Isopropylation over HY, HL and Other Zeolites

2 Isopropylation over HY, HL and Other Zeolites - The catalysis over HY and HL zeolites is quite different from that over HM. The product distribution over HY and HL resembled that of SA the formation of 4,4 -DIPB was non-regioselective (Table l).18-1 These catalyses are not controlled by the environments of the pores because both zeolites have sufficiently large pores for the transition states form all the IPBP and DIPB isomers. Instead, the product distribution markedly changes by the reaction temperature. At low temperatures, the products are determined by the reactivity at 2- and 4-positions of biphenyl for electrophilic alkylation to yield principally 2- and 4-IPBP for IPBP isomers and 

DIPB isomers with 2-isopropyl groups. This is due to the higher electron density of the 2- and 4-positions compared to the 3-position. However, the amounts of 3-and 4-IPBP, 3,4 - and 3,3 -DIPB increased with increasing temperature. These isomers may be formed by the isomerization of IPBP and DIPB isomers with 2-isopropyl groups because the former isomers are thermodynamically more stable isomers than the latter. These results show that the isopropylation of biphenyl over HY, HL, and SA is controlled by the reactivity of the reactant molecules at low temperatures, and by the thermodynamic stability of the product molecules at higher temperatures. 

Matsuda and his co-workers examined the isopropylation of biphenyl over H-offretite and SAPO-ll.52 H-Offretite has pore size of 0.67x0.68 nm, but its pores have cages in the channels.30 SAPO-ll has pores of 0.63x0.39 nm.30 H-Offretite was less selective for the formation of 4,4 -DIPB than HM although their catalytic activities were comparable. SAPO-ll exhibited a comparable selectivity for 4,4 -DIPB to HM although catalytic activity was low. The formation of 4,4 -DIPB over these two zeolites was shape-selective compared to the thermodynamically attainable level. 

Loktev and Chekriy showed that HZSM-12 produced 4,4 -DIPB with much higher selectivity than HM, H-beta (HP), HY, and HZSM-5 using flow type reactor at 200-270 °C.53 HM yielded predominantly 3,4 -DIPB among DIPB isomers under the conditions. HY and HZSM-5 extensively catalysed propylene oligomerization. 

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Isopropylation over HY, HL and Other Zeolites - The catalysis over HY and HL was quite different from that over HM.61 63 The further isopropylation of IPN and DIPN isomers was quite rapid in spite of the higher number of bulky isopropyl groups. The yield of IPN had a maximum value during the initial stage of the reaction, and then decreased with reaction time. At longer periods, the product amounts decreased as follows DIPN > IPN > TrIPN. Because the catalytic activities correlate well with the pore surface areas of the zeolite, the isopropylation occurs predominantly inside the pores. These results indicate that HY and HL have enough space for the isopropylation of naphthalene inside their pores. Naphthalene and its alkylates can easily enter into and diffuse out of the pores. 

Isopropylation over HY, HL and Other Zeolites - The catalysis over HY and HL was quite different from that over The further isopropylation... 

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