Glycerol Dehydration Research Articles

Synergistic Effects of Nonthermal Plasma and Solid Acid Catalysts in Thermo-Catalytic Glycerol Dehydration

To enhance the bio-based synthesis of acrolein from glycerol, a hybrid approach combining in situ nonthermal plasma (NTP) with thermo-catalytic dehydration was employed. This study investigated the impact of the reaction temperature and NTP discharge field strength on glycerol conversion, acrolein selectivity, byproduct formation, and coke deposition using two catalysts of silicotungstic acid supported on mesoporous alumina and silica. The results revealed that, while the reaction temperature and NTP field strength exhibited complex interactions, the in situ application of NTP markedly improved both glycerol conversion and acrolein selectivity when optimized for specific temperature–NTP field strength combinations. Additionally, the reaction mechanisms of glycerol dehydration with the two catalysts, in the presence and absence of NTP, were systematically analyzed and discussed based on the experimental data.

Influence of WO3 Content in Phosphated Tungsten-Zirconium Oxide Catalysts on the Catalytic Pathways of Glycerol Transformation.

The catalytic performance of phosphate-stabilized WOx-ZrO2 compositions in gas-phase glycerol dehydration has been investigated. Results show that varying WO3 concentrations direct the process towards either acrolein or allyl alcohol formation. Catalysts with low WOx content exhibit strong Lewis acid sites (Zr4+ and W6+), where these metal ions likely function as redox sites, facilitating glycerol hydrogenolysis to produce allyl alcohol. Higher WO3 concentrations (exceeding 20 wt.%) lead to the shielding of some W6+ and Zr4+ sites by polytungstate surface complexes, which are strong Brønsted acid sites. This alteration promotes glycerol dehydration through the removal of two water molecules, thereby shifting the selectivity towards acrolein formation.

Evaluation of two acrylic acid production processes from renewable crude glycerol: Rigorous process design, techno-economic evaluation, and life cycle assessment

This study aims to propose and evaluate two acrylic acid (AA) production processes that utilize bio-based crude glycerol as a feedstock. Scheme 1 employs acrolein as an intermediate, while Scheme 2 utilizes allyl alcohol as an intermediate. For process intensification, Scheme 1 employs a one-pot reactor configuration that couples the glycerol dehydration and oxidation reactions and uses an additional reactor to suppress the formation of side products. Scheme 2 implements a membrane that helps prevent the multiple azeotropic distillation between water and other substances. Furthermore, both processes were systematically optimized based on varying levels of information available in the process (i.e., three objectives for Scheme 1, single objective for Scheme 2). From a techno-economic evaluation, Scheme 2 (2.136 USD/kg) slightly outperforms Scheme 1 (2.514 USD/kg) in terms of the minimum required selling price (MRSP). Both values are significantly higher than the market price (1.24–1.32 USD/kg) based on the conventional process that uses propene as a feedstock. Subsequently, a cradle-to-gate life cycle assessment was conducted to compare these processes across five impact categories (i.e., global warming potential, fossil source scarcity, human non-carcinogenic toxicity, water consumption, and terrestrial acidification). We have observed that Scheme 1 can be more sustainable than Scheme 2 and the conventional process if the issue associated with the acrolein left in the wastewater can be addressed. In contrast, Scheme 2 is far from environmentally friendly even compared to the conventional process, primarily because of the use of formic acid as a co-reactant.

Hierarchical EMT structured zeolites as improved catalysts for glycerol dehydration

A fast and simple post-synthesis method for creating secondary mesoporosity in EMT zeolites was developed using an ammonium fluoride / cetyltrimethylammonium bromide (NH4F/CTAB) solution at low temperature with ultrasound irradiation. This strategy is shown to be highly effective for producing hierarchical EMT structured zeolites through the etching of both Si and Al species. The catalytic performance of these materials were assessed using glycerol dehydration as a reaction test, which is in addition a relevant reaction due to the high amounts of glycerol generated as a by-product of biodiesel production. The resulting hierarchical EMT structured zeolites exhibited improved catalytic activity and high selectivity towards acrolein (around 80 %). This innovative approach creates new opportunities for using hierarchical EMT structured zeolites in processes related with biodiesel manufacture.

