Utilization of Feedstocks

Before considering alternative sources of feedstocks, it is useful to consider how those feedstocks can be used in the least polluting, most sustainable way possible. Feedstocks are modified by chemical processes to produce new chemical materials with commercial uses. The ideal feedstock is renewable and poses no hazards. And it can be converted to the desired product using a few steps with 100% yield and 100% atom economy. This should be done with minimum quantities of reagent using only safe media in which the reaction occurs. 

FIGURE 16.2 Illustration of three major categories of reaction processes by which feedstocks are acted upon by reagents to produce desired products. 

---

Priorities in today s industry emphasize more efficient utilization of feedstocks and energy. Most effort is placed on improving existing processes rather than developing new ones. With this in mind and with an awareness of the direction of current research, it is the author s opinion that the relative order of importance is selectivity > deactivation > activity. 

The amino acid production industry will remain as a fast growing business enterprise until a cheaper and energy efficient process is commercialized. Microbial amino acid production will be exploited to the most possible extend of maximal production capacity and process economics by new innovations in strain improvement, metabolic engineering, and systems biology. Microbial amino acid production holds a promising position in the future of white biotechnology and studies on utilization of feedstock for... 

Adiponitrile is made commercially by several different processes utilizing different feedstocks. The original process, utilizing adipic acid (qv) as a feedstock, was first commercialized by DuPont in the late 1930s and was the basis for a number of adiponitrile plants. However, the adipic acid process was abandoned by DuPont in favor of two processes based on butadiene (qv). During the 1960s, Monsanto and Asahi developed routes to adiponitrile by the electrodimerization of acrylonitrile (qv). 

The need to meet environmental regulations can affect processing costs. Undesirable air emissions may have to be eliminated and Hquid effluents and soHd residues treated and disposed of by incineration or/and landfilling. It is possible for biomass conversion processes that utilize waste feedstocks to combine waste disposal and treatment with energy and/or biofuel production so that credits can be taken for negative feedstock costs and tipping or receiving fees. 

Alcohol Substitution. In the early period of normal thiol production, the normal alcohols were utilized as feedstocks. The use of a strong acid catalyst results in the formation of a significant amount of secondary thiol, along with other isomers resulting from skeletal isomerization of the starting material. This process has largely been replaced by uv-initiation because of the higher relative cost of alcohol vs alkene feedstock. 

A typical reactor operates at 600—900°C with no catalyst and a residence time of 10—12 s. It produces a 92—93% yield of carbon tetrachloride and tetrachloroethylene, based on the chlorine input. The principal steps in the process include (/) chlorination of the hydrocarbon (2) quenching of reactor effluents 3) separation of hydrogen chloride and chlorine (4) recycling of chlorine to the reactor and (i) distillation to separate reaction products from the hydrogen chloride by-product. Advantages of this process include the use of cheap raw materials, flexibiUty of the ratios of carbon tetrachloride and tetrachloroethylene produced, and utilization of waste chlorinated residues that are used as a feedstock to the reactor. The hydrogen chloride by-product can be recycled to an oxychlorination unit (30) or sold as anhydrous or aqueous hydrogen chloride. 

Table 1 shows the carbon chain distributions for several typical commercial alkylates. The carbon chain distributions for linear alkylbenzene (LAB) samples A, C, and E are determined by the distillation cut of n-paraffins used to make the LAB. LAB samples B and D represent blended alkylates made by mixing samples such as A and E in different ratios. This provides to the customer LAB products with a wide variety of molecular weights and improves the utilization of the fl-paraffin feedstocks. 

Direct conversion of methane to ethane and ethylene (C2 hydrocarbons) has a large implication towards the utilization of natural gas in the gas-based petrochemical and liquid fuels industries [ 1 ]. CO2 OCM process provides an alternative route to produce useful chemicals and materials where the process utilizes CO2 as the feedstock in an environmentally-benefiting chemical process. Carbon dioxide rather than oxygen seems to be an alternative oxidant as methyl radicals are induced in the presence of oxygen. Basicity, reducibility, and ability of catalyst to form oxygen vacancies are some of the physico-chemical criteria that are essential in designing a suitable catalyst for the CO2 OCM process [2]. The synergism between catalyst reducibility and basicity was reported to play an important role in the activation of the carbon dioxide and methane reaction [2]. 

Apart from a few reports" on solid acid catalyzed esterification of model compounds, to our knowledge utilization of solid catalysts for biodiesel production from low quality real feedstocks have been explored only recently. 12-Tungstophosphoric acid (TPA) impregnated on hydrous zirconia was evaluated as a solid acid catalyst for biodiesel production from canola oil containing up to 20 wt % free fatty acids and was found to give ester yield of 90% at 200°C. Propylsulfonic acid-functionalized mesoporous silica catalyst for esterification of FFA in flotation beef tallow showed a superior initial catalytic activity (90% yield) relative to a... 

Dextran was chosen to study for the following reasons. First, it is water soluble allowing three dimensional modification employing aqueous solution and classical interfacial condensation routes. Second, it is readily available in industrial quantities. Third, it is available in a range of molecular weight allowing product modification to be studied as a function of dextran chain size. Fourth, it is generally considered to be an under-utilized natural feedstock. 

Sales limited by market This situation is susceptible to optimization only if improvements in efficiency or productivity can be obtained hence, the economic incentive for implementation in this case may be less than in the first example because no additional products are made. Reductions in unit manufacturing costs (via optimizing usage of utilities and feedstocks) are generally the main targets. 

MARCHAIM, U., and CRIDEN, J. Research and development in the utilization of agricultural wastes in Israel for energy, feedstock fodder, and industrial products. In D.L.Wise (Ed), Fuel Gas Production from Biomass . Vol. 1, CRC Press Inc. Boca Raton, Florida, pp. 95-120, 1981. 

The current utilization of carbohydrates as a feedstock for the chemical industry—be it for bulk, commodity, intermediate, fine, or high-value-added speciality chemicals—is modest when considering their ready availability at low cost and the huge as yet unexploited potential. The examples currently realized on an industrial scale are outlined briefly. 

The monetization of remote natural gas has been a key economic driver for catalysis research over the past 20 years. Significant reserves of natural gas exist in remote locations, distant from available gas pipehnes, which cannot be readily brought to market. The conversion of these resources to higher-valued, transportable products, such as methanol or polyolefins can allow the economical utilization of these stranded assets. Other low-valued natural gas streams, such as associated gas from oil production, could also provide feedstocks to such a technology. The conversion of remote gas, typically valued at US 0.50-1.50 per MMBTU, into polyolefins, valued at more than US 1000/t, via methanol has sparked the development of several MTO technologies. 

Many renewable feedstocks are currently summarily destroyed (through leaving them to rot or burning) or utilized in a noneconomical manner. Thus, leaves are ritualistically burned each fall. A number of these seemingly useless natural materials have already been utilized as feedstock sources for industrial products with more becoming available. 

Thus, the overall acetaldehyde selectivity approaches 98%. The utility of methyl acetate as an alternative feedstock has been previously illustrated by the reported carbonylation to acetic anhydride ( ) and homologation ( ) to ethyl acetate via reaction with synthesis gas. 

Nickel and Other Base Metal Catalysts. Supported Ni is widely utilized as a catalyst for the industrial SR of hydrocarbons. The type of feedstocks and reaction conditions used for SR determine the choice of support, promoter, and loading of Ni. Typically, 15-25% nickel oxide loading is used in commercial SR catalysts. These supports must have high crush strength and stability so they can sustain severe reaction conditions. 

---