Abstract
We report the use of five alpha-hydroxy acids (citric, tartaric, mandelic, lactic and glycolic acids) as catalysts in the synthesis of terpineol from alpha-pinene. The study found that the hydration rate of pinene was slow when only catalyzed by alpha-hydroxyl acids. Ternary composite catalysts, composed of AHAs, phosphoric acid, and acetic acid, had a good catalytic performance. The reaction step was hydrolysis of the intermediate terpinyl acetate, which yielded terpineol. The optimal reaction conditions were as follows: alpha-pinene, acetic acid, water, citric acid, and phosphoric acid, at a mass ratio of 1:2.5:1:(0.1–0.05):0.05, a reaction temperature of 70 °C, and a reaction time of 12–15 h. The conversion of alpha-pinene was 96%, the content of alpha-terpineol was 46.9%, and the selectivity of alpha-terpineol was 48.1%. In addition, the catalytic performance of monolayer graphene oxide and its composite catalyst with citric acid was studied, with acetic acid used as an additive.
Highlights
Terpineol has an aroma similar to lilac
To address the strong corrosion in alphaterpineol synthesis when sulfuric acid is used as a catalyst, Román-Aguirre et al used hydrochloric acid, acetic acid, oxalic acid, and monochloroacetic acid (MCA) as catalysts for the direct synthesis of terpineol from alpha-pinene [3]
The content of alpha-terpineol increased by 9.7%, and the selectivity increased by 5.6% with citric acid
Summary
Terpineol has an aroma similar to lilac. It is present in a variety of essential oils and is widely used in the fragrance industry. Chen et al used solid superacid Ni/SO42−-SnO2 as a catalyst and MCA as the promoter to synthesize alpha-terpineol from alpha-pinene [8]. Chen et al used solid superacid Ni/SO42−-SnO2 as a catalyst and MCA a2sotfh1e6 promoter to synthesize alpha-terpineol from alpha-pinene [8]. They are environmMenotsatllaylpfhriae-nhdyldyr,onxoyna-ctoidxsic(AtoHhAusm) aanreswaniddealynidmisatrlsib, uanteddminilndalytucroe.rrTohseivyeatroewenarvdiroren-amcetinotnalelyqufriipemndelnyt,.nHoenr-eto, xwice tuoshedumcoamnsmaonndAanHimAsal(sc,itarnicdamciidld, lLy-(c+o)r-rtaorstiavreictoawciadr,dDrLea-mctaionndeqeulicip, mL-e(+n)t-.laHcteirce,acwide,uasnedd gcloymcomliocnacAidH)Aass (ccaittarliycsatcsidfo,rLa-(lp+h)-ata-prtianreinceachiydd, rDatLio-mn a[n21d–e2li3c], aLn-(d+)t-hlaecntiicnavceisdt,igaantdedglayncdolcicoamcpida)raesdctahteailrysctastafolyrtaiclpphear-fpoirnmenane cheyadnradtiroenac[t2i1o–n2s3t]eapnsd. AAllpphhaa--ppiinneennee hhyyddrraattiioonn wwaass ccaattaallyyzzeedd bbyy ffiivvee AAHHAAss ((cciittrriicc aacciidd,, LL--((++))--ttaarrttaarriicc aacciidd,, DDLL--mmaannddeelliicc,, LL--((++))--llaaccttiiccaacciidd,,aanndd ggllyyccoolliicc aacciidd)).
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