Plants hydrocarbon synthesis

This section covers recent advances in the application of three-phase fluidization systems in the petroleum and chemical process industries. These areas encompass many of the important commercial applications of three-phase fluidized beds. The technology for such applications as petroleum resid processing and Fischer-Tropsch synthesis have been successfully demonstrated in plants throughout the world. Overviews and operational considerations for recent improvements in the hydrotreating of petroleum resids, applications in the hydrotreating of light gas-oil, and improvements and new applications in hydrocarbon synthesis will be discussed. 

Belingheri, L., Pauly, G., Gleizes, M. and Marpeau, A. (1988) Isolation by an aqueous two-polymer phase system and identification of endomembranes from Citrofor-tunella mitis fruits for sesquiterpene hydrocarbon synthesis. /. Plant Physiol, 132, 80-5. 

Coal gasification plants are in operation today and are used mainly for the production of hydrogen for ammonia synthesis and the production of carbon monoxide for chemical processes and for syngas feed for hydrocarbon synthesis. 

Ishwarane (20) and ishwarone (25) are two novel tetracyclic sesquiterpenes which have been isolated from Aristolochia indica Linn, and other tropical plants a synthesis of ishwarane was reported by Kelly and his co-workers in 1971. Kelly and Alward have now effected an improved synthesis of the hydrocarbon, which... 

Farley, R. and D. Ray. The Design and Operation of a Pilot Scale Plant for Hydrocarbon Synthesis in the Slurry Phase. J. 

Ministry of Fuel and Power (ref. 12), 89 T.E. Warren, Inspection of hydrogenation and Fischer-Tropsch plants in western Germany during September 1945, FIAT, Final report no. 80, item no. 30 (London, 1945), 1-28, on 16-18 Germany, liquid fuels, V-syn-thetic oil plants-Fischer-Tropsch synthesis, (typed) Report 75687, Reference numbers 5.01-5.09 "Coal hydrogenation-Germany, hydrocarbons synthesis," Petroleum press service, 6 (1939), 529-532. 

On the basis of the assumptions of model <22> and <23> the Fischer-Tropsch synthesis in a slurry phase BCR has been modeled [37, 38]. As this hydrocarbon synthesis from synthesis gas (CO + H2) is accompanied by considerable volume contraction, it is clear that gas flow variations have to be accounted for. The developed models are useful to evaluate experimental data from bench scale units and to simulate the behavior of larger scale Fischer-Tropsch slurry reactors. Though only simplified kinetic laws were applied, the predictions of the model are in reasonable agreement with data reported from 1.5 m diameter demonstration plant. Fig. 12 shows computed space-time-yields (STY) as a function of the inlet gas velocity. As the Fischer-Tropsch reaction on suspended catalyst takes place in the slow reaction regime, it is understood that STY passes through a maximum in dependence of uqo- The predicted maximum is in striking agreement with experimental observations [37]. 

The Shell Middle Distillate Synthesis (SMDS) process has been developed with these considerations in mind. It produces high-quality middle distillates from natural gas via synthesis gas and a hydrocarbon synthesis/cracking step. In August 1989, it was announced that the world s first commercial SMDS plant will be built in Bintulu in Sarawak, Malaysia, and that it will come on stream in the last quarter of 1992. 

On the basis of experiments with protoplasts from epidermal cells of barley leaf sheaths, the proposal was made that the plasmalemma and/or cell wall was the site of the epicuticular wax synthesizing machinery . The observations summarized above are pertinent in this respect. The cer-cqu determined polypeptide contains the enzymatic activity for the final step in the associated pathway consisting of at least the apparent decarboxylation and hydroxylation reactions. The latter would be expected to occur close to the plant surface. This is where the decarbonylation activity which is the final step in hydrocarbon synthesis in peas has been located more specifically in a cutin containing fraction of a microsomal preparation. That the condensing activity of the 0-ketoacyl elongase, which is... 

