Study For Alkylation Of Toluene With Methanol On Multi-stage-reactor

Para-xylene is widely used in our daily life as a basic organic chemical material, it’s downstream products terephthalic acid and dimethyl terephthalate manufacture is the main materials to produce polyester fibers and resins. At present, para-xylene is mainly come from naphtha, In addition, relying on aromatic combination plant, toluene disproportionation or selective disproportionation of toluene, isomerization of mixed xylenes and transalkylation can also improve the yield of para-xylene. However, thermodynamic equilibrium concentration mixed xylene are produced in processes above, energy consumption in separation is high. Alkylation of toluene with methanol can produce para-xylene with high selectivety by one step, it can reduce the energy consumption in separation significantly and save equipment investment cost; Improve the utilization of toluene and there is almost no benzene in production; To expand the sources of raw metarial by using the excess and cheap methanol, make it true to combination coal chemical industry and petrochemical industry.Higher mole ratio of toluene/methanol can reduce the occurrence of side reactions and the toluene convertion rate is more closed to the ideal value, but there will be a large amount of toluene circulated in the device in separation process, which increases the energy consumption a lot. So it’s necessary to make a development of multi-stage-reactor, toluene can be converted by feeding methanol between stages, it can improve the utilization of toluene, reduce the circulation amount of toluene in the device, it can also reduce the energy consumption in separation process and save equipment investment cost, it may improve the economy in industrialization.In this article several different nano HZSM-5 was modified with Si-P-Mg-Si-Pt firstly, and evaluated the catalytic reactivity under the specific reaction conditions, compared with the activity, selectivy and stability of these catalyst, selected 5#-Pt/HZSM-5 which has the optimal reaction performance(the conversion of toluene (CT) was 9.7% and para-selectivity (SPX) stablized at over 90% in 250h), used it in the subsequent amplification. Investigated the performance under the condition of material circulation on the scale-up single-stage fixed bed reactor, find that the conversion of toluene and para-selectivity was decreased under material circulation. And then analysis the compact of C8 to the reaction, find that para-xylene is a key factor impaffecting the subsequent reaction. Finally, Investigated the performance of 5#-Pt/HZSM-5 on the scale-up multi-stage-reactor:Fresh catalyst react last for 430h, the conversion of toluene was 19.8% and para-selectivity was 87%, after in situ regeneration, regenerated catalyst restore the performance of fresh catalyst and react another 470h. Both fresh and regenerated catalyst maintained a good effect in hydrogenation. With the increase of the stage number, the coke amount increases and the polycyclic aromatic hydrocarbon coke species increases.