WO2010049075A2

WO2010049075A2 - Improved hydrotreatment of renewable organic material

Info

Publication number: WO2010049075A2
Application number: PCT/EP2009/007472
Authority: WO
Inventors: Kristoffer Moos; Rasmus Gottschalck Egeberg
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 2008-10-31
Filing date: 2009-10-19
Publication date: 2010-05-06
Anticipated expiration: 2011-04-30
Also published as: WO2010049075A3

Abstract

The present invention relates to a process for the hydrotreating of mineral oil and renewable organic material. The renewable organic material is split into at least two streams. One stream of renewable organic material is combined with the mineral oil after the fired heater and the combined stream is contacted with a first catalyst bed in a hydrotreating reactor. A second stream of renewable organic material is added to the second catalyst bed in the reactor.

Description

IMPROVED HYDROTREATMENT OF RENEWABLE ORGANIC MATERIAL

The present invention relates to a process for the combined hydrotreatment of mineral oil and renewable organic mate- rial, in particular renewable organic material in the form of tall oil or tall oil derived material. More particularly, the invention relates to a process in which the amount of renewable organic material represents 0.1-80 vol% of the combined mineral oil-renewable organic material feed, more particularly 30 vol% . A portion of the renewable organic material feed is directly combined with the mineral oil feed prior to entering the hydrotreating reactor and another portion of the renewable organic material feed is introduced into the reactor downstream the first hy- drotreating catalyst bed.

During the refining of oil feeds, hydrotreating is utilized for the removal of impurities such as sulphur and nitrogen. Hydrocarbon feedstocks and in particular heavy hydrocarbons such oil and diesel usually contain organic sulphur and nitrogen compounds that in subsequent stages represent unde- sired impurities because of their negative effect on catalyst activity. Additionally, environmental regulations impose a demand on the production of extremely clean trans- portation fuels with very low sulphur levels, for instance as low as 10 ppm total sulphur in diesel fuels. The sulphur and nitrogen impurities are therefore hydrogenated during hydrotreatment to hydrogen sulphide and ammonia.

Renewable organic material is an alternative source of energy that can supplement conventional fossil fuels such as mineral oils. Vegetable oils and animal fats consist mainly (typically > 95 wt%) of triglycerides having the following general formula:

The groups Rl, R2 and R3 are aliphatic chains which typically contain 7-24 carbon atoms and 0-3 double bonds. The oils may also contain a fraction of free fatty acids with similar chain lengths and degree of unsaturation . If crude tall oil or tall oil derived material is used, then the feedstock can also contain resin acids. Fatty acid esters obtained e.g. by transesterification of triglycerides with an alcohol, in particular fatty acid methyl esters (FAME) and other oxygen-containing material derived from renewable organic material can also be used as a feedstock and proc- essed similar to raw vegetable oils and animal fats.

In order to use feedstocks derived from renewable organic material in conventional automobile engines it is desirable to convert the material into hydrocarbons that are similar to those present in fossil derived transportation fuels. It has already for a number of years been known how to convert vegetable oils into normal paraffins in the gasoline or di- esel boiling range by employing a hydrotreating process. In this process the renewable organic material is reacted with hydrogen at elevated temperature and pressure in a catalytic reactor.

US Patent No. 5 ,705 ,722 teaches the use of a hydroprocess- ing catalyst to convert a tall oil feedstock into a mixture of compounds, some of which can be used as diesel fuel additives .

US Patent No. 4,992,605 describes the conversion of canola oil, sunflower oil, soybean oil, rapeseed oil, palm oil and fatty acid fraction of tall oil into mainly Ci₅-Ci_S hydrocarbons using a hydroprocessing catalyst at 350-450⁰C. This patent discloses also the use of 50% light cycle oil and 50% canola oil as feed to a hydrotreatment stage.

WO-A-2008/054442 discloses a process for the hydrotreatment of a mixture of a hydrocarbon boiling in the range 27- 538°C, such as gasoline, light cycle oil and vacuum gas oil, and a triglyceride in which the triglyceride repre- sents 2-80 wt% of the mixture. The triglyceride is preferably vegetable oil, yellow grease, animal fats or mixtures thereof.

