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This review fills an apparent gap existing in the literature by providing an overview of the readily available terpenes and existing catalytic protocols for preparation of terpene-derived amines. To address the role of solid catalysts in amination of terpenes the same reactions with homogeneous counterparts are also discussed. Such catalysts can be considered as a benchmark, which solid catalysts should match. Although catalytic systems based on transition metal complexes have been developed for synthesis of amines to a larger extent, there is an apparent need to reduce the production costs. Subsequently, homogenous systems based on cheaper metals operating by nucleophilic substitution (e.g., Ni, Co, Cu, Fe) with a possibility of easy recycling, as well as metal nanoparticles (e.g., Pd, Au) supported on amphoteric oxides should be developed. These catalysts will allow synthesis of amine derivatives of terpenes which have a broad range of applications as specialty chemicals (e.g., pesticides, surfactants, etc.) and pharmaceuticals. The review will be useful in selection and design of appropriate solid materials with tailored properties as efficient catalysts for amination of terpenes.

Structure sensitivity in hydrogenation of arabinose and galactose was studied over supported ruthenium catalysts with the cluster size ranging from 1 to 8 nm. Ruthenium on carbon supports with different ruthenium particle sizes were prepared by incipient wetness impregnation and colloidal method. Catalytic activity was seen to have almost no dependence on the substrate being, however, sensitive to the cluster size. The highest turnover frequency (TOF) was obtained with a catalyst having average ruthenium particle size of ca. 3 nm. A mathematic model incorporating cluster size dependent rate constants was used to quantitatively describe experimental data on TOF. Graphical Abstract

Catalytic deoxygenation of tall oil fatty acids (TOFA) was demonstrated over palladium catalysts supported on mesoporous carbon at 300 °C using dodecane as a solvent. Maximally 95% selectivity to linear C17 hydrocarbons was achieved. The effects of reaction atmosphere and initial TOFA concentration were investigated.

The deoxygenation experiments of different reactants, i.e., pure palmitic acid, stearic acid, and a technical grade stearic acid containing a mixture of 59% of palmitic and 40% of stearic acid were successfully performed over 4 wt% Pd/C mesoporous catalyst at 300 °C under 17 bar of 5% H₂ in argon. The main product in catalytic deoxygenation of saturated fatty acids, C16 and C18, were aliphatic chain length hydrocarbons containing one less carbon than the corresponding acid. Additionally it was found that the deoxygenation rates of different reactant were independent on carbon chain length of its fatty acids.

The process of catalytic hydrogenation of furfural diethyl acetal to ethyl furfuryl ether on the different catalysts (palladium, palladium-rhenium and copper-ruthenium on Sibunit in reduced forms) was studied. It was found that hydrogenation of the furan ring with the formation of THF diethyl acetal occurs on all the catalysts. Ethyl furfuryl ether becomes the main product while carrying on the second hydrogenation cycle on spent palladium catalyst (yield and selectivity up to 55 % and 85 %, respectively)

Selective oxidation of glucose into gluconic acid by molecular oxygen over carbon-supported Pt and Pd catalysts was studied. Under examination were kinetic regularities of the process in respect of the electronic state of the noble metal surface, dispersion of the active component particles as well as substrate:Pt(Pd) ratio. Catalytic activity of the Pt/C catalysts being normalized to the dispersion of the platinum particles appeared independent of the particles mean diameter in the 1-5 nm range. A negative particle size effect for the Pd/C catalysts, caused by feasibility of oxidation of the surface of noble metal particles with the size less than 3 nm, was observed. Pt/C catalysts exhibited lower specific activity and provided poor selectivity of the glucose oxidation in comparison with Pd/C. Deactivation of Pd/C catalysts arising from the formation of surface Pd(II) oxides was retarded when the reaction was carried out under an oxygen-diffusion control. Graphical Abstract Selective oxidation of glucose to gluconic acid over carbon supported palladium and platinum catalysts proceeds with the selectivity up to 97 and 77%, respectively. Catalytic activity of the carbon-supported Pt nanoparticles with diameters ranging from 1 to 5 nm towards the selective oxidation of glucose is directly proportional to platinum surface area. Finely dispersed Pd/C catalysts (〈d Pd〉 =3 nm) are prone to deactivation due to oxidation of their surface, while larger metal particles (〈d Pd〉 =6 nm) are more tolerant and stable. The activity of Pd nanoparticles can be maintained when the process is controlled by diffusion of oxygen towards the active component of the catalyst. [graphic removed]

