Patent Application
20220041937
The present disclosure falls within the field of the chemical recycling processes of plastics which serve to valorise plastic materials otherwise destined for landfill or waste-to-energy disposal.
In particular, the present disclosure relates to a hydroconversion process by means of slurry technology which transforms mixtures of polymers or plastics, mainly, into hydrocarbons having a boiling temperature which varies in the range from 65° C. to 170° C., also known as naphtha cut.
The present disclosure falls within the scope of the depolymerization processes of plastics which can follow a molecular or chemical-type approach.
The hydroconversion reactor can traditionally be fixed bed, ebullated bed or a slurry type bed. In a slurry reactor the catalyst is dispersed in the reaction medium and uniformly distributed inside the reactor itself.
A possible configuration of the hydroconversion process of heavy oil products consists of Eni Slurry Technology, owned by Eni and known by the acronym EST.
This configuration provides a hydroconversion section in which the reactors are loaded with a molybdenum-based catalyst of such dimensions as to be completely dispersed in the reaction medium, so as to be able to operate in the slurry phase. The reaction produces a head effluent which is subsequently sent to a separator section which includes at least one high-pressure and high-temperature (HP/HT) phase separator.
The vapour phase leaving the HP/HT separator is sent to a section from which naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO) and a gaseous stream rich in hydrogen, which contains C1-C4 gas, are recovered by condensation, and which is recycled into the hydroconversion section, except for a gaseous sample which can be introduced into the reaction effluent.
The bottom stream leaving the HP/HT separator is in slurry phase and is sent to a separation section which typically comprises a series of devices of decreasing pressure and temperature—such as a medium-pressure separator, an atmospheric distillation column and a vacuum distillation column—in order to separate the VGO from the heavier products.
The heavy bottom products contain an unconverted charge, catalyst and solid formed during the reaction. A part of said heavy products is recycled into the reaction section and the remainder is removed from the process as a purge stream. The purge stream can in turn be sent to a separation section to obtain a dense stream called Cake, and a less dense stream called Clarified. This latter stream can be recycled into the reaction section, the mixing section, or removed from the process.
The reaction products of an EST process can also be obtained exclusively in the vapour phase, as occurs in the EST Vapor Phase Outflow process (EST-VPO), described in several patent applications according to the progressive development of the technology. The applicant briefly summarises the patent applications that apply the EST-VPO technology below.
WO 2008/141830 describes a process for the hydroconversion of heavy oils in which the reaction takes place in a bubble-type reactor capable of accumulating at least 50 kg/m3 of solids, fuelled by hydrogen or a mixture of hydrogen and sulphuric acid in which the hydrogen has a weight ratio, with respect to the charge, of at least 0.3. The concentration of molybdenum used as a catalyst is at least 5 kg per each m3 of charge.
WO 2008/141831 describes a system for the hydroconversion of heavy oils which consists of a solids accumulation reactor and a stripping section outside or inside the reactor. When the stripping section is internal, the reactor can be completely or partially filled and the stripping section can be positioned in the upper part of the reactor or downstream of a duct inside the reactor. When the stripping section is external, the reactor—completely filled—provides a forced recirculation circuit of the liquid phase to the reactor itself. It is also possible that there is a liquid-vapour separator downstream of the reactor.
WO 2016/103199 describes a system for the hydroconversion of heavy oils comprising a reactor, a liquid-vapour separator and a stripping section of the conversion products outside the reactor. The stripping gas is introduced directly into the reaction effluent through a stripping gas introduction duct, positioned at a point of the connection duct between the reactor head and the liquid-vapour separator, said connection duct being inclined, at least starting from the introduction point, upwards with a slope between 2% and 20%, with respect to a horizontal plane. The stripping gas introduction duct is inclined with respect to the axis of the connection duct between the reactor head and the liquid-vapour separator at an angle comprised between 20° and 65° . The flow of the stripping gas stream that is introduced into the connection duct between the reactor head and the separator has a direction from top to bottom. After stripping, the effluent is sent to an HP/HT phase separator to separate the liquid phase also containing a small amount of solids (those formed during the reaction and the dispersed catalyst) which is recycled into the reactor and a vapour phase containing the reaction products.
WO 2018/078555 describes a process for the hydroconversion of heavy petroleum products which are reacted in a hydroconversion reactor, together with a recycling containing hydrogenating gas and in the presence of a suitable catalyst producing a two-phase effluent. The reaction effluent is fed to a high-pressure and high-temperature stripping step, which operates at the reaction pressure, using a stream as a stripping gas having the same composition as the gas fed to the reactor; and thus producing a stream in vapour phase and a stream in slurry phase containing the heavy products and solids. The slurry is in part recirculated into the hydroconversion section, and partly withdrawn, continuously forming a purge stream. Several methods have been developed for the purge treatment in order to recover the components that can be valorised, such as for example the catalyst metals.
