Processes hydroisomerization

There are currentiy three important processes for the production of isobutylene (/) the extraction process using an acid to separate isobutylene (2) the dehydration of tert-huty alcohol, formed in the Arco s Oxirane process and (3) the cracking of MTBE. The expected demand for MTBE wHl preclude the third route for isobutylene production. Since MTBE is likely to replace tert-huty alcohol as a gasoline additive, the second route could become an important source for isobutylene. Nevertheless, its avaHabHity wHl be limited by the demand for propylene oxide, since it is only a coproduct. An alternative process is emerging that consists of catalyticaHy hydroisomerizing 1-butene to 2-butenes (82). In this process, trace quantities of butadienes are also hydrogenated to yield feedstocks rich in isobutylene which can then be easHy separated from 2-butenes by simple distHlation. 

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. 

The hydroisomerization of linear alkanes nowadays is among the most demanded technologies for transformation of naphtha into high octane gasoline. However, while the processes for hydroisomerization of C4 and C5 - C6 cuts are well established (PENEX, ISOTEX, TIP, HYSOMER, ISOFIN, SKIP, PAR-ISOM), there is no suitable technology for the conversion of longer alkanes (C7 - C8 cuts). 

The development of composite micro/mesoporous materials opens new perspectives for the improvement of zeolytic catalysts. These materials combine the advantages of both zeolites and mesoporous molecular sieves, in particular, strong acidity, high thermal and hydrothermal stability and improved diffusivity of bulky molecules due to reduction of the intracrystalline diffusion path length, resulting from creation of secondary mesoporous structure. It can be expected that the creation of secondary mesoporous structure in zeolitic crystals, on the one hand, will result in the improvement of the effectiveness factor in hydroisomerization process and, on the other hand, will lead to the decrease of the residence time of products and minimization of secondary reactions, such as cracking. This will result in an increase of both the conversion and the selectivity to isomerization products. 

The co-refining synergy of natural gas liquids and Fe-HTFT was exploited for alkylate production. The natural gas liquids serve as a source of butane that can be hydroisomerized to yield isobutane that is alkylated (HF process) to produce a... 

Hysomer [Hydroisomerization] A process for converting -pentane and -hexane into branched-chain hydrocarbons. Operated in the vapor phase, in the presence of hydrogen, in... 

Isopol A hydroisomerization process for converting 1-butene to 2-butene. Developed by the Institut Frangais du Petrole. 

In addition to this, solid acid catalysts can also be used in the hydroisomerization cracking of heavy paraffins, or as co-catalysts in Fischer-Tropsch processes. In the first case, it could also be possible to transform inexpensive refinery cuts with a low octane number (heavy paraffins, n-Cg 20) to fuel-grade gasoline (C4-C7) using bifunctional metal/acid catalysts. In the last case, by combining zeolites with platinum-promoted tungstate modified zirconia, hybrid catalysts provide a promising way to obtain clean synthetic liquid fuels from coal or natural gas. 

Hydrocracking and hydroisomerization are related bond breaking and rearrangement processes which rely on the use of dual function catalysts operating under high hydrogen pressure to achieve their objectives. In fact, they share the same fundamental mechanistic steps and differ mainly in the degree to which some... 

Although not a separate process, isomerization plays an important role in pretreatment of the alkene feed in isoalkane-alkene alkylation to improve performance and alkylate quality.269-273 The FCC C4 alkene cut (used in alkylation with isobutane) is usually hydrogenated to transform 1,3-butadiene to butylenes since it causes increased acid consumption. An additional benefit is brought about by concurrent 1-butene to 2-butene hydroisomerization. Since 2-butenes are the ideal feedstock in HF alkylation, an optimum isomerization conversion of 70-80% is recommended.273... 

It is advantageous to pretreat butene feeds before alkylation.294-298 1,3-Butadiene is usually hydrogenated (to butenes or butane) since it causes increased acid consumption. The additional benefit of this process is that under hydrogenation conditions alkene isomerization (hydroisomerization) takes place, too. Isomerization, or the transformation of 1-butene to 2-butenes, is really attractive for HF alkylation since 2-butenes give better alkylate (higher octane number) in HF-cata-lyzed alkylation. Excessive 1,3-butadiene conversion, therefore, ensuring 70-80% isomerization, is carried out for HF alkylation. In contrast, approximately 20% isomerization is required at lower butadiene conversion for alkylation with H2SO4. 

Our study was undertaken specifically to investigate the processing of a typical raffinate to produce either high yields of LPG or isobutane as well as to determine the octane improvement in the C5+ fraction due to hydroisomerization. A 0.7 wt % Pd-15 wt % Ni-SMM catalyst was used for all the experimentation. 

The hydroisomerization of light paraffins (C5-C6-C7) to produce their branched isomers is an important industrial process aimed at improving the octane number of the light straight mm stream (LSR). Reformulated gasolines with their impact on olefins and aromatics reduction [26, 27] have increased the number of LSR isomerization units. Table 5.1 gives the octane number of the different C5-C7 linear and branched paraffins. 

Bifunctional zeolite catalysts are used in various commercial processes light alkane hydroisomerization (chapter 7), hydrocracking (chapter 6),hydrodewaxing (chapter 8), light alkane aromatization and hydroisomerization of the C8 aromatic cut (chapter 9). The hydrogenation/dehydrogenation components included in zeolite catalysts can be very different and located in different positions ... 

The increase of 1 unit of the RON corresponds to about 900.000 US per year for a 300.000 tpa hydroisomerization unit (1). In Figure 7.1, several major refinery processes to improve RON are shown these include isomerization, reforming, addition of FCC-Naphtha, alkylation, addition of oxygenates or polygas or butanes. The effect of these options with respect to the new specifications is different for each particular process. Keeping in mind the Californian ban on MTBE and also the fact... 

Hydroisomerization is one of the few major refinery processes that allow refineries to cope with the future fuel regulations on the one side and the necessity to supply premium fuel with the necessary octane on the other side. Due to the limited volume the chemical industry can cope with in addition to the present level, future reduction of the aromatics in fuels will force the refineries to convert as much of the aromatics as possible to fuel components. One possible option is to feed the one-ring aromatics such as benzene to an isomerization unit. A state of the art hydroisomerization catalyst such as HYSOPAR is very active for benzene hydrogenation at temperatures as low as 100°C, where 100% hydrogenation is achieved, and can cope with up to 15 wt.-% of benzene in the feed. When sulfur in the range of 50 ppm is present in the feed, a partial inhibition of... 

Hydroisomerization is also a key process. In this process, linear paraffins are converted to isoparaffins. This reaction greatly improves the pour point of the base oil, but results in a loss in VI. The catalyst is often noble metal supported on a controlled acidity support. The catalyst formulations are often proprietary and may utilize an amorphous silica-alumina or a modified molecular sieve. 

Description Crude C4 streams are converted into propylene and an isobutylene-rich stream in three IFP process steps (1) butadiene and C4 acetylenes selective hydrogenation and butenes hydroisomerization, (2) isobutylene removal via distillation or MTBE production and (3) metathesis (Meta-4). 

The hydroisomerization step features complete C4 acetylenes and butadiene conversion to butenes, maximum 2-butenes production, flexibility to process different feeds, polymer-free product and no residual hydrogen. The second step separates isobutylene either by conventional distillation, or by reacting the isobutylene with methanol to produce MTBE. 

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