Patent Application
20200270531
The present invention relates to a process for obtaining a renewable hydrocarbon stream for use in gasoline formulations, and to the hydrocarbon stream and gasoline formulations thus obtained.
The debate concerning eventual exhaustion of the natural reserves of petroleum, as well as the need to reduce the level of emissions from vehicles with internal-combustion engines, have promoted interest in the development not only of vehicles that are more efficient, but also in research into new environmentally friendly fuels and catalytic converters. Therefore the use of renewable components is an increasingly frequent requirement in various segments of the fuels industry.
Renewable fuels, also known as biofuels, are fuels of biological origin. They are made from biomass such as maize, soya, sugar cane, castor seed, canola, palm oil or hemp.
The advantage of using biofuels is associated with the significant reduction in emissions of greenhouse gases compared to fuels derived from petroleum, as well as being a source of renewable energy. The main biofuels known at present are alcohol (ethanol), mainly produced from sugar cane and maize; biogas, produced from biomass; bioether, and biodiesel, among others. Biofuels may be used alone in vehicles or mixed with fossil fuels.
Among the biofuels mentioned above, ethyl tert-butyl ether (ETBE) and ethanol are products available in Brazil and are examples of biofuels that are widely used in gasoline formulations.
Gasoline is a fuel consisting basically of hydrocarbons and, in minor amounts, oxygenates such as alcohols and ethers, which are added to it at the distributors. These hydrocarbons are usually aromatic, olefinic, naphthenic and paraffinic and generally “lighter” than those that make up diesel oil, as they are formed by molecules with a shorter carbon chain, normally from 5 to 10 carbon atoms.
Depending on the application, the content of oxygen-containing components is limited by the product specification else they affect the properties of the fuel, mainly in relation to consumption and performance, due to the lower energy content of the oxygen-containing components relative to the hydrocarbons.
Besides the hydrocarbons and the oxygenates, gasoline may also contain sulphur compounds, compounds containing nitrogen, as well as additives for various purposes, among which we may mention detergents and deposit control additives. Therefore the chemical composition of gasoline is complex and may be subject to variations. As a rule, its boiling point is relatively low, which favours its use as a fuel. Furthermore, its combustion releases a very good potential amount of energy and its price is economically viable.
More particularly, automotive gasoline is created from various streams, called naphthas, arising from various refining processes. These naphthas differ from one another in respect of the types and contents of hydrocarbons that they contain, depending on the refining processes that produce them, which accounts for the variation in the constitution of gasoline.
Various processes may be used for obtaining gasoline from petroleum. The refining processes undergo continuous evolution simultaneously with progress in engine design. With design changes, mainly in respect of the compression ratio, for increase in power, the refiners improve the manufacturing processes for gasoline in order to satisfy the quality requirements, which are becoming more and more demanding. At the same time, higher consumption of gasoline has led to the development of processes giving higher yields. These objectives have led to the current state of the petroleum refining industry, constituting one of the most efficient and complex technologies.
The main processes used for production of gasoline are fractional distillation, vacuum distillation, thermal or catalytic cracking and catalytic reforming.
Cracking, which is widely used, consists of breaking long hydrocarbon molecules of high molecular weight into others with a shorter chain and lower molecular weight. It is an extremely important process industrially that makes it possible to obtain, from a single compound, various compounds with smaller molecules, which are used for various purposes.
Cracking may be thermal or catalytic. Thermal cracking is carried out at high temperatures and pressures. For example, to transform molecules in the kerosene distillation range, diesel oil or lubricating oil, into gasoline, the temperatures used are between 450° C. and 700° C. However, catalytic cracking does not require high temperatures and pressures, owing to the use of catalysts, making the process safer and more economical.
To assess the quality of gasoline, a property called octane number, also known as octane rating, is measured, which indicates the knock resistance on compression of the fuel.
In the octane rating scale, index 100 is ascribed to isooctane (2,2,4-trimethylpentane; C8H18), for which knock only occurs at high compression ratios, and index zero to n-heptane (C7H16), for which knock occurs at very low compression ratios.
The octane number of a gasoline informs that this fuel possesses knock resistance equivalent to that of a mixture of isooctane and n-heptane with a volume percentage of isooctane numerically equal to the octane number, when analysed in a standard engine. For example, a gasoline with an octane rating of 80 has knock resistance equivalent to that of a mixture of 80% v/v of isooctane and 20% v/v of n-heptane.
