Fischer-Tropsch (F-T) based Gas-to-Liquids (GTL) processing is recognized as an industrially proven and economically competitive route to high quality diesel. Furthermore, it is generally accepted that for this purpose, GTL processing is most effective when comprising an F-T synthesis driven to wax production, followed by hydrocracking to produce middle-distillate products. Applying a CoMo/SiO 2 -Al 2 O 3 catalyst, optimised for hydrocracking crude oil refinery feedstocks in a sulphur-containing environment, to the processing of a linear paraffin F-T wax model compound, n-tetradecane, shows that a significant opportunity exists for utilisation of base metal catalyst, having the advantage of producing less branched hydrocracking products, i.e. high cetane number diesel via a hydrogenolytic cracking mechanism. A drawback of such a catalyst, if applied in non-sulphided form and in a non-sulphur containing environment, is the comparably high yield of light gases, in particular methane. It is shown, and proved by a simple kinetic model, that methane is formed via 'methanolysis', i.e. successive hydrogenolytic demethanisation reaction of the feed compounds, presumably of islands of metallic cobalt on the catalyst.

Selective Fischer-Tropsch wax hydrocracking : opportunity for improvement of overall gas-to-liquids processing

One-step hydrotreatment of inedible oil for production the second-generation biofuel over Pt-Sn/SAPO-11 catalyst

Polyolefins, the largest used commodity plastics in the world, find extensive application in many fields. However, most end up in landfills or incineration, leading to severe ecological crises, environmental pollution, and serious resource waste problems. As representatives on chemical upcycling of polyolefin plastics polyolefin waste to fuels and bulk/fine chemicals, polyolefin catalytic cracking and hydrocracking based on zeolite or metal/zeolite composite catalysts are considered the most effective paths due to their large capacity and strong adaptability to existing petrochemical equipment. After an overview of the reaction mechanisms of pyrolysis and catalytic cracking, this review aims to comprehensively discuss the influence of zeolite catalyst structure (acidity, pore structure, and morphology) on the catalytic activity, selectivity, and stability of polyolefin cracking, particularly emphasizing the importance for matching acidity and pore structure for target product formation. Subsequently, the structure–activity relationship between the metal site and zeolite’s acid site in polyolefin hydrocracking is also discussed. In the end, emerging opportunities and challenges are proposed to promote a more efficient way for polyolefin chemical upcycling. 

Understanding the Structure–Activity Relationships in Catalytic Conversion of Polyolefin Plastics by Zeolite-Based Catalysts: A Critical Review

Although being transition metals, the Fenton‐inactive group 3–4 elements (Sc, Y, La, Ti, Zr, and Hf) can easily lose all the outermost s and d electrons, leaving behind ionic sites with nearly empty outermost orbitals that are stable but inactive for oxygen involved catalysis. Here, it is demonstrated that the dynamic coordination network can turn these commonly inactive ionic sites into platinum‐like catalytic centers for the oxygen reduction reaction (ORR). Using density functional theory calculations, a macrocyclic ligand coordinated yttrium single‐atom (YN4) moiety is identified, which is originally ORR inactive because of the too strong binding of hydroxyl intermediate, while it can be activated by an axial ligand X through the covalency competition between YX and YOH bonds. Strikingly, it is also found that the binding force of the axially coordinated ligand is an effective descriptor, and the chlorine ligand is screened out with an optimal binding force that behaves self‐adaptively to facilitate each ORR intermediate steps by dynamically changing its YCl covalency. These experiments validate that the as‐designed YN4‐Cl moieties embedded within the carbon framework exhibit a high half‐wave potential (E1/2 = 0.85 V) in alkaline media, the same as that of the commercial Pt/C catalyst .

Coordination Chemistry of Large‐Sized Yttrium Single‐Atom Catalysts for Oxygen Reduction Reaction

Effect of metal–acid balance and textual modifications on hydroisomerization catalysts for n-alkanes with different chain length: A mini-review

Maximizing the utilization of noble metals is crucial for applications such as catalysis. We found that the minimum loading of platinum for optimal performance in the hydroconversion of n-alkanes for industrially relevant bifunctional catalysts could be reduced by a factor of 10 or more through the rational arranging of functional sites at the nanoscale. Intentionally depositing traces of platinum nanoparticles on the alumina binder or the outer surface of zeolite crystals, instead of inside the zeolite crystals, enhanced isomer selectivity without compromising activity. Separation between platinum and zeolite acid sites preserved the metal and acid functions by limiting micropore blockage by metal clusters and enhancing access to metal sites. Reduced platinum nanoparticles were more active than platinum single atoms strongly bonded to the alumina binder. Description Better on the outside One way to maximize the activity of scarce and costly noble metals in catalysis is to use small cluster or even single atoms on metal oxide supports. Bifunctional platinum and zeolite catalysts are used industrially in alkane hydroconversion. Cheng et al. show that the amount of platinum used could be reduced and isomer selectivity improved when the catalyst preparation created platinum clusters on the surface of zeolite or its alumina binder, rather than in the interior of the zeolite channels. Preparations that would have formed single-atom catalysts were less active because the platinum ions adsorbed on the alumina surface were more difficult to reduce. —PDS Isomer selectivity in alkane hydroconversion improves when platinum clusters are located on rather than in zeolites.

Tegan Roberts

Papers

Maximizing noble metal utilization in solid catalysts by control of nanoparticle location

Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane