Description:FIELD OF THE INVENTION
The present invention relates to a process for preparation of a mono-metallic hydrogenating catalyst. More specifically, the present invention relates to a process for preparation of a mono-metallic nickel-based hydrogenating catalyst, a mono-metallic nickel-based hydrogenating catalyst, and uses thereof in the preparation of de-aromatized hydrocarbon solvents having aromatic content less than 100 ppm through selective hydrogenation of distillates having boiling point in range of 150° C to 350° C.
BACKGROUND OF THE INVENTION
Dearomatized hydrocarbon solvents commonly known as D-solvents or D-series, are considered an ideal replacement for traditional hydrocarbon solvents such as mineral or white spirits, kerosene etc. With its low to extremely low aromatic content (less than 0.1%), dearomatized fluids still provide optimal solvency in many applications such as printing inks, paint, coatings, metal working fluids, industrial and institutional cleaning, adhesives, sealants, drilling fluids etc., and maintain good safety, health, and environmental standards.
The processes for obtaining de-aromatized hydrocarbon solvents involve conversion of the aromatic compounds present in hydrocarbon feed to the corresponding saturated hydrocarbons by reacting the aromatic compounds with hydrogen in the presence of a suitable catalyst under appropriate process conditions. Further, the hydrogenated petroleum distillates obtained from the hydrogenation reaction are usually stabilized by the removal of the light, volatile hydrocarbon components.
In order to produce high valued de-aromatized hydrocarbon solvents, selection of suitable hydrocarbon feedstock is important. Further, competitive and highly efficient processes for hydrogenation reaction of the hydrocarbon stream are critical to produce these high value products meeting the existing and future market demand.
Conventionally, de-aromatized solvents are prepared from expensive hydrocarbon feedstock and the processes used for this purpose require harsh hydrogenation reaction conditions.
The art continues to develop processes for reaction of niche hydrocarbon feedstock with hydrogen to produce de-aromatized hydrocarbon solvents in an efficient and cost-effective manner.
To have an efficient and economic process for preparation of de-aromatized solvent from less expensive hydrocarbon feedstock through selective hydrogenation, a hydrogenating catalyst which has high selectivity, high active metal reducibility, and having less severe process condition requirements along with efficient de-aromatization capabilities is highly desirable.
Most used hydrogenating catalyst in the hydrocarbon industry is a catalyst comprising nickel and other active metals like copper loaded on a refractory metal oxide support. Such catalysts are mostly prepared by impregnating nickel metal on refractory metal oxide support using spray impregnation method. The conventional spray impregnation method involves spraying a solution containing precursor of nickel on refractory metal oxide support. It has been observed that reducibility of active metal in a hydrogenating catalyst is crucial for its catalytic activity and dependent on various factors including the process used for spray impregnation in terms of steps involved, order of steps, and concentration of precursor solution used.
IN202047044783 provides a method for preparing a nickel and copper based bimetallic catalyst for hydrogenating aromatic compounds. The method involves step a) contacting the nickel precursor with support and step b) contacting the copper precursor with the support. The applicant has discovered that the pre-impregnation (with respect to the impregnation of the nickel precursor) of a copper precursor on the support makes it possible to obtain better results in terms of reducibility of the nickel compared to a post-impregnation of the copper precursor (with respect to the impregnation of the nickel precursor), this being for identical catalyst reduction operating conditions (temperature, time, reducing gas).
IN202147031138 provides a process for preparing a selective hydrogenation catalyst, comprising a step of forming a Ni-Cu alloy in pre-impregnation. It has been observed by the applicant that, during the preparation of the catalyst, carrying out a step of bringing the support into contact with a solution simultaneously containing a copper-based metal precursor and a nickel-based metal precursor, followed by a step of drying and reducing in the presence of a reducing gas at low temperature (between 150° C. and 250° C.) makes it possible to obtain a nickel-copper alloy (in reduced form) which unexpectedly makes it possible to greatly improve the reducibility of the nickel active phase on the support, said nickel active phase being supplied for the most part in a step subsequent to the formation of the nickel-copper alloy (in reduced form).
It is observed by the applicant unexpectedly that it possible to greatly improve the reducibility of the active phase of nickel on the refractory metal oxide support in a mono-metallic hydrogenating catalyst by adopting a multi-stage spray impregnation instead of conventional spray impregnation.
OBJECTIVES OF THE PRESENT INVENTION
It is the primary objective of the present invention to provide a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.
It is another objective of the present invention to provide a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on an alumina support.
It is another objective of the present invention to provide a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a phosphorous modified alumina support.
It is another objective of the present invention to provide a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support wherein high reducibility of active phase of nickel on the refractory metal oxide support can be achieved.
It is another objective of the present invention to provide a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support wherein reducibility of active phase of nickel on the refractory metal oxide support is improved through multi-stage spray impregnation of nickel on the refractory metal oxide support.
The other objective of the present invention is to provide a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.
It is another objective of the present invention to provide a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support wherein active phase of nickel on the refractory metal oxide support has high reducibility.
The other objective of the present invention is to provide a process for preparing de-aromatized hydrocarbon solvents by subjecting distillates having boiling point in range of 150° C to 350° C in presence of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.
It is another objective of the present invention is to provide a process for preparing de-aromatized hydrocarbon solvents having aromatic content less than 100 ppm by subjecting distillates having boiling point in range of 150° C to 350° C in presence of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.
It is another objective of the present invention to provide a process for preparing de-aromatized hydrocarbon solvents having aromatic content less than 100 ppm from a heavy hydrocarbon feedstream by subjecting the said feedstream to distillation followed by catalytic hydrotreatment of distillate having boiling point in the range of 180° C to 550° C in presence of a hydrotreatment catalyst, isodewaxing, fractionation, and subjecting the fraction having boiling point in range of 150° C to 350° C having aromatic content in range of 5000 ppm to 40000 ppm to selective hydrogenation in presence of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.
SUMMARY OF THE INVENTION
The present invention discloses a process for preparation of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on an alumina support. The process involves preparation of an alumina support, loading of nickel on the said alumina support using a multi-stage spray impregnation process, drying the said nickel sprayed alumina support and calcining the dried nickel loaded alumina support to obtain the mono-metallic nickel-based hydrogenating catalyst.