WO 2014/025561 describes a process for the recovery of a catalyst for hydro-cracking from an effluent coming from a hydro-cracking slurry zone. Said process provides that the effluent is separated into a first stream containing solvent and a clarified (pitch), and a second stream containing pitch and catalyst.
The separation can take place by centrifugation, filtration, decantation or electrostatic separation. The second stream is treated by leaching with acid so as to extract the catalyst and form an aqueous solution and a residue. The aqueous solution is then treated with anions to form an insoluble salt, the catalyst, and a further aqueous solution.
US 2013/0247406 describes an integrated process which comprises:
a process for valorising heavy crude oils to convert them into lighter products in the presence of a catalyst;
a deoiling process in which the heavy residues and the heavier products deriving from the treatment of heavy crude oils are separated by the exhausted catalyst which will subsequently be recovered;
a synthesis zone of the catalyst.
The separation of the catalyst takes place by treatment with filtration technologies on membranes, and a subsequent stage of thermal devolatilization.
WO 2009/070778 describes a method for recovering the metals of an exhausted catalyst used in a slurry process valorising heavy oils. According to WO 2009/070778 the phase containing the exhausted catalyst is subjected to pyrolysis and the pyrolysis residue is put in contact with a leaching solution containing ammonia and with air, to dissolve the metals of the VIB and VIII groups, and form a slurry under pressure. Said slurry contains at least one soluble metallic complex of the VIB and VIII group, ammonium sulphate and a solid residue containing at least one metal complex of the VB group and coke.
Subsequently the solid residue containing ammonium metavanadate and coke from the pressurised slurry is separated and removed. A portion of the metals of the VIII group is precipitated. The precipitation is carried out at a predetermined pH to selectively precipitate a portion of the metal complexes of the VIB and VIII groups.
US 2010/0122938 relates to a process for separating ultra fine hydro-cracking solid catalysts from a liquid slurry of hydrocarbons, said solids present in an amount comprised between 5% and 40% by weight. The process envisages the following stages:
EP 2440635 describes a process for recovering metals from a stream rich in hydrocarbons and carbon residues which comprises the following stages:
Patent application US 2010/0326887 describes the separation of a not-sticky pitch from a hydrocarbon slurry, by means of a distillation treatment which brings the Vacuum Gas Oil (VGO) content in the final product below 14% by weight. The solids are concentrated at the bottom of the column to give pitch.
WO 2017/109728 describes a process for the treatment of refinery purge streams which comprises the following steps:
In said process the weight ratio between purge and flux varies between 1:0.5 and 1:4, and the average residence time of the mixture during the mixing and before the liquid-solid separation is lower than or equal to 12 hours. As previously stated, the purge stream constitutes a value comprised between 6% and 8% of the fresh charge, so that the total conversion that can be obtained under normal operating conditions varies from 92% to 94%. In the literature, the possibility of producing liquid fuels from waste from the processing of plastic materials is documented. The processes used can be catalytic or thermal. Some of these documents are listed:
The purely thermal degradation of polymeric waste has been studied both in the laboratory and on a pilot scale.
For the class of styrene-type polymers good yields in styrene (greater than or equal to 75%) can be obtained by rapid pyrolysis (depolymerization with molecular approach). In order to effectively deal with this depolymerization process and obtain the starting styrene monomer, it is necessary to feed the process with a polystyrene-only charge, the process is not effective using a mixture of polymers as the charge.
For polyethylenes, polypropylenes and polyvinyl chloride, monomer yields are low and mainly high molecular weight hydrocarbons (oils) and gases with high calorific power are produced. This means that it is not possible to depolymerize polymers such as polyethylenes, polypropylenes and polyvinyl chloride to monomers or to building blocks of the plastics production chain.
On the other hand, said classes of polymers treated in mixture generate low-quality fuel oils which need to be upgraded in order to be valorised based on their net calorific value. In this case, therefore, the low efficiency recycling of plastics to energy is discussed. Furthermore, the formation of coke is caused as a by-product, causing fouling of the relative plants and the impossibility of running continuously. Due to these criticalities, this process is not applied industrially. The catalytic processes for the conversion of plastics are of various nature and normally provide for a thermal pre-treatment of the plastic material in order to obtain a heavy hydrocarbon (Heavy Oil) that can be fed to a catalytic hydroconversion process to produce hydrocarbons, including the naphtha cut.
hydroconversion of polymer mixtures which comprises the following steps:
A further embodiment of the present disclosure is a mixture of polymers in solid phase which comprises:
Advantageously with the described and claimed process it is possible to demonstrate the flexibility of the charges in the hydroconversion process and the feasibility of the chemical recycling of the polymers, the naphtha being at the base of the petrochemical chain. In this way it is possible to valorise a waste product from the recycling of plastics or polymers.
