Highest Glycerol Conversion Research Articles

Deciphering the imperative role of ruthenium in enhancing the performance of Ni/Nd2O3.Gd2O3 in glycerol dry reforming

Glycerol dry reforming (GDR) turns glycerol and CO2 into valuable syngas. The present work aims to decipher the imperative role of Ru metal in enhancing the performance of Ni/Nd2O3.Gd2O3 in GDR. The unpromoted 15%Ni/Nd2O3.Gd2O3 and promoted 3%Ru-Ni/Nd2O3.Gd2O3 catalysts are synthesized via the ultrasonic-assisted impregnation method while XRD, FESEM-EDX, H2-TPR and CO2-TPD analyses are used to characterize the catalysts. In this study, the influence of reaction variables such as temperature and the CO2 to glycerol ratio (CGR) was investigated. In accordance with XRD and FESEM-EDX analyses, the promoted catalyst exhibited a more refined morphology and more uniform Ni dispersion than the unpromoted catalyst. From the reaction study, the promoted 3%Ru-15%Ni/Nd2O3.Gd2O3 gives higher glycerol conversion (91%), H2 yield (65%) and CO yield (80%) at a reaction temperature of 800 °C and CGR of 1. This is due to the higher number of available active sites as well as the excellent diffusion of Ni metal across the surface of the catalyst. However, as Ni metal is susceptible to carbon formation and is easily sintered, the production of carbon is unavoidable for the catalysts. The XRD and TPO analyses shown that the addition of Ru reduces the amount of carbon that accumulates on the site of the catalyst, which in turn reduces the rate of deactivation.

Conversion of bio-glycerol to propylene glycol over basic oxides (MgO, La2O3, MgO-La2O3, CaO, and BaO2) supported Cu–Zn bimetallic catalyst: A reaction kinetic study

The effect of various basic oxide support (MgO, La2O3, CaO, BaO2) as a catalyst promoter on the performance of Cu–Zn bimetallic catalysts was investigated for selective conversion of glycerol to 1,2-propanediol (1,2-PDO) in an autoclave reactor. Various catalysts developed were characterized by different techniques and the physicochemical properties of the catalysts were correlated with the activity data and compared. Among the basic oxide-supported catalysts, Cu–Zn(4:1)/MgO demonstrated a very high glycerol conversion of 98.7% with a 92.2% yield of 1,2-PDO at 210 °C temperature and 4.5 MPa pressure. It was observed that after the incorporation of La2O3, glycerol conversion reached 100%, and 1,2-PDO yield marginally improved to 93.1%. It has been observed that the acidity/basicity, average crystallite size, H2-consumption, and the degree of reduction of the catalyst played an important role to improve the catalyst activity and 1,2-PDO yield. Further, a Langmuir–Hinshelwood–Hougen–Watson​ (LHHW) model was developed in presence of Cu–Zn(4:1)/MgO-La2O3 catalyst. The numerical solution of the model equation was computed with the help of the ode23 solver in MATLAB combined with a genetic algorithm (GA). Results demonstrated that the experimental concentrations of the reactant and products were very well correlated with the model predicted data. The calculated activation energy and frequency factor for the conversion of glycerol to 1,2-PDO were 69.6 kJ mol−1 and 4.2 × 107 mol gcat−1 h−1, respectively.

Heterogeneous Pt-Bi hybrid nanoparticle decorated self-standing hollow TiN nanowire as an efficient catalyst for glycerol electrooxidation