The alumina support is obtained by extruding alumina dough prepared by mixing alumina powder with an acid using a trilobite dye and drying the wet alumina extrudes for a duration of 5 to 15 hours at a temperature range of 60 to 120 ℃ followed by calcining at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours.

The wet alumina extrudes is preferably dried for 10 to 12 hours at a temperature range of 80 to 100 ℃ and calcined at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours.

The acid mixed in the alumina powder to prepare alumina dough is selected from phosphoric acid, nitric acid, and acetic acid. Further, the acid is nitric acid. The alumina powder is one or more selected from boehmite, pseudo boehmite, gibbsite, direct alumina, aluminum hydroxide, aluminum chlorides, aluminum sulfates, dawsonites and the alumina powder has surface area in range of 200 to 400 m2/gr. Further, the alumina powder is pseudo-boehmite, phosphorous modified alumina, and a combination thereof and has surface area in range of 250 to 330 m2/gr.

The alumina support thus obtained is then loaded with nickel using a multi-stage spray impregnation process wherein precursor solutions of nickel with varying concentration is sprayed on the alumina support with intermittent drying steps.

The precursor solutions of varying concentration are prepared by dissolving 0.2 mol % to 1.5 mol % of one or more nickel salt selected from nickel (II) nitrate hexahydrate and nickel (II) acetate tetrahydrate in water. Further, the precursor solutions are prepared by dissolving 0.4 mol % to 0.6 mol % of nickel (II) nitrate hexahydrate in water.

The intermittent drying step involves initial drying under vacuum at a temperature range of 50 to 100 ℃, followed by drying in an oven at a temperature range of 60 to 120 ℃, and then air drying at a temperature range of 450 to 550 ℃ for a duration of 4 to 12 hours. Further, the intermittent drying involves initial drying under vacuum at a temperature range of 60 to 80 ℃, followed by drying in an oven at a temperature range of 80 to 100 ℃, and then air drying at a temperature range of 450 to 520 ℃ for a duration of 8 to 12 hours.

The nickel loaded alumina support obtained at the end of multi-stage spray impregnation process is subjected to calcination at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours to obtain the mono-metallic hydrogenating catalyst. Further, the calcination is carried out at a temperature range of 480 to 520 ℃ for a duration of 4 to 8 hours to obtain mono-metallic hydrogenating catalyst.

The present invention further provides a mono-metallic hydrogenating catalyst comprising 10 to 60 weight % of nickel metal dispersed on a refractory metal oxide support for producing de-aromatized hydrocarbon solvents through selective hydrogenation of heavy and middle hydrocarbon distillate having aromatic content in range of 5000 ppm to 40000 ppm, and sulfur content ranging from 0 ppm to 1 ppm. The mono-metallic catalyst has reducibility of nickel metal in the range of 80 % to 90 % at a reduction temperature in the range of 440 to 480 ℃.

The refractory metal oxide is one or more selected from the group consisting of alumina, silica, titania, and zirconia. The alumina support in the mono-metallic hydrogenating catalyst is alumina or modified alumina. The modified alumina is a phosphorous modified alumina.