According to a molecular approach, the polymers are treated to obtain the monomers used at the outset. According to a chemical approach, instead, starting from a plastic it is possible to obtain building blocks of the petrochemical industry.
The present disclosure follows a chemical-type, chemical recycling approach, precisely because it starts from polymeric or plastic materials, to obtain mainly naphtha as a product, which is one of the main reactants for the production of plastics.
The proposed solution makes it possible to insert plastic materials in the circuit of the circular economy which would otherwise be destined for landfill or waste-to-energy disposal, positively impacting the reduction of the consumption of raw materials, both of fossil origin (polymeric materials of petroleum origin) and of vegetable origin (bio-based polymeric materials). In this way these materials are valorised at light hydrocarbon fractions through slurry hydroconversion technologies, for example the Eni Slurry Technology (EST) hydroconversion process. In the present patent application, the term “polymer mixtures” is meant as a solid mixture of one or more polymers, possibly containing additives of organic or inorganic origin.
The described and claimed process allows increasing the naphtha fraction thanks to the conversion of the polymer charge.
Furthermore, it concentrates the inorganic components present in the initial polymer mixture in the solid residues, without contaminating the hydrocarbon products. The products obtained with the hydroconversion process of the polymeric mixtures, lead to the production of monomers to be included in the synthesis chain of plastic materials usable in every application.
One of the major disadvantages of the production of products from the mechanical recycling of plastic materials is represented by the fact that it is not always possible to allocate the product obtained from mechanical recycling to the same application from which the waste was derived. In fact, applications exist that are very sensitive to the contamination present in the waste collection flows (for example “food” applications, i.e. in contact with food).
With the described process, instead, naphtha is produced which can be used in the supply chain for the synthesis of polymers, which can also be used in “food” applications (from which the largest share of post-consumer waste comes).
The hydroconversion technology or EST incorporates therein the characteristic advantages of chemical recycling processes via hydroconversion, all while avoiding one of the main criticalities which is the deactivation of the catalyst due to impurities introduced through the polymer charge.
In detail, through the hydroconversion of plastic materials via hydroconversion or via EST technology there is:
Further aims and advantages of the present disclosure will appear more clearly from the following description and from the accompanying figures, given purely by way of non-limiting example, which represent preferred embodiments of the present disclosure.
The slurry (7) is fed into a separation section (D) to separate Vacuum Gas Oil (VGO) from a heavy product which partly recirculates to the mixing section (12, F) and partly forms a purge stream (9). The purge is subjected to a liquid-solid separation (E) where a heavy or dense phase (10) is separated from a light or clarified phase (11) which is recirculated to the mixing section (F).
In the present patent application, slurry phase is meant as a mixture of liquid and solid.
In the present patent application the term “purging” is meant as slurry-phase organic streams which contain a quantity of hydrocarbons having a boiling point greater than or equal to 540° C. greater than 65% by weight, a quantity of asphaltenes greater than or equal to 20% by weight and characterised by the presence of solids contents greater than or equal to 4% by weight, the remainder being hydrocarbons having a boiling point comprised between 350° C. and 500° C. Purge solids contain carbonaceous residues and metal compounds which can contain sulphides of transition metals, such as for example molybdenum, iron, nickel and vanadium, and having sub-millimetre dimensions. For the purposes of this discussion, the term “solid” is meant as the insoluble fraction in tetrahydrofuran, indicated in this text by the acronym THF-i.
For the purposes of this discussion, the term “asphaltenes” is meant as the organic fraction soluble in tetrahydrofuran but insoluble in n-pentane.
Asphaltenes are classified according to their insolubility in n-paraffins (typically having 5 to 7 C5-C7 carbon atoms). Such compounds are generally constituted by nuclei of variously branched aromatic polycondensates and joined together through linear chains. These compounds can contain heteroatoms (S, N) therein which give them their polar nature.
In the present patent application the term “cake” is meant as a solid material at room temperature with glass-like characteristics (i.e. the appearance of the cake has the characteristics of glass) that make it easily grindable and consequently transportable even for long stretches without requiring a particular thermostatic control. This characteristic remains at temperatures ranging in the interval comprised between 50° C. and 60° C.
The cake is hard at room temperature with a softening point comprised between 80° C. and 100° C. and a degree of penetration from 2 dmm to 5 dmm (dmm indicates decimillimetres). The softening point is the temperature at which the solid cake becomes soft and indicates the dependence of the cake's consistency on the temperature. The degree of penetration is measured according to the method ASTM-D5-06 and expresses the penetration the material undergoes at room temperature by a needle of known weight, in decimillimetres.
The consistency of the cake is due to the presence of solids (THFi) in greater concentration than the other streams and to the presence of asphaltenic compounds.
The cake contains solids as previously defined in the text of the present patent application.
The cake solids contain carbonaceous residues and metal compounds which can contain sulphides of transition metals, such as for example molybdenum, iron, nickel and vanadium, and having sub-millimetre dimensions.