WO-A-2008/020048 discloses a process for the production of normal alkanes by hydrotreatment in which 50 to 99.5 wt% of the feedstock is vacuum gas oil and the rest is triglycerides or triglyceride-derived molecules including rapeseed oil, soybean oil, canola oil, waste vegetable oil and tall oil. It is mentioned that the oxygenated compounds (triglycerides or triglyceride-derived molecules) are injected at a point downstream from the injection point of the crude oil-derived compounds thereby ensuring a shorter contact time of the more reactive oxygenated compounds with the hydroconversion catalyst. Although it is known to hy- drotreat conventional mineral oil in combination with significant amounts of renewable organic material, current in- dustrial practice involving the hydrotreating of a feed comprising oil and renewable organic material has often been limited to the use of small amounts of the latter, normally as low as 5 vol%. It would be desirable to increase the proportion of renewable organic material in the feed, for instance up to 25 or 30 vol% or higher, but this conveys the penalty of increasing corrosion in pipes, heat exchangers and fired heaters upstream the hydrotreating reactor. Particularly, when using tall oil derived material, which may contain a high content (e.g. 15 wt% or more) of free fatty acids one will be faced with severe corrosion problems. The prior art fails in realizing or at least addressing this aspect which is of utmost importance and which inevitably imposes a limitation on the industrial applicability of the attractive concept of hydrotreating mix- tures of conventional mineral oil with significant proportions, ≥ 25 vol% of renewable organic material such as bio- diesel and particularly tall oil or tall oil derived material .

In addition to this, large amounts of heat are released due to FAME reactions in the hydrotreating reactor thereby deteriorating the hydrotreating catalyst and giving rise to fouling of the catalyst bed.

EP-A-I, 857, 525 and EP-A-I, 693, 432 disclose also the hy- drotreatment of mixtures of vegetable oils and mineral oils. The mixing of the mineral oil and vegetable oil oc- curs downstream the feed/effluent heat exchangers of the hydrotreating unit but upstream the fired heater (oven) which is used to heat the feed to the inlet temperature of the hydrotreating unit.

US-A-20008/0173570 discloses a hydrotreatment process in which a petroleum cut is passed through a first bed of hydrotreating catalyst. Part of the effluent from this first bed is admixed with vegetable oil and then introduced to a second bed of hydrotreating catalyst. Thereby, it is possible to limit the use of hydrogen in order to control the heat release in the first bed, since quenching is provided by the vegetable oil. However, the control of heat release is not sufficient to permit the use of significant amounts of vegetable oil in the process, such as 25 or 30 vol% or more .

WO-A-2008/087279 discloses likewise a method for hydroproc- essing petroleum of the gas oil type and a biological feed- stock, in which the former is introduced into the hydro- processing reactor upstream the biological feedstock.

WO-A-2007/125332 discloses also a process for the hydrohy- drotreating of mineral and organic oil of animal or plant origin. The mineral oil is added upstream of the first bed of a first hydrotreater, while the organic oil is added after the first bed of the first hydrotreater. The organic oil is also injected before the second bed of a second hydrotreater downstream and into the effluent product stream of the first hydrotreater. This conveys the problem of increasing the number of potential corrosion points; yet this problem of corrosion is not addressed. Thus, according to the teaching of this citation several points are needed to inject the organic oil, so that if there is only one hy- drotreating reactor with two beds, the problem is moved from the first to the second bed, which makes it impossible to conduct a so-called skimming where the upper catalyst layer is replaced with a new one in the case of problems. In other words, the teaching of WO-A-2007/125332 cannot be applied in circumstances where operation with a single hy- drotreating reactor containing two catalytic beds is re- quired.

We have now found that by splitting the renewable organic material in several streams and delaying the mixing of conventional mineral oil with renewable organic material prior to hydrotreating, it is possible to increase the proportion of the latter with respect to mineral oil significantly, i.e. up to 80 vol% without risking corrosion of particularly upstream equipment and at the same time it is possible to control the heat release from the exothermic reac- tions and lengthen the lifetime of the hydrotreating catalysts.

Accordingly, we provide a process for the hydrotreating of mineral oil and renewable organic material comprising the steps:

(a) providing a mineral oil feedstock, passing the feedstock through one or more feed-effluent heat exchanger (s) of a hydrotreating reactor and subsequently through a fired heater; (b) providing a renewable organic material feedstock and dividing this feedstock into at least two sub-streams; (c) combining the heated mineral oil feedstock from step (a) with at least one of the sub-streams of renewable organic material from step (b) and contacting the combined stream with a first catalyst bed in a hydrotreating reactor containing at least two fixed beds of hydrotreating catalyst;

(d) contacting at least one of the other sub-streams of renewable organic material from step (b) with a second catalyst bed downstream the first catalyst bed in said hy- drotreating reactor;

(e) passing the effluent from the hydrotreating reactor through the one or more feed-effluent heat exchanger (s) of step (a) .

