Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-19ACTIVITY AND DEACTIVATION OF ACIDIC CATALYSTS AT THEDEHYDRATION OF GLYCEROLWladimir Suprun, Carsten Frohberg, Robert Oltroge, Helmut PappInstitut für Technische Chemie, Linnéstraße 3, 04103 Leipzig, GermanyFax:+ (49) 341 9736473; e-mail: suprun@chemie.uni-leipzig.deItroduction. In recent years, the increasing of biodiesel production has resulted in a pricedecline of raw glycerol, which make the aqueous glycerol as attractive compound for thesynthesis of fine and crude chemicals [1]. The conversion of glycerol to acroleine opened anew route for a production of acrylate monomers from renewable raw materials [1-3]. Thedehydration of glycerol in gaseous phase on acidic catalyst proceeds via formation of3-hydroxypropionaldehyde (3-HPA) and 2-hydroxyacetone (2-HOAC) [1, 4]. The highestobserved selectivity to acrolein was 55-70%. Moreover a formation of a large amount of byproducts(25-40%) and catalyst deactivation was reported. In order to understand themechanism of acrolein formation, we investigated the catalytic activity of solid supportedphosphates (Al 2 O 3 /PO 4 , TiO 2 /PO 4 ) and selected SAPO samples in the dehydration ofglycerol. Additionally the reactivity of 3-HPA and 2-HOAC toward dehydration anddeactivation of acid catalysts in presence of water was studied.Experimental. Al 2 O 3 -PO 4 , TiO 2 -PO 4 catalysts are prepared by impregnation methods,using H 3 PO 4 solution and corresponded support or by sol-gel co precipitation of metalhydroxides with H 3 PO 3 . SAPO-34 and SAPO-11 were prepared by hydrothermal synthesis.The crystal structure of catalysts were characterised by X-ray diffraction, elemental analysis,XPS and thermal analysis (TG/DTA, TPO and NH 3 -TPD). The gas-phase dehydration ofglycerol and C3-hydroxy carbonyl compounds was conducted under atmospheric pressure infixed-bed reactor. Before reaction catalyst were pre-treated for 5h in presence of water streamat 350°C, The reactions products of glycerol dehydration were condensed analysed by GC.The reactions product of 3-HPA and 2-HOAC thermolysis or decomposition were alsoanalysed by online MS (Omni-Star; GSD-200C, Balzer-Pfeiffer-Vacuum) and GC/MS(Varian/Saturn).Result and Discussions. Gas-phase dehydration of glycerol to produce acrolein wasinvestigated at 325°C. The glycerol conversion and selectivity to acrolein and to side productsdepended on reaction conditions and strength of acids site. Other by-products includedacetone, acetaldehyde, propionaldehyde, allylalcohl and 2-HOAC. Moreover a large amount(~ 25 %) of C6 compounds (Adol-condensation of 2-HOAC) were identified by GC/MS.62