The electrochemical oxidation of glycerol is considered as a promising route to generate high value-added products. Rationally tuning the electronic structure of Pt catalysts by supporter and modifier is desirable for promoting the activity and stability of glycerol electrooxidation reaction (GEOR). In this work, we report Pt–Bi hybrid nanoparticles anchored hollow titanium nitride nanowires grew on carbon cloth (Pt1-x-Bix/TiN HNWs/CC (0≤ x ≤ 1)) as a self-supported monolithic electrode for efficient GEOR. Contributed by 3D porous nanotube structure, high corrosion resistance and conductivity of TiN, and strong electronic coupling effect of Pt, Bi, and TiN, the optimized Pt0.95-Bi0.05/TiN HNWs/CC electrode exhibits good catalytic activity and stability for GEOR. It shows a high peak current density of 88.4 mA cm−2 or 306.7 mA mgPt−1 in 0.05 M glycerol +1.0 M KOH solution. After continuous electrolysis for 8 h in 0.05 M glycerol +1.0 M KOH solution at a constant potential of 0.85 V versus reversible hydrogen electrode (vs. RHE), a high glycerol conversion of 87.0%, a moderate selectivity of 36.6% for glyceric acid, and a good stability were achieved, which is superior to other compared electrodes and most of the reported Pt–Bi catalysts.

Tuning the Product Selectivity toward the High Yield of Glyceric Acid in Pt−CeO2/CNT Electrocatalyzed Oxidation of Glycerol

AbstractElectrocatalytic oxidation of glycerol is a highly efficient way for upgrading glycerol toward fine chemicals. Currently, electro‐oxidation of glycerol into the high value‐added C3 products remains a big challenge because of the poor catalytic activity, low selectivity, and high cost of the noble metal catalysts, especially in the alkaline medium. Here, we report that the Pt−CeO2/CNT (CNT=carbon nanotubes) catalyst remarkably promotes the conversion (86.5 % vs. 37.6 %) and recycling stability for glycerol electro‐oxidation reaction, as compared with Pt/CNT. However, the improved catalytic activity of Pt−CeO2/CNT is accompanied by the further oxidation of C3 products including glyceric acid (GLYA). By tuning the product distribution by the ratio of CeO2 and CNT, applied potential, and the Pt loading amount, the high selectivities of C3 products (95 %) and GLYA (59 %) are achieved together with the high glycerol conversion (86 %), leading to the impressive yields of C3 products (81 %) and GLYA (50 %). The unique contributions of CeO2 includes not only the enhanced catalytic activity and recycling stability, but also the suppressed further oxidation of GLYA. Moreover, higher yield of GLYA is reached over Pt−CeO2/CNT even with half loading of Pt, as compared with Pt/CNT.

Investigating the effects of synthesis procedures on textural and catalytic properties of nickel/magnesium silicate catalyst in glycerol dry reforming

• The synthesis method affects the structural properties of the Ni/MgO.SiO 2 catalyst. • The structural features of the Ni catalyst affect catalytic performance significantly. • The Ni/MgO.SiO 2 catalyst prepared by one-pot method showed better performance. • The one-pot method has resulted in the highest textural properties of the Ni/MgO.SiO 2. Ni-based catalysts supported on magnesium silicate were synthesized using various synthesis procedures and were then investigated for the first time in the glycerol-DR (dry reforming) process. In general, synthesis procedures for catalyst supports included co-precipitation and hydrothermal, and nickel as active metal was attached to the support simultaneously with support preparing and impregnation technique. The results of characterizations of Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), hydrogen temperature-programmed reduction (TPR-H 2 ), temperature-programmed oxidation (TPO), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) element mapping, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA-DTA), and the catalytic glycerol-DR reaction tests illustrated that the preparation route of Ni/MgO.SiO 2 catalyst is effective in the structural and physicochemical features of the sample. It was observed that the catalysts with various synthesis methods exhibited different activity and stability during the glycerol-DR reaction. However, the highest glycerol conversion (31–50%) and the yield of both H 2 and CO were achieved over the Ni/MgO.SiO 2 (I) catalyst at all reaction temperature ranges (600–750 °C). The high catalytic performance of the Ni/MgO.SiO 2 (I) sample in the glycerol-DR reaction was related to its textural properties such as surface area (411 m 2 g −1 ), the crystallite size (8.5 nm), and active species dispersion, which were superior for this catalyst in comparison with other samples. This sample also exhibited better catalytic stability during the reaction. Furthermore, synthesis gas (syngas) was produced for all catalysts with an H 2 /CO ratio of less than 1.6. These results clearly show a significant impact of the sample synthesis procedure on the catalyst's final physical and chemical properties. The Ni/MgO.SiO 2 catalyst prepared with a one-step method showed high potential as a glycerol-DR catalyst for syngas production.

