RU2379103C1 - Sorbent, method of preparing said sorbent and method of drying hydrocarbons - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to drying hydrocarbons through sorption and can be used in oil refining and petrochemical industries. A calcium chloride based sorbent is proposed, which is placed in pores of a solid body - matrix, which is a composition of aluminium, calcium and boron oxides, with the following content of components of the sorbent, wt %: AI₂O₃ - 50-80; B₂O₃ -5-30; CaO - 10-11; CaCl₂ - 5-30, with total concentration of Broensted and Lewis acid sites on the surface of the sorbent of not more than 7 mcmol/g. The sorbent for drying hydrocarbons is obtained by simultaneously mixing a hydrate of aluminium oxide with pseudo-boehmite structure with orthoboric acid and calcium chloride, granulation, drying and calcination. The method of drying hydrocarbons involves bringing hydrocarbons into contact with the proposed sorbent at temperature 0-40°C and regeneration of the sorbent at temperature 150-200°C in the current of a gas consisting of C₁-C₄ hydrocarbons, hydrogen, nitrogen.

EFFECT: invention enables efficient drying of hydrocarbons, particularly pyrolysis gas; the sorbent is characterised by high stability of drying properties during repeated use in drying-regeneration cycles.

3 cl

Description

The invention relates to the field of sorption technologies for the drying of hydrocarbons, namely to sorbents based on calcium chloride, their production and use in the processes of the oil refining and petrochemical industries.

Drying refers to the important stages in the implementation of various industrial processes for the synthesis and processing of hydrocarbons. Moreover, in a number of cases, a specific feature of drained flows is the presence of readily polymerizable components in them. The latter poses a problem of the selection and use of appropriate sorbents, the solution of which requires a compromise combination of indicators such as drying depth, water capacity, catalytic activity, regenerability, and the overall service life of the sorbent.

Sorption technologies for the drying of hydrocarbons are mainly based on the use of solid porous materials, the most widely used of which are various silica gels, aluminum oxides, and synthetic zeolites (N.V. Keltsev. Fundamentals of adsorption technology. 2nd ed., Revised and additional - M .: Chemistry, 1984. - 592 p.). For the drying of hydrocarbons, it is also known to use composite sorbents, which are hygroscopic inorganic salts located on a porous support (patents RU 2169606, 2244588). At the same time, composite sorbents are characterized by the greatest moisture capacity. A common drawback of all these sorbents during the drying of hydrocarbons is their catalytic activity, due to the presence of the Brandsted (BCC) and Lewis (LCC) acid centers. The latter cause the conversion of hydrocarbons during the drying process, which leads to loss of components of the drained streams, coking of the sorbents during thermal regeneration, premature loss of sorption and mechanical properties by them, and shortening of the overall service life.

The closest technical solution to the proposed is a composite desiccant of gases and liquids, a method for its production and a method of drying with its use (patent RU 2169606, prototype). The composite desiccant consists of a porous matrix and an active moisture-absorbing substance placed in the pores of the matrix. Solutions of halides, sulfates, nitrates of alkali and alkaline earth metals and their mixtures are used as active moisture-absorbing substances, and inorganic oxides, porous coals, natural sorbents, porous metals, porous composites, or mixtures thereof are used as a porous matrix. The disadvantage of the prototype is that the composite desiccant retains acid sites and catalytic activity in the hydrocarbon conversions inherent in the porous matrix used for its preparation, which characterizes the insufficient stability of the sorbent. First of all, this concerns matrices based on inorganic oxides and natural sorbents, mainly of aluminosilicate nature. Chemically inert matrices based on porous carbon materials are characterized by an increased ability to absorb hydrocarbons; they can have low mechanical properties or high cost.

The main objective of this invention is the development of a new sorbent for drying hydrocarbons with increased stability of drying properties during repeated use in drying-regeneration cycles and the possibility of obtaining from available inorganic raw materials.

As a solution to this problem, a sorbent based on calcium chloride located in the pores of a solid body — a matrix, which is a composition of aluminum, calcium and boron oxides, with the following content of sorbent components, wt.%: Al ₂ O ₃ - 50-80; In ₂ O ₃ - 5-30; CaO - 10-11; CaCl ₂ - 5-30. The total concentration of the Brandsted and Lewis acid centers on the surface of the sorbent is not more than 7 μmol / g.

A method of producing a sorbent for drying hydrocarbons involves the simultaneous mixing of alumina hydrate of a pseudoboehmite structure with orthoboric acid and calcium chloride, molding into granules, drying and calcining the dried granules at a temperature of 500-700 ° C to obtain a sorbent having the following composition, wt.%: Al ₂ O ₃ - 50-80; In ₂ O ₃ - 5-30; CaO - 10-11; CaCl ₂ - 5-30.

The method of drying hydrocarbons involves contacting the hydrocarbons with the proposed sorbent at a temperature of 0-40 ° C and regenerating the sorbent at a temperature of 150-200 ° C in a stream of gas consisting of C ₁ -C ₄ hydrocarbons, hydrogen, nitrogen.

The chemical composition of the sorbent is determined according to atomic emission analysis. The content of free calcium chloride in the sorbent is additionally controlled by the weight loss of the sorbent as a result of its prolonged washing with water. The total content of BCC and LCC in the sorbent is estimated by measuring pyridine adsorption by IR spectroscopy [E.A. Paukshtis. Infrared spectroscopy in heterogeneous acid-base catalysis. - Novosibirsk: Science. Sib. Department, 1992. - 255 p.]. The chemical composition of the sorbents (claimed and prototype), as well as the total concentration of BCC and LCC on their surface are presented in table 1.

