Biorefinery chemicals

Brehmer, B., Boom, R.M. et al. (2009) Maximum fossil fuel feedstock replacement potential of petrochemicals via biorefineries. Chemical Engineering Research and Design, 87(9), 1103-1119. 

Wood chips can also be utilized as such to produce bioethanol. The cellulose and hemicellulose material is hydrolyzed in the presence of acids (H2SO4, HCl, or HCOOH) or enzymes to yield glucose and other monosaccharides [16]. Lignin is separated by filtration as a solid residue and the monosaccharides are fermented to ethanol, which, in turn, is separated from water and catalyst by distillation. Ethanol can be used not only as energy source but also as a platform component to make various chemicals, such as ethene and polyethene. Today green acetaldehyde and acetic acid from wood-derived bioethanol is manufactured by SEKAB Ab, at the Ornskoldsvik Biorefinery of the Future industrial park. 

An alternative possibility is that of the biorefinery. In this concept a few key chemicals would be isolated from a small number of process steps. Whilst there are many possibilities for this, in one example the raw material, say com, could be cmshed to release oil (the first key product). The resulting mass could then be fermented to give several key platform chemicals such as ethanol, lactic acid and acetic acid. This attractive concept would be more viable if all the cellulose and lignin components could be efficiently used in the fermentation process. 

Alternatively, an entirely new downstream process and product chain, using renewable raw materials, can be conceived (the biorefinery ). The chemistry will be more focused on that of oxohydrocarbons (particularly carbohydrates) rather than hydrocarbons. Understanding the materials chemistry of biomass and related products would need to be enhanced. However, work has already been undertaken to identify the top sugar-derived intermediates (Figure 1.9) on which down-stream chemical processing might be derived. 

To achieve sustainable production through biorefineries, engineers can look to specific chemical processes that draw on green technological alternatives. Whereas the principles... 

Biomass is a renewable resource from which various useful chemicals and fuels can be produced. Glycerol, obtained as a co-product of the transesterification of vegetable oils to produce biodiesel, is a potential building block to be processed in biorefineries (1,2). Attention has been recently paid to the conversion of glycerol to chemicals, such as propanediols (3, 4), acrolein (5, 6), or glyceric acid (7, 8). 

Combining fuel and power production, possibly extended with (bulk) chemical production by advanced integrated biorefinery process concepts... 

A biorefinery scheme to produce chemicals from non-food biomass is given in Fig. 1.16. 

This chapter surveys different process options to convert terpenes, plant oils, carbohydrates and lignocellulosic materials into valuable chemicals and polymers. Three different strategies of conversion processes integrated in a biorefinery scheme are proposed from biomass to bioproducts via degraded molecules , from platform molecules to bioproducts , and from biomass to bioproducts via new synthesis routes . Selected examples representative of the three options are given. Attention is focused on conversions based on one-pot reactions involving one or several catalytic steps that could be used to replace conventional synthetic routes developed for hydrocarbons. 

The biorefinery scheme was developed initially for carbohydrate-containing feedstocks. Large biorefineries are currently operating in the USA (e.g., Cargill at Blair, Nebraska) and in Europe (e.g., Roquette Frs. at Lestrem, France). The concept can be extended to produce chemicals from other renewable feedstocks. An integrated production of oleochemicals and biofuels can be achieved in biorefineries using vegetables oils as main feedstock to produce versatile platform mole-... 

Within the biorefinery scheme we have identified three process options to produce chemicals by catalytic routes ... 

A biorefinery maximizes the value derived from the complex biomass feedstock by (a) optimal use and valorization of feedstock, (b) optimization and integration of processes for better efficiency, and (c) optimization of inputs (water, energy, etc.) and waste recycling/treatment. Integrated production of bioproducts, especially for bulk chemicals, biofuels, biolubricants and polymers, can improve their competitiveness and eco-efficiency. However, although a few examples of biorefineries already exist (Chapters 3 and 6), many improvements are still needed to enhance the process [5] ... 

Development of new and/or improved routes for chemical building blocks for polymers, lubricants and fine chemicals, including through the integration of the biorefinery concept and products into the existing chemical production chain. 

