CS275924B6 - Process for preparing low-molecular alkenes by co-pyrolysis of crude oil fractions with waste polyalkenes - Google Patents

Abstract

A method of producing low molecular weight alkenes by copyrolysis petroleum fractions with polyalkene waste

Description

The invention relates to a process for the production of low molecular weight alkenes by copyrolysis of petroleum fractions! with waste polyalkenes.

Hitherto, low molecular weight alkenes such as ethylene, propene, butenes, 1,3-butadiene, isoprep and cyclopentadiene have been largely obtained from the products of medium-temperature pyrolysis of hydrocarbon gases and naphtha. A characteristic feature of current global developments is the rational saving of oil as the most valuable carbonaceous raw material. In addition, it is necessary to use alternative sources energetically as well as chemically. We mention the use of non-petroleum raw materials for the production of alkenes and BTX aromatics not because they would currently have a significant industrial position, but because some of them will certainly become so in the future. Three primary types of non-petroleum raw materials come into consideration: fossil carbon materials other than oil and natural gas, biomass (mainly cellulose) and hydrocarbon-type plastic waste. Fossil materials include oil sands, natural asphalts (rare and not considered for chemical pyrolysis), bituminous shale and, of course, coal, lignite and peat. Biomass represents municipal and agricultural waste and potentially wood raw material. Waste from polyalkenes (polyolefins), polyethylene, polypropylene and rubbers is available in sufficient quantities from plastics. Each of these materials can be pyrolyzed in different ways to give a gaseous, liquid and solid product (semi-coke and coke). For some raw materials, the carbon present is completely gasified, especially during flash heating.

At present, more and more attention is being paid to the use of by-products and industrial waste materials. One of the by-products that results from the stereospecific polymerization of propene to crystalline polypropylene is amorphous polypropylene. Another industrial waste generated in the production of polyethylene is low molecular weight polyethylene.

Amorphous polypropylene (atactic polypropylene and stereoblocks) has the appearance of an elastomer comparable to unvulcanized rubber. It does not have a characteristic melting point, its behavior is determined by the soaking point. In chemical properties, atactic polypropylene resembles a branched structure with an alkane (paraffin). It is stable to acids, alkalis and reducing agents. Only against strong oxidizing agents is it not stable. Water and other low molecular weight polar solvents do not dissolve amorphous polypropylene. A portion of the amorphous polypropylene (atactic polypropylene) is dissolved in aliphatic hydrocarbons.

Important properties of polyethylene include weight and crystallinity. The molecular weight of polyethylene determines whether the polymer will behave as petrolatum, wax or plastic. As a plastic, polyethylene behaves only from a molecular weight of 10,000 to 15,000 upwards. Crystallinity has a determining effect on the properties of polyethylene with a molecular weight of less than 10,000. Low molecular weight polyethylene can be Vaseline or wax, depending on the crystallinity. The molecular weight determines in particular the flow properties of the polymer, which are important in the processing technology (Gašperík J. et al .: Technology of Plastics, ES SVŠT (scripts), p. 15 (1977); Kamenár S., Beniska J., Hrivník A. : Production of polymers, ES SVŽT (scripts) (1989)).

Due to its unsatisfactory properties, amorphous polypropylene has no direct technological use. One of the possibilities is the production of waterproof paper by painting. Another suitable application is the use in adhesives (Przem. Chem, 51 (12), 781, (1972)). Amorphous polypropylene can be used to impregnate glass fibers as a raw material for rubber admixtures and as a modifier for paraffins and waxes. In the field of lubricants, it is recommended as an additive for lubricating oils, increasing the viscosity index and improving the oxidative stability of oils. Amorphous po

CS 275924 Polypropylene with a molecular weight above 1000 can be part of floor coverings produced on the basis of butadiene-styrene rubber. In construction, it can be used in a mixture with asphalt for the construction of roads, roofing and as sound insulation. Chlorinated amorphous polypropylene with a chlorine content of over 60% in a mixture with alkyd or other resins and plasticizers It is suitable for the production of permanent coatings for the protection of metals and concrete structures.

