Catalysts For Hydrogenolysis Of Glycerol Research Articles

Copper Zinc Aluminate Synthesized by Sol‐Gel Method with Polyacrylic Acid as Catalysts for Glycerol Hydrogenolysis

AbstractThis study describes the use of novel Cu/ZnO/ZnAl2O4/PAAH (PAAH=polyacrylic acid) hybrid nanomaterials for glycerol hydrogenolysis. Their elaboration by sol‐gel process either in one step or in two steps allowed to modulate their structural properties in terms of specific surface area, Lewis acidity, sizes and dispersion of copper nanoparticles. The presence of PAAH and aluminium during the synthesis particularly showed benefits in terms of dispersion and metal‐support interaction. The characterization of the catalyst surfaces in composition and size of the copper nanoparticles allowed to establish structure‐reactivity relationships. Their optimization allowed to reach remarkable conversions up to 96 % with selectivity towards 1,2‐propanediol of 83 %. A recyclability study also showed a possible reuse of these catalysts after a reactivation step.

Insights into the Nature of the Active Sites of Pt-WOx/Al2O3 Catalysts for Glycerol Hydrogenolysis into 1,3-Propanediol

The chemo-selective hydrogenolysis of secondary hydroxyls is an important reaction for the production of biomass-derived α,ω-diols. This is the case for 1,3-propanediol production from glycerol. Supported Pt-WOx materials are effective catalysts for this transformation, and their activity is often related to the tungsten surface density and Brönsted acidity, although there are discrepancies in this regard. In this work, a series of Pt-WOx/γ-Al2O3 catalysts were prepared by modifying the pH of the solutions used in the active metal impregnation step. The activity–structure relationships, together with the results from the addition of in situ titrants, i.e., 2,6-di-tert-butyl-pyridine or pyridine, helped in elucidating the nature of the bifunctional active sites for the selective production of 1,3-propanediol.

An Active K‐OMS‐2 Supported Catalyst for Hydrogenolysis of Glycerol

AbstractPropanediols are very important chemical intermediates, which need to be prepared through commercially viable routes. Cryptomelane type octahedral molecular sieve‐2 (K‐OMS‐2), a cheap and environmentally benign microporous oxide was employed to support Ru and used as a catalyst to get 1,2‐propanediol (1,2‐PDO) selectively through hydrogenolysis of glycerol. Three catalysts with different Ru content were prepared and evaluated for glycerol hydrogenolysis. Among these, 1 wt.% Ru‐K‐OMS‐2 showed reasonably good activity towards 1,2‐PDO formation under moderate reaction conditions even at lower Ru loading (0.9 wt.%). When other metals such as Cu and Ni were supported on K‐OMS‐2, their performance was inferior compared to Ru‐supported catalysts. All the catalysts were characterized using various physicochemical techniques like XRD, N2‐sorption, TPD, H2‐TPR, TGA, ICP‐OES, FE‐SEM and TEM. The enhanced catalytic activity with the 1 wt.%Ru‐K‐OMS‐2 catalyst was attributed to the better Ru metal dispersion, higher active metal surface area, basic strength, and porosity of the support. The catalyst was found to be recyclable. Analysis of spent catalyst by TEM showed disintegration of Ru nanoparticles to smaller ones, under high H2 pressure at the reaction temperature. Smaller Ru particles are expected to promote C−C bond cleavage thus suppressing 1,2‐PDO formation. Furthermore, a relationship between the TOF value, Ru nanoparticles size, and the basic strength of the catalysts was established, which provides dipper insight into the different catalytic behavior of the catalysts.

