A series of granulated Ni/Al2O3 catalysts were prepared by impregnating the γ-alumina support with a nickel (II) ammine complex solution. The study of catalysts at different stages of preparation using IR and UV–Vis spectroscopy, XRD, thermogravimetric analysis, H2-TPR, TPD-CO2 and O2 chemosorption methods made it possible to trace the evolution of the active component. The interaction between the [Ni(NH3)5(H2O)]2+ cations and γ-Al2O3 results in the partial replacement of NH3 ligands with hydroxyl groups of the support, forming inner-sphere complexes between Ni2+ ions and the Al2O3 surface. Drying the catalyst at 140 °C causes the NH3 ligands in the nickel complexes to be replaced by H2O molecules and/or carbonate ligands. The calcination temperature of 300 °C is sufficient for decomposition of the active component precursor to NiO. In the calcined samples, almost all of the nickel oxide is strongly bound to the alumina surface. The highest reducibility was achieved for the samples calcined at 300 °C. Increasing the calcination temperature to 400 °C decreases the reduction rate. It was demonstrated that the reduction of oxide precursors (obtained by calcination at 300–400 °C) in an H2 flow at 400 °C leads to the formation of a highly dispersed nickel phase on the γ-Al2O3 surface. The Ni/Al2O3 catalysts synthesized using nickel ammine complexes show 40

The process of preparing a highly concentrated Ni/Al 2 O 3 catalyst by impregnating γ-Al 2 O 3 with a nickel nitrate solution followed by calcination in a hydrogen-containing atmosphere was studied. Calcination of the supported Ni 3 (OH) 4 (NO 3 ) 2 , which is formed during the heat treatment of the impregnated carrier at 200 °C, in an H 2 environment (H 2 content ≥20%) at 230 °C promotes the formation of a phase of highly dispersed NiO. In this case, nitrate ions are completely removed and there is no enlargement of the active component particles compared to the initial Ni 3 (ОН) 4 (NO 3 ) 2 phase. A decrease in the H 2 concentration in the gas mixture reduces the rate of nitrate decomposition and leads to an agglomeration of the active component particles at an H 2 content of ≤5%. An assumption is made about the role of hydrogen in the process of calcining the catalyst precursor.

Furfuryl alkyl ethers (FAEs) are considered attractive biofuels or gasoline additives. Reductive etherification of bio-based furfural (FF) is a promising method for production of these compounds. In present work, we study the catalytic behavior of Cu-Al mixed oxide in combination with HZSM-5-Al2O3 composites for the syntheses of FAEs in a flow reactor using H2 as a reducing agent. The Cu-based catalyst ensures the hydrogenation of FF to furfuryl alcohol, which then reacted with alcohol in the presence of the acid catalyst. It was found that the reaction of FF with 2-propanol over catalytic system including HZSM-5(Si/Al = 40)-Al2O3 leads to the formation of 2-(isopropoxymethyl)furan (IMF) in excellent yield due to the optimal concentration of strong Bronsted acid sites in the composite. Lower selectivity to IMF was observed in the presence of HZSM-5 with Si/Al ratio of 15, 25 and 140. In addition, the use of primary alcohols instead of 2-PrOH gives a significantly lower yield of FAEs.

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, CC, CN, CO, and CN) in the presence of other substituents. In addition, cascade synthetic protocols involving hydrogenation are presented.

The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using molecular hydrogen as a reducing agent. The reaction was carried out in toluene with a slight excess of amine at a total pressure of 10 bar and a temperature of 140–170°C. With the use of primary aliphatic amines, the 6.3

The effect of diethylene glycol addition on the formation of oxide precursors of nickel–molybdenum sulfide hydrotreating catalysts was studied by Raman spectroscopy and differential dissolution. The NiMoP/Al 2 O 3 catalyst was prepared by impregnation of γ-alumina with an aqueous solution obtained by successive dissolution of H 3 PO 4 , MoO 3 , and Ni(OH) 2 in water. To prepare the NiMoP-diethylene glycol/Al 2 O 3 catalyst, diethylene glycol was added to the impregnation solution. On contact of the impregnation solution with γ-alumina, the H x P 2 Mo 5 O 23 (6− x )− heteropolyanions initially present in the solution decompose to form polymolybdates. Without organic additive, the heptamolybdate anion (Mo 7 O 24 6− ) is formed, whereas the use of diethylene glycol leads to the formation of polymolybdates of different structures, mainly with high degree of polymerization. In contrast to Mo 7 O 24 6− , such polymolybdates are probably incapable of interacting with the support surface to generate aluminum molybdates that do not form the most active “NiMoS” phase.

