Shape-Selective Alkylation Of Toluene With Methanol Or Ethanol Over Modified Nano-scale HZSM-5 Zeolite

Para-Ethyltoluene (P-ET) are used for the production of poly-methylstyrene (PMS). Compared with polystyrene (PS), PMS has many physical advantages such as lower specific gravity, higher flash point and higher glass transition temperatures. Para-Xylene(PX) can be used for the production of terephthalic acid (PTA) and dimethylterephthalate (DMT). PTA and DMT can in further react with diols to produce polyester, which are widely used in chemical fiber, synthetic resin, plastics, and other fields. Toluene (T) shape-selective alkylation with ethanol (E) and methanol (M) to produce para-ethyltoluene and para-xylene is a new technologic route. This thesis focused on the choosing of the type of zeolites and analyzing how did the modification of Si, P, Mg influence the alkylation of T with E/M.The catalytic performance for T shape-selective alkylation with E over modified nanoscale HZSM-5 and nanoscale HZSM-11 were studied in this work. The results indicated that nanoscale HZSM-5 modified with rare earth showed good catalytic performance. Atmospheric pressure was more conducive to maintaining the stability of the catalyst. For nanoscale HZSM-5 catalysts which impregnated with 6 wt%SiO2,3 wt% MgO, the para-ethyltoluene selectivity reached 100%. For nanoscale HZSM-5 catalysts modified with rare earths, under 334 hrs on-stream, the toluene conversion can be maintained 15% and the the selectivity to para-xylene was higher than 96%, during T alkylation with E at lO1KPa,3 h"1, 400℃, T/E=6mol/mol, N2/(T+E)=2 mol/mol and H2O/(T+E)=1 mol/mol.The catalytic performance for T alkylation with M over microscale HZSM-5 and nanoscale HZSM-5 were studied. Compared with microscale, nanoscale HZSM-5 showed higher activity and para-selectivity. So that nanoscale HZSM-5 was chosed to be the parent zeolite for T alkylation with M. The physicochemical property and catalytic performance for T shape-selective alkylation with M were studied over nanoscale HZSM-5 modified with SiO2, P2O5 and MgO. For the modified nanoscale HZSM-5, it can be concluded that the decline in the activity of the catalyst and the improvement of selectivity resulted from the decrease of total acidity, strong acidity, total Lewis/Bronsted acidity, BET surface area, pore volume and average pore size. The effects of temperature, space velocity (WHSV), and flow rate of nitrogen carrier gas and water on the reaction were investigated in a continuous flow fixed-bed reactor. It was found that increasing the line speed by increasing flow rate of nitrogen can not raise the para-xylene selectivity all the time. Under the optimized conditions (2 h-1,460℃, T/M=8, H2O/hydrocarbon=8, N2/hydrocarbon=8 molar ratio), during 500 h on stream over 6wt%SiO2,5%P2O5 and 3wt% MgO modified nano-scale HZSM-5 catalysts, the toluene conversion of about 10% and the selectivity to para-xylene (PX) of more than 97% were maintained, indicating that the catalyst exhibits high selectivity and good stability, and have potential in application in industry.