Olefin space velocity

A change in any one of the three included variables which improves the quality of the product will increase the numerical value of the factor hence, the larger the factor, the better the alkylate quality. In ordinary commercial operation F will vary from about 10 to 40. Acid content of the reaction mixture and reaction time, while not directly a part of the factor, are so interrelated that if the acid content is maintained above 40%, the olefin space velocity term correlates the effects of these variables satisfactorily. While reaction temperature has an important effect on product quality, it has not been included in this factor since this variable is ordinarily held constant at an optimum value for any well-... 

Control of the important operating parameters other than temperature and the degree of mixing has also led to significant improvements in alkylation (17). For example, the effects of isobutane-olefin ratio, acid strength, acid concentration in the reaction mixture, and olefin space velocity have been recognized, and efforts to control these variables in the preferred ranges have resulted in more profitable operations. 

In general, high ratios olefin/sulfuric acid increase acid consumption and decrease octane number. This ratio is often presented as olefin space velocity , defined as volume of olefin charged divided by the volume of H2S04 in the reactor. Typical values are in the range 0.25-0.5 h 1. For our process, the olefin space velocity is 0.5 h1, calculated for an emulsion containing 50% acid (45-65% is the recommended range). 

A second question is what might be done to improve selectivity beyond the usual practice of refiners to maximize mixing, maximize the isobutane to olefin ratio, lower the temperature and reduce the olefin space velocity. One approach is to decide what s rate determining and then to develop a chemical solution. This paper will be concerned with developing evidence that hydride transfer from a tertiary paraffin is generally slow and may be considered to be the rate determining step. The fact that a cation abstracts from Isobutane relatively slowly compared to... 

One series was made with an isobutane - 2-butene feed, 6.6% olefin, at 10°C and olefin space velocities of 0.077 to 0.7 V/Hr/V. The additives studied are listed in Table IV. 

In all cases some improvement in selectivity and octane quality was obtained. Cetylamlne and CTMAB showed the best results with typical improvements of about 0.5 MON and 1.5% in selectivity throughout the range of olefin space velocities. Figure 18 shows the improvements obtained with the C33 amine. 

Also shown in Table II is the effect of olefin space velocity. Comparison of Runs 4 and 6 shows that the Amberlyst-I5/BF3 catalyst can alkylate isobutane with butene in good yield at an olefin WHSV of 2.6 g olefin/g resin-hour. The alkylate yields are slightly lower than the theoretical value of 2,04 due to removal of some of the reactor contents via the on-line sampling system. The yields shown are based on the liquid... 

It is noteworthy that good performance was achieved at high olefin space velocities with low external isobutane/butene ratio. For comparison purposes sulfuric acid alkylation operates at an olefin space velocity of approximately 0.2-0.4, and an external iso-butane/olefin ratio of about 5. HF alkylation, while permitting operation at higher olefin space velocities than H2SO4 alkylation, requires external isobutane/ olefin ratio of about 15. 

It is well known that olefin space velocity and external isobutane/olefin ratio has a pronounced effect on alkylate quality with both H2SO4 and HF alkylation. 

Since the Amberlyst XN-IOIO/BF3 catalyst produced an alkylate with quality superior to the other resins tested, additional work was performed with this resin/ BF3 catalyst to explore the effects of particle size and temperature, and sensitivity to olefin type. Olefin space velocity was kept at 2.6 grams C4=/gram resin-hour for all the results reported below. 

As shovm, the selectivity for TMP and the RON of C5 alkylate increased sharply with decreasing temperature. An alkylate with a RON clear of 101.9 was produced at O C and an olefin space velocity of 2.6. 

Olefin Space Velocity - 0.15 vol. olefin/hr/vol. H2SO4 H2SO4 in Emulsion - 60 vol. %... 

The most important variables in the process are (1) reaction temperature, (2) acid strength, (3) iso-butane concentration, and (4) olefin space velocity. 

The effect of space velocity is interrelated with reactor geometry and the effect of olefin concentration. As long as alkylation and hydrogen transfer reaction rates are in balance (effect of T, I/O, etc.), yield and selectivity show little dependence on olefin space velocity (OSV). In general, a very high space velocity will increase acid consumption and formation of acid-soluble oils because of the higher probability of multiple olefins reactions. 

As mentioned with liquid acid catalysts, selectivity and yield remain at an almost constant high level when the olefin space velocity (OSV) is increased. However, a critical OSV can be identified above which the polymerization reactions rapidly start to increase. This is related to the available number of add sites and the rate... 

At sufficiently high I/O, selectivity vas optimized by varying reaction temperature. When the temperature vas lo vered, less C5-C7 and more of the desired Cg compounds vere formed. Also, at lo ver temperature, isomerization of high-octane TMPs to low-octane DMHs was reduced. However, when the temperature was reduced too much at a given olefin space velocity, overall olefin conversion was... 

Fig. 7. Relative decrease in butenes conversion for different zeolite structures. The alkylation reaction is performed in a fixed bed reactor at 50°C, 20 bar, I/O = 15, and olefin space velocity of 1 h . ...

Pig. 22. Comparison of the alkylation performance of K2.5H0.5PW catalyst in a fixed bed reactor under supercritical (140°C, 50 bars) and liquid phase (40°C, 30 bars) conditions (a) variation of butenes conversion with time on stream (expressed in grams of butenes fed per gram of catalyst), (b) product selectivities obtained after a total amount of olefin charged of 0.16 g/ g of catalyst. The experiments were conducted at an isobutane/butenes ratio of 64.3 and an olefin space velocity of 0.27 h"... 

The recent application of AlkyStar catalyst has reduced the number of reactors required in the AlkyClean process from five to three, owing to its extended service lifetime. In addition, higher olefin space velocities are allowed, while a lower I/O ratio can be employed, with the consequent savings in distillation and recirculation of isobutane. 

Information is not complete enough for the use of the polymerization chart (Fig. 20-8), but for an olefin composition ratio of 2.0, a reactor temperature of 380 T, an olefin space velocity of 0.08, a total space velocity of 0.18, and a catalyst activity of 50, the total conversion of olefins by weight will be about 90 per cent (this is a high total conversion). On such a basis, and if 90 per cent of the olefins are exposed to polymerization, the yield of polymer gasoline per 100 gal will be about ... 

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