Comparison of batch and continuous operating mode of the reactor for C-O hydrogenolysis of erythritol on Ir-Re catalysts

EMANUEL VIRGILIO; LUDMILA N. CHORVAT; CRISTINA LILIANA PADRÓ; MARÍA EUGENIA SAD

Santa Fe

Workshop; French-Argentinian Workshop on Heterogeneous Catalysis; 2023

Institute of Research on Catalysis and Petrochemistry, ?Ing. José Miguel Parera?, INCAPE (CONICET - UNL)

New processes starting frombiomass derivatives are replacing the traditional synthesis of numerouschemicals involving sources of fossil origin. As a disadvantage, thebiomass-derived molecules typically contain excess of oxygen that must beremoved to render valuable chemicals. C-O hydrogenolysis is a key reaction forthe conversion of polyols and sugar alcohols to platform molecules because itallows the removal of oxygen while preserving the number of carbon atoms of thestarting molecule. Erythritol (C4H10O4, ERY)is commercially produced through fermentation of glucose and sucrose from chemicallyand enzymatically hydrolyzed wheat and corn starches. It is considered as aplatform molecule and then, susceptible to participate in attractive chemicaltransformations, such as C-O hydrogenolysis, conducting to valuable productslike butanediols (BDO) which are important chemicals used in the industry ofsynthetic rubber and polymers, among many other uses.The direct hydrogenolysis of ERY to produce butanediols was previouslyreportedusing 4 wt.% Ir–ReOx/SiO2 catalyst (Ir/Re=1);the selectivity to butanediols reached was 48% at 74.2 % conversion at 100ºCand PH2=80 bar after 24 h of reaction. Some more recent researchhave been developed in order to improve to BDO yield by changing the noblemetal (Ir, Rh, Pt), the oxide promoter (Re, W, Mo) and the support but onlybatch reactors were used for ERY reactions. The goal of this work is tocompare the catalytic activity of two Ir and Re bimetallic catalysts withdifferent physicochemical and acidic properties in the reaction of ERY to BDOusing a batch and a continuous reactor. ERY may react in presence of H2through four main routes: C-O hydrogenolysis (CO), C-C bond cleavage (CC),dehydration (DH), and isomerization (ISO). The primary products from C-Oscissions from ERY are the butanetriols that can be converted into BDO by a second C-O hydrogenolysis; the over-C-Ohydrogenolysis is, however, undesirable because butanols and butane may beformed and transferred to gas phase. In batch process, the ERY conversion toliquid products was similar on Ir-Re/TiO2 and Ir-Re/Al2O3but the TiO2 catalyst favored the C-O scissions more than Al2O3-basedcatalyst that promoted dehydration reactions. At these conditions, ERYconversion to gas products and gaseous products distribution were similar onboth catalyst. The main difference between these two solids was the higheracidity of alumina, as well as the presence of slightly reduced Re species, andlower accessibility of Ir on Ir-Re/Al2O3. In addition,the catalysts were tested in a continuous reactor at the same temperature. Forthis operating mode, the ERY conversion was almost total on both catalysts.However, only Ir-Re/TiO2 favored the C-O hydrogenolysis to renderliquid products such as BDO (XL≈70% and 56% of products from C-O hydrogenolysis within liquid) whereas the highacidity of Ir-Re/Al2O3 clearly promoted dehydrationreactions with 1,4anhydroerhytritol as main compound and also formed highamounts of products from C-C scissions in gas phase (mainly methane). ISO (threitolformation) was negligible compared to batch reactor that can be attributable tothe high conversion reached. Catalyst acidity and theoperating mode influence on the activity and selectivity to different routesduring ERY reactions. The highest BDO productivities were achieved on Ir-Re/TiO2(60 and 80 mmol/gIr.h for batch and continuous reactorrespectively).