METHOD FOR OBTAINING SOLID PARAFFINIC COMPOUNDS BY HYDROTREATMENT OF VEGETABLE OILS

Description

TECHNOLOGICAL SECTOR

With the shortage of paraffinic crudes at global level and the consequent difficulty for obtaining solid paraffins in the refineries, the applicant has found that the direct hydrotreatment of oils or fats of organic origin offers an alternative for the production of solid paraffinic compounds, which have a wide application in different industrial fields as are candle manufacturing, waxed papers production, coverage of pharmaceutical products and foods, among others.

The solid paraffins derived from petroleum present a high content of carcinogenic pollutants, that doesn't allow them to be suitable for applications in the pharmaceutical or food industry, particularly by the presence of polynuclear aromatic hydrocarbons (PNA's). The paraffins obtained through the process of the present invention, lack such hydrocarbons, which make them optimal for the pharmaceutical and food industry.

STATE OF THE TECHNIQUE

Within the estate of the technique related with processes used for the obtaining of paraffins, there were found processes oriented to the synthesis of liquid paraffins, where they prevail the short chain paraffins, such as C₁₃ to C₁₈ paraffins.

The process of hydrotreatment of vegetable oils under certain operation conditions has been amply used in the production of liquid paraffins with properties similar to that of diesel. Within this field there have been developed different inventions that describe conditions to improve the characteristics of such product. Among them there can be found:

The patent application US 2007/0010682 from the company Neste Oil, that divulges a hydrotreatment process and isomerisation of mixtures of diluent agent (DA) with a content of up to 20% of fresh load (FL) (vegetable or animal oil or fat), to produce a hydrocarbon in the range of diesel. The operation conditions of this hydrotreatment are in the following ranges: 200 to 400° C. of temperature, 2.9 MPa to 15 MPa of pressure, and a diluent/fresh load ratio of 5 to 30:1.

In the patent U.S. Pat. No. 4,992,605, vegetable oils are hydro-processed to produce hydrocarbons, mainly C₁₅ to C₁₈ paraffins in the boiling range of diesel with a better cetane. This hydroprocess includes a hydro-cracking of the triglyceride structure, a hydrotreatment with the removal of oxygen and a hydrogenation with the saturation of the double bonds. The operation conditions of this process, for the crude palm oil, are: 350 to 450° C. of temperature, 4.8 to 15.2 MPa of pressure and an hourly space velocity between 0.5 to 5 h⁻¹.

Another document belonging to the state of the technique of the request US 2006/0207166, in which a hydro-oxygenation and a hydro-isomerisation to produce diesel with a good lubricity is done. The triglycerides of the load are deoxygenated removing O₂, as H₂O and CO, to form the C₁₄ to C₁₈ n-paraffins, then the hydro-isomerisation occurs to form the iso-paraffins. The used catalyst has a metallic and an acid component, the recommended one is Pt/SAPO-11. The hydro-cracking is inhibited, reason why the range of numbers of carbon is maintained in C₁₄ to C₁₈. The liquid product comprises water, C₁₄ to C₁₈ paraffins and naphthas. The obtained diesel contains C₁₄ to C₁₈ paraffins with less than 5 ppm of sulphur, with a iso-paraffin/normal paraffin ratio of 2 to 8, with less than 0.6% in weight of oxygenated compounds, with less than 0.4% in weight of fatty acids, with less than 10% in weight of alkyl-cyclohexane and less than 15% in weight of alkyl-benzene. With the isomerisation the lubricity is damaged but if the iso/normal paraffin ratio is increased, this property is improved. The hydro-oxygenation and hydro-isomerisation conditions are: 300 to 450° C. of temperature, 1.0 to 6.0 MPa of pressure, between 0.5 to 5 h⁻¹ of hourly space velocity and 500 to 2000 LN of H₂/L of load.

On its part, the patent request No. US 2006/0186020 reports a hydrotreatment process of mixtures comprising 1 to 75% in weight of vegetable oils and animal fats with fractions of mineral oil for the production of liquid paraffins, where the yield is of 95% v/v without the residues generation and a small production of propane. For every 100 liters of soy oil processed, there are produced 96 liters of liquid paraffin and 2.2 Nm³ of propane. The hydrotreatment conditions are: 320 to 400° C. of temperature, 4.0 to 10.0 MPa, 0.5 to 2 h⁻¹ of hourly space velocity and 200 to 1000 LN of H₂/L of load.

In this same field, it was located the request EP 0126168, related with a process for the selective reduction of edible oils and fats, that employs a catalyst and a fixed bed to carry out a hydrogenation process. The document teaches the hydrogenation method and the types of vegetable oils that can be employed, in which they are included the palm oil. This process employs nickel catalysts and the hydrotreatment conditions are: 150 to 260° C. of temperature, around 11.0 MPa and 0.2 to 20 h⁻¹ of hourly space velocity.

