Levulinic Acid Production from Starch Using Microwave and Oil Bath Heating: A Kinetic Modeling Approach

Microwave-assisted deep eutectic solvents/dimethyl sulfoxide system for efficient valorization of sugar bagasse waste into platform chemicals: A biorefinery approach for circular bioeconomy

The exploitation of lignocellulosic biomass (LB) such as sugar bagasse waste in biorefineries is the most cost-effective and favourable sustainable approach to producing essential platform chemicals, materials, and energy environmentally benignly. Herein, a microwave-mediated deep eutectic solvents (DESs)/dimethyl sulfoxide (DMSO) system for efficiently processing LB waste into platform chemicals was proposed thereof. Under optimized appropriate diverse parameters such as solvent varieties, catalyst dosage, DMSO addition, reaction time and temperature, the proposed catalytic system (i.e., microwave mediated DESs/DMSO system) has demonstrated significant yields of 5-hydroxymethylfurfural (5-HMF), furfural (FF) and levulinic acid (LevA) of 31.29 %, 28.38 % and 35.65 %, respectively. These favourable results were obtained at the reaction temperature of 140 °C for 40 min. The anticipated catalytic system's activation energy (Ea) was found to be 29.11 kJ/mol. Hence, a practical, inexpensive and sustainable process with the potential of high-value platform chemicals, explicitly for a sustainable strategy in a circular bioeconomy was proposed.

An insight into the principles of lignocellulosic biomass-based zero-waste biorefineries: a green leap towards imperishable energy-based future

Lignocellulosic biomass (LCB) is an energy source that has a huge impact in today's world. The depletion of fossil fuels, increased pollution, climatic changes, etc. have led the public and private sectors to move towards sustainability i.e. using LCB for the production of biofuels and value-added compounds. A major bottleneck of the process is the recalcitrant nature of LCB. This can be overcome by using various pretreatment strategies like physical, chemical, biological, physicochemical, etc. Further, the pretreated biomass is made to undergo various steps like hydrolysis, saccharification, etc. for the conversion of value-added products and the remaining waste residues can be further utilized for the synthesis of secondary products thus favouring the zero-waste biorefinery concept. Currently, microorganisms are being explored for their use in biorefinery but the unavailability of commercial strains is a major limitation. Thus, the use of metagenomics can be used to overcome the limitation which is both cost-effective and environmentally friendly. The review deliberates the composition of LCBs, and their recalcitrance nature, followed by the structural changes caused by various pretreatment methods. The further steps in biorefineries, strategies for the development of zero-waste refineries, bottlenecks, and suggestions are also discussed. Special emphasis is given to the use of metagenomics for the discovery of microorganisms efficient for zero-waste biorefineries.

Phosphomolybdic acid-catalyzed oxidation of waste starch: a new strategy for handling the OCC pulping wastewater

When old corrugated cardboard (OCC) is returned to the paper mill for repulping and reuse, the starch, which is added to the paper surface as a reinforcement agent, is dissolved into the pulping wastewater. Most of the OCC pulping wastewater is recycled to save precious water resources; however, during the water recycling process, the accumulation of dissolved starch stimulates microbial reproduction, which causes poor water quality and putrid odor. This problem seriously affects the stability of the papermaking process and product quality. In this study, phosphomolybdic acid (H₃PMo₁₂O₄₀, abbreviated as PMo₁₂) was utilized to catalyze the waste starch present in papermaking wastewater to monosaccharides, realizing the resource utilization of waste starch. The results showed that the optimized yield of total reducing sugar (78.68 wt%) and glycolic acid (12.83 wt%) was achieved at 145 °C with 30 wt% PMo₁₂ at pH 2, which is equivalent to 91.51 wt% starch recovered from wastewater for resource utilization. In addition, the regeneration of the reduced PMo₁₂ was realized by applying a potential of 1 V for 2 h. Overall, this study has theoretical significance and potential application value for resource utilization of waste starch in OCC pulping process and cleaner management of OCC waste paper.

Microwave-Assisted Conversion of Carbohydrates

Catalytic conversion of carbohydrates into value-added products and platform chemicals became a trend in recent years. Microwave activation used in the processes of carbohydrate conversion coupled with the proper choice of catalysts makes it possible to enhance dramatically the efficiency and sometimes the selectivity of catalysts. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of carbohydrates, mostly produced from natural resources and wastes (forestry and agriculture wastes) including production of hydrogen, synthesis gas, furanics, and alcohols. The focus is made on microwave technologies used for processing carbohydrates. Of particular interest is the use of heterogeneous catalysts and hybrid materials in processing carbohydrates.

