Abstract
The conversion of 1,4-butanediol (BDO) to tetrahydrofuran (THF) in aqueous phase is desirable because BDO production technology is shifting to bio-based aqueous fermentation routes. In this study, liquid-phase cyclodehydration of BDO to THF was studied in two reaction media (pure BDO and aqueous BDO feeds) at 200–240 °C using ZrO2-Al2O3 (ZA) mixed oxides, which were made with a co-precipitation method and were characterized with XRD, BET, SEM/EDX, pyridine and n-butylamine adsorptions. The maximum acidity and the largest surface area occurred at Zr/Al atomic ratios of 1/1 (ZA11) and 1/3 (ZA13), respectively. The reaction exhibited pseudo-first-order; aqueous BDO feed had much greater rate constant than pure BDO feed, ascribed to the acidic properties of adsorbed water molecules (coordinated to surface metal cations) for the former case. For pure BDO feed, linear relation was observed between rate constant and catalyst acidity, and ZA11 reached a THF yield of 90.1% at 240 °C. With aqueous BDO feed, rate constant increased linearly with increasing surface area and ZA13 reached a THF yield of 97.1% at 220 °C. The change of optimum catalyst composition with reaction medium suggests that active sites for catalyzing BDO cyclodehydration changed with the reaction environment.
Highlights
In the commercial processes based on allyl alcohol and Materials 2019, 12, 2092; doi:10.3390/ma12132092
In the commercial processes based on allyl alcohol and propylene oxide, 1,4-BDO is produced by hydrogenation of 4-hydroxyburaldehyde in aqueous solutions [5,6]
We found that the optimum Zr-Al catalyst composition changed with reaction medium, which was ascribed to the change of active sites for BDO cyclodehydration
Summary
Tetrahydrofuran (abbreviated as THF) is an important fine chemical intermediate and a powerTfeutrlaohrygdarnoifcursaonlv(aebnbt.reMvioastetdTaHs FTHpFr)oidsuacntiiomnpiosrtuansetdfinteochmeamkiecapl oinlytetremtraemdieattheyalnednea pgolywceerrfoull (aobrgbarenviciastoeldveanst.PMTMosGt T, HalFsoprkondouwctnioansispuolsye-dTHtoFm),awkehipcohlyitsetursaemdetihnytlheneepgrloydcuercotilo(nabobfreuvrieattheadnaes ePlaTsMtoGm,earlss,o kpnoolywunreatshpaonley-TfiHbeFr)s, w(ehtihcehri-sbuasseedd inspthaendperoxd),ucatniodn ocof puorelytheasnteere-elathsteormeelrass,tpoomlyeursr.ethTahnee rfiembearisn(ientgheTrH-bFasperdosdpuacntidoenx)i,saunsdedcoapsoalyseosltveer-netthfoerr tehlaesmtomaneurfsa. Ercial petroleum-derived BDO technologies include acetylene based process, butaTdhieenec-obmasmederpcrioalcespse,tmroaleleuimc a-dnheryidvreidde-BbDasOedtpecrohcneoslso,gpireospyinlecnlued-beasaecdeptyrloecneess bvaiaseadllypl arolccoehsso,l, butadiene-based process, maleic anhydride-based process, propylene-based process via allyl alcohol, and propylene oxide based process. In the commercial processes based on allyl alcohol and Materials 2019, 12, 2092; doi:10.3390/ma12132092 www.mdpi.com/journal/materials. Materials 2019, 12, x; doi: FOR PEER REVIEW www.mdpi.com/journal/materials. Materials 2019, 12, 2092 and propylene oxide based process. In the commercial processes based on allyl alcohol and propylene oxide, 1,4-BDO is produced by hydrogenation of 4-hydroxyburaldehyde in aqueous solutions [5,6]. It is better to convert 1,4-BDO to THF in aqueous solutions without water removal because the separation of BDO and water is costly
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