Synthesis plant waxes

The structure and composition of )3-diketones and hydroxy-/8-diketones of plant waxes strongly suggest that the latter are derived from the former. In support of this conclusion it was shown that wax of barley mutants lacking hydroxy-j8-diketones had a compensatory increase in /3-diketones (von Wettstein-Knowles, 1972). Presumably /8-diketones are hydroxylated in a manner similar to that discussed above for the synthesis of secondary alcohols from hydrocarbons. 

Malaysia (9,10). in 1993, the Shell SMDS (Shell middle distillate synthesis) plant at Bintulu came online. The syngas is produced by noncataljrtic partial oxidation of offshore natural gas. The H2/CO ratio of this gas is 1.7 and because this is lower than that required for the FT synthesis, the additional hydrogen is produced by catalytic steam reforming of the FT tail gas. The plant s capacity is about 0.6 Mt per year. The FT wax is hydrocracked to give a high yield of diesel fuel. 

CO is the only reactant for the low-temperature FT synthesis for wax and diesel and the cobalt catalyst is not active for shift reaction. It means that the syngas should have a minimum content of CO2, which remains inert in the FT synthesis and hence represents a carbon (oxygen) loss. This is different from the high-temperature FT synthesis and the methanol synthesis for which the catalyst is active for shift reaction. CO2 is normally returned to the syngas plant as shown in Figure 2.31. 

The latest advances in bio-based polymers are beyond the scope of this chapter, however, the reader can refer to a number of reviews [4-6] on the synthesis and applications of biopolymers. Instead in this chapter, we will review latest advances in liquid repellent surfaces and materials based on biopolymers staring with cellulose, other polysaccharides such as starch and chitosan, biodegradable polyesters, and plant waxes. It is hoped that this chapter will encourage researchers actively engaged in conventional liquid repellent technologies to explore new techniques and materials based on biodegradable polymers. 

Avato, P. (1984) Synthesis of wax esters by a cell-free system from barley (Hordeum vulgare L.). Planta 162, 487-494 Avato, P., Bianchi, G., Salamini, F. (1985) Absence of long chain aldehydes in the wax of the glossy 11 mutant of maize. Phytochemistry 2At 1995-1997 Haas, K., Rentschler, I. (1984) Discrimination between epi-cuticular and intracuticular wax in blackberry leaves ultrastructural and chemical evidence. Plant Sci. Lett. 

The reaction mechanisms advanced are discussed in the light of a new hypothesis and in relationship to feeding experiment data, chemical genetic evidence and an abiological biomimetic synthesis of B-diketones. As hentriacontan-14,16-dione 6 is the commonest B-diketone found in cereal plant waxes we shall use it as model for our discussion (Scheme). 

The main components of plant waxes are listed in Table 6.10. In general, most of the major constituents are non-polar molecules with long hydrocarbon chains. The pathway of synthesis determines whether the final products have odd- or even-numbered carbon chains. 

In 1991, the relatively old and small synthetic fuel production faciHties at Sasol One began a transformation to a higher value chemical production facihty (38). This move came as a result of declining economics for synthetic fuel production from synthesis gas at this location. The new faciHties installed in this conversion will expand production of high value Arge waxes and paraffins to 123,000 t/yr in 1993. Also, a new faciHty for production of 240,00 t/yr of ammonia will be added. The complex will continue to produce ethylene and process feedstock from other Sasol plants to produce alcohols and higher phenols. 

A similar process to SMDS using an improved catalyst is under development by Norway s state oil company, den norske state oHjeselskap AS (Statod) (46). High synthesis gas conversion per pass and high selectivity to wax are claimed. The process has been studied in bubble columns and a demonstration plant is planned. 

Gas-to-liquids (GTL) is the chemical conversion of natural gas into petroleum products. Gas-to-liquid plants use Fischer-Tropsch technology, which first converts natural gas into a synthesis gas, which is then fed into the Fischer-Tropsch reactor in the presence of a catalyst, producing a paraffin wax that is hydro-cracked to products (see also Chapter 7). Distillate is the primary product, ranging from 50% to 70% of the total yield. 

The picture shows the Sasol Slurry Phase Distillate (SPD ) process plant, which converts at low temperatures synthesis gas to paraffins and specialty waxes. We express our gratitude to A. Buchanan and A. Rautenbach, both from Sasol, for kindly providing us with these figures. 

