GB2462054A

GB2462054A - Biodiesel

Info

Publication number: GB2462054A
Application number: GB0807863A
Authority: GB
Inventors: Knut Grande; Per Aksel Skjolsvikl; Geir Remo Fredriksen
Original assignee: Statoil ASA
Current assignee: Equinor ASA
Priority date: 2008-04-29
Filing date: 2008-04-29
Publication date: 2010-01-27
Also published as: GB2462054A8; GB0807863D0

Abstract

A process for the formation of biodiesel where a crude marine oil is degummed to remove phosphorus catalyst poisons (e.g. phospholipids). The degummed marine oil is then mixed with a mineral oil and this mixture is hydrotreated in the presence of hydrogen and a hydrotreating catalyst such as a Ni/Mo catalyst. The hydrotreated mixture is isomerised in the presence of an isomerisation catalyst such as a TON or MTW zeolite. Optionally the degumming can be excluded and the marine oil is then mixed directly with the mineral oil and hydrotreated.

Description

Biodiesel This invention relates to process for the production of biodiesel from crude marine oil, in particular to a process for eliminating catalyst poisons from marine biomass which is to be used in the formation of biodiesel.

There is increasing World concern about climate change and hence carbon dioxide emissions. In Europe at least, measures are now being taken at the highest level to try to reduce carbon dioxide emissions in all walks of life. This means a heavier reliance on renewable energy sources such as solar and wind power, increasing taxation on energy inefficient products and more investment in harnessing the power of the sea. A furthàr quickly developing field is biofuels, especially for vehicles.

The biofuels directive of 2003 (Directive 2003/30) established an indicative target value of 5.75 % market share for bio-fiiels at the end of 2010. The reference value is based on the energy content of the fuel, and each member state is to set national targets. In the Energy and Climate Package and the related Renewable Energy Roadmap published on 10 January 2007, the European Commission proposes a minimum binding 10% target of biofuels for vehicle use to be reached in the EU by 2020.

The use of flexifuel vehicles, which run on alcohol, in particular ethanol (and also methanol), are already well known. Ethanol can be produced from sugar cane and is frequently used in blends with gasoline to form a biofuel (E5, E85). Methanol is however toxic and is not an ideal material for the mass market, its use currently being confined therefore to racing vehicles.

The industry has therefore being considering ways in which other biomasses can be incorporated into both gasoline and diesel.

Components for diesel fuel can be prepared in various ways but the major diesel components are manufactured using a hydrotreating/isomerisation process where a mineral oil feed is treated with a Ni/Mo or Co/Mo type catalyst (i.e. a hydrogenation, hydrodeoxygenation and hydrodesuiphurisation step) before being subjected to isomerisation in the presence of a zeolite type catalyst. Such a process is well known and carried out industrially around the globe. The hydrotreating step f V involved is designed to remove contaminants such as oxygen, sulphur and nitrogen from the oil and also serves to hydrogenate certain compounds in the mineral oil, such as condensed ring aromatics, which are unacceptable in the final fuel. The isomerisation step causes the hydrocarbons to rearrange or crack so that as many hydrocarbon components as possible have a boiling point within the diesel fuel range (typically 221 to 360°C).

To introduce a biodiesel element into a diesel fuel, it is known to add to a conventional mineral oil a biomass component. Vegetable oils such as rape seed oils are currently the most common biomass added to biofuels. In US 2006/0186020 the hydroconversion of a mixture of vegetable oil and mineral oil is described to form a biodiesel material. A similar disclosure is made in W02004/022674. In must be remembered however that hydrotreating and isomerisation processes described in these and other state of the art documents were originally optimised to deal with mineral oil feeds alone. The catalysts used were not intended to be used in the presence of biomass and the conditions of reaction have been optimised for mineral oil treatment.

Currently, biofuels mostly contain methanol added after cracking or plant derived biomass but vegetable oils and the like are not the only sources of suitable biomass for cracking. Animal fats and fish oils are also capable of providing oils for biofuels. There are however, structural differences between vegetable oils and animals fats/fish oils, typically concerning the unsaturation of the carbon chains in the fat which makes their use potentially harder than plant biomass. Animal and fish oils tend to comprise more unsaturation which could affect cracking.

