Active site for hydrogenation on reduced V2O5/Al2O3 catalyst

1991 ◽  
Vol 43 (2) ◽  
pp. 481-486 ◽  
Author(s):  
S. Ishida ◽  
S. Imamura ◽  
A. Iwaki ◽  
Y. Fujimura
Keyword(s):  
Active Site ◽  
Al2o3 Catalyst

scholarly journals Kinetic Study of the Selective Hydrogenation of Acetylene over Supported Palladium under Tail-End Conditions

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 180 ◽  
Author(s):  
Caroline Urmès ◽  
Jean-Marc Schweitzer ◽  
Amandine Cabiac ◽  
Yves Schuurman
Keyword(s):  
Selective Hydrogenation ◽  
Active Site ◽  
Reaction Conditions ◽  
Selective Hydrogenation Of Acetylene ◽  
End Conditions ◽  
Supported Palladium ◽  
Α Al2o3 ◽  
Intrinsic Kinetic ◽  
Kinetics Of ◽  
Al2o3 Catalyst

The kinetics of the selective hydrogenation of acetylene in the presence of an excess of ethylene has been studied over a 0.05 wt. % Pd/α-Al2O3 catalyst. The experimental reaction conditions were chosen to operate under intrinsic kinetic conditions, free from heat and mass transfer limitations. The data could be described adequately by a Langmuir–Hinshelwood rate-equation based on a series of sequential hydrogen additions according to the Horiuti–Polanyi mechanism. The mechanism involves a single active site on which both the conversion of acetylene and ethylene take place.

Role of Citric Acid in Preparing Highly Active CoMo/Al2O3 Catalyst: From Aqueous Impregnation Solution to Active Site Formation

2017 ◽  
Vol 56 (48) ◽  
pp. 14172-14181 ◽  
Author(s):  
Jianjun Chen ◽  
Jinxing Mi ◽  
Kezhi Li ◽  
Xiqin Wang ◽  
Elizabeth Dominguez Garcia ◽  
...  
Keyword(s):  
Citric Acid ◽  
Active Site ◽  
Site Formation ◽  
Highly Active ◽  
Al2o3 Catalyst ◽  
Impregnation Solution

CO2 Hydrogenation to Methanol Over Cu/ZnO/Al2O3 Catalyst: Kinetic Modeling Based on Either Single- or Dual-Active Site Mechanism

2022 ◽  
Author(s):  
Hou-Xing Li ◽  
Liu-Qing-Qing Yang ◽  
Zi-Yi Chi ◽  
Yu-Ling Zhang ◽  
Xue-Gang Li ◽  
...  
Keyword(s):  
Kinetic Modeling ◽  
Active Site ◽  
Co2 Hydrogenation ◽  
Al2o3 Catalyst

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Structures of c-di-GMP/cGAMP degrading phosphodiesterase VcEAL: identification of a novel conformational switch and its implication

2019 ◽  
Vol 476 (21) ◽  
pp. 3333-3353 ◽  
Author(s):  
Malti Yadav ◽  
Kamalendu Pal ◽  
Udayaditya Sen
Keyword(s):  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Triosephosphate Isomerase ◽  
Catalytic Mechanism ◽  
Degradation Mechanism ◽  
Structural Basis ◽  
Conserved Residues ◽  
Phosphodiester Bond ◽  
Cyclic Dinucleotides

Cyclic dinucleotides (CDNs) have emerged as the central molecules that aid bacteria to adapt and thrive in changing environmental conditions. Therefore, tight regulation of intracellular CDN concentration by counteracting the action of dinucleotide cyclases and phosphodiesterases (PDEs) is critical. Here, we demonstrate that a putative stand-alone EAL domain PDE from Vibrio cholerae (VcEAL) is capable to degrade both the second messenger c-di-GMP and hybrid 3′3′-cyclic GMP–AMP (cGAMP). To unveil their degradation mechanism, we have determined high-resolution crystal structures of VcEAL with Ca2+, c-di-GMP-Ca2+, 5′-pGpG-Ca2+ and cGAMP-Ca2+, the latter provides the first structural basis of cGAMP hydrolysis. Structural studies reveal a typical triosephosphate isomerase barrel-fold with substrate c-di-GMP/cGAMP bound in an extended conformation. Highly conserved residues specifically bind the guanine base of c-di-GMP/cGAMP in the G2 site while the semi-conserved nature of residues at the G1 site could act as a specificity determinant. Two metal ions, co-ordinated with six stubbornly conserved residues and two non-bridging scissile phosphate oxygens of c-di-GMP/cGAMP, activate a water molecule for an in-line attack on the phosphodiester bond, supporting two-metal ion-based catalytic mechanism. PDE activity and biofilm assays of several prudently designed mutants collectively demonstrate that VcEAL active site is charge and size optimized. Intriguingly, in VcEAL-5′-pGpG-Ca2+ structure, β5–α5 loop adopts a novel conformation that along with conserved E131 creates a new metal-binding site. This novel conformation along with several subtle changes in the active site designate VcEAL-5′-pGpG-Ca2+ structure quite different from other 5′-pGpG bound structures reported earlier.

Contributions of the substrate-binding arginine residues to maleate-induced closure of the active site of Escherichia coli aspartate aminotransferase

2001 ◽  
Vol 268 (6) ◽  
pp. 1640-1645
Author(s):  
Annelise Matharu ◽  
Hideyuki Hayashi ◽  
Hiroyuki Kagamiyama ◽  
Bruno Maras ◽  
Robert A. John
Keyword(s):  
Escherichia Coli ◽  
Active Site ◽  
Aspartate Aminotransferase ◽  
Substrate Binding ◽  
Arginine Residues
Sign in / Sign up

Export Citation Format

Share Document