Building blocks chemical conversion

Beyond this careful selection of platform chemicals, the production of a number of other polymer building blocks, chemical intermediates, and end products from carbohydrates has been reported. Due to the unique oxygen-rich composition of carbohydrates, their conversion into renewable chemicals that preserve the functional groups is an advantage over the current petroleum and natural gas conversion routes. Biomass conversion with high atom efficiency is a key aspect of the competitive synthesis of chemicals and chemical-based products. 

The implementation of compatible catalytic processes in the actual chemical and petrochemical infrastructure requires the conversion of biomass feedstocks into building block chemicals (also known as platform... 

The US Department of Energy has recently issued a report (2) outlining the top 12 building block chemicals that can be produced from sugars via biological or chemical conversions. They are shown in Table III. Levulinic acid is one of the key building blocks and has been the focus of some of our research at DuPont. This paper will outline some of our research to illustrate the potential for new chemical transformations of these biomass building blocks. 

The most conspicuous use of iron in biological systems is in our blood, where the erythrocytes are filled with the oxygen-binding protein hemoglobin. The red color of blood is due to the iron atom bound to the heme group in hemoglobin. Similar heme-bound iron atoms are present in a number of proteins involved in electron-transfer reactions, notably cytochromes. A chemically more sophisticated use of iron is found in an enzyme, ribo nucleotide reductase, that catalyzes the conversion of ribonucleotides to deoxyribonucleotides, an important step in the synthesis of the building blocks of DNA. 

While alkane metathesis is noteworthy, it affords lower homologues and especially methane, which cannot be used easily as a building block for basic chemicals. The reverse reaction, however, which would incorporate methane, would be much more valuable. Nonetheless, the free energy of this reaction is positive, and it is 8.2 kj/mol at 150 °C, which corresponds to an equihbrium conversion of 13%. On the other hand, thermodynamic calculation predicts that the conversion can be increased to 98% for a methane/propane ratio of 1250. The temperature and the contact time are also important parameters (kinetic), and optimal experimental conditions for a reaction carried in a continuous flow tubiflar reactor are as follows 300 mg of [(= SiO)2Ta - H], 1250/1 methane/propane mixture. Flow =1.5 mL/min, P = 50 bars and T = 250 °C [105]. After 1000 min, the steady state is reached, and 1.88 moles of ethane are produced per mole of propane consmned, which corresponds to a selectivity of 96% selectivity in the cross-metathesis reaction (Fig. 4). The overall reaction provides a route to the direct transformation of methane into more valuable hydrocarbon materials. 

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). 

Recently a very comprehensive report on the pathways from sugars to chemicals and fuels has been issued by the US department of energy [88]. The report identifies the twelve most promising building blocks (Table 6.5) that can be produced from sugars via biological and chemical conversions. These building blocks can be subsequently converted into several chemicals and fuels. 

The main framework is made up of five key modules for chemical library editing, enumeration, conversion, visualization, and analysis. The operations of these functionalities are accomplished by the various applications at the resource layer. For the purpose of illustration, the compound calothrixin B, a secondary metabolite isolated from the Calothrix cyanobacteria (11-13), is used as the scaffold molecule with the variable functional groups Rw] attached (Fig. 18.1). The calothrixins are redox-active natural products which display potent antimalarial and anticancer properties and thus there is interest in probing the physical as well as biological profiles of their derivatives (14). In this exercise, six functional groups have been selected as the building blocks (Table 18.1). 

Another process is the conversion of toluene into caprolactam that provides an alternative basic building block for this chemical other than benzene. Toluene is oxidized to benzoic acid, and hydrogenation to cyclohexanecar-boxylic acid is followed by treatment with nitrosylsulfuric acid to form cyclohexanone oxime followed by rearrangement to caprolactam. 

The potential for fermentation technologies to produce bulk quantities of chemicals from sugars has stimulated much interest. The EU BREW project (BREW, 2006) identified a significant number of potential chemical building blocks of current commercial interest, which are, or could, be economically produced from fermentation and/or enzymic conversion of glucose, sucrose or starch (Table 2.5). 

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