The present invention further provides a process for preparing de-aromatized hydrocarbon solvents having aromatic content less than 100 ppm from a heavy hydrocarbon feedstream by subjecting the said feedstream to distillation followed by catalytic hydrotreatment of distillate having boiling point in the range of 180° C to 550° C in presence of a hydrotreatment catalyst, isodewaxing, fractionation, and subjecting the fraction having boiling point in range of 150° C to 350° C and aromatic content in range of 5000 ppm to 40000 ppm to selective hydrogenation in presence of a mono-metallic hydrogenating catalyst comprising nickel metal dispersed on a refractory metal oxide support.

The fractionated hydrocarbon feedstream utilized in the process for preparation of de-aromatized solvents is a low-cost hydrocarbon feedstream having high aromatic content ranging from 5000 ppm to 20,000 ppm, and sulfur content ranging from 0 ppm to 1 ppm. Further, the aromatic content of the hydrocarbon feedstream is in range of 5000 ppm to 40000 ppm and sulfur content is in range of 0.5 ppm to 1 ppm. The feedstream comprises one or more selected from crude oil, heavy vacuum gas oil, and lube base oil.

The de-aromatized solvent preparation process starts with the distillation of heavy hydrocarbon feedstream to obtain a first distillate having boiling point in range of 180° C to 550° C. The first distillate is then subjected to hydrotreatment in presence of a hydrotreatment catalyst to obtain a hydrotreated hydrocarbon stream having sulfur content of less than 100 ppm, The hydrotreatment of the first distillate is carried out at a reactor temperature ranging from 300° C to 450 °C, reactor pressure ranging from 60 bar to 180 bar, weight hourly space velocity (WHSV) ranging from 0.5 h−1 to 3.0 h−1, and volume ratio of hydrogen to heavy hydrocarbon stream ranging from 100 Nm3/m3 to 1500 Nm3/m3. Further, the hydrotreatment of the first distillate is carried out at a reactor temperature ranging from 350° C to 400 °C, reactor pressure ranging from 100 bar to 150 bar, weight hourly space velocity (WHSV) ranging from 0.75 h−1 to 1.25 h−1, and volume ratio of hydrogen to heavy hydrocarbon stream ranging from 400 Nm3/m3 to 1000 Nm3/m3

The hydrotreated hydrocarbon stream having sulfur content less than 100 ppm is further subjected to isodewaxing which is mainly done to isomerize hydrocarbons and fractionation to obtain a second distillate having boiling point in the range of 150° C to 350° C.

The second distillate is further subjected to selective hydrogenation in presence of nickel-based mono-metallic catalyst to obtain de-aromatized solvents having aromatic content of de-aromatized solvent obtained is in a range of 5 ppm to 100 ppm and sulfur content in range of 0.5 to 1 ppm. In the most preferred embodiment, the aromatic content of de-aromatized solvents obtained is in a range of 20 ppm to 50 ppm.

The selective hydrogenation of the second distillate is carried out at a reactor temperature ranging from 80 °C to 200 °C, reactor pressure ranging from 25 bar to 35 bar, liquid hourly space velocity (LHSV) ranging from 0.25 h-1 to 2.0 h-1, and volume ratio of hydrogen to second distillate ranging from 40 Nm3/m3 to 100 Nm3/m3. Further, the selective hydrogenation of the second distillate is carried out at a reactor temperature ranging from 140 °C to 180 °C, reactor pressure ranging from 10 bar to 45 bar, liquid hourly space velocity (LHSV) ranging from 0.5 h-1 to 1.0 h-1, and volume ratio of hydrogen to second distillate ranging from 50 Nm3/m3 to 70 Nm3/m3.

The reactor pressure and volume ratio of hydrogen to second distillate is advantageously low in comparison to other processes for the preparation of de-aromatized solvents from heavy hydrocarbon feedstream.

DETAILED DESCRIPTION OF THE INVENTION
Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps of the process, features of the system, referred to or indicated in this specification, individually or collectively and all combinations of any or more of such steps or features.
The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.

Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred method, and materials are now described.

The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products and processes are clearly within the scope of the disclosure, as described herein.

The process for preparation of a mono-metallic nickel-based hydrogenating catalyst disclosed herein involves preparation of a refractory metal oxide support, loading of nickel on the said refractory metal oxide support using a multi-stage spray impregnation process, drying the said nickel sprayed refractory metal oxide support and calcining the dried nickel loaded refractory metal oxide support to obtain the mono-metallic nickel-based hydrogenating catalyst.

The refractory metal oxide support used in the process is selected from alumina, silica, titania, and zirconia. In preferred embodiments, the refractory metal oxide support is selected from alumina support, modified alumina support and combination thereof. In most preferred embodiments, the modified alumina support is a phosphorus modified alumina support. The preparation of refractory metal oxide support in the process disclosed herein involves extrusion of refractory metal oxide powder using a dye, drying the refractory metal oxide extrudes, and calcination of dried refractory metal oxide extrudes to obtain the refractory metal oxide support.