Few methods are known for the treatment of plastic waste, used rubber and other organic wastes which are hungry, have no detrimental effect on the environment, are widely used and are cost-effective. So far, incineration is the most common and widespread method of treating organic waste. However, it has several disadvantages. High investment price, risk of environmental pollution, average production values and the need to incinerate the same types of waste or selected waste fractions. Based on research that began 10 years ago, pyrolysis processes have become widespread. However, they require certain technical and economic conditions, but on the other hand they bring considerable benefits. The amount and composition of the products formed in the pyrolysis of plastic waste depends mainly on the composition of the waste (type of plastic substance), on the temperature and method of pyrolysis, on the reaction time and the extent of the secondary reactions. The gas yield is in the range of 5 to 30% by weight. Methane has a dominant position in pyrolysis gases. The gas is most often used energetically to delay the pyrolysis temperature, or to produce steam. The yield of the liquid product varies between 15 and 90% by weight. The pyrolysis liquid is aromatic in nature and in most cases is used as a sulfur-free heating oil (Kerényi E .: Mage. Kem. Lapja, 33, 298 (1978); Collin H .: International Recycling Congress CRE / MER 1-3.10.1979, Berlin). This was also the case for the pyrolysis of atactic polypropylene on fluidized sand. A portion of the atactic polypropylene was oxidized, thereby maintaining the temperature at 400-600 ° C (Hiroku Nishiraki et al .: J. Chem. Soc. Japan, Chem. And Industrial Chem (12), 1899 (1977)).

From the foregoing, it is clear that the use of amorphous polypropylene is wide, but its production far exceeds the use in said applications. At present, large quantities are still exported to landfills. Therefore, it is necessary to look for more possibilities for the use of these polymerization by-products.

The above drawbacks are eliminated by the process for the production of low molecular weight alkenes in the temperature range 600 to 900 ° C, preferably 750 to 850 ° C in the presence of water vapor, the essence of which consists in subjecting pyrolysis to gasoline, kerosene, gas oil obtained from physically. chemical treatment of petroleum and from cleavage processes in the presence of polyalkenes, preferably low molecular weight polyethylene and amorphous polypropylene in an amount of 3 to 50% by weight, preferably 5 to 30% by weight on the starting material. raw material.

The invention makes progress in that waste polyalkenes, in particular low molecular weight polyethylene and amorphous polypropylene, are recovered by copyrolysis with petroleum fractions! for low molecular weight alkenes and aromatics. At the same time, not only is a certain part of the valuable starting oil raw materials replaced by hungrier polyalkenes, but under copyrolysis conditions they are applied! decomposition reactions which lead to increased yields of the desired alkenes, for example ethylenes. Increased ethylene yields can be obtained without the need to increase the outlet and reactor temperatures excessively. Another benefit of the process according to the invention is that during the copyrolysis of petroleum fractions with polyalkenes secondary reactions are carried out to a lesser extent, as a result of which less coke is formed on the inner surface of the pyrolysis reactor and on the heat exchange surfaces of cooling units, especially TLE. This will allow the use of the time pool of pyrolysis furnaces to be extended.

CS 275924 Βδ

The subject matter of the invention is elucidated on the basis of exemplary embodiments without referring only to said examples.

Example 1

The starting materials, which include primary petroleum fractions, amorphous polypropylene and low molecular weight polyethylene, were obtained from n.p. Slovnaft Bratislava. The average basic properties of amorphous polypropylene are as follows:

Content of atactic share 80 up to 90% by weight Stereoblock content 10 up to 20 wt. Ί Molecular weight (viscometric) 10 000 to 40 000 g.mol Ash content 0.02% by weight Water content ' 10 up to 30 wt. Impact point (KG) 130 up to 140 ° C Density 860 . -3 kg. m Evaluation of amorphous polypropylene by NMR is as follow:

Group -CH 39.7%

Group -CH ₂ 21.9%

Group -CH ^ 38.4%

Before proceeding with the pyrolysis of the amorphous polypropylene itself, it was necessary to find a suitable system in which the polymer is soluble. Initially, aliphatic hydrocarbons such as heptane and hexane were monitored. Amorphous polypropylene did not dissolve completely even at the boiling point of these hydrocarbons. Amorphous polypropylene also did not completely dissolve in aromatic solvents (toluene, benzene, xylenes). Chlorinated hydrocarbons (chloroform, trichloromethane, dichloromethane) were also not suitable solvents. The best results were given by decalin, but only at a temperature of 135 ° C. We also tested the following petroleum fractions: hydrogenated gasoline, heavy gasoline, gasoline raffinate, kerosene (PL-4), (PS), (PL-6) and gas oil. Amorphous polypropylene dissolved better in said petroleum fractions than in individual hydrocarbons. Transparent solutions were obtained in kerosene and gas oil when heated to 70-80 ° C. Upon cooling to room temperature, no amorphous polypropylene settled, although the solution was not true.

