No description available.

No description available.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 141-144). Also available via the Internet.

In this study, an attempt was made to synthesis SAPO-34 using piperidine as structure directing agent/ template. The synthesis parameters such as crystallization temperature, crystallization time, phosphorus content and silicon content, as well as Na, Fe, Co and Ni impregnation were varied. The resulting materials were characterized by a combination of physicochemical techniques such as XRD, SEM spectroscopy, NH3-TPD and SS NMR spectroscopy. The peaks at 2θ = 9.9⁰, 13.0⁰, 15.0⁰, 18.0⁰, 21⁰, 26⁰, 32⁰ on XRD patterns confirmed the presence of SAPO-34 phase, extra peaks at 2θ = 7.9 ⁰, 20 ⁰, 23 ⁰and 26 of XRD patterns indicated the existence of SAPO-5. Most of the samples of the molecular sieves comprised SAPO- 5 and SAPO-34. The SAPO-5 materials were the main domain and SAPO-34 materials were less. The two peaks that appeared in the temperature regions between the ranges 190-250 ⁰C and 340-380 ⁰C that were assigned for weak and medium BrØnsted acid site on NH3-TPD profiles. The SS NMR spectroscopy and XRD patterns confirmed a SAPO-34 phase with amorphous phase in a sample prepared with SiO2/Al2O3 = 2.4 molar ratio at 200 ⁰C for 5 days. The NH3-TPD profile and SS NMR spectroscopy for this molecular sieve confirmed the presence of weak and strong acid sites assigned to P-OH-Al and Si-OH-Al hydroxyl groups. All the molecular sieves were used in MTO reaction. The selectivity to ethylene and propylene on the molecular sieves prepared at 190 ⁰C for 5 days is better than the selectivity to ethylene and propylene on the molecular sieve synthesized at 170 ⁰C, 200 ⁰C and 210 ⁰C for 5 days. Molecular sieve prepared at 200 ⁰C for 4 days was better in ethylene and propylene selectivity than the molecular sieve prepared at 200 ⁰C for 2-3 days, 5-6 days. Methane and DME were the main products on most of the molecular sieves. Methane, ethylene and propylene and some impurities were the products on molecular sieve prepared with SiO2/Al2O3 = 2.4 molar ratio in MTO reaction. The conversions of DME towards light olefins were extremely low. Na- SAPO reduced methane, and improved ethylene and propylene selectivity. Nonmodified and Co-SAPO molecular sieves improved the selectivity towards light olefins. Piperidine can be used as a template to synthesis SAPO-34 molecular sieve within a short period of five days. SAPO-5 was synthesized instead of SAPO, and DME was the main product instead of light olefins on the molecular sieves during MTO reactions.

No description available.

No description available.

Graduation date: 1995

Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Raul F. Lobo, Dept. of Chemical Engineering. Includes bibliographical references.

No description available.

No description available.