Table 1 The composition of the sorbents, the total concentration of BCC and LCC on their surface Example Chemical composition, wt.% BCC + LCC, μmol / g Al ₂ O ₃ B ₂ O ₃ Cao CaCl ₂ one 69.14 5.33 10.12 15.41 7 2 (prototype) 82.55 0.00 0.00 17.45 twenty

The invention is illustrated by the following examples.

Example 1. The sorbent is obtained by mixing alumina hydrate of pseudoboehmite structure with orthoboric acid and calcium chloride, molding into granules, drying and calcining. Alumina hydrate of pseudoboehmite structure (70 wt.% Calculated on Al ₂ O ₃ ), orthoboric acid (5 wt.% Calculated on В ₂ O ₃ ) and 25 wt.% Calcium chloride are stirred at room temperature, formed, dried at 150 ° C and then calcined at 600 ° C. Get the sorbent in the form of cylindrical granules with a diameter of 3-4 mm

1.16 kg of sorbent is loaded into the adsorber (diameter - 0.03 m, length - 2.2 m) and regenerated at 200 ° C in a stream of methane-hydrogen fraction containing: hydrogen - 38.64 vol.%, Methane - 56.60 vol.%, ethylene - 0.70 vol.%, ethane - 0.02 vol.%, propylene - 1.75 vol.%, propane - 0.51 vol.%, butanes - 1.78 vol.%.

Pyrogas is used as a drained medium (hydrogen - 22.05 vol.%, Methane - 20.69 vol.%, Ethylene - 29.88 vol.%, Ethane - 16.78 vol.%, Propylene - 6.53 vol. %, propane - 3.37 vol.%, butenes, divinyl - 0.70 vol.%), obtained as a result of pyrolysis of hydrocarbon feedstocks. The temperature of the drying process of the pyrogas is 24 ° C, the pressure is 3.0 MPa, the feed rate of the pyrogas is 0.5 m ³ / h, the initial humidity of the pyrogas is 0.0217 kg / m ³ . The drying process of the pyrogas is carried out until the dew point temperature of the dried pyrogas is more than minus 60 ° C. The dynamic moisture capacity of the sorbent is estimated from the results of weighing the sorbent after drying and by calculation from a dynamic curve. The regeneration-drying cycle is repeated on the sorbent 20 times. The values of the dynamic moisture capacity of the sorbent achieved in each cycle are presented in table 2.

Example 2. Analogously to example 1, but the sorbent used is a sorbent according to the prototype, obtained by impregnating alumina with a solution of calcium chloride and drying at 200 ° C.

table 2 The effect of the number of regeneration-drying cycles on the dynamic moisture capacity of sorbents Cycle Dynamic moisture capacity, g / 100 g of sorbent Example 1 Example 2 (prototype) one 27.6 29.3 2 26.8 29.2 3 27.1 28.9 four 27.0 27.5 5 26,4 26.7 6 27.3 25.3 7 26.1 24.9 8 25.9 23.1 9 25.3 21.0 10 26.1 22.3 eleven 25.3 22.4 12 24.9 21.7 13 25.1 22.4 fourteen 24.7 22.5 fifteen 24.2 21.3 16 24.5 20.9 17 25.1 20,2 eighteen 24.9 20.1 19 24.7 19.6 twenty 24.2 20,4

The initial values of the dynamic moisture capacity of the developed sorbent and prototype are close (27.6 and 29.3 g / 100 g, respectively), which is associated with a similar content of calcium chloride in both materials (15.41 and 17.45 wt.%, Respectively). However, as can be seen from the data presented in table 1, the developed sorbent in comparison with the prototype is characterized by almost three times lower content of acid centers, which leads to the fact that during the multi-cycle tests during the drying of the pyrogas (table 2), the developed sorbent shows more stable and regenerable. Over twenty working cycles, the dynamic moisture capacity of the developed sorbent decreased by 3.4 g / 100 g and in the last cycle amounted to at least 24.2 g / 100 g. Under the same conditions, the dynamic moisture capacity of the prototype dropped by 8.9 g / 100 g and the last cycle was 20.4 g / 100 g.

Thus, in comparison with the prototype, the developed sorbent is characterized by increased stability of its drying properties during repeated use in the drying-regeneration cycles. To obtain the sorbent, as well as to obtain a prototype, it is possible to use available inorganic raw materials. The use of the developed sorbent for drying hydrocarbons, in particular pyrogas, as well as other media containing readily polymerizable components, will increase the duration and reliability of the operation of drying plants, and minimize the loss of drained components.

Claims (3)

1. Sorbent for drying hydrocarbons, containing calcium chloride, fixed in a matrix, characterized in that the matrix is a composition of oxides of aluminum, calcium and boron, with the following sorbent component content, wt.%: Al ₂ O ₃ - 50-80; In ₂ O ₃ - 5-30; CaO-10-11; CaCl ₂ - 5-30, and the total concentration of the Brandsted and Lewis acid centers on the surface of the sorbent is not more than 7 μmol / g. 2. A method of producing a sorbent for drying hydrocarbons, comprising producing a matrix, mixing it with calcium chloride and drying, characterized in that the pseudoboehmite structure alumina hydrate is simultaneously mixed with orthoboric acid and calcium chloride, formed into granules and calcined dried granules at a temperature of 500 -700 ° C to obtain a sorbent having the following composition, wt.%: Al ₂ About ₃ - 50-80; In ₂ O ₃ - 5-30; CaO - 10-11; CaCl ₂ - 5-30. 3. A method of drying hydrocarbons, including contacting hydrocarbons with a sorbent and regenerating the sorbent, characterized in that the drying is carried out on the sorbent according to claim 1 at a temperature of 0-40 ° C, the regeneration of the sorbent is carried out at a temperature of 150-200 ° C in a gas stream, consisting from hydrocarbons C ₁ -C ₄ , hydrogen, nitrogen.