Unraveling High Chemoselectivity in Oxidative Dehydration of Glycerol into Acrylic Acid over a Bifunctional Metal–Organic Framework–Polyoxometalate Composite Catalyst

Unraveling High Chemoselectivity in Oxidative Dehydration of Glycerol into Acrylic Acid over a Bifunctional Metal–Organic Framework–Polyoxometalate Composite Catalyst

Influence of the Calcination Atmosphere on Copper-Aluminum Catalysts for the Selective Dehydration of Glycerol

The present work studied the influence of two atmospheres (air or N2) in the calcination step at 500 ºC on catalysts based on copper and aluminum with a 28 mol% of Cu. The catalysts were characterized and tested in gas-phase reactions for the selective dehydration of glycerol into acetol.

Alejandro Lete - Influence of the Calcination Atmosphere on Copper-Aluminum Catalysts for the Selective Dehydration of Glycerol

Alejandro Lete - Influence of the Calcination Atmosphere on Copper-Aluminum Catalysts for the Selective Dehydration of Glycerol

Synergistic effects on Cu, Zn and Al-based catalyst: tracking the change of active sites during glycerol dehydration

Synergistic effects on Cu, Zn and Al-based catalyst: tracking the change of active sites during glycerol dehydration

SiO2-coated HZSM-5 catalysts for dehydration of bio-based glycerol to acrolein

As biodiesel production from triglyceride transesterification increases, by-product glycerol is accumulated, motivating the development of novel mechanism for converting glycerol into valuable chemicals. In the present work, for the selective production of acrolein from glycerol, SiO2-coated HZSM-5 molecular sieve with preciously controlled surface was designed. As characterized by NH3-TPD and pyridine adsorption IR, the total acid and the Lewis acid amounts of SiO2-coated HZSM-5 were decreased whereas the Brønsted acid amount remained almost unchanged. SiO2-coated HZSM-5 catalyst exhibited selectivity to acrolein of 64%, in glycerol conversion of 100% under reaction temperature of 300°C, much higher than HZSM-5 catalyst with acrolein selectivity of 52%. The catalytic activity durability was also improved by the modification of the surface properties because SiO2 coating reduced the surface acid amount and the micropore volume of HZSM-5, suppressing side reactions and inhibiting carbon deposition efficaciously.

In-depth analysis of embedded-type structures of NixMg4-xAl LDO-composited catalysts and the impacts on glycerol conversion under a base- and H2-free condition

Core-shell composite catalysts composing of AgO@SnO2/ZSM-5 embedded by NixMg4-xAlO LDOs with various Ni/Mg ratios were characterized and tested for the activity on the conversion of glycerol to valuable chemicals under a base-free and external H2-free condition. As a result, the catalytic performance of an embedded composite was found greater than that of its individual constituents, owing to the synergy between a NixMg4-xAlO lodge and embedded AgO@SnO2/ZSM-5. The highest yield of 1,2-propanediol and lactic acid was achieved at the Ni/Mg ratio of 0.2/3.8. NixMg4-xAlO lodges were found to simultaneously drive glycerol dehydration to acetol and glycerol reforming, driven by Ni sites, forming in-situ H2 that enhances 1,2-propanediol formation whereas the AgO@SnO2/ZSM-5 clusters governed acetol oxidation and Cannizzaro reaction that led to the formation of lactic acid. At a high Ni/Mg ratio, the NixMg4-xAlO lodges completely covered AgO@SnO2/ZSM-5 clusters entirely, resulting in the suppression of lactic acid yield due to over-oxidation.

The effect of Ni- and Mo-based materials on thermochemical sulfate reduction by glycerol under hydrothermal process conditions

Catalytic hydrothermal gasification (cHTG) is a sustainable and promising route to convert wet biomass into renewable methane, but the catalyst is deactivated by small amounts of soluble sulfate stemming from the biomass feedstock. Under hydrothermal conditions, sulfate can be converted to the strong catalyst poisons thiols or sulfides by thermochemical sulfate reduction (TSR). In this work, we explored the extent to which TSR occurs under conditions relevant to cHTG operation, along with the impact of various materials on the reaction. Our results indicated that within 60 min, an aqueous solution of 20 wt% glycerol and 10 mM potassium sulfate at 25 MPa started to produce organosulfur compounds at ca. 420–440 °C, with yields for the volatile ones of 3% and 6% at 440 °C and 490 °C, respectively. The main products were non-volatile organosulfur compounds (NVOSC), which were tentatively identified as sulfate esters of glycerol or of glycerol decomposition products. A smaller fraction of products consisted of volatile organosulfur compounds (VOSC). The VOSC identified from the TSR with glycerol were mostly alkyl thiophenes, as well as methanethiol, disulfides and trisulfides with no evidence of H2S formed. Ni-, Mo-, or NiMox-based materials did not show any catalytic effect on sulfate reduction, independent of the sulfidation of the material. Glycerol was proven to be much more reactive towards TSR than acetone, as no TSR products could be observed when acetone was used as a reducing agent. A reaction pathway for the formation of thiophenes from H2S and glycerol is proposed that consists of the dehydration of glycerol, the formation of CO and H2 from glycerol decomposition, hydroformylation of acrolein, and the Paal-Knorr synthesis with succinaldehyde and H2S as intermediates.

