Effect of Phosphorus Precursor, Reduction Temperature, and Support on the Catalytic Properties of Nickel Phosphide Catalysts in Continuous-Flow Reductive Amination of Ethyl Levulinate

Organic synthesis in flow mode by selective liquid-phase hydrogenation over heterogeneous non-noble metal catalysts

Flow hydrogenation performed over heterogeneous catalysts makes organic synthesis more economical, safe and environmentally friendly. Over the past two decades, a significant amount of research with a major focus on noble metal catalysts has been carried out in this area. However, catalysts based on non-noble metals (Ni, Cu, Co, etc.) are more promising for practical use due to their low cost and high availability. This review article discusses the use of supported and bulk non-noble metal catalysts for the liquid-phase hydrogenation of bi- and polyfunctional organic compounds in flow mode. The main attention is paid to the selective reduction of one functional group (NO2, CC, CN, CO, and CN) in the presence of other substituents. In addition, cascade synthetic protocols involving hydrogenation are presented.

Reductive N-Alkylation of Amines with Ketones Using Heterogeneous Polysilane-Palladium Catalysts under Continuous-Flow Conditions

This work reports a continuous-flow reductive N-alkylation of amines with ketones using molecular hydrogen. The reaction, performed with highly active polysilane-modified heterogeneous palladium catalysts, enables the efficient synthesis of diversely substituted amines under mild flow conditions. The developed catalyst exhibits sustained activity for 5 days (turnover number of >2400). Moreover, the utility of the method is demonstrated by the synthesis of a key intermediate of the active pharmaceutical ingredient teneligliptin.

Reductive Amination of Levulinic Acid to Pyrrolidones: Key Step in Biomass Valorization towards Nitrogen-Containing Chemicals

Nowadays, the field of biomass conversion is gradually moving towards an encouraging stage. The preparation of nitrogen-containing chemicals using various biomass resources instead of fossil resources do not only reduce carbon emissions, but also diversify the products of biomass conversion, thus increasing the economic competitiveness of biomass refining systems. Levulinic acid (LA) can be used as a promising intermediate in biomass conversion for further synthesis of pyrrolidone via reductive amination. However, there are still many critical issues to be solved. Particularly, the specific effects of catalysts on the performance of LA reductive amination have not been sufficiently revealed, and the potential impacts of key conditional factors have not been clearly elucidated. In view of this, this review attempts to provide theoretical insights through an in-depth interpretation of the above key issues. The contribution of catalysts to the reductive amination of LA as well as the catalyst structural preferences for improving catalytic performance are discussed. In addition, the role of key conditional factors is discussed. The insights presented in this review will contribute to the design of catalyst nanostructures and the rational configuration of green reaction conditions, which may provide inspiration to facilitate the nitrogen-related transformation of more biomass platform molecules.

Conversion of Levulinic Acid and its Esters to 1,5-dimethyl-2-Pyrrolidone over a Nonnoble Metallic Ni@CeOx Catalyst

1,5-dimethyl-2-pyrrolidone (MNMP), as a highly efficient green solvent, can be obtained from biomass-derived levulinic acid and its esters with 100 % conversion and 96.8 % yield over a 10 % Ni@CeOx catalyst at 140 °C, 2 MPa H2 , 8 h, and with water as the solvent. Structure-property correlation investigations were performed with diverse characterization methods, including BET, XRD, XPS, TEM, HAADF-STEM, H2 -TPR, NH3 -TPD, CO2 -TPD and FT-IR, and the results revealed that the excellent catalytic performance of the 10 % Ni@CeOx catalyst was mainly resulted from the strong interaction between Ni and CeOx, which formed more catalytic active sites and contributed to higher reductive amination efficiency. Besides, the 10 % Ni@CeOx catalyst had a chemisorption effect on LA. This was also the key to the excellent catalytic activity of the 10 % Ni@CeOx catalyst. The 10 % Ni@CeOx catalyst exhibited great stability throughout 6 reaction runs and excellent catalytic efficiency in the kilogram scale preparation of MNMP. This work provides a low-cost, efficient, and environmentally friendly heterogeneous catalytic system for the production of MNMP.

Transition Metal Phosphide Nanoarchitectonics for Versatile Organic Catalysis

Transition metal phosphides (TMP) posses unique physiochemical, geometrical, and electronic properties, which can be exploited for different catalytic applications, such as photocatalysis, electrocatalysis, organic catalysis, etc. Among others, the use of TMP for organic catalysis is less explored and still facing many complex challenges, which necessitate the development of sustainable catalytic reaction protocols demonstrating high selectivity and yield of the desired molecules of high significance. In this regard, the controlled synthesis of TMP-based catalysts and thorough investigations of underlying reaction mechanisms can provide deeper insights toward practical achievement of desired applications. This review aims at providing a comprehensive analysis on the recent advancements in the synthetic strategies for the tailored and tunable engineering of structural, geometrical, and electronic properties of TMP. In addition, their unprecedented catalytic potential toward different organic transformation reactions is succinctly summarized and critically analyzed. Finally, a rational perspective on future opportunities and challenges in the emerging field of organic catalysis is provided. On the account of the recent achievements accomplished in organic synthesis using TMP, it is highly anticipated that the use of TMP combined with advanced innovative technologies and methodologies can pave the way toward large scale realization of organic catalysis.

Hydrodeoxygenation–Isomerization of Methyl Palmitate over SAPO-11-Supported Ni-Phosphide Catalysts

Ni-phosphide catalysts on SAPO-11 were studied in the hydrodeoxygenation–isomerization of methyl palmitate (C15H31COOCH3—MP). The catalysts were synthesized using temperature-programmed reduction (TPR) of a phosphate precursor ((NH4)2HPO4 and Ni(CH3CH2COO)2), TPR of a phosphite precursor (H3PO3 and Ni(OH)2), and using phosphidation of Ni/SAPO-11 by PPh3 in the liquid phase. The samples were characterized by ICP-AES chemical analysis, N2 physisorption, NH3-TPD, XRD, and TEM. First, the screening of the catalysts prepared by the TPR method was carried out in a semi-batch autoclave to determine the influence of the preparation method and conditions on one-pot HDO–isomerization (290–380 °C, 2–3 MPa). The precursor’s nature and the amount of phosphorus strongly influenced the activity of the catalysts and their surface area and acidity. Isomerization occurred only at a low P content (Ni/P = 2/1) and blocking of the SAPO-11 channels by unreduced phosphates at higher P contents did not allow us to obtain iso-alkanes. Experiments with liquid phosphidation samples in a continuous-flow reactor also showed the strong dependence of activity on phosphidation duration as well as on Ni content. The highest yield of isomerized products (66% iso-C15–16 hydrocarbons, at complete conversion of O-containing compounds, 340 °C, 2 MPa, and LHSV = 5.3 h−1) was obtained over 7% Ni2P/SAPO-11 prepared by the liquid phosphidation method.