WO2009038486A1

WO2009038486A1 - Method of used oils processing

Info

Publication number: WO2009038486A1
Application number: PCT/PL2008/050014
Authority: WO
Inventors: Franciszek Steinmec; Iwona Skret; Jan Lubowicz; Michal Krasodomski; Bogdan Pawlicki; Grazyna Jolanta Mikrut; Grzegorz Kowalczyk; Mariusz Iskierski; Piotr Dziadosz; Antoni Marchut
Original assignee: Instytut Nafty I Gazu; Rafineria Nafty Jedlicze Sa
Priority date: 2007-09-17
Filing date: 2008-09-16
Publication date: 2009-03-26
Also published as: PL383382A1

Abstract

The method of used oils processing makes possible to obtain clear hydrorefined base oil, without coagulums, out of the used oil containing feed. The process is carried out in two stages. In the first stage feed containing used oil is subject to catalytic hydrodematallization in presence of NiMo/AI2O3 type catalyst, and then to the first hydrofining in presence of NiMo/AI2O3 type catalyst, further, in the second stage, feed is subject to catalytic deparaffination in presence of nickel containing catalyst deposited on ZSM-5 zeolite, and then to the second hydrofining in presence of the second catalyst of NiMo/AI2O3 type. In the whole process average temperature (WABT) is from 300 to 350 °C and space velocity (LHSV), counted in relation to total volume of catalytic beds used in the second process stage if from 0.2 to 2.0 h-1, but feed space velocity (LHSV) in relation to the hydrodeparaffination catalyst is from 0.5 to 3.5 h-1.

Description

Method of used oils processing

The subject of the invention is a method of used oils processing that makes possible to produce clear hydrofined base oil without coagulums, out of the raw material containing used oils.

Last thirty years gave origin to the development of modern processing of used oils. Known examples of industrial production technologies have been collected by Czestaw Kajdas in "Major Pathways for Used Oils Disposal and Recycling", Part 1 , Tribotest Journal 7-7, September 2000 [7] 61 , and Part 2, Tribotest Journal 7-2, December 2000 [7], 137. These examples are shortly discussed below:

KTI (Kinetics Technology International) - preliminary water and solids separation, atmospheric distillation (water and light hydrocarbons removal), vacuum distillation (lubricating oil cuts separation) - all contaminants remain in vacuum residuum;

MOHOWK (Mohowk-Oil Company of Vancouver) - preliminary water and solids separation and raw material chemical treating to separate metals, atmospheric distillation, vacuum distillation, thin-layer evaporation, hydrofinishing; BERC/NIPER (Bartelsville Energy Research Center) - preliminary water and solids separation, atmospheric distillation (water and light hydrocarbons removal), vacuum distillation (lubricating oil cuts separation), solvent extraction, vacuum distillation (fractionation), hydrofinishing or sorption on bleaching clay; PROP (Philips Petroleum Company) - metals removal (reaction with diammo- nium phosphate), atmospheric distillation, sorption on bleaching clay, hydrofin- ing (NiMo/AI₂O₃);

SAFETY KLEEN - light contaminants topping, vacuum steam stripping, vacuum distlillation, hydrotreating (NiMo/AI₂O₃);

ITP/SNAMPROGETTI - atmospheric distillation (water and light hydrocarbons removal), vacuum distillation, hydrofinishing, vacuum residuum propane deasphalting, brightstock hydrogenation; UOP DCH - metals and sludges separation, hydrofining, light contaminants preliminary topping, vacuum distillation with fractionation; VISCOLUBE - mechanical contaminants separation, deposit precipitation with sodium hydroxide, light contaminants preliminary topping, vacuum distillation with fractionation, hydrofining;

HYLUBE - (residuum separation out of raw material and hydrogen mixture in a high pressure separator, catalytic hydrofining, hydrorefined products fractionation).

Patent literature describes many methods of used oil processing.

Used oils refining method disclosed in patent specification PL 171473 is characterized by three preliminary stages. In the first stage NaOH is added to the used oils and the whole volume is mixed together. In the second stage mixed liquid is heated up in a heat exchanger and then decanted. In the third preliminary stage, additionally, remaining heavy sludges are separated, including high-molecular polymers and heavy metals. After mixing and heating, decanta- tion operation is carried out periodically. Next process is a vacuum distillation process in a four-stage packed fractionating column. In the next stage, after steam stripping, the treated oil is submitted, to improve the colour, to the process of clay refining or catalytic refining with hydrogen.

