RU2261241C1 - Carbon monoxide/hydrogen-based production of hydrocarbons - Google Patents

Abstract

FIELD: petrochemical processes.

SUBSTANCE: hydrocarbons are produced via contacting synthesis gas with catalytic composition consisting of mixture of iron-containing Fischer-Tropsch synthesis catalyst and acid component at elevated pressures and temperatures and specified iron-containing catalyst reduction conditions. Specifically, said iron component is a mixture of neodymium and cerium silicates at weight ratio between 1:9 and 9:1 and weight ratio of acid component to iron-containing catalyst ranges from 1:1 to 6:1.

EFFECT: increased selectivity and productivity of catalyst and reduced level of aromatic hydrocarbons in product.

3 cl, 1 tbl, 15 ex

Description

Technical field

The invention relates to organic chemistry, in particular to petrochemistry and, in particular, to a method for producing hydrocarbons from a mixture of CO, H ₂ and CO ₂ (hereinafter referred to as synthesis gas). As a catalyst, compositions of iron-containing Fischer-Tropsch synthesis catalysts with acidic components — crystalline aluminosilicates, rare-earth element silicates of neodymium, cerium, praseodymium — are used. The resulting hydrocarbon fractions used as motor gasoline and diesel fuel are characterized by a lower aromatic hydrocarbon content compared to hydrocarbons obtained from a mixture of carbon monoxide and hydrogen in the presence of known iron-containing Fischer-Tropsch synthesis catalysts.

A known method of producing C ₅₊ hydrocarbons from a gas containing H ₂ and CO by contacting the gas at a temperature of 180-250 ° C, a pressure of 15-20 atm and a volume ratio of H ₂ / CO equal to 1.1-1.8 with a catalyst containing cobalt and zirconium on a carrier selected from aluminosilicate or oxides of silicon, aluminum, titanium (RU 1833335, C 07 C 1/04, 1993) [1].

There is also a method of producing a cobalt-zirconium catalyst on Al ₂ O ₃ for the synthesis of C ₅₊ hydrocarbons from a gas containing H ₂ and CO, and used at a temperature of 150-350 ° C, a pressure of 10-70 atm and a volume ratio of H ₂ / CO equal to 1.0-2.3 (RU 1836146, 01 J 37/04, 21/04, 23/74, 1993) [2].

According to the data obtained, a mixture of H ₂ and CO on cobalt catalysts produces C ₅ hydrocarbons with a selectivity of 68-85 wt.% [1] to 87-91 wt.% [2] and a productivity of 100-108 g / l cat / h .

The main disadvantage of the above methods for producing liquid hydrocarbons from synthesis gas in the presence of cobalt catalysts is the low content of hydrocarbons of the structure in the reaction products and the high cost of the catalysts.

Therefore, methods have been developed for producing liquid hydrocarbons from synthesis gas in the Fischer-Tropsch process using iron-containing catalysts. Although the selectivity and performance of these catalysts is lower compared to cobalt, however, the liquid products obtained in the presence of these catalysts contain a significantly larger amount of hydrocarbons from the structure and, in addition, the cost of these catalysts is much lower than cobalt (RU 2180651 C1 11.01.2001 )

Closest to the present invention is a method for producing hydrocarbons from carbon monoxide and hydrogen, comprising contacting the synthesis gas in the reactor with a catalytic composition consisting of a mixture of an active iron-containing Fischer-Tropsch synthesis catalyst and an acid component, at elevated pressure and temperature and given conditions for the reduction of iron-containing the active component of the catalytic composition (RU 2204546 C1, 2002). A distinctive feature of which is that crystalline aluminosilicate or silicoaluminophosphate is used as the acid component, circulation of the gas stream after the reactor is used with a volume ratio of the amount of circulating gas to the initial synthesis gas equal to 1-1000, and the process is carried out at a pressure of 10-100 atm. a temperature of 220-400 ° C, a volumetric feed rate of the feed synthesis gas of 100-5000 h ^-1 , a molar ratio of H ₂ -CO equal to 1-3, and a volumetric content of CO ₂ in the gas stream at the inlet of the reactor 0.01-40 % As catalysts for Fischer-Tropsch synthesis, iron fused catalysts in oxidized or reduced form, promoted by oxides of aluminum, silicon, magnesium, potassium and calcium, are used. As the acid component of the catalyst, crystalline aluminosilicates with a ZSM-5 type B structure are used, as well as crystalline silicoaluminophosphates with a SAPO-5 structure. The catalyst composition contains 10-90% of an iron-containing Fischer-Tropsch synthesis catalyst and 10-90% of an acid component.

