The SAPO-11 molecular sieve was impregnated with CuNO3, and the surface area and pore volume of the modified SAPO-11 molecular sieve decreased, while the total acid content decreased. With the increase of Cu loading on SAPO-11 zeolite, the selectivity of 2, 6-DMN increased and the conversion rate of naphthalene decreased. Although the conversion rate of naphthalene was low, it could be remixed and the selectivity could be improved, but the higher the activity of catalyst, the easier the deactivation and the catalyst life was shorter.
HZSM-5 zeolite molecular sieve has a three-dimensional crossed pore system, and its pore is composed of ten-membered rings, and has good shape selection. Compared with the other two molecular sieves, HZSM-5 is less acidic, which is the most favorable for the synthesis of 2,6-DMN. However, due to its unique three-dimensional pore structure, the reactant and product molecules are diffused more rapidly in the pore, thus ensuring the better stability of HZSM-5 molecular sieve catalyst in the reaction, but the selectivity is relatively low. Although the structure and acidity of ZSM-5 molecular sieve are adjusted by post-treatment and other methods, The selectivity of 2,6-DMN and catalyst life were improved, but the activity was decreased.
MCM-22 molecular sieve has high conversion rate, good stability and low selectivity, SAPO-11 selectivity and high ratio of 2,62,7-DMN, with the progress of the reaction, the conversion rate decreased rapidly, HZSM-5 stability, selectivity and conversion rate are relatively low. The stability, conversion rate and selectivity of HZSM-5, SAPO-11 and MCM-22 molecular sieve catalysts decreased while the other index increased. It is difficult for molecular sieve to have good reactivity and high selectivity for 2,6-DMN at the same time. How to prepare catalysts with high activity, good stability and high selectivity is the challenge we face. To achieve a relative balance among various performance indexes of the catalyst is the proposition that naphthalene and methyl naphthalene alkylation cannot escape.
