CN107922852B

CN107922852B - Process for preparing paraffins and waxes

Info

Publication number: CN107922852B
Application number: CN201680050904.2A
Authority: CN
Inventors: G·L·贝泽梅; H·博里格特; H·M·谭
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2015-09-04
Filing date: 2016-09-01
Publication date: 2020-11-10
Anticipated expiration: 2036-09-01
Also published as: MY191351A; CN107922852A; US20180258354A1; EP3344730A1; WO2017037177A1; ZA201801287B

Abstract

The present invention relates to a process for the preparation of paraffins and waxes from a gas mixture comprising hydrogen and carbon monoxide in at least two conversion reactors being a first reactor and a second reactor, said reactors comprising a catalyst, said process comprising at least the following steps: (a) providing the gas mixture to one or more conversion reactors; (b) catalytically converting the gas mixture of step (a) under initial reaction conditions to obtain an initial fischer-tropsch product comprising paraffins having from 5 to 300 carbon atoms; (c) combining the initial fischer-tropsch product streams from each of the at least two reactors of step (b) to obtain a combined fischer-tropsch product stream; (d) subjecting the combined fischer-tropsch product stream of step (c) to a hydrogenation step to obtain a hydrogenated fischer-tropsch product stream; (e) separating the hydrogenated fischer-tropsch product stream of step (d) thereby obtaining at least a fraction comprising 5 to 9 carbon atoms, a fraction comprising 10 to 17 carbon atoms and a fraction comprising 18 to 300 carbon atoms; (f) separating the hydrogenated fraction comprising 18 to 300 carbon atoms in step (e) to obtain one or more light waxes having a congealing point in the range of 30 to 75 ℃ and heavy waxes having a congealing point in the range of 75 to 120 ℃, wherein subsequently the relative concentration of the fraction comprising 5 to 9 carbon atoms, the fraction comprising 10 to 17 carbon atoms, the concentration of light waxes and the concentration of heavy waxes is varied by increasing, decreasing or maintaining the reaction temperature of at least one of the reactors.

Description

Process for preparing paraffins and waxes

Technical Field

The present invention relates to a process for the preparation of paraffins and waxes from a gaseous feed stream comprising hydrogen and carbon monoxide in at least two conversion reactors as a first reactor and a second reactor, said reactors comprising a catalyst.

Background

Paraffins and paraffins may be obtained by various processes. US 2,692,835 and EP2655565 disclose a process for obtaining paraffins and paraffins from crude oil. Furthermore, paraffins and paraffins may be obtained using the so-called fischer-tropsch process. An example of such a process is disclosed in WO 2002/102941, EP 1498469, WO 2004/009739, WO 2013/064539 and WO 2014095814.

The fischer-tropsch process may be used to convert synthesis gas to liquid and/or solid hydrocarbons. Synthesis gas may be obtained from a hydrocarbonaceous feedstock by a process wherein the feedstock, e.g. natural gas, associated gas and/or coal bed methane, heavy and/or residual oil fractions, coal, biomass, is converted in a first step into a mixture of hydrogen and carbon monoxide. Such a mixture is commonly referred to as synthesis gas or syngas. The synthesis gas is then fed to a reactor where it is converted in one or more steps over a suitable catalyst at elevated temperature and pressure by the actual fischer-tropsch process into paraffinic compounds and water. The obtained paraffinic compounds range from methane to high molecular weight modules. The high molecular weight module obtained may contain up to 200 carbon atoms, or in particular cases even more. Many types of reactor systems have been developed for carrying out the fischer-tropsch reaction. For example, fischer-tropsch reactor systems include fixed bed reactors, particularly multi-tubular fixed bed reactors, fluidized bed reactors, such as entrained fluidized bed reactors and fixed fluidized bed reactors, and slurry bed reactors, such as three-phase slurry bubble columns and ebullated bed reactors.

Catalysts for fischer-tropsch synthesis typically comprise a support-based support material and one or more metals from groups 8 to 10 of the periodic table, in particular the cobalt or iron group, optionally in combination with one or more metal oxides and/or metals selected from zirconium, titanium, chromium, vanadium and manganese, in particular manganese, as promoters. Such catalysts are known in the art and have been described in e.g. specifications of WO 9700231a and US 4595703.

One of the limitations of the fischer-tropsch process is that the activity of the catalyst decreases over time due to a number of factors. The activity of the catalyst is reduced compared to its initial catalytic activity. The initial activity of the catalyst may be its activity as prepared. Catalysts which show a decrease in activity after use in the fischer-tropsch process are sometimes referred to as deactivated catalysts, although they still usually show activity. Such a catalyst is sometimes referred to as a deterioration catalyst. The catalyst may sometimes be regenerated. This may be done, for example, with one or more oxidation and/or reduction steps.

After regeneration, the catalyst generally exhibits an activity lower than that of the catalyst as prepared. In particular, after a number of regenerations, it has generally proved difficult to restore activity levels comparable to those of the catalysts just prepared. In order to be able to use the catalyst for a long time, it may therefore be desirable to start the fischer-tropsch process with fresh catalyst having a relatively high activity.