According to the prototype, the synthesis gas conversion products are gasoline fractions (C ₅ -C ₁₀ hydrocarbons), diesel fraction (C ₁₀ -C ₂₀ hydrocarbons), C ₂₁₊ solid paraffins and reaction water containing oxygen-containing compounds.

However, the prototype has an important drawback:

When using in the process of synthesis of hydrocarbons from carbon monoxide and hydrogen a catalytic composition, from a series presented in the patent, which gives the lowest content of aromatic hydrocarbons in the reaction products - 2.9 wt.% (Example 13 prototype), there is a decrease in the efficiency of the process, which is expressed in a decrease the yield of liquid hydrocarbons up to 105 g / nm ^{3 of} synthesis gas and the degree of utilization of carbon contained in the initial carbon monoxide up to 50 wt.%, in comparison with the performance of more efficient catalysts. However, it should be noted that for more effective catalytic compositions (example 8 of the prototype), characterized by a high yield of liquid hydrocarbons - 159 g / nm ³ and a degree of carbon utilization from the starting carbon monoxide equal to 78 wt.%, The content of aromatic hydrocarbons in the reaction products increases - 22.5 wt.%.

The value of this drawback is very significant. Considering the fact that modern requirements for motor fuels are aimed at reducing the content of aromatic hydrocarbons in their composition, and the main use of hydrocarbons obtained in this method is their use as motor fuels, a high content of aromatic hydrocarbons is undesirable.

The objective of the present invention is to develop and create a method for producing hydrocarbons from carbon monoxide and hydrogen, having improved performance.

As a result of solving this problem, it is possible to obtain technical results consisting in increasing the selectivity and productivity of the catalyst for liquid hydrocarbons while reducing the content of aromatic hydrocarbons in liquid products.

These technical results are achieved in that in a method for producing hydrocarbons from carbon monoxide and hydrogen, comprising contacting the synthesis gas in the reactor with a catalytic composition consisting of a mixture of an iron-containing Fischer-Tropsch synthesis catalyst and an acid component at elevated pressures and temperatures and given conditions for the reduction of iron-containing catalyst, a mixture of neodymium and cerium silicates in a weight ratio of iron-containing catalyst and acid is used as the acid component the component from 1 to 6 and the ratio of silicates of neodymium and cerium, wt.%:

neodymium silicate 10-90 cerium silicate 10-90

In addition, gas circulation is used after the reactor with a volume ratio of the amount of circulating gas to the source gas equal to 1-1000, and the process is carried out at a pressure of 10-100 atm, a temperature of 220-400 ° C, a volumetric feed rate of the synthesis gas of 100-5000 h ^-1 , the molar ratio of H ₂ / CO in the initial synthesis gas, equal to 1-3, and the volumetric content of CO ₂ in the gas stream at the inlet of the reactor is 0.01-40%.

Distinctive features of the invention are:

- for the catalytic conversion of synthesis gas to hydrocarbon products, mixtures of iron-containing Fischer-Tropsch synthesis catalysts in oxidized or reduced form, promoted with oxides of aluminum, silicon, alkaline or alkaline-earth metals, with an acid component - rare-earth silicates of neodymium and cerium are used as a catalyst in a mass ratio of iron-containing catalyst / acid component equal to 50/50 - 85/15.

The weight ratio of neodymium and cerium, which are part of the acid component of the catalyst, varies in the range (wt.%):

neodymium silicate - 10-90,

cerium silicate - 10-90.

The choice of catalyst for the conversion of synthesis gas to hydrocarbon products is based on the fact that of all Fischer-Tropsch synthesis catalysts, the most productive in the temperature range 220-400 ° C are fused iron catalysts. The combination of fused iron catalysts with acidic components leads to intensification of the synthesis of hydrocarbons from H ₂ , CO, and CO ₂ due to faster reactions of conversion of intermediate products of Fischer-Tropsch synthesis (alcohols, olefins) on the acid component to the target hydrocarbon products.