Of more significance still, animal and fish derived biomass contain higher levels of compounds which are poisons to catalysts used in the mild hydrocracking process. Marine oils may contain quite high levels of heavy metals. Some of these heavy metals are poisonous to the catalysts conventionally used in mild hydrocracking so the use of marine oils has not been exemplified in the art, potentially for this reason. The inventors have realised that mild hydrocracking units processing at least some heavy oil, i.e. atmospheric or vacuum resids already have most of these metals present in the feed to the unit. Such units are therefore already using catalysts which can inherently tolerate certain amounts of heavy metals. The inventors have further realized that when blending a marine oil, e.g. less than 50 %, more preferably less than 30 % marine oil, which inherently contains heavy metals, with a mineral oil feed which also contains such metals, the level of heavy metals in the blend will not change significantly. The present invention therefore has particular relevance in mild hydrocracking units processing at least some heavy oil, i.e. atmospheric or vacuum resid. The inventors have found a particular catalyst combination which works well for heavy oil/marine oil containing feeds.

Moreover, the inventors have realised that marine based oils contain phosphorus compounds. Phosphorus compounds are catalyst poisons and their presence may force the regular regeneration of the NiMo/CoMo catalyst used in hydrotreating. The present inventors have realised therefore that their removal is vital.

EP-A-13 96531 suggests removing phosphorus compounds by removing phosphorus after the hydrotreating step, the idea being that the NiMo/CoMo catalyst is sufficiently resistant to the phosphorus poison that its presence is not a problem.

The critical feature is to ensure that the phosphorus is removed before the isomerisation step begins as the zeolites used in that step are exceedingly sensitive to poisons.

Thus, in EP-A-1396531, the inventors teach that the biomass should be exposed to the NiMo/CoMo catalyst and then stripped before entering the isomerisation stage. The present inventors have detennined however that phosphorus does deactivate the NiMo/CoMo catalyst so it is too late to remove the phosphorus during hydrotreating. The phosphorus should be removed prior to contact with the catalyst at all.

The present inventors realised therefore that, ideally, it is necessary to remove phosphorus from the biomass feed before the mild hydrocracking process can begin. The removal of phosphorus type compounds (such as phospholipids) from biooils, in particular vegetable oils, is called degumming. In a typical degumming process, the oil is washed with aqueous acid, such as phosphoric acid, to cause hydration of phospholipids which, upon hydration, are no longer soluble in the oil but are instead water soluble. The water soluble hydrated phospholipids can then be removed from the oil phase by any suitable technique, e.g. by centrifuge. After removal of the phospholipids, the acidic oil phase is neutralised to return it to neutral pH.

Neutralisation is typically effected using sodium hydroxide. However, the inventors have found that sodium ions are themselves potential poisons to the hydrotreating and zeolite catalysts used in mild hydrocracking. It is envisaged that the use of other metal hydroxides would also have the same problem. Thus, whilst degumming might seem an attractive way of removing the phosphorus based catalyst poisons from the biomass, the degummed biomass may still contain ions which are themselves poisons.

There remains a need therefore to devise a process for removing catalyst poisons from biomass, and in particular crude marine oils, which does not result in the addition of other catalyst poisons to the biomass.

The present inventors have surprisingly found that for marine oils, it is only readily water soluble phosphorus compounds which cause catalyst deactivation. It is not necessary therefore to remove all the phosphorus impurities but rather only those which are water soluble. Such water soluble impurities can be simply removed from the oil by washing with water. A complete degumming process in which the marine oil is acidified and subsequently neutralised is therefore unnecessary and the mild hydrocracking reaction can proceed successfully in the presence of a marine oil which has not undergone a complete degumming reaction. All that is required is that the crude marine feed containing phosphorus based catalyst poisons is washed thoroughly with water as sufficient phosphorus impurities are removed during such a process that the deactivation of the catalysts during mild hydrocracking becomes negligible.

Thus; viewed from one aspect the invention provides a process for the formation of biodiesel comprising: (I) obtaining a crude marine oil and combining said marine oil with a mineral oil to form a mixture; (II) hydrotreating the mixture in the presence of a hydrotreating catalyst; (III) isomeri sing the hydrotreated mixture in the presence of an isomerisation catalyst; -wherein said hydrotreating catalyst is a Ni/Mo catalyst and said isornerisation catalyst is a TON or MTW zeolite.

Viewed from another aspect the invention provides a process for the formation of biodiesel comprising: (11) obtaining a crude marine oil containing at least one phosphorus catalyst poison, e.g. a phospholipid; (II) degumming said crude marine oil; (III) combining the degummed marine oil with a mineral oil to form a mixture; (IV) hydrotreating the mixture in the presence of a hydrotreating catalyst; and optionally (V) isomerising the hydrotreated mixture in the presence of an isomerisation catalyst.

