RECYCLING OF HYDROCARBONS IN CATALYTIC CRACKING
Abstract: The possibility of the chemical recycling of waste hydrocarbon fractions, e.g. waste polymers or waste lubricating oils in catalytic cracking was verified in the MAT laboratory test. Linear 1-olefins were used as model compounds simulating products of thermal pre-cracking of waste polyolefins into liquid fraction suitable for admixing to HVGO as standard FCC feed, and products of semi-pilot plant thermal/catalytic cracking of industrial PP wastes were used as possible real feed. Filtered used automotive oil was tested as possible feed to catalytic cracking to chemical recycling.
A standard FCC catalyst was used in microactivity test at 525°C, introduction time of 40 s and catalyst/feed ratio of 4.76 g/g. No negative effect in coking was observed as consequence of olefinic fraction adding to hydrogenated VGO feed. Similarly, the use of thermally/catalytically precracked fraction in pilot-plant treatment of industrial polypropylene wastes showed good possibility of chemical recycling of waste polyolefines in FCC process into gases and gasoline fraction. Catalytic cracking of used automotive oil increased conversion to gases and gasoline with little increase of Gas Factor after longer use of this oil. Results showed good possibility for chemical recycling of waste polymers and waste lubricating oils in FCC technology into gases and gasoline. Keywords: waste plastics;
CHEMICAL RECYCLING OF
WASTE HYDROCARBONS:
Waste hydrocarbons represent a serious problem in everyday life. The greatest quantities of waste hydrocarbons are mainly waste plastics and also used lubricating oils. Both these wastes come from crude oil and even if both could be used for energy production by incineration, the best way for they treatment should be the material or chemical recycling. Polymer wasted could be regarded as potential source of chemicals and energy. Different methods of polymer wastes recycling are developed [1,2]. One of the most attractive ways is chemical recycling that converts waste polymers into basic monomers or petrochemicals. About 60-70% of waste polymeric materials are composed of PE and PP that cannot be easily converted into monomers.
For chemical recycling of waste polymers a thermal or catalytic method could be applied, by which the long alkyl chains of polymers are broken into a mixture of lighter hydrocarbons [3-20]. One of the most appropriate chemical recycling of used polyolefins is fluid catalytic cracking process that could convert waste polyolefines directly into fractions of light olefins and motor fuels. The main problem is the state of waste polyolefines – they are available in form of greater or smaller pieces or in powder – all as solids which could not be simply added to FCC feed – hydrogenated WGO. The best way to introduce the polyolefin feed to FCC process is admixing of thermally depolymerizated polymers in liquid state to the base FCC feed – hydrogenated vacuum gas oil.
The research in this waste plastics, used oils, catalytic cracking field is focused to use of solid acid catalysts as natural or synthetic zeolites. To the main types of reactors used for the laboratory catalytic depolymerization belong batch reactor [4-6] but examples from flow-type reactors are known [7-9]. Many experiments were carried-out in thermobalances (TGA) with mixtures of about 10 wt. % of catalyst with plastics The best possibility gives laboratoty simulation of fluidized-bed reactors [3, 17-19] of MAT-tests. As heterogeneous catalysts, different mesoporous acid catalysts as conventional amorphous alumosilicates [4] and different microporous molecular sieves – zeolites of types USY [6,7,12,15,16], ZSM-5, [4-7,10-15,19] BEA [10], MOR [10] as well as mesoporous molecular sieves of MCM-41 type [8,13,14,19,20], and commercial FCC catalysts [3,15-18] were tested.
Generally, the catalytic depolymerization is carried out over acid catalysts in atmosphere of nitrogen or other inert gas. Consequently, the cracking products are strongly non-saturated, and catalysts are deactivated because of coking. Catalytically pre-cracked polyolefines contain mainly linear and branched unsaturated and alkane molecules and aromatics. The olefins in feed represent the main different between such feed for FCC and standard feed for FCC, represented by HVGO. The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2.
Waste hydrocarbons represent a serious problem in everyday life. The greatest quantities of waste hydrocarbons are mainly waste plastics and also used lubricating oils. Both these wastes come from crude oil and even if both could be used for energy production by incineration, the best way for they treatment should be the material or chemical recycling. Polymer wasted could be regarded as potential source of chemicals and energy. Different methods of polymer wastes recycling are developed [1,2]. One of the most attractive ways is chemical recycling that converts waste polymers into basic monomers or petrochemicals. About 60-70% of waste polymeric materials are composed of PE and PP that cannot be easily converted into monomers.
For chemical recycling of waste polymers a thermal or catalytic method could be applied, by which the long alkyl chains of polymers are broken into a mixture of lighter hydrocarbons [3-20]. One of the most appropriate chemical recycling of used polyolefins is fluid catalytic cracking process that could convert waste polyolefines directly into fractions of light olefins and motor fuels. The main problem is the state of waste polyolefines – they are available in form of greater or smaller pieces or in powder – all as solids which could not be simply added to FCC feed – hydrogenated WGO. The best way to introduce the polyolefin feed to FCC process is admixing of thermally depolymerizated polymers in liquid state to the base FCC feed – hydrogenated vacuum gas oil.