The choice of conditions for the process of synthesis of gasoline and diesel fractions from a gas containing H ₂ , CO and CO ₂ is due to the following factors. Increased pressure is necessary for deeper conversion of synthesis gas. The lower limit of the temperature range (220 ° C) is determined by the minimum activity of the catalyst, exceeding the upper temperature value (400 ° C) leads to rapid carbonization of the catalyst surface. The volumetric feed rate of the feed synthesis gas is determined by the activity of the catalyst used, at fixed pressure and temperature. The claimed value of the space velocity is optimal for obtaining gasoline and diesel fractions. The ratio between H ₂ and CO, as well as between CO and CO _2, is determined by the stoichiometry of the chemical reaction of hydrocarbon synthesis. For the formation of the “CH ₂ ” group of paraffin hydrocarbons per carbon atom, two hydrogen atoms are required, and the amount of bound “O” in the feedstock determines the hydrogen consumption for the formation of H ₂ O molecules. Based on theoretical assumptions, the experiments were carried out under conditions fairly close to stoichiometric ratio between carbon, oxygen and hydrogen atoms. The conditions for the reduction of the catalyst are determined experimentally.

An important role in achieving high selectivity and productivity of the catalytic composition for the synthesis of liquid hydrocarbons belongs to the circulation of the gas stream after separation of liquid products. The constant removal of water and liquid hydrocarbons from the contact gas prevents the poisoning of the surface of the iron catalyst with water vapor, significantly suppresses the reaction of carbon dioxide formation of the passive component in the Fischer-Tropsch reaction and reduces the cracking of the formed liquid hydrocarbons on the acid component. During recycling, light olefins and intermediate oxygen-containing products are repeatedly contacted with the catalyst and converted into the target products.

Method implementation examples

Examples of the method for producing hydrocarbons from carbon monoxide and hydrogen are presented in table 1 (examples 3-15).

In examples 3-8, a catalytic composition was used consisting of a fused iron catalyst and an acid component of a mixture of neodymium and cerium silicates with a weight ratio (wt.%) Of 50/50 and an acid component (wt.%) Of 15-50.

In examples 9-11, a catalytic composition was used with an acid component (wt.%) - 30, the weight ratio of neodymium and cerium silicates included in the acid component varied in the range (wt.%):

neodymium silicate - 10-90,

cerium silicate - 10-90.

In examples 12-15, the content of the acid component in the fatty acids was (wt.%) - 30, and the ratio of silicates of neodymium and cerium 50/50.

Example 1 (prototype).

50 cm ³ fractions of 0.25-0.5 mm of fused iron catalyst (FFA) and granular (30 wt.% Al ₂ O ₃ ) ZSM-5 zeolite in a weight ratio of 33/67 are loaded into the reactor. The initial synthesis gas is fed into the reactor block for mixing with the gas circulating in the block. The reactor block consists of a heated reactor, a condenser refrigerator, a high and low pressure separator, an intermediate collector of liquid products, and an electromagnetic pump for gas circulation. Before synthesis, the catalyst is subjected to synthesis gas reduction under the following conditions: pressure of 10 atm, temperature of 350 ° C, duration of 24 hours. Then, the pressure is raised to 30 atm and catalyst recovery is continued at a temperature of 350 ° C for 8 hours. After recovery, a catalyst development process is carried out at a temperature of 300 ° C for 20 hours. The process of hydrocarbon synthesis is conducted at a pressure of 30 atm and a temperature of 280 ° C. To prevent the accumulation of condensed products in the reactor block, part of the circulating gas is constantly removed from the block after the high-pressure separator. Liquid products (hydrocarbons and water), gas discharged from the reactor block and gaseous hydrocarbons released during throttling are analyzed chromatographically. The process conditions and key indicators are shown in table 1.

Example 2 (prototype).

The conditions of the experiment are shown in table 1. Similar to example 1 with the exception of:

- the composition of the catalyst was changed, in which type B zeolite (SiO ₂ / Al ₂ O ₃ = 75) was used as the acid component,

- mass ratio of fused iron catalyst to acid component 70/30,

- the frequency of circulation increased to 600,

- space velocity is reduced to 700 h ^-1 .