The catalytic properties of a copper-aluminum oxide catalyst obtained from double layered hydroxide have been studied in hydrogenation of 1,3,5-trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT) in a flow reactor. The reaction was carried out at temperature of 120°C, total pressure of 30 bar and substrate concentration of 0.10–0.15 M, using methanol as a solvent. 1,3,5-Triaminobenzene (TAB) and 2,4,6-triaminotoluene (TAT) were isolated from the reaction mixture in the form of double salts with sulfuric acid TAB⋅2H2SO4 and TAT⋅2H2SO4, the yield of which was 92 and 98%, respectively. At an initial trinitroarene concentration of 0.10 M, the hydrolysis of triaminobenzene salts made it possible to synthesize phloroglucinol and methylphloroglucinol in 78 and 91% yields. Increasing the concentration to 0.15 M reduces the yield to 71 and 88%, respectively. According to thermal analysis data, the observed differences in the yields of triaminobenzene salts and polyphenols are explained by the formation of different amounts of resinous by-products on the catalyst surface during hydrogenation of trinitroarene. Hydrogenation of TNT produces less resin, resulting in higher yields of TAT⋅2H2SO4 and methyl phloroglucinol. This is probably due to the presence of an electron-donating methyl substituent, which slows down polycondensation of TAT molecules.

The catalytic hydrogenation of dinitroaromatic compounds is an important reaction for the production of phenylenediamine derivatives, which are widely used in industry. In this work, the catalytic properties of a Cu–Al mixed oxide obtained from double layered hydroxide have been investigated in liquid-phase hydrogenation of 1,3-dinitrobenzenes under continuous-flow conditions. The reaction was carried out at temperature of 120 °C, total pressure of 30 bar, using methanol or methanol/isopropanol mixture as a solvent. It was found that hydrogenation of 1,3-dinitrobenzene, 2,4-dinitrotoluene, 2,4-dinitroanisole and 2,4-dinitromesitylene provides the selective formation of the corresponding diamines, which were isolated in the form of salts with sulfuric acid stable in storage. The effect of the reaction temperature, pressure, H2 flow rate, and solvent nature on the catalyst performance was studied.

A series of bifunctional catalysts, MoS2/Al2O3 (70 wt.%), zeolite (30 wt.%) (zeolite—ZSM-5, ZSM-12, and ZSM-22), and silica aluminophosphate SAPO-11, were synthesized for hydroconversion of methyl palmitate (10 wt.% in dodecane) in a trickle-bed reactor. Mo loading was about 7 wt.%. Catalysts and supports were characterized by different physical-chemical methods (HRTEM-EDX, SEM-EDX, XRD, N2 physisorption, and FTIR spectroscopy). Hydroprocessing was performed at a temperature of 250–350 °C, hydrogen pressure of 3.0–5.0 MPa, liquid hourly space velocity (LHSV) of 36 h−1, and an H2/feed ratio of 600 Nm3/m3. Complete conversion of oxygen-containing compounds was achieved at 310 °C in the presence of MoS2/Al2O3-zeolite catalysts; the selectivity for the conversion of methyl palmitate via the ‘direct’ hydrodeoxygenation (HDO) route was over 85%. The yield of iso-alkanes gradually increases in order: MoS2/Al2O3 < MoS2/Al2O3-ZSM-12 < MoS2/Al2O3-ZSM-5 < MoS2/Al2O3-SAPO-11 < MoS2/Al2O3-ZSM-22. The sample MoS2/Al2O3-ZSM-22 demonstrated the highest yield of iso-alkanes (40%). The hydroisomerization activity of the catalysts was in good correlation with the concentration of Brønsted acid sites in the synthesized supports.