The relationship between organic compounds and octane rating obeys the following rules:
The higher the octane rating of a gasoline, the higher its knock resistance. Some components or even finished gasolines have an octane rating above 100, requiring the use of other standards for determining the octane rating, such as isooctane with addition of standardized contents of tetraethyl lead or aromatic compounds of known octane rating.
The octane rating is one of the most important parameters of gasoline quality, and is directly related to the performance of the product. However, other properties are important for performance, such as suitable volatility characteristics, combustion rate compatible with the application, and energy content sufficient to guarantee power and autonomy.
The availability of a gasoline stream that combines all of its optimized parameters in one and the same product, such as octane rating, combustion rate and energy content (calorific value), is still a challenge both from the technical and from the commercial standpoint.
From the above discussion it is clear that there is still a current need to obtain gasoline streams with properties that are more attractive from the standpoint of performance, especially higher calorific value, starting from renewable raw materials, to fill gaps in performance left by the renewable products currently available, for example oxygen-containing components (ethanol, ETBE, etc.).
In this connection, the attention of research and development teams has been directed towards obtaining these products from alternative biomass sources, especially with upgrading of by-products from processes that already exist.
Fusel oil, for example, is a residue/by-product obtained from fuel ethanol distilleries, consisting of a mixture of higher alcohols, such as isoamyl alcohol (IAA), isobutyl alcohol, among others. These alcohols are classified as congeners of alcoholic fermentation and must be removed in the rectification column, as they tend to accumulate in the unit. In countries where fuel ethanol is produced on a large scale, such as Brazil, alternatives for utilization of the residues generated in this process would be of great importance for making ethanol production less polluting and more profitable. The low price of fusel oil and its high content of isoamyl alcohol, coupled with the high volume of fusel oil produced in Brazil annually, would justify the development of technologies that require the use of this mixture.
Thus, there are various documents that describe processes such as those referred to above for obtaining automotive gasoline of renewable origin starting from these by-products. However, no processes have been developed that combine adaptation of refining technologies with the use of fusel oil or IAA as raw materials.
Document WO2013/169461, for example, describes a process for the production of olefins and aromatic hydrocarbons, in which a feed that comprises an oil from biomass pyrolysis, or a fraction thereof, is supplied to a steam cracking plant at a temperature from 600 to 1000° C., or a reverse flow reactor operating at a temperature from 900 to 1700° C., and one or more fractions of hydrocarbon effluents are produced by thermal cracking. However, the high temperatures and pressures employed in this cracking process mean it is not very economical and safe, and is therefore unattractive.
Document US2012/0220808A1 describes a process for the production of long-chain olefins at high yield and high selectivity by submitting long-chain primary aliphatic alcohols to a liquid-phase dehydration reaction. The term “liquid-phase reaction”, as used in the invention, signifies that the reaction is conducted at a temperature not above the boiling point of the raw alcohol, that is, at a temperature not above the temperature at which a liquid phase of the alcohol is still present.
However, there is still a need to develop a process for obtaining a renewable hydrocarbon stream consisting primarily of light olefins for use in the production of gasolines with properties that are more attractive from the standpoint of performance, particularly with higher calorific value.
As will be presented in greater detail below, the present invention aims to solve the problems of the prior art described above in a practical and efficient manner.
The present invention relates to a process for obtaining a renewable hydrocarbon stream suitable as a component of gasoline formulations, using by-products from ethanol production from sugar cane as raw material, and to the hydrocarbon stream and gasoline formulations thus obtained. The invention is defined in the claims.
According to a first aspect of the disclosure, there is provided a process for obtaining a renewable hydrocarbon stream suitable as a component of gasoline formulations, characterized in that it comprises one or more of: a) a dehydration reaction of a feed of by-products from ethanol production from sugar cane based on the technology of fluid catalytic cracking (FCC) in the presence of an optionally pulverized acid catalyst, at temperature and pressure in the range 350-550° C. and 0 kgf/cm2 (0 KPa) to 2 kgf/cm2 (196.13 KPa), respectively, wherein the catalyst/feed ratio used varies between 3 and 10; and b) distillation of the liquid product obtained in step a) at a temperature in the range from 20 to 70° C., preferably from 20 to 50° C., obtaining a hydrocarbon stream consisting primarily of olefins with 5 carbon atoms, wherein the degree of conversion of the by-products from ethanol production from sugar cane into olefins with 5 carbons is in the range from 80 to 100%.
