Hydrogenation Of Acids Research Articles

Catalytically efficient Co-CoOx-Al2O3 interface for mild temperature fatty alcohol production via fatty acid transfer hydrogenation

The cost-effective and environmentally friendly conversion of biomass to value-added chemicals under mild conditions is highly desirable but challenging. Herein, two-dimensional Co-Al hydrotalcite catalysts (CoAl-LDOx) were fabricated for selective catalytic transfer hydrogenation (CTH) of fatty acids to fatty alcohols with isopropanol (2-PrOH) as hydrogen donor. The structure and morphology of surface Co species can be regulated via reduction temperature. The optimal CoAl-LDO600 with high Co dispersion, modest reducibility, and rich Co-CoOx-Al2O3 interface achieved the highest octadecanol yield (94.2%) at full oleic acid conversion under 200 °C for 3 h. This catalyst was magnetically separable, highly stable and versatile for various fatty acids to achieve 89.1–96.7% alcohol yields. Controlled experiments suggest that 2-PrOH dehydrogenation was not highly dependent on Co structure, while the interfacial synergy of metallic Co and oxidized Co boosted the active hydrogen transfer, thus accelerating the overall reaction. The present work provided a boosted and stable catalytic system for biomass-related hydrogenation reactions without any external hydrogen supply.

Concise Enantioselective Total Synthesis of Isopavine Alkaloids.

Herein, we report a concise asymmetric total synthesis of isopavine alkaloids, which feature a special azabicyclo[3.2.2]nonane tetracyclic skeleton. The key steps include iridium-catalyzed asymmetric hydrogenation of unsaturated carboxylic acids, Curtius rearrangement, and Eschweiler-Clarke methylation, which enable an enantioselective approach to isopavine alkaloids in 6-7 linear steps. Furthermore, for the first time, isopavine alkaloids, especially (-)-reframidine (3), are found to display effective antiproliferative effects on various cancer cell lines.

Competent production of hydrogen and hydrogenation of carboxylic acids using urea-rich waste water over visible-light-responsive rare earth doped photocatalyst

BackgroundA strategy employing water as a hydrogen source is promising but challenging. Conversely, urea is the major pollutants causing substantial water pollution. Moreover, direct reduction of carboxylic acids into aldehydes is still a great challenge due to higher propensity of aldehydes being further reduced to alcohols. MethodsWe report a visible-light driven one-step protocol to selectively convert aromatic carboxylic acids to aldehydes with water as the sustainable hydrogen source, environmental pollutant urea as a hole scavenger and Eu3+ doped Na2CaP2O7 phosphor as a viable photocatalyst. Significant findingsApart from the photocatalytic H2 evolution, the procedure is able to reduce a broad range of carboxylic substrates with good functional group tolerance in good to excellent yield. The insertion of Eu3+ into the present host creates several metastable states inside the forbidden region and thereby led to enhancement of photo stimulation process. Moreover, various experiments and analytical analysis reveal that photo-generated active H-species from water are the direct reducing agent, skipping the use of traditional flammable H2. Present work provides a ‘waste-to-value’ route for solar energy driven preparation of valuable chemicals by simultaneous photocatalytic treatment of urea-rich waste water.

Antioxidant Activity of Sulfate Metabolites of Chlorogenic Acid

This study aimed to determine the antioxidant properties of the sulfate monoesters of ferulic, caffeic, dihydroferulic and dihydrocaffeic acids, the main metabolites of chlorogenic acids. These compounds are not commercially available, so they were synthesized in the laboratory. The LC-MS/MS analysis allowed for the full characterization of these derivatives, which has made them reliable standards for further research. Purified metabolites including ferulic acid-4-O-sulfate, caffeic acid-4-O-sulfate and caffeic acid-3-O-sulfate, dihydrocaffeic acid-4-O-sulfate and caffeic acid-3-O-sulfate were examined for their antioxidant capacities and compared to their precursor compounds using Folin–Ciocalteu, CUPRAC (cupric ion—reducing) and DPPH• (2,2-diphenyl-1-picrylhydrazyl) methods. This study shows that hydrogenation of caffeic and ferulic acids into dihydrocaffeic and dihydroferulic acids has a positive influence on their reducing properties. Moreover, all synthesized sulfate monoesters exhibited very weak antioxidant properties compared to precursor compounds. The presented results show that the transformation of phenolic acids via sulfation leads to the inhibition of antioxidant properties due to the blockage of hydroxyl groups.

