Biomass, in particular biomass of plant origin, is recognized as an abundant potential source of fuels and specialty chemicals. See, for example, “Energy production from biomass,” by P. McKendry—Bioresource Technology 83 (2002) 37-46 and “Coordinated development of leading biomass pretreatment technologies” by Wyman et al., Bioresource Technology 96 (2005) 1959-1966. Refined biomass feedstock, such as vegetable oils, starches, and sugars, can be substantially converted to liquid fuels including biodiesel, such as methyl or ethyl esters of fatty acids and ethanol. However, using refined biomass feedstock for fuels and specialty chemicals diverts food sources from animal and human consumption, raising financial and ethical issues.
Alternatively, inedible biomass can be used to produce liquid fuels and specialty chemicals. Examples of inedible biomass include agricultural waste such as bagasse, straw, corn stover, corn husks, and the like, and specifically grown energy crops such as switch grass and saw grass. Other examples include trees, forestry waste, such as wood chips and saw dust from logging operations, and waste from paper or paper mills. In addition, aquacultural sources of biomass, such as algae, are also potential feedstocks for producing fuels and chemicals. Inedible biomass generally includes three main components: lignin, amorphous hemi-cellulose, and crystalline cellulose. Certain components such as lignin reduces the chemical and physical accessibility of the biomass, which in turn reduces the susceptibility to chemical or enzymatic conversion.
Attempts to produce fuels and specialty chemicals from biomass often result in low value products such as unsaturated and oxygen containing hydrocarbons. Although such low value products can be upgraded into higher value products including conventional gasoline and jet fuel, such upgrading requires specialized and costly conversion processes and refineries, which are distinct from and incompatible with conventional petroleum-based conversion processes and refineries. Thus, the wide-spread use and conversion of biomass to produce fuels and specialty chemicals face many challenges for various reasons. First, large-scale production facilities are not widely available and are expensive to build. Furthermore, existing processes require extreme conditions such as high temperature and pressure, expensive process gasses such as hydrogen, as well as expensive catalysts, all of which increase capital and operating costs. In addition, existing processes not only suffer low conversion efficiency caused by, for example, incomplete conversion or inability to convert lingo-cellulosic and hemi-cellulosic material, but also suffer poor product selectivity.
To date, a need remains for novel and improved processes and catalysts for the conversion of solid biomass materials to produce fuels and specialty chemicals. More specifically, a need exists for improved catalysts that can increase biomass conversion efficiency and increase the yield of desired conversion products.