PROCESS FOR OBTAINING ALKYLATION GASOLINE THROUGH THE USE OF REFINERY BLENDS AND ORGANIC ACIDS

Abstract

The present disclosure describes a new production process of alkylate gasoline through the application of a Batch reactor which mixes a hydrocarbon feed from an alkylation plant containing olefins and iso-paraffins, and methanesulfonic acid as the catalyst, under certain conditions of pressure, and temperature, at weight ratio no lower than 50 weight % of catalyst respective to hydrocarbons, and a stirring velocity of 1000 rpm. The alkylate product keeps a quality similar to that obtained using commercial catalysts such as sulfuric acid. The new catalyst can be reused up to 4 reaction cycles without significant reduction in its catalytic activity.

Claims

1. A process for production of alkylate gasoline using refinery mixtures and organic acids, said process comprising: (a) adding an organic acid, selecting only methanesulfonic acid at 99% purity in amounts ranging from 10 to 50 weight % respective to the mass of gas mixture, to a batch reactor provided with a Teflon lining; (b) sealing and cooling the reactor up to 5 C.; (c) adding a refinery mixture containing olefins and iso-paraffins, by the employment of micrometric valves; (d) connecting the reactor to a heating device and heating to a rate of 5 C./minute up to a temperature within a range of 0 to 140 C.; (e) injecting nitrogen to pressures within a range of 2 to 6 MPa and, at the same time, stirring the reaction at 1500 rpm using the reactor's propeller at reaction times from 5 to 30 minutes; (f) shutting off heating and stirring; (g) cooling down the product mixture up to ambient temperature; (h) taking a gas sample by using a gas collector plastic bag; (i) afterwards, cooling down the reactor to 5 C.; (j) extracting the liquid product at 5 C.; (k) neutralizing the alkylate gasoline with a saturated solution of sodium bicarbonate at ambient temperature; and (l) regenerating the used catalyst under the following conditions: temperature of 80 C.; pressure of 3 MPa; time of 15 minutes; stirring at 1000 rpm; and catalyst/hydrocarbon ratio of 50 wt %.

2. The process according to claim 1, wherein a potential catalyst is recovered from the reaction mixture without any prior treatment.

3. A catalyst produced according to the process of claim 2.

4. A method comprising using the catalyst according to claim 3, wherein the catalyst is used in up to 4 reaction cycles without any detrimental effects on catalytic activity of the catalyst.

5. The method according to claim 4, wherein the maximum weight ratio is 50 weight % of catalyst to the hydrocarbon mixture, and minimum stirring is at 1000 rpm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] With the aim clarify the description of the process for the production of alkylate gasoline, through the use of refinery mixtures and organic acids, subject of this disclosure, reference to the drawing will be made, with no limitation of the scope of the present disclosure:

[0014] FIG. 1 shows the scheme of the catalyst system used for the alkylation reactions, which contains: [0015] 1. Feed tank [0016] 2. Micrometric Valve [0017] 3. Filter [0018] 4. Feeding Bomb [0019] 5. Passage Valve [0020] 6. Relief Valve [0021] 7. Nitrogen Tank [0022] 8. Stirring Device [0023] 9. Reactor [0024] 10. Safety Valve [0025] 11. Vent [0026] 12. Reaction Mixture [0027] 13. Catalyst

[0028] FIG. 2 depicts the plot exhibiting the temperature effect in the alkylate volume and on the TMP/DMH ratio.

[0029] FIG. 3 shows the plot of the effect of the temperature on the olefin's conversion and the selectivity towards the TMPs and C8s hydrocarbons.

[0030] FIG. 4 is the plot showing the effect of reaction time on the selectivity, both to C8s and TMP/DMH.

[0031] FIG. 5 presents the plot showing the effect of reaction time on the volume of gasoline and on the TMP/DMH ratio.

[0032] FIG. 6 provides the plot that shows the effect of the reaction pressure on the selectivity towards C8s and TMPs

[0033] FIG. 7 provides the plot that shows the effect of the reaction pressure on the volume of the produced gasoline and on the TMP/DMH ratio.