The liquid product obtained in step a) can be cooled before continuing to the distillation step b).
The by-product from ethanol production from sugar cane can be fusel oil, and more preferably the isoamyl alcohol present therein.
The stream of olefins obtained in step b) can comprise a percentage of isoamylenes between 60 and 80%.
The temperature of the dehydration reaction can be in the range 450-500° C.
Tthe pressure of the dehydration reaction can be in the range from 1 kgf/cm2 (98.07 KPa) to 1.8 kgf/cm2 (176.52 KPa).
The pulverized acid catalyst can be alumina, silica-alumina, zeolite Y and/or mixtures thereof.
The catalyst/feed ratio can be between 4 and 8.
The degree of conversion of the by-product from ethanol production from sugar cane into olefins with 5 carbons can be in the range from 90 to 100%.
According to a second aspect of the disclosure there is provided a renewable hydrocarbon stream, characterized in that it is obtained by the process as discussed in connection with the first aspect.
The present disclosure relates to a process for obtaining a renewable hydrocarbon stream for use in gasolines, using by-products from ethanol production from sugar cane as raw material.
In particular, this disclosure deals with a process for obtaining a renewable hydrocarbon stream, preferably by means of a dehydration reaction of a by-product from ethanol production from sugar cane, particularly fusel oil and, more preferably, isoamyl alcohol present therein, bearing in mind the availability of these by-products on a large scale in Brazil. Said process is based on cracking technology of the fluidized bed catalytic cracking type (fluid catalytic cracking, FCC), which allows continuous and prolonged operation of the process in the vapour phase, using existing refinery equipment (dispensing with the use of a dedicated reactor) for obtaining a hydrocarbon stream consisting primarily of light olefins containing 5 carbon atoms.
The fluidized bed catalytic cracking process can employ suitable, commercially available catalysts that preferably include pulverized acid catalysts and, more preferably, alumina, silica-alumina, zeolite Y and/or mixtures of any or all of these components. The catalyst/feed ratio used in said dehydration reaction, which corresponds to the flow rate by weight of the feed (isoamyl alcohol or fusel oil) and catalyst circulation, can vary between 3 and 10, preferably between 4 and 8.
The reaction can take place at temperatures in the range from 350 to 550° C., preferably between 450 and 500° C. The operating pressures for the reaction are those typical of a fluidized bed catalytic cracking process (FCC) and can vary between about 0 kgf/cm2 (0 KPa) and 2 kgf/cm2 (196.13 KPa), preferably between 1 kgf/cm2 (98.07 KPa) and 1.8 kgf/cm2 (176.52 KPa).
The aforementioned operating conditions are selected so as to promote maximum conversion of the by-products from ethanol production from sugar cane into hydrocarbons containing mainly branched olefins with 5 carbon atoms, also known as isoamylenes. At the same time the reaction conditions avoid the formation of by-products from cracking and condensation such as Liquefied Petroleum Gas (LPG) (3 and 4 carbon atoms) and aromatics, such as benzene, toluene and xylenes, which are secondary products of octane rating and have lower calorific value. In general, the values of the degree of conversion of isoamyl alcohol to olefins with 5 carbons are in the range from 80 to 100%, preferably between 90 and 100%, and give rise to a light naphtha of excellent quality.
The liquid product obtained from the dehydration reaction is preferably cooled (to prevent loss of the isoamylenes by evaporation) and then distilled at a temperature in the range from 20 to 70° C., preferably between 20 and 50° C., in a TBP (true boiling point) column to separate the naphtha cut. As mentioned, the degree of conversion of isoamyl alcohol is high, above 80%. This can give as the final result, in addition to other by-products, a stream with a percentage of isoamylenes from 60 to 80% w/w, a high octane rating and stability compatible with the values observed for automotive gasolines. Furthermore, the content of sulphur and of nitrogen compounds present in the product derived from fusel oil is compatible for various segments of gasoline, including products that require low contents of impurities.