Low molecular weight polyethylene is a waxy substance with a certain content of oily substances with a melting point above 100 ° C. Both low molecular weight polyethylene and amorphous polypropylene are in the form of a solid at room temperature. Good solubility of low molecular weight polyethylene in naphtha was obtained after previous heat treatment of this raw material in a water bath. In the case of a mixture with 5 to 10% of low molecular weight polyethylene in naphtha, a white suspension was formed which did not change significantly even after cooling to room temperature. Mixtures of .5 and 10% amorphous polypropylene in naphtha were prepared by dissolving it without heating. The required amount of amorphous polypropylene, which has the appearance of an elastomer, was added to the naphtha in small portions with constant stirring. There was no complete dissolution, the resulting mixture contained, in addition to small particles of insoluble amorphous polypropylene, also mechanical impurities and water, which after a certain time sedimented to the bottom of the vessel. Also in this case, we heated the mixture before entering the preheating of the pyrolysis plant.

It was used for the copyrolysis of low molecular weight polyethylene and amorphous polypropylene

naphtha with the following characteristics: Composition (% by weight) - straight chain alkanes 24.9 - branched alkanes 55.2 - cycloalkanes 13.2 - aromas 6.7 Average molecular weight: 128 g.mol ” ¹ Density 705 kg.m ¹ Distillation range 64-167 ° C

Primary kerosene had the following properties:

Density Molar mass 0.7999 g.cm 167 g.mole ¹ Sulfur content 0.20% by weight Aromatic content 20.1% by weight Distillation range 162-242 °

Basic characteristics of gas oil:

Density Molar mass 0.8519 g.cm ”269 g.mole” ¹ Sulfur content 0.89 wt. Aromatic content 24.5% by weight Distillation range 245-360 ° C

Example 2

Copyrolysis of the reactor gasoline in the temperature range 700 with pelyalkenes takes place in a flow tube up to 950 ° C. The pressure ranges from 0.05 to 0.5 MPa and the residence time is less than 0.5 seconds. The reaction is carried out in the presence of water vapor in an amount of 20 to 150% by weight per hydrocarbon feed. The results of pyrolysis of naphtha alone and its copyrolysis with low molecular weight polyethylene are shown in Table 1.

Table 1. Copyrolysis of naphtha with low molecular weight polyethylene

Temperature, ° C 820 The ratio of water to raw material ' about. , 5 Raw material flow, gh ^-1 40.0 20.2 29.9 20.0 30.1 20.0 Amount of low molecular weight polyethylene,% wt. - - 5 5 10 10 Dwell time, p 0.076 0Í157 0.112 0.147 0.101 0.133 Amount of pyropas,% wt. 75.7 79.1 71.2 76.4 64.9 76.1 Product yields in% wt. Hydrogen 0.9 1.1 0.8 1.1 0.8 1.1 Methane 10.6 15.5 13.4 20.1 12.8 15.3 Ethane 2.8 4.5 3.5 3.8 4.2 3.8 Ethylene 25.5 30.4 25.2 31.5 24.2 31.8 Overdone 16.5 13.2 13.8 10.0 10.2 11.3 1,3-Butadiene 5.9 4.9 4.8 3.9 3.7 4.4 After all, pyrolysis products 37.8 30.4 38.5 29.6 44.1 32.3

(gaseous and liquid)

The results obtained from the copyrolysis of naphtha with amorphous polypropylene are shown in Table 2.

Table 2. Copyrolysis of naphtha with amorphous polypropylene Temperature, ° C 820 The ratio of water to raw material 0.5 Raw material flow, g.h 40.0 20.2 39.8 20.0 40.1 20.0 Amount of amorphous polypropylene,% by weight, . - - 5 5 10 10 Dwell time, p 0.076 0.157 0.081 0.143 0.081 0.146 Amount of pyropas,% wt. 75.7 79.1 72.8 77.9 59.2 67.4 Product yields in% wt. Hydrogen ¹ 0.9 1.1 0.6 0.9 0.8 0.7 Methane 10.6 15.5 9.5 16.5 9.4 14.5 Ethane 2.8 4.5 3.0 3.6 5.5 5.7 Ethylene 25.5 30.4 26.2 32.3 21.9 28.2 Propene 16.5 13.2 16.3 10.2 11.7 10.9 1,3-Butadiene 5.9 4.9 5.6 4.3 5.5 5.5 Other pyrolysis products (gaseous and liquid) 37.8 30.4 38.8 32.2 49.4 38.9

Example 3

Copyrolysis of primary kerosene, the properties of which are given in Example 1, was carried out under the conditions given in Example 2. The results of the copyrolysis of kerosene with low molecular weight polyethylene are shown in Table 3.