The Promotional Effect of Sulfates on TiO2 Supported Pt‐WOx Catalyst for Hydrogenolysis of Glycerol

AbstractPt‐WOx based catalysts were widely investigated and showed high industrial application potential for glycerol hydrogenolysis. Further improving the catalytic activity and stability of the Pt‐WOx based catalysts is important. Herein, we modified the TiO2 supported Pt‐WOx catalyst with sulfate doping and employed for the glycerol hydrogenolysis. The introduction of sulfates dramatically promoted the catalytic activity and stability of the Pt/W/Ti catalyst in glycerol hydrogenolysis. Sulfates‐doped Pt/W−S/Ti achieved 100 % conversion of glycerol, with 36 % selectivity to 1,3‐PDO and 57 % selectivity to n‐PO at 120 °C and 4 MPa, while the conversion over Pt/W/Ti only reached 57 %. Moreover, Pt/W−S/Ti offered 22.5 times more glycerol conversion (90 %) than Pt/W/Ti (4 %) for the second run. The much higher activity of the Pt/W−S/Ti was ascribed to the better dispersion of Pt and WOx species and more Brønsted acid amount. The enhanced stability of Pt/W−S/Ti was attributed to its strong anti‐leaching ability after sulfate doping.

Synthesis of Cu-based catalysts for hydrogenolysis of glycerol to 1,2-propanediol with in-situ generated hydrogen

This study focuses on the "green" conversion of glycerol to 1,2-propanediol using the Cu-Al-Zn catalyst prepared by the co-precipitation method. Different ratios of (Cu+Zn)/Al were synthesized; the Zn and Al contents were varied while the Cu was kept constant (the Zn/Al ratios were 3:1, 4:1, 5:1, and 6:1). Catalyst characterization using TPD, XRD, and SEM, showed that the synthesized catalysts consisted of hydrotalcite with basic and acidic sites. The basicity of the catalysts was found to be an important criterion for the catalytic transfer hydrogenation, with the basic sites of the catalyst increasing the conversion of glycerol. Copper appeared to have an impressive effect on the C-O/C-C cleavage of glycerol during indirect hydrogenolysis for the synthesis of 1,2-propanediol. A reaction mechanism based on the hydrogenation of ethanol at Cu sites and the formation of intermediates at the basic sites of the catalysts was proposed.

Ni/CeO2 as catalyst for glycerol hydrogenolysis without external H2 supply: the role of synthesis conditions

Aqueous phase processes at high pressure are considered one of the most promising thermochemical processes to valorize wet residual streams, in order to produce value-added chemicals. Among them, glycerol hidrogenolysis (HG) has been intensely studied. Although many different catalytic systems for HG have been studied in the last years, the Ni/CeO2 catalytic system has not been so deeply performed in liquid phase. 
 This work studies the hydrogenolysis of glycerol without external H2 supply as a pathway to obtain value-added chemicals using Ni/CeO2 catalysts. Different synthesis parameters were changed, in order to determine their influence on the catalytic activity. In this process, 1,2–propanediol and ethylene glycol are produced, compounds which are valuable due to their use in chemical synthesis, antifreeze fluids, and others.

Effect of Silica Particle Size on Texture, Structure, and Catalytic Performance of Cu/SiO2 Catalysts for Glycerol Hydrogenolysis

The influences of carrier particle sizes of Cu/SiO2 catalysts for hydrogenolysis of glycerol were studied use mono-dispersed silica as models. Catalysts were prepared by precipitation method with the average size of the mono-dispersed silica supports varying of 10, 20, and 90 nm. Characterization of the catalysts show that the physical properties such as pore volume and BET surface area of the catalysts were largely affected by the carrier particle size of silica. However, the copper dispersion of the three samples were similar. XPS patterns show a difference in the chemical states of copper species, small carrier particle size induced formation of copper phyllosilicate, which benefits on the stability of copper species in reaction. The overall activity in the reaction of glycerol hydrogenolysis shows a correlation with the carrier particle size. The small carrier particles prevent the copper species from aggregation thus such catalysts exhibit good catalytic activity and stability.

Alcohol-treated SiO2 as the support of Ir-Re/SiO2 catalysts for glycerol hydrogenolysis

The surface of SiO2 support was pretreated by C1–C4 normal alcohols before the impregnation of iridium and rhenium precursors. These catalysts were applied in high concentration glycerol aqueous solution hydrogenolysis. The catalysts prepared from the pretreated supports exhibited high catalytic activity because of the formation of more active sites from a high dispersion of iridium oxide and rhenium oxide. The catalysts with the support pretreated by 1-propanol showed the highest glycerol conversion of 59.5%. The supports and catalysts were characterized by FT-IR, nitrogen adsorption, TPR, XRD, TEM, H2-chemisorption and NH3-TPD.