In one of the preferred embodiments, the refractory metal oxide support is an alumina support prepared by extruding alumina dough using a dye of 2 mm X 3 mm Trilobite shape, drying the wet alumina extrudes and calcining the dried alumina extrudes to obtain alumina support. In another preferred embodiment, the refractory metal oxide support is a phosphorous modified alumina support prepared by extruding alumina dough using a dye of 2 mm X 3 mm Trilobite shape, drying the wet alumina extrudes, calcining the dried alumina extrudes, and spraying solution of phosphoric acid on the dried alumina extrudes to obtain phosphorous modified alumina support.

The alumina dough used for preparing the alumina support or modified alumina support is prepared by mixing commercially available alumina powder with an acid selected from nitric acid, acetic acid, and phosphoric acid. In the most preferred embodiments, acid is nitric acid. The alumina powder is selected from boehmite, pseudo boehmite, gibbsite, direct alumina, aluminum hydroxide, aluminum chlorides, aluminum sulfates, and dawsonites. In the most preferred embodiments, alumina powder is boehmite or pseudo boehmite. The surface area of alumina powder used for preparing the alumina dough is in the range of 200 to 400 m2/gr. In the most preferred embodiment, the surface area of alumina powder is in the range of 250 to 330 m2/gr.

The process disclosed herein involves drying of wet alumina extrudes during the preparation of alumina support to obtain dried alumina extrudes. The wet alumina extrudes is dried for 5 to 15 hours at a temperature range of 60 to 120 ℃. In most preferred embodiments, the wet alumina extrudes is dried for 10 to 12 hours at a temperature range of 80 to 100 ℃.

The dried alumina extrudes is then calcined to obtain the alumina support ready for loading of nickel. The calcination of dried alumina extrudes is carried out at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours to obtain calcined alumina support. In most preferred embodiments, the dried alumina extrudes are calcined at a temperature range of 480-520 ℃ for a duration of 4 to 8 hours. The calcination is preferably performed in an open-air furnace.

The alumina support obtained after calcination is ready for loading of nickel metal using a multi-stage spray impregnation process. The spray impregnation step methodology used herein for loading nickel metal on the alumina support is a crucial step in the preparation of the mono-metallic hydrogenation catalyst disclosed herein.

It is observed by the applicant unexpectedly that it possible to greatly improve the reducibility of the active phase of nickel on the support by optimizing spray impregnation process during the preparation of mono-metallic hydrogenating catalyst disclosed herein.

The reducibility of the active phase of nickel on the refractory metal oxide support in the disclosed mono-metallic hydrogenating catalyst is greatly improved even in the absence of promoter when nickel is loaded on the alumina support through spray impregnation in a staged manner using an aqueous solution having specified concentration of nickel salt instead of single-stage spray impregnation.

The mono-metallic nickel-based hydrogenating catalyst disclosed herein has reducibility of the active phase of nickel in the range of 80 % to 90 % at a reduction temperature in the range of 440 to 480 ℃. It is also devised through experimentation that best catalytic efficiency is obtained when spray impregnation is done in two stages.

The multi-stage spray impregnation process used in the process disclosed herein involves spraying of nickel precursor solution on the alumina support in multiple steps with intermittent drying steps.

The precursor solutions of nickel salt is prepared by dissolving 0.2 mol % to 1.5 mol % of one or more nickel salt selected from nickel (II) nitrate hexahydrate and nickel (II) acetate tetrahydrate in water. In the most preferred embodiments, the aqueous solution of nickel salt is prepared by dissolving 0.4 mol % to 0.6 mol % of nickel (II) nitrate hexahydrate in water.

The multi-stage spray impregnation used in the process disclosed herein involves intermittent drying of alumina support sprayed with precursor solution. The wet nickel sprayed alumina support is dried initially under vacuum at a temperature range of 50 to 100 ℃, followed by drying in an oven at a temperature range of 60 to 120 ℃, and then air drying at a temperature range of 450 to 550 ℃ for a duration of 4 to 12 hours. In most preferred embodiments, the wet nickel sprayed alumina support is dried initially under vacuum at a temperature range of 60 to 80 ℃, followed by drying in an oven at a temperature range of 80 to 100 ℃, and then air drying at a temperature range of 450 to 520 ℃ for a duration of 8 to 12 hours.

The alumina support loaded with nickel obtained after the multi-stage spray impregnation process is calcined to obtain the mono-metallic nickel-based hydrogenation catalyst. The calcination is carried out at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours in muffle air-furnace. In the most preferred embodiments, the calcination is carried out at a temperature range of 480 to 520 ℃ for a duration of 4 to 8 hours to obtain mono-metallic nickel-based hydrogenating catalyst.