Therefore, compared to other processes for biomass conversion, dehydration of isoamyl alcohol is superior in maximizing the yield of the desired distillation range, and in avoiding the presence of oxygenates in the final fuel.
The following examples illustrate various embodiments of the present invention.
Preliminary tests for assessing the operating conditions of the FCC were carried out in a circulating pilot unit. The pilot unit was equipped with an adiabatic riser with a length of 1 m and an isothermal rectifier and a regenerator with temperature controlled by electric heating. The catalyst inventory of the unit was 2 kg and the flow rate of feed was 1 kg/h. The catalyst used was Ecat 1, a pulverized catalyst containing zeolite Y, used in a Petrobras commercial FCC unit in the cracking of gas oil. Table I presents the composition of the Ecat 1 catalyst (and Ecat 2, referred to further below), along with the specific area of the catalyst.
A feed of isoamyl alcohol (IAA) of petrochemical origin was used for studying the effect of the operating conditions, and the fusel oil used in run 3 was supplied by an ethanol distillery.
Table II presents a summary of the operating conditions of the pilot unit and of the yields of isoamylenes, including the cracking reaction temperature (TRX), and the catalyst to feed (oil) ratio (CTO). The operating conditions were selected so as to optimize the conversion of IAA, forming isoamylenes by dehydration, and at the same time minimize the formation of products with secondary octane rating and lower calorific value. Assessment of the processing of fusel oil was only conducted at the pilot scale, with a focus on assessing a lower-cost raw material. The fusel oil used in run 3 contained, based on dry matter, 76% w/w IAA (71% 3-methyl-1-butanol and 5% 2-methyl-1-butanol), 6% w/w butanols and 16% w/w ethanol. Overall, the fusel oil contained 17% w/w of water, resulting in lower yield of isoamylenes and higher yield of water compared to the IAA feed (run 1 vs run 3—Table II). To generate a sufficient volume of liquid product, runs lasting 3 hours were carried out. The liquid product was collected in a vessel cooled with dry ice (to prevent loss of the isoamylenes by evaporation) and then distilled in a TBP column to separate the naphtha cut (initial boiling point [IBP]=70° C.), generating a sample of approximately 1 L, sufficient for complete characterization.
Table III presents the data for characterization of the products generated in the pilot unit after distillation, including the lower calorific value (LCV) and the higher calorific value (HCV), and composition measured by gas chromatography (GC). The ASTM testing method reference for each parameter is included in brackets in the first column of the table.
It can be seen from Table III that all the cuts are light enough, with low density and high volatility (measured by RVP—Reid vapour pressure), showing that the process generates a stream with properties compatible with those of gasolines.
Regarding the energy content, it is observed that the products derived from processing the 99% fossil IAA had a lower calorific value (LCV) of about 44.3 MJ/kg, which is an excellent value, suitable for special gasoline formulations. The LCV of the product derived from the processing of fusel oil was approximately 2.3% less than that of the products derived from IAA, and this reflects the presence of the relatively high ethanol content (4.3% w/w) recovered in distillation. It should be emphasized that processing of fusel oil proved promising, as the negative impact observed on the LCV of the TBP cut can be corrected by adjusting the final boiling point (FBP) of the distillation cut (for example, 50° C.), which eliminates the presence of ethanol (boiling point [BP]=78° C.).
iValue of IP for mixture of 10% w/w component/90% w/w alkylated product (IP alkylated product > 1200 min)
iiCalculated from data on composition by GC
iiiRON of the pure sample. Sample very volatile, irregular combustion
ivRON value for mixture of 10% w/w component/90% w/w alkylated product (RON alkylated product = 98.5)
vRON value for mixture of 10% w/w component/90% w/w alkylated product (RON alkylated product = 96.4)
Regarding the octane rating, it was not possible to measure the RON (research octane number) of the pure products, owing to the high volatility of the cuts, which upsets the analysis. Only the cut from run 1 had its RON estimated at 99.4, showing that the stream has a high octane rating. Assessment of the octane rating of the products was carried out with mixtures of each stream with an alkylated product of high isooctane content (80-85% w/w), in the proportion of 10% w/w of the cut generated with 90% w/w of alkylated product. The RON octane rating of the mixtures compared with the octane ratings of the alkylated base used in the mixture showed that all the cuts had similar performance, with an intensified effect in the mixture.
