specifically as depending on frustration for distinct reactions. Particular pools as for olefins or for gasoline are specified. Mechanism changes with reaction time and with reaction temperature are described, including the surprising phenomenon of reanimation and the mechanisms of catalyst deactivation.

•Selforganization in Fischer–Tropsch synthesis on iron and cobalt catalysts.•Mechanism of alkali promoting of iron catalysts.•Time resolved selectivity, chain growth and branching.•Primary and secondary olefin selectivity.•Spatial constraints on growth sites.

Co/SiO2 catalysts were promoted with 4% and 8% ZrO2. Small amounts (0.07%) of Ru were impregnated onto 4%ZrO2/Co/SiO2. Catalysts resulting from time-resolved XANES reduction showed mixed phases of Co and CoO, with the highest percentages of Co resulting from Ru/4%ZrO2/Co/SiO2 and the highest percentages of CoO resulting from 8%ZrO2/Co/SiO2. Product distributions of n-alkanes, iso-alkanes and alkenes during Fischer-Tropsch Synthesis (FTS) were used to investigate the catalyst performance of 4%ZrO2/Co/SiO2 8%ZrO2/Co/SiO2 and Ru/4%ZrO2/Co/SiO2. FTS steady state was studied by growth probabilities of n-alkane products. No 1-alkene was produced from Ru/4%ZrO2/Co/SiO2, indicating high availability of Fischer-Tropsch sites for long chain hydrocarbon growth, despite high methanation. Branched alkanes produced from the secondary reaction were related to the high CoO percentages on 8%ZrO2/Co/SiO2. Alkene readsorption sites were high, corresponding to the high CoO percentages, causing a high probability of forming branched alkane products. (c) 2014 Elsevier B.V. All rights reserved.

Fischer-Tropsch synthesis has been performed with iron- and cobalt catalysts at varied conditions, and selectivity determined for steady state and the initial time of selforganization. Product composition has been analyzed in detail with high temporal resolution. Using the kinetic model of non-trivial surface polymerization, information about elemental reactions and their role in the reaction mechanism has been attained.Among the ruling principles, distinct constraints appear to be essential, as frustration of methanation, of desorption of chains in relation to their prolongation and of paraffin formation in relation to olefin desorption. Spatial constraints on the growth sites appear to control linear growth in relation to chain branching and also branching probability in dependence of chain length.With cobalt, selectivity and respectively the structure of active sites appear to be dynamic, to develop under reaction conditions and to respond to changes of conditions. With carbided iron, selectivity and respectively active sites appear to be of static nature. Information about secondary olefin reactions is also obtained as important for producing olefins through Fischer-Tropsch synthesis. (C) 2013 Elsevier B.V. All rights reserved.

Selectivity in petroleum chemistry generally means multi-compound product compositions, distributed over a wide range from, e.g. hydrocarbon gases up to vapors of high boiling substances – thus providing analytical problems. Temporal resolution is required for investigating unsteady regimes of reaction, as pertinent during self-organization of catalytic processes or phenomena of catalyst deactivation. It is also of interest in temperature programmed operation as for catalyst regeneration, pyrolysis of organic materials as oil shale and biomass or TPD of pollutants recovered on adsorbents. For temporal resolution instant ampoule sampling has been developed. Ampoule samples are taken from the (hot) gaseous product flow in pre-evacuated glass ampoules in less than 1s and stored without compositional changes for later GC-analysis. High resolution gas chromatography has been developed, starting at −80°C for the separation of light gases and ending at, e.g. 250°C for separating high boiling compounds (e.g. vapors of hydrocarbons C20). In the article, initial selectivity changes in Fischer–Tropsch synthesis (referring to chain growth, chain branching and olefin reactions, as caused by self-organization of the FT-regime) and also thermal regeneration of a HZSM5 catalyst used for methanol conversion at low temperature (referring to reactivation by de-alkylation of bulky benzene derivates) are being presented.

Un-promoted and promoted Co/SiO2 catalysts with ZrO2 and Ru were prepared and the catalytic performances for Fischer-Tropsch synthesis were investigated. The prepared catalysts were characterized by XRD, N2 adsorption/desorption, and X-ray absorption techniques. XRD suggested that the cobalt species presence in all prepared catalysts was Co3O4. Promoted catalyst with ZrO2 and Ru showed high distribution of cobalt on silica surface resulted in smaller Co3O4 crystalline size than un-promoted ones. From the reaction testing, the obtained products of C1 to C9 from un-promoted and promoted Co/SiO2 were studied.

Deactivation of acidic zeolite catalysts during methanol conversion is investigated for elucidating how spatial constraints interfere mechanistically. Detailed product composition - including retained organic matter - is determined in a time resolved mode.At 270-300 degrees C with H-ZSM-5, first unsaturated hydrocarbons are formed-methane being the indicative co-product. Then the reaction rate increases auto-catalytically, but soon declines because of exhaustive pore filling. The retained organic matter consists mainly of ethyl-trimethyl-benzene-and isopropyl-dimethyl-benzene molecules. Alkylation of benzene rings with ethene and propene produces the deactivating molecules.At 475 degrees C, alkylation of benzene rings with olefins has shifted to the reverse, reactivating the H-ZSM-5 catalyst. Coke forms slowly on the surface of H-ZSM-5 crystallites. Spatial constraints suppress the formation of 2-ring aromatics. With the wide pore zeolite H-Y, fast deactivation is noticed-bigger aromatic molecules can be formed and are retained.Methanol reactions on the protonic catalyst sites are visualized as CH3+ attack for methylation and dehydrogenation, methane being the hydrogen-rich co-product. Methanol conversion on zeolites H-ZSM-58, H-EU-1 and H-Beta is comparatively investigated.Zone ageing is discussed for favorable reactor design.It is shown, how a multi-compound product composition is the source of information for elucidating complex reaction mechanisms. (C) 2010 Elsevier B. V. All rights reserved.