Vapour Phase Dehydration Of Glycerol Research Articles

Catalytic dehydration of glycerol to acrolein over mesoporous MCM-41 supported heteropolyacid catalysts

A series of vanadium substituted phosphomolybdic acid (VPMA) supported on mesoporous MCM-41 catalysts with varying VPMA content ranging from 10 to 50 wt% were prepared by impregnation method. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy, N2 adsorption–desorption measurements to determine surface area and pore size distribution. The acidity measurements were studied by temperature programmed desorption (TPD) of NH3 and nature of acidic sites were examined by pyridine adsorbed FT-IR spectra. XRD results and N2 adsorption–desorption isotherms revealed the retention of ordered mesoporous structure of MCM-41 and the uniform pore structure with increase in HPA loading. FT-IR and Raman spectra showed that the primary structure of the Keggin units of the VPMA remains intact with the MCM-41. The TPD-NH3 showed that acidity of the catalysts increased with increase of VPMA loading. The findings of FT-IR spectra of pyridine adsorption revealed that VPMA/MCM-41 catalysts contain both the Bronsted and Lewis acidic sites and the amount of Bronsted acidic sites increased with increase of VPMA loading up to 40 wt% on the support. The catalysts were tested for the vapour phase dehydration of glycerol to acrolein. The catalyst samples were found to be highly active with 100% conversion and the acrolein selectivity changed with VPMA active phase loading on the support. In summary, the catalytic properties in terms of conversion and selectivity are attributed to the acidity, structural and textural properties of VPMA/MCM-41 catalyst.

Metal Phosphates: Preparation, Characterization and Catalytic Evolution for Vapour Phase Dehydration of Glycerol to Acrolein

Metal phosphate (MP; M = Al, Ti, Zr and Nb) catalysts have been examined for the continuous dehydration of glycerol to acrolein and hydroxyacetone. These catalysts are prepared by hydrothermal procedure and the physico-chemical characteristics were probe by XRD, N2 sorption, FT-IR, UV-DRS, ex-situ Py-FT-IR and TPD-NH3 to gain the insight effect of the samples structural and superficial acidity with changing the metal component. The glycerol dehydration activity will be interpreted with respected to the acidity and skeletal behavior of the MP catalysts. The outcomes indicated that the NbP was the best catalyst, achieving 100% glycerol conversion, followed by TiP, ZrP and AlP. However, due to its expanded porosity, TiP catalyst proved its long life activity during vapor phase glycerol dehydration.

Vapour Phase Dehydration of Glycerol to Acrolein Over Wells-Dawson Type H6P₂W18O62 Supported on Mesoporous Silica Catalysts Prepared by Supercritical Impregnation.

The H6P2W18O62/MCM-41-SUP was first synthesized using supercritical impregnation as highly efficient catalyst during glycerol conversion reaction. For comparison, the H6P2W18O62/MCM-41 prepared by conventional wet impregnation was also studied. The catalysts were studied using XRD, BET, FTIR, SEM, TEM, pyridine-FTIR, NH3-TPD, TG, ICP and elemental analysis. The characterization results showed that the preparation condition of supercritical carbon dioxide contributed to improve the dispersion of H6P2W18O62 on MCM-41, strengthen the interaction between H6P2W18O62 and MCM-41, increase the thermostability of H6P2W18O62 and enhance the amount of medium and Brønsted acid sites on the catalyst. Therefore, the formation of coke was retarded, and the lifetime of catalyst was prolonged. After 15 h reaction, the glycerol conversion rapidly reduced from 92% to 64% on H6P2W18O62/MCM-41-IMG (15.4 wt% coke), while the glycerol conversion slightly decreased from 94% to 82% on H6P2W18O62/MCM-41-SUP (9.8 wt% coke).

Vapor Phase Dehydration of Glycerol to Acrolein Over SBA-15 Supported Vanadium Substituted Phosphomolybdic Acid Catalyst.

Vapor phase dehydration of glycerol to acrolein was investigated over heteropolyacid (HPA) catalysts containing vanadium substituted phosphomolybdic acid (H4PMo11VO40) supported on mesoporous SBA-15. A series of HPA catalysts with HPA loadings varying from 10-50 wt% were prepared by impregnation method on SBA-15 support. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, Fourier Transform infrared spectroscopy, temperature-programmed desorption of NH3, pyridine adsorbed FT-IR spectroscopy, scanning electron microscopy, pore size distribution and specific surface area measurements. The nature of acidic sites was examined by pyridine adsorbed FT-IR spectroscopy. XRD results suggest that the active phase containing HPA was highly dispersed at lower loadings on the support. FT-IR and Raman spectra results confirm that the presence of primary Keggin ion structure of HPA on the support and it was not affected during the preparation of catalysts. Pore size distribution results reveal that all the samples show unimodel pore size distribution with well depicted mesoporous structure. NH3-TPD results suggest that the acidity of catalysts increased with increase of HPA loading. The findings of acidity measurements by FT-IR spectra of pyridine adsorption reveals that the catalysts consist both the Brønsted and Lewis acidic sites and the amount of Brønsted acidic sites are increasing with HPA loading. SBA-15 supported vanadium substituted phosphomolybdic acid catalysts are found to be highly active during the dehydration reaction and exhibited 100% conversion of glycerol (10 wt% of glycerol) and the acrolein selectivity was appreciably changed with HPA active phase loading. The catalytic functionalities during glycerol dehydration are well correlated with surface acidity of the catalysts.