Viewed from another aspect the inyention provides a process for the formation of biodiesel comprising: (I) obtaining a crude marine oil containing at least one phosphorus catalyst poison, e.g. a phospholipid; (II) washing the crude marine oil with water at a pH of from 5 to 8; (III) combining the washed marine oil with a mineral oil to form a mixture; (1Y) hydrotreating the mixture in the presence of a hydrotreating catalyst; and optionally (V) isomensing the hydrotreated mixture in the presence of an isomerisation catalyst.

Viewed from another aspect the invention provides biodiesel made by a process as hereinbefore described.

Viewed from another aspect the invention provides a process for the preparation of biodiesel containing a marine oil component, the improvement -comprising washing the crude marine oil with water at a pH of from 5 to 8.

By biodiesel is meant that the diesel contains a component which is derived from a renewable biological source, in this case a marine oil. -By crude marine oil is meant an oil derived from an marine organism such as a fish, seal, krill etc. The crude marine oil will not have been refined, e.g. degummed and is essentially raw. Crude marine oils are available commercially.

By phosphorus catalyst poison is meant a phosphorus containing compound that acts to deactivate a catalyst used in the hydrotreating andlor isomerisation reaction, e.g. a Ni/Mo or Co/Mo type catalyst or a zeolite. Typically, the phosphorus compound will be a phospholipid and may comprise a fatty acid, usually saturated, a second fatty acid, usually unsaturated, a negatively-charged phosphate group, usually attached to a nitrogen containing alcohol like ethanolamine or an organic compound such as choline.

The crude marine dii can be obtained from any convenient source. Marine oils are those oils which are derived from marine sources such as fish, micromarine organisms (hill and the like) or marine mammals such as seals. In a preferred embodiment the marine oil is a fish oil. Whilst it is preferred if the marine oil derives from a sea based organism, in this invention, the term marine oil is intended to cover freshwater sources of oils.

It is also within the scope of the invention for a mixture of biooils to be employed, e.g. a mixture of plant oil and marine oil, as long as a marine oil is used.

It is also possible of course to mix animal oils with marine oils and so on.

Biooils are often characterised by their free fatty acid content (FFA). Oils with a FFA of less than 1.5 % are regarded as refined and those with an FFA of greater than 20% are regarded as high FFA materials, typically animal fats. The present invention is of particular utility with oils having an FFA of at least 5%, preferably at least 10%.

The crude marine oil is not one which has undergone refinement. Many fish oils are refined to provide a source for allegedly health improving fatty acids such as omega-3 Such refined fish oils are of no interest in this invention as the cost of the refined oil is too high for use in the great bulk required to manufacture a useful amount of biodiesel. Thus, the marine oil used should be unrefined and used essentially in the form it is isolated in from the marine source. Marine oil, especially fish oil, is a known waste product from the fish industry and this waste product, in unrefined state provides the ideal starting material for the process of the invention.

The process of the invention requires that the marine oil component is mixed with a mineral oil component before being hydrotreated. This is conveniently achieved by premixing the marine oil and mineral oil and adding these to the hydrotreatment apparatus together. It will be appreciated however that mixing could occur in the reactor itself and hence the mineral oil and marine oils could be added via separate addition points. It will also be appreciated that the process of the invention is likely to be carried out continuously in that new feed will be added to a reactor in which there is already a hydrotreating reaction occurring. This also falls within the scope of the invention.

The relative amounts of marine oil added relative to the mineral oil feed can vary over a wide range as long as the resulting biodiesel product can function successful in the combustion engine. Preferably however, the amounts range from 0.5 to 50 wt% marine oil, preferably I to 20 wt% marine oil, especially 3 to 15 wt% marine oil, e.g. 5 to 10 wt% marine oil.

By mineral oil component (also termed the hydrocarbon feedstock herein) is meant a component which is derived from crude oil; The mineral oil/hydrocarbon feedstock on which the process above operates can be any suitable feed, e.g. any distillate oil. Preferably however, the feed comprises light andlor heavy gas oils, (especially straight run light or heavy gas oils of crude oil), vacuum distillates, vacuum gas oil, coker gas oil, light cycle oil and materials which are produced during coking, e.g. delayed coking or fluid catalytic cracking. The use of light gas oil or heavy gas oil, especially straight run light gas oil or straight run heavy gas oil is especially preferred.

The boiling point of the mineral oil feedstock may be in the range from 150 to 550°C, in particular 250 to 450°C, preferably 280 to 4 10°C. The density of the hydrocarbon feedstock may be greater than 845 kg/rn3, e.g. greater than 860 kg/rn3.