The mono-metallic hydrogenating catalyst provided by the present invention comprises nickel loaded on refractory metal oxide. The mono-metallic catalyst comprises 10 to 60 weight percent of nickel metal. In the most preferred embodiments, the weight percent of nickel metal in the mono-metallic catalyst is 30 to 50 percent by weight. Advantageously, the mono-metallic hydrogenating catalyst has reducibility of nickel metal in the range of 80 % to 90 % at a reduction temperature in the range of 440 to 480 ℃.

The refractory metal oxide support on which nickel is loaded is selected from alumina, silica, titania, and zirconia. In preferred embodiments, the refractory metal oxide support is an alumina support or modified alumina support. The modified alumina support is phosphorus modified alumina support.

The mono-metallic hydrogenating catalyst disclosed herein can be advantageously used to produce de-aromatized solvents with aromatic content in a range of 5 ppm to 100 ppm and sulfur content in a range of 0.5 ppm to 1 ppm from middle and heavy distillates having aromatic content in range of 5000 ppm to 40000 ppm, and sulfur content ranging from 0 ppm to 1 ppm. In the most preferred embodiments, the middle and heavy distillates have aromatic content in range of 5000 to 20000 ppm. In the most preferred embodiments, the aromatic content in the de-aromatized solvents is in range of 20 ppm to 50 ppm.

The process for preparation of de-aromatized solvents disclosed herein can be used advantageously to produce de-aromatized solvents with aromatic content in a range of 5 ppm to 100 ppm and sulfur content in a range of 0.5 ppm to 1 ppm from a distillate having boiling point in the range of 150° C to 350° C, aromatic content in range of 5000 ppm to 40000 ppm, and sulfur content in range of 0 ppm to 1 ppm. In the most preferred embodiments, the distillate has aromatic content in range of 5000 to 20000 ppm. In the most preferred embodiments, the aromatic content in the de-aromatized solvents is in range of 20 ppm to 50 ppm.

The process for preparing de-aromatized hydrocarbon solvents from the selective hydrogenation of a hydrocarbon feedstream disclosed herein involves distillation of a heavy hydrocarbon feedstream, followed by catalytic hydrotreatment, fractionation and catalytic selective hydrogenation.

The hydrocarbon feedstream utilized for the production of de-aromatized solvents is one or more selected from crude oil, heavy vacuum gas oil, and lube base oil. The hydrocarbon feedstream is distilled to obtain a first distillate having boiling point in the range of 180° C to 550° C.

The first distillate is then subjected to hydrotreatment in presence of hydrotreating catalyst to obtain a hydrocarbon stream having sulfur content of less than 100 ppm, The hydrotreating catalyst used in the process comprises one or more active metals selected from cobalt, nickel, and molybdenum-phosphorus impregnated on one or more support selected from alumina, silica, titania, and zirconia.

The hydrotreatment of the first distillate in the process is carried out at a reactor temperature ranging from 300° C to 450 °C, reactor pressure ranging from 60 bar to 180 bar, weight hourly space velocity (WHSV) ranging from 0.5 h−1 to 3.0 h−1, and volume ratio of hydrogen to heavy hydrocarbon stream ranging from 100 Nm3/m3 to 1500 Nm3/m3. In the most preferred embodiments, the hydrotreatment of the first distillate is carried out at a reactor temperature ranging from 350° C to 400 °C, reactor pressure ranging from 100 bar to 150 bar, weight hourly space velocity (WHSV) ranging from 0.75 h−1 to 1.25 h−1, and volume ratio of hydrogen to heavy hydrocarbon stream ranging from 400 Nm3/m3 to 1000 Nm3/m3

The hydrocarbon stream having sulfur content of less than 100 ppm is then isodewaxed and fractionated to obtain a second distillate having boiling point in the range of 150° C to 350° C.

The second distillate is then subjected to selective hydrogenation in the presence of a mono-metallic nickel-based hydrogenating catalyst to obtain the de-aromatized hydrocarbon solvents aromatic content in a range of 5 ppm to 100 ppm and sulfur content in a range of 0.5 ppm to 1 ppm. In the most preferred embodiment, the aromatic content of de-aromatized solvent obtained is in a range of 20 ppm to 50 ppm.

