3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review

Background Lignin, nature’s dominant aromatic polymer, is found in most terrestrial plants in the approximate range of 15 to 40% dry weight and provides structural integrity. Traditionally, most large-scale industrial processes that use plant polysaccharides have burned lignin to generate the power needed to productively transform biomass. The advent of biorefineries that convert cellulosic biomass into liquid transportation fuels will generate substantially more lignin than necessary to power the operation, and therefore efforts are underway to transform it to value-added products. Production of biofuels from cellulosic biomass requires separation of large quantities of the aromatic polymer lignin. In planta genetic engineering, enhanced extraction methods, and a deeper understanding of the structure of lignin are yielding promising opportunities for efficient conversion of this renewable resource to carbon fibers, polymers, commodity chemicals, and fuels. [Credit: Oak Ridge National Laboratory, U.S. Department of Energy] Advances Bioengineering to modify lignin structure and/or incorporate atypical components has shown promise toward facilitating recovery and chemical transformation of lignin under biorefinery conditions. The flexibility in lignin monomer composition has proven useful for enhancing extraction efficiency. Both the mining of genetic variants in native populations of bioenergy crops and direct genetic manipulation of biosynthesis pathways have produced lignin feedstocks with unique properties for coproduct development. Advances in analytical chemistry and computational modeling detail the structure of the modified lignin and direct bioengineering strategies for targeted properties. Refinement of biomass pretreatment technologies has further facilitated lignin recovery and enables catalytic modifications for desired chemical and physical properties. Outlook Potential high-value products from isolated lignin include low-cost carbon fiber, engineering plastics and thermoplastic elastomers, polymeric foams and membranes, and a variety of fuels and chemicals all currently sourced from petroleum. These lignin coproducts must be low cost and perform as well as petroleum-derived counterparts. Each product stream has its own distinct challenges. Development of renewable lignin-based polymers requires improved processing technologies coupled to tailored bioenergy crops incorporating lignin with the desired chemical and physical properties. For fuels and chemicals, multiple strategies have emerged for lignin depolymerization and upgrading, including thermochemical treatments and homogeneous and heterogeneous catalysis. The multifunctional nature of lignin has historically yielded multiple product streams, which require extensive separation and purification procedures, but engineering plant feedstocks for greater structural homogeneity and tailored functionality reduces this challenge.

https://lifelong.unt.edu/sites/default/files/EmeritusCollege/Spring2015/Handouts/Lignin%20co-products.pdf

Lignin valorization: improving lignin processing in the biorefinery.

Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.

/pdf/pretreatment-of-lignocellulosic-wastes-to-improve-ethanol-zbwx58h962.pdf

Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review.

Progress and recent trends in biodiesel fuels

Production of ethanol by bioconversion of lignocellulosic biomass has attracted much interest in recent years. However, the pretreatment process for increasing the enzymatic digestibility of cellulose has become a key step in commercialized production of cellulosic ethanol. During the last decades, many pretreatment processes have been developed for decreasing the biomass recalcitrance, but only a few of them seem to be promising. From the point of view for integrated utilization of lignocellulosic biomass, organosolv pretreatment provides a pathway for biorefining of biomass. This review presents the progress of organosolv pretreatment of lignocellulosic biomass in recent decades, especially on alcohol, organic acid, organic peracid and acetone pretreatments, and corresponding action mechanisms. Evaluation and prospect of organosolv pretreatment were performed. Finally, some recommendations for future investigation of this pretreatment method were given.

Organosolv pretreatment of lignocellulosic biomass for enzymatic hydrolysis

Biodiesel has become more attractive recently because of its environmental benefits, and the fact that it is made from renewable resources. Generally speaking, biodiesel is prepared through transesterification of vegetable oils or animal fats with short chain alcohols. However, the lack of oil feedstocks limits the large-scale development of biodiesel to some extent. Recently, much attention has been paid to the development of microbial, oils and it has been found that many microorganisms, such as algae, yeast, bacteria, and fungi, have the ability to accumulate oils under some special cultivation conditions. Compared to other plant oils, microbial oils have many advantages, such as short life cycle, less labor required, less affection by venue, season and climate, and easier to scale up. With the rapid expansion of biodiesel, microbial oils might become one of potential oil feedstocks for biodiesel production in the future, though there are many works associated with microorganisms producing oils need to be carried out further. This review is covering the related research about different oleaginous microorganisms producing oils, and the prospects of such microbial oils used for biodiesel production are also discussed.

/pdf/perspectives-of-microbial-oils-for-biodiesel-production-5216vxlk8h.pdf

Perspectives of microbial oils for biodiesel production.

Lignocellulosic biomass is recalcitrant to biodegradation due to the rigid and compact structure of plant cell wall The recalcitrance of biomass is mainly constructed by its chemical compositions that build a spatial network as a protective bulwark Generally, the factors affecting the accessibility of biomass cellulose can be divided into direct and indirect factors The direct factors refer to the accessible surface area, and the indirect factors include biomass structure-relevant factors (pore size and volume, particle size, and specific surface area), chemical compositions (lignin, hemicelluloses, and acetyl group), and cellulose structure-relevant factors (cellulose crystallinity and degree of polymerization) Pre-treatment is actually the process to alter indirect factors and improve direct factors thus enhancing the accessibility of cellulose In this review, we summarize the effects of chemical compositions and physical structures on the enzymatic digestibility of lignocellulosic biomass We suggest that future work should be focused on but not limited to the molecular mechanisms of biomass recalcitrance by investigating the microscale and nanoscale features as well as hydrogen bonds network of lignocellulosic biomass © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd

Biomass recalcitrance. Part I: the chemical compositions and physical structures affecting the enzymatic hydrolysis of lignocellulose

Methyl acetate, a novel acyl acceptor for biodiesel production has been developed, and a comparative study on Novozym 435-catalyzed transesterification of soybean oil for biodiesel production with different acyl acceptors was conducted and reported in this paper. Methanol has a serious negative effect on enzymatic activity. A molar ratio of methanol to oil of above 1:1 leads to serious inactivation of the enzyme. However, when methyl acetate was used as the acyl acceptor, a yield of 92% of methyl ester could be obtained with a molar ratio of methyl acetate to oil of 12:1, and methyl acetate showed no negative effect on enzymatic activity. Additionally, with crude soybean oil as the oil source and methanol as acyl acceptor, a much lower methyl ester yield was obtained than that with refined soybean oil, while with methyl acetate as acyl acceptor, an equally high yield of methyl ester (92%) was achieved for both soybean oils. Lipase loses its activity very rapidly during repeated experiments with methanol as the acyl acceptor, while there is almost no detected loss in lipase activity, even after being continuously used for 100 batches, when methyl acetate was used for biodiesel production. Moreover, the by-product triacetylglycerol is an important chemical with a higher value than glycerol, and this novel acyl acceptor seems very promising for lipase-catalyzed large-scale production of biodiesel.

Dehua Liu

Papers

Organosolv pretreatment of lignocellulosic biomass for enzymatic hydrolysis

Perspectives of microbial oils for biodiesel production.

Biomass recalcitrance. Part I: the chemical compositions and physical structures affecting the enzymatic hydrolysis of lignocellulose

Comparative study on lipase-catalyzed transformation of soybean oil for biodiesel production with different acyl acceptors

Production of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF): recent progress focusing on the chemical-catalytic routes