Hydrogenation of Carboxylic Acids, Esters, and Related Compounds over Heterogeneous Catalysts: A Step toward Sustainable and Carbon-Neutral Processes

The catalytic hydrogenation of esters and carboxylic acids represents a fundamental and important class of organic transformations, which is widely applied in energy, environmental, agricultural, and pharmaceutical industries. Due to the low reactivity of the carbonyl group in carboxylic acids and esters, this type of reaction is, however, rather challenging. Hence, specifically active catalysts are required to achieve a satisfactory yield. Nevertheless, in recent years, remarkable progress has been made on the development of catalysts for this type of reaction, especially heterogeneous catalysts, which are generally dominating in industry. Here in this review, we discuss the recent breakthroughs as well as milestone achievements for the hydrogenation of industrially important carboxylic acids and esters utilizing heterogeneous catalysts. In addition, related catalytic hydrogenations that are considered of importance for the development of cleaner energy technologies and a circular chemical industry will be discussed in detail. Special attention is paid to the insights into the structure-activity relationship, which will help the readers to develop rational design strategies for the synthesis of more efficient heterogeneous catalysts.

Local reactivity descriptors to decipher the electrochemical hydrogenation of unsaturated carboxylic acids

We explain the intricate interplay between electronic properties and reactivity during the electrochemical hydrogenation of biobased unsaturated (di)acids under acidic and neutral conditions.

ReOx promotes Ni cluster interactions on TiO2 to improve the activity and durability for green alkane and alcohol production at low temperature

Enhancing both the reactivity and durability of catalysts for the hydrogenation of bio-derived fatty acids is a formidable challenge.

Key Intermediates in the Hydrogenation of Carboxylic Acids on the Pt–ReOx/TiO2 Catalyst

Key Intermediates in the Hydrogenation of Carboxylic Acids on the Pt–ReOx/TiO2 Catalyst

Heterogeneously Catalyzed Carboxylic Acid Hydrogenation to Alcohols

AbstractThis critical review discusses the synthesis of alcohols via hydrogenation of carboxylic acids promoted by heterogeneous metal catalysis. The introductory chapter rationalizes the comparative reactivity of carboxylic acid derivatives, which is proceeded by a description of different mechanisms for carboxylic acid hydrogenation. Reaction pathways are discussed that give rise to undesired side products, before comparing the reactivity of different classes of carboxylic acid substrates with a focus on biomass‐derived carboxylic acids. The final portion of the review aims to guide researchers in the selection of appropriate reaction conditions, such as the choice of solvent, transition metal, and catalyst support.

Boosting chiral carboxylic acid hydrogenation by tuning metal-MO -support interaction in Pt-ReO /TiO2 catalysts

Engineering the surface microenvironment by tuning the binary interactions between a supported metal with a secondary metal oxide (MOx) or support has been a common method for improving the catalytic performance of supported metal catalysts. However, few studies have investigated the ternary interactions among the metal, MOx, and support. Here, we report for the first time the formation of metal-MOx-support interaction (MMSI) in reducible TiO2-supported PtReOx catalysts, affording 87% yield and 100% ee in the tandem hydrogenation of an aqueous chiral cyclohexane-1,2-dicarboxylic acid into the corresponding diol; the catalytic activity is eight times higher than that obtained with non-reducible support counterparts in the same reaction via traditional batch synthesis with multiple steps and unfriendly reagents. Detailed experimental and computational studies suggest that the TiO2 crystalline phase-dependent density of the oxygen vacancies induces different Pt-ReOx-TiO2 interactions, which dominate the electron transfer therein and tune the adsorption strength of the carbonyl moiety of the substrate/intermediate, thus promoting the hydrogenation activity and selectivity. In addition, the strong MMSI endows the optimal rutile TiO2 supported PtReOx catalyst with an outstanding lifetime of 400 h in a fixed-bed reactor under acidic aqueous conditions and ensures efficient applications in the selective hydrogenation of aliphatic dicarboxylic acids and functional carboxylic acids. This work provides a promising strategy for the development of efficient and stable supported catalysts for the selective hydrogenation of diverse C–O and C=O bonds.

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

Hydrogenation of Alkyl Carboxylic Acids with Tetrahydropyrimidine-Derived Iridium Complexes under Mild Conditions

NiCu Anchored on a Specific TiO2 Face Tunes Electron Density for Selective Hydrogenation of Fatty Acids into Alkanes or Alcohols

NiCu Anchored on a Specific TiO₂ Face Tunes Electron Density for Selective Hydrogenation of Fatty Acids into Alkanes or Alcohols

Efficient low-temperature hydrogenation of fatty acids to fatty alcohols and alkanes on a Ni-Re bimetallic catalyst: The crucial role of NiRe alloys

