Alkylation of Alkylaromatics cracking of Naphtha and CO2 Sorption over ZSM 5 Zeolite

Abstract

Zeolites are extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis involving production of fine and specialty chemicals. They have been synthesised hydrothermally from highly viscous mixtures of colloidal silica, sodium aluminate, sodium hydroxide, water and a structure directing template. The present study attempted to suppress fluoride ion complexation of aluminium using a co-complexant, phosphate. The SEM analysis illustrated large crystal size with smooth surface. TPD (ammonia) showed presence of weak and medium acid sites. Time on stream study was carried out for 5 h to compare the activity of the catalysts. The conversion decreased slowly illustrating resistance to coke formation. Medium pore size and absence of strong acid sites were suggested to be the cause for the slow coke formation. The study of time on stream showed steady ethylbenzene conversion and high selectivity to 1,4-DEB. Cracking of naphtha to light olefins over HZSM-5(Si/Al = 25, 50 and 75) at 675 °C in helium atmosphere was studied. The commercial catalyst was also tested for the same reaction for comparison. The results indicated nearly same yield of light olefins over all the catalysts. Though the commercial catalyst carried high density of acid sites compared to the present system of catalysts, similar level of conversion was due to its high hydrogen transfer activity. This study concluded that synthesis of HZSM-5 in fluoride medium with phosphate as co-complexant could be more advantageous than those synthesised in alkaline medium for selective alkylation of alkylaromatics and cracking of naphtha to high yield of olefins. Dipole-dipole interaction between CeO2 and CO2 was suggested as the cause for CO2 adsorption. Hence, it was established that rice husk ash could be a better source of silica for the synthesis of NaZSM-5 in alkaline medium, and NaZSM-5 could be a convenient support for fine dispersion of transition and rare earth metal oxide for CO2 adsorption. newline