Advances in understanding the humins: Formation , prevention and application

Liu, Siwei; Zhu, Yuting; Liao, Yuhe; Liu, Qiying; Ma, Longlong; Wang, Chenguang

doi:10.1016/j.jaecs.2022.100062

Cited by 50 publications

(80 citation statements)

References 125 publications

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“…Both ethanol and DMSO are alternative polar organic solvents, with ethanol as an example of a protic and DMSO as an example of an aprotic solvent. The formation of humins is usually impeded by non-aqueous solvents [ 9 , 18 , 40 ]; therefore, we expected a molar 1:1 mixture of water and the organic solvents to exhibit lower humin formation than pure H 2 O. The sugars and solvents were combined with three different acid catalysts: sulfuric acid (pK a of −3) was chosen as a strong inorganic acid, which is also commonly used in industrial acid catalysis [ 3 ].…”

Section: Resultsmentioning

confidence: 99%

“…In the latter, insoluble black solid polymers are formed, which are called humins [ 2 , 3 , 4 ]. They are formed during the acid-catalyzed conversion of carbohydrates below a temperature of 250 °C [ 5 , 6 , 7 , 8 , 9 ]. Humins are particularly problematic for industrial processes, as they clog up both reactor and catalyst, and signify a waste of resources into an unusable side product [ 10 , 11 , 12 , 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

“…This was eventually confirmed by the subsequent research of multiple research groups such as Tsilomelekis et al [ 13 ] and Shen et al [ 30 ]. Numerous other insights were made concerning the formation of humins, resulting in the reaction mechanism for hexoses to humins by Siwei et al in Figure 1 [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

“…During this process, catalysts and solvent molecules are also incorporated into the humin structure through polymerization with oligomers or through absorption [ 11 , 13 , 33 , 34 , 35 ]. The resulting particles will then agglomerate step by step into a foam-like humin coke [ 9 ]. Although this research identified structural motifs of humins, details of their structure remain unknown due to their overall very complex composition.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the Formation, Characterization, and Oxidative Catalytic Valorization of Humins

et al. 2023

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The industrial use of biomass, e.g., for the production of platform chemicals such as levulinic acid, became increasingly important in recent years. However, the efficiency of these processes was reduced by the formation of insoluble solid waste products called humins. Herein, the formation of humins from various carbohydrates was investigated under different process conditions, in order to obtain information about the structure and the formation mechanism. During this process, new potential structural fragments of humins were identified. Subsequently, the produced humins were oxidatively converted to low-molecular-weight carboxylic acids with the use of polyoxometalate catalysts. The experiments showed that the use of sugars in acetic acid and ethanol only lead to the formation of a small amount of humins, which were also structurally most suitable for conversion to carboxylic acids. The main products of the oxidative valorisation of these humins were acetic acid, formic acid, and CO2, respectively, and our results indicate that certain functional groups were converted preferentially. These findings will help to improve processes for the valorisation of biomass by enabling an overall more efficient use of thermo-sensitive feedstock such as carbohydrates.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of the Formation, Characterization, and Oxidative Catalytic Valorization of Humins

et al. 2023

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“…The theoretical H/C and O/C ratios for polymerized furfural are H/C = 0.8 and O/C = 0.4, according to the polymerization scheme provided in Zeitsch, which is not very different from the measured values for the black particles that average H/C = 0.88 and O/C = 0.26. Aside from these differences, the black particles share many similarities in both properties and apparent structure with both humins [24] and pseudo-lignins, which is another class of solid by-product. Pseudo-lignins are derived from condensation reactions between dehydrated polysaccharides, such as HMF and furfural, that take place during high-severity pretreatment of lignocellulosic biomass in the presence of acids (Fig.…”

Section: Discussionmentioning

confidence: 99%

Investigating solids present in the aqueous stream during STEX condensate upgrading—a case study

Hermundsgård

Ghoreishi

Tanase-Opedal³

et al. 2022

Biomass Conv. Bioref.

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Steam explosion (STEX) of woody biomass is an efficient pretreatment method in the production of water-resistant wood pellets. The STEX process also generates an aqueous condensate stream containing dissolved organic compounds, with furfural as the most abundant and valuable component. An industrial-scale recovery process for furfural and other organic by-products is therefore in the process of being developed and built. One challenge in the process has turned out to be the formation of solid particulate matter that can clog filters in the process unit. We have analyzed both the solid deposits and the fluids present at different points in the process unit to try to identify the origin of the particles using spectroscopic and chromatographic analysis, elemental analysis, and scanning electron microscopy.The aqueous fluids deriving from condensed steam contain furfural and other small organic molecules, with a separate low-density organic layer occurring at some points. This layer largely consists of wood extractives, typically terpenoids. In addition, a heavy organic phase comprising mostly furfural was found at one sampling point. The particles comprise a black, largely insoluble material with a H/C ratio of 0.88 and an O/C ratio of 0.26 and a very low ash content. IR spectra show a low content of C–H functional groups, and chromatographic analysis supports an interpretation that the particles are dominantly furfural-sourced humin-like polymers with adsorbed or co-polymerized terpenoids. Particle formation has been reproduced in a laboratory setting with conditions similar to those in the full-scale process.

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