The sulphur content of the hydrocarbonfeedstock may be at least 500 ppm, preferably at least 750 ppm, especially at least 1000 ppm (by weight).

The nitrogen content of the hydrocarbon feedstock may be at least 150 ppm, preferably at least 200 ppm (by weight).

The initial cetane index (D4737/90) for the hydrocarbon feedstock may be 45 to 51.

The hydrocarbon feedstock may comprise at least 20% aromatics, e.g. at least 25 % aromatics, such as 25 to 70 wt% aromatics, e.g. at least 28 wt% aromatics, such as at least 35 % aromatics. The hydrocarbon feedstock may comprise up to 20 wt% monoaromatics, up to 10 wt % diaromatics and up to 5 wt % triaromatics.

Once mixed with the marine oil, the mixed feed may have a density of at least 0.860 kg/i, preferably at least 0.865 kgIL. The cetane number may be in the range 45 to 50. Thus, the mixture of marine oil and mineral oil has a lower cetane number but higher density than the mineral oil alone.

In the process of the invention the bio oil containing feed is hydrotreated and isomerised. These processes are known in the art.

An ideal reactor set up may involve addition of the marine oil and hydrocarbon feedstock with hydrogen rich treat gas to the reactor, i.e. it is preferred if addition of the hydrogen and feedstock occur through the same reactor inlet.

Whilst it would be possible to feed these separately, mixing them is preferred. In a further preferred embodiment, the feed or feeds to the reactor are preheated, preferably to a temperature similar to that of the reactor at the inlet point. Thus, if the reactor temperature is 350°C at the inlet point, then the feed should be heated to approximately this temperature prior to its a dition to the reactor.

Preheating of the feed can be achieved using an external heat source but ideally it is effected by heat exchange with the reactor effluent stream. Should heat exchange not heat the feed sufficiently, external heating means can be used to supplement the preheating process.

As the reactor feed passes through the reactor and hence over the catalyst in the reactor, it is preferred if the temperature increases through the reactor, i.e. from inlet to outlet. The temperature increase through the reactor may be at least 20°C, e.g. at least 30°C.

Where the reactor contains a plurality of catalyst beds, i.e. the feed passes over more than one catalyst bed between the inlet and reactor outlet, it is possible to cool the reactor between beds by the introduction of a quench gas, typically hydrogen. This not only cools the reactor but provides further hydrogen for hydrogenation.

The hydrotreating catalyst preferably comprises one or more metal components and is conventional in the art. The hydrotreating catalyst preferably comprises a metal of group VIB, such as Cr, Mo and W, and a metal of Group VIII, such as Co and Ni. The metals can be provided in any suitable form such as an oxides, sulphides, nitrates or organic salts. Suitable organic salts include, for example, metal carboxylates, such as formates, acetates, oxalates etc., metal alcoholates and acetylacetonates and the like.

Especially preferably, the hydrotreating catalyst comprises Ni-W or Ni-Mo.

Ni may be provided in its 2+ oxidation state via its nitrate with tungsten being provided via a metatungstate salt, e.g. an animonium salt. The hydrotreating catalyst may be supported as is known in the art, e.g. using an inert support such as alumina, silica or silica alumina. Preferably, the same material is used for the support in the bydrotreating catalyst and the zeolite catalyst binder. Especially preferably, both catalyst systems are carried on the same support.

The amounts of metal present in the hydrotreating catalyst may vary within well known limits. Preferably however the amount of Group VIB component may be in the range 2 to 50 wt%, e.g. 5 to 20 wt%, and the amount of Group VIII component in the range I to 10 wt%, e.g. 3 to 8 wt % based on the weight of the catalyst composition as a whole (i.e. based on the total weight of hydrotreating and hydrocracking catalyst). In a most preferred embodiment the hydrotreating catalyst is a NiIMo catalyst.

Suitable zeolite catalysts for use in the isomerisation step are also well known in the art. Zeolites are three-dimensional (tecto-) silicates which are also called molecular sieves. Zeolites have a porous three-dimensional structure comprising linked oxygen tetrahedra arranged around a cation. A precise definition of zeolites according to the International Mineralogical Association is to be found in: D.S. Coombs et al., The Canadian Mineralogist, vol. 35, p. 1571-1606 (1997).

The zeolite used herein may be a zeolite of the faujasite structure type, i.e. a Y zeolite. Preferably, the Y zeolite is modified and is preferably at least partly, e.g. completely, in the so-called H form or partly, e.g. completely in the ammonium form. It is especially preferably a USY zeolite. The Y zeolite may have a Si/Al ratio in the rangeofl to 25.