A Highly Active Cu–Pt/SiO2 Bimetal for the Hydrogenolysis of Glycerol to 1,2-Propanediol

A series of bimetallic Cu samples (Cu–Pt/SiO2, Cu–Pd/SiO2, Cu–Ag/SiO2, Cu–Ni/SiO2) were prepared by wetness impregnation method, then investigated for hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). We furthered the study and found that Cu–Pt/SiO2 got the smallest particle size and greatest dispersion. Besides, it was found that Pt promoted reduction of Cu2+. Compared with other Cu–Pt molar ratio, Cu–Pt/SiO2 (1:0.2) was the preferable catalyst for hydrogenolysis of glycerol to 1,2-PDO. It is worth noting that Cu–Pt/SiO2 presented the highest activity with a 96 % selectivity to 1,2-PDO and a nearly 100 % conversion of glycerol at 473 K, 40 bar initial H2 pressure, 12 h, which is much higher activity than monometallic Cu/SiO2, Pt/SiO2 and other bimetallic Cu samples. Meanwhile, the used Cu–Pt/SiO2 catalyst still preformed high activity. Furthermore, it was found that the presence of Pt decreased the aggregation of particles during the hydrogenolysis of glycerol.

EFFECT OF SUPPORT MATERIALS ON CATALYTIC ACTIVITY OF NANO RUTHENIUM CATALYST IN HYDROGENOLYSIS OF GLYCEROL

A series of heterogenous catalysts based on supported ruthenium were prepared from RuCl3 precusor by impregnation method. The effect of support materials (bentonite, TiO2, Al2O3 and SiO2) on catalytic activity of Ru catalyst for hydrogenolysis of glycerol were investigated under mild reaction condition of 150C and 20 bar initial hydrogen pressure for 7 hours reaction time and glycerol concentration was 20%(wt). It was found that the type of support material have significant effects on the activity and selectivity of glycerol hydrogenolysis. The order of Ru catalyst activity was Ru/bentonite > Ru/Al2O3  Ru/TiO2 > Ru/SiO2. This study showed that bentonite supported Ru catalyst was the most active with glycerol conversion reaching 62.5% compared to other supports. All the tested catalyst exhibited high selectivity to 1,2-propanediol with more than 80%. Characterization of the catalysts was carried out using BET, XPS, FESEM-EDX and TEM to obtain the physicochemical properties of the catalysts.

Development of cerium promoted copper–magnesium catalysts for biomass valorization: Selective hydrogenolysis of bioglycerol

The selective hydrogenolysis of bioglycerol to 1,2-propanediol was investigated over a series of Ce-promoted Cu/Mg catalysts, namely, Cu/Mg (1/9), Cu/Ce/Mg (1/1/5), Cu/Ce/Mg (1/3/5), and Cu/Ce/Mg (1/5/5) prepared by a coprecipitation method. The physicochemical properties of the synthesized catalysts were analyzed by XRD, Raman, BET, BJH, XPS, NH3- and CO2-TPD, and H2-TPR techniques. The XRD and BET surface area results indicated that addition of Ce to Cu/Mg sample remarkably inhibits the crystal growth of CuO and improves the specific surface area. More number of oxygen vacancy defects were found in the Cu/Ce3/Mg sample, as evidenced from Raman studies. The reducible nature of the Cu/Mg sample was significantly enhanced after the Ce-incorporation. The NH3- and CO2-TPD results show that the acid–base properties of the Ce-promoted Cu/Mg samples are highly dependent on the Ce-loading. Among the synthesized samples, the Cu/Ce3/Mg sample exhibited higher concentration and superior strength of acidic sites. The achieved activity order of various catalysts for glycerol hydrogenolysis is Cu/Mg<Cu/Ce1/Mg<Cu/Ce3/Mg<Cu/Ce5/Mg. The high surface area, higher concentration of acid sites, abundant oxygen vacancies, and remarkable reducibility are found to be the key factors for the observed superior performance of the Cu/Ce3/Mg catalyst. Notably, the Cu/Ce3/Mg catalyst could be used multiple times for glycerol hydrogenolysis without considerable loss of activity.

