Table 1represents the physicochemical properties of H-USY, 10-30P-Y and 10-30S-Ysamples. In all H3PO4treated samples i.e. 10-30P-Y, the P (wt%) was observed to be increased from 0.075%to 1.8%, whereas Al (wt%) decreases from 2.
84 (parent H-USY) to 0.93% (30P-Y).Amongst P-Y samples, the reduction of Al is 58 (10P-Y) to 67% (30P-Y) comparedto parent H-USY. H2SO4 treated samples viz; 10, 20 &30S-Y also showed a decrease of Al from 0.94 to 0.86 (wt%) which corresponds to67 to 70% as compared to parent H-USY (2.
84%) at identical sulphur content of 0.12 (wt%). This decrease of Al may be dueto Al separation from extra framework and from framework. Inoverall, H3PO4 treatment showed less dealumination (58-65%) than H2SO4 ( 67- 70%) due to formation of newAl-O-P bond in framework as well as AlPO species generation with extraframework Al. Table 1: Physico-Chemical Properties of H-USY & different concentration of H3PO4and H2SO4 treated H-USY Catalysts Catalyst P(wt %) # S(wt %) # Al # (wt%) Total acidity * (mmol/g) H-USY – – 2.84 0.
86 10 P-Y 0.075 – 1.18 0.27 20 P-Y 0.
085 – 1.14 0.58 30 P-Y 1.
8 – 0.93 0.98 10 S-Y – 0.12 0.94 0.31 20 S-Y – 0.12 1.
16 0.18 30 S-Y – 0.11 0.86 0.22 # Wt % ofPhosphorous (P), Sulphur (S) & Aluminium (Al) Estimated by EDAX, * Total acidity Estimated by NH3-TPD Fig.
2A shows NH3-TPD profiles of H-USY, 10P-Y,20P-Y & 30P-Y andFig. 2B depict NH3-TPD profiles of H-USY, 10S-Y, 20S-Y& 30S-Y. NH3-TPDprofiles of parent H-USY shows two desorption peaks in temperature range of 100-250oCand 250-450oC respectively, which corresponds to desorption ofammonia adsorbed on sites of weak acidity (100-250oC) and relativelystrong acidity (250-450oC).27 In NH3-TPD profiles of all 10-30P-Y (Fig.
2A), adesorption peaks of strong acid sites decreases from 10 to 30P-Y samples as compared to parent H-USY. In case of 10P-Y peak of weak acid site significantlydecreased however it was further increased in 20P-Y and 30P-Y samplerespectively (Fig. 2A). The decrease of weak and strong acidity with 10P-Y may be due todealumination of framework & extraframework alumina and an increase of weakacidity in 20P-Y & 30P-Y may be attributed to an increase of Al-O-P linkages &comparatively lower dealumination (Table-1) than 10P-Y as compared to parent H-USY.28 The NH3-TPD profiles of all 10-30S-USYexhibited significantly decreased of both (weak as well as strong) desorptionpeaks which is attributed to the more dealumination than P-Y samples and thereis no additional species formation like 10-30P-Y.