Porous zirconium phosphate supported tungsten oxide solid acid catalysts for the vapour phase dehydration of glycerol

Solid acid catalysts containing WOx/ZrP with varying the active component loading (5–40wt%) on porous ZrP support have been investigated for the vapour phase dehydration of glycerol to acrolein. The catalyst containing 30wt% WOx/ZrP has shown high selectivity to acrolein (about 82%) with a total conversion of glycerol at 300°C in the presence of water. The calcined catalysts were characterized by X-ray diffraction, pore size distribution, FT-IR, UV-DRS, pyridine absorbed FT-IR and NH3-temperature programmed desorption to elucidate the structural and acidic properties of the catalysts. The XRD results suggest that WOx is found to be present in a highly dispersed state at lower loadings (<30wt%) and crystalline WOx at higher loadings. NH3-TPD and FT-IR results of adsorbed pyridine suggest that the total acidity and number of Brønsted acidic sites are found to increase with WO3 loading on the support. Further, there is no significant change of acidity was noticed at higher loadings. The conversion of glycerol and the selectivity toward acrolein mainly depend on the fraction of moderate acidic sites and Brønsted acidic sites. The Glycerol dehydration functionalities are explained in terms of the acidity and structural properties of WOx/ZrP catalysts. In addition, the positive effect due to addition of air to N2 feed flow suppresses the coke formation on the surface of catalyst was also investigated during dehydration reaction.

Modification of aluminum oxide as a method for controlling its activity and stability in vapor-phase dehydration of glycerol into acrolein

It is shown that promotion of γ-Al2O3 with zirconium, cobalt, boron, lanthanum, and cerium oxides strongly affects its catalytic activity and stability in vapor-phase dehydration of glycerol into acrolein. Modification of gamma-aluminum oxide with acid oxides impairs the stability and activity of the catalyst. Introduction of lanthanum and cerium oxides into the structure of γ-Al2O3 leads to a decrease in the number of strong acid centers, which diminishes the activity of the catalytic system and improves its stability.

A study of the preparation conditions of aluminum oxide on its catalytic activity and stability in vapor-phase dehydration of glycerol to acrolein

Effect of the preparation conditions of aluminum oxide on its catalytic activity and stability in the course of vapor-phase dehydration of glycerol to give acrolein was studied. The conditions were determined in which γ-Al2O3 is prepared so that the maximum selectivity of acrolein formation (∼60%) and glycerol conversion (∼80%) is in 10 h. The results of the study suggest that systems based on γ-Al2O3 are the most promising catalysts for the process under consideration.

Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

Abstract Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO 3 ) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH 3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Bronsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

Deactivation of acid catalysts in vapor-phase dehydration of glycerol into acrolein

An effect of acid properties and structure of catalysts on their deactivation and selectivity of the acrolein formation was studied in dehydration of glycerol. It was found that γ-Al2O3 is effective catalyst for vapor-phase dehydration of glycerol into acrolein.

Characterization and reactivity of 11-molybdo-1-vanadophosphoric acid catalyst supported on zirconia for dehydration of glycerol to acrolein

A series of vanadium-substituted phosphomolybdic acid (HPA) catalysts supported on zirconia were prepared by impregnation method with varying the HPA active phase content from 10 to 50 wt% on the support. The calcined catalysts were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed desorption of NH3, FT-IR spectra of pyridine adsorption and surface area measurements. XRD results suggest that the active phase of heteropolyacid is present in a highly dispersed state at lower loadings and as a crystalline phase at higher HPA loadings and these findings are well-supported by the results of FT-IR and Raman spectra. Calcination of the samples did not affect the Keggin ion structure of HPA. The ammonia TPD results suggest that acidity of the catalysts was found to increase with increase of HPA loading up to 40 wt% and decreases at higher loadings. FT-IR spectra of pyridine adsorption show that the Brønsted acidic sites increase with increase of HPA loadings up to 40 wt% catalyst. However, Lewis acid sites decrease with increase of HPA loading. Catalytic properties were evaluated during vapour phase dehydration of glycerol to acrolein. The catalyst with 40 wt% HPA has exhibited excellent selectivity towards acrolein formation with complete conversion of glycerol at 225°C under atmospheric pressure. Catalytic performances during dehydration of glycerol are well-correlated with acidity of the catalysts. Zirconia-supported H4PMo11VO40 catalysts have been investigated in the vapour dehydration of glycerol to acrolein. The catalysts are highly active and selective during dehydration of glycerol under mild reaction conditions. The high selectivity of acrolein is attributed to the presence of Brønsted acidic sites in the catalysts.