Selective hydrogenation of fatty acids is important for production of sustainable fuels and valuable chemicals as well as for the utilization of natural oils and fats. Generally, high reaction temperature (>200 °C) is required due to the weak polarizability and low reactivity of the carbonyl group of fatty acids. Here, we report an efficient catalytic system (Ni-Re/SBA-15 bimetallic catalyst) that realizes the low-temperature conversion of fatty acids to corresponding alcohols (reaction temperature: 150 °C) and diesel-range alkanes (170 °C) with high yields, surpassing the catalytic performance rendered by most of the catalytic systems reported so far. Detailed investigation into the nature of the catalyst showed that the superior activity originated from the formation of NiRe alloy, which improved the dispersion of metallic Ni, the H2 activation ability and promoted the fatty acids/alcohols adsorption on the catalyst surface at low temperatures. More importantly, due to its strong electrophilicity, the fatty acids with highly electronegative carbonyl oxygen can be preferentially adsorbed on the catalyst surface than the fatty alcohols, which leads fatty acids to be converted preferentially. In this way, high catalytic efficiency and fatty alcohol selectivity can be obtained at a low temperature (150 °C). Further increasing reaction temperature to 170 °C, the reactant can be hydrodeoxygenated to form diesel-range alkanes. This developed NiRe/SBA-15 catalytic system highlights a great prospect for production of valuable fatty alcohols and alkanes from the conversion of bioderived fatty acids under mild conditions.

Nickel-Catalyzed Asymmetric Hydrogenation of γ-Keto Acids, Esters, and Amides to Chiral γ-Lactones and γ-Hydroxy Acid Derivatives.

A highly efficient asymmetric hydrogenation of a series of γ-keto acid derivatives, including γ-keto acids, esters, and amides, using a Ni-(R,R)-QuinoxP* complex as the catalyst has been developed to afford chiral γ-hydroxy acid derivatives with excellent enantioselectivities, up to 99.9% ee. This method provides not only an economical one-pot approach for the synthesis of chiral γ-lactones but also access to (S)-norfluoxetine, an inhibitor of neural serotonin reuptake and an essential intermediate for pharmaceutical synthesis.

Key intermediates in the hydrogenation of carboxylic acids over Pt-ReOx/TiO2 catalyst

The reactivity of different forms of adsorbed acetic acid on the Pt-ReOx/TiO2 catalyst was studied. To this end, in situ FTIR spectroscopy at T = 200 °С was used to identify three forms of adsorbed acetic acid: bidentate acetates and two forms of molecularly adsorbed acetic acid (1645–1653 and 1700–1720 cm–1). Rate constants for the consumption of two forms of molecularly adsorbed acetic acid, which are equal to 0.029 and 0.02 s–1, respectively, were found to be close to the rate constant of the catalytic reaction equal to 0.034 s–1, which was measured at T = 200 °С. It was concluded that two forms of molecularly adsorbed acetic acid serve as the key intermediates in the hydrogenation of acetic acid over Pt-ReOx/TiO2 catalyst.

Selective Reduction of Carboxylic Acids to Alcohols in the Presence of Alcohols by a Dual Bulky Transition-Metal Complex/Lewis Acid Catalyst

Here, we report a molecular method for the generally applicable reduction of mono- and dicarboxylic acids that selectively furnishes a diverse variety of alcohols, including mono- and diols. One of the inherent drawbacks of the direct hydrogenation of carboxylic acids to alcohols is the in situ formation of the corresponding esters via condensation of the carboxylic acids with the produced alcohols. Especially, the hydrogenation of polycarboxylic acids frequently suffers from the formation of a complex mixture of oligomeric esters. This issue was successfully overcome by the combined use of a dual catalyst that consists of a bulky (PNNP)iridium complex and a Lewis acid. Owing to the steric bulk and robustness of the iridium catalyst, the main role of the Lewis acid is to independently catalyze the esterification, albeit the cooperative activation of (a resting state of) the iridium catalyst by the Lewis acid also seems to be implied.

Process for the decarboxylation, isomerization, hydrogenation, dehydrogenation and cyclization aromatization of fatty acids yielding products with significant aromatic content

Multiwall carbon nanotubes supported MoO3 (Mo/MWCNTs) and potassium containing Mo/MWCNTs (K/Mo/MWCNTs) catalysts were prepared and characterized with XRD, N2-physisorption, SEM, TEM, NH3-TPD, and TGA/DTA. Increasing the Mo content (5–15 wt%) in Mo/MWCNTs samples diminished BET surface area and pore volume with concomitant increase of MoO3 particle size. Potassium addition to Mo/MWCNTs resulted in apparent decrease of their acid amounts and MoO3 particle sizes. These catalysts were utilized for selective oxidation of 1-dodecanol (DCOL) with air to obtain 1-dodecanal (DCAL). Various reaction parameters were investigated. It was found that K/Mo/MWCNTs exhibited much better catalyst performance than Mo/MWCNTs. Potassium loading on Mo/MWCNTs greatly enhanced DCOL conversion, DCAL selectivity, and catalyst stability due to smaller MoO3 particles and decreased acid sites.