The selective hydrogenation of the second distillate in the process is carried out at a reactor temperature ranging from 80 °C to 200 °C, reactor pressure ranging from 25 bar to 35 bar, liquid hourly space velocity (LHSV) ranging from 0.25 h-1 to 2.0 h-1, and volume ratio of hydrogen to second distillate ranging from 40 Nm3/m3 to 100 Nm3/m3. In the most preferred embodiments, the selective hydrogenation of the second distillate in the process is carried out at a reactor temperature ranging from 140 °C to 180 °C, reactor pressure ranging from 10 bar to 45 bar, liquid hourly space velocity (LHSV) ranging from 0.5 h-1 to 1.0 h-1, and volume ratio of hydrogen to second distillate ranging from 50 Nm3/m3 to 70 Nm3/m3.
The reactor pressure and volume ratio of hydrogen to second distillate is advantageously low in comparison to other processes for the preparation of de-aromatized solvents from hydrocarbons.
EXAMPLES:
Having described the basic aspects of the present invention, the following non-limiting examples illustrate specific embodiments thereof. Those skilled in the art will appreciate that many modifications may be made in the invention without changing the essence of invention.
Example 1: Preparation of mono-metallic hydrogenating catalyst
Example 1.1: Preparation of alumina support
Commercial pseudo boehmite (PB700, Pacific Industrial Development corporation, PIDC) is mixed with 0.1 N HNO3 solution to prepare a dough which is then extruded using a dye of 2 mm X 3 mm Trilobite, followed by drying for 12 hours at 120 ℃ and calcination at 500 ℃ with a heating ramp rate of 5 ℃ /min. The sample is then subjected to calcination for 4 hours in an open-air furnace to obtain alumina extrudes of Trilobite shape having diameter of 2mm X 3 mm.
Example 1.2: Preparation of Ni dispersed on alumina support
37.5 grams of alumina extrudes prepared as per the process disclosed in Example-1 above is then dispersed with nickel metal through spray impregnation wherein a solution containing 182 grams of Ni(NO3)2.6H2O in 70 ml of distilled water is sprayed on the extrudes and wet extrudes is dried under vacuum at 70 ℃ followed by e drying in an oven at 100 ℃ and further drying at 120 ℃ for 12 hours. The dried extrudes is then subjected to calcination at 450 ℃ at a heating rate 5 ℃/min for a duration of 5 hours in an open-air muffle furnace to obtain a catalyst comprising nickel metal dispersed on an alumina support.
Example 1.3: Preparation of Ni dispersed on alumina support though two-stage spray impregnation
37.5 grams of alumina extrudes prepared as per the process disclosed in Example-1 above is then dispersed with nickel metal through spray impregnation wherein a solution containing 96 grams of Ni(NO3)2.6H2O in 40 ml of distilled water is sprayed on the extrudes and wet extrudes is dried under vacuum at 70 ℃ followed by drying in an oven at 100 ℃ and further drying at 120 ℃ for 12 hours. The dried extrudes is then sprayed with a solution containing 86 grams of Ni(NO3)2.6H2O in 40 ml of distilled water and the wet extrudes is then dried under vacuum at 70 ℃ followed by drying at 120 ℃ for 12 hours. The dried extrudes is then subjected to calcination at 450 ℃ at a heating rate 5 ℃/min for a duration of 5 hours in an open -air muffle furnace to obtain a catalytic system comprising nickel metal dispersed on alumina support.
Example 1.4: Preparation of Ni dispersed on phosphorous modified alumina support
The alumina extrudes prepared as per the process disclosed in example 1.1 is sprayed with a phosphoric acid solution (H3PO4) containing 3 wt. % of phosphoric acid in 20 ml of water to obtain phosphorous modified alumina extrudes. 37.5 grams of this phosphorous modified alumina extrudes is dispersed with nickel metal through spray impregnation wherein a solution containing 182 grams of Ni(NO3)2.6H2O in 150 ml of distilled water is sprayed on the extrudes and wet extrudes is dried under vacuum at 70 ℃ followed by e drying in an oven at 100 ℃ and further drying at 120 ℃ for 12 hours. The dried extrudes is then subjected to calcination at 450 ℃ at a heating rate 5 ℃/min for a duration of 5 hours in an open-air muffle furnace to obtain a catalyst comprising nickel metal dispersed on phosphorous modified alumina support.
Example 1.5: Preparation of Ni dispersed on alumina support through 4 -stage spray impregnation
37.5 grams of alumina extrudes prepared as per the process disclosed in Example-1 above is then dispersed with nickel metal through spray impregnation wherein a solution containing 36.4 grams of Ni(NO3)2.6H2O in 20 ml of distilled water is sprayed on the extrudes and wet extrudes is dried under vacuum at 70 ℃ followed by drying in an oven at 100 ℃ and further drying at 120 ℃ for 12 hours. Similarly, 10% of metal loading is done in subsequent 4 steps and the final wet extrudes is dried under vacuum at 70 ℃ followed by drying at 120 ℃ for 12 hours. The dried extrudes is then subjected to calcination at 450 ℃ at a heating rate 5 ℃/min for a duration of 5 hours in an open-air muffle furnace to obtain a catalytic system comprising nickel metal dispersed on alumina support.
Example 2: Assessment of physical-chemical and mechanical characteristics of the catalyst
The physical-chemical and mechanical characteristics of the catalytic systems prepared in Examples-1.2, 1.3, 1.4, and 1.5 are assessed and the data is provided below in Table-1:
Table-1: Physical-chemical and mechanical characteristics of the catalyst

