Abstract
An efficient elevated-pressure catalytic oxidative process (2.5 mol % Co(NO3)2, 2.5 mol % MnBr2, air (30 bar), 125 °C, acetic acid, 6 h) has been developed to oxidize p-cymene into crystalline white terephthalic acid (TA) in ∼70% yield. Use of this mixed Co2+/Mn2+ catalytic system is key to obtaining high 70% yields of TA at relatively low reaction temperatures (125 °C) in short reaction times (6 h), which is likely to be due to the synergistic action of bromine and nitrate radicals in the oxidative process. Recycling studies have demonstrated that the mixed metal catalysts present in recovered mother liquors could be recycled three times in successive p-cymene oxidation reactions with no loss in catalytic activity or TA yield. Partial oxidation of p-cymene to give p-methylacetophenone (p-MA) in 55–60% yield can be achieved using a mixed CoBr2/Mn(OAc)2 catalytic system under 1 atm air for 24 h, while use of Co(NO3)2/MnBr2 under 1 atm O2 for 24 h gave p-toluic acid in 55–60% yield. Therefore, access to these simple catalytic aerobic conditions enables multiple biorenewable bulk terpene feedstocks (e.g., crude sulfate turpentine, turpentine, cineole, and limonene) to be converted into synthetically useful bio-p-MA, bio-p-toluic acid, and bio-TA (and hence bio-polyethylene terephthalate) as part of a terpene based biorefinery.
Highlights
Biorefineries are predicted to play an increasingly important role in the sustainable transformation of biomass into the diverse range of chemical products and fuels that are currently sourced from petrochemicals.[1−3] The forestry industry has pioneered use of the biorefinery concept for more than 150 years, with the Kraft paper making process used to transform wood chips into paper generating significant amounts of other sustainable product streams, including Kraft lignin, crude tall oil, and crude sulfate turpentine (CST).[2]
With viable routes to transform biorenewable bulk terpene feedstocks into bio-p-cymene established, we wanted to identify optimal catalytic aerobic conditions to convert it into bio-terephthalic acid (TA).[32]
Development of controllable catalytic aerobic conditions that would allow selective oxidation of the isopropyl group of bio-p-cymene had the advantage of potentially affording bio-p-MA and bio-p-toluic acid as alternative biorenewable products
Summary
Biorefineries are predicted to play an increasingly important role in the sustainable transformation of biomass into the diverse range of chemical products and fuels that are currently sourced from petrochemicals.[1−3] The forestry industry has pioneered use of the biorefinery concept for more than 150 years, with the Kraft paper making process used to transform wood chips into paper generating significant amounts of other sustainable product streams, including Kraft lignin, crude tall oil, and crude sulfate turpentine (CST).[2]. Significant quantities of other biorenewable p-MeD feedstocks are available as byproducts of acid catalyzed hydrolysis processes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