As used herein the term "renewable organic material" defines vegetable oils, animal fats, tall oil and derived material such as fatty acid alkyl esters, particularly fatty acid methyl esters (FAiME) or combinations thereof, in particular tall oil or tall oil derived material in which the latter represents a composition containing mainly free fatty acids, FAME and resin acids. All of these represent renewable sources. Vegetable oils include rapeseed, soybean, corn, coconut, palm and cotton oils. Animal fats include bacon grease, yellow grease, lard, butter and tallow.

As used herein the term "mineral oil" defines hydrocarbons selected from the group of light gas oil (LGO) , such as light light gas oil (LLGO) , light cycle oil (LCO) , vacuum gas oil (VGO) , heavy atmospheric gas oil, heavy light gas oil (HLGO) and combinations thereof. The term "hydrotreating" or "hydrotreatment" encompasses a range of process requiring the presence of hydrogen, namely hydrogenation, hydrodeoxygenation (HDO) , hydrodecarboxyla- tion, hydrodearomatisation (HDA) , hydrocracking, hydrode- sulfurisation (HDS) and hydrodenitrification (HDN) .

Hydrotreating conditions involve normally operation at temperatures between 200 and 500⁰C and pressures up to 200 bars. Catalysts used in the hydrotreating step are prefera- bly those employed conventionally such as mixed cobalt and/or nickel and molybdenum sulfides supported on alumina and mixed nickel and tungsten sulfides supported on alumina or silica. Other suitable catalysts include those containing ruthenium sulfide and catalysts using novel supports such as silica-alumina, carbons or other materials.

After cooling of the effluent from the hydrotreating reactor in the feed-effluent heat exchanger (s) , the process may further comprise passing the effluent to a hot separator and withdrawing from the hot separator an overhead fraction and a bottoms fraction, then passing the overhead fraction to a cold separator and withdrawing from the cold separator a gaseous overhead fraction in the form of a hydrogen- recycle gas stream.

The hydrogen-recycle gas stream may optionally be passed to an amine wash unit, i.e. a hydrogen sulphide recovery unit in which a solvent (amine) is contacted with said gaseous stream thereby withdrawing from said recovery unit a hydro- gen-recycle gas stream with reduced content of hydrogen sulphide and carbon dioxide. In another embodiment of the invention, the process further comprises combining the mineral oil feedstock of step (a) with hydrogen from the hydrogen-recycle gas stream, a hydrogen make-up gas or a combination of both.

The total amount of renewable organic material is 0.1 to 80 vol%, preferably 25 to 75 vol%, more preferably 30 to 50 vol%, most preferably 30 vol% of the combined volume of renewable organic material and mineral oil. By "total amount of renewable organic material" is meant the amount renewable organic material of this feedstock prior to division into sub-streams, and thus it represents the total amount of this material added to the hydrotreating reactor.

Oil and fats are the main constituents in the human diet and it has therefore been debated whether the production of transportation fuels in so-called first generation technologies can result in food scarcity and higher food prices. It would therefore be desirable to develop tech- nologies that can process other types of feedstocks. Therefore, in a specific embodiment of the invention the renewable organic material is tall oil, more specifically tall oil derived material and the mineral oil is a light light gas oil (LLGO) . Tall oil derived material comprises mainly fatty acids, fatty acid methyl esthers and resin acids. Tall oil is a by-product obtained from paper mills.

In another specific embodiment of the invention the total amount of renewable organic material is up to 30 vol%, preferably 30 vol% of the combined volume of renewable organic material and mineral oil, the renewable organic material is tall oil or tall oil derived material and the min- eral oil is light light gas oil (LLGO) . Since the density of e.g. tall oil or tall oil derived material is typically 900-930 kg/³ and the density of a mineral oil such as LLGO is typically 810-840 kg/m³, the vol% corresponds roughly to the wt%. For instance 30 vol% renewable organic materials, particularly tall oil or tall oil derived material, corresponds to 30-35 wt%.