Example Surface area m2/g Pore volume
Cc/g Pore dia meter Angstroms Metal percentage By ICP
1.2 144 0.43 60 47.2
1.3 134 0.42 62 47
1.4 137 0.45 60 46.8
1.5 145 0.40 62 47

Example 3: Assessment of de-aromatization efficiency of the catalyst

A hydrocarbon feedstream comprising 8500 ppm of monoaromatics, 115 ppm of di-aromatics, and 52 ppm of poly-aromatics is subjected to a hydrogenation reaction in presence of mono-metallic catalyst prepared in Example-1.2, 1.3, 1.4, and 1.5 at a temperature of 160 ℃, pressure of 30 bar, H2/HC ratio of 100 Nm3/m3 and LHSV of 0.71 s-1 at 24 hours TOS and the amount of monoaromatics, diaromatics and polyaromatics in the output stream is ascertained to determine de-aromatization efficiency of the catalysts. The results are provided in Table-2 below:

Table-2: Content of monoaromatics, diaromatics, and polyaromatics in the output stream

Example Feedstream
[Overall aromatic content]
Out-put stream
[Content of mono aromatics in ppm] Out-put stream
[Content of di-aromatics in ppm) Out-put stream
(Content of poly-aromatics in ppm)
1.2 8667 432 ND ND
1.3 8667 29 ND ND
1.4 8667 116 ND ND
1.5 8667 200 ND ND
*ND: non detectable

Example 4: Obtaining low sulfur 2nd distillate from 1st distillate for production of de-aromatized hydrocarbon solvents
First distillate having IBP of 341 Deg C and FBP of 507 Deg C with sulfur of 1.2 wt% was hydrotreated at 348 Deg C, hydrogen to feed ratio of 664 Nm3/m3, WHSV 0.92 Hr-1, pressure 145 barg, using hydrotreating catalyst of Nickel-Cobalt on alumina. Then the hydrotreated stream was isodewaxed and fractionated to obtain second distillate having IBP of 160 Deg C and FBP of 336 Deg C having sulfur less than 1 ppm and aromatics 6800 ppm.
Table 3: Properties of First Distillate and second distillate
Properties First Distillate Second distillate
ASTM D86 (Deg C) IBP 341 160
5% 376 168
10% 386 186
20% 402 218
30% 411 243
40% 422 263
50% 430 280
60% 438 293
70% 446 304
80% 456 314
90% 470 324
95% 481 330
FBP 507 336
Sulfur ppm 12000 less than 1
Density gm/cc 0.8719 0.804
Aromatics ppm - 6800