In the present patent application the term maltenes is meant as the set of those compounds soluble both in Tetrahydrofuran and in n-pentane.
In the present patent application the term “styrene residue” is meant as a by-product of industrial origin deriving from the production of styrene and ethylbenzene and/or production of styrene polymers/copolymers. In particular it can contain aromatic organic compounds such as for example benzene, ethylbenzene, styrene, toluene, xylenes, propylbenzenes, alpha methyl styrene, polyethylbenzenes, styrene oligomers, oligomers of the SAN copolymer (styrene-acrylonitrile), polycyclic aromatic hydrocarbon compounds (naphthalene, anthracene, fluorantene, etc.); both short-chain hydrocarbons, i.e. with less than or equal to 12 carbon atoms, and long-chain, i.e. with carbon atoms equal to or greater than 12, mineral oils with carbon atoms comprised between 10 and 40; other unsaturated compounds such as for example acrylonitrile, and mixtures of the components listed above.
In the present patent application the term “phenolic residue” is meant as a by-product of industrial origin deriving from the production of phenol and its derivatives such as cyclohexanone and cyclohexanol. In particular the phenolic residue can contain aromatic organic compounds such as phenol, cresols, acetophenonene, cumene, alpha-methyl styrene; both short-chain hydrocarbons, i.e. with less than or equal to 12 carbon atoms, and long-chain, i.e. with carbon atoms equal to or greater than 12, mineral oils with carbon atoms comprised between 10 and 40 and mixtures of the components listed above.
In the present patent application, all the operating conditions reported in the text must be understood as preferred conditions, even if not expressly declared. For the purposes of the present discussion the term “comprise” or “include” also comprises the term “consist in” or “essentially consisting of”.
For the purposes of the present discussion the definitions of the intervals always comprise the extremes unless otherwise specified.
Hydroconversion is usually carried out starting from heavy petroleum products and can be achieved by adopting different process schemes.
In the present patent application, heavy petroleum products is meant as crude oils, heavy crude oils, bitumen from bituminous sands, distillation residues, heavy distillation cuts, de-asphalting residues, synthetic oils produced by the Fischer Tropsch process, vegetable oils, coke-derived oils and oil shale, oils obtained by thermal decomposition of waste, polymers, biomass.
The method for the hydroconversion of polymer mixtures which is the object of the present patent application is now described in detail, also with reference to
A mixture of polymers (1) is suitably pre-treated, then it is mixed with a vacuum residue (14). The catalyst precursors (2) can be fed to the mixer (F) or to the hydroconversion reactor (A). The mixture (15) is then subjected to a hydroconversion reaction producing hydrocarbons having a lower boiling temperature than the starting charge. In particular, a conversion of the mixture of polymers to hydrocarbon products is observed with boiling temperatures preferentially in the range from 65° C. to 170° C., also known as naphtha cut.
In the present patent application vacuum residue is meant as the residual stream of industrial origin which remains following a vacuum distillation of the pool of crude oils entering a refinery.
For the purposes of the present disclosure, the mixture of polymers mixed with the vacuum residue comprises polymeric waste deriving, for example, from the sorting cycle of differentiated solid urban plastic waste, from the selection from unsorted solid urban waste, from waste from industrial, craft, commercial and agricultural activities. The treated polymer mixtures are in solid phase and comprise:
The inorganic component of the polymeric mixture (consisting of ashes) and the unconverted polymers are instead concentrated in the fraction called THF-i (insoluble tetrahydrofuran).
A preferred mixture contains 35-60% by weight of polyethylene (PE) 15-40% by weight of polypropylene (PP); 0-25% weight of polystyrene (PS), 0-15% weight of polyethylene terephthalate (PET), 0-5% weight of polyvinyl chloride (PVC), 0-15% weight of inorganic charges. The polymer mixtures are mixed with the vacuum residue preferably at 5% by weight, more preferably at 20% by weight.
The process which is the object of the present patent application comprises several steps, among these a pre-treatment step of the polymer mixture (G) which has the purpose of making the polymer mixture miscible or suspendable in the vacuum residue (Vacuum Oil); and a hydro conversion step (A) of the reactant mixture to produce hydrocarbon products, among which preferably naphtha cuts. Naphtha is at the base of the petrochemical chain and thus allows valorising a waste product from the recycling of plastics or polymers.
A polymer mixture (1) can be pre-treated through methods selected from mechanical methods, chemical methods, thermal methods, or combinations thereof, in a pre-treatment section (G) forming a pre-treated charge. Among the preferred mechanical pre-treatments is grinding, also cryogenic, of the polymer mixture, in order to reduce the average dimension of the charge D50 itself to less than or equal to 1 mm.