Effects of surface functional groups of the N-containing carbon support on the catalytic properties of supported palladium

Nitrogen-containing mesoporous carbons (SNMC) were shaped by the drop ball method. A SNMC and a commercial coconut shell carbon (CSC) were oxidized by nitric acid to obtain the OSNMC and OCSC supports. Then, the Pd/OSNMC, Pd/SNMC, Pd/OCSC and Pd/CSC catalysts (5%wt) were prepared to study the effects of carboxyl group on the hydrogenation of C=C double bond. The results showed that both the doped N and surface O-containing functional groups increased the dispersion and surface electron density of supported Pd, leading to the increased heats for the adsorption of hexene and H 2 and thus the increased intrinsic activity for the hydrogenation of hexene on Pd. The pre-adsorption of propionic acid (PA) significantly inhibited the adsorption of hexene and H 2 and decreased the conversion of hexene on Pd. However, the surface O-containing functional groups inhibited the adsorption of carboxyl groups and offset the inhibition effect of carboxyl groups on the hydrogenation of hexene on Pd, while the doped N atoms played the opposite role. Thus, it is expected that the surface O-containing functional groups are beneficial to the hydrogenation of unsaturated fatty acids on Pd/C catalysts. The doped N and surface O-containing functional groups in carbon supports were electron donators that increased the electron charges of supported Pd on which the adsorption of hexene was enhanced and led to the increase in intrinsic activity for the hydrogenation of hexene. The strong adsorption of propionic acid (PA) inhibited the adsorption of hexene and lowered the conversion of hexene on Pd/C, which was offset by the surface O-containing functional groups. • Doped N in C supports enhanced dispersion of Pd and donated electron charges to Pd. • Surface O groups also enhanced dispersion of Pd and donated electron charges to Pd. • Electron enriched Pd favored adsorption of hexene and thus its hydrogenation. • Carboxyl groups strongly inhibited adsorption of hexene and thus its hydrogenation. • Surface O groups offset inhibition effect of -COOH on adsorption of hexene on Pd.

Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol

• Octanoic acid was converted over RuSn supported on ZnO. • High conversion (99.4 %) and selectivity to octanol (93.0 %) were achieved. • Ru 3 Sn 7 alloy phase was responsible for the high hydrogenation activity. • Esterification was suppressed by optimizing the reaction condition. • RuSn/ZnO was exceptionally robust over 1000 h. The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h −1 , and 30 atm H 2 ). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru 3 Sn 7 alloy phase as well as SnO x . Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru 3 Sn 7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnO x and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.

Electrocatalytic Nuclear Hydrogenation of Benzoic Acids in a Proton Exchange Membrane Reactor

The nuclear hydrogenation of aromatic substrates to obtain saturated cyclic compounds is of great importance in the field of chemical and pharmaceutical industry, due to its readily obtained feedstocks, environmentally friendly and straightforward routes.1 For instance, the chemoselective hydrogenation of benzoic acids to cyclohexanecarboxylic acids has attracted great attention, as the hydrogenated products cyclohexanecarboxylic acids are important organic intermediates for pharmaceuticals, such as praziquantel, caprolactam, and ansatrienin.Several efficient catalysts based on monometallic Pd, Pt, Rh, and Ru and several alloys have been explored for the aromatic nuclear hydrogenation of benzoic acid and its derivatives.2 However, most of the catalytic reactions were performed under a high pressure of hydrogen gas, which leads to safety concerns. Therefore, the development of hydrogenation of benzoic acids to cyclohexanecarboxylic acids under mild conditions is still a challenging target.Under these backgrounds, we have demonstrated electrocatalytic nuclear hydrogenation in a proton exchange membrane (PEM) reactor (Figure 1). This system has several merits such as easy separation and recycle use of catalysts, operation under mild and benign conditions.3 We found that the use of PEM reactor with PtRu catalyst gave the corresponding cyclohexanecarboxylic acids with excellent current efficiencies in our demonstrations.AcknowledgementThe authors gratefully acknowledge supports by a CREST (JST Grant No.: JP65R1204400), Japan.References L. Zhang, J. Dong, X. L. Qiao, J. R. Qin, H. F. Sun, A. Q. Wang, L. B. Niu, G. Y. Bai, J. Catal., 372, 258–265 (2019).D. Dwivedi, R. K. Rai, K. Gupta, S. K. Singh, ChemCatChem, 9, 1930 – 1938 (2017).Fukazawa, J. Minoshima, K. Tanaka,Y. Hashimoto, Y. Kobori, Y. Sato, M. Atobe, ACS Sustain. Chem. Eng., 7, 11050-11055 (2019). Figure 1