CZ2007374A3 - Process for preparing olefins from renewable resources - Google Patents

Abstract

Production of olefin by catalytic transformation in the presence of hydrogen of suitable renewable raw materials on a n-alkane mixture which are further pyrolyzed in the presence of water vapor to the desired olefins. Renewable raw materials are vegetable oils, vegetable fats, animal fats and rendered fats, even when used. Preferably, either the liquid phase or the hydrocarbon fraction or only propane is isolated from the downstream pyrolysis mixture. Preferably, from 1 to 99% by weight of the isolated parts of the mixture, i.e. the liquid phase, the hydrocarbon fraction or the propane, are added. petroleum raw materials. Preferably, the pyrolysis hydrogen is used for the catalytic conversion of renewable raw materials.

Description

Method of production of olefins from renewable sources

Technical field

The invention relates to a process for producing olefins from renewable sources, in particular biomass, also called bioolefins.

BACKGROUND OF THE INVENTION

Currently, there is growing pressure on the use of renewable energy sources. While the production of motor fuels from renewable raw materials is carried out in practice and is widely described in both scientific and patent literature, the production of olefins from these sources has not been described yet.

Biomass is an important source of alternative raw materials for the production of fuels and chemicals. By converting it, it is possible to obtain either suitable chemical intermediates or at least suitable chemical raw materials. Plant oils and animal fats are important raw materials of plant and animal origin, which are to some extent similar to petroleum fractions from a chemical point of view. They are essentially mixtures of triglycerides, i.e., triglycerides of fatty acids, which are characterized by long chains with a hydrocarbon structure having a high atomic H / C ratio.

Until now, ethylene has been produced exclusively by pyrolysis of petroleum hydrocarbon fractions in the presence of water vapor. The main raw materials used were liquefied gases, primary gasoline, atmospheric gas oil and vacuum residue from the hydrocracking of the vacuum distillate, the so-called hydrocrackate. Hydrocarbon fractions with a high atomic H / C ratio are considered to be the optimum feedstock for ethylene production. Liquefied gases and naphtha are best suited to this requirement. The use of atmospheric gas oil or hydrocracking vacuum residue is forced by the lack of more advantageous lighter raw materials.

The most preferred pyrolysis feedstock is n-alkanes since they best meet the above requirement for a high atomic H / C ratio and provide a product with a relatively higher olefin content and a lower aromatic hydrocarbon content. Isoalkanes also behave similarly to n-alkanes, which also provide a relatively high yield of propylene. Less preferred feedstocks are olefins which are prone to the formation of condensation products and high molecular weight pyrolysis products.

The least suitable raw materials are aromatic hydrocarbons whose aromatic rings are highly stabilized and therefore do not cleave into light olefins during pyrolysis. Aromatic hydrocarbons primarily provide condensed products and / or coke. An exception is the long-chain aliphatic aromatic hydrocarbons, where the olefin source is precisely this chain. The second major product of industrial pyrolysis in pyrolysis units with an annual production capacity of up to several hundred thousand tons of ethylene is propylene. The average yield of ethylene without recycling is 25 to 27% by weight, the average yield of propylene is approximately 15% by weight.

The above mentioned raw materials of biological origin can also be used for the production of motor fuels. US 2004/0230085 A1 describes a process for producing hydrocarbons from raw materials of biological origin. The hydrocarbons produced are identified as suitable components for the production of diesel. This process consists of two basic steps; in the first, hydrodeoxygenation is carried out in which the oxygen present in the raw materials of biological origin is removed and hydrocarbons are obtained which are isomerized in the second step on the isomerization catalyst. The product is a mixture of branched hydrocarbons - isoalkanes. The disadvantage of this process is that n-alkanes are isomerized to isoalkanes and that the reaction products need to be separated.

US 2004/0055209 A1 and WO 2004/022674 A1 define the fuel composition for diesel engines. The fuel blending components are obtained from raw materials of biological origin, in particular vegetable oils, animal and fish fats and mixtures thereof. The proportion of these components in the resulting diesel fuel is in the range of 0.1 to 80% by weight.