Isophorone is a solvent for a large number of natural and synthetic polymers, resins, waxes, fats, and oils. Specifically, it is used as a solvent for concentrated vinyl chloride/acetate-based coating systems for metal cans, other metal paints, nitrocellulose finishes, printing inks for plastics, some herbicide and pesticide formulations, and adhesives for plastics, poly(vinyl) chloride and polystyrene materials (Papa and Sherman 1981). Isophorone also is an intermediate in the synthesis of 3, 5-xylenol, 3, 3, 5-trimethylcyclohexanol (Papa and Sherman 1981), and plant growth retardants (Haruta et al. 1974). Of the total production, 45-65% is used in vinyl coatings and inks, 15-25% in agricultural formulations, 15-30% in miscellaneous uses and exports, and 10% as a chemical intermediate (CMA 1981). 

The introduction of iron-zinc catalysts led to the low pressure nthesis of liquid and solid hydrocarbons from CO/Hj in 1925 [19. 20. However, it was found that these catalysts were deactivated rapidly and thus further investigations concentrated on nickel and cobalt catalysts. They led to the introduction of a standardized cobalt-based catalyst for llic normal-pressure synthesis of mainly saturated hydrocarbons at temperatures below 200 C. In 1936, the first four commercial plants went on stream. Until 1945 the Fischer-Tropscit synthesis was carried out in nine plants in Germany, one plant in France, four plants in Japan and one plant in Manchuria. The total capacity amounted to approximately one million tons of hydrocarbons per year in 1943. The catalysts used consisted of Co (1(X) parts), ThO (5 parts). MgO (8 parts), and kieselgur (200 parts) and were prepared by precipitation of the nitrates. These catalysts were used in fixed-bed reactors at normal or medium pressures (< 10 bar) and produced mainly saturated straightproduct obtained consisted of 46% gasoline. 23% diesel oil, 3% lubricating oil and 28% waxes (3.15). 

Packed Bed. The packed-bed reactor used the Sasol plant to cany out Fis-cher-Tropsch syndiesis reaction is shown in Figure El-5.3. Synthesis gas is fed at a rate of 30,000 trf/h (STP) at 240°C twd 27 atm. to the packed-bed reactor. The reactor contains 2050 tubes, each of which is 5.0 cm in diameter and 12 m in length. The iron-based catalyst that fills these tubes usually contains KjO and St02 and has a specific area on the order of 200 in-/g. The reaction products are light hydrocarbons along with a wax that is used in candles and printing inks. Approxirn ly 50% conversion of the reactant is,achieved in the reactor. 

The FT process is well known and already applied on a large scale [9,10,11,12]. Currently, the two players that operate commercial Fischer-Tropsch plants are Shell and Sasol. In the Sasol and Shell plants gasification of coal and partial oxidation of natural gas, respectively, produce the syngas for the FT synthesis with well-defined compositions. Shell operates the SMDS (Shell Middle Distillate Synthesis) process in Bintulu, Malaysia, which produces heavy waxes with a cobalt catalyst in multi-tubular fixed bed reactors. Sasol in South Afirica uses iron catalysts and operates several types of reactors, of which the slurry bubble column reactor is the most versatile (i.e. applied in the Sasol Slurry Phase Distillate SSPD),... 

Acetone is obtained by fermentation or chemical synthesis and is used to make plastic, fibers, drugs, and other chemicals. It is also used to dissolve fats, oils, waxes, resins, rubber, plastics, lacquers, varnishes, and rubber cements. In the laboratory, it is used to extract various substances from animal and plant tissues and as a dehydrating agent. 

Larger scale Fischer-Tropsch synthesis runs were performed in a pilot plant slug-flow slurry reactor using 3-8kg catalyst as well as in a slurry phase bubble column demonstration unit using 500-1500kg catalyst. The reaction conditions were similar to those in the laboratory CSTR runs. The reactor wax production varied between 5 and 30kg per day for the pilot plant runs and up to 60 bbl/day for the demonstration unit. On-line catalyst samples were taken for particle size distribution measurements and Scanning Electron Microscope analyses. 

Fig. 1. Cobalt content in secondary filtered wax during pilot plant scale Fischer-Tropsch synthesis runs, using catalyst A 30gCo/0.075gPt/100gAl203 (run F102).

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