The use of fresh or rejuvenated catalysts with relatively high initial activity may have disadvantages. This is particularly the case when the amount of catalyst used in the reactor tubes is fixed after loading the catalyst in the reactor tubes. One example of a reactor tube packed with a fixed amount of catalyst is a reactor tube packed with a packed bed of catalyst particles.

In a fischer-tropsch process with a catalyst having a relatively high initial activity, the activity of the catalyst is particularly high at the start of the process. Furthermore, because of the high activity of the catalyst, large amounts of water are produced in the fischer-tropsch hydrocarbon synthesis, resulting in a high relative humidity at the start of the fischer-tropsch process. During start-up of a fischer-tropsch reactor with a very active catalyst, the reaction temperature is usually kept at a relatively low value, e.g. below 200 ℃, to avoid too high a product yield and a concomitant large temperature rise due to the exothermic reaction.

Because the catalyst deactivates over time, the temperature of the reactor must be increased. The increase in temperature in the reactor leads to an increase in the activity of the catalyst. By increasing the temperature, the activity of the aged catalyst can be partially compensated.

The higher operating temperature of the "end of run" (EOR) catalyst results in lower C5+ selectivity and light wax. On the other hand, the very beginning (start of run (SOR)) catalyst operation results in high C5+ selectivity and heavy wax. The relationship between operating temperature and selectivity of a catalyst is for example described in Fischer-Tropsch and related synthesis, h.h.storch; columbic; anderson, John & Wiley parent-child publishing company (John Wiley & Sons, Inc.), new york, 1951, is described on page 217. The term "light wax" means that the heavy wax C40+ fraction rarely tails to longer chains. The term "heavy wax" means a C40+ fraction that is tail to long chain number.

The hydrocarbon product stream obtained after fischer-tropsch synthesis comprises mainly paraffinic compounds ranging from methane to high molecular weight molecules. Of the products in this range, the lighter fraction (i.e., methane (C1) through butane (C4)) is the most undesirable fraction of the product stream, and the heavier fraction is the more desirable fraction of the product stream. For paraffin and wax production, the most valuable are hydrocarbons in the range from C5 to C41+ (C stands for carbon chain length). The lighter part of the product stream is typically recovered from the product stream as a tail gas and may be reused upstream of the fischer-tropsch process (e.g. in synthesis gas production).

Several processes are known to increase the yield of paraffins and waxes comprising hydrocarbons in the C10 to C40 range of the product stream obtained from the fischer-tropsch reaction. For this desired portion of the product stream, the catalyst formulation can be varied and a catalyst selected having an improved yield. The relationship between the catalyst formulation and the increased yield of this catalyst due to the change in formulation is described, for example, in applied Catalysis A (applied Catalysis A), 161(1997), pages 59-78. Once the catalyst is selected, the distribution is largely fixed. Moreover, even if the same catalyst is used, by varying the CO, H2 and inert gas in the gaseous stream towards the reactorRelatively small variations in the concentration of the body can also be achieved. Partial pressure and H₂The effects of/CO on activity and methane selectivity are described, for example, in industrial and engineering chemistry research (ind. eng.chem.res.) 2005,44, pages 5987-5994 and Fischer-Tropsch and related synthesis, h.h. store; columbic; R.B. Anderson, John&Willi parent-child publishing company (John Wiley)&Sons, Inc.), new york, page 330 and page 370-372 of 1951. Finally, the operating temperature of the catalyst can be varied. The effect of temperature on product distribution is described, for example, in Fischer-Tropsch and related syntheses, h.h.storch; columbic; R.B. Anderson, John&Willi parent-child publishing company (John Wiley)&Sons, Inc.), new york, page 217, 1951. There is a continuing desire in the art to improve the fischer-tropsch process, particularly to adjust the product distribution of a given catalyst during its use.

Disclosure of Invention

It is an object of the present invention to provide an improved fischer-tropsch process wherein a cobalt catalyst having a relatively high initial activity is used. In particular, processes for increasing paraffin and wax yields are improved.

According to the present invention, one of the above and other objects can be accomplished by the provision of a process for the preparation of paraffins and waxes from a gas mixture comprising hydrogen and carbon monoxide in at least two conversion reactors being a first reactor and a second reactor, said reactors comprising a catalyst, said process comprising at least the steps of:

(a) providing the gas mixture to at least two conversion reactors;

(b) catalytically converting the gas mixture of step (a) under initial reaction conditions to obtain an initial fischer-tropsch product comprising paraffins having from 5 to 300 carbon atoms;

(c) combining the initial fischer-tropsch product streams from each of the at least two reactors of step (b) to obtain a combined fischer-tropsch product stream;

(d) subjecting the combined fischer-tropsch product stream of step (c) to a hydrogenation step to obtain a hydrogenated fischer-tropsch product stream;

(e) separating the hydrogenated fischer-tropsch product stream of step (d) thereby obtaining at least a fraction comprising 5 to 9 carbon atoms, a fraction comprising 10 to 17 carbon atoms and a fraction comprising 18 to 300 carbon atoms;

(f) separating the hydrogenated fraction comprising 18 to 300 carbon atoms of step (e) thereby obtaining one or more light waxes having a congealing point in the range of 30 to 75 ℃ and heavy waxes having a congealing point in the range of 75 to 120 ℃, wherein subsequently the relative concentration of the fraction comprising 5 to 9 carbon atoms, the fraction comprising 10 to 17 carbon atoms, the concentration of light waxes and the concentration of heavy waxes is varied by increasing, decreasing or maintaining the reaction temperature of at least one of the reactors.