Cu/ZrO2 Catalyst Modified with Y2O3 for Effective and Stable Dehydration of Glycerol to Acetol.

Glycerol is a main by-product of biodiesel production, and its further processing is essential for the biorefinery. In this paper, a highly active and stable catalyst for the catalytic dehydration of glycerol to acetol is obtained by modifying a Cu-Zr (ZrO2 supported Cu) catalyst with Y2O3 using a co-precipitation method. It is found that the addition of Y2O3 effectively enhances the catalytic performance of Cu-Zr. Cu-Zr reaches the highest selectivity (82.4%) to acetol at 24 h. However, the selectivity decreases to 70.1% at 36 h. The conversion also decreases from 99.2 to 91.1%. Cu-Zr-Y exhibits very high activity and very good stability. During a 250 h reaction, no deactivation is observed, and the conversion and selectivity remains ~100% and ~85%, respectively. The catalysts are characterized by XRD, TEM, H2-TPR, and NH3-TPD. The results reveal that Y2O3 not only improves the dispersion of Cu and the acidity of the catalyst but also restrains the agglomeration of Cu particles and assists retaining the main structure of support under reaction conditions. The high dispersion, high acidity content, and stable structure contributes to the excellent catalytic performance of Cu-Zr-Y.

Vapor-phase dehydration of glycerol to acetol over Cu/SiO2 prepared with organic additives

Silica-supported Cu (Cu/SiO2) catalysts prepared with organic additives showed excellent activity for the dehydration of glycerol to acetol. Among eight organic additives tested, 12-crown-4-ether (12C4) contributed the highest improvement in the activity of Cu/SiO2 catalyst. The catalytic dehydration of glycerol to acetol was accompanied by the formation of glyceraldehyde via dehydrogenation. The enlargement of Cu surface area was limited by the pore volume of SiO2 support. Acetol was the dominant product over Cu catalysts at high glycerol conversions, and the highest acetol yield of 94.3% was achieved over 12C4-Cu/SiO2 at 270 °C. The Cu surface area was proportional to the formation rate of acetol in the dehydration of glycerol at 200 °C. Consequently, we concluded that the glycerol dehydration was not catalyzed by the Lewis acid sites but catalyzed by Cu0 nanoparticles dispersed on SiO2 support.

Studies on a niobia-supported VPO catalyst for glycerol dehydration

Niobia-supported VPO catalysts were synthesized using the deposition–precipitation method with different VPO loadings to evaluate glycerol dehydration. The activity patterns are consistent with the acidity trends.

Structure–reactivity relations in Cu/ZrO2 catalysed glycerol dehydration to acetol in continuous flow

Selective dehydration of glycerol to acetol was successfully catalysed by Cu/m-ZrO2 with monoclinic zirconia preferentially stabilising the more active Cu(i) species.

Combining structure design and surface modification of BPO4 solid acid catalyst to boost the anti-coking performance in dehydration reaction of glycerol

Catalytic vapor-phase dehydration of glycerol is an energy-efficient and environmentally friendly route for producing acrolein, a valuable organic chemical intermediate. However, anti-coking is one of the key problems due to the excessively acid catalytic sites and sluggish mass transfer, restricting the industrial application of this reaction. Herein, potassium element modified BPO4 monolithic foams with the hierarchically porous structure were synthesized by adding potassium element in the gel precursor of BPO4. The catalyst introducing 3% K exhibited the best acrolein selectivity of 81.0% with nearly complete glycerol conversion. In a 10-hour run of the reaction at 320 °C, the selectivity of acrolein could remain at 75.9% with 94.5% glycerol conversion, indicating the superior stability. The excellent activity and stability for 3% K-BPO4 is mainly attributed to the synergetic effect between hierarchical structure providing favorable mass transfer and appropriate acid catalytic sites inhibiting over dehydration reaction. They not only boost activity but also reduce coking, providing a unique approach for the design of solid acid catalyst.

Valorization of glycerol through plasma-induced transformation into formic acid.