Catalytic continuous deoxygenation of stearic acid, ethyl stearate and tristearin without any solvents was investigated using Pd/Sibunit as a catalyst in a trickle bed reactor at 300 °C. The main emphasis was to investigate the effect of gas atmosphere and catalyst deactivation. In addition to liquid-phase analysis made offline by GC, also online gas-phase analysis with IR were performed. The main liquid-phase product coming from all reactants was n-heptadecane. In addition to deoxygenation, which was observed for all substrates, also C18 and C16 alkanes were formed from tristearin. The relative ratios between stearic acid, ethyl stearate and tristearin conversions to alkanes after 3 days time-on-stream were 2.8/2.3/1.0, respectively using 5 % H2/Ar as a gas atmosphere, whereas rapid catalyst deactivation occurred with all substrates under H2-lacking atmosphere. The spent catalyst’s specific surface area profile along the downward reactor was maximum in the middle of the catalyst beds with the highest pore shrinking in the beginning and at the end of the reactor catalyst segments in the case of stearic acid and tristearin deoxygenation whereas that decreased consecutively as ethyl stearate passed through the reactor.

The transformation reaction of 1-(2-aminophenyl)propan-2-ol was studied at 200 °C under argon pressure. A range of catalysts was applied including carbon, titania and zeolite supported Ru, Pd, Pt, Rh, and Ir, as well as metal free zeolites. The highest conversion was obtained with H-Beta-150 and H-Beta-25 and the highest selectivity to 2-methylindoline was achieved with 0.3 % Ir–H-Beta-150 and H-Beta-25. Although the selectivity to 2-methylindole was high for all catalysts, formation of the final product 2-methylindoline only took place over the most acidic catalysts. Graphical Abstract

Liquid phase levulinic acid hydrogenation into γ-valerolactone in 1,4-dioxane as a solvent (165°C, 20 bar) was studied over a range of Ru monometallic catalysts using mesoporous carbon material Sibunit as a support. In addition to the catalyst prepared by impregnation with RuCl3∙nH2O (0.1 M) followed by reduction in H2, size-controlled Ru(NPs)/Sibunit catalysts were synthesized by immobilization of polyvinylpyrrolidone (PVP) stabilized Ru nanoparticles (NPs) (dRu=2.4 nm). Сarbon supported colloidal Ru NPs were not studied earlier in levulinic acid hydrogenation. Activity of colloidal Ru(NPs)/Sibunit catalysts was found to be lower than that of impregnated Ru/Sibunit which could be attributed to hampering effect of PVP. However, colloidal Ru(NPs)/Sibunit purified by thermal treatment in air (180°C) followed by reduction in H2 (400°C) exhibited the same activity as impregnated one yielding 93% γ-valerolactone at 100% levulinic acid conversion. Applicability of supported PVP-assisted colloidal Ru NPs in hydrogenation of levulinic acid illustrates a potential to prepare more efficient catalysts for this reaction with a desired particle size. The catalysts were characterized by TEM, XRF, and N2 physisorption to compare their physical chemical properties

A theoretical analysis of the influence of particle size distribution on observed TOF dependence on cluster size is presented for a two step catalytic cycle. Such mechanism can display different TOF behavior including maxima. In the later case simulations demonstrated broadening of TOF curves compared to an idealized case of very narrow PSD. However, for more often observed cases with smooth TOF increase or decrease with cluster size increase incorporation of particle size distribution in kinetic analysis is not required at least for often experimentally observed particle size distributions. Graphical Abstract