It has now been found that in the case of hydrocarbon synthesis carried out in two or more reactors, a more flexible way of producing paraffins and waxes comprising hydrocarbons in the range of C5 to C41 can be managed.

This means that the process allows to adjust the reaction temperature in the different reactors such that the product stream obtained from a system comprising at least two reactors can be optimized for the desired product.

Another advantage of the present invention is that in case the hydrocarbon synthesis is carried out in two or more reactors, the deactivation of the fischer-tropsch catalyst over time can be managed by changing the reaction temperature of at least two reactors.

Another advantage is that by controlling the process temperature in the different reactors, the difference between the start of the catalyst run temperature and the end of the catalyst run temperature is less than operational and it is not possible to change the reaction temperature of the different reactors. Thus, the product split difference per reactor over the lifetime is thus reduced.

Detailed Description

The process according to the invention is a process for the preparation of paraffins and waxes from a gas mixture comprising hydrogen and carbon monoxide in a fischer-tropsch reactor. The gas mixture comprising hydrogen and carbon monoxide is also referred to as synthesis gas or syngas. At least two conversion reactors, a first reactor and a second reactor, are operated, said reactors comprising a fixed bed of a reducing fischer-tropsch catalyst. The catalyst comprises cobalt as the catalytically active metal.

The catalyst may be fresh catalyst or rejuvenated catalyst. Reference herein to fresh catalyst is to catalyst as-prepared which has not undergone a fischer-tropsch process. Reference herein to rejuvenated catalysts is to regenerated catalysts whose initial activity has been at least partially restored, typically by several reduction and/or oxidation steps. The catalyst is preferably fresh catalyst, since fresh catalyst in particular has a very high initial activity.

Fischer-tropsch catalysts comprising cobalt as the catalytically active metal are known in the art. Any suitable cobalt-containing fischer-tropsch catalyst known in the art may be used. Typically, such catalysts comprise cobalt on a support material based on a support, optionally in combination with one or more metal oxides and/or metals as promoters selected from zirconium, titanium, chromium, vanadium and manganese (especially manganese). The most suitable catalyst comprises cobalt as the catalytically active metal and titania as the support material.

The catalyst may further comprise one or more promoters. One or more metals or metal oxides may be present as promoters, more particularly one or more d-metals or d-metal oxides. Suitable metal oxide promoters may be selected from groups 2-7 of the periodic Table of the elements, or actinides and lanthanides. In particular, oxides of magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are suitable promoters. Suitable metal promoters may be selected from groups 7-10 of the periodic table of elements. Manganese, iron, rhenium and group 8-10 noble metals are particularly suitable as promoters, and are preferably provided in the form of salts or hydroxides.

The promoter, if present in the catalyst, is typically present in an amount of from 0.001 to 100 parts by weight, preferably from 0.05 to 20, more preferably from 0.1 to 15, per 100 parts by weight of carrier material. It is to be understood, however, that the optimum amount of promoter may vary for the respective elements used as promoter.

Suitable catalysts comprise cobalt as the catalytically active metal and zirconium as a promoter. Another most suitable catalyst comprises cobalt as the catalytically active metal and manganese and/or vanadium as a promoter. If the catalyst comprises cobalt as the catalytically active metal and manganese and/or vanadium as promoter, the cobalt (manganese + vanadium) atomic ratio is advantageously at least 12: 1.

Reference herein to "groups" and the periodic Table of the elements relates to the new IUPAC versions of the periodic Table of the elements, such as those described in Handbook of Chemistry and Physics (Handbook of Chemistry and Physics), 87 th edition (CRC Press).

In operating at least two conversion reactors according to the invention, the catalyst is a reducing catalyst. In the reduction catalyst, the cobalt is substantially in its metallic state. The at least two reactors may have a fixed bed of the reduction catalyst by reducing the fixed bed of the catalyst precursor in situ, i.e. in the same reactor in which the fischer-tropsch hydrocarbon synthesis takes place, or by loading the reactors with the reduction catalyst, for example prepared by reducing the catalyst precursor in a separate vessel or reactor prior to loading the reduction catalyst into the reactor. Preferably, at least two reactors have a fixed bed of reduction catalyst by in situ reduction of a fixed bed of catalyst precursor.

Reference herein to a catalyst precursor is to a precursor which can be converted to a catalytically active catalyst by subjecting the precursor to reduction, typically by subjecting the precursor to hydrogen or a hydrogen-containing gas using reducing conditions. Such reduction steps are well known in the art.

In step (a) of the process according to the invention, the gas mixture is supplied to at least two conversion reactors.

In step (b) of the process according to the invention, the gas mixture of step (a) is catalytically converted at initial reaction conditions to obtain an initial fischer-tropsch product comprising paraffins having from 5 to 300 carbon atoms.

By "fischer-tropsch product stream comprising paraffins having from 5 to 300 carbon atoms" is meant in part 5 to 300 carbon atoms per molecule.