Evaluation of production processes of glycerol acetals using process intensification by flow chemistry

Currently, glycerol has been receiving great attention worldwide for being an important by-product formed during the production of biodiesel in high quantities, being considered, therefore, a very promising raw material for obtaining products with greater added value. Particularly, glycerol acetylation stands out for the glycerol acetals synthesis, which have application as fuel additives. However, in conventional processes, such reaction requires long times and significant acid excess in relation to glycerol. Based on that, the present work aims to apply process intensification, through millichannel reactor, for the acetylation reaction. The results obtained showed that the expressive area/volume ratio of the microreactors added to the high mixing efficiency allowed obtaining, in a few minutes (< 5 min), high glycerol conversions and high selectivities to diacetin. In general, the results showed that the acetals selectivities were directly influenced by the residence time and inversely influenced by the molar ratio of acetic acid/glycerol.

Selective Photoelectrocatalytic Glycerol Oxidation to Dihydroxyacetone via Enhanced Middle Hydroxyl Adsorption over a Bi2O3-Incorporated Catalyst.

Photoelectrocatalytic (PEC) glycerol oxidation offers a sustainable approach to produce dihydroxyacetone (DHA) as a valuable chemical, which can find use in cosmetic, pharmaceutical industries, etc. However, it still suffers from the low selectivity (≤60%) that substantially limits the application. Here, we report the PEC oxidation of glycerol to DHA with a selectivity of 75.4% over a heterogeneous photoanode of Bi2O3 nanoparticles on TiO2 nanorod arrays (Bi2O3/TiO2). The selectivity of DHA can be maintained at ∼65% under a relatively high conversion of glycerol (∼50%). The existing p-n junction between Bi2O3 and TiO2 promotes charge transfer and thus guarantees high photocurrent density. Experimental combined with theoretical studies reveal that Bi2O3 prefers to interact with the middle hydroxyl of glycerol that facilitates the selective oxidation of glycerol to DHA. Comprehensive reaction mechanism studies suggest that the reaction follows two parallel pathways, including electrophilic OH* (major) and lattice oxygen (minor) oxidations. Finally, we designed a self-powered PEC system, achieving a DHA productivity of 1.04 mg cm-2 h-1 with >70% selectivity and a H2 productivity of 0.32 mL cm-2 h-1. This work may shed light on the potential of PEC strategy for biomass valorization toward value-added products via PEC anode surface engineering.

Waste glycerol conversion on pilot scale continuous process by Al-modified mesoporous SiO2 catalysts

This work describes the conversion of the waste glycerol (as generated in the biodiesel industry, supplied by Petrobras) to valuable chemicals (such as formic acid, diglycerol, and dioxanes). The reactions were evaluated in batch and continuous-flow fixed-bed reactors (PBR) on a pilot scale using high porosity mesoporous silica (≈ 1500 m2 g−1) and Al-modified silica catalysts (SiAl = 15/1 and 5/1). The Al addition increased the acidity of the catalysts and reduced their surface areas (698 m2 g−1 in SiAl = 5). High glycerol conversion (80%) was reached for 15 Si/Al and 5 Si/Al whereas SiO2 tends to deactivate in a continuous-flow fixed-bed reactor (PBR). Furthermore, the catalysts exhibited different selectivity: SiO2 produced mainly formic acid (≈ 65% average) in the liquid phase whereas the Al-modified catalysts generated a large amount of diglycerol, possibly due to the different acidity of the catalysts. This study indicates the potential industrial use of the catalysts and contributes to increasing the sustainability of the biodiesel industry.