We found that the paraffins formed by the hydrogenation of the renewable organic material, particularly tall oil or tall oil derived material improves the cetane index and lowers the density of the product, but impairs its cold flow properties. By providing up to 30 vol%, preferably 30 vol% renewable organic material, more preferably 30 vol% tall oil or tall oil derived material, it is possible to not only improving the cetane index, but also still be able to secure a low cloud point in the product (good cold flow properties) .

Preferably, the renewable organic material feedstock is di^¬ vided into only two sub-streams. These sub-streams are often of equal size, i.e. 50 vol% of the renewable organic material in each sub-stream, but other splits such as 25/75 or 75/25 vol% are also possible, where the first number corresponds to one sub-stream mixed with mineral oil. Accordingly, one sub-stream is mixed with the mineral oil feed between the fired heater and the hydrotreating reactor, while the other sub-stream is contacted with a second catalyst bed downstream the first catalyst bed and thereby used as a quench between these catalyst beds of the reactor. A quench ring of a high alloy material such as SS904L may thus be incorporated in between the first and second catalyst beds of the hydrotreating reactor as there is a liquid quench at this point. As a result the mixture of mineral oil and renewable organic material becomes less corrosive since only part of the renewable organic material is mixed with the mineral oil. In addition, the heat release from the exothermic reactions take place in two catalyst beds rather than one, and the liquid quench facilitates a more controlled heat release in the hydrotreating reactor, thereby lengthening the lifetime of the hy- drotreating catalysts. We achieve therefore an improved temperature management through better control of heat release than in for instance US-A-20008/0173570 or WO-A- 2007/125332. Particularly with respect to WO-A-2007/125332 the invention provides the advantages that since the renew- able organic material, especially TOFAME compounds are easy to convert, it is possible with the present invention to obtain a lower inlet temperature in the first catalytic bed of the hydrotreater due to the mixing of a part of the renewable organic material with mineral oil. As a conse- quence, the exit temperature from the first bed is not higher when using renewable organic material than when not using renewable organic material. In addition, the mixing of the mineral oil and renewable organic material is easier to perform before entering the hydrotreater than in between beds in the hydrotreater, the latter requiring the use of special quench ring for liquid and gas. Furthermore, the invention provides a higher hydrogen partial pressure upstream the reactor, preventing gum formation by polymerisation reactions and corrosion.

Moreover, in revamp applications, since the renewable organic material is injected after the fired heater and as a liquid quench to the second reactor bed, the amount of hardware that is subjected to the high-corrosive material is significantly reduced and only minor material changes are necessary.

As indicated above, tall oil derived material is a particularly preferred renewable organic material of this invention. Tall oil derived material contains mainly three fractions, fatty acids, fatty acid methyl esthers and resin ac- ids. The oxygen containing groups in the tall oil derived material can react in two ways in the unit, either by decarboxylation or hydrodeoxygenation (HDO) . A significant part of the tall oil derived material is thus in the form of acids. During decarboxylation the C-atom on which the acid group is attached is removed from the alkane chain and CO₂ is formed. During HDO the C-atom with the acid group is left on the chain, while the oxygen atoms are removed as water. The decarboxylation route uses less hydrogen compared to the HDO route, and may therefore appear to be the preferred reaction route. The CO₂ formed can react with hydrogen, forming CO and in turn methane. Moreover, CO₂ and CO can cause a number of other problems including catalyst inhibition and are more difficult to remove from the recycle gas loop than water. We have found that it is possible to provide modifications of the recycle gas loop in order to handle the formed gases, in particular CO and CO₂. The CO₂ can to a large extent be removed in a down-stream amine wash, but in order to avoid build-up of CO and CH₄ in the recycle gas loop, a purge can be established from which CO in the hydrogen-recycle gas is removed. Accordingly, in another embodiment of the invention a sub-stream is divided from the hydrogen-recycle gas stream obtained from the amine wash unit and this sub-stream subsequently passes through at least one methanation reactor. A purge gas stream containing methane is then withdrawn from the methanation reactor and accordingly from the recycle gas loop. In the methanation reactor CO reacts with hydrogen, forming methane according to the reaction CO + 3H₂ <^> CH₄ + H₂O. The methanation enables also the removal of traces of CO₂ that are present in the recycle gas after the amine wash.