The Fischer-Tropsch product stream provided in step (b) is derived from a Fischer-Tropsch process. Fischer-tropsch product streams are known in the art. The term "fischer-tropsch product" means the synthesis product of a fischer-tropsch process. In the fischer-tropsch process, synthesis gas is converted to synthesis product. Synthesis gas or syngas is obtained by conversion of a hydrocarbonaceous feedstock. Suitable feedstocks include natural gas, crude oil, heavy oil fractions, coal, biomass, and lignite. The fischer-tropsch product obtained from a hydrocarbonaceous feedstock, usually in the vapour phase, may also be referred to as a GTL (gas-liquid) product. The preparation of Fischer-Tropsch products has been described, for example, in WO 2003/070857.

It is known to the person skilled in the art that the temperature and pressure at which the fischer-tropsch process is carried out influence the extent to which synthesis gas is converted into hydrocarbons and influence the branching level of paraffins (and thus the amount of iso-paraffins). Typically, the process for preparing the fischer-tropsch derived wax may be carried out at a pressure above 25 bar. Preferably, the fischer-tropsch process is carried out at a pressure above 35 bar, more preferably above 45 bar, and most preferably above 55 bar. The practical upper limit of the fischer-tropsch process is 200 bar, preferably the process is carried out at a pressure below 120 bar, more preferably below 100 bar.

The fischer-tropsch process is suitably a low temperature process carried out at a temperature of from 170 to 290 ℃, preferably at a temperature of from 180 to 270 ℃, more preferably at a temperature of from 200 to 250 ℃.

Preferably, the fischer-tropsch reactor is operated at the initial reaction conditions of step (b), including an initial temperature in the range of from 200 to 250 ℃, and preferably from 205 to 230 ℃.

The conversion of carbon monoxide and hydrogen to hydrocarbons in the process according to the invention may be carried out at any reaction pressure and gas hourly space velocity known to be suitable for fischer-tropsch hydrocarbon synthesis. Preferably, the reaction pressure is in the range of 10 to 100 bar (absolute), more preferably in the range of 20 to 80 bar (absolute). The gas hourly space velocity is preferably in the range of from 500 to 25,000h-1, more preferably from 900 to 15,000h-1, even more preferably from 1,300 to 8,000 h-1. Preferably, the reaction pressure and the gas hourly space velocity are kept constant.

The amount of isoparaffin is suitably less than 20 wt. -%, preferably less than 10 wt. -%, more preferably less than 7 wt. -%, and most preferably less than 4 wt. -%, based on the total amount of paraffins having 9 to 24 carbon atoms.

Suitably, the fischer-tropsch derived paraffin wax according to the invention comprises more than 75 wt% n-paraffins, preferably more than 80 wt% n-paraffins. In addition, the paraffin may comprise isoparaffins, naphthenes, and alkylbenzenes.

The fischer-tropsch process for the preparation of a fischer-tropsch derived wax according to the invention may be a slurry fischer-tropsch process, an ebullated bed process or a fixed bed fischer-tropsch process, in particular a multi-tubular fixed bed.

The product stream of the fischer-tropsch process is typically separated into a water stream, a gaseous stream comprising unconverted synthesis gas, carbon dioxide, inert gases and C1 to C4, and a C5+ stream.

The overall fischer-tropsch hydrocarbonaceous product suitably comprises a C1 to C300 fraction.

The lighter fraction of the fischer-tropsch product, suitably comprising a C1 to C4 fraction, is separated from the fischer-tropsch product by distillation, thereby obtaining a fischer-tropsch product stream, suitably comprising a C5 to C300 fraction.

The above weight ratio of compounds having at least 60 or more carbon atoms to compounds having at least 30 carbon atoms in the fischer-tropsch product is preferably at least 0.2, more preferably 0.3.

Suitably, the above weight ratio is at least 0.5 in the case of preparing a fischer-tropsch derived wax fraction having a congealing point above 90 ℃.

The weight ratio in the fischer-tropsch product may result in a fischer-tropsch derived paraffin having a low oil content.

In step (c) of the present invention, the initial fischer-tropsch product streams from each of the at least two reactors of step b) are combined to obtain a combined fischer-tropsch product stream. Typically, the combined fischer-tropsch product stream comprises paraffins having from 5 to 300 carbon atoms.

In step (d) of the present invention, the combined fischer-tropsch product stream of step (c) is subjected to a hydrogenation step to obtain a hydrogenated fischer-tropsch product stream.

The hydrogenation is suitably carried out at a temperature of from 200 to 275 ℃ and a pressure of from 20 to 70 bar. Typically, hydrogenation removes olefins and oxygenates from the hydrogenated fraction. The oxygenate is preferably a hydrocarbon containing one or more oxygen atoms per molecule. Typically, the oxygenates are alcohols, aldehydes, ketones, esters and carboxylic acids.

In step (e) of the present invention, the hydrogenated fischer-tropsch product stream of step (d) is separated to obtain at least a fraction comprising 5 to 9 carbon atoms, a fraction comprising 10 to 17 carbon atoms and a fraction comprising 18 to 300 carbon atoms.

