ADSORPTION EQUILIBRIUM OF CH4 AND CO2 ON SILICOALUMINA-PHOSPHATE MOLECULAR SIEVE (SAPO-34) HAS BEEN STUDIED IN VARIOUS OPERATING CONDITIONS, EXPERIMENTALLY AND THEORETICALLY. THE EXPERIMENTS WERE PERFORMED IN THE BATCH SYSTEM ON THE BASE OF VOLUMETRIC MEASUREMENT TECHNIQUE FOR THE ABSOLUTE GAS PRESSURE RANGE OF 1 TO 10 BAR AND THREE DIFFERENT TEMPERATURES OF 303, 313 AND 323 K. THE MAXIMUM ADSORPTION CAPACITIES OF CH4 AND CO2 WERE DETERMINED AS 1.254 AND 5.125 MMOL/GR, RESPECTIVELY, AT THE EQUILIBRIUM PRESSURE OF 9.0 BAR AND TEMPERATURE OF 303 K. THE EXPERIMENTAL ISOTHERMS WERE MODELED ON THE BASE OF DIFFERENT ISOTHERM EQUATIONS; LANGMUIR, SIPS, TOTH AND UNILAN BY MINIMIZING THE MEAN RELATIVE DIFFERENCE BETWEEN THE MODEL AND EXPERIMENTAL ADSORPTION CAPACITY. AMONG THE SO-CALLED MODELS, LANGMUIR HAS SHOWN THE BEST AGREEMENT WITH THE EXPERIMENTAL RESULTS, AND IT REVEALS THAT THE ADSORPTION MECHANISM WOULD BE MONOLAYER ADSORPTION WITH THE HOMOGENEOUS ADSORPTION SYSTEM OF CH4-SAPO34 AND CO2-SAPO34.

SEVERAL SAMPLES WERE SYNTHESIZED UNDER HYDROTHERMAL CONDITIONS BY USING TEAOH, DEA (DIETHYLAMINE), TEA (TRIETHYLAMINE) AND MORPHOLINE AS STRUCTURE-DIRECTING AGENTS. THE SIGNIFICANCE OF TEMPLATE ON CRYSTAL PHASE, MORPHOLOGY, CRYSTAL SIZE AND CRYSTALLINITY WERE STUDIED. SAPO-5 AND SAPO-34 MOLECULAR SIEVES WITH DIFFERENT CRYSTAL SIZE IN THE RANGE OF 300 NM-10 MM WERE FORMED, USING DIFFERENT TEMPLATE. THE SAPO CRYSTALS WERE CHARACTERIZED BY X-RAY DIFFRACTION (XRD), SCANNING ELECTRON MICROSCOPY (SEM), AND ENERGY-DISPERSIVE X-RAY SPECTROSCOPY (EDX). THE RESULTS SHOW THAT TEAOH IS THE MOST PROPER TEMPLATE FOR SAPO-34 SYNTHESIS WHEREAS TEA IS AN APPROPRIATE TEMPLATE OF SAPO-5. DEA AND MORPHOLINE HOWEVER CAN PRODUCE SAPO-34 OR SAPO-5 DEPENDING ON THEIR CONCENTRATION USED.

DEHYDROGENATION OF PROPANE (PDH) TO PROPYLENE HAS RECEIVED CONSIDERABLE ATTENTION AS AN ALTERNATIVE REACTION OF STEAM CRACKING AND FLUID CATALYTIC CRACKING OF NAPHTHA. PDH IS KNOWN AS ONE OF ON-PURPOSE PRODUCTION METHODS TO MEET THE INCREASING DEMAND FOR PROPYLENE. THE CONVENTIONAL CATALYST OF DEHYDROGENATION PROCESS IS PT-ɤAL2O3 WHICH WOULD HAVE THE PROBLEM OF LARGE PORE VOLUME, THEREFORE LOWER SELECTIVITY TOWARDS PROPYLENE.SAPO-34 WOULD BE A GOOD CHOICE FOR THE HIGHER SELECTIVITY OF PDH PROCESS TO PROPYLENE PRODUCTION BECAUSE OF ITS SUITABLE PORE SIZE AND GREAT SHAPE SELECTIVITY. HOWEVER ITS NARROW PORE OPENINGS CAN BE IMMIDIATELY BLOCKED DUE TO THE FORMATION OF COKE OR OTHER HEAVY INTERMEDIATES WHICH CAN REDUCE CONVERSION AND SELECTIVITY DURING THE LONG TIME PROCESS. THEREFORE, MODIFIED SAPO-34 CATALYST WITH HIERARCHICAL STRUCTURE HAS BEEN CHOSEN IN ORDER TO IMPROVE CATALYTIC ACTIVITY TO A DESIRED POINT.IN THIS RESEARCH, HIERARCHICAL AND REGULAR NANO-STRUCTURE SAPO-34 ARE IMPREGNATED WITH PT+IV-SN+II COMPLEX SOLUTIONS. CATALYTIC PERFORMANCE OF PREPARED SAMPLES ARE MEASURED IN A TUBULAR PACKED BED REACTOR FOR PROPANE DEHYDROGENATION AT ATMOSPHERIC PRESSURE AND 600OC. FINALLY, COMPARATIVE TESTS HAVE BEEN CARRIED OUT WITH INDUSTRIAL PT-SN/ɤAL2O3 CATALYST UNDER IDENTICAL CONDITIONS. THE RESULTS HAVE SHOWN THAT HIERARCHICAL SAPO-34 WAS THE EFFECTIVE CATALYST WITH HIGH SELECTIVITY AND CONVERSION THAN THE OTHER CATALYSTS. HOWEVER THE STABILITY OF THE HIERARCHICAL CATALYST WAS LESS THAN INDUSTRIAL CATALYST BUT HIGHER THAN REGULAR SAPO-34.

THE PRODUCTION OF LIGHT OLEFINS FROM METHANOL (METHANOL-TO-OLEFINS OR MTO PROCESS) IS AN INTERESTING ROUTE FOR RESEARCHERS OF THE PETROCHEMICAL INDUSTRY.1 SAPO-34 MOLECULAR SIEVE WITH A PORE SIZE OF 0.43-0.50 NM...

THE SAPO-34 CATALYST WAS SYNTHESIZED USING TETRAETHYL ORTHOSILICATE (TEOS) OR SILICA GEL (SG) AND ALUMINIUMISOPROPOXIDE (AIP) OR ALUMINIUMHYDROXIDE (AH) AS SOURCES OF SI AND AL, RESPECTIVELY UNDER HYDROTHERMAL CONDITIONS. THE EFFECT OF SILICON AND ALUMINIUM SOURCE ON THE PHYSICOCHEMICAL PROPERTIES OF EACH CATALYST WAS STUDIED BY XRD, SEM AND FTIR TECHNIQUES. SEM PHOTOS SHOWED THAT ALL THE CATALYSTS HAVE CUBIC MORPHOLOGY, BUT THEIR PARTICLE SIZE WAS DIFFERENT. THE CATALYTIC PERFORMANCE OF THE SYNTHESIZED CATALYSTS WAS TESTED IN MTO REACTION. THE CATALYST PRODUCED BY SILICA GEL AND ALUMINIUM ISOPROPOXIDE AS SOURCES OF SI AND AL, RESPECTIVELY EXHIBITED THE HIGHEST LIGHT OLEFINS SELECTIVITY. THE MAXIMUM SELECTIVITY OF ETHYLENE AND PROPYLENE WAS DETERMINED TO BE 95 WT% WITH 100% METHANOL CONVERSION.