Glycerol Hydrogenolysis to Produce 1,2-Propanediol in Absence of Molecular Hydrogen Using a Pd Promoted Cu/MgO/Al2O3 Catalyst

The catalytic process of glycerol hydrogenolysis to produce 1,2-propandiol (1,2-PD) in the absence of external hydrogen addition has been investigated. The methanol present in the crude glycerol from a biodiesel production process is used to provide in situ hydrogen produced via methanol steam reforming for the glycerol hydrogenolysis process. This process can reduce the additional cost for the transportation and storage of molecular hydrogen and also reduce the safety risks related to using high hydrogen pressure. It was found that the introduction of Pd onto a Cu/MgO/Al2O3 catalyst significantly improved the glycerol conversion and 1,2-PD selectivity. The pseudo-first-order kinetic results suggested that the promoting effect of Pd is primarily attributed to the enhanced activity for the hydrogenation of acetol, which is the intermediate formed via glycerol dehydration. A 27−3 fractional factorial design experiment was carried out to investigate the impacts of seven single factors and their binary effects on two responses, namely 1,2-PD selectivity and glycerol conversion. The results showed that the glycerol feed concentration has the most significant effect on the 1,2-PD selectivity, such that the 1,2-PD selectivity is lower if a more concentrated glycerol is used as the feedstock; stirring speed, inert gas pressure and water to methanol molar ratio have insignificant effects on the reaction system. The addition of Pd, higher temperature and higher catalyst loading are the essential factors in order to obtain a high selectivity of 1,2-PD and a high glycerol conversion.

Ni-based catalysts supported on acid/alkali-activated coal fly ash residue for improved glycerol steam reforming

Application of coal fly ash (FA) residues as catalyst support is mainly restricted because of low surface area and high sulfur content. In the present work, the physicochemical properties of a low-efficiency FA were significantly improved via simple acid/alkali treatments consisting of one-step (HNO3 or NaOH) or two-step (NaOH/HNO3 or HNO3/NaOH) leaching-partial-dissolution (LPD). As a result, as compared to Ni-FA, the catalytic activity of the Ni-FA(treated) catalysts for glycerol steam reforming was considerably enhanced. Alkali-LPD is more effective than acid-LPD in simultaneously improving FA’s surface area and regulating FA’s elemental distribution. Ni-FA(HNO3/NaOH) has the best performance with high glycerol conversion to gas (99.2%) and H2 yield (74.5%), attributed to i) removal of sulfur-containing species by acid-LPD, ii) upgrading specific surface area, iron-exposure, and Ni dispersion via alkali-LPD, iii) diminishment of coke using acid/alkali-LPD sequence treatment, and iv) enhancement of catalytic stability due to the formation of NiFe alloys.

Hydrogenolysis of glycerol to 1,3-propanediol over H-ZSM-5-supported iridium and rhenium oxide catalysts

The hydrogenolysis of glycerol to 1,3-propanediol (1,3-PrD) over Ir-ReOx catalysts supported on H-ZSM-5 (denoted as Ir-ReOx/H-ZSM-5) was investigated. The glycerol conversion and 1,3-PrD yield strongly depended on the catalyst composition (Re/Ir) and the amount of metal loading. The analyses of the catalysts using X-ray powder diffraction and transmission electron microscopy revealed that a higher metal dispersion of Ir and a smaller Ir particle were encouraged by the addition of Re to the catalyst. Furthermore, a strong electronic interaction between Ir and Re in the Ir-ReOx/H-ZSM-5 catalyst was observed from X-ray photoelectron spectroscopy measurements. In the study on the effects of operating conditions, increasing the temperature and reaction time resulted in a higher glycerol conversion at the expense of 1,3-PrD selectivity due to over-hydrogenolysis, whereas increasing the pressure had a positive effect on 1,3-PrD selectivity. The highest 1,3-PrD yield observed was achieved at 2.8% with 14.9% glycerol conversion and 19.0% 1,3-PrD selectivity.

