Vapour phase dehydration of glycerol to acrolein over NbOPO₄catalysts

Abstract

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

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over ZnxZryOz

“…Figure a shows that the dominant phase of the pure zirconia is monoclinic, as evidenced by the peaks at 2θ angles of 24, 28, 32, and 56°, − denoted by stars. As the Zn loading increases, prominent peaks at 2θ angles of 30, 35, 50, and 59° appear, denoted by triangles, that are characteristic of tetragonal zirconia. − The pure bulk ZnO exhibits peaks at 2θ angles of 32, 34, 37, 47, 57, 64, 67, 68, and 69°, denoted by the squares, that are characteristic of wurtzite (WZ). , The wurtzite phase is not observed for Zn x Zr y O z , suggesting that clusters of bulk ZnO are not present on the surface of these catalysts. As the weight loading of Zn approaches a theoretical monolayer coverage of zinc oxide over the zirconia (occurring at molar ratio of Zn/Zr ∼1:50 for particles 5 μm in diameter), the crystal structure of the zirconia changes from monoclinic to tetragonal.…”

“…The XRD patterns and Raman spectra are shown in Figure a, b. Figure a shows that the dominant phase of the pure zirconia is monoclinic, as evidenced by the peaks at 2θ angles of 24, 28, 32, and 56°, − denoted by stars. As the Zn loading increases, prominent peaks at 2θ angles of 30, 35, 50, and 59° appear, denoted by triangles, that are characteristic of tetragonal zirconia. − The pure bulk ZnO exhibits peaks at 2θ angles of 32, 34, 37, 47, 57, 64, 67, 68, and 69°, denoted by the squares, that are characteristic of wurtzite (WZ). , The wurtzite phase is not observed for Zn x Zr y O z , suggesting that clusters of bulk ZnO are not present on the surface of these catalysts.…”

An Environmentally Friendly Nb–P–Si Solid Catalyst for Acid-Demanding Reactions

“…In particular, biorefinery reactions take place in environments where high amounts of water vapor are present, or directly in liquid water (sugar polymer and carbohydrate transformations). Niobium oxophosphate (NbOPO 4 , NbP) is an interesting solid acid catalyst (Ho < −8.2) with a high ratio of Brønsted (BAS) to Lewis (LAS) acidic sites, − which has been used as a water-tolerant solid acid catalyst for various reactions of interest in biorefining, such as esterification, hydrolysis, dehydration, ,− and alkylation . The advantages of NbP stem from the recognized stability of Nb–O–P bonds toward hydrolysis and the presence of both kinds of acid sites at the surface.…”

Synthesis and Characterization of Zirconia Supported Silicotungstic Acid for Ethyl Levulinate Production

“…23 Nevertheless, the presence of peaks at 30.0°, 35.3°, and other 2θ values indicates the presence of tetragonal and cubic phases in a minor amount. 24,25 On the contrary, Keggin type silicotungstic acid diffraction peaks were not significantly visible in synthesized catalysts, thereby confirming uniform and homogeneous distribution over ZrO 2 support. However, one or two peaks at different 2θ values than that of zirconia were visible in the ESZN-4 catalyst, thus indicating a possible weak interaction between the parent Keggin HPS and the ZrO 2 support.…”