Alternatively, the zeolite is a fibrous zeolite substantially comprising non-crossing one-dimensional channels. Preferably this zeolite should consist essentially of non-crossing one-dimensional channels, e.g. consist of non-crossing one-dimensional channels. Thus, it is preferred if substantially all of the channels in the fibrous zeolite are non-crossing one-dimensional channels. It is also preferable for the channels to be at least 8-ring channels, even more preferably at least 1 0-ring channels, and most preferably at least 1 2-ring channels. This may increase further the yield of cyclic paraffins into non-cyclic paraffins during the mild hydrocracking process.

Preferably, any zeolite is in the H-form.

Preferred fibrous zeolites in the context of the present invention are the following, which are named by the three-letter code of the International Zeolite Organization (for further examples see http:/fwww.iza-online.org/: Zeolites based on the following three letter codes could be used: ABW, AEL, AET, AFI, AFO, AHT, ASV, ATh, ATO, ATY, AWO, AWW, BCT, BIK, CAN, CAS, CFI, CHI, CZP, DON, ESV, EUO, GON, IFR, JBW, LAU, LTL, MAZ, MOR, MTF, MU, MTW, NPO, OFF, OSI, PAR, PON, RON, RTE, SAS, SFE, SFF, SFH, SFN, SSY, STF, TON, VET, VFI.

Preferred structures are TON and MTW. Specific zeolites of interest include ZSM-22 and ZSM-12.

It is also within the scope of the invention for a mixture of isomerisation catalysts to be used, e.g. a mixture of (I) a zeolite which has a faujasite structure; and (II) a fibrous zeolite which substantially comprises non-crossing one-dimensional channels.

During hydrotreatment, it is normal for the feed to be hydrogenated, desulphurised and denitrogenated in one step.

Once the desuiphurisation, hydrogenation and isomerisation have occurred the reactor effluent may be cooled and mixed with wash water before further cooling, e.g. by air cooler or other heat exchange, to the required separator temperature. In the separator sour water, reacted feedstock and gas may be separated. Sour water may routed back to the sour water system, the gas (hydrogen) may be recycled to the reactor and the reacted feedstock is sent to a product stripper where light products, such as hydrocarbon gases and naphtha, are sent overhead and the gasoil product is taken out as the bottom product.

The gas is typically sent to H2S recovery, the naphtha to further processing or to product tankage, and the gasoil product is sent to product tankage for subsequent use in diesel fuel.

In a preferred aspect of the invention, a stripping step can be avoided.

The process of the invention is carried out under particularly mild conditions and this is a further aspect of the invention. In particular low pressures can be employed. Low pressures mean a more economic process and are highly desirable.

The process of the invention preferably occurs at a temperature of from 250 to 500°C, preferably 300 to 450°C, especially 300 to 400°C. The pressure is less than 100 barg but preferably at least 10 barg, e.g. 40 to 100 barg, such as 45 to 60 barg. Barg is gauge pressure, i.e. the pressure measured in bars on a pressure gauge (thus relative to the ambient pressure).

Suitable hydrogen to feedstock ratios may be at least 75 Ni/i, e.g. 100 to 1500 Ni/i, preferably 150 to 500 Ni/i. (The unit Ni/i represents normal litre hydrogen at 0°C and 1 atm pressure per litre feedstock). The liquid hourly space velocity (LHSV) may be between 0.3 to 5/h, e.g. 0.5 to 2/h.

Whilst the process of the invention minimises catalyst deactivation caused by poisons from the marine oil, the catalyst will still deactivate slowly as is normal in hydrotreating reactions. The catalyst can be regenerated by conventional techniques, e.g. by burning off any coke which forms on the catalyst composition.

The product of the process as hereinbefore defined has a much lowered sulphur content relative to the feedstock. Sulphur contents in the hydrocarbon product which exits the ring opening reactor can be less than 50 ppm, e.g. less than ppm, especially less than 10 ppm. The amount of sulphur present in the hydrocarbon product can be reduced further by increasing the operating temperature.

The invention also effects denitrogenation of the feedstock. Levels of less than 10 ppm in the product can be achieved, e.g. less than 2 ppm. For straight-run HGO as an example, the nitrogen levels in the feedstock may be of the order of 250 ppm which reduces to less than 2 ppm after hydrotreating.

After the process of the invention, the boiling point of the majority (i.e. at least 50 wt%) of the hydrocarbon product, i.e. the ring opened feedstock, should be in the range from 150 to 360°C, preferably at least 60 wt%.. Preferably, at least 90% of the product, especially 95% of the product is. formed from hydrocarbons having a boiling point below 3 95°C, preferably below 3 80°C, especially below 360°C.