Regarding the stability of the products, all the cuts showed values of actual and potential gum compatible with values observed for automotive gasolines. Regarding the induction period (IP), despite the low values of IP of the cuts, the results obtained in mixtures with a more stable stream (alkylated product) were much higher, indicating that they are not a problem.
Another point that deserves special mention is that the sulphur content and nitrogen content in the product derived from fusel oil is compatible for various segments of gasoline, including products that require low contents of impurities. The presence of these contaminants was not assessed in the cuts derived from 99% fossil IAA, since the raw material used in the tests was not the renewable raw material of interest.
Production of the isoamylene stream on a semi-industrial scale was carried out in a prototype FCC unit, equipped with an 18 m riser, adiabatic regenerator and adiabatic stripper. Table IV presents the operating conditions for obtaining the product. To supply the energy required for dehydration of IAA, torch oil was burned in the regenerator of the unit, maintaining the temperature of the regenerator at the specified value. The catalyst inventory of the prototype unit was 350 kg. Before the production tests, a stream of practically sulphur-free S10 diesel was processed, to purge the systems of condensation and guarantee sulphur content below 10 mg/kg for the stream. The IAA processed in the semi-industrial FCC unit was purified from fusel oil residue from distillation of sugar-cane ethanol (referred to as “bio-IAA”). The catalyst (Ecat 2), similar to the catalyst used in example 1, was supplied by a Petrobras refinery. The dehydration product was collected and separated from the water produced in a pressure vessel at 1 kgf/cm2, with the aid of a density sensor, which made it possible to monitor the water-naphtha interface during emptying of the vessel. The liquid product generated in the FCC unit was then fractionated in a distillation unit to generate the final stream. As it was a product derived from raw material of vegetable origin, the product became known as “bioisoamylene”.
Table V shows the data from characterization of the distillation cut generated after processing the bio-IAA 99%.
The product had characteristics similar to those of the products obtained in the pilot plant. Regarding volatility, bioisoamylene was found to be somewhat lighter than the product generated in the pilot plant, with higher RVP, resulting from the greater recovery of light components (compounds with 4 carbons) relative to the products from the pilot plant.
The final product had high calorific value and octane rating (RON>100 and LCV=44.8 MJ/kg), compatible with the values observed in the cuts produced in the pilot plant. Both properties are excellent, indicating that bioisoamylene is a suitable stream for use in special gasoline formulations.
iValue of IP for mixture of 10% w/w component/90% w/w alkylated product (IP alkylated product > 1.200 min)
iiCalculated from data on composition by GC
iiiNot determined. Sample very volatile, irregular combustion
ivRON value for mixture of 10% w/w component/90% w/w alkylated product (RON alkylated product = 98.5)
Regarding stability, the product had behaviour similar to that of the products of the pilot plant, and it was not necessary to use an antioxidant additive. Furthermore, it should be emphasized that the product was easier to produce, as post-treatment unit operations were not required to ensure stability.
Regarding the content of impurities (total N, total S and oxygen), very low values were observed, which did not cause any problem for meeting any current specification for all series of gasolines, including those with low sulphur content.
In general, the composition of the product, the physicochemical data for bioisoamylene (RVP, density, distillation, LCV and octane rating) and the data on stability indicated very good suitability of the product as a component of gasolines, since its use may provide all the properties required for the formulations.
In addition, some properties of bioisoamylene are significantly better than those observed for the naphthas obtained by petroleum refining, indicating that this hydrocarbon stream, consisting primarily of olefins with 5 carbon atoms, tends to contribute to the development of various special gasolines.
As may be deduced from the above examples, the process for dehydration of by-products from ethanol production from sugar cane based on FCC of the present disclosure results in a hydrocarbon stream with a high percentage of isoamylenes, high octane rating and energy content. The stability is compatible with the values observed for automotive gasolines and the content of sulphur and nitrogen-containing compounds is compatible for various gasoline segments. Therefore the product is suitable for various applications, such as development of products with better performance (aviation gasoline, premium gasolines, competition gasolines) or as an octane improver for automotive gasolines.
Numerous variations falling within the scope of protection of the present application are permitted. The present invention is not limited to the configurations/particular embodiments described above.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2017/053439 | 11/15/2017 | WO | 00 |