The hydrocarbons can be obtained according to GB 1524781 A1 by thermal cleavage of vegetable oils. This cleavage takes place at temperatures of 300 to 700 ° C in the presence of a catalyst which is silica-alumina mixed with a transition metal oxide. The process is carried out at atmospheric pressure and involves separation and purification of the products. Its disadvantage is the necessity of separation and cleaning of products and undefined handling of by-products.

Catalytic cleavage of fatty acid triglycerides using a zeolite Y in admixture with Al2 O3, CoMo on Al2O3 or NiMo on Al2O3 is described in DE3340711 A1. The product is paraffinic hydrocarbons. The reaction temperatures and pressures are in the range of 300 to 600 ° C, respectively. 1 to 20 MPa. The disadvantage of this process is the relatively low yield of liquid n-alkanes (<60%) and the high consumption of hydrogen, which comes exclusively from an external source.

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EP 1489157 A1 describes a process for converting oil and fat-based raw materials and waste materials into high hydrocarbon mixtures. These products are obtained by exposure to a fixed bed of activated carbon at high temperatures ranging from 150 to 850 ° C. The unsaturated products may be further hydrogenated. The hydrocarbon-containing mixture obtained by the process described in the patent is useful as a fuel or fuel or for the production of chemicals. The disadvantage of this process is that it requires an external hydrogen source and that the product is a complex mixture of products that must be further purified and separated.

Pyrolysis (cracking of hydrocarbons in the presence of water vapor) of hydrogenated and hydrotreated petroleum hydrocarbon fractions that do not contain simene and nitrogen compounds is disclosed in US 6210561. Hydrogen refining reduces S contents below 100 ppm (parts per million) and N below 15 ppm. The aromatic hydrocarbons in the feedstock are hydrogenated on a catalyst containing Pt or Pd. Saturated and refined products are subsequently pyrolytically cleaved in the presence of water vapor. The yield of ethylene, propylene and butadiene from the refined feedstock will increase by about 2.5 wt. compared to the use of the original, unrefined raw material. The disadvantage of this process is that the feedstock used to produce olefins comes from a fossil non-renewable carbon source.

Pyrolysis of n-alkanes for the production of ethylene is described in U.S. Pat. No. 6,473,401. The feedstock is Cs CsCaž hydrocarbons from which a fraction with a high content of n-alkanes is isolated by adsorption. Adsorption separation is reported as a preferred method for isolating n-alkanes from mixtures with other hydrocarbons. Again, the disadvantage is that ethylene is obtained by cleaving the raw material of fossil origin.

Said drawbacks are at least partially eliminated by the process for producing olefins from renewable sources according to the invention.

SUMMARY OF THE INVENTION

Process for producing olefins from renewable sources, characterized in that at least one renewable feedstock is catalytically converted in the presence of hydrogen to a mixture of gaseous and liquid hydrocarbons, water, CO and CO 2 and then pyrolyzed in the presence of water vapor to olefins.

A preferred method for producing olefins from renewable sources, characterized in that the renewable raw materials are substances from the group comprising vegetable oils, vegetable fats, animal fats and rendered fats, even spent.

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Another preferred method for producing olefins from renewable sources, characterized in that the liquid phase is isolated from the mixture and then pyrolyzed.

Another preferred process for producing olefins from renewable sources, characterized in that hydrocarbon fractions are recovered from the mixture and pyrolyzed.

Another preferred process for producing olefins from renewable sources, characterized in that propane is recovered from the mixture, which is then pyrolyzed.

Another preferred process for the production of olefins from renewable sources, characterized in that 1 to 99 wt. petroleum raw materials.

Another preferred process for producing olefins from renewable sources, characterized in that the hydrogen produced by pyrolysis is used for catalytic conversion.

The invention solves the production of olefins from biomass. The production of the so-called bioolefins according to the invention involves the catalytic conversion of renewable raw materials containing triacylglycerides, most preferably vegetable oils and fats including vegetable and animal waste (preferably animal fats, rendered fats and spent vegetable oils and fats) in the presence of hydrogen to a hydrocarbon product. with a very high content of aliphatic hydrocarbons of n-alkanes (> 95% by weight) and propane.