One or more of the catalyst beds may be provided with at least two catalyst sub-beds, in which the top catalyst subbed (s) contain a catalyst active in hydrodeoxygenation (HDO) and hydrodecarboxylation, but with low hydrodesulfu- risation (HDS) activity and the subsequent sub-bed (s) contains a catalyst active in HDS. Since the top sub-bed(s) have activity for HDO and decarboxylation reactions, but have low activity for HDS/HDA it is possible to prevent the temperature gradient over the first catalyst sub-bed(s) from becoming too large and thereby it is possible to further reduce the overall temperature gradient in the catalyst bed.

As used herein the term "catalyst bed" defines a catalyst region within the hydrotreating reactor separated by vapour-liquid trays and with quench regions in between each catalyst bed. The term "catalyst sub-bed" defines a layered region of catalyst, e.g. HDO catalyst, within such catalyst bed.

The same catalyst arrangement within a catalyst bed may also be provided within the hydrotreating reactor itself. Hence, the top two catalyst beds in the hydrotreating reactor may be provided with a catalyst active in hydrodeoxy- genation (HDO) and hydrodecarboxylation and the subsequent bed(s) is provided with a catalyst active in hydrodesulfu- risation (HDS) . Accordingly, below the top two catalyst beds which primarily convert the renewable organic material, additional catalyst beds may be provided which performs hydrodesulphurisation (HDS) reactions on the mineral oil.

Hydrotreating catalysts active for HDO and hydrodecarboxylation are well known in the art and comprise normally nickel and/or molybdenum on a suitable carrier.

The free fatty acids in the tall oil have similar properties as naphthenic acids and are responsible for corrosion in the plant. The acid corrosion is particularly relevant for equipment upstream the hydrotreating reactor such as pipes, feed/effluent heat exchanger (s) and fired heater, as well as in the hydrotreating reactor itself at points near the introduction of the feed containing the renewable organic material.

Accordingly, in yet another embodiment of the invention the mineral oil and renewable organic material in step (c) are combined immediately before entering the hydrotreating reactor, i.e. at injection point farthest away from the fired heater yet upstream the reactor. This enables the reduction in the length of corrosion resistant pipe that must be con- structed to withstand the corrosive effects of the acidic compounds in the renewable organic material. In a further embodiment of the invention the hydrotreating reactor is provided with a lining of stainless steel, such as a cladding of 304L stainless steel, particularly in regions where the feed, either the combined mineral oil - re- newable organic material or the renewable organic material alone is introduced into the reactor. This further minimizes corrosion risks.

Since hydrogen has an inhibiting effect on the corrosion, downstream of the hydrogen injection point with the mineral oil, which is often upstream the feed/effluent heat exchanger (s) of the hydrotreating reactor or downstream the fired heater, it is convenient to use equipment and parts with 300 series stainless steel with sulfidic corrosion re- sistance.

The process of the invention represents an environmentally friendly technology: it gives the important advantage that "green diesel" is produced, while the global food shortage is not negatively affected, since the process is tailored to treat tall oil or tall oil derived material as well as other renewable resources, rather than for instance maize and corn or crops that are used for human nutrition.

In accordance with the appended claims the invention encompasses the following features:

1. A process for the hydrotreating of mineral oil and renewable organic material comprising the steps: (a) providing a mineral oil feedstock, passing the feedstock through one or more feed-effluent heat exchanger (s) of a hydrotreating reactor and subsequently through a fired heater/

(b) providing a renewable organic material feedstock and dividing this feedstock into at least two sub-streams; (c) combining the heated mineral oil feedstock from step (a) with at least one of the sub-streams of renewable organic material from step (b) and contacting the combined stream with a first catalyst bed in a hydrotreating reactor containing at least two fixed beds of hydrotreating cata- lyst;

(d) contacting at least one of the other sub-streams of renewable organic material from step (b) with a second catalyst bed downstream the first catalyst bed in said hydrotreating reactor; (e) passing the effluent from the hydrotreating reactor through the one or more feed-effluent heat exchanger (s) of step (a) .

2. Process according to claim 1, further comprising passing the effluent from step (e) to a hot separator and withdrawing from the hot separator an overhead fraction and a bottoms fraction, then passing the overhead fraction to a cold separator and withdrawing from the cold separator a gaseous overhead fraction in the form of a hydrogen-recycle gas stream.

3. Process according to claim 2, wherein the hydrogen- recycle gas stream subsequently passes through an amine wash unit.

4. Process according to any preceding claim further comprising combining the mineral oil feedstock of step (a) with hydrogen from the hydrogen-recycle gas stream, a hydrogen make-up gas or a combination of both.

