title: Effects of amine organic groups as lattice in ZSM-5 on the hydrolysis of dimethyl ether.
abstract: The effects of doping amine to ZSM-5 on its catalytic activity for hydrolysis of dimethyl ether (DME) have been studied theoretically using Density Functional Theory with the embedded cluster ONIOM(M06/6-31G(d,p):UFF) model. Doping by amine to ZSM-5 yields two new active centers, namely the protonated Z[NH2] and non-protonated Z[NH] amine sites in addition to the normal Brønsted acid Z[OH] site. The reaction has two possible stepwise and concerted channels. The stepwise channel consists of two elementary steps; (i) the demethylation followed by (ii) the hydrolysis while the concerted channel involves in the demethylation and hydrolysis in a single step. We found that the reaction favors to proceed via the concerted channel at all three active centers. The results predict that the Z[OH] shows the best catalytic performance for the studied reaction. The Z[NH2] is not catalytically active due to the activation barriers are extremely high for both stepwise and concerted pathways. The demethylation step is energetically favorable over the Z[NH] site, however, the product methylamonium surface intermediate is too stable to be further converted to methanol.
authors.affiliation: National Nanotechnology Center, National Science and Technology Development Agency, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Jittima
authors.initials: J
authors.lastname: Meeprasert
authors.forename: Siriporn
authors.initials: S
authors.lastname: Jungsuttiwong
authors.forename: Thanh N
authors.initials: TN
authors.lastname: Truong
authors.forename: Supawadee
authors.initials: S
authors.lastname: Namuangruk
mesh_terms: D000588:Amines / Q000737:chemistry; D002384:Catalysis; D006868:Hydrolysis; D008738:Methyl Ethers / Q000737:chemistry* / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D013816:Thermodynamics; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000588:Amines; D008738:Methyl Ethers; C570564:ZSM-5 zeolite; D017641:Zeolites; C033413:dimethyl ether