The starting standard refined feedstock is fed from the reservoir together with the hydrogen to a heated fixed bed tubular reactor. If the raw material is vegetable oil, there is no need to heat the tank. If the raw material is animal fat, the tank and the feed path should be heated to a temperature of at least 80 ° C. The feedstock can also be injected only after it has been mixed with a suitable petroleum fraction. The reactor is heated to a temperature in the range of 150 to 450 ° C and the reaction pressure is maintained in the range of 1 to 20 MPa. The catalyst used is one of the transition metals, preferably Ni, Mo, Co and W and combinations thereof. These active ingredients are deposited on a carrier to achieve good dispersion. Alumina (Al 2 O 3) or aluminosilicates, either amorphous or zeolites or mesoporous molecular sieves, are used as the carrier. The catalyst load is characterized by WHSV (weight hourly space velocities) indicating the amount of raw material in kg processed per kg of catalyst per hour. The WHSV is usually in the range of 0.2 to 5 h ^-1 .

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After cooling, the products are readily separated into a liquid phase containing n-alkanes and water and a gas phase, the main components of which are propane, CO, CO2, CH4 and hydrogen. The liquid product is pyrolyzed in the presence of water vapor to produce olefins (ethylene > 40 wt%, propylene > 15 wt%) in high yield. Either the entire liquid fraction (n-alkanes + water) can be pyrolyzed without the need to dry the hydrocarbon fraction, or only the hydrocarbon fraction (n-alkanes). Each of these fractions can also be pyrolyzed in admixture with petroleum hydrocarbon fractions. The gaseous product is treated by fractional distillation together with conventional pyrolysis products. This separation yields hydrogen for hydrogenation, which is an advantage of the process of the invention, and propane, which is used as feed to the pyrolysis reactor. This means that propane, which is produced as a byproduct in the hydrotreating of raw materials from renewable sources of biological origin, is also recovered into ethylene and propylene. The separated hydrogen can be advantageously used in the catalytic hydrotreating of the above-mentioned renewable raw materials into hydrocarbons.

The treatment of hydrocarbon fractions obtained by refining renewable raw materials together with petroleum fractions, in particular atmospheric gas oil and hydrocrackate, not only leads to an increase in olefin yields, but also facilitates the processing of these fractions. The reason is to reduce the content of aromatics, which are contained in petroleum fractions, ^J their mixing with n-alkanes valkanické hydrocarbon fractions of renewable energy, which is another advantage of the present invention. Reducing the aroma content can be used in two ways: 1. by increasing the olefin yield while maintaining the energy performance; or 2. by reducing the energy intensity of the process while maintaining the olefin yield, for example by reducing the ratio of water vapor to hydrocarbon feedstock.

DETAILED DESCRIPTION OF THE INVENTION

Example:

Treatment of the renewable raw material - rapeseed oil - at a temperature of 320 ° C and a pressure of 7 MPa in the presence of a NIMO / Al 2 O 3 catalyst and hydrogen produced a mixture containing CO, CO 2, water, methane, propane and a mixture of n-alkanes predominantly 15-18 atoms of carbon in the molecule. No other waste products are produced in this process. The approximate composition of the mixture is summarized in Table 1.

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Table 1 - Composition of the mixture resulting from the catalytic treatment of rapeseed oil (wt%)

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Composition of the mixture Content n-alkanes 85 propane 5 CO, CO2, methane 7 water 6

By reducing the pressure in the outlet tank of the mixture from 7 MPa to atmospheric pressure, separation of the gaseous and liquid phases was achieved. By pyrolysis of a mixture containing liquid fractions, in particular C15-C18 n-alkanes and water, olefins, in particular ethylene and propylene, were obtained in high yield. The yields of pyrolysis products of this mixture are shown in Table 2. Pyrolysis was performed at 810 ° C. In particular, the yield of ethylene significantly exceeds the yields obtained by the cracking of conventional petroleum feedstocks. By way of comparison, the yield of ethylene in the pyrolysis of the most typical liquid feedstock, straight-run gasoline, is in the range of 25 to 27% by weight.

Table 2 - Yields of pyrolysis products of the mixture obtained by catalytic treatment of rapeseed oil, respectively. naphtha (% by weight)

Product Mixture Primary petrol Ethylene 48.3 26.1. Propylene 17.4 15.0 Butadiene 5.6 6.8 BTX 1.3 10.6 Other 21.9 35.7 Oils 5.5 5.8

Note: BTX is a fraction consisting of C 6 -C 8 aromatics.