Similar to the above described process is the method of used oils treating, described in patent specification PL 177602. Disclosed in this patent specification refining method includes dehydration, vacuum distillation, solvent extraction and hydrofining operations. The process used there is characterized in that, that dehydrated used oils are directly vacuum distilled, without other stages, and at least one oil fraction is collected, then the vacuum residuum undergoes solvent extraction, and this vacuum residuum is separated into one or more fractions of clear oil, and extraction residuum. One or more clear oil fractions are stabilized by hydrofining. The refining process is carried out in hydrogen atmosphere and with the catalyst - oxide or sulphide of group VIII metal and/or at least group Vl, on a carrier, with space velocity in the range of 0.1 to 10 h^"1. As it could be seen from the above data, known processing methods of used oils have similar structure and consist of three to five stages. Usually these stages are:

- preliminary removal of mechanical contaminants and water;

- chemical treating of oils;

- extraction;

- vacuum fractionation;

- hydrofining.

Chemical treating stage of used oils mentioned above is used in three known mentioned above production technologies only.

In hydrofining stage known production technologies usually use two-reactor system. Main role of the first reactor is oil demetallization. To achieve this hy- drodemetallization catalysts are used, usually NiMo/AI₂O₃ catalysts, with large volume pores and because of this - low density; their bulk density is usually about 0.5 ÷ 0.6 kg/I. In the second reactor typical hydrofining catalysts are used, usually also NiMo/AI₂O₃ catalysts, but of greater density. It is recommended to use high process pressures, 7 ÷ 13 MPa. The hydrofining process is carried out in the temperature range between 290 °C and 350 °C.

In technical and patent publications there is no information about using other types of hydrofining refinery catalysts, except above mentioned two types generally known. In technical literature information regarding used oils treating, and in patent specifications, there is no mention about problems connected with quality of end-products - hydroraffinates extracted from used oils.

Industrial practice shows however that final products - base oils extracted from used oils not always are stably clear, what is required. Sometimes it can be seen that after a few dozen hours after their production, when the temperature drops to 10 ÷ 20 °C, opacity appears. This opacity is not stable but there takes place the coagulation of opacities. Coagulated substance takes shape of irregular ball or ellipsoid, that after some time falls down to the bottom of the tank. The colour of the coagulum depends on the type of used oil and could be pale-grey, grey, dark-grey or even black.

It was found that n-paraffins content in coagulums is low, so the described above unfavourable effect is not caused by n-paraffins.

But at the same time hydroxy, carboxy and carbonyl groups were found in coagulums, as well as aromatic structures. Analytical investigation of many different coagulums allowed to put scientific hypothesis that such a phenomenon is connected with more and more growing additives content and with growing share of synthetic base oils used to formulate final products. Moreover, the collection of used oils very often is carried out in a non-selective manner.

There is a possibility to remove coagulums formed, using known method of de- cantation of clear oil or filtration. In the first method process losses are very high. The second method also is not a very good solution because of quick filter blocking.

Unexpectedly it was found that problems mentioned above and regarding coagulums formation in base oils obtained out of the feed containing used oils could be eliminated completely, or at least largely limited, by introduction of a new, catalytic method of feed preparation that differs from normally used for used oils hydrofining, and also due to carrying on the process in conditions that differ from known conditions.

Method of used oils processing where feed is subject to removal of mechanical contaminants and water and/or to chemical treating and/or to removal of light chemical contaminants and/or vacuum distillation and/or to fractionation, and then is subject to catalytic treating in presence of hydrogen is characterized by that, that process is carried out in two stages.

In the first stage feed containing used oil is subject to catalytic demetallization (hydrodemetallization) in the presence of the NiMo/AI₂O₃ catalyst and then to the first hydrofining also in the presence of NiMo/AI₂O₃ catalyst, but demetallization catalyst contains, before sulphurizing, from 10 to 14 % (m/m) of molyb- denum as MoO₃ and 2 to 5 % (m/m) of nickel as NiO, and first hydrofining catalyst contains, before sulphurizing, 15 to 22 % (m/m) of molybdenum as MoO₃ and from 2.5 to 6 % of nickel as NiO, and volume of the demetallization catalyst bed in relation to the total volume of both catalysts beds used in the process first stage is from 30 to 60 % (VA/), preferably from 35 to 45 % (VA/), and similarly volume of the first hydrofining catalyst in relation to the total volume of both catalysts used in the first stage is from 40 to 70 % (VA/), preferably from 55 to 65 % (V/V).