Preferably, the amount of the fraction comprising 5 to 9 carbon atoms in step (e) is in the range of 3 to 14 wt. -%, based on the total fischer-tropsch hydrocarbonaceous material comprising the C1 to C300 fractions.

Furthermore, the amount of the fraction comprising 10 to 17 carbon atoms in step (e) is in the range of 7-21 wt. -%, based on the total fischer-tropsch hydrocarbonaceous material comprising the C1 to C300 fractions.

The fraction is preferably divided into a fraction containing 10 to 13 carbon atoms and a fraction containing 14 to 17 carbon atoms. Furthermore, the amount of the fraction comprising 10 to 13 carbon atoms is in the range of 3 to 11 wt% and the amount of the fraction comprising 14 to 17 carbon atoms is in the range of 4 to 10 wt% based on the total fischer-tropsch hydrocarbonaceous product comprising C1 to C300 fractions.

In step (f) of the present invention, the hydrogenated fraction comprising 18 to 300 carbon atoms in step (e) is separated, thereby obtaining one or more light waxes having a congealing point in the range of 30 to 75 ℃ and heavy waxes having a congealing point in the range of 75 to 120 ℃, wherein subsequently the relative concentration of the fraction comprising 5 to 9 carbon atoms, the fraction comprising 10 to 17 carbon atoms, the concentration of the light waxes and the concentration of the heavy waxes is varied by increasing, decreasing or maintaining the reaction temperature of at least one reactor.

Preferably, the relative concentrations of the fraction comprising 5 to 9 carbon atoms, the fraction comprising 10 to 17 carbon atoms, the concentration of light waxes and the concentration of heavy waxes are varied by adding nitrogen compounds to at least one reactor.

Preferably, the nitrogen-containing compound is added to the gas mixture of step (a) such that the nitrogen-containing compound is present in the gas mixture in a concentration in the range of from 0.05 to 10 ppmV.

Examples of suitable nitrogen-containing compounds are ammonia, HCN, NO, amines, organic cyanides (nitriles) or heterocyclic compounds containing at least one nitrogen atom as a member of a heterocyclic ring.

Suitably, the nitrogen-containing compound is a compound selected from the group consisting of ammonia, HCN, NO, an amine, and combinations or two or more thereof.

Preferred amines include amines having one or more alkyl or alcohol groups having up to five carbon atoms. More preferably, the amine is a monoamine. Examples of particularly preferred amines include trimethylamine, dipropylamine, diethanolamine and methyldiethanolamine.

A particularly preferred nitrogen-containing compound is ammonia.

By light wax is meant a wax having a congealing point in the range of 30 to 75 ℃. Heavy wax means a wax having a congealing point in the range of 75 to 120 ℃.

The congealing point of the paraffin wax according to the invention is determined according to ASTM D938.

Suitably, the hydrogenated fraction comprising 18 to 300 carbon atoms in step (d) is isolated by vacuum distillation at a pressure of 5 to 20 mbar, preferably 5 to 15 mbar, and more preferably 10 to 15 mbar. The distillation is also preferably carried out at a temperature of from 300 to 350 ℃.

Preferably, the first light one or more waxes are obtained as distillate and/or side-draw in a vacuum distillation, for example a first light wax fraction having a congealing point in the range of 30 to 35 ℃, a second light wax fraction having a congealing point in the range of 50 to 60 ℃ and a third light wax fraction having a congealing point in the range of 65 to 75 ℃.

Suitably, the first light wax fraction is obtained as a top fraction of a vacuum distillation, the second light wax fraction is obtained as a side fraction of a vacuum distillation and the third light wax fraction is obtained as a heavier side fraction of a vacuum distillation.

Preferably, the one or more wax fractions having a congealing point in the range of 30 to 75 ℃ in step (f) are hydrofinished to obtain one or more hydrofinished wax fractions having a congealing point in the range of 30 to 75 ℃. Suitably, the wax fraction having a congealing point in the range of 30 to 75 ℃ is hydrofinished, thereby obtaining a hydrofinished wax fraction having a congealing point in the range of 30 to 75 ℃.

Optionally, the first light wax fraction and the second light wax fraction are hydrofinished to obtain a first light hydrofinished wax fraction having a congealing point in the range of from 30 to 35 ℃ and a second light hydrofinished wax fraction having a congealing point in the range of from 50 to 60 ℃.

Preferably, the amount of hydrofinished wax fraction having a congealing point of 30 ℃ is in the range of from 3 to 7 wt% based on the total fischer-tropsch hydrocarbonaceous product comprising C1 to C300 fractions. Moreover, the amount of the hydrofinished wax fraction having a congealing point of 50 ℃ is preferably in the range of from 5 to 13 wt% based on the total fischer-tropsch hydrocarbonaceous product comprising C1 to C300 fractions.

Furthermore, the amount of the hydrofinished wax fraction having a congealing point of 70 ℃ is in the range of from 7 to 16 wt% based on the total fischer-tropsch hydrocarbonaceous product comprising C1 to C300 fractions.

Preferably, at least the third light wax, i.e. the heaviest side-cut fraction of the vacuum distillation step (f), is hydrofinished, thereby obtaining a hydrofinished wax fraction having a congealing point in the range of from 65 to 75 ℃.