To convert these feedstocks into useful chemicals, mainly fermentation, chemical modification or thermochemical methods were applied. However, these processes were later abandoned in favor of the more economic and efficient processes based on fossil resources, in particular oil. Easier transport and more stable chemical composition (biomass feedstocks are highly diverse, depending on the source) are two relevant additional factors in favor of fossil fuels. Therefore, although the concept of biorefinery is attractive, there are several barriers to economically feasible. 

However, most of these routes are still economically unattractive and the possibility of creating an equivalent petrochemistry based on biomass, which depends on raising the conversion efficiency and establishing cascades in which the residues of one product serve as inputs for another, still suffers from the relatively unattractive products derived from hemicellulose and lignin. Therefore, to bring back biomass into the chemical business , the utilization of biomass must be enhanced by integrating it into biorefinery (Fig. 2). 

The valorization of by-products in biomass conversion is a key factor for introducing a biomass based energy and chemistry. There is the need to develop new (catalytic) solutions for the utilization of plant and biomass fractions that are residual after the production of bioethanol and other biofuels or production chains. Valorization, retreatment or disposal of co-products and wastes from a biorefinery is also an important consideration in the overall bioreftnery system, because, for example, the production of waste water will be much larger than in oil-based refineries. A typical oil-based refinery treats about 25 000 t d-1 and produces about 15 000 t d 1 of waste water. The relative amount of waste water may increase by a factor 10 or more, depending on the type of feed and production, in a biorefinery. Evidently, new solutions are needed, including improved catalytic methods to eliminate some of the toxic chemicals present in the waste water (e.g., phenols). 

Biorefineries New catalytic pretreatment of plant materials Valorization, pretreatment or disposal of co-products and wastes from biorefinery by catalytic treatments New and/or improved catalytic processes for chemicals production through the integration of the biorefinery concept and products into the existing chemical production chain New advanced catalytic solutions to reduce waste emissions (solid, air and, especially, water) New catalysts to selectively de-oxygenate products from biomass transformation Catalysts to selectively convert chemicals in complex multicomponent feedstocks New biomimetic catalysts able to operate under mild conditions Small catalytic pyrolysis process to produce stabilized oil for further processing in larger plants... 

It is thought that this cascade of products could be manufactured in a biorefinery by integrating all the unit operations needed to convert biomass into chemicals. A lot more research is needed, however, to develop the hydrothermolysis process and high-efficiency/low-cost fermentation and acid treatments. An efficient exploitation of lignin (the only naffiral source of aromatic rings) has also to be developed. 

A biorefinery is a facility that integrates biomass conversion processes and eqtrip-ment to produce fuels, power, and value-added chemicals from biomass. Biorefinery is the co-production of a spectram of bio-based products and energy from biomass. The biorefinery concept is analogous to today s crude oil refinery. Biorefinery is a relatively new term referring to the conversion of biomass feedstock into a host of valuable chemicals and energy with minimal waste and emissions. 

Biorefinery includes fractionation for separation of primary refinery products. The fractionation refers to the conversion of wood into its constituent components (cellulose, hemicelluloses and lignin). Processes include steam explosion, aqueous separation and hot water systems. Commercial products of biomass fractionation include levulinic acid, xylitol and alcohols. Figure 3.3 shows the fractionation of wood and chemicals from wood. 

There are four main biorefineries biosyngas-based refinery, pyrolysis-based refinery, hydrothermal upgrading-based refinery, and fermentation-based refinery. Biosyngas is a mrrltifimctional intermediate for the production of materials, chemicals, transportation fuels, power and/or heat from biomass. Figrrre 3.4 shows the gasification-based thermochemical biorefinery. 

The concept biorefinery is discussed in the US National Research Council Report Biobased Industrial Products [4] and by Lynd et al. [7] in much detail. The basic idea is the processing of multiple renewable resources and the production of multiple products in a production complex. Another characteristic of biorefinery is the integration of thermal, chemical, biological and/or cataly-tical processes for an efficient and optimal processing and utilization of the raw materials. Technological, ecological and economic analysis and system design should be implemented to ensure an overall optimization of raw material conversion and product formation in a similar way as for oil refineries. 

It is beheved that such a diversity of substrates and products of biorefinery will greatly improve the economical competitiveness of producing chemicals from biotechnology. 

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