The particle size distribution of the ground polymeric mixture was evaluated using Light Scattering measurements, performed with Mastersizer 2000 (Malvern Instruments). The dimension (MT50 or D50) is measured with a laser granulometer and is the diameter corresponding to 50% by weight of particles having a smaller diameter, and 50% by weight of particles having a larger diameter.
Among the preferred chemical pre-treatments are those selected from:
Among the preferred thermal pre-treatments is the method which involves heating the polymer mixture to a temperature T greater than or equal to 200° C. in an inert environment, possibly also through equipment such as extruders, thus allowing the intimate mixing of the polymeric components and the best subsequent mixing with Vacuum Oil. The pre-treatments can preferably be combined together in order to obtain the best stability of the final solution or suspension.
The pre-treatments can also be combined with each other, the preferred combinations being the following:
Once the charge is pre-treated it can be mixed in a mixing section (F) with a vacuum hydrocarbon residue, optionally pre-heated, forming a reactant mixture which can be subsequently fed into a hydroconversion section in slurry phase (A). In this phase a catalyst precursor containing Molybdenum can also be added; otherwise said precursor can be added to the reactor.
The mixture thus formed, and possibly the precursors, are fed together with a stream containing hydrogen to the hydroconversion reactor (A) to conduct a hydroconversion reaction producing a reaction effluent.
Preferably the hydroconversion reactor in slurry phase is a bubble column. One or more hydroconversion reactors placed in parallel can be used; similarly, one or more high-pressure and high-temperature separators can be used in parallel.
Preferably a part of the hydrogen-containing recycling gas (13) is fed to the high-pressure and high-temperature separator.
The reaction effluent can be separated into at least one high-pressure and high-temperature separator (B) in a vapour phase and a slurry phase. The separated vapour phase can be subsequently sent to a vapour treatment section (C) with the function of separating a liquid fraction from the hydrogen-containing gas.
The vapour treatment section operates at gradually decreasing pressure and temperature. Said section can comprise heat exchangers interspersed with a washing column which uses VGO as a solvent, a high-pressure and medium-temperature separator, a high-pressure and low-temperature separator.
From the vapour treatment section, naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO) and a gaseous stream rich in hydrogen are recovered, which contains hydrocarbon gases having from 1 to 4 carbon atoms, and which is recycled to the hydroconversion section (4), except for a gaseous sample that can be fed into the high-pressure and high-temperature separator (B).
The slurry phase can be subsequently sent to a separation section (D) that has the function of separating the fractions of the Vacuum Gas Oil (VGO), Heavy Vacuum Gas Oil (HVGO) , Light Vacuum Gas Oil (LVGO) , Atmospheric Gas Oil (AGO), from a stream of heavy organic products which contains asphaltenes, unconverted charge, catalyst and solid formed during the hydroconversion reaction.
Said liquid separation section (D) can preferably comprise a series of devices of decreasing pressure and temperature. In a first step the slurry is fed to a high-temperature and low-pressure separator which acts as an accumulator; in a second step the separated vapour phase is fed into a pre-flash column, eventually the bottom current is fed to a stripper to separate the light oils, and finally in a third step the enriched stream leaving the stripper is fed to a vacuum distillation column; alternatively, the stripper is not present and the bottom stream is fed to a vacuum distillation column. The Vacuum Gas Oil (VGO) fraction, the Light Vacuum Gas Oil (LVGO) fraction, the Heavy Vacuum Gas Oil (HVGO) fraction, the Wash Oil and the vacuum residue are recovered from the vacuum column. The Vacuum residue leaves the bottom of the vacuum column and is rich in asphaltenes, solids, metals and catalysts and forms a stream of heavy products.
A part of the heavy products (12,
The described and claimed process can comprise a further purge processing step which provides a liquid-solid separation treatment selected from sedimentation, filtration or centrifugation.
In a first separation process the purging can be heated to a temperature greater than or equal to 185° C. and no greater than 220° C., preferably between 200° C. and 220° C.
Subsequently the hot purge can be cooled by progressively and in a controlled manner lowering the temperature to a minimum temperature of 100° C., preferably comprised between 100° C. and 170° C., more preferably comprised between 100° C. and 160° C., without stirring the purge, so as to form a light phase (clarified) and a heavy phase (cake) as a function of the density.
The controlled lowering of the temperature can occur in different ways:
The controlled lowering of the temperature is of a value ranging from 3° C. per minute to 10° C. per minute, preferably from 5° C. per minute to 10° C. per minute, more preferably 10° C. per minute.
The cooled purge can be subjected to sedimentation, for example in a static sedimentation tank (E); during the static sedimentation, the temperature must be such as to make the asphaltenes insoluble and at the same time make the clarified part movable, allowing its extraction. In the temperature range comprised between 100° C. and 160° C. the separation of the dense phase (cake) is optimal. During the sedimentation phase the purge is not shaken. The sedimentation forms a light phase, called clarified, and a heavy phase, called cake, as a function of the density.