Further, in the second process stage, preliminarily treated feed is subject to the catalytic deparaffination (hydrodeparaffination) in presence of nickel containing catalyst, deposited on the ZSM-5 zeolite, and then to the second hydrofining, in the presence of the second catalyst of NiMo/AI₂O₃ type, and hydrodeparaffination catalyst contains from 3 to 7 % (m/m) of nickel, and the second hydrofining catalyst from 15 to 22 % (m/m) of molybdenum as MoO₃ and 2.5 to 6 % (m/m) of nickel as NiO.

In the second stage of carrying out this method, the relation of the hydrodeparaffination catalyst bed volume, to the total volume of both catalysts used in this stage is from 20 to 40 % (VA/), preferably from 25 to 35 % (VA/), and similarly the relation of the second hydrofining catalyst bed to the total volume of both catalysts used in the second process stage is from 60 to 80 % (VA/), preferably from 65 to 75 % (VA/).

Method according to the invention is carried out at medium temperature (WABT) from 300 to 350 °C, preferably from 320 to 340 °C and at pressure from 5 to 12 MPa.

The temperature control in the process second stage is carried out by the addition to the hydrodeparaffination catalyst, additional amount of hydrogen, and in the whole process, feed and hydrogen are introduced to the catalyst beds co- currently, and the volumetric ratio of hydrogen to feed is 700 to 1600 (VA/), preferably from 1000 to 1500 (VA/). The volume of the catalyst beds used in the process first stage in relation to the total volume of catalyst beds used in the whole process is from 20 do 50 % (VA/), preferably from 25 to 40 % (VA/).

The space velocity (LHSV) for the whole process, related to the total volume of catalytic beds used in the second process stage is of 0.2 to 2.0 h^"1, preferably 0.3 to 1.0 h^"1, and at the same time feed space velocity (LHSV) related to the total volume of hydrodeparaffination catalyst should be contained in the range from 0.5 to 3.5 h^"1, preferably 1.2 to 2.5 h^"1.

Method according to the invention can be effectively carried out in the system containing at least one flow reactor with stationary catalytic packing. Inlet to the reactor is preferably situated at the top of the reactor. In this system there are placed in turn catalytic beds: l-bed containing hydrodemetallizing catalyst of NiMo/AI₂O₃ type, ll-bed containing hydrofining catalyst also of NiMo/AI₂O₃ type, Ill-bed containing hydrodeparaffination catalyst of zeolite type containing nickel, preferably containing catalyst on the basis of zeolite ZSM-5, and IV-bed containing hydrofining catalyst of NiMo/AI₂O₃ type, and preferably the system between bed-ll and bed-Ill should include supply of hydrogen stream. The best place for the outlet of the system is at the bottom of the reactor.

In another solution the system for carrying out the process can include two separate flow reactors in series, containing stationary catalytic beds. Inlets to reactors are preferably situated at the top of the reactors and outlets at the bottom. In the first reactor there are two catalytic beds. The catalytic bed-l that is situated in the upper part of the reactor and contains hydrodemetallization catalyst of NiMo/AI₂O₃ type, and below there is catalytic bed-ll containing hydrofining catalyst also of NiMo/AI₂O₃ type. Outlet of the first reactor is connected with the inlet to the second reactor. Moreover, to the inlet of the second reactor is connected the hydrogen stream supply to control the reactor temperature. At the top of the second reactor there is catalytic bed-Ill containing hydrodeparaffination catalyst of zeolite type containing nickel, preferably containing zeolite ZSM-5 based catalyst (activity of this catalyst is not disturbed by the presence of sulphur in hydrocarbons up to the level of 2 % (m/m). Below bed-Ill there is catalytic bed-IV containing hydrofining catalyst of NiMo/AI₂O₃ type.

For an expert it is understandable and evident that the system may be composed of 3 or 4 separate reactors containing catalytic beds of sequence and types given above.

For means and technological operations characterized above and using process conditions mentioned above, hydrofined, clear base oils are obtained, without coagulums precipitation. Taking into consideration state of art regarding knowledge of catalytic systems used and the fact that only faint amount of n- paraffins in coagulums was found, the effect of stable hydroraffinate obtained with the catalyst designed just for the deparaffination, is unexpected. Placing in two first catalytic beds hydrodemetallization catalyst and then hydrofining catalyst should be bond with the presence in used oils of compounds containing oxygen groups (alcohols, acids, esters etc.) of polar character that can influence the formation of stable coagulums containing fine-crystalline hydrocarbons.

The subject of the invention is discussed below by examples of the execution of the method in an embodied system shown on the drawing. It is understandable that examples are given to illustrate only and in no way they could limit the essence of the invention.