[0034] FIG. 8 exhibits the plot showing the reusability of the catalytic process through the values of C8s, C9+ and C5-C7.

[0035] FIG. 9 shows the results of recyclability of the MSA catalyst, undertaken at Batch experiments at 50 C.

DETAILED DESCRIPTION

[0036] The present disclosure describes a new process to produce alkylation gasoline by using a batch reactor in which a hydrocarbon load from an alkylation plant composed of olefins and iso-paraffins, and methanesulfonic acid used as catalyst. Hydrocarbons and catalyst are mixed under certain conditions of pressure, time, and temperature, at a weight ratio equal to or less than 50% catalyst to hydrocarbons, and with a stirring of not less than 1500 rpm. The alkylated product maintains the quality to that obtained with commercial catalysts such as sulfuric acid. The new catalyst can be reused without any pretreatment for up to 4 reaction cycles without showing a significant decrease in its catalytic activity.

[0037] With the use of hydrocarbon mixtures from a refinery, it is possible to convert iso-paraffins and alkenes into alkylation gasoline (alkylated product), using batch reactors and organic catalysts, such as methanesulfonic acid. The components of the reaction mixture to be transformed are listed in Table 1. This mixture corresponds to the typical feed composition of a hydrofluoric acid-based alkylation plant working in a local refinery in the central region of Mexico, under the operating standards of the state oil company (PEMEX).

[0038] The tests are carried out in a reaction apparatus as shown in FIG. 1, where the batch reactor (9) used is provided with temperature controls and propeller-type stirring means. Externally, the reaction system includes a storage tank for gas loading (1), a tank for the nitrogen feed (7), a tank for the feed (8), discharge and feed valves, among the rest of the peripherals and controls.

TABLE-US-00001 TABLE 1 Composition of the gas charge used in alkylation tests. Compound Composition (mol %) Hydrogen 0.094 C6+/C5= 0.008 Propane 0.300 Propylene 0.794 Isobutane 67.174 n-Butane 3.713 1-Butene 4.955 Isobutylene 1.620 t-2-Butene 5.424 c-2-Butene 3.518 1,3-Butadiene 0.040 Isopentane 0.011 Carbon Dioxide 0.003 Etane 0.004 Oxygen/Argon 0.114 Nitrogen 12.228 Total 100

[0039] Before the hydrocarbon mixture is loaded into the reactor, the catalyst, which consists only of reagent grade methanesulphonic acid (99% purity), and without prior purification treatment, is added into a Teflon-lined reactor (a mass equivalent to 50% by weight of the hydrocarbon mixture), closing the reactor, and then vacuum is applied to the reactor using a vacuum pump.

[0040] After loading the catalyst, the reactor is pre-weighed and the weight is tared on a balance, after which the hydrocarbon mixture (50 weight % of the catalyst) is loaded at 5 C., using micrometric valves to control the flow. Once the reactor is loaded, it is connected to the heating grid, at a rate of 5 C./min until the desired temperature is reached. Once the working temperature (20 to 140 C.) is reached, nitrogen is injected into the reactor to achieve the working pressure. The system pressure (2 to 6 MPa) will tend to vary as the gasoline is formed.

[0041] After the reaction time has elapsed, the reactor is cooled down to room temperature to collect gas samples and then, to 5 C., the reactor is completely discharged and collected the liquid product, which is separated by decanting and neutralized with a saturated sodium bicarbonate solution. Both gaseous and liquid samples are taken for gas chromatographic analysis.

