Use of a catalyst composition for the catalytic depolymerization of plastics waste

Abstract

Use of a catalytic composition parameters comprising oxides of aluminum or oxidic compounds comprising aluminum and silicon with a molar ratio of aluminum to silicon of more than 1 in a process for the catalytic depolymerization of plastics waste.

Claims

1. A process comprising catalytically de-polymerizing plastics waste in the presence of a catalytic composition comprising oxidic compounds comprising aluminum and silicon with a molar ratio of aluminum to silicon of more than 1, wherein the catalytic composition comprises from 50 to 100 wt %, based on the weight of the composition, of at least one catalytically active amorphous aluminum oxide component which is aluminosilicate and from 0 to 50 wt %, based on the weight of the composition, of a crystalline catalytically active component containing at least one microporous aluminosilicate.

2. The process of claim 1 wherein the catalytic composition comprises an aluminosilicate compound wherein a silicon oxide component is chemically compounded with an aluminum oxide component.

3. The process of claim 2 wherein the aluminium oxide component is an acid dispersible alumina, a clay or a non-dispersible alumina.

4. The process of claim 1 wherein the catalytic composition comprises an oxide of silicon in an amount of from 0.5 to 50 wt (expressed as SiO.sub.2 equivalent), based on the weight of the composition.

5. The process of claim 1 wherein the catalyst composition comprises one or more additional metals selected from the group consisting of magnesium, calcium, zinc, boron, titanium, and zirconium; or comprises phosphorus.

6. The process of claim 1 wherein plastics waste is selected from post consumer waste plastics, off-spec plastics and industrial scrap plastic.

7. The process of claim 1 wherein the plastics waste comprises at least 50 wt % of polyolefins, styrene polymers or mixtures thereof.

8. The process of claim 1 wherein the plastics waste is essentially free of thermosetting polymers.

9. A process for the catalytic de-polymerization of plastic waste, the process comprising: a) introducing plastics waste into a reactor, melting the plastics waste, and thereafter increasing the temperature to a temperature in the range of from 350 to 600 C., b) adding a catalytic composition comprising oxidic compounds comprising aluminium and silicon with a molar ratio of aluminium to silicon of more than 1 to the molten plastics, wherein the catalytic composition comprises from 50 to 100 wt %, based on the weight of the composition, of at least one catalytically active amorphous metal oxide component which is aluminosilicate and from 0 to 50 wt %, based on the weight of the composition, of a crystalline catalytically active component containing at least one microporous aluminosilicate, c) carrying out the catalytic depolymerization at a temperature of from 350 to 600 C., and d) recovering the product fractions produced.

10. The process of claim 9 wherein the catalytic composition comprises an aluminosilicate compound wherein a silicon oxide component is chemically compounded with an aluminium oxide component.

11. The process of claim 9 wherein the plastic waste comprises at least 50 wt % of polyolefins, styrene polymers or mixtures thereof.

12. The process of claim 9 wherein the plastics waste is selected from the group consisting of post consumer waste plastics, off-spec plastics and industrial scrap plastic.

13. The process of claim 10 wherein the aluminium oxide component is an acid dispersible alumina, a clay and or non-dispersible alumina.

Description

EXAMPLES

(1) General Description of the Procedure

(2) 30 g of plastic (20% Polypropylene, 80% Polyethylene) were loaded inside the reactor and a defined amount of catalyst (approximately 20 g) was stored in a catalyst storage tank. The reactor was closed and heated from room temperature to 200 C. during 20 minutes, while simultaneously purging with a 150 mL/min nitrogen flow. When the internal temperature reached the melting point of the plastic, stirring was started and was slowly increased to 690 rpm. The temperature was held at 200 C. for 25-30 minutes. During this heating process, nitrogen coming out from the reactor was disposed of. Meanwhile, the catalyst storage tank containing the catalyst was purged with nitrogen several times.

(3) After this first pretreatment step, temperature was increased to the reaction temperature of 425 C. at a heating rate of 10 C./min, and the collection of gases and nitrogen in the corresponding gas sampling bag was started. When the internal temperature reached the reaction temperature, the catalyst was introduced into the reactor, and the circulation of the gaseous products was commuted to another pair of glass traps and corresponding gas sampling bag. This was considered as the zero reaction time.

(4) During selected time periods, liquid and gaseous products were collected in a pair of glass traps and their associated gas sampling bag, respectively. At the end of the experiment the reactor was cooled to room temperature. During this cooling step, liquids and gases were also collected.

