Conversion of biomass materials

The conversion of biomass materials to high octane gasoline has been actively pursued for many years. Historically, methanol was made in very low yields by the destructive distillation of hardwoods. More recently, the manufacture of methanol has been by the reaction of synthesis gas over catalysts at high pressures. In theory, any carbon source can be used for this catalytic generation of methanol, but in practice, biomass has not been advantageous relative to coal or natural gas. Other approaches to making liquid fuel from biomass have involved the fermentation of biomass to ethanol in a rather slow process. The conversion of biomass to alcohols is technically feasible, but the utilization of the alcohols as transportation fuels will require modifications to the... 

At Brookhaven National Laboratory in the 1980s, a two-step process was described for the coproduction of hydrogen and carbon, with methane being the intermediate see Steinberg.107108 In the first step, carbonaceous material is hydrogasified to methane with a subsequent thermal decomposition of the methane to hydrogen and carbon. In the process, water is also formed from the oxygen present in the fuel. A typical overall conversion of biomass, as reported by Milne et al.,5 would be... 

Steinberg, M., The conversion of carbonaceous materials to clean carbon and co-product gaseous fuel. 5th European Conference on Biomass for Energy and Industry, Lisbon, 1989. 

Development of novel synthetic routes for efficient conversion of biomass derived raw materials with high performance, stability and selectivity, by integrating bio-, chemical and catalytic processes. Synthetic pathways in which the complexity needed in a target molecule is already preformed in the biomolecule are especially favorable. 

Chemical Synthesis The traditional tools of chemical synthesis in use today are organic and inorganic synthesis and catalysis. Synthesis is the efficient conversion of raw materials such as minerals, petroleum, natural gases, coal, and biomass into more useful molecules and products catalysis is the process by which chemical reactions are either accelerated or slowed by the addition of a substance that is not changed in the chemical reaction. Catalysis-based chemical syntheses account for 60% of today s chemical products and 90% of current chemical processes (Collins, 2001). 

Ethanol is the key reactant in Eq. (1), and also in Eq. (2) because it is readily converted to acetaldehyde. The process based on Eq. 1 was developed in Russia and the process based on Eq. 2 was developed in the United States. The yield of butadiene for the Russian process is about 30-35%. It is about 70% if mixtures of ethanol and acetaldehyde are employed as in the U.S. process. Equation (3) represents a process that involves 2,3-butylene glycol, a product from the microbial conversion of biomass. The process is carried out in two sequential steps via the glycol diacetate in overall yields to butadiene of about 80%. The process of Eq. (4) starts with a biomass derivative, the cyclic ether tetrahydrofuran, and can be carried out at high yields. When this process was first operated on a large scale in Germany, acetylene and formaldehyde were the raw materials for the synthesis of intermediate tetrahydrofuran. It is manufactured today from biomass feedstocks by thermochemical conversion, as will be discussed later. 

The other prerequisite is the fact that society not only expects competitive, but clean systems and products as well. One has to look at the whole chain of production and conversion of biomass to get a clear picture of the environmental consequences. For the feeding material there is a strong preference for woody or grassy materials [7]. The emission of the power plant has to be low and the strict Dutch rules for waste incineration installations are taken as a point of departure [5]. The whole-integrated system has the further advantage that it produces renewable products for which there is a market today electricity, heat, and FT-liquids. Furthermore, the liquid fuels form an attractive energy carrier and storage medium. 

Another potential feedstock for ethanol production is the lignocellulosic biomass . Lignocellulosic biomass is the most plentiful of all naturally occurring organic compounds. It includes such materials as wood, herbaceous crops, agricultural and forestry residues, waste paper and paper products, pulp and paper mill waste, and municipal sohd waste. Unlike starchy materials, lignocellulosic biomass is structurally complex. The conversion of this material into ethanol has been the subject of intense study over the last 20 years. 

Needless to say, solid acid and base catalysts play a key role in the transformation of biomass-derived materials to value-added compounds such as carbonyl compounds [21-33]. For example, lactic acid could be obtained from cellulose using tungstated alumina as a Lewis add catalyst [137], and from glucose using HT as a solid base catalyst [138]. In this parL selective conversions of biomass-sourced materials using solid acid and base catalysts are surveyed alongside mechanistic considerations. 

Multifunctional Zeolites Efficient, multifunctional zeolite-based catalysts allowing one-step complex reactions are of great interest in the field of fine chemicals and organic industrial synthesis [58]. Recendy, catalysts based on zeolites are relevant in emerging areas of interest such as the catalytic conversion of biomass to fuels and chemicals (see Section 8.2.1.3 for illustrative examples). This field needs to develop specific multifunctional catalysts having the correct polarity (adsorption properties) and reactant accessibility (porosity), which are efficient in water or biphasic operation with reactants and products of different polarities and sizes. Hence, great opportunities for zeolites and related materials are offered in this new field [59-61]. 

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