Role of preparation parameters of Cu–Zn mixed oxide catalyst in solvent free glycerol carbonylation with urea

Solvent-free carbonylation of glycerol with urea to glycerol carbonate (GC) was achieved over heterogeneous Cu–Zn mixed oxide catalyst. Cu–Zn catalysts with different ratios of Cu:Zn were prepared using co-precipitation (CP) and oxalate gel (OG) methods. As compared to CuO–ZnO(2:1) catalyst prepared by oxalate gel (OG) method, much higher conversion of glycerol and highest selectivity towards glycerol carbonate (GC) was achieved with CuO–ZnO_CP(2:1) catalyst. Physicochemical properties of prepared catalysts were investigated by using XRD, FT-IR, BET, TPD of CO2 and NH3 and TEM techniques. The effect of stoichiometric ratio of Cu/Zn, calcination temperature of CuO–ZnO catalysts and effect of reaction parameters such as molar ratio of substrates, time and temperature on glycerol conversion to GC were critically studied. Cu/Zn of 2:1 ratio, glycerol–urea 1:1 molar ratio, 145 ​°C reaction temperatures were found to be optimized reaction conditions to achieve highest glycerol conversion of 86% and complete selectivity towards GC. The continuous expel of NH3 from reaction the mixture avoided formation of ammonia complex with CuO–ZnO catalyst. As a result of this, CuO–ZnO catalyst could be recycled up to three times without losing its initial activity.

Tungsten-doped siliceous mesocellular foams-supported platinum catalyst for glycerol hydrogenolysis to 1,3-propanediol

By varying the mass ratio of the swelling agent 1,3,5-trimethylbenzene (TMB) to the template P123 during the synthesis of the W-MCFs, we prepared a series of tungsten-doped siliceous mesocellular foams (W-MCFs) supported Pt catalysts (Pt/W-MCFs). In glycerol hydrogenolysis, the Pt/W-MCFs catalysts were highly active and selective to 1,3-propanediol (1,3-PDO), attributable to the 3-dimensional continuous large pore structure of the W-MCFs that facilitates the entry of the reactant and the escape of the product. Among the Pt/W-MCFs catalysts, the Pt/W-1.5MCFs catalyst with the TMB/P123 ratio of 1.5 exhibited the best activity and 1,3-PDO selectivity. Remarkably, the Pt/W-1.5MCFs catalyst afforded a high 1,3-PDO selectivity of 65 % at high glycerol conversion, thus rendering the highest 1,3-PDO yield of 63 %. The synergy between the Pt nanoparticles and the single-sited tetrahedral WVO4 species at the metal–oxide interface is proposed to be responsible for the differences in the catalytic performances among the Pt/W-MCFs catalysts.

Co-production of hydrogen and syngas from chemical looping water splitting coupled with decomposition of glycerol using Fe-Ce-Ni based oxygen carriers

In this study, chemical looping water splitting (CLWS) coupled with glycerol decomposition to simultaneously produce hydrogen and syngas was proposed using the iron-cerium-nickel (Fe-Ce-Ni) based oxygen carriers (OCs). The OCs containing large amounts of iron were synthesized by the metal chelating sol–gel method and characterized by BET, XRD and TEM. During the fuel stage, the OCs of oxidation state were first reduced by the glycerol and reactive gases from catalytic decomposition of glycerol producing syngas. Afterward in the subsequent steam stage, the previously reduced OCs were re-oxidized by the steam to generate pure hydrogen, which was also named the steam iron process (SIP). The prepared Fe-Ce-Ni based OCs demonstrated the remarkable redox behavior, and exerted an important catalytic function of the partial oxidation and decomposition of glycerol at 750 ℃. The OCs with 100:10:3 of Fe-Ce-Ni molar ratio presented the best capability of oxygen transfer and the highest yields of hydrogen and syngas, reaching the water splitting hydrogen production of 11.79 mmol/g per cycle on average and guaranteeing the high conversion of glycerol and selectivity of syngas. This could be ascribed to the preferable dispersion of Ce and Ni nanoparticle on the OCs. The results also proved the effectiveness of Ce and Ni doping Fe based OCs by the improved metal chelating sol–gel method to develop the catalysts with high activity and stability for co-production of hydrogen and syngas from CLWS coupled with glycerol decomposition.