Secunda discharges no process water effluents. AU. water streams produced are cleaned and reused in the plant. The methane and light hydrocarbons in the product are reformed with steam to generate synthesis gas for recycle (14). Even at this large scale, the cost of producing fuels and chemicals by the Fischer-Tropsch process is dominated by the cost of synthesis gas production. Sasol has estimated that gas production accounts for 58% of total production costs (39). 

Imperial Chemical Industries (ICI) operated a coal hydrogenation plant at a pressure of 20 MPa (2900 psi) and a temperature of 400—500°C to produce Hquid hydrocarbon fuel from 1935 to the outbreak of World War II. As many as 12 such plants operated in Germany during World War II to make the country less dependent on petroleum from natural sources but the process was discontinued when hostihties ceased (see Coal conversion PROCESSES,liquefaction). Currentiy the Fisher-Tropsch process is being used at the Sasol plants in South Africa to convert synthesis gas into largely ahphatic hydrocarbons at 10—20 MPa and about 400°C to supply 70% of the fuel needed for transportation. 

SASOL. SASOL, South Africa, has constmcted a plant to recover 50,000 tons each of 1-pentene and 1-hexene by extractive distillation from Fischer-Tropsch hydrocarbons produced from coal-based synthesis gas. The company is marketing both products primarily as comonomers for LLDPE and HDPE (see Olefin polymers). Although there is still no developed market for 1-pentene in the mid-1990s, the 1-hexene market is well estabhshed. The Fischer-Tropsch technology produces a geometric carbon-number distribution of various odd and even, linear, branched, and alpha and internal olefins however, with additional investment, other odd and even carbon numbers can also be recovered. The Fischer-Tropsch plants were originally constmcted to produce gasoline and other hydrocarbon fuels to fill the lack of petroleum resources in South Africa. 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

The earliest method for manufacturiag carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally heated retorts. Safety concerns, short Hves of the retorts, and low production capacities led to the development of an electric furnace process, also based on reaction of sulfur and charcoal. The commercial use of hydrocarbons as the source of carbon was developed in the 1950s, and it was still the predominate process worldwide in 1991. That route, using methane and sulfur as the feedstock, provides high capacity in an economical, continuous unit. Retort and electric furnace processes are stiU used in locations where methane is unavailable or where small plants are economically viable, for example in certain parts of Africa, China, India, Russia, Eastern Europe, South America, and the Middle East. Other technologies for synthesis of carbon disulfide have been advocated, but none has reached commercial significance. 

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

The principal advance ia technology for SASOL I relative to the German Fischer-Tropsch plants was the development of a fluidized-bed reactor/regenerator system designed by M. W. Kellogg for the synthesis reaction. The reactor consists of an entrained-flow reactor ia series with a fluidized-bed regenerator (Fig. 14). Each fluidized-bed reactor processes 80,000 m /h of feed at a temperature of 320 to 330°C and 2.2 MPa (22 atm), and produces approximately 300 m (2000 barrels) per day of Hquid hydrocarbon product with a catalyst circulation rate of over 6000 t/h (49). 

In early times hydrogen cyanide was manufactured from beet sugar residues and recovered from coke oven gas. These methods were replaced by the Castner process in which coke and ammonia were combined with Hquid sodium to form sodium cyanide. If hydrogen cyanide was desired, the sodium cyanide was contacted with an acid, usually sulfuric acid, to Hberate hydrogen cyanide gas, which was condensed for use. This process has since been supplanted by large-scale plants, using catalytic synthesis from ammonia and hydrocarbons. 

Shell Gas B.V. has constructed a 1987 mVd (12,500 bbhd) Fischer-Tropsch plant in Malaysia, start-up occurring in 1994. The Shell Middle Distillate Synthesis (SMDS) process, as it is called, uses natural gas as the feedstock to fixed-bed reactors containing cobalt-based cat- yst. The heavy hydrocarbons from the Fischer-Tropsch reactors are converted to distillate fuels by hydrocracking and hydroisomerization. The quality of the products is very high, the diesel fuel having a cetane number in excess of 75. 

---