In all presented examples generally available catalysts were used:

1. Hydrodemetallization catalyst of NiMo/AI₂O₃ type containing 12 % (m/m) MoO₃ and 2.5 % (m/m) NiO (mesopores volume 0.555 cm³/g, dominant radius 7.9 mm);

2. Hydrofining catalyst of NiMo/AI₂O₃ type containing 21 % (m/m) MoO₃ and 4.5 % (m/m) NiO (mesopores volume 0.472 cm³/g, dominant radius 3.7 mm); 3. Deparaffination catalyst based on ZSM-5 zeolite containing 5 % (m/m) Ni (mesopores volume 0.465 cm³/g, dominant radius 5.2 mm).

System for the execution of the invention presented schematically on the enclosed drawing contains two reactors R1 and R2. The oil feed S and H₂ are introduced to R1 reactor with two catalytic beds Z1 and Z2. Z1 bed contains hyudrodemetallizing catalyst of NiMo/AI₂O₃ type, and Z2 catalytic bed contains hydrofining catalyst also of NiMo/AI₂O₃ type, and the Z1 bed volume in relation to the total volume of Z1 and Z2 beds is 40 % (VTV). The feed goes through Z1 bed and then through Z2 bed. Feed leaving reactor R1 is directed to reactor R2 containing two catalytic beds Z3 and Z4. Catalytic bed Z3 contains deparaffination catalyst of zeolite type containing nickel, based on ZSM-5 zeolite, and catalytic bed Z4 contains hydrofining catalyst of NiMo/AI₂O₃ type, and the Z3 bed volume in relation to the total volume of Z3 and Z4 beds is 25 % (VA/). Total volume of Z1 and Z2 beds in relation to the total volume of Z1, Z2, Z3 and Z4 beds is 33 % (VA/). In R2 reactor the feed goes first through Z3 bed and then through Z4 bed. To the inlet of R2 reactor H₂ is introduced to control the temperature. After passing through Z3 and Z4 beds in turn, obtained hydroraf- finate goes out of the R2 reactor as product P.

Example 1

The method was executed in experimental conditions, in a series of two working flow-reactors without process product recirculation.

In the first reactor the bed consisting of hydrodemetallizing catalyst layer 40 % (VA/). and hydrofining catalyst layer 60 % (VA/) was used. In the second reactor deparaffination catalyst layer 25 % (VA/) and hydrofining catalyst layer 75% (VA/) was used. Before starting the process the catalyst was sulphurized. In both reactors average temperatures (WABT) used for catalytic beds were respectively 320 °C and 330 °C. The feed space velocity in relation to the whole catalytic bed in the second reactor was 0.5 h^"1 with volume ratio H₂/feed equal 1500 and the pressure at the first reactor inlet 6.0 MPa.

However feed space velocity in relation to deparaffination catalyst was 2 h^"1. As a feed to the hydrofining, dark brown, non transparent feed was used, obtained in industrial plant treating used oils, subject to preliminary sedimentation of contaminants and water, and chemically treated with sodium hydroxide, subject to light contaminants topping, and then distilled under vacuum. Feed properties are given in Table 1.

As a result of carrying process according to the invention celadon-yellow clear product, not containing coagulums was obtained.

Comparison of the properties of the hydroraffinate obtained with the properties of known oil obtained from crude oil processing are also given in Table 1.

Table 1. Comparison of Properties of Obtained Oil and Known Oil

Additionally in Table 2 are given metal amounts in hydroreffined oil obtained in example 1 compared with hydroraffinate of used oil, obtained in commercial plant, where the whole first reactor was packed with hydrodemetallization catalyst.

Table 2. Metal Content of Hydroraffinates

Results given in Table 2 show effective demetallization of feed used, though the amount of hydro-demetallization catalyst was lowered 2.5 times in conditions specified in example 1 , in relation to classic catalytic system used in industry.

Additionally one should take into consideration that metal can catalyze the oxidation process, so their effective elimination is relevant for used oil refining.

Example 2

Conditions were the same as in example 1 , only average bed temperatures

(WABT) in both reactors were changed, 330 °C in first and 320 °C in the sec- ond reactor. The product obtained was of celadon-yellow colour, was clear and without coagulums. Chosen properties of hydroraffinate are given in Table 3.

Example 3

In comparison with example 1 the space velocity was lowered from 0.5 h^"1 to 0.35 h^"1. in relation to the whole volume in the second reactor. Chosen properties of hydroraffinate without coagulums are given in Table 3. Yields of hydroraffinates obtained in examples 1 to 3 are in the range of 94 ÷ 98 %.