The research in this waste plastics, used oils, catalytic cracking field is focused to use of solid acid catalysts as natural or synthetic zeolites. To the main types of reactors used for the laboratory catalytic depolymerization belong batch reactor [4-6] but examples from flow-type reactors are known [7-9]. Many experiments were carried-out in thermobalances (TGA) with mixtures of about 10 wt. % of catalyst with plastics The best possibility gives laboratoty simulation of fluidized-bed reactors [3, 17-19] of MAT-tests. As heterogeneous catalysts, different mesoporous acid catalysts as conventional amorphous alumosilicates [4] and different microporous molecular sieves – zeolites of types USY [6,7,12,15,16], ZSM-5, [4-7,10-15,19] BEA [10], MOR [10] as well as mesoporous molecular sieves of MCM-41 type [8,13,14,19,20], and commercial FCC catalysts [3,15-18] were tested.
Generally, the catalytic depolymerization is carried out over acid catalysts in atmosphere of nitrogen or other inert gas. Consequently, the cracking products are strongly non-saturated, and catalysts are deactivated because of coking. Catalytically pre-cracked polyolefines contain mainly linear and branched unsaturated and alkane molecules and aromatics. The olefins in feed represent the main different between such feed for FCC and standard feed for FCC, represented by HVGO. The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2.
EXPERIMENT: In the
present work the influence of additives of model compounds, representing
examples of thermally depolymerizated polyethylene, were studied. As model
compounds were used 1-olefines C6–C24 pure and in 10% additives to standard FCC
feed – hydrogenated vacuum gas oil. Tests were carried-out in Micro-Activity
Test (MAT) at 525°C. The treatment of long 1-olefins increases the total
micro-activity values - conversion to gases and gasoline. As industrial example
of pre-cracked polymer wastes, liquid product of thermal decomposition of
polypropylene wastes in Blowdec process [21] was studied. As feed representing
waste oils was tested used lubricating oil from diesel engine in bus.
Feeds: A)
Hydrogenated Vacuum Gas Oil (HVGO) As feed for MAT was used a standard refinery
feed for FCC from refinery - hydrogenated vacuum gas oil (HVGO). Its basic
properties are summarized as
Properties
of hydrogenated vacuum gas oil (HVGO): viscosity at 50°C- 43.41 mm2 /s,
density (20°C)- 906 kg/m3,viscosity at 100°C-8.436 mm2 /s,melting point 40°C ,sulphur
0.033 wt. % ,nitrogen 1002 ppm wt. 10% vol,nickel 0.01 ppm wt,30% vol. vanadium
,0.07 ppm wt,50% vol. sodium 0.01 ppm wt. 70% vol. iron 0.22ppm wt. 90% vol.
541°C ED 555°C
Pure LAO - Linear alpha-olefins
(Spolana Neratovice, Czech republic) with the carbon chain of 6, 8, 10, 12, 14,
16, 18, 20-24, were used as model compounds of the polyolefins thermal
depolymerization. The purity of LAO was 98.4 % wt. C) Mixture of 10 wt. % of
individual LAO in HVGO was prepared by mechanical mixing of HVGO and LAO at
temperature of 50°.
Generally, the catalytic
depolymerization is carried out over acid catalysts in atmosphere of nitrogen
or other inert gas. Consequently, the cracking products are strongly
non-saturated, and catalysts are deactivated because of coking. Catalytically
pre-cracked polyolefines contain mainly linear and branched unsaturated and
alkane molecules and aromatics. The olefins in feed represent the main
different between such feed for FCC and standard feed for FCC, represented by
HVGO.
The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2 mg/kg Mg 238 mg/kg Fe 61.1 mg/kg Al 25.8 mg/kg 2.2. Catalytic test For laboratory catalytic cracking tests of above-mentioned feeds was used microactivity test (MAT) according to ASTM D-3907-92 [22]. Reaction conditions in MAT: Temperature: 525°C Catalyst weight: 4.00 ±0.005 g Introduction time: 40 s Catalyst/Feed: 4.76 g/g Total flow of nitrogen: 30 ml/min 2.3. Catalyst As cracking catalyst, a commercial equilibrated FCC catalyst from refinery was used with acidity value by TPDA of 0.150 mmol of acid center/gram and surface area of 140 m2 /g. The main characteristics of used FCC catalyst are in Table 4, its SEM picture is in Figure 1. Before MAT tests, 4 g of catalyst was calcined at 560 °C for 3 hrs.
The paper deals with the study of the treatment of liquid and solid waste hydrocarbons – mainly waste plastics and waste lubricating oils – in catalytic cracking processes of treatment of petroleum fractions- FCC mainly to fraction of gases and motor fuels – gasoline. 2 mg/kg Mg 238 mg/kg Fe 61.1 mg/kg Al 25.8 mg/kg 2.2. Catalytic test For laboratory catalytic cracking tests of above-mentioned feeds was used microactivity test (MAT) according to ASTM D-3907-92 [22]. Reaction conditions in MAT: Temperature: 525°C Catalyst weight: 4.00 ±0.005 g Introduction time: 40 s Catalyst/Feed: 4.76 g/g Total flow of nitrogen: 30 ml/min 2.3. Catalyst As cracking catalyst, a commercial equilibrated FCC catalyst from refinery was used with acidity value by TPDA of 0.150 mmol of acid center/gram and surface area of 140 m2 /g. The main characteristics of used FCC catalyst are in Table 4, its SEM picture is in Figure 1. Before MAT tests, 4 g of catalyst was calcined at 560 °C for 3 hrs.
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