Vapor Phase Dehydration of Glycerol to Acrolein Over Phosphotungstic Acid Catalyst Supported on Niobia

The vapor phase dehydration of glycerol was carried out on niobia-supported phosphotungstic acid (PTA) catalysts. The catalysts were prepared by varying the active component PTA loadings ranging from 10 to 40 wt% on the support. The catalysts were characterized by powder X-ray diffraction, laser Raman spectroscopy, temperature programmed desorption of ammonia, ex-situ FT-IR spectra of adsorbed pyridine, BET surface area and pore size distribution. The XRD results suggest that the active phase of phosphotungstic acid was found to be highly dispersed at lower PTA loadings on the support. The findings of Raman spectra reveals that the catalyst with 30 PTA/Nb-400 clearly exhibit the primary structure of Keggin ion of hetropolyacid on the niobia support. NH3-TPD experiments confirm that the acidity of the catalyst increases with increase of PTA loading and decreases at higher loadings. The nature of acidic sites on the catalyst surface was investigated by the ex-situ pyridine adsorbed FT-IR spectroscopy and the results suggest that the catalyst with 30 PTA/Nb has shown stronger Bronsted acidic sites. Pore size distribution reveals that 30 PTA/Nb-400 exhibited lager average pore diameter than the other loadings. The Nb2O5-supported PTA catalysts have shown remarkable catalytic performance during the dehydration of glycerol to acrolein. The catalytic properties during glycerol dehydration are related to the surface acidic functionality of the catalyst.

Vapour phase dehydration of glycerol over VPO catalyst supported on zirconium phosphate

A series of VPO catalysts supported on porous zirconium phosphate with varying VPO loadings ranging from 5–30 wt% were prepared by solid–solid wetting method. The calcined catalysts are well characterized by BJH for pore size distribution, X-ray diffraction (XRD), FTIR, scanning electron microscopy (SEM), temperature programmed reduction (TPR) and UV diffuse reflectance spectroscopy. The acidic properties of the catalysts were investigated by ex-situ FTIR analysis of adsorbed pyridine and temperature programmed desorption (TPD) of NH3. The catalytic properties were evaluated for the gas phase dehydration of glycerol to acrolein. The results of pore size distribution by the BJH method suggest that the VPO loadings considerably affect the textural properties. XRD and FTIR analysis suggest that the formation of vanadyl pyrophosphate phase on the zirconium phosphate support. SEM image of unsupported VPO catalyst clearly exhibits the formation of a rosette like structure. UV-DRS study reveals the formation of vanadyl pyrophosphate phase along with some extent of vanadium orthophosphate phase. TPR analysis suggests that the reducibility of the active VPO phase depends on the VPO loading and also the active phase strongly interacts with the support. The results of vapour phase glycerol dehydration reaction are well correlated with the acidity of the catalysts measured by the ex-situ adsorbed pyridine by FTIR and TPD of ammonia. The findings derived from several characterization techniques clearly suggest that VPO species is highly dispersed on the ZrP support.

Vapour phase dehydration of glycerol to acrolein over vanadium phosphorous oxide (VPO) catalyst

X-ray diffraction patterns of pure and spent VPO samples.

Vapour phase dehydration of glycerol to acrolein over NbOPO4catalysts

BACKGROUND The valorization of glycerol obtained from biodiesel production is a challenging task. Effective use or conversion of crude glycerol to specific products will further reduce the cost of biodiesel production. RESULTS Vapour phase dehydration of glycerol to acrolein was investigated over solid acid catalysts containing nio-biumoxophosphate (NbP) by varying the calcination temperature. All the catalysts prepared were active for the synthesis of acrolein (conversion of glycerol was observed in the range 75–100% with selectivity to acrolein in the range 69–86%). The acidic properties are correlated with catalytic functionalities during dehydration of glycerol. CONCLUSIONS The NbP catalyst calcined at 550 °C has shown higher selectivity to acrolein with total conversion of glycerol. Calcination of the samples at 350 to 650 °C produces amorphous NbP sample, which contains significantly higher fractions of moderate acid sites than the crystalline NbP. The higher activity during glycerol dehydration and acrolein selectivity exhibited by NbP-550 catalyst is attributed to the presence of only moderate acidic sites with the majority of them Brønsted acidic sites. © 2013 Society of Chemical Industry

Vapor-phase Dehydration of Glycerol into Hydroxyacetone over Silver Catalyst

Abstract Silica-supported silver exhibited high catalytic activity in the dehydration of glycerol: glycerol was dehydrated into hydroxyacetone with the selectivity higher than 86% at 91% conversion over Ag/SiO2 in H2 flow at 240 °C. Silver metal provides an active site and showed stable catalytic activity for the glycerol dehydration in H2 atmosphere, while the dehydration activity decreased in N2 atmosphere. The hydrogenation of hydroxyacetone into 1,2-propanediol and the decomposition to ethylene glycol did not proceed over silver.