Typical hydrofinishing conditions for the hydrofinishing of the above fractions are described, for example, in WO 2007/082589.

Suitably, the second heavy wax of step (f) is separated, thereby obtaining at least one distilled wax fraction having a congealing point in the range of from 75 to 85 ℃ and at least one residual wax fraction having a congealing point in the range of from 95 to 120 ℃.

Preferably, the heavy second wax of step (f) is separated, thereby obtaining at least one distilled wax fraction having a congealing point in the range of from 70 to 90 ℃, preferably from 70 to 85 ℃ and more preferably from 75 to 85 ℃.

Suitably, the heavy distilled wax fraction having a congealing point in the range of 75 to 85 ℃ is hydrofinished, thereby obtaining a hydrofinished heavy distilled wax fraction having a congealing point in the range of 75 to 85 ℃.

Further, the heavy distilled wax fraction having a congealing point in the range of 70 to 90 ℃, preferably in the range of 70 to 85 ℃ and more preferably in the range of 75 to 85 ℃ is hydrofinished, thereby obtaining a hydrofinished heavy distilled wax fraction having a congealing point in the range of 70 to 90 ℃, preferably in the range of 70 to 85 ℃ and more preferably in the range of 75 to 85 ℃.

Preferably, the heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃ is hydrofinished, thereby obtaining a hydrofinished heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃.

The heavy second wax of step (f) is preferably isolated by short path distillation at a pressure of preferably 0.05 to 0.5 mbar, and more preferably 0.1 to 0.3 mbar. The distillation is preferably carried out at a temperature of from 200 to 350 ℃, more preferably from 250 to 300 ℃.

Typically, the residual heavy wax having a congealing point in the range of 95 to 120 ℃ is obtained as a residual fraction of a short path distillation. The term residual means a fraction obtained by distillation, which is a residual bottom fraction, neither a top fraction nor a side fraction.

Short path distillation (also known as molecular distillation) is known in the art and is therefore not described in detail herein. An example of a form of short path distillation is a wiped film evaporator. Typical short path distillation is described, for example, in "distillation: operations and applications (Distiltation, operations and applications), Andrzej G Lo Rak and Hartmut Schoenmakers, Elsevier Inc, Oxford, chapter 9.1 of 2014.

Thus, preferably, the heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃ is hydrofinished, thereby obtaining a hydrofinished heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃.

Preferably, one or more Fischer-Tropsch derived waxes are obtained having a congealing point in the range of from 30 to 120 ℃. More preferably, a fischer-tropsch derived wax having a congealing point in the range of from 30 to 35 ℃ or in the range of from 50 to 60 ℃ or in the range of from 60 to 70 ℃, or in the range of from 75 to 85 ℃ or in the range of from 95 to 100 ℃, or in the range of from 100 to 106 ℃ or in the range of from 106 to 120 ℃ is obtained by the process according to the invention.

Suitably, the amount of hydrofinished wax fraction having a congealing point in the range of from 100 to 105 ℃ is in the range of from 15 to 70 wt% based on the total fischer-tropsch hydrocarbonaceous product comprising a C1 to C300 fraction.

The determination of the content of each final product fraction in the total fischer-tropsch hydrocarbonaceous product can be achieved by analysing a sample of this stream using chromatographic methods such as high temperature gas chromatography or distillation. Conveniently, the gas, liquid and solid phases are quantified, analyzed using respective chromatographic methods and combined to produce a fischer-tropsch product distribution, taking into account that the olefins and oxygenates are hydrogenated to respective paraffins.

Suitably, the reaction temperature is increased by:

-increasing the amount of synthesis gas provided to the reactor;

-increasing the temperature of the cooling water supplied to the reactor; and/or

-providing a nitrogen containing compound to the reactor, preferably by adding the nitrogen containing compound to the gas mixture prior to steps a) and b), preferably the nitrogen containing compound is selected from the group consisting of ammonia, HCN, NO, amines and combinations or two or more thereof.

Suitably, the reactor operating point is increased by:

-increasing the amount of synthesis gas provided to the reactor;

The reactor operating point means the operating temperature at which the target conversion of CO and H2 is achieved.

In one embodiment of the invention, the reaction temperature and/or the reactor operating point is increased by increasing the amount of synthesis gas provided to the reactor. Since the fischer-tropsch reaction is an exothermic reaction, providing more hydrogen and carbon monoxide will result in more heat being generated. The increase in heat will result in a decrease in selectivity to heavy hydrocarbon products.

In one embodiment of the invention, the reaction temperature and/or the reactor operating point is increased by increasing the temperature of the cooling water supplied to the reactor. The reaction temperature and/or the reactor operating point may be increased by supplying a nitrogen-containing compound to the reactor. By supplying the nitrogen-containing compound to the reduced catalyst as-prepared or rejuvenated, the catalyst activity is reduced and the temperature can be increased. This higher temperature and reduced activity condition results in lower relative humidity and less catalyst deactivation. Moreover, since the effect of such nitrogen-containing compounds on the catalyst activity appears to be reversible, the catalyst activity can be adjusted by adjusting the concentration of the nitrogen-containing compound. In particular, the gradual decrease in catalyst activity can be compensated by a gradual decrease in the concentration of nitrogen-containing compounds in the feed gas stream provided to the catalyst. Therefore, the reaction temperature and the reactor productivity (productivity) can be controlled and kept constant for a longer time after the start-up of the reactor, resulting in an improvement in the stability of the catalyst.