Table 3, Copyrolysis of primary kerosene with low molecular weight polyethylene (composition of products in% by weight)

Temperature, ° C The ratio of water to raw material Amount of low molecular weight polyethylene, Retention time, p Amount of pyropas, wt. 800 % wt. 0.75 0.130 51.13 5 0.131 52.03 Product yields in% wt. Methane 12.16 13.52 Ethane 3.18 3.06 Ethylene 19.52 21.17 Prop 9.20 13.62 1,3-Butadiene 3.01 5.57 Other pyrolysis products (gaseous and liquid) 52.93 45.06

Example 4

For pyrolysis, a 10% solution of amorphous polypropylene in gas oil was prepared, the properties of which are given in Example 1. The experiments were performed under the conditions as in Example 2. The results of copyrolysis of gas oil with amorphous polypropylene are shown in Table 4.

Table 4. Copyrolysis of gas oil in amorphous polypropylene

Temperature, ° C 780 The ratio of water to raw material 1.0 Amount of amorphous polypropylene,% wt. 10 Raw material flow, g.h 28.8 28.0 Dwell time, p 0.038 0.035 Amount of pyropas,% wt. 35.03 40.74 Product yields in% wt. Methane 4.82 4.34 Ethane 2.33 1.81 Ethylene 12.40 14.75 Propene 7.06 8.21 1,3-Butadiene 2.22 2.69 After all, pyrolysis products 71.17 68.20

(gaseous and liquid)

Example 5

In order to obtain data on the coking of the monitored raw materials under copyrolysis conditions, experiments were performed in which the thermal decomposition of naphtha with polyalkenes was performed under hard pyrolysis conditions. Copyrolysis was performed in the absence of water vapor. The amount of coke deposited in the stainless steel tubular reactor (primary coke) and in the cooling (secondary coke) was determined as a function of time. The results are shown in Table 5.

Table 5. Copyrolysis of naphtha with low molecular weight polyethylene and polypropylene. Hydrocarbon feed: .26 g.h ~, amount of coke in grams

Raw material Coking site Experiment time, min. 15 30 120 1. Primary gasoline reactor, g 0.10 '0.10 0.20 cooler, g 0.06 0.12 0.14 2. Primary gasoline + 5% reactor, g 0.08 0.12 0.21 low milks. polyethylene cooler, g 0.06 0.10 0.17 3. Primary gasoline + 5 S reactor, g 0.15 0.17 0.30 amorphous polypropylene cooler, g 0.07 0.12 0.18

Ί

CS 275924 Β6

Example 6

The effect of higher content of low molecular weight polyethylene (20% by weight) on copyrolysis with naphtha and amorphous polypropylene (25% by weight) on copyrolysis with naphtha is shown in Table 6. The properties of hydrocarbon feedstocks are given in Example 1 and the experimental conditions in Example 2. .

Table 6. Copyrolysis of primary petroleum fractions with waste polyalkenes

Raw material Petrol Petrol Kerosene Kerosene - + 20% PE - + 25% APP Temperature 820 820 800 800 The ratio of water to raw material 0.5 0.5 0.75 0.75 Dwell time, p 0.157 0.160 0.130 0.137 Amount of pyropas,% wt. 79.1 77.2 51.13 53.7 Extracts of products in Her wt. Hydrogen 1.1 1.0 - - Methane 15.5 16.1 12.2 13.1 Ethane 4.5 4.2 5.2 3.6 Ethylene 30.4 31.3 19.5 21.8 Propene 13.2 15.4 9.2 10.1 1,3-Butadiene 4.9 4.7 3.0 3.5 After all, pyrolysis products (gaseous and liquid) 30.4 27.3 52.9 47.9

ď- PE - low molecular weight polyethylene APP - amorphous polypropylene

Claims (1)

PATENTS Process for the production of low molecular weight alkenes by copyrolysis of hydrocarbon feedstocks in the temperature range of 600 to 900 ° C, preferably 750 to 850 ° C in the presence of water vapor, characterized in that pyrolysis of gasoline or kerosene or gas oil obtained from physicochemical processing of crude oil and fission processes with waste polyalkenes, preferably with low molecular weight polyethylene from polyethylene production and / or amorphous polypropylene from polypropylene production in an amount of 3 to 30% by weight, preferably 5 to 20% by weight per starting material.