Many research papers describe selective hydrogenation of functional groups, such as nitro groups, carbonyl groups, or unsaturated carbon bonds to obtain fine chemicals or precursors of pharmaceuticals. Quite often, the catalyst performance is investigated in batch or continuous flow reactors without finding advantages and disadvantages of this or that regime. At the same time, the transition from batch processes to continuous flow occurs on the industrial scale. However, the batch process can be preferable for some reactions, in spite of its drawbacks. This review article aims to identify all publications that consider selective hydrogenation of functional groups in organic compounds, both in batch and continuous flow reactors, at the same reaction conditions that allow making conclusions about the benefits of one of the regimes in a particular case.

Cu-containing layered double hydroxides (LDHs) were synthesized by a co-precipitation method at different reaction conditions, such as aging time, pH, precipitation rate and synthesis temperature. The effect of these parameters on the structure and chemical composition of the catalysts were investigated using a set of physical methods, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), H2-TPR and in situ X-ray photoelectron spectroscopy (XPS). It allowed for checking of the reducibility of the samples. 5-Acetoxymethylfurfural was catalytically hydrogenated to 5-(acetoxymethyl)-2-furanmethanol (AMFM) over Cu-containing catalysts synthesized from layered double hydroxides so as to investigate its catalytic properties in flow reaction. It was shown that synthesis pH decreasing from 10 to 8 resulted in rise of AMF conversion that coincided with the higher surface Cu/Al ratio obtained by XPS. Preferable aging time of LDH materials for obtaining the most active catalyst was 2 h, an amount of time that favored the production of the catalyst with high surface Cu/Al ratio up to 0.38. Under optimized reaction conditions, the AMFM yield was 98%. Finally, a synthesis strategy for the preparation of highly efficient Cu-based hydrogenation catalyst with optimized characteristics is suggested.

Levulinic acid and its esters (e.g., ethyl levulinate, EL) are platform chemicals derived from biomass feedstocks that can be converted to a variety of valuable compounds. Reductive amination of levulinates with primary amines and H2 over heterogeneous catalysts is an attractive method for the synthesis of N-alkyl-5-methyl-2-pyrrolidones, which are an environmentally friendly alternative to the common solvent N-methyl-2-pyrrolidone (NMP). In the present work, the catalytic properties of the different nickel phosphide catalysts supported on SiO2 and Al2O3 were studied in a reductive amination of EL with n-hexylamine to N-hexyl-5-methyl-2-pyrrolidone (HMP) in a flow reactor. The influence of the phosphorus precursor, reduction temperature, reactant ratio, and addition of acidic diluters on the catalyst performance was investigated. The Ni2P/SiO2 catalyst prepared using (NH4)2HPO4 and reduced at 600 °C provides the highest HMP yield, which reaches 98%. Although the presence of acid sites and a sufficient hydrogenating ability are important factors determining the pyrrolidone yield, the selectivity also depends on the specific features of EL adsorption on active catalytic sites.

An environmentally friendly and safe synthesis of phloroglucinol and its derivatives through the flow hydrogenation of 1,3,5-trinitrobenzenes on heterogeneous copper catalysts is reported. It was found that hydrogenation of 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene, 2,4,6-trinitroxylene, and 2,4,6-trinitromesitylene in methanol over Cu-Al mixed oxides derived from layered double hydroxides led to selective formation of the corresponding triaminobenzenes, which were isolated from the reaction mixture in the form of double salts with sulfuric acid and were stable in storage. Subsequent hydrolysis in aqueous solution gave the phloroglucinol derivatives in good yields (75-82%).

Aminomethylhydroxymethylfuran derivatives are well known for their pharmaceutical activities. In this work, the two-step one-pot procedure for the synthesis of N-substituted 5-(acetoxymethyl)-2-furfuryl amines was proposed, which includes two successive reactions: the condensation of 5-acetoxymethylfurfural (AMF) with primary amines and the reduction of obtained imines with hydrogen over supported metal catalysts in a flow reactor. The comparison of the properties of Au, Pd and Pt catalysts in the hydrogenation of imine obtained by reaction of AMF with aniline showed that Pt-based catalysts (both Pt/Al2O3 and Pt/C) are highly active and provide high selectivity and stability, while Pd and Au nanoparticles supported on gamma-alumina and carbon show low selectivity. A wide range of N-substituted 5-(acetoxymethyl)-2-furfuryl amines was synthesized in good to excellent yields using Pt/Al2O3 catalyst and methanol as a solvent.