The time required for the formation of a heavy phase or cake can range from preferably 15 minutes to 2 hours, more preferably it ranges between 20 minutes and 1 hour. The sedimentation rate is preferably comprised between 85 mm/hour and 300 mm/hour.
The cake produced is “glassy” at room temperature with a softening point that can range from 80° C. to 100° C. and penetration 2 dmm.
The consistency of the cake is due to the presence of solids (THFi) in greater concentration than the other streams and to the presence of asphaltenic compounds. The clarified (11) thus obtained can preferably be recirculated into the mixing section (F) or into the hydroconversion section (A).
In an alternative separation process the purge is mixed, at a temperature greater than or equal to 100° C., with a mixture of hydrocarbons or flux which has a total aromatic compound content ranging from 50% to 70% by weight, and a starting boiling point equal to or greater than the temperature at which the mixing is conducted, so as to form a suspension with a content greater than or equal to 10% by weight of compounds having a boiling point Tbp less than or equal to 350° C.
Said suspension is then subjected to a liquid-solid separation stage, which operates at a temperature greater than or equal to 100° C., separating a solid phase containing a residual organic component and a solid component, cake, and a liquid phase containing solid residues.
The liquid-solid separation is preferably carried out by filtration or by using a centrifugal decanting device (centrifugation) which operates at temperature. The separation is followed by cooling the solid phase (cake) thus obtained under 60° C., including the upper end, and maintaining it at a temperature lower than or equal to 60° C.
The catalyst used during the hydroconversion reaction is generated “in situ” by an oleosoluble precursor containing Mo, which can be fed to the hydroconversion reactor in liquid phase directly with the charge, or to the mixer together with the vacuum residue. The normally used precursor consists of Mo 2-ethylhexanoic acid (2-ethylhexanoate) solution, containing 15.5% by weight of Mo.
The catalyst precursor is liquid and reacts with the sulfide coming from the charge and the hydrogen present in the reactor forming MoS2 (solid molybdenite finely dispersed in the liquid phase) in lamellas.
The hydroconversion reactors can operate in a temperature range comprised between 420° C. and 440° C., at a pressure comprised between 155 atm and 160 atm.
The high-pressure and high-temperature separators operate in the same operating conditions as the hydroconversion reactors, except for the head losses and the heat losses along the line that connects the reactors to the separators.
Some application examples of the present disclosure are now described, which have a purely descriptive and non-limiting purpose and which represent preferred embodiments.
Description of polymeric charge
The polymeric charge used in the following examples, indicated with the term PLASMIX, is a mixture coming from the sorting of the separate collection of plastic packaging. These materials originate from industrial residues and/or post-consumer materials.
In particular, the unselected fraction output from the sorting process was tested, consisting of a mixture of heterogeneous plastics, mostly polyolefins.
The mixture consists of flakes with dimensions D50>1 cm and characterised by an apparent density of 200 kg/m3 measured according to the method ASTM D1895-96.
The described charge is insoluble in tetrahydrofuran.
In all the examples the mixture of polymers or plastics (polymeric charge) contains 35-60% weight of polyethylene (PE), 15-40% weight of polypropylene (PP); 0-25% weight of polystyrene (PS), 0-15% weight of polyethylene terephthalate (PET), 0-5% weight of polyvinyl chloride (PVC), 0-15% weight of inorganic charges.
The mixtures of polymers or plastics are mixed with the vacuum residue preferably at 5% by weight with respect to the vacuum residue.
For grinding, a Retsch Mill with a rotor diameter of 130 mm was used equipped with a 1.5 kW motor with the following operating conditions:
For grinding, a Retsch Mill ZM200 was used, an ultra-centrifugal rotor with annular screens, with current absorption of 1300 W and rotation speed between 6000 and 18000 rpm. Operating conditions:
100 ml of aqueous solution of NaOH at 10% w/w is prepared at room temperature in a glass flask. The polymeric charge at 5% w/w is added to this solution. This means that out of 100 grams of reactant mixture, 5 grams are the polymer mixture and 95 grams are the Vacuum residue. The system is initially stirred with a stirbar and subsequently the suspension thus obtained is left to rest for 12 hours.
100 ml of aqueous solution of Ca(OH)2 at 10% w/w is prepared at room temperature in a glass flask. The polymeric charge at 5% w/w is added to this solution. The system is initially stirred with a stirbar and subsequently the suspension thus obtained is left to rest for 12 hours.
100 ml of aqueous solution of H2SO4 at 10% w/w is prepared at room temperature in a glass flask. The polymeric charge at 5% w/w is added to this solution. The system is initially stirred with a stirbar and subsequently the suspension thus obtained is left to rest for 12 hours. The pre-treatments reported in examples 2-3-4 were also repeated by adding 10% w/w and 20% w/w of polymeric charge to the different aqueous solutions.
