A Molecular Analogue of the C−H Activation Intermediate of the Silica-Supported Ga(III) Single-Site Propane Dehydrogenation Catalyst: Structure and XANES Signature

Propane dehydrogenation is an important field of research due to an increasing world-wide demand of propene while classical production routes through naphtha cracking are in decline. In that context, silica-supported Ga(III) sites, synthesized from surface organometallic chemistry principles, show high selectivity and stability in the propane dehydrogenation reaction. This performance is in significant contrast to the reported fast deactivation and lower selectivity of most Ga₂O₃ and CrO₃ based materials. The Ga-catalyzed propane dehydrogenation reaction is proposed to proceed through the formation of Ga alkyl intermediates for which it would be desirable to have detailed structural and spectroscopic information. Here, we prepare a consistent series of Ga(III) molecular complexes with varying numbers of alkyl and siloxide ligands; they are characterized by single crystal X-Ray diffraction and X-Ray Absorption Near Edge Structure analysis, which is known to be highly sensitive to the Ga coordination environment. We report in particular the structure and the spectroscopic signatures of [Ga(ⁱPr)(OSi(O^tBu)₃)₂(HOSi(O^tBu)₃)], a molecular mimic of the key proposed reaction intermediates in the Ga-catalyzed PDH reaction.     

Platinum‐Promoted Ga/Al2O3 as Highly Active,Selective, and Stable Catalyst for the Dehydrogenation of Propane

A novel catalyst material for the selective dehydrogenation of propane is presented. The catalyst consists of 1000 ppm Pt, 3 wt % Ga, and 0.25 wt % K supported on alumina. We observed a synergy between Ga and Pt, resulting in a highly active and stable catalyst. Additionally, we propose a bifunctional active phase, in which coordinately unsaturated Ga³⁺ species are the active species and where Pt functions as a promoter.     

Azaruthena(II)‐bicyclo[3.2.0]heptadiene: Key Intermediate for Ruthenaelectro(II/III/I)‐catalyzed Alkyne Annulations

A ruthenium‐catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N‐fused [5,6]‐bicyclic heteroarenes through regioselective electrochemical C?H/N?H annulation without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.     

Selective Acceptorless Dehydrogenation of Primary Amines to Imines by Core–Shell Cobalt Nanoparticles

Core–shell nanocatalysts are attractive due to their versatility and stability. Here, we describe cobalt nanoparticles encapsulated within graphitic shells prepared via the pyrolysis of a cationic poly‐ionic liquid (PIL) with a cobalt(II) chloride anion. The resulting material has a core–shell structure that displays excellent activity and selectivity in the self‐dehydrogenation and hetero‐dehydrogenation of primary amines to their corresponding imines. Furthermore, the catalyst exhibits excellent activity in the synthesis of secondary imines from substrates with various reducible functional groups (C=C, C≡C and C≡N) and amino acid derivatives.     

Postdiagenetic Changes in Kerogen Properties and Type by Bacterial Oxidation and Dehydrogenation

A significant part of organic carbon found on the earth is deposited as fossil organic matter in the lithosphere. The most important reservoir of carbon is shale rocks enriched with organic matter in the form of kerogen created during diagenesis. The purpose of this study was to analyze whether the bacterial communities currently inhabiting the shale rocks have had any impact on the properties and type of kerogen. We used the shale rock located on the Fore-Sudetic Monocline, which is characterized by oil-prone kerogen type II. We were able to show that shale rock inhabited by bacterial communities are characterized by oxidized and dehydrated kerogen type III (gas-prone) and type IV (nonproductive, residual, and hydrogen-free). Bacterial communities inhabiting shale rock were dominated by heterotrophs of the Proteobacteria, Firmicutes, and Actinobacteria phyla. Additionally, we detected a number of protein sequences in the metaproteomes of bacterial communities matched with enzymes involved in the oxidative metabolism of aliphatic and aromatic hydrocarbons, which may potentially contribute to the postdiagenetic oxidation and dehydrogenation of kerogen. The kerogen transformation contributes to the mobilization of fossil carbon in the form of extractable bitumen dominated by oxidized organic compounds.     

正丁烷脱氢制正丁烯催化剂

综述了对正丁烷脱氢制备正丁烯的催化剂体系,包括有氧脱氢中钒基催化剂、钼酸盐系列和焦磷酸盐系列催化剂;催化脱氢中贵金属Pt系催化剂、以ZSM-5分子筛为载体的催化剂以及膜反应器。探讨了正丁烷脱氢动力学,并在Mars-van Krevlen和 Eley-Rideal机理模型动力学基础上归纳了正丁烷氧化脱氢及直接脱氢的机理。讨论了正丁烷催化剂的影响因素,比较了各类催化剂的特点并对其进行展望,认为ZSM-5分子筛将可能成为正丁烷脱氢制正丁烯的新的研究热点。     

Potassium bromide catalyzed NS bond formation via oxidative dehydrogenation

N-Substituted benzo[d]isothiazol-3(2H)-ones are a family of compounds with extremely important application. Recently, we have developed a new green pathway to synthesize these compounds via potassium bromide-catalyzed intramolecular oxidative dehydrogenative cyclization. This reaction has high functional group tolerance and affords excellent yield even in gram scale.     

Modification of Cr/SiO2 for the dehydrogenation of propane to propylene in carbon dioxide

Summary Dehydrogenation of propane to propylene in carbon dioxide was investigated over promoted Cr/SiO2. The results showed that the catalysts were effective for the reaction and CO2 in the feed promoted the catalytic activity. XRD, TPR and microcalorimetric adsorption techniques were used to study the structure and surface acidity of the catalysts. It was found that the surface acidity decreased with the increase of K in the Cr/SiO2 and led to the increase of selectivity toward propylene. A propane conversion of 31% with 91% selectivity to propylene over the 5%Cr-0.4%K/SiO2 catalyst was observed at 923 K with CO2 /C3H8 molar ratio of 3.6.     

CeO2负载的Cu, Ir和Pd催化剂上的醇转移脱氢反应

 研究了CeO2负载的Cu, Ir和Pd催化剂上的醇转移脱氢反应. 利用催化剂体系脱氢和加氢功能的偶合,在较温和的反应条件下实现了二级脂肪醇的高选择性转移脱氢. 其中, Ir/CeO2催化剂表现出较高的催化活性,其TOF值达16.0 h-1.