ΚΑΤΑΛΥΤΙΚΗ ΟΞΕΙΔΩΣΗ ΤΟΥ ΔΙΟΞΕΙΔΙΟΥ ΤΟΥ ΘΕΙΟΥ ΣΕ ΤΗΓΜΑΤΑ ΑΛΑΤΩΝ. ΣΧΗΜΑΤΙΣΜΟΣ ΚΡΥΣΤΑΛΛΙΚΩΝ ΕΝΩΣΕΩΝ ΚΑΙ ΑΠΕΝΕΡΓΟΠΟΙΗΣΗ ΤΟΥ ΚΑΤΑΛΥΤΗ

THE FORMATION OF LOW VALENCE CRYSTALLINE VANADIUM COMPOUNDS WAS STUDIED IN THE V2O5-M2S2O7 (M=NA, K, CS) UNSUPPORTED MELT SYSTEMS IN THE TEMPERATURE RANGE 350-480 C DURING SO2 OXIDATION WITH UNCONVERTED 10% SO2, 11% O2 AND 79% N2 AS THE FEED GAS. A GAS- MOLTEN SALT REACTOR SYSTEM WAS BUILT IN SUCH A WAY AS TO PROVIDE THE POSSIBILITY OF ISOLATING THE CRYSTALLINE PRECIPITATES UNDER OPERATING CONDITIONS AT ANY TEMPERATURE BY FILTERING THE CATALYST MELTS. BOTH V(IV) AND V(III) CRYSTALLINE COMPOUNDS WERE FORMED UNDER DIFFERENT PROCESS CONDITIONS. THE V(IV)-COMPOUNDS K4(VO)3(SO4)5, NA2VO(SO4)2 AND CS2(VO)2(SO4)3 AND V(III)- COMPOUNDS KV(SO4)2, NAV(SO4)2 AND CSV(SO4)2 WERE ISOLATED FROM THE MELTS. THE STRUCTURE OF THESE COMPOUNDS HAS BEEN DETERMINED BY X-RAY ANALYSIS. VIBRATIONAL SPECTRA (IR AND RAMAN) OF POLYCRYSTALLINE SAMPLES OF THE ISOLATED VANADIUM COMPLEXES HAVE BEEN RECORDED AND INTERPRETED. A BREAK IN THE ARRHENIUS TYPE PLOTS WAS OBSERVED AT TEMPERATURES WHERE THESE COMPOUNDS STARTED TO PRECIPITATE. FOR THE FIRST TIME IT HAS BEEN POSSIBLE TO OBSERVE THE DROP IN CATALYTIC ACTIVITY AND THE FORMATION OF LOW SOLUBLE VANADIUM COMPOUNDS SIMULTANEOUSLY. IT WAS ALSO FOUND THAT: (I) HIGH ALKALI TO VANADIUM RATIOS, LARGE ALKALI CATION PROMOTERS OR MIXING OF THE ALKALI PROMOTERS CAUSED THE PRECIPITATION AND THE STEEP ACTIVITY DROP TO OCCUR AT LOWER TEMPERATURES AND (II) THE CRYSTALLINE PRECIPITATES OF V(IV) AND V(III) COULD BE REDISOLVED BY A HEAT TREATMENT AT/OR ABOVE 470 C OR BY PURGING THE MELTS WITH N2. THE THERMAL STABILITY OF THE V(IV)-COMPOUNDS HAS BEEN INVESTIGATED BY MEANS OF DTA. FURTHERMORE THE DECOMPOSITION RATE OF KV(SO4)2 AND K4(VO)3(SO4)5 DURING ISOTHERMAL HEATING AT DIFFERENT TEMPERATURES IN THE RANGE 470-510 C HAS BEEN MEASURED AND IR SPECTRA OF THE DECOMPOSITION PRODUCTS HAVE BEEN RECORDED AND INTERPRETED. THE RESULTS INDICATE THAT A HEAT TREATMENT OF MELTS CONTAINING LARGE AMOUNTS OF V(IV) AND V(III) PRECIPITATES LEADS TO REOXIDATION OF VANADIUM IN THE +V OXIDATION STATE. CERTAIN CONDITIONS REQUIRED FOR REACTIVATION OF DEACTIVATED CATALYSTS ARE POINTED OUT AND ARE DISCUSSED IN RELATION TO THE DISOLUTION OF THE PRECIPITATES IN THE MELTS.

Grantor dc:publisher

University of Patras

Year dc:date

1990

Author dc:creator

• Μπογοσιάν, Σόγομων

• ΔΟΜΕΣ ΕΝΩΣΕΩΝ ΤΡΙΣΘΕΝΟΥΣ & ΤΕΤΡΑΣΘΕΝΟΥΣ ΒΑΝΑΔΙΟ
• ΚΑΤΑΒΥΘΙΣΗ ΕΝΩΣΕΩΝ ΚΑΙ ΑΠΕΝΕΡΓΟΠΟΙΗΣΗ ΚΑΤΑΛΥΤΟΥ
• ΚΑΤΑΛΥΣΗ ΣΕ ΤΗΓΜΑΤΑ ΑΛΑΤΩΝ
• ΚΑΤΑΛΥΤΗΣ ΘΕΙΙΚΟΥ ΟΞΕΟΣ
• Οξείδωση διοξειδίου του θείου
• ΣΥΜΠΛΟΚΑ ΒΑΝΑΔΙΟΥ ΣΕ ΛΥΡΟΘΕΙΙΚΑ ΤΗΓΜΑΤΑ
• ΣΧΗΜΑΤΙΣΜΟΣ ΚΡΥΣΤΑΛΛΙΚΩΝ ΕΝΩΣΕΩΝ
• COMPOUND PRECIPITATION AND CATALYST DEACTIVATIO
• Sulfur dioxide oxidation
• SULFURIC ACID CATALYST
• Επιστήμες Μηχανικού και Τεχνολογία
• Επιστήμη Χημικού Μηχανικού
• Engineering and Technology
• Chemical Engineering

Language dc:language

gre

Identifier

10.12681/eadd/1227

OAI identifier oai:identifier

oai:10442/1227