100 ml of aqueous solution of NaOH at 10% w/w is prepared at room temperature in a glass flask. The polymeric charge at 5% w/w is added to this solution. The system is initially stirred with a stirbar and subsequently the suspension thus obtained is left to rest for 12 hours. The suspension is filtered to remove the aqueous phase; the solid phase retained on the filter is dried in an oven at 120° C. for one night.
The pre-treatment reported in example 5 was also repeated using a solution of Ca(OH)2 and H2SO4.
45 grams of “styrene residue” are heated to 120° C., maintaining the stirring for 2 h, after which 15 grams of polymeric charge are added. The mixture is kept at 120° C. for 16 h in nitrogen storage.
1 lt. of “styrene residue” is distilled obtaining a fraction containing the compounds with boiling temperatures greater than 350° C. This heavy fraction is then heated to 200° C., mechanically stirred and 5% of polymeric charge is added. The mixture is then cooled and placed in an ultrasonic bath at 50° C. for 2 h.
1 lt. of “styrene residue” is distilled obtaining a fraction containing the compounds with boiling temperatures lower than 350° C. This heavy fraction is then heated to 120° C., mechanically stirred and 5% of polymeric charge is added.
The mixture is then cooled and placed in an ultrasonic bath at 50° C. for 2 h.
20 g of polymeric charge is placed in a nitrogen vented oven at 200° C. for 16 h.
20g of polymeric charge is placed in a nitrogen vented oven at 250° C. for 16 h.
20g of polymeric charge is placed in a nitrogen vented oven at 350° C. for 16 h.
2 kg of polymeric mixture is loaded into a co-rotating twin-screw extruder, equipped with a die plate having cylindrical holes. It is all extruded by operating at a constant temperature profile equal to 300° C., at a pressure upstream of the die plate equal to 50 bar, at a total flow rate equal to 10 Kg/h and at a screw rotation speed equal to 200 rpm. The material is extruded in the form of “spaghetti”, cooled in a water bath, air-dried and granulated using a cutter.
2 kg of polymeric mixture is loaded into a co-rotating twin-screw extruder, equipped with a die plate. It is all extruded by operating at a constant temperature profile equal to 300° C., at a pressure upstream of the die plate equal to 15 bar, at a total flow rate equal to 10 Kg/h and at a screw rotation speed equal to 200 rpm. The material melted by the extruder is added to the vacuum residue.
5 grams of the pyrolysed material is taken at 200° C. (example 10) and mixed with 95 grams of acetone.
5 grams of the pyrolysed material is taken at 250° C. (example 11) and mixed with 95 grams of acetone.
Case 1: The polymeric charge is treated as in Example 1, i.e. ground. 5 grams of pre-treated polymeric charge are taken, available at room temperature, and 95 grams of vacuum residue pre-heated to 200° C. are added. The mixture is kept warm at 200° C. for 2 h under mechanical stirring.
Case 2: The polymeric charge is treated as in Example 1, i.e. ground. 20 grams of pre-treated polymeric charge are taken, and 80 grams of vacuum residue pre-heated to 200° C. are added. The mixture is kept warm at 200° C. for 2 h under mechanical stirring.
Case 3: The polymeric charge is treated as in Example 1, i.e. ground. Subsequently, 5 grams of ground polymeric charge are taken and treated as in example 3, i.e. chemically pre-treated with a 10% w/w NaOH solution. The polymeric charge thus pre-treated is added to 95 grams of vacuum residue pre-heated to 200° C. The mixture is heated to 200° C. for 2 h under mechanical stirring.
Case 4: The polymeric charge is treated as in Example 2, i.e. ground. 5 grams of pre-treated polymeric charge are taken, available at room temperature, and 95 grams of vacuum residue pre-heated to 200° C. are added. The mixture is kept warm at 200° C. for 2 h under mechanical stirring.
Several experiments were conducted using a 30 cc microautoclave reactor. The tests were conducted under the following operating conditions:
The mixtures tested in the various cases were characterised quantifying by precipitation the amount of insolubles in tetrahydrofuran (THF-i), the insolubles in n-pentane (Ins-C5, fraction normally considered as an asphaltenic fraction) and the characterisation of the fraction thus de-asphalted using the ASTM D2887 method. The reaction products are collected at the end of the test, quantified and characterised.
The gas phase is characterised by the ASTM D7833 Standard Refinery Gas Analysis method. Of the liquid phase, the insoluble in THF (THF-i) and the insoluble in n-pentane (Ins-C5) are quantified by precipitation and the de-asphalted fraction is analysed with the method D2887. The tables show the yields calculated according to the following formula:
Mproduct (OUT): mass of outgoing product (g)
Mmixture (IN): mass of mixture loaded (g).