[0042] Experimental results. Preliminary experiments were carried out to determine the optimal conditions that allow to obtain high olefin conversions, with high C8 content, specially to trimethyl-pentanes (TMPs), which is demonstrated with the values of trimethylpentanes/dimethyl hexanes ratio (TMP/DMH) and the alkylate obtained alkylate volume. Therefore, 3 variables were chosen as the reaction's critical conditions to study, to name: pressure, temperature and reaction time. The interpretation of the results is described as follows:

[0043] Effect of the reaction temperature: FIG. 2 exhibits the conversion and selectivity results of the executed tests withing the temperature range of 0 to 140 C. using MSA as catalyst and the following constant conditions: pressure: 2 MPa, time, 30 min, HC/MSA 50 wright %, agitation: 1500 rpm. As FIG. 2 shows, the olefins conversion increases as the temperature does, which provokes an important reactant consumption, leading to an increase in yield and thus, higher gasoline production. In the same FIG. 2, it is also noticeable that the TMPs selectivity drastically decreases because of the increased number of secondary reactions that take place during the process. Such reactions are mainly olefin oligomerization, catalytic cracking of the produced hydrocarbons, or isomerization of some of the hydrocarbon products. Despite this, it is possible to determine that, at high temperatures, it is possible to obtain selectivity values comparable to those that are currently reached using sulfuric acid as catalyst.

[0044] FIG. 3 represents the temperature to alkylate volume relationship and the TMP/DMH ratio. This last value is also a significant reference to determine the quality of the alkylate, since sulfuric acid displays a ratio of 6. The results show that, when increasing the reaction temperature, the volume of alkylate gets increased, and the highest volume is reached at 120 C.; however, the quality of the hydrocarbon notoriously decreases. On the other hand, at 80 C. a high gasoline volume is obtained, (about 3.0 mL respective to the amounts of reactants), with the TMP/DMH of about 8.4, higher than that reached by sulfuric acid (TMP/DMH of 6).

[0045] Effect of the reaction time. The reaction time exerts a significant effect on the gasoline quality that is obtained using the proposed process, this is due to the velocity at which the secondary reactions take place, producing undesired products. These tests were carried out under the following conditions: temperature 80 C., pressure 2 MPa, HC/MSA ratio 50 weight %, agitation: 1500 rpm at 4 different times (5, 10, 15 and 30 min). The results are shown in FIGS. 4 and 5. FIG. 4 shows the relationship between reaction time with the selectivity, from where it can be seen that, at 15 min reaction, the selectivity is drastically decreased. From both figures, it is possible to conclude that high quality gasoline can be obtained at reaction times lower than 30 min. FIG. 5 is a double axe plot, where the relationship between the reaction time and the alkylate volume and TMP/DMH ratio is seen. It is possible to see that at 15 min, one can secure the production of high volumes of gasoline (about 3 mL) of high quality (TMP/DMH ratio of 9.1).

[0046] Effect of the reaction pressure. FIG. 6 shows the relationship between the pression of the reaction and the selectivity to C8s and TMPs. The reactions were carried out under the following conditions: Temperature 80 C., time 15 min, HC/MSA ratio of 50 weight %, agitation: 1500 rpm at 2, 3.5, 4 and 6 MPa of pressure. From a practical perspective, the change in pressure did not represent any change in trend, whether to increase or decrease the selectivity, since such parameters erratically changed, showing no trend (see FIG. 6). In practice, it seems favorable to leave a low pressure, which means that no nitrogen was necessary to increase it. Instead, the final pressure of 2 MPa was autogenic. Notwithstanding, FIG. 7 proofs that the increase in pressure favors the yield of the gasoline product (up to 3 mL respective to the used reactants), keeping the TMP/DMH ratio values higher than those obtained using sulfuric acid as catalyst. These results indicate that an increase in pressure leads to a higher yield of products, representing advantages when industrial applications are envisaged.

[0047] Effect of the catalyst/hydrocarbon (cat/HC) weight ratio. FIG. 8 presents the relationship between the weight % of the catalyst and the conversion/selectivity values of the obtained alkylate. The conversion of butenes is notoriously increased when the catalyst mass is also increased, but the selectivity to TMPs is significantly diminished (from 58% to 32.2 and 28.5% at 10, 25 and 50 weight %) and, regarding the selectivity to C8s, this falls at 25 wt. % of catalyst; however, it ends in a value of 60% at 50 weight % of catalyst.