The presented results of the experiments were taken from examples of the prototype, characterized by the lowest content of aromatic hydrocarbons in the resulting liquid products. The aromatic hydrocarbon content is 11.9 wt.% And 2.9 wt.% For example 1 and 2. The output of liquid hydrocarbons 148 and 105 g / nm ^{3 of the} original synthesis gas, the degree of use of "carbon" contained in carbon monoxide , 72 and 50% respectively. Achieving a higher yield of liquid hydrocarbons and the degree of use of "carbon" contained in carbon monoxide, characterizing the efficiency of the process according to the data presented in the prototype, lead to an increase in the content of aromatic hydrocarbons in the resulting liquid hydrocarbons.

The latter is undesirable, since the obtained liquid hydrocarbons used as motor fuels, in accordance with European and world standards, should be characterized by a low aromatic content.

Example 3. It is similar to example 2 except that it uses a catalyst consisting of a fused iron catalyst and an acid component, which is a mixture of silicates of neodymium and cerium, in a weight ratio of 50:50.

The results obtained are characterized by a low content of aromatic hydrocarbons in the resulting liquid hydrocarbons - 3.0 wt.%. Moreover, the yield of liquid products exceeds the performance achieved in the prototype (by 28% for example 1 and 71% for example 2).

Example 4. Similar to example 3 except for the weight ratio of the amount of calcined catalyst and acid catalyst, which is 50/50.

Example 5. Similar to example 4 except for the weight ratio of the amount of calcined iron catalyst and the acid component, which is 85/15.

Example 6. Similar to example 3 except that in this experiment the working pressure of the process was increased to 50 atm.

Example 7. Similar to example 3 except that in this experiment increased to 1000 h ^{-1 the} volumetric rate of the process.

Example 8. Similar to example 3 except that the volumetric rate of the process is reduced to 500 h ^-1 .

Example 9. Similar to example 3 except that as the acid component was used a mixture of silicates of neodymium and cerium with a weight ratio, wt.%:

neodymium silicate - 10,

cerium silicate - 90.

Example 10. Similar to example 3 except that the acid component used was a mixture of silicates of neodymium and cerium with a weight ratio, wt.%:

neodymium silicate - 30,

cerium silicate - 70.

Example 11. Similar to example 3 except that as the acid component was used a mixture of silicates of neodymium and cerium with a weight ratio, wt.%:

neodymium silicate - 90,

cerium silicate - 10.

Example 12. Similar to example 3 except that the pressure in the reaction system is 10 atm.

Example 13. Similar to example 3 except that the process temperature is 400 ° C.

Example 14. Similar to example 3 except that the volumetric rate of the process is 100 h ^-1 .

Example 15. Similar to example 3 except that the volumetric content of CO ₂ in the gas stream at the inlet to the reactor is 4.0%.

As can be seen from the results presented in table 1, the proposed method allows to obtain liquid hydrocarbons and has advantages compared with the prototype:

- reduced aromatic hydrocarbon content in the resulting liquid products,

- while the yield of liquid hydrocarbons and the degree of use of "carbon" carbon monoxide exceeds these prototypes.

Claims (3)

1. A method of producing hydrocarbons from carbon monoxide and hydrogen, comprising contacting the synthesis gas with a catalytic composition consisting of a mixture of an iron-containing Fischer-Tropsch synthesis catalyst and an acid component at elevated pressures and temperature and given conditions for the reduction of the iron-containing catalyst, characterized in that as the acid component use a mixture of silicates of neodymium and cerium in a weight ratio of acid component and iron-containing catalyst from 1 to 6 and the content of s ikat neodymium and cerium, wt.%: Neodymium Silicate 10-90 Silicate Cerium 10-90 2. The method according to claim 1, characterized in that the circulation of the gas stream after the reactor with a volume ratio of the amount of circulating gas to the source gas equal to 1-1000 is used. 3. The method according to claim 1 or 2, characterized in that the process is carried out at a pressure of 10-100 atm, a temperature of 220-240 ° C, a volumetric feed rate of the original synthesis gas of 100-5000 h ^-1 , a molar ratio of N ₂ / CO in the initial synthesis gas equal to 1-3, and the volumetric content of CO ₂ in the gas stream at the inlet to the reactor of 0.01-40%.