The outgoing products considered are gaseous products containing 1 to 4 carbon atoms (C1-C4), gaseous products containing 5 carbon atoms and liquid products with a boiling temperature comprised between 65° C. and 170° C. (65° C. (C5)-170° C.) considering the naphtha cut; liquid products with boiling temperature between 170° C. and 350° C. (170° C.-350° C.); liquid products with boiling temperature between 350° C. and 500° C. (350° C-500° C.); liquid products with a boiling temperature above 500° C. (500+° C.), products insoluble in n-pentane (Ins-C5) and products insoluble in tetrahydrofuran (THF-i).
The EST base case represents the reactivity of the vacuum residue alone in hydroconversion conditions. The polymeric charge is insoluble in tetrahydrofuran and constitutes the THF-i fraction present in the charge.
In case 1 a vacuum residue charge was treated, added to 5% of mechanically pre-treated polymeric charge (see the Case 1 description of the mixture preparation) while in case 2 the quantity of polymeric charge introduced was increased from 5% to 20%. An increase in the yields of the fraction 65° C-170° C. is observed, along with the increase in the charge treated.
THF-i also increase from the base case to case 1 to case 2. This fraction consists of THF-i reaction products (see base case), THF-i deriving from the organic fraction of unconverted plastic material, accumulation, in THF-i, of the inorganic fraction (ashes of the polymeric charge).
In case 3 the reactivity is reported under the same operating conditions using a vacuum residue mixture with 5% w/w of Plasmix chemically pre-treated with NaOH. As can be seen, while maintaining the naphtha cut yield at 65° C.-170° C., the production of THF-i considerably increases, indicating how the presence of NaOH intervenes in the overly high production of solid carbonaceous compounds.
In case 4 the reactivity is reported, under the same operating conditions, using a mixture of vacuum residue with 5% w/w of Plasmix pre-treated by grinding, obtaining a Plasmix with D50<0.2 mm. As can be seen, the naphtha cut yield 65-170° C., compared to Case 1 in which the Plasmix was more coarsely ground, slightly increases, as does the production of solids. The decrease in the diameter of the polymeric charge particles helps, in both the mixing and homogenisation of the polymeric charge with the vacuum residue in the preparation phase of the mixture, and, moreover, make the material more available for both the naphtha cut and carbonaceous solids reaction.
Case 5: The polymeric charge is treated as in Example 1, i.e. ground. 5 grams of pre-treated polymeric charge are taken, available at room temperature, and 95 grams of vacuum residue pre-heated to 200° C. are added. The mixture is kept warm at 200° C. for 2 h under mechanical stirring.
Case 6:
The polymeric charge is treated as in Example 2, i.e. ground. 5 grams of pre-treated polymeric charge are taken, available at room temperature, and 95 grams of vacuum residue pre-heated to 200° C. are added. The mixture is kept warm at 200° C. for 2 h under mechanical stirring.
Several experiments were conducted using a 30 cc microautoclave reactor.
The tests were conducted under the following operating conditions:
As described in example 18, the mixtures tested in the various cases and the reaction products were characterised quantifying by precipitation the amount of insolubles in tetrahydrofuran (THFi), the insolubles in n-pentane (Ins-C5, fraction normally considered as an asphaltenic fraction) and the characterisation of the fraction thus de-asphalted using the ASTM D2887 method. The gas phase produced is characterised by the ASTM D7833 Standard Refinery Gas Analysis method.
In the base case reported in the table below and in cases 5 and 6 the operating reaction conditions have been kept unchanged and represent the conditions of a thermal treatment process.
The THERMAL base case represents the reactivity of the vacuum residue alone in thermal conversion conditions. The polymeric charge is insoluble in tetrahydrofuran and constitutes the THF-i fraction present in the charge. In case 5 a vacuum residue charge was treated, added to 5% of mechanically pre-treated polymeric charge (see the Case 5 description of the mixture preparation) while in case 6 a vacuum residue mixture was prepared, added to 5% of mechanically pre-treated polymeric charge so as to obtain particles with D50<0.2 mm. From the comparison of the base case with the cases in which the polymeric charge is added, it can be observed that in thermal conversion process conditions the naphtha yield is in any case lower than in the base case. At the same time there is evidence of a decrease in the conversion of the polymeric charge, as the THF-i are much higher at the end of the test. Considering the THF-i at the end of the test as an unconverted polymeric charge, it can be observed that the conversion in Case 5 is greater than in Case 6. Comparing the two cases (5 and 6) the increase in gas yields (C1-C4) and naphtha cut in Case 5 can be observed, indicating that the polymeric charge converts to light products even in a thermal conversion process, but predominantly with C1-C4 gaseous compounds.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018000020818 | Dec 2018 | IT | national |
This Patent Application claims priority from PCT Application No. PCT/IB2019/061213, which claims priority from Italian Patent Application No. 102018000020818 filed on Dec. 21, 2018, the entire disclosures of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/061213 | 12/20/2019 | WO | 00 |