[0048] Catalyst reuse. The gasoline production process here described can be boosted by the reuse of the single catalyst, namely, methanesulfonic acid. The reuse process can be described as follows:

[0049] Once the reaction time is accomplished, the reactor is vented, at 5 C. by using the scape valves. Later on, the reactor is opened, and the liquid content is decanted to a beaker at 0 C., where the volatiles are allowed to evaporate. Part of the catalyst remaining in the reactor is at the solid phase, which allows to be easily separated from the reaction products by decantation, so it can be used in a subsequent reaction cycle without any previous treatment. It is expected that a fraction of the catalyst is lost during the handling of the reactor, but also it can be lost due to its mixing with the alkylate product. In this case, the amounts of reactants are adjusted to the amount obtained of used catalyst.

[0050] FIG. 9 shows the results of recyclability of the MSA catalyst, undertaken at Batch experiments at 50 C. These results reveal a stable catalytic activity for up to 4 reaction cycles, reaching selectivity to C8 higher than 60%. After the 4th reaction cycle, the catalytic activity starts to decay, and the heavy end products (C9+) become more abundant. To note that the amount of hydrocarbons lower than C8 (C5-C7) does not undergo significant modifications, showing that the production of lower ends by cracking reactions is negligible.

[0051] The results up to this point shown demonstrate the capacity of MSA to catalyze the alkylation reaction of olefins and iso-paraffins, and its capacity to be recycled in subsequent reaction cycles. The regeneration process shown here is not limited to Batch experiments, but it can be replicated at continuous regime processes, provided that the technical modifications are done.

[0052] General considerations of the gasoline production process of this disclosure: Through this gasoline production process, methanesulfonic acid (MSA) is used as the single catalyst for the reaction; this catalyst allows a proper separation from the reaction products, leading to a facile reutilization of the catalyst, which, in other processes such as that catalyzed by sulfuric acid, is more complicated, having to regenerate it with fresh acid to keep a minimum acidity of 90%.

[0053] This process describes the production of alkylate gasoline through a batch reaction, where, in the following order, are mixed: methanesulfonic acid, hydrocarbon mixtures coming from an alkylation plant, and nitrogen. These are heated to a certain temperature and stirred for a certain amount of time. Once the reaction time has been accomplished, the mixture is cooled to 5 C. and the alkylation product separated from the catalyst by simple decantation. The catalyst can be regenerated by separating form the reaction effluent (decantation) and re-introduction into the reactor without further pre-treatment.

EXAMPLE

[0054] The following example is presented to illustrate the process of production of alkylate gasoline with refinery mixtures and organic acids and should not be considered as a limitation of the technical scope of the present disclosure, but they tend to be informative about the best way to employ methanesulfonic acid as single catalyst and its evaluation in a proper way.

[0055] In a batch reactor, provided with an internal Teflon lining, methanesulfonic acid is added in amounts within the range of 10-50 weight % of that of the gas mixture. One the reactor is charged; it is sealed and cooler to 5 C. Then, at this temperature, the gas mixture from refinery is injected by using the micrometric valves; such mixture contains olefins and iso-paraffins. Once the mixture is charged, the reactor is taken to a heating place and heating is started at about 5 C./min heating rate, up to the temperatures oscillating between 0 and 140 C. Once the reaction temperature is reached, nitrogen is injected until the working pressure is reached, which is between 2 and 6 MPa. The stirring is started at 1500 rpm through the reactors propel. The working pressure will slightly change due to the formation of the alkylate gasoline. Once the reaction time has been accomplished (which can go from 5 to 30 min) the stirring is switched off, the temperature is stabilized to the ambient one, and then a gas sample is taken by a valve and collected in a plastic bag. The reactor is then cooled to 5 C. and, at that temperature, it is open to extract the liquid product (gasoline), which is kept at the same temperature in a cool bath, and then allowed to reach ambient temperature. Finally, the alkylate is neutralized with a saturated solution of sodic bicarbonate. One neutral, the produced alkylate is taken to a gas chromatograph to determine the content of TMPs and C8s.

BIBLIOGRAPHICAL REFERENCES

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