The amount of naphtha component (i.e. liquid components boiling below 150°C) produced during the process should be less than 40% wt, preferably less than % wt, especially less than 15% wt, most especially less than 10 wt% of the product. Such naphtha can of course be isolated and used as is known in the art.

The amount of hydrocarbon gas produced (i.e. C1-C4 fraction) is also minimised, e.g. to less than 5 wt%. Again, these gaseous products can be isolated and used as is known in the art. The inventors have surprisingly found that the addition of marine oil to a hydrotreating process yields much higher levels of propane than are reported with mineral oil feeds alone. Propane is not a constituent of diesel so this needs to be isolated (by well known conventional separation techniques) from the diesel fraction but can be used in many industrial processes either as a fuel, diluent or to make propene.

The density reduction achieved using the process of the invention from feedstock to ring opened product is preferably at 0.10 kg/L. This reduction is preferably achieved relative to the formed product even after the naphtha and gas fractions are removed..

Surprisingly, despite the combination of marine oil and mineral oil having a higher density than the mineral oil alone, the resulting treated feedstock has a lower density than that of the similarly treated mineral oil. The overall density reduction is thus much more marked for the mixed feed of the invention.

The density of the hydrocarbon product is preferably less than 855 kg/rn3 especially less than 852 kg/rn3. Whilst the density can be reduced further by increasing the temperature of the process this also results in increased naphtha production. -The amount of monoaromatics in the product stream can be reduced to less than 15 wt%, the amount of diaromatics to less than 2 wt% and the amount of triaromatics to less than 0.5 wt% using the process of the invention, especially for a heavy gas oil feedstock. The total aromatic content may therefore reduced to less than 17.5 wt%.

In addition, the naphthenes content of the product (i.e. cyclic aliphatic hydrocarbon content) may be greater than 45 wt%.

The cetane number of the cracked product is preferably greater than 51, especially greater than 53. Surprisingly, the inventors have found that the addition of the marine oil to the mineral oil gives rise to a diesel component with a higher cetane rating than that produced using the mineral oil alone. This is despite the mineral oil feed having a higher rating than the mixed feed. As higher cetane rating means a cleaner fuel and hence lower emissions, the invention has the double benefit of using renewable biomass as a fuel source and forming a cleaner burning fuel.

It is a particular advantage of the present invention that Cl 5-18 paraffins become branched and therefore provide excellent cold flow properties.

The product can be fractionated or passed to further reactors for further treatment as is desired. It is also possible to recycle heavy fractions back into the isomeriser. Preferably however, the hydrocarbon product stream, after naphtha and gas removal, is suitable for direct use in automotive diesel.

It is preferred.of course if the crude marine oil is degummed prior to hydrotreatment and isomerisation. The crude marine oil inherently contains phosphorus compounds that are potential poisons to the catalysts used in mild hydrocracking. The phosphorus compounds are preferably phospholipids such as phosphatidyicholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidic acid. The phosphorus catalyst poisons are preferably amphiphilic.

Before addition of the crude marine oil to the hydrotreating reactor, the process of the invention preferably requires that the crude marine oil is thoroughly washed in water. It is possible to use an acidic water wash here (e.g. at pH of less than 4), and if an acid wash is used, suitable acids are weak acids such as citric acid and phosphonc acid.

Preferably however, the water wash is carried out at or around neutral pH, e;g. 5 to 8. By avoiding the use of an acid wash, not only is there an obvious economic saving that the acid does not need to be used or transported but there is also the benefit that a later neutralisation step can be avoided.

The washing step is preferably vigorous to ensure that thecatalyst poisons become hydrated and hence removable with the water. The washing step may therefore incorporate stirring or sonication. Moreover, the washing step may last for a considerable period of time, e.g. days. Preferably however, the mixing step occurs at slightly elevated temperature as this encourages hydrate formation and hence allows easier removal of the hydrated phosphorus compounds.

The addition of water at around neutral pH hydrates the polar head of the phosphorus compound and makes the previously oil soluble molecule readily soluble in water.

If however an acid wash has been used it will be necessary to neutralise the acid, e.g. by the addition of a base such as a hydroxide, e.g. NaOH.

Once formed the hydrated material and water can be simply removed from the desired oil phase by standard phase separation techniques. Centrifugation is a preferred method for separating the phases. The resulting oil phase contains a much lower concentration of the catalyst poisons which cause deactivation during hydrotreating and isomerisation.

