Ethylene Shell process

Shell Higher Olefins Process (SHOP). In the Shell ethylene oligomerization process (7), a nickel ligand catalyst is dissolved in a solvent such as 1,4-butanediol (Eig. 4). Ethylene is oligomerized on the catalyst to form a-olefins. Because a-olefins have low solubiUty in the solvent, they form a second Hquid phase. Once formed, olefins can have Htfle further reaction because most of them are no longer in contact with the catalyst. Three continuously stirred reactors operate at ca 120°C and ca 14 MPa (140 atm). Reactor conditions and catalyst addition rates allow Shell to vary the carbon distribution. 

TABLE 8 Composition of the Ethylene Oligomer Product of the Shell Process ... 

In contrast to the processes of Ethyl and of Chevron/Gulf, which use Ziegler catalyst in the oligomerization of the ethylenes, Shell uses a self-developed catalyst system consisting of, for example, a nickel salt, a rm-organophosphine group, and a polar solvent such as 1,4-butanediol (3) [34,35] ... 

In the first process the yield does not exceed 65% of the starting compound due to simultaneous formation of 1,2-propanediol, while, in the second, a yield of 80% is obtained. Adding the fact that the market price of ethylene oxide is lower than acrolein, the Shell process can be regarded as economically more favorable. This is reflected in the much higher production volume reported for the production of 1,3-PD from ethylene oxide, which amounted to 45,000 t/a in 1999 as opposed to 9000 t/a from acrolein. The relatively high production costs with the acrolein process have probably induced the Dupont Company to invest in research efforts to further develop the biological process (see below). 

Propanediol is produced either from the reductive hydration of acrolein (Degussa-DuPont process), or through reductive carbonylation of ethylene oxide (Shell process), or through fermentation of glucose via glycerol (DuPont-Genencor process). 

Alternatives to oxychlorination have also been proposed as part of a balanced VCM plant. In the past, many vinyl chloride manufacturers used a balanced ethylene—acetylene process for a brief period prior to the commercialization of oxychlorination technology. Addition of HC1 to acetylene was used instead of ethylene oxychlorination to consume the HC1 made in EDC pyrolysis. Since the 1950s, the relative costs of ethylene and acetylene have made this route economically unattractive. Another alternative is HC1 oxidation to chlorine, which can subsequendy be used in direct chlorination (131). The Shell-Deacon (132), Kel-Chlor (133), and MT-Chlor (134) processes, as well as a process recendy developed at the University of Southern California (135) are among the available commercial HC1 oxidation technologies. Each has had very limited industrial application, perhaps because the equilibrium reaction is incomplete and the mixture of HC1, CL, CL, and water presents very challenging separation, purification, and handling requirements. HC1 oxidation does not compare favorably with oxychlorination because it also requires twice the direct chlorination capacity for a balanced vinyl chloride plant. Consequendy, it is doubtful that it will ever displace oxychlorination in the production of vinyl chloride by the balanced ethylene process. 

Probably the first example of a process employing the biphasic concept is the Shell process for ethylene oligomerization in which the nickel catalyst and the ethylene reactant are dissolved in 1,4-butanediol, while the product, a mixture of linear alpha olefins, is insoluble and separates as a second (upper) liquid phase (see Fig. 7.1). This is the first step in the Shell Higher Olefins Process (SHOP), the largest single feed application of homogeneous catalysis [7]. 

The Shell EO process is licensed under the name Shell MASTER process when combined with the Shell ethylene glycols process, and under the name Shell OMEGA process when combined with the Shell process for selective MEG production via ethylene carbonate intermediate. 

The performance of the PPR for NOx removal by the Shell low-temperature NOx reduction has been investigated extensively [20]. In the first commercial application of the Shell process with parallel-passage reactors, flue gases of six ethylene cracker furnaces at Rheinische Olefin Werke at Wesseling, Germany, are treated in a PPR system with 120-m catalyst in total to reduce the nitrogen oxide emissions to about 40 ppm v. Since its successful start-up in April 1990, the unit has performed according to expectations... 