A review on solid acid catalysis for sustainable production of levulinic acid and levulinate esters from biomass derivatives

Biomass is a kind of renewable and abundant resource that can be seen as an important candidate to solve the energy crisis. Levulinic acid (LA) and levulinate esters (LEs) have been widely researched as biomass-based platform compounds. In recent years, efficient, green, and environment-friendly solid acid catalysts have been developed for the fast production and resolution of the problems, such as low yield, high equipmental requirements, and difficulty in product separation, in the preparation of LA and LE from biomass. In this paper, the preparation routes of LA and LEs from various raw materials are introduced, and the solid acid catalysts involved in their production are emphatically reviewed. The challenges and prospects in LA and LE production from biomass are proposed to achieve a more economical and energy efficient process with the concept of sustainable development in the future.

Different Reactivity of Raw Starch from Diverse Potato Genotypes

Potato starch is one of the most important renewable sources for industrial manufacturing of organic compounds. Currently, it is produced from mixed potato varieties that often are harvested from different fields. Meanwhile, tuber starches of various potato breeds differ in their crystallinity, granule morphology, and other physical and chemical parameters. We studied the reactions of raw potato starches of different origins to chemical and biochemical reactions typically used for industrial starch modification. The results clearly demonstrate that there is a significant difference in the reactivity of the starches of different potato genotypes. While the main products of the transformations are the same, their preparative yields differ significantly. Thus, tuber starch of certain potato varieties may be more suitable for specific industrial purposes. Starch reactivity may potentially be a phenotypical trait for potato breeding to obtain potato starches for various industrial applications.

Experimental and kinetic study of the conversion of waste starch into glycolic acid over phosphomolybdic acid

The starch used to enhance the paper surface dissolves in water during the production process and forms pollutants that accumulate in water when old corrugated cardboard (OCC) is returned to a paper mill for pulping and reuse. At present, anaerobic fermentation is widely used in the paper industry to treat starch-containing wastewater, producing biogas energy, or oxidative decomposition, which is a huge waste of valuable starch resources. Phosphomolybdic acid (PMo₁₂) is a highly selective catalyst for the oxidation of carbohydrates; therefore, PMo₁₂ can be envisaged as a suitable catalyst to convert waste starch into glycolic acid, an important high added-value chemical. In this paper, the catalytic oxidation technology of PMo₁₂ was explored to produce glycolic acid from starch contained in OCC papermaking wastewater, and the kinetics and influencing factors of the catalytic oxidation reaction were studied. The results indicated that the PMo₁₂-catalyzed oxidation of starch followed a first-order reaction; the reaction rate constant increased with increasing the temperature, the apparent activation energy of starch to monosaccharide was 104.7 kJ mol⁻¹, the apparent activation energies of starch and monosaccharide to humins were 126.5 and 140.5 kJ mol⁻¹, and the apparent activation energy of monosaccharide to glycolic acid was 117.2 kJ mol⁻¹. The yields of monosaccharide and glycolic acid were 80.7 wt% and 12.9 wt%, respectively, and the utilization of starch resources was about 90.0 wt% under the following reaction conditions: temperature, 145 °C; reaction time, 120 min; pH, 2. Therefore, the feasibility of the PMo₁₂-catalyzed oxidation of starch to produce high value-added glycolic acid is demonstrated, which has theoretical guiding significance and potential application value for the clean production and resource utilization of waste starch in the OCC papermaking process.

The starch in old corrugated cardboard (OCC) wastewater is catalyzed and oxidized to produce high value-added glycolic acid, which has potential application value for the clean production and resource utilization of waste starch in the OCC papermaking process.

Catalytic Production of Levulinic Acid (LA) from Actual Biomass

Catalytic conversion of actual biomass to valuable chemicals is a crucial issue in green chemistry. This review discusses on the recent approach in the levulinic acid (LA) formation from three prominent generations of biomasses. Our paper highlights the impact of the nature of different types of biomass and their complex structure and impurities, different groups of catalyst, solvents, and reaction system, and condition and all related pros and cons for this process.

Valorization of lignocellulosic fibres of paper waste into levulinic acid using solid and aqueous Brønsted acid

This study aims to produce levulinic acid (LA) from paper towel waste in environment-friendly and economically feasible conditions, and evaluate the difference using solid and aqueous Brønsted acids. Direct dehydration of glucose to LA required sufficiently strong Brønsted acidity, where Amberlyst 36 demonstrated rapid production of approximately 30Cmol% of LA in 20min. However, the maximum yield of LA was limited by mass transfer. In contrast, the yield of LA gradually increased to over 40Cmol% in 1M H₂SO₄ at 150°C in 60min. The SEM images revealed the conversion in dilute acids under microwave at 150°C resulting in swelling structures of cellulose, which were similar to the pre-treatment process with concentrated acids. Further increase in reaction temperature to 200°C significantly shortened the reaction time from 60 to 2.5min, which saved the energy cost as revealed in preliminary cost analysis.