(5) The reaction products were classified into 3 groups: i) gases, ii) liquid hydrocarbons and iii) residue (waxy compounds, ashes and coke accumulated on the catalyst). Quantification of the gases was done by gas chromatography (GC) using nitrogen as the internal standard, while quantification of liquids and residue was done by weight. Glass traps (along with their corresponding caps) were weighed before and after the collection of liquids, while the reactor vessel was weighed before and after each run.

(6) The simulated distillation (SIM-DIS) GC method was used to determine the different fractions in the liquid samples (according to the selected cuts), the detailed hydrocarbon analysis (DHA) gas chromatography method was used to determine the PIONAU components (P=paraffin, I=isoparaffin, O=Olefins, N=Naphthenes, A=Aromatics) in the gasoline fraction of the last withdrawn sample (C.sub.5-C.sub.11: Boiling point <216.1 C.; what includes C.sub.5-C.sub.6 in the gas sample and C.sub.5-C.sub.11 in the liquid samples), and two dimensional gas chromatography allowed the determination of saturates, mono-, di- and tri-aromatics in the diesel fraction of the last withdrawn liquid samples (C.sub.12-C.sub.21; 216.1<BP<359 C.).

Comparative Example 1

(7) 20 g of an an equilibrated FCC catalyst were obtained from the company Hermes catalysts. Experiments were carried out using a plastic mixture comprising 80 wt % HDPE and 20 wt % PP as raw materials. Reaction temperature was set to 425 C. Catalyst to plastic weight ratio was equal to 20/30 by wt.

Example 2

(8) Example 1 was repeated except a bottoms cracking additive BCA-105 purchased from Johnson Matthey was used. This product, according to the datasheet had an attrition resistance in accordance with ASTM 757 D of 1.3, a surface area of 130 m.sup.2/g, an apparent bulk density of 0.80, and an aluminum oxide content of 68 wt %. The wt ratio Si/Al was 0.452. The average particle size was 90 m, with 12 wt % of the particles having an average diameter of less than 40 m and 2 wt % of the particles having a size of less than 20 m. The total acidity was 160 mol/g with no Bronsted acidic sites being detectable by temperature programmed desorption with pyridine as described above.

Comparative Example 3

(9) Example 1 was repeated except that only SiO.sub.2 was used as catalyst.

(10) The results of the analysis of the cumulative selectivity is given in Table 1.

(11) TABLE-US-00001 TABLE 1 Selectivity towards certain fractions in %, MON, RON and polyaromatic contents Fraction Comp. Ex. 1 Ex. 2 Comp. Ex. 3 Gas 6.2 9.3 6.4 Gasoline 41.5 32.5 17.7 Kerosene 28.3 23.5 20.8 Diesel 16.1 20.7 31 HCO 8 14.1 24 RON 79.6 80.1 71.5 MON 77 75.5 68.4 Polyaromatic (wt %) 14 3.1 2.4

(12) The data in Table 1 show that Comparative Example 3 (SiO.sub.2) yields high amounts of diesel but only low amounts of gasoline. Comparative Example 1 yields a high amount of gas and only lower yield of diesel. Furthermore, the diesel fraction obtained with Comparative Example 1 contained diaromatics and polyaromatics in an amount exceeding the upper limit of EN 590 for diesel, i.e. the diesel fraction could not be directly used without further purification. The amount of polyaromatics in the diesel fraction exceeded the amount in Example 2 by more than a factor of ten. Also mono-aromatics are approximately higher by a factor of six in Comparative Example 1 vs. Example 2. The diesel fraction obtained in Comparative Example 3 fulfilled the EN 590 specification, but, as can be seen in the FIGURE, the cumulative conversion as function of reaction time was entirely unsatisfactory.

(13) Thus, it is apparent that a fluid catalytic cracking catalyst (FCC catalyst) has good conversion over time but does not yield a high quality diesel fraction. SiO.sub.2 does not have a noticeable catalytic activity (the thermal depolymerization without any additive resulted in about the same conversion). In any case, with SiO.sub.2 the conversion achieved over time is not feasible for an economical commercial operation.

(14) Furthermore RON and MON for the gasoline fraction in Comparative Example 3 was appr. 10% lower than for Example 2.

(15) These results show that only the catalytic composition as described in the present invention lead to good conversion, gasoline fraction with high octane number and diesel fraction with polyaromatics and diaromatics content below the limit set forth in EN 590.