Heterolytic liquid-phase oxidation processes are more recent than homolytic ones. The two major applications are the Wacker process for oxidation of ethylene to acetaldehyde by air, catalyzed by PdClj-CuCL systems, and the Arco oxirane or Shell process for epoxidation of propylene by f-butyl or ethylbenzene hydroperoxide catalyzed by molybdenum or titanium complexes. These heterolytic reactions require less drastic conditions than the homolytic ones... 

This reaction is accompanied by complete combustion into water and carbon dioxide. The only selective catalyst known is based on silver. This catalyst was known as early as the 1930s and has been continuously improved since then in a rather empirical way. It has been discovered that the catalyst may be promoted by the addition of alkali metal ions. Moreover, the presence of chlorine has a beneficial effect (cf. Fig. 5.30) [124]. Chlorine has to be added continuously because it disappears from the surface by reacting to give chlorinated ethane. It is sufficient to mix 10-40 ppm chlorine with the feed. The feed consists of a mixture of ethylene (24%), oxygen (8%) and the balance of inert gases. The reaction rate was found to be first order in oxygen and zero order in ethylene in the Shell process. 

The Shell process, now in commercial operation (see process description) uses a phosphoric acid-on Celite catalyst to effect a 4.2 per cent once-through conversion. Mace and Bonilla showed that a tungsten oxfde-on silica gel catalyst was the most effective of several types investigated. Yields of 4.6 mole per cent were obtained at optimum conditions of 580 F (300 C), 2,000 psi pressure, steam ethylene mole ratio of 1, and a space velocity of 1,500 reciprocal hours. 

Ethanol via Direct Hydration. The Shell Ih-ocess. The production of ethanol by the direct addition of water to ethylene is being carried out successfully on a commercial scale. In the Shell process a phosphoric acid-on Celite catalyst is used in the reaction ... 

Table 2.5 demonstrates the dependence of the cooling zone length which provides 0 °C (273 K) in a reaction zone at a given output and the values (-35 °C (238 K) and 258 °C (531 K)), on the radius R (the ethylene hydrochlorination process is given as an example) for various numbers of tubes in a shell-and-tube turbulent reactor. 

Table 2.5 The dependence of cooling length zone (Tp = 0 on the number of tubes N and radius R in3L shell-and-tube turbulent reactor for the ethylene hydrochlorination process (AP = 322.5 kg/m, q = 552 kilojoules/ kg, k = 10 1/mol-s, y = 1 m/s, Tq = -10 and AT = 100 C) ...

Parker (12) recommended the use of a distillation reactor for hydrolyzation of ethylene oxide to ethylene glycol. Miller (13), and subsequently Corrigan and Miller (14), analysed this process using a crude plate model and concluded that increased temperature in the distillation reactor adversely affected selectivity of the process as com )ared to the two-stage Shell process. However, this was disproved by Sive (15) who found no effect on selectivity of operating pressure or feed composition when modelling a packed distillation reactor for this process. 

Higher olefins from ethylene (Shell Higher Olefin Process)... 

The most modern ethylene oligomerization process—SHOP (Shell higher olefin process)—consists of three steps ethylene oligomerization, oligomers isomerization and cometathesis (Figure 2) [291]. 

Oligomerization processes practized embrace monoenes and dienes. Here the synthesis of a-olefins from ethylene (Shell Higher Olefin Process), the oligomerization of propylene/butene (Dimersol Process), and... 

A very comprehensive review deals with the catalytic dimerisatlon of ethylene and propene.139 The Shell Higher Olefin (ethylene oligomerisation) Process has been reviewed briefly.lAO The cationic Ni complexes (35) trimerise propene mainly to hexenes and methylpentenes.lAl Olefin oligomerisation catalysts, e.g. (36) and (37), cyclise 1,5-hexadiene, mainly to methylenecyclopentane (c.f. ref.90).142 37) Also dimerlses 1-butene to 2-,... 

Shell Higher Olefin Process) plant (16,17). C -C alcohols are also produced by this process. Ethylene is first oligomerized to linear, even carbon—number alpha olefins using a nickel complex catalyst. After separation of portions of the a-olefins for sale, others, particularly C g and higher, are catalyticaHy isomerized to internal olefins, which are then disproportionated over a catalyst to a broad mixture of linear internal olefins. The desired fraction is... 

---