Vitaliy L. Budarin

Direct Microwave-Assisted Hydrothermal Depolymerization of Cellulose

A systematic investigation of the interaction of microwave irradiation with microcrystalline cellulose has been carried out, covering a broad temperature range (150 → 270 °C). A variety of analytical techniques (e.g., HPLC, (13)C NMR, FTIR, CHN analysis, hydrogen-deuterium exchange) allowed for the analysis of the obtained liquid and solid products. Based on these results a mechanism of cellulose interaction with microwaves is proposed. Thereby the degree of freedom of the cellulose enclosed CH2OH groups was found to be crucial. This mechanism allows for the explanation of the different experimental observations such as high efficiency of microwave treatment; the dependence of the selectivity/yield of glucose on the applied microwave density; the observed high glucose to HMF ratio; and the influence of the degree of cellulose crystallinity on the results of the hydrolysis process. The highest selectivity toward glucose was found to be ~75% while the highest glucose yield obtained was 21%.

Valorisation of Orange Peel Residues: Waste to Biochemicals and Nanoporous Materials

FRUIT FOR THOUGHT: Low-temperature microwave hydrothermal processing of orange peel not only enables the separation of the major components but also adds further value through the production of other high-value products: pectin and D-limonene, together with a rare form of mesoporous cellulose, are produced in a single step, without added acid. A process temperature change enables the conversion of D-limonene to α-terpineol.

Microwave-mediated pyrolysis of macro-algae

Macro-algae (seaweed) is an abundant and, for the most part, under-utilised resource. This study has shown that microwave (MW)-mediated pyrolysis of seaweed occurs at extremely low temperatures and produces chemical rich bio-oils which are rich in aromatics, sugars and other high value chemicals.

Applications of nanoparticles in biomass conversion to chemicals and fuels

Biorefineries are facilities that process biomass into fuels, power and value-added chemicals and with the increasing population and depleting petroleum reserves they are fast becoming more important to society. The technology required to process a wide variety of biomass types can be highly complex due to potentially unknown, varying or difficult to breakdown chemical structures within them. One of the prospective routes to a successful biorefinery, that can treat a wide range of biomass and produce products with good selectivity, is the use of nanoparticles as heterogeneous catalysts. The potential of nanoparticles to catalyse and modify chemical processes, thereby influencing both the nature of the products and their distribution is seen as highly promising. In this publication, we aim to give an overview of the use of a range of nano-catalysts and nano-enzymatic supports for greener biorefinery processing. Finally, future prospects of greener routes to nanoparticle production and their integration into biomass are discussed.

From waste to wealth using green chemistry

The availability of chemically rich food supply chain waste (FSCW) gives it considerable potential as a resource for the manufacture of chemicals including materials and fuels. By applying clean chemical technologies to the extraction and conversion of molecules from FSCW, we can aim to produce genuinely green and sustainable products to help meet the legislative and consumer-oriented demands of a sustainable society. Low-temperature microwave (MW) processing is a particularly powerful technology to achieve this aim and is shown to be effective for several different high-volume, geographically diverse biomass types.

A Sustainable Freeze-Drying Route to Porous Polysaccharides with Tailored Hierarchical Meso- and Macroporosity

Bio-derived polysaccharide aerogels are of interest for a broad range of applications. To date, these aerogels have been obtained through the time- and solvent-intensive procedure of hydrogel fomation, solvent exchange, and scCO2 drying, which offers little control over meso/macropore distribution. A simpler and more versatile route is developed, using freeze drying to produce highly mesoporous polysaccharide aerogels with various degrees of macroporosity. The hierarchical pore distribution is controlled by addition of different quantities of t-butanol (TBA) to hydrogels before drying. Through a systematic study an interesting relationship between the mesoporosity and t-butanol/water phase diagram is found, linking mesoporosity maxima with eutectic points for all polysaccharides studied (pectin, starch, and alginic acid). Moreover, direct gelation of polysaccharides in aqueous TBA offers additional time savings and the potential for solvent reuse. This finding is a doorway to more accessible polysaccharide aerogels for research and industrial scale production, due to the widespread accessibility of the freeze drying technology and the simplicity of the method.