It is not essential for every phosphorus compound in the crude marine oil to be removed. The inventors have found that any non water soluble phosphorus compounds present in the crude marine oil can be left in the oil as they are not poisons for the catalyst anyway. Moreover, the washing process described herein may not remove all the potentially water soluble phosphorus compounds from the crude marine oil but it removes a sufficient percentage that the resulting washed oil contains too little phosphorus compound to cause meaningful catalyst deactivation.

Thus, the level of water soluble phosphorus compounds in the marine oil after water washing may be less than 50 wt%, preferably less than 25 wt%, more preferably less than 10 wt%, especially less than 5 wt% of the amount present prior to the washing step. The amounts present may be less than 50 ppm, preferably less than 25 ppn.

During the subsequent polymerisation process, the fact that sufficient catalyst poisons have been removed is seen through the fact that catalyst deactivation occurs at approximately the same rate as if the marine oil was not present at all, i.e. at the same rate as with the mineral oil feed alone. During any hydrotreating or subsequent isomensation process, the catalysts used will deactivate slowly over time. A typically rate of deactivation for a bydrotreating catalyst is around 0.75 to 0.9°C per month. The product of a mild hydrocracking reaction is highly dependent on the temperature at which you carry out the reaction. To compare reactions therefore the weight average bed temperature (WABT) needs to be fixed.

A deactivation rate of 0.9°C per month means that after one month, the temperature of a reaction will need to be approximately 0.9°C higher than a the start of the month if the same product is to be produced.

Using the process of the invention, the deactivation rate of the catalyst in the presence of the washed marine oil feed and mineral oil feed should be within 10% of the figure achieved for mineral oil alone, preferably within 5% thereof.

The mild hydro cracking process cannot function if the oil is added to the cracking unit in solid form. It is required therefore that the oil be melted before being added to the cracker. Most marine oils will; of course, be in liquid form in their natural state but some, in particular mammalian oils may present as solids and need to be melted. Melting can be achieved simply by heating the oil to a temperature greater than its melting point, typically 60°C.

The process of the invention can be carried out in a conventional hydrotreating process layout. Figure 1 shows an exemplary process set up. The process can occur in a single step, i.e. hydrogenation, desuiphurisation and isomensation of the feedstock can all occur in the same reaction step or it could be carried out in more than one step.

The hydrotreating catalyst system can be present in a single bed or multiple beds. In a further embodiment, the zeolite catalyst system can be present in one bed with a hydrotreating catalyst present in a separate, preferably earlier bed. The person skilled in the art is able to manipulate the reactor set up to suit his needs.

Hydrogen is added to the hydrotreating step to effect hydrogenation and desuiphurisation of the hydrocarbon feedstock.

The invention will now be described with reference to the following non limiting examples and figures.

Figure 1 shows a typical mild hydrocracking reactor set up. Feed (1) is mixed with hydrogen rich treat gas and preheated to reactor inlet temperature by heat exchange with the reactor effluent stream and by a fired heater (2). The reactor feed reacts over the catalyst in the reactor (3) and the temperature increases through the reactor. The produced exotherm can be.quenched by introduction of quench gas between the catalyst beds if desired. The reactor effluent is cooled and mixed with wash water before further cooling by air cooler or other heat exchange, to the required separator temperature. In the separator (4), sour water, liquid and gas are separated. Sour water is routed to. the sour water system, the gas is recycled to the reactor via the recycle gas compressor (5) and after mixing with fresh H2 makeup from makeup compressor (6), and the liquid is sent to the product stripper (7). In the stripper the light products, that is, gas and naphtha, are sent overhead of the column and the gasoil product is taken out as the bottom product. The gas is sent to H2S recovery, the naphtha to further processing or to product tankage, and the gasoil product is sent to product tankage.

Figure 2 shows that the level of sulphur relative to weight average bed temperature for mineral oil and mixed mineral oillfish oils feeds. In the Figures, the word Fiskeolje means fish oil and LGO stands for light gas oil.

Figure 3 shows catalyst deactivation rate for 5% fish oil/mineral feed.

Figure 4 shows that the product density of the hydrotreated feed material as a function of WABT.

Figure 5 shows cetane number as a function of weighed average bed temperature.

Figure 6 shows the level of propane as a function of reactor temperature.

Examples

General Fish oil was obtained from Scanbio, Lys�ysund, and corresponded to what is denoted raw fish oil, i.e. no refinement of the fish oil has been done. -The mineral oil employed was a light gas oil from a light North Sea Crude.