Example 5: Time on stream study of mono-metallic hydrogenation catalyst prepared using Example 1.3 for production of de-aromatized hydrocarbon solvents
A Second distillate having feed sulfur of less than 1 ppm and total aromatics of 8260 ppm with monoaromatics of 8207 ppm and diaromatics of 53 ppm hydrogenated using catalyst prepared by method explained in Example 1.3 above at a temperature of 160 Deg C, pressure of 30 barg, LHSV of 0.7 Hr-1 and H2/Feed ration of 60 Nm3/m3 for 500 hours and found consistent product stream having aromatics less than 60 ppm and sulfurs stream less than 1 ppm.
Time (hr) Aromatics (ppm)
50 29
100 36
150 59
200 40
250 38
300 32
350 50
400 28
450 20
500 20
, Claims:1. A process for preparation of a mono-metallic hydrogenating catalyst, wherein the process comprises steps of:
(i) obtaining an extruded alumina support from an alumina dough, wherein the alumina dough is prepared by mixing alumina powder in an acid;
(ii) drying the extruded alumina support for a duration of 5 to 15 hours at a temperature range of 60 to 120 ℃ to obtain a dried alumina support;
(iii) calcining the dried alumina support at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours to obtain a calcined alumina support;
(iv) spraying a first precursor solution on the calcined alumina support to obtain a first stage nickel sprayed alumina support, wherein the first precursor solution is prepared by dissolving a salt of nickel in water;
(v) drying the first stage nickel sprayed alumina support in an oven at a temperature range of 60 to 120 ℃ to obtain a first stage nickel loaded alumina support;
(vi) spraying a second precursor solution on the first stage nickel loaded alumina support to obtain a second stage nickel sprayed alumina support, wherein the second precursor solution is prepared by dissolving a salt of nickel in water;
(vii) drying the second stage nickel sprayed alumina support to obtain a dried nickel loaded alumina support; and
(viii) calcining the dried nickel loaded alumina support at a temperature range of 450 to 550 ℃ for a duration of 2 to 10 hours to obtain the mono-metallic hydrogenating catalyst.
2. The process as claimed in claim 1, wherein the dried nickel loaded alumina support is further sprayed with a third precursor solution and subsequently with a fourth precursor solution with an intermittent drying step and wherein the third solution and the fourth precursor solution are prepared by mixing a salt of nickel in water.
3. The process as claimed in claim 1, wherein the alumina powder is selected from boehmite, pseudo boehmite, gibbsite, direct alumina, aluminum hydroxide, aluminum chlorides, aluminum sulfates, dawsonites, and a combination thereof, and wherein the alumina powder has surface area in range of 200 to 400 m2/gr.
4. The process as claimed in claim 1, wherein the acid is selected from nitric acid, acetic acid, phosphoric acid, and a combination thereof.
5. The process as claimed in claims 1-2, wherein the first precursor solution, second precursor solution, third precursor solution, and the fourth precursor solution contain salt of nickel in the range of 0.2 to 1.5 mol %, and wherein the salt of nickel is selected from Nickel (II) nitrate hexahydrate, Nickel (II) acetate tetrahydrate, and combination thereof.
6. The process as claimed in claim 1, wherein drying is carried out initially under vacuum at a temperature range of 50 to 100 ℃, followed by drying in an oven at a temperature range of 60 to 120 ℃, and then air drying at a temperature range of 450 to 550 ℃ for a duration of 4 to 12 hours.
7. A mono-metallic hydrogenating catalyst for producing de-aromatized hydrocarbon solvents through selective hydrogenation of a hydrocarbon feedstream, wherein the mono-metallic hydrogenating catalyst comprises 10 to 60 weight % of nickel metal dispersed on a refractory metal oxide.
8. The catalytic composition as claimed in claim 7, wherein the refractory metal oxide is selected from the group consisting of alumina, silica, titania, zirconia, and combination thereof.
9. The catalytic composition as claimed in claim 8, wherein the refractory metal oxide support is selected from alumina, a modified alumina, and a combination thereof.
10. The catalytic composition as claimed in claim 9, wherein the modified alumina is a phosphorous modified alumina.
11. The catalytic composition as claimed in claim 7, wherein the hydrocarbon feedstream is heavy and middle distillate having aromatic content ranging from 5000 ppm to 40000 ppm, and sulfur content ranging from 0 ppm to 1 ppm.
12. The catalytic composition as claimed in claim 7, wherein the nickel metal has reducibility in the range of 80 % to 90 % at a reduction temperature in the range of 440 to 480 ℃.
13. A process for preparing de-aromatized hydrocarbon solvents from selective hydrogenation of a hydrocarbon feedstream, wherein the process comprises steps of:
(i) distilling a heavy hydrocarbon feedstream to obtain a first distillate having boiling point in the range of 180° C to 550° C;
(ii) hydrotreating the first distillate in the presence of a hydrotreating catalyst to obtain a stream having sulfur content less than 100 ppm;
(iii) isodewaxing followed by fractionating the stream having sulfur content less than 100 ppm to obtain a second distillate having boiling point in the range of 150° C to 350° C; and
(iv) subjecting the second distillate to selective hydrogenation in the presence of a mono-metallic hydrogenating catalyst as claimed in claims 1-12 in a hydrogenation reactor to obtain the de-aromatized hydrocarbon solvents.
14. The process as claimed in claim 13, wherein the hydrotreatment is carried out at a reactor temperature ranging from 300° C to 450 °C, reactor pressure ranging from 60 bar to 180 bar, weight hourly space velocity (WHSV) ranging from 0.5 h−1 to 3.0 h−1, and volume ratio of hydrogen to heavy hydrocarbon stream ranging from 100 Nm3/m3 to 1500 Nm3/m3.
15. The process as claimed in claim 13, wherein the selective hydrogenation is carried out at a reactor temperature ranging from 80 °C to 200 °C, reactor pressure ranging from 10 bar to 45 bar, liquid hourly space velocity (LHSV) ranging from 0.25 h-1 to 2.0 h-1, and volume ratio of hydrogen to second distillate ranging from 40 Nm3/m3 to 100 Nm3/m3.
16. The process as claimed in claim 13, wherein the second distillate having aromatic content ranging from 5000 ppm to 20,000 ppm, and sulfur content ranging from 0 ppm to 1 ppm.
17. The process as claimed in claim 13, wherein the hydrocarbon feedstream is selected from crude oil, heavy vacuum gas oil, lube base oil, and a combination thereof.
18. The process as claimed in claim 13, wherein the hydrotreating catalyst is selected from a catalyst having active metals impregnated on a support selected from alumina, silica, titania, zirconia, and wherein the active metals are selected from cobalt, nickel, molybdenum, phosphorus, and a combination thereof.
19. The process as claimed in claim 13, wherein the de-aromatized hydrocarbon solvent has an aromatic content in a range of 5 ppm to 100 ppm and sulfur content in a range of 0.5 ppm to 1 ppm.