Promoting the Effect of Au on the Selective Hydrogenolysis of Glycerol to 1,3-Propanediol over the Pt/WOx/Al2O3 Catalyst

The selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PDO) is an important yet challenging reaction because it requires the selective cleavage of the sterically hindered secondary C–O bond of glycerol. In this work, we have developed a new catalyst, 0.1Au-2Pt/7.5W/Al, which affords both high glycerol conversion (77.5%) and 1,3-PDO selectivity (54.8%), which are significantly higher than the Au-free counterpart. HAADF-STEM reveals that the structure of 0.1Au-2Pt/7.5W/Al is characterized with ∼2 nm Pt NPs decorated with Au-WOₓ at the periphery, where the Au additive exists most likely as single atoms. Chemisorption and XPS show that the electron transfer from W to Au can help to weaken the strong metal support interaction (SMSI) between Pt and WOₓ, and thus greatly enlarges the exposed Pt surface and increases the H-spillover capacity. The 2-butanol dehydration in H₂ reveals that the H-spillover capacity is proportional to the number of Bronsted acid sites, which, in conjunction with the only water desorption in H₂-TPD results, strongly suggests that the active sites for breaking the secondary C–O bond of glycerol should be Bronsted acid sites generated by the H-spillover at the interface between Pt and WOₓ, and the modification by the Au additive increases the number of interfacial sites, and thus enhances the 1,3-PDO yield.

Enhance glycerol conversion through co-etherification with isobutene and tert-butanol

tert-Butyl glycerol ethers obtained from etherification of glycerol with isobutene or tert-butanol are desirable fuel additives. While glycerol etherification with isobutene has high glycerol conversion and yield to the desired ethers, it undergoes intricate interphase mass-transfer and the rate is restricted by the low reactant concentration resulting from phase separation. On the contrary, although glycerol etherification with tert-butanol avoids phase separation, the conversion and yield are relatively low due to equilibrium limitation and/or the inhibition from the produced water. We proposed to etherify glycerol with isobutene and tert-butanol simultaneously (co-etherification) to enhance glycerol conversion. Multiphase chemical equilibrium was calculated to explore the phase states of reaction mixtures as well as the equilibrium conversions and yields under a wide range of conditions. The co-etherification was then demonstrated on NKC-9 catalyst, which validated that the solvation function of tert-butanol to the glycerol-isobutene mixture improved the glycerol conversion rate (up to twice). Isobutene addition raised glycerol conversion and yield to the poly-substituted ethers comparing with the etherification with tert-butanol. Co-etherification (G:IB:TBA = 1:3:1) yielded 0.573 poly-substituted ethers at 353 K, while the yield was only 0.069 in the G-TBA etherification (G:TBA = 1:4). Moreover, the presence of tert-butanol effectively hindered the undesired isobutene dimerization.

Effect of different supports for copper as catalysts on glycerol hydrogenolysis to 1,2-propanediol

In this work, several copper supported catalysts, Cu/Dol, Cu/Al2O3, Cu/Bent, Cu/Mont, and Cu/Talc were prepared using wet impregnation route and characterized using BET, BJH, XRD, H2-TPR, NH3–TPD, and SEM analytical techniques and subsequently tested in hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). The nature of support was found to determine the activation of the catalysts. Among the tested catalysts, dolomite supported copper catalyst (Cu/Dol) exhibited superior performance due to the copper and dolomite species mutual interaction. The findings from the various characterization tests showed that the presence of copper species were essentially enriched on the dolomite grain surfaces, the redox properties, and acidic property of the catalyst enhanced, as well as the formation of the small size of the catalyst (Cu/Dol) contributed to the high conversion of glycerol (78.5%) and high 1,2-PDO selectivity (79%) with low methanol production as the by-product at 200 °C, 4 MPa H2 and 10 h reaction conditions.