Example 1

Degumming of fish oil A portion of raw fish oil was vigorously washed with water at neutral pH. The mixture was centrifuged and the water phase discarded. The resulting oil phase was substantially free of water soluble phosphorus compounds.

Example 2

Hydrotreating to form biodiesel In the experiments three different feed compositions were used Mineral oil feed with no addition of fish oil 5:95 wt% mixture of washed fish oil and mineral oil 10:90 wt% mixture of washed fish oil and mineral oil The oil feeds had the following characteristics: __________ Unit LGO +5% +10% Density kg/I 0.8625 0.8655 0.8685 Sulfur Ppm 1020 920 873 CI __________ 50.4 49.8 48.3 IBP °C 245.6 249.5 246.1 5% Recovered °C 261.2 262.2 256.5 10% °C 268.3 268.3 265.8 Recovered ____________ _____________ _________ _________ 20% °C 274.4 274.9 273.3 Recovered ___________ ____________ _________ _________ 30% °C 279.5 280.3 279.4 Recovered ___________ ____________ _________ _________ 40% °C 284.5 285.3 285.1 Recovered ____________ _____________ _________ _________ 50% °C 289.6 291.4 290.9 Recovered ____________ _____________ _________ _________ 60% °C 295.5 297.6 297.6 Recovered ___________ ____________ _________ _________ 70% °C 302.3 304.7 305.3 Recovered ____________ _____________ __________ __________ 80% °C 310.7 313.7 315.8 Recovered ____________ _____________ __________ __________ 90% °C 322.9 330.0 331.3 Recovered ___________ ____________ _________ _________ 95% °C 333 342.4 337.6 Recovered ___________ ____________ _________ _________ FBP °C 341 ________ 339.3 The catalyst used was Axens HR-448 (NiMo).

Hydrotreating Conditions The feeds were treated at a temperature 300 to 3 50°C, pressure 48 barg, hydrogen to oil ratio of 200 Nl/1 and LHSV 1.66 fh in the presence of the catalyst.

Results The results of the hydrotreating reaction are presented in the figures.

Figure 2 shows that the level if sulphur is slightly higher as the amount of fish oil increases but that low levels of sulphur can be readily achieved using appropriate hydrotreating temperatures.

Figure 3 shows catalyst deactivation for 5% fish oil. The deactivation rate is calculated at 0.9°C per month. In contrast, the known deactivation rate for the mineral oil feed alone is 0.83°C per month. The presence therefore of the 5% washed fish oil has negligible effect on catalyst deactivation.

Figure 4 shows that the product density of the hydrotreated feed material follows essentially the same curve irrespective of the presence of the fish oil.

Figure 5 shows cetane number as a function of weighed average bed temperature.

This graph shows the remarkable finding that higher cetane ratings are achieved when a marine oil component is incorporated into the mineral oil feed despite the mixed feed having a lower initial cetane value than the mineral oil alone.

* Figure 6 shows the level of propane as a function of reactor temperature and shows that the use of a marine oil inihe feed increases the amount of propane produced.

Claims

SClaims - 1. A process for the formation of biodiesel comprising: (I) obtaining a crude marine oil containing at least one phosphorus catalyst poison, e.g. a phospholipid; (II) degumming said crude marine oil; (III) combining the degummed marine oil with a mineral oil to form a mixture; (IV) hydrotreating the mixture in the presence of a hydrotreating catalyst; and optionally (V) isomerising the hydrotreated mixture in the presence of an isomerisation catalyst.
2. A process for the formation of biodiesel comprising: (I) obtaining a crude marine oil and combining said marine oil with a mineral oil to form a mixture; (II) hydrotreating the mixture in the presence of a hydrotreating catalyst; (III) isomerising the hydrotreated mixture in the presence of an isomerisation catalyst; wherein said hydrotreating catalyst is a Ni/Mo catalyst and said isomerisation catalyst is a.TON or MTW zeolite.
3. A process for the formation of biodiesel comprising: (I) obtaining a crude marine oil containing at least one phosphorus catalyst poison, e.g. a phospholipid; (II) washing the crude marine oil with water at a pH of from 5 to 8; (III) combining the washed marine oil with a mineral oil to form a mixture; (IV) hydrotreating the mixture in the presence of a hydrotreating catalyst; and optionally (V) isomerising the hydrotreated mixture in the presence of an isomerisation catalyst.
4. Biodiesel made by a process as hereinbefore described.
5. A process for the preparation of biodiesel containing a marine oil component, the improvement comprising washing the crude marine oil with water at apHoffrom5to8.