In one embodiment, the nitrogen-containing compound is provided to the one or more reactors as the reaction temperature and/or the reactor operating point is increased.

Moreover, the reaction temperature is reduced by:

-reducing the amount of synthesis gas provided to the reactor;

-reducing the temperature of the cooling water supplied to the reactor; and/or

Moreover, the reactor operating point is lowered by:

-reducing the amount of synthesis gas provided to the reactor;

-reducing the temperature of the cooling water supplied to the reactor; and/or

In one embodiment, the reaction temperature and/or the reactor operating point in one or more reactors is reduced by reducing the amount of synthesis gas provided to the reactor. By reducing the amount of syngas provided to the reactor, less hydrocarbons are synthesized. Because the FT reaction is an exothermic reaction, less energy will be released if less hydrocarbons are synthesized.

In one embodiment, the reaction temperature and/or the reactor operating point in one or more reactors is reduced by reducing the temperature of the cooling water provided to the reactor. Furthermore, lowering the temperature by lowering the temperature of the cooling medium results in an increased selectivity to the heavy fraction.

In one embodiment, the reaction temperature and/or the reactor operating point in one or more reactors is reduced by providing a nitrogen-containing compound to the reactor.

In one embodiment of the invention, the method comprises one of the following steps:

-providing a nitrogen-containing compound to the first reactor in case the first reactor comprises a least active catalyst;

-providing a nitrogen-containing compound to the second reactor in case the second reactor comprises the least active catalyst. This can be done with an increase in temperature in the reactor, resulting in an increase in the activity of the catalyst, but a decrease in the selectivity to heavy hydrocarbons.

-providing a nitrogen-containing compound to the first reactor in case the first reactor comprises the most active catalyst;

-providing a nitrogen-containing compound to the second reactor in case the second reactor comprises the most active catalyst.

The nitrogen-containing compounds added to increase or decrease the reaction temperature and/or the reaction operating point in one or more reactors are similar to the nitrogen-containing compounds described above.

In another aspect, the present invention provides fischer-tropsch derived paraffins and waxes obtainable by the process according to the present invention.

The invention is illustrated by the following non-limiting examples.

Examples of the invention

In the present example, two Fischer-Tropsch reactors are connected in series. A cobalt based fischer-tropsch catalyst was loaded in two reactors and reduced. The synthesis gas is supplied to an upstream reactor (designated R1) and a downstream reactor (designated R2) receives the exhaust gas from the upstream reactor.

The off-gas contains unreacted hydrogen and carbon monoxide. In each example, one reactor was just started and the other reactor activity deteriorated. In the basic case, both reactors are operated at the same production rate, but at different operating temperatures. Table 1 lists the amounts of gases, solvents, LDF, HDF, SX-30, SX-50, SX-70, SX-100/105.

In table 1, the first three rows provide the reaction conditions. The addition of ammonia is indicated by Y (YES) or N (NO). The product gas, solvent, LDF, HDF, SX-30, SX-50, SX-70, SX-100/105 are expressed in weight percent based on the Fischer-Tropsch product stream.

In a first example according to the invention, the productivity of the first reactor is reduced by adding ammonia while increasing the temperature. While the productivity of the second reactor increases. The distribution of the products is given in the table. It can be seen that the total amount of solvent, LDF, HDF, SX-30, SX-50 and SX-70 increased from 36% to 41%.

In a second example according to the invention, the load through the first reactor is increased and the load through the second reactor is decreased, thereby keeping the total production constant. It can be seen that the amount of SX-30, SX-50, SX-70, SX-100/105 increased from 54% to 60%.

In a third example, production through the first reactor is increased and an N compound is added. Production through the second reactor is reduced by adding an N compound to the feed. It can be seen that the amount of solvent, LDF and HDF increased from 36% to 41%.

TABLE 1

Discussion of the related Art

Table 1 example 1 clearly shows an increase in gas, solvent, LDF, HDF, SX-30, SX-50, SX-70, but a decrease in SX-100/105. These observations indicate that the addition of ammonia to the synthesis gas stream results in a decrease in the C41+ selectivity of the fischer-tropsch catalyst.

Example 2 clearly shows a decrease in gas, solvent, LDF, but an increase in SX-100/105. The amounts of HDF, SX-30, SX-50, Sx-70 remained unchanged. These observations indicate that increasing the temperature of both reactors results in an increase in the C41+ selectivity of the fischer-tropsch catalyst.

Example 3 clearly shows an increase in gas, solvent, LDF, HDF, SX-30, SX-50, SX-70, but a decrease in SX-100/105.

These observations indicate that adding ammonia to the synthesis gas stream and increasing the temperature in one reactor while decreasing the temperature in the other reactor results in a decrease in the C41+ selectivity of the fischer-tropsch catalyst.