To cope with climate change issues, a significant shift is required in worldwide energy sources. Hydrogen and bioenergy are being considered as alternatives toward a carbon neutral society, making formic acid-a hydrogen carrying product of glycerol-of interest for the valorization of glycerol. Here we investigate the plasma-induced transformation of glycerol in an aqueous nanosecond repetitively pulsed discharge reactor. We found that the water content in the aqueous mixture fulfilled a crucial role in both the gas phase (as a source of OH radicals) and the liquid phase (as a promotor of the dissolved OH radical's mobility and reactivity). The formic acid produced was linearly proportional to the specific input energy, and the most cost-effective production of formic acid was found with 10-%v/v glycerol in the aqueous mixture. A plausible reaction pathway was proposed, consisting of the OH radical-driven dehydrogenation and dehydration of glycerol. The results provide a fundamental understanding of plasma-induced transformation of glycerol to formic acid and insights for future practical applications.

Acidic property and gas-phase glycerol-dehydration activity of WO3/Al2O3 catalysts

The acidic property of WO3/Al2O3 catalysts loaded with WO3 (5–37 wt%) and their activity for gas-phase glycerol dehydration were investigated. Temperature-programmed desorption of NH3 revealed the formation of weak acid sites (the enthalpy of NH3 desorption; ΔHNH3 <110 kJ mol–1) on WO3/Al2O3. Infrared spectra of adsorbed pyridine indicated that a part of Lewis acid sites of WO3/Al2O3 was converted to Brønsted acid sites by water vapor treatment. The ΔH‡–ΔS‡ relationship for glycerol dehydration over WO3/Al2O3 and H-ZSM-5 indicated a weaker interaction of WO3/Al2O3 catalyst with the reaction intermediate than that of H-ZSM-5. The coke species deposited over WO3/Al2O3 and H-ZSM-5 were confirmed to consist of C3–C4 compounds, acrolein, benzene, toluene, xylene, glycerol, indenes, naphthalenes, and anthracenes (or phenanthrenes); fewer polyaromatic compounds were formed over WO3/Al2O3. For WO3/Al2O3, the weak acid strength of the Brønsted acid sites resulted in high durability for glycerol dehydration.

Glycerol dehydration catalyzed by solid acid in nonthermal plasma and simulation analysis of plasma electric field

AbstractNonthermal plasma (NTP), for the first time, was integrated in glycerol dehydration reaction catalyzed by silicotungstic acid supported on mesoporous silica with argon as the carrier and discharge gas. A range of reaction temperatures (220–320°C) and NTP discharge field strengths (2.06–6.87 kV/cm) were studied for the individual and interactive effects regarding the glycerol conversion and product selectivity. Results showed that the presence of NTP always improved the glycerol conversion, and NTP increased acrolein selectivity if properly conditioned. An optimal condition of 275°C and 4.58 kV/cm NTP field strength achieved a glycerol conversion of 94.4 mol%, acrolein selectivity of 88.0 mol%, with an acrolein yield of 83.1 mol%, representing a 10% improvement in acrolein production over that conducted at the same temperature but without NTP. Results of this study will also have significant implication for other heterogeneously catalyzed dehydration reactions. Simulation of the high‐voltage electric field distribution as function of NTP electrical conductivity and relative permittivity of catalyst materials also offers insight for the future design of reactors and catalysts.

Photoinduced Biomimetic Room-Temperature C-O Bond Cleavage over Mn Doped CdS.

Selective C-O bond cleavage is an efficient way for the biomass valorization to value-added chemicals, but is challenged to be operated at room temperature via conventional thermal catalysis. Herein, inspired from the DNA biosynthesis which involves a radical-mediated spin-center shift (SCS) C-O bond cleavage process, we report a biomimetic room-temperature C-O bond cleavage of vicinal diol (HOCHCH-OH). We construct a Mn doped CdS (Mn/CdS) as a photocatalyst to mimic the biologic SCS process. The Mn site plays pivotal role: (1) accelerates the photo-induced carrier separation, promoting the hole-mediated C-H bond cleavage to generate carbon-centered radicals, and (2) serves as the binding site for -OH groups, making it to be an easier leaving group. Mn/CdS achieves 0.28 mmol gcat -1 h-1 of hydroxyacetone (HA) from glycerol dehydration at room temperature under visible light irradiation, which is 3.5-fold that over pristine CdS and 40-fold that over bulk MnS/CdS. This study provides a new biomimetic room-temperature C-O bond cleavage process, which is promising for the biomass valorization.