Formation of C–C bonds for the production of bio-alkanes under mild conditions

Abstract

It is of crucial importance to form C-C bonds between biomass-derived compounds for the production of bio-alkanes from biomass. In this study, it was found that C-C bonds can be formed between angelica lactones, key intermediates derived from biomass, through free radical reactions under mild conditions without using a noble catalyst or solvent, which gave elongated carbon chains of di/trimers with 10 or 15 carbons, with complete conversion and 100% selectivity. The di/trimers produced serve as a novel feedstock for the carbon backbones of bio-alkanes. Hydrogenation of the di/trimers produced C6-C13 hydrocarbons suitable for use as transportation fuels.Biomass is regarded as a possible renewable resource for fuels and chemicals. Current approaches for the conversion of biomass feedstocks into liquid fuels involve their gasification to syngas followed by Fischer-Tropsch synthesis, thermal liquefaction and fermentation. 1 These approaches have one or more drawbacks, including the poor fuel properties of the products, low conversion efficiencies, low heating values, long treatment times or high processing costs. Recently, acid hydrolysis to give sugars followed by aqueous-phase processing (APP) to yield liquid fuel has attracted much interest. 2-7 The APP process can convert biomass-derived sugars into liquid fuels with an energy recovery as high as 96% and is believed to be a promising route for industry-scale technology. 8 However, the process needs sugars as the raw materials and the production of sugars is costly, and sugars tend to produce dehydration products like hydroxylmethylfurfural or humins in the presence of water and an acid catalyst, thus decreasing the yield of the target products. [9][10][11] Furthermore, typical gasoline and diesel fuels are hydrocarbons 6 to 13 carbons in length, while the major monomeric building blocks of biomass are carbohydrates which have 5 or 6 carbons. In order to meet the required fuel specifications, new C-C bonds have to be constructed between sugar-, cellulose-or hemicellulose-derived furan compounds. Ketonization and aldol condensation have been found to be effective for the purpose. However, ketonization has to be carried out at 623 K and 5.7 MPa with Pd or Pt as the catalysts, 12 while aldol condensation needs a ketone as a reactant and low yields have always existed in this reaction. 3,13 In this respect, it is desirable to develop an efficient process that can convert widespread biomass without extensive pretreatment to liquid alkanes, similar to those that have been used for many years from petroleum resources, 14-16 and to design an effective C-C bond formation reaction between biomass-derived compounds under mild conditions. Herein, we introduce an integrated process that converts commonly available biomass into gasoline range alkanes. 17 The strategies of this process are to form elongated-carbon-chain oxygenated intermediates from functional chemicals produced from biomass, and then to remove the oxygens of the intermediates by hydrodeoxygenation to produce ga...

Angelica Lactones: From Biomass‐Derived Platform Chemicals to Value‐Added Products

“…In this case, the group notes that the temperature of the reaction has a strong influence on the α‐AL/β‐AL ratio. In all cases, α‐AL is formed as the major product, but higher temperatures favor the appearance of β‐AL among the products, which thus decreases the selectivity of the process …”

“…Currently, it is known that the lactonization of levulinic acid followed by dehydration in acid medium leads to the formation of α‐AL, which can then be isomerized to β‐AL by using acidic or basic catalysts. S. Zhang's group, for instance, has observed that a H‐ZMS‐5/SiO 2 catalyst system is able not only to dehydrate levulinic acid to α‐AL but also to isomerize it to β‐AL in a one‐pot fashion . However, alternative approaches can be employed to obtain β‐AL.…”

“…Following a similar path, S. Zhang's group has described the K 2 CO 3 ‐catalyzed production of ALD and AL trimer (ALT) followed by their conversion into branched alkanes under relatively mild conditions (Scheme ) . The group has evaluated several catalysts for the production of α‐AL from levulinic acid (see Section 2.1) and for the formation of dimers and trimers from ALs.…”

“…In all cases, a-AL is formed as the major product, but higher temperatures favor the appearance of b-AL among the products, which thus decreasesthe selectivity of the process. [20] Aside from distillation approaches,L Ac an also be converted into ALs under vapor-phase reactions. By this path, in 2016 Sun et al reported the preparation am esoporous silica type catalysta nd its use in the vapor-phase conversion of LA into a-AL.…”

Production of renewable long-chained cycloalkanes from biomass-derived furfurals and cyclic ketones

“…[24][25][26][27] Despite the fact that the precursor could be converted into branched long-chain hydrocarbons, the main drawback was that only hemicellulose (the least abundant component in a typical lignocellulosic biomass) could be utilized. Interestingly, alternative routes including direct C-C bond formation by condensation of monosaccharides/furfurals, 28 a-alkylation of ketones with 1-butanol, 29 self-coupling by two HMF molecules 30 and oligomerization of angelica lactone 31,32 were used to produce C 10 -C 15 precursors with high yields, and hydrodeoxygenation to the relative long-chained hydrocarbons was then conducted over supported metal catalysts. Instead of the common furfurals, these routes extended the platform molecules for target hydrocarbons by using diversied structures.…”