The process of methanol conversion to dimethyl ether over an H-SAPO-34 molecular sieve was studied, using the catalyst as synthesized or formulated in an alumina matrix. The experiments were performed on the temperature interval 100−250 °C, liquid space velocities of 1−5 h−1, and pressures between 1 and 10 bar. The results evidenced a high catalytic activity of the H-SAPO-34 molecular sieve, providing in these conditions a practically total methanol transformation to dimethyl ether. Also, a special run, performed at 180 °C, with an output composition close to chemical equilibrium, showed no significant change of catalyst activity during an on-stream time of 50 h, this proving a good stability and resistance to deactivation. A published rate expression for the methanol dehydration reaction was selected and adapted to describe the experimentally observed process kinetics.
Characterization of products.Figure S1. SAXS powder pattern of (a ) P123-alumina ( procedure III) calcined at 500 o C (d = 6.24 nm); (b) as synthesized LA-alumina. ( procedure II) (d = 3.5nm)
The published kinetic models for methanol etherification over ZSM-5 zeolite were evaluated against our own experimental data. The process was investigated over a synthesized H-ZSM-5 zeolite using a laboratory fixed-bed reactor. The experiments were carried out at atmospheric pressure, temperatures of 170−270 °C, methanol feed concentrations up to 15 mol %, and gas phase velocity (WHSV) values in the range of 15−48 h −1 . The results showed a decrease of methanol conversion with respect to feed methanol concentration, with the single reaction product obtained in significant concentrations being dimethyl ether (no secondary products were observed in significant concentrations). The methanol conversion measurements were compared with theoretical predictions based on the main kinetic models published for methanol etherification over ZSM-5 zeolites with different acidities. As none of the published models fitted satisfactorily with our experimental data, we re-estimated the parameters of the tested models and applied a discrimination procedure in order to identify the most suitable one. The best quality of the fit was obtained by using an LH kinetic model based on the associative surface reaction mechanism. The adequacy of this kinetic model was confirmed by statistical and thermodynamic consistency criteria.
In this study, non-irradiated and weathered multiwalled carbon nanotubes (MWCNTs) obtained through irradiation, were studied as adsorbents for BPA, both nanomaterials being characterized before and after the adsorption process. The objectives of our investigation were to compare the characteristics of non-irradiated and irradiated MWCNTs, to evaluate the adsorption capacity of BPA by pristine and irradiated MWCNTs and to determine the variation of the kinetic, sorption and thermodynamic parameters during sorption process using both sorbents.
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