Selective hydrogenolysis of glycerol to 1,2-propanediol catalyzed by supported bimetallic PdCu-KF/γ-Al2O3

Biomass glycerol is an important raw material for many available chemicals, such as 1,2-propanediol (1,2-PDO). Hydrogenolysis of glycerol to 1,2-PDO is considered as a sustainable process with renewable potential application. In this paper, a series of bimetallic PdCu-KF/γ-Al2O3 were prepared and the structures of catalysts were characterized by XRD, XPS, TEM and CO2-TPD. By measuring the activity of the catalyst, we found that PdCu-KF/γ-Al2O3 (Pd:Cu:KF=0.05:1:0.5) can be used as an efficient catalyst for hydrogenolysis of glycerol to 1,2-PDO, with 98.3% selectivity and nearly 100% conversion (200°C, 2.5MPa initial H2 pressure, 20h).

Influence of pretreatment on the catalytic performance of Ru/SBA-15 catalysts for glycerol hydrogenolysis

Ru/SBA-15 catalysts were prepared by impregnation and were pretreated under different conditions, and were characterized by N 2 adsorption-desorption, X-ray diffraction, CO chemisorption, transmission electron microscopy, and the reaction of glycerol hydrogenolysis. The catalyst calcined in air had larger Ru particles, while the direct reduction of the catalysts with H 2 without air pre-calcination made the Ru particles dispersed well. As the H 2 reduction temperature increased, the Ru dispersion decreased. The turnover frequency (TOF) of the catalysts increased as the Ru dispersion decreased, indicating that Ru/SBA-15 catalyzed glycerol hydrogenolysis is a structure sensitive reaction. Different treatment conditions gave Ru/SBA-15 catalysts with different Ru particle size, and they showed that glycerol hydrogenolysis over Ru/SBA-15 is a structure sensitive reaction.

Synergetic effect between Cu0 and Cu+ in the Cu-Cr catalysts for hydrogenolysis of glycerol

Active species of Cu-Cr catalysts, prepared by an epoxide-assisted sol–gel route, were investigated for the hydrogenolysis of glycerol to 1,2-propanediol. Structural characterization of the catalysts was performed by means of N2 physisorption, X-ray diffraction, H2-temperature programmed reduction, high-resolution X-ray photoelectron spectroscopy, NH3-temperature programmed desorption, and N2O titration. On the basis of the characterizations, the copper species on the calcined Cu-Cr catalysts and the reduced Cu-Cr catalysts were assigned. Combined with reaction results, it was found that there was not similar trend in copper metal surface area and glycerol conversion, indicating that a two-site (Cu0 and Cu+) mechanism existed in the hydrogenolysis of glycerol over Cu-Cr catalysts. Besides, the maximum conversion of glycerol was obtained when the surface Cu0/Cu+ ratio increased from 3.1 to 6.6, whereas decreased with increasing sequentially to 15.7, demonstrating that the appropriate surface Cu0/Cu+ ratio was required for optimum hydrogenation activity. Thus, the synergetic effect between the Cu0 and Cu+ was considered to be responsible for the high catalytic activity in the hydrogenolysis of glycerol, and that CuCr2O4 played a critical role in the glycerol hydrogenolysis reaction since it could function as a “hydrogen delivery bridge”.