5. Process according to any preceding claim, wherein the total amount of renewable organic material is 0.1 to 80 vol% of the combined volume of renewable organic material and mineral oil.

6. Process according to claim 5, wherein the total amount of renewable organic material is up to 30 vol% of the combined volume of renewable organic material and mineral oil, the renewable organic material is tall oil or tall oil derived material and the mineral oil is light light gas oil (LLGO) .

7. Process according to claim 3 wherein a sub-stream is divided from the hydrogen-recycle gas stream obtained from the amine wash unit and said sub-stream subsequently passes through at least one methanation reactor.

8. Process according to any preceding claim, wherein one or more of the catalyst beds is provided with at least two catalyst sub-beds, in which the top catalyst sub-bed (s) contain a catalyst active in hydrodeoxygenation (HDO) and hydrodecarboxylation and the subsequent sub-bed (s) contains a catalyst active in hydrodesulfurisation (HDS) .

9. Process according to any preceding claim, wherein the mineral oil and renewable organic material in step (c) are combined immediately before entering the hydrotreating reactor. 10. Process according to any preceding claim, wherein the hydrotreating reactor is provided with a lining of stainless steel.

The accompanying figure shows a simplified diagram of a process according to a specific embodiment of the invention comprising hydrotreating stage with split of the renewable organic material stream and associated hydrogen recycle loop .

Feedstock stream 1 containing light light gas oil (LLGO) as mineral oil is pumped and heated by passage through feed- effluent heat exchanger 20 of hydrotreating reactor 21 and subsequently fired heater 22. Feedstock stream 2 containing tall oil or tall oil derived material as renewable organic material is split into substreams 3 and 4. Half of the tall oil or tall oil derived material is carried in stream 3 and is combined with the mineral oil after the fired heater 22 to create combined stream 5 which is contacted with a first catalyst bed 23 of hydrotreating catalyst in hydrotreating reactor 21. The other half of the tall oil or tall oil derived material is carried in stream 4 and is used as quench between the first catalyst bed 23 and second catalyst bed 24.

Make-up hydrogen is added as stream 7 to the hydrogen recycle stream 12. The feedstock of mineral oil 1 is mixed with resulting hydrogen recycle stream 6 which is here added be^¬ fore the feed-effluent heat exchanger 20. This hydrogen may also be added after such heat exchanger, for instance upstream the fired heater 22. An effluent 8 containing the diesel product is withdrawn from hydrotreating reactor 21 and then cooled via feed-effluent heat exchanger 20 while the mineral oil feed 1 is preheated. The cooled effluent is then conducted to hot separator 27 where a bottoms fraction 9 is withdrawn while the lighter components containing car- bon monoxide, carbon dioxide, hydrogen sulphide, ammonia, water and other light hydrocarbons are recovered as overhead fraction 10. This overhead fraction is cooled and conducted to cold separator (fractionation unit) 28. From the cold separator a hydrogen-rich overhead fraction 11 is withdrawn and passed to amine wash unit 29. Δ sub-stream 16 is divided from the hydrogen-recycle gas stream 12 obtained from the amine wash unit 29. This sub-stream 16 passes subsequently through methanation reactor 30 in order to obtain purge gas stream 17 thereby avoiding build-up of carbon monoxide and methane in the recycle gas loop. A bottoms fraction 14 is then withdrawn from the cold separator 28. Stream 14 is combined with stream 9 to yield a combined stream 15 containing product diesel for further use as clean renewable transportation fuel, i.e. "green diesel".

Claims

1. A process for the hydrotreating of mineral oil and renewable organic material comprising the steps: (a) providing a mineral oil feedstock, passing the feedstock through one or more feed-effluent heat exchanger (s) of a hydrotreating reactor and subsequently through a fired heater;

(b) providing a renewable organic material feedstock and dividing this feedstock into at least two sub-streams;

(c) combining the heated mineral oil feedstock from step (a) with at least one of the sub-streams of renewable organic material from step (b) and contacting the combined stream with a first catalyst bed in a hydrotreating reactor containing at least two fixed beds of hydrotreating catalyst;

9. Process according to any preceding claim, wherein the mineral oil and renewable organic material in step (c) are combined immediately before entering the hydrotreating re- actor.

10. Process according to any preceding claim, wherein the hydrotreating reactor is provided with a lining of stainless steel.