Next two examples are given to show the difference between the catalytic system used in the process according to the invention, where one receive clear hydroraffinate without coagulums, and known systems giving hydrorafined turbid hydroraffinate containing coagulums.

Example 4 (comparative)

In the first reactor, bed containing hydrodemetallization catalyst was used. In the whole second reactor, hydrofinig catalyst was used. Before starting, investigation catalysts were sulphurized. In both reactors average temperatures of catalyst beds (WABT) were used, respectively 365 °C and 300 °C. Feed space velocity (in relation to the whole bed in the second reactor) was 0.5 h^"1, with H₂/feed volumetric ratio of 1000 and at the pressure at the inlet to the first reactor of 6.0 MPa. Feed to the hydrofining was the same feed as used in the example 1. As a result of the process used, turbid product containing coagulums was received (Table 3).

Example 5 (comparative)

In the first reactor, beds differing from beds used in examples 1 , 2 and 3, and from used in the example 4 known bed, were used. In this example, bed consisted of hydrodemetallization catalyst 5 % (VTV) and hydrofining catalyst 95 % (VTV). Moreover, in the second reactor only the hydrofining catalyst was used. Before starting the process catalysts were sulphurized. Average bed temperatures (WABT) were used in both reactors, respectively 330 °C and 320 °C. Feed, its space velocity and volumetric ratio H₂feed were the same as in example 4. As a result of hydrofining process carried out, turbid product containing coagulums was received (Table 3).

Table 3. Some properties of received oils

Presented invention is especially suited for application in existing plants of used oils hydrofining process, preceded by preliminary contaminants and water sedimentation, and/or chemical treating of received feed (e.g. with sodium hydroxide), and/or preliminary topping of light contaminants, and then by vacuum distillation.

Claims

Patent claims

1. Method of used oils processing where feed is subject to mechanical contaminants and water elimination, and/or chemical treating, and/or light contaminants elimination, and/or vacuum distillation, and/or fractionation and then to catalytic treatment in presence of hydrogen characterized in that it is carried out in two stages at average temperature (WABT) of 300 to 350 °C, and preferably 320 to 340 °C, with hydrogen to feed ratio for the whole process from 700 to 1600 (VA/), and preferably from 1000 to 1500 (VA/), and in the first stage the feed containing used oil undergoes hydrodemetallization, in presence of NiMo/AI₂O₃ type catalyst, and then the first hydrofining in presence of NiMo/AI₂O₃ type catalyst, further, in the second stage the feed undergoes catalytic deparaffination in presence of nickel containing catalyst deposited on ZSM-5 zeolite, and then the second hydrofining in presence of second hydrofining catalyst of NiMo/AI₂θ3 type, and that hydrodemetallization catalyst contains, before sulphuhzation, from 10 to 14 % (m/m) of molydenum as MOO₃ and from 2 to 5 % (m/m) of nickel as NiO, and first and second hydrofining catalyst contains, before sulphuhzation, from 15 to 22 % (m/m) of molybdenum as MOO3 and from 2.5 to 6 % (m/m) of nickel as NiO, and hydrodeparaffination catalyst contains from 3 to 7 % (m/m) of nickel, and furthermore that in the whole process space velocity (LHSV), counted in relation to the total volume of catalytic beds used in the second process stage is from 0.2 to 2.0 h^"1, and preferably from 0.3 to 1.0 h^"1, but feed space velocity (LHSV) in relation to the hydrodeparaffination catalyst bed is from 0.5 to 3.5 h^"1, and preferably from 1.2 to 2.5 h^"1.

2. Method according to claim 1 characterized in that temperature control of the second process stage is carried out by hydrogen addition at the inlet to the hydrodeparaffination catalyst bed.

3. Method according to claim 1 or 2 characterized in that feed and hydrogen are introduced to the catalytic beds co-currently.

4. Method according to claim 1 characterized in that the first stage of the process is carried out with the volume of hydrodemetallization catalyst from 30 to 60 % (VA/), preferably from 33 to 45 % (VA/), counted in relation to the volume of both catalytic beds used in the first process stage.

5. Method according to claim 1 characterized in that the second process stage is carried out with the volume of hydrodeparaffination catalyst from 20 to 40 % (VA/), preferably from 25 to 35 % (VA/), counted in relation to the volume of both catalytic beds used in the second process stage.

6. Method according to claim 1 or 4 or 6 characterized in that the volume of catalytic beds used in the fist process stage is from 20 to 50 % (VA/), preferably from 25 to 40 % (VA/), of total volume of all catalytic beds in the whole process.