Selective hydrogenolysis of glycerol to 1,2-propanediol over MgO-nested Raney Cu

Cu/MgO and MgO nested on the surface of Raney Cu were prepared by a wet-mixing method and used as catalyst for glycerol hydrogenolysis. The texture of Raney Cu/MgO was characterized by X-ray diffraction and transmission electron microscopy, Brunauer–Emmett–Teller, and CO2-temperature-programmed desorption techniques. Results indicated that MgO was well dispersed in the pores of Raney Cu. Moreover, Raney Cu with large specific surface area had a larger contact surface for MgO, and a new phase of Cu–MgO was produced. Glycerol hydrogenolysis was selectively catalyzed under the synergistic effect of Cu and MgO in Cu/MgO catalyst. Under the moderate conditions of 180 °C and 1 MPa H2, the conversion of glycerol was 36.2 wt% and the selectivity for 1,2-propanediol was ~85 wt% when chemical equilibrium.

A thermally stable and easily recycled core–shell Fe2O3@CuMgAl catalyst for hydrogenolysis of glycerol

Core–shell structured magnetic Fe2O3@CuMgAl layered double hydroxide (LDH) catalysts were synthesized in a facile route and used in selective hydrogenolysis of glycerol.

Effect of the functional groups of carbon on the surface and catalytic properties of Ru/C catalysts for hydrogenolysis of glycerol

Ruthenium catalysts supported on activated carbons, original (AC) and treated with nitric acid (AC-Ox) were prepared by incipient wetness impregnation from either chloride (Cl) or nitroxyl nitrate (n) precursors. These catalysts were characterized by TG, XPS, TEM, TPD-MS and CO adsorption microcalorimetry and evaluated in the hydrogenolysis of glycerol in the liquid phase, at 453K and 8MPa. Studies by TEM show that ruthenium particles supported on AC-Ox are larger than on AC, without any effect of the nature of the metal precursor. However, adsorption of CO on the ex-chloride catalysts is inhibited in comparison with that of the ex-nitroxyl nitrate catalysts. Catalysts characterization by TG, TPD-MS and XPS reveals that the nitric acid treatment and the nitroxyl nitrate precursor generate oxygenated groups on the carbon surface, which provide acid properties to the catalysts, although they are partly destroyed during the reduction treatment applied to the catalysts. The sequence of the overall TOF, Ru(Cl)/AC<Ru(n)/AC<Ru(Cl)/AC-Ox≈Ru(n)/AC-Ox, reasonably parallels the population increase of surface acid groups. Participation of the COOH groups in the transformation of glycerol into 1,2-propanediol is verified by using the admixture Ru(Cl)/AC+AC-Ox as catalyst. In this case, since AC-Ox was not thermally treated and no loss of oxygenated groups occurred, TOF and selectivity toward 1,2-propanediol improve in comparison with those of the more active catalysts.

Effect of Phosphorus on Structure and Performance of Cu/Al&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Catalysts for Hydrogenolysis of Glycerol

Effect of Phosphorus on Structure and Performance of Cu/Al&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Catalysts for Hydrogenolysis of Glycerol

Multiwall carbon nanotube-pillared layered Cu0.4/Mg5.6Al2O8.6: an efficient catalyst for hydrogenolysis of glycerol

Multiwall carbon nanotube (MWCNT)-pillared layered Cu0.4/Mg5.6Al2O8.6 material with doublet meso-pore channels and higher surface area was fabricated and used in hydrogenolysis of glycerol. The activity of surface Cu in MWCNTs–Cu0.4/Mg5.6Al2O8.6 hybrid is higher than those of Pd- and Rh-promoted Cu0.4/Mg5.6Al2O8.6 catalysts.

Cu/boehmite: A highly active catalyst for hydrogenolysis of glycerol to 1,2-propanediol

Small Cu clusters (~ 1 nm) were highly dispersed over boehmite via an aqueous chemical reduction method. In comparison with Cu/γ-Al2O3, Cu/SiO2 and Ru/C catalyst, Cu/boehmite catalyst showed the highest conversion and selectivity of 1,2-propanediol in the hydrogenolysis of glycerol. The good conversion and selectivity are ascribed to the small size of Cu metal clusters and the Lewis acid sites of boehmite, which provides high surface concentrations of active metal sites without CC bond cleavage activity and promotes the dehydration of glycerol to acetol as the intermediate of 1,2-propanediol, respectively.