Low temperature microwave-assisted vs conventional pyrolysis of various biomass feedstocks

Abstract A comparison between conventional pyrolysis and a novel developed low-temperature microwave-assisted pyrolysis methodology has been performed for the valorisation of a range of biomass feedstocks including waste residues. Microwave pyrolysis was found to efficiently deliver comparable evolution of bio-gases in the system as compared with conventional pyrolysis at significantly reduced temperatures (120–180°C vs 250–400°C). The gas obtained from microwave-assisted pyrolysis was found to contain CO 2 , CH 4 and CO as major components as well as other related chemicals (e.g. acids, aldehydes, alkanes) which were obtained in different proportions depending on the selected feedstock.

Low-temperature microwave-assisted pyrolysis of waste office paper and the application of bio-oil as an Al adhesive

The conversion of waste office paper (printed or photocopied) to bio-oil via low temperature (<200 °C) microwave-assisted pyrolysis, and its utilisation as an adhesive for aluminium–aluminium bonding are reported. The yields for the organic and aqueous phase bio-oil are 19% and 23%, respectively. The pyrolysis products were characterized by ICP-MS, ATR-IR, GC-MS and NMR to reveal broad categories of compounds indicative of sugars (carbohydrates), aromatics and carbonyl-containing moieties. Application of the organic phase bio-oil (70 mg) to Al plates (50 mm × 50 mm) followed by curing at different temperatures and time periods revealed that a maximum tensile strength of approximately 2300 N could be attained at 160 °C for 8 h cure. Also, at a fixed temperature, the tensile strength increased with increasing curing time. To gain an in-depth understanding of the adhesive properties of bio-oil, a liquid–liquid fractionation of the organic phase bio-oil was conducted. The ‘acidic’ fraction showed far better adhesion properties than the ‘neutral’ fraction with no bonding achieved for the aqueous fraction. A combination of the ‘acidic’ and ‘neutral’ fraction gave better adhesion, thus suggesting a possible synergistic or co-operative effect.

Molecular‐Level Understanding of the Carbonisation of Polysaccharides

Understanding of both the textural and functionality changes occurring during (mesoporous) polysaccharide carbonisation at the molecular level provides a deeper insight into the whole spectrum of material properties, from chemical activity to pore shape and surface energy, which is crucial for the successful application of carbonaceous materials in adsorption, catalysis and chromatography. Obtained information will help to identify the most appropriate applications of the carbonaceous material generated during torrefaction and different types of pyrolysis processes and therefore will be important for the development of cost- and energy-efficient zero-waste biorefineries. The presented approach is informative and semi-quantitative with the potential to be extended to the formation of other biomass-derived carbonaceous materials.

Identification of high performance solvents for the sustainable processing of graphene

Nanomaterials have many advanced applications, from bio-medicine to flexible electronics to energy storage, and the broad interest in graphene-based materials and devices means that high annual tonnages will be required to meet this demand. However, manufacturing at the required scale remains unfeasible until economic and environmental obstacles are resolved. Liquid exfoliation of graphite is the preferred scalable method to prepare large quantities of good quality graphene, but only low concentrations are achieved and the solvents habitually employed are toxic. Furthermore, good dispersions of nanomaterials in organic solvents are crucial for the synthesis of many types of nanocomposites. To address the performance and safety issues of solvent use, a bespoke approach to solvent selection was developed and the renewable solvent Cyrene was identified as having excellent properties. Graphene dispersions in Cyrene were found to be an order of magnitude more concentrated than those achieved in N-methylpyrrolidinone (NMP). Key attributes to this success are optimum solvent polarity, and importantly a high viscosity. We report the role of viscosity as crucial for the creation of larger and less defective graphene flakes. These findings can equally be applied to the dispersion of other layered bi-dimensional materials, where alternative solvent options could be used as drop-in replacements for established processes without disruption or the need to use specialized equipment. Thus, the discovery of a benign yet high performance graphene processing solvent enhances the efficiency, sustainability and commercial potential of this ever-growing field, particularly in the area of bulk material processing for large volume applications.