As can be seen from Table 2, the yields of ethylene and propylene obtained by pyrolysis of the blend are significantly higher than that of pyrolysis of straight-run gasoline. At the same time, the formation of undesirable waste products, especially pyrolysis oils, was reduced. Hydrogen, which is produced in the amount of about 1% by weight in the pyrolysis of hydrocarbons, is used as a raw material in the catalytic treatment of rapeseed oil.

Example 2:

The mixture produced by the processing of the renewable raw material, containing mainly C-C 18 n-alkanes and water, the production of which is described in Example 1, was poured into a separator where it was divided into two layers. The lower layer contained water and the upper, hydrocarbon layer contained n-alkanes

_{CI5-C] S.} After separation of the water, the hydrocarbon layer was pyrolyzed at 810 ° C. The yields of the pyrolysis products were identical to those shown in Table 2,

Example 3:

Catalytic treatment of the rapeseed oil described in Example 1 also yielded propane in a yield of 5% by weight. (see Table 1). This by-product was pyrolyzed at 810 ° C. The yields of the products obtained are shown in Table 3. It is apparent from the results that propane also provides high yields of olefins, in particular ethylene and propylene, during pyrolysis.

Table 3 - Yields of pyrolysis products of propane obtained by catalytic treatment of rapeseed oil (% by weight)

Product Yield Ethylene 43.7 Propylene 21.2 Butadiene 4.1 BTX 4.8 Other 26.1 Oils 0.1

Example 4;

The hydrocarbon fraction containing n-alkanes, prepared as described in Example 1, was mixed with one of the standard pyrolysis feedstocks - a vacuum residue from the vacuum distillate hydrocracking process (hydrocrackate, HCVD) in a 1: 9 by volume ratio. the mixture was pyrolyzed at 810 ° C. The yields of the individual products obtained are shown in Table 4 together with the yields of the products obtained by pyrolysis of HCVD alone carried out under the same conditions. It can be seen from Table 4 that the addition of the hydrocarbon fraction produced according to Example 1 to the vacuum residue from the hydrocracking of the vacuum distillate greatly increases the yield of ethylene and propylene. The increase in yield of these olefins is greater than would correspond to a mere additive increase. The addition of the hydrocarbon fraction produced according to Example 1 to HCVD also has the advantage of reducing the aromatic content of the resulting mixture and thereby reducing the formation of coke by pyrolysis.

Table 4-Yields of hydrocrackate pyrolysis products (HCVD) and HCVD with a liquid hydrocarbon fraction (9: 1 by volume) obtained by catalytic treatment of rapeseed oil (% by weight)

Product HCVD Mixture of HCVD with n-alkanes Ethylene 28.2 35.2 Propylene 14.5 15.8 Butadiene 7.3 6.6 BTX 8.3. 6.4 Other 28.1 26.1 Oils 13.6 9.9 /

Industrial applicability

The invention is industrially applicable in the production of alkane fractions from renewable sources and their subsequent pyrolysis to olefins, in particular ethylene and propylene.

Claims (7)

Process for producing olefins from renewable sources, characterized in that at least one renewable feedstock is catalytically converted in the presence of hydrogen into a mixture of gaseous and liquid hydrocarbons, water, CO and CO ₂ and then pyrolyzed in the presence of water vapor to olefins. Process for producing olefins from renewable sources according to claim 1, characterized in that the renewable raw materials are substances from the group comprising vegetable oils, vegetable fats, animal fats and rendered fats, even spent. 3. A process for producing olefins from renewable sources according to claim 1, characterized in that the liquid phase is isolated from the mixture, which is then pyrolyzed. A process for producing olefins from renewable sources according to claim 1, characterized in that hydrocarbon fractions are isolated from the mixture, which are then pyrolyzed. Process for the production of olefins from renewable sources according to claim 1, characterized in that propane is isolated from the mixtures, which is then pyrolyzed. Process for producing olefins from renewable sources according to claim 3 or 4 or 5, characterized in that 1 to 99 wt. petroleum raw materials. Method for producing olefins from renewable sources according to claim 1, characterized in that the hydrogen produced by pyrolysis is used for catalytic conversion.