IndianJournalofChemistry Vol.3? A, July 1998, pp. 655 - 658 Alcohols via direct hydration of ethylene over alwninophosphate based molecular sieves in the vapour phase C Kannan, S P Elangovan', M PalanichamyzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA & V Murugesan' DepartmentofChemistry,AnnaUniversity,Madras 600 025, India Received:3 October 1997; revised 5 May 1998 Ethylene hydration gives isobutanol, ethanol andwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA n- butanol over NAPO-l1 and ZAPO-ll molecular sieves in the vapour phase. The effects of partial pressure of water vapour, temperature and time on stream have been studied and the conditions optimised to achieve better conversion and selectivity. The product selectivity is correlated with the nature of acid sites of the catalysts. Synthesis of alcohols from ethylene is an industrially important reaction and this has been the subject of numerous investigations. Impregnated mineral acid catalysts 1 such as sulphuric acid and phosphoric acid are reported in the literature for the synthesis of alcohols. But the use of these catalysts leads to low conversion, environmental concern and corrosion problems. The NiS0 4 .xH 2 0 catalyst was reported to be active for ethylene hydration" OgasawarazyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA et al 3 attempted ethylene hydration over niobic acid Nb 2 0 s . nH 2 0, Nb 2 0 s -F and Nb 2 0 s - S04 2 - , and all these showed better activity than mineraI acid and NiS0 4 .xH 2 0 when evacuated at relatively low temperature. Among these, the simple solid acid, Nb2 0 s . nH 2 0 which does not contain F - and sol ions will be the best since the catalysts containing F - and SO.• 2- may release these ions causing corrosion when used for long periods. With a view to finding out eco-friendly solid acid catalysts, we have made attempts to carry out ethylene hydration over ZAPO-II and NAPO-II t Department of Chemistry, Sri Venkateswara College of Engineering, Sri Perumbudur 603 105, India molecular sieves. These catalysts have the acid sites internally within their tetrahedral frame work and hence they do not cause corrosion and environmental problems. Experimental Synthesis and characterisation NAPO-II and ZAPO-ll molecular sieves were synthesised by hydrothermal crystallisation using aluminium isopropoxide and orthophosphoric acid as sources for aluminium and phosphorus respectively and dipropylamine as template by adopting the method described in our earlier papers" - 6. The gel composition and pH for the synthesis were as follows: NAPO -. 11 Gel composition (M) 0.1 NiO: OPA: Ah03: P 2 0 S : 40 H 2 0 pH 4.0 (before); 9.1 (after) ZAPO -11 Gel composition (M) 0.1 ZnO: OPA: Ah03: P 2 0 S : 40 H 2 0 pH 3.9 (before); 9.7 (after) The catalysts were characterised by instrumental methods and the characterisation data were found to agree well with our earlier reported data" 6. X-ray diffraction analysis was carried out employing a Siemens 0500 diffractometer in the scan range of 29 between 5 and 50° using cox, source. The peaks were identified with reference to compilation of simulated XRD powder patterns. IR spectra of the samples were recorded on a Bruker IFS 66v FT- IR spectrophotometer using KBr pellets. TG analyses were carried out with a Mettler TA 3000 system at a scanning rate of 20°C min" in a stream of dry air. Inductively coupled plasma (lCP) ARL 3410 with minitorch was used to determine the chemical composition of the samples. BET surface area was measured on a Micromeritics Pulse Chemisorb 2700 using nitrogen as adsorbate at - 170° C. ESR spectra were recorded on a Varian E112 spectrometer at room temperature. Acidity of the samples was measured by temperature progranuned desorption (TPD) of pyridine using TGA (Mettler TA3000). From the weight loss of