Thus, these examples clearly show that by taking into account the state of the catalyst present in each reactor in the fischer-tropsch reactor system, the content of the product stream can be well controlled. Reference herein to "groups" and the periodic Table of the elements refers to new IUPAC versions of the periodic Table of the elements, such as those described in the 87 th edition of Handbook of Chemistry and Physics (CRC Press).

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the disclosure is not necessarily limited to the disclosed embodiment. It is intended to cover various modifications, combinations, and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. The present disclosure includes any and all embodiments of the following claims.

It should also be understood that various changes may be made without departing from the essence of the invention. These modifications are also implicitly included in the description. They are still within the scope of the present invention. It should be understood that this disclosure is intended to yield a patent covering many aspects of the present invention both independently and as an overall system and in method and apparatus modes.

Any patents, publications, or other references mentioned in this patent application are incorporated herein by reference. In addition, for each term used, it should be understood that, unless its use in this application is inconsistent with such interpretation, for each term and all definitions, alternative terms and synonyms should be understood as common dictionary definitions, such as those contained in at least one standard technical dictionary recognized by the skilled artisan.

Claims

1. Process for the preparation of paraffins and waxes from a gaseous mixture comprising hydrogen and carbon monoxide in at least two conversion reactors being a first reactor and a second reactor, said reactors comprising a catalyst, said process comprising at least the following steps:

(a) providing the gas mixture to at least two conversion reactors;

(f) separating the hydrogenated fraction comprising 18 to 300 carbon atoms in step (e) thereby obtaining one or more light waxes having a congealing point in the range of 30 to 75 ℃ and heavy waxes having a congealing point in the range of 75 to 120 ℃, wherein subsequently the relative concentration of the fraction comprising 5 to 9 carbon atoms, the fraction comprising 10 to 17 carbon atoms, the concentration of the light waxes and the concentration of the heavy waxes is varied by increasing, decreasing or maintaining the reaction temperature of at least one of the reactors, the reaction temperature being between 170 and 290 ℃.

2. The process of claim 1, wherein the fischer-tropsch reactor is operated at initial reaction conditions of step (b), including a temperature in the range of from 200 to 250 ℃.

3. The process according to claim 1 or 2, wherein the amount of the fraction comprising 5 to 9 carbon atoms in step (e) is in the range of 3 to 14 wt. -%, based on the total fischer-tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

4. The process according to claim 1 or 2, wherein the amount of the fraction comprising 10 to 17 carbon atoms in step (e) is in the range of 7 to 21 wt. -%, based on the total fischer-tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

5. The process according to claim 1 or 2, wherein the one or more wax fractions of step (f) having a congealing point in the range of 30 to 75 ℃ are hydrofinished to obtain one or more hydrofinished wax fractions having a congealing point in the range of 30 to 75 ℃.

6. The process of claim 5, wherein the amount of hydrofinished wax fraction having a congealing point of 30 ℃ is in the range of 3 to 7 wt% based on the total Fischer-Tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

7. The process of claim 5, wherein the amount of the hydrofinished wax fraction having a congealing point of 50 ℃ is in the range of from 5 to 13 wt% based on the total Fischer-Tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

8. The process of claim 5, wherein the amount of hydrofinished wax fraction having a congealing point of 70 ℃ is in the range of from 7 to 16 wt% based on the total Fischer-Tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

9. The process according to claim 1, separating the heavy wax of step (f), thereby obtaining at least one distilled wax fraction having a congealing point in the range of from 75 to 85 ℃ and at least one residual wax fraction having a congealing point in the range of from 95 to 120 ℃.

10. The process according to claim 9, the heavy distilled wax fraction having a congealing point in the range of 75 to 85 ℃ is hydrofinished to obtain a hydrofinished heavy distilled wax fraction having a congealing point in the range of 75 to 85 ℃.

11. The process according to claim 9, wherein the heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃ is hydrofinished to obtain a hydrofinished heavy residual wax fraction having a congealing point in the range of 95 to 120 ℃.

12. The process of claim 11, wherein the amount of hydrofinished wax fraction having a congealing point of from 100 to 105 ℃ is in the range of from 15 to 70 wt% based on the total fischer-tropsch hydrocarbonaceous material comprising a C1 to C300 fraction.

13. The process of claim 1, wherein the reactor operating point is increased by:

increasing the amount of synthesis gas provided to the reactor;

increasing the temperature of cooling water provided to the reactor; and/or

Providing a nitrogen-containing compound to the reactor.

14. The process of claim 13, wherein nitrogen-containing compounds are provided to the reactor by adding the nitrogen-containing compounds to the gas mixture prior to steps a) and b).

15. The process of claim 13 or 14, wherein the nitrogen-containing compound is selected from the group consisting of ammonia, HCN, NO, an amine, and combinations or two or more thereof.

16. The process of claim 1, wherein the reactor operating point is lowered by:

reducing the amount of synthesis gas provided to the reactor;

reducing the temperature of cooling water provided to the reactor; and/or

Providing a nitrogen-containing compound to the reactor.

17. The process of claim 16, wherein nitrogen-containing compounds are provided to the reactor by adding the nitrogen-containing compounds to the gas mixture prior to steps a) and b).

18. The process of claim 16 or 17, wherein the nitrogen-containing compound is selected from the group consisting of ammonia, HCN, NO, an amine, and combinations or two or more thereof.