Conversion of Glycerol to Value Added Products in a Semi-Continuous Batch Reactor Using Noble Metals Supported on ZSM-11 Zeolite.

Au, Pt, and Pd supported on ZSM-11 microporous zeolite were investigated as catalysts for glycerol (GLY) oxidation towards higher value added products. ZSM-11 was synthesized by hydrothermal treatment. Subsequently, ion exchange with NH4Cl was performed to recover acidic sites and then, Au, Pt, and Pd were incorporated onto this material by wet impregnation procedure. After thermal treatment of desorption and calcination, the corresponding Au, Pt, and Pd-ZSM-11 catalysts were obtained. These materials were characterized by different techniques, such as XRD, ICP, TEM- XEDS, and XPS, and were evaluated in the glycerol oxidation reaction by using alkaline medium and molecular oxygen as oxidizing agent. The higher conversion of GLY (66.5 mol.%) was reached for the Pt–ZSM-11 catalyst with moderate selectivity towards lactic acid (LA), while the bimetallic Au-Pt-ZSM-11 catalyst offered high selectivity to LA at moderate GLY conversion. Optimization of the main reaction parameters (i.e., temperature, reaction time and NaOH/GLY ratio) was carried out to maximize the selectivity towards the LA desired product. Thus, LA selectivity values close to 55% at GLY conversion >65% can be reached by using Pt-ZSM-11 as a catalyst under mild reaction conditions.

Easily Recycled CuMgFe Catalysts Derived from Layered Double Hydroxides for Hydrogenolysis of Glycerol

A series of CuMgFe catalysts with different (Cu + Mg)/Fe molar ratios derived from hydrotalcites were prepared by coprecipitation for the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), vibrating sample magnetometer (VSM), hydrogen temperature-programmed reduction (H2-TPR), CO2-TPD, and H2-TPD (temperature-programmed desorption of CO2 and H2) were used to investigate the physicochemical properties of the catalysts. The CuMgFe-layered double oxides (CuMgFe-4LDO) catalyst with (Cu + Mg)/Fe molar ratio of 4 exhibited superior activity and stability. The high glycerol conversion and 1,2-propanediol selectivity over CuMgFe-4LDO catalyst were attributed to its strong basicity, excellent H2 activation ability, and an increase in the surface Cu content. The CuMgFe catalysts could be easily recycled with the assistance of an external magnetic field due to their magnetism.

Promotional effect of transition metals (Cu, Ni, Co, Fe, Zn)–supported on dolomite for hydrogenolysis of glycerol into 1,2-propanediol

Hydrogenolysis of biomass-derived glycerol is an alternative route to produce 1,2-propanediol. A series of transition metals supported on dolomite catalysts (Cu/Dol, Ni/Dol, Co/Dol, Fe/Dol, Zn/Dol) were prepared via impregnation, calcined at 500 °C and reduced at 600 °C. The synthesized catalysts were then characterized by BET, BJH, XRD, H2-TPR, NH3–TPD, and SEM, and subsequently evaluated in glycerol hydrogenolysis reaction to produce 1,2-propanediol (1,2-PDO). The nature of transition metals was found to influence the activation of the catalysts. Among the tested catalysts, copper supported on dolomite (Cu/Dol) exhibited appreciable hydrogenolysis performance due to the mutual interaction between the copper species and the dolomite. The findings from the various characterization results showed the addition of copper to dolomite ameliorates the chemical and reduction of the catalyst. It appears that the copper species were essentially enriched on the grain surfaces of the dolomite, the reduction properties, and the acidity of the catalyst enhanced. All the features of Cu/Dol catalyst contributed to the high glycerol conversion (78.5%) and high 1,2-PDO selectivity (79%) with low methanol production as the by-product at 200 °C of reaction temperature, 4 MPa of reaction pressure and 10 h of reaction time.