N-alkyl-5-methyl-2-pyrrolidones are an attractive alternative to the common solvent N-methyl-2-pyrrolidone (NMP) and can be used as starting materials for synthesis of various valuable chemicals. Reductive amination of alkyl levulinates derived from biomass feedstock is a promising method for production of these compounds. In the present work, N-alkyl-5-methyl-2-pyrrolidones were obtained in excellent yields by reductive amination of ethyl levulinate with alkylamines over SiO2-supported nickel phosphide in a flow reactor using molecular hydrogen as a reducing agent. At the same time, aromatic amines and 1-nitropropane give a lower yield of the corresponding pyrrolidones. The influence of the solvent nature, temperature, pressure, hydrogen and liquid flow rates on the catalyst performance was studied.

Co-processing of mixture, containing 30 wt.% of rapeseed oil (RSO) in straight run gas oil (SRGO), was studied over stacked bed sulfide catalytic system containing Mo/Al2O3 as a first layer and CoMo/Al2O3-SAPO-11 or NiMo/Al2O3-SAPO-11 catalyst as the second one. The experiments were performed in a trickle bed reactor at 350-380 degrees C, 4.0-7.0 MPa, 1.5 h(-1) and 1000 Nm(3)/m(3). The hydrodeoxygenation (HDO) of RSO is proceeding over Mo/Al2O3 catalyst mostly through direct HDO route (selectivity > 93 %). The proposed combination of catalysts minimizes the formation of carbon monoxide, that is known as an inhibitor of hydrotreating reactions and can affect the hydroisomerisation/hydrocraking of alkanes over CoMo/Al2O3-SAPO-11 and NiMo/Al2O3- SAPO-11 catalysts. The effects of temperature and pressure on the behavior of Mo/Al2O3-CoMo/Al2O3-SAPO-11 and Mo/Al2O3-NiMo/Al2O3-SAPO-11 systems were studied and the difference in the quality of products were discussed with the emphasis on the cold flow properties. The cloud point of products, obtained in the co processing of RSO-SRGO mixture over Mo/Al2O3-CoMo/Al(2)O3-SAP and Mo/Al2O3-NiMo/Al2O3-SAP catalytic systems was decreased to-8 and-13 degrees C respectively with the temperature increase from 350 to 380 degrees C. In addition, the hydrogenated products produced over NiMo/Al2O3-SAP were characterized by lower final boiling point values and aromatic content in comparison with that produced over CoMo/Al2O3-SAP catalyst. Unexpectedly, the opposite effect of pressure was observed on the cloud point and the conversion of long chain alkanes, which were produced in hydrodeoxygenation of RSO.

Various amino acid-based furfurylamine derivatives were synthesized by two-stage procedure, which includes the condensation of 5-hydroxymethylfurfural (or furfural) with amino acid salts in methanol followed by hydrogenation of obtained imines in a flow reactor over CuAlOx catalyst.

The catalytic properties of a platinum catalyst supported on γ-alumina in the hydrogenation of imines formed during the condensation of 5-hydroxymethylfurfural (HMF) with primary amines in methanol have been studied. The reaction has been run in a flow reactor at a hydrogen pressure of 5 bar and a temperature of 15–65ºC. It has been found that the reductive amination of HMF with n-hexylamine; aniline; ortho-, meta-, and para-toluidines; and aniline derivatives containing F, Cl, Br, and I substituents at the para- or meta-positions leads to the formation of N-substituted 5-hydroxymethyl-2-furfuryl amines with high yields (90–99%). At the same time, the reaction of HMF with aromatic amines exhibiting weak nucleophilic properties (o-chloroaniline, p-aminoacetophenone) provides a target product yield that does not exceed 52%.