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1. Olefin methylation over iron zeolites and the methanol to hydrocarbons reaction

   https://doi.org/10.1016/j.apcata.2022.118645  

   LaFollette, Mark R; Lobo, Raul F (July 2022, Applied Catalysis A: General)

   The effect of olefin addition to a stream of dimethyl ether on the methanol homologation reaction is investigated using iron-substituted zeolites Fe-beta and Fe-ZSM-5. The reaction was investigated using plug-flow microreactors in the temperature range of 240-400 degrees C, at a total pressure of 0.239 MPa and a WHSV of 6.12 (g DME/ gcat-hr). For Fe-beta (Si/Fe= 9.2) catalysts, isobutene co-feeding almost doubles dimethyl ether (DME) consumption rate and shifts selectivity towards larger olefins with carbon numbers from 5 to 7. Addition of isobutene above 6.3%, however, resulted in a reduction of DME consumption rates, an effect assigned to the replacement of surface methoxy groups for adsorbed olefins in the zeolite pores. Below a temperature of 340 degrees C hydride-transfer rates are negligible; reaction rates are stable for over 5.5 h and the products consist almost exclusively of olefins and a small amount of methane. Above 360 degrees C the onset of catalytic hydride transfer processes is observed leading to fast catalyst deactivation rates and an increase in the concentration of aromatic species. Iron ZSM-5 (Si/Fe = 21.4) catalysts under similar reaction conditions consumes methanol faster than Febeta at approximately three times the TOF (on a per iron basis). The Fe-ZSM-5 catalyst was selective to a distribution of products (C5 to C8) as compared to Fe-beta which was selective to primarily C5 and C7. Co-feeding larger olefins (2-methyl-2-butene, 2,3-dimethyl-2-butene, 2,3,3-trimethyl-1-butene, and 2,4,4-trimethyl-2-pentene) at a 3.9% olefin concentration over Fe-beta changed selectivity towards cracking products (C4 compounds such as isobutene). As the size of the olefin increases, a reduction of DME consumption rate is also observed. These results show that co-feeding olefins with DME over Fe-zeolites is a promising route to increase methylation rates at relatively low temperatures producing larger branched olefins and that the product distribution is highly dependent on the zeolite pore size and structure of the olefin. 

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2. Catalytic performance and stability of Fe-doped CeO ₂ in propane oxidative dehydrogenation using carbon dioxide as an oxidant

   https://doi.org/10.1039/D0CY00586J  

   Wang, Hedun; Tsilomelekis, George (July 2020, Catalysis Science & Technology)

   Propane oxidative dehydrogenation (ODH) in the presence of CO 2 was investigated over a series of Fe-doped CeO 2 catalysts. The well-recognized properties of cerium oxide materials regarding improved oxygen mobility and oxygen storage capacity (OSC) were utilized towards the synthesis of stable catalytic systems. The iron–cerium oxide solid solution catalysts with an Fe dopant content from 1% up to 15% were successfully synthesized via a co-precipitation method and calcined at 873 K. It was confirmed by XRD and Raman characterization that all samples featured a single cerianite crystalline phase with periodic lattice Ce ions substituted by Fe ions, with no hematite phase identified. Initial screening of catalytic behavior showed that the propane ODH pathway was enhanced at high Fe/Ce ratio while propane cracking was suppressed. Stable propane conversion and propylene selectivity for up to 20 hours were achieved for the synthesized catalysts with moderate Fe loading. Ex situ Raman, XPS and STEM were applied to analyze post-reaction catalysts and confirmed that deactivation occurring over low Fe catalysts resulted from coke deposition on the surface, while CeO 2 sintering and Fe migration to form nanocrystals were the primary deactivation reasons for high Fe loading catalysts. 

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3. Graphene oxide catalyzed ketone α-alkylation with alkenes: enhancement of graphene oxide activity by hydrogen bonding

   https://doi.org/10.1039/c9cc02578b  

   Meng, Guangrong; Patel, Mehulkumar; Luo, Feixiang; Li, Qingdong; Flach, Carol; Mendelsohn, Richard; Garfunkel, Eric; He, Huixin; Szostak, Michal (May 2019, Chemical Communications)

   Direct α-alkylation of carbonyl compounds represents a fundamental bond forming transformation in organic synthesis. We report the first ketone-alkylation using olefins and alcohols as simple alkylating agents catalyzed by graphene oxide. Extensive studies of the graphene surface suggest a pathway involving dual activation of both coupling partners. Notably, we show that polar functional groups have a stabilizing effect on the GO surface, which results in a net enhancement of the catalytic activity. The method represents the first alkylation of carbonyl compounds using graphenes, which opens the door for the development of an array of protocols for ketone functionalization employing common carbonyl building blocks and readily available graphenes. 

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4. Transition-metal-catalyzed decarbonylation of carboxylic acids to olefins: exploiting acyl C–O activation for the production of high value products

   https://doi.org/10.1039/C8QO00585K  

   Zhang, Xu; Jordan, Frank; Szostak, Michal (January 2018, Organic Chemistry Frontiers)

   Transition-metal-catalyzed decarbonylation reactions of aliphatic carboxylic acids produce olefins via one carbon degradation. Recently, tremendous progress has been made in the development of new protocols for the synthesis of linear olefins by the formal acyl C–O activation mechanism of ubiquitous carboxylic acids. Various transition metals including nickel, palladium, iridium and iron have been shown to catalyze the reaction and achieve excellent yields and selectivity. The use of new ligand systems has resulted in unprecedented control of selectivity of elementary steps in the catalytic cycle. The development of new acyl precursors expands the access to α-olefins and offers promising perspectives for applications in preparative organic synthesis. In this article, we highlight the recent noteworthy developments in the transition-metal-catalyzed decarbonylation of carboxylic acids and discuss future challenges in this field. 

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5. Design of highly selective ethanol dehydration nanocatalysts for ethylene production

   https://doi.org/10.1039/C7NR08678D  

   Austin, Natalie; Kostetskyy, Pavlo; Mpourmpakis, Giannis (January 2018, Nanoscale)

   Rational design of catalysts for selective conversion of alcohols to olefins is key since product selectivity remains an issue due to competing etherification reactions. Using first principles calculations and chemical rules, we designed novel metal–oxide-protected metal nanoclusters (M 13 X 4 O 12 , with M = Cu, Ag, and Au and X = Al, Ga, and In) exhibiting strong Lewis acid sites on their surface, active for the selective formation of olefins from alcohols. These symmetrical nanocatalysts, due to their curvature, show unfavorable etherification chemistries, while favoring the olefin production. Furthermore, we determined that water removal and regeneration of the nanocatalysts is more feasible compared to the equivalent strong acid sites on solid acids used for alcohol dehydration. Our results demonstrate an exceptional stability of these new nanostructures with the most energetically favorable being Cu-based. Thus, the high selectivity and stability of these in-silico-predicted novel nanoclusters ( e.g. Cu 13 Al 4 O 12 ) make them attractive catalysts for the selective dehydration of alcohols to olefins. 

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