Direct oxidation of benzene to phenol

2014-07-07T11:14:15Z (GMT) by Mohammad H. Sayyar
This thesis deals with two major process routes for the direct oxidation of benzene to phenol. The main objective of the first route was to understand the properties of the porous stainless steel (PSS) needed for support of a catalyst deposited onto its surface, to identify the morphologies of the Pd membrane deposited onto the PSS, to design a catalytic membrane reactor, to characterise membrane in terms of its permeability to hydrogen, and then to investigate hydroxylation of benzene using oxygen as an oxidant. It was observed, using Mo or zeolites as a second catalyst and the reactor design affect the productivity and selectivity towards phenol. This research has also shown the effects of the catalytic properties of iron zeolites with a focus on reactions involving the decomposition of nitrous oxide and direct oxidation of benzene to phenol using nitrous oxide as the oxidant. The main objective of this second route was to identify the active sites in the catalysts, and to a design catalyst based on the acquired knowledge. The methodology was to incorporate iron either at framework positions via hydrothermal synthesis of the zeolites followed by controlled migration to extra-framework positions, or directly at extra-framework positions via sublimation of FeCh or liquid ion-exchange. In this project, different catalysts were characterized and their catalytic activities compared. It was observed contaminants such as N-containing compounds, O2, CO, and water affected the catalytic properties and catalyst half-life. In this thesis, two different methods were used to improve productivity when using a PdlPSS membrane. First, changing design of the reactor, and second, using Mo as a second catalyst. It was observed that higher productivity was obtained when the reactor tube was packed with Fe/ZSM-5 and N20 using as the oxidant. From an economic point of view, using N20 in the presence of zeolite in a fixed-bed reactor is expected to offer more advantages than Pd membrane for oxidation of aromatic compounds.