Within this context it is also found the patent U.S. Pat. No. 4,169,101, which object is a hydrogenation process of vegetable oils consisting in mixing a particulate catalyst with the oil current, for afterwards separating the catalyst by magnetic means. Also it is divulged that the process is carried out under a pressure between 5 to 20 MPa and a temperature between 180° C. and 230° C.

Lastly, it was found the patent request EP 1857525, which divulges a process for the obtaining of light n-paraffins from the hydrogenation of a mixture of vegetable and mineral oils in a ratio of 100:1 or 1:100 at a temperature of 250 to 400° C., 7.0 to 15.0 MPa, 0.5 to 2 h⁻¹ of hourly space velocity and 200 to 1000 LN of H₂/L of load.

Since the observed tendency is towards the depletion of paraffinic crudes, it persists the need to count with a reliable source of solid paraffins different from the ones from petroleum. According with the quoted requests, the existing inventions in the state of the technique are limited to the production of liquid paraffins, principally for the use as transport fuel. Therefore, its still required to develop a process through which high volumes of solid paraffins are obtained which characteristics allow them to be employed in pharmaceutical and alimentary applications.

Having into account the existing problem in the state of the technique, the applicant has developed a process based in the hydrotreatment of vegetable oils or animal fats that allows satisfying the permanent demand of such products.

SUMMARY OF THE INVENTION

In general the claimed process comprises steps of preheating, mixture of oil with hydrogen, heating, reaction, separation by decantation and eventually distillation or crystallization, as it is shown in FIG. 1. The sequence of the steps that characterize this invention are explained bellow:

Preheat the organic oil to a temperature between 50 and 100° C., to make it fluid and be able to transfer it to the following steps of the process. The oil and the hydrogen are mixed in the pipeline and are passed through a furnace to heat it to the desired temperature. Inside the reactor, the hydrogen reacts with the oil on the active sites of the catalyst at pressures between 2 and 11 MPa and temperature between 150° C. and 330° C., with an hourly space velocity between 0.2 and 6 h⁻¹. The employed catalyst is of fixed bed, composed of nickel and molybdenum oxides supported on alumina that were previously sulphurized for their activation. The hydrated product exits the lower part of the reactor and passes to a level separator, where the gas is removed through the upper part and the hydrated liquid product through the bottom. This last, is composed of two phases (water and paraffin), which are separated by decantation and according with the desired concentration of high molecular weight paraffins it can be done a distillation separation step, to remove the paraffins with lower molecular weight.

The operational conditions, that is, pressure, temperature, hourly space velocity and hydrogen/load ratio, to obtain the product in a solid state in the reaction step, are specific for each catalyst, either fresh or used, and are determined according with a pre-established protocol.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Scheme of the hydrotreatment process of palm oil for the obtaining of solid paraffins

DETAILED DESCRIPTION OF THE PROCESS

In FIG. 1 it is presented the detail of the flow diagram of the hydroteatment unit where the solid paraffin is obtained. The load to process, that in this case is vegetable oil or animal fat, is introduced in the load drum (1), from where it is pumped and mixed (2) with the hydrogen to pass to the heating furnace (3) where the oil/hydrogen mixture acquires the adequate temperature to pass to the reactor (4).

The products of the reaction pass to the decanting separation system (5), that generally is formed by various steps to achieve the required qualities. The most convenient conformation of the steps of decantation separation are well known and used by the hydrotreatment industry. In this step there are obtained three main currents: one gaseous conformed by hydrogen along with the reaction gases; one liquid phase constituted by the obtained products from the oil and another liquid phase corresponding to the by-product water of the reaction (C).

Depending on the required physical characteristics for the solid paraffin it could be needed a separation by distillation (8) to separate the lower molecular weight paraffins that are in the range of the diesel (B) from the paraffins and solid compounds (A).

The gaseous phase obtained in step (5) passes to a cleaning step (6) to purify the hydrogen from gases produced during the reaction such as CO, CO₂ and methane by washing techniques known in the industry, to obtain a high purity hydrogen which is compressed (7) and is mixed with the replacement hydrogen to maintain the stock and is recycled before the steps of heating and reaction.

DETAILED DESCRIPTION OF THE INVENTION

As previously indicated, the claimed process comprises the steps shown in the flow diagram of FIG. 1, where from the storing tank (1), with heating, the vegetable oil, from algae or other vegetal origin or animal fat its pumped to the furnace (3). The vegetable oil or the animal fat is combined with the hydrogen in the mixer (2), which can be located before or after the furnace (3), where the load is heated to the desired temperature at the entrance of the reactor (4). In the reactor (4), the reaction is done, that being exothermic it makes the load temperature to rise as it goes through the catalytic bed. The product from the reaction is taken to a separating reservoir (5) where the gaseous hydrogen is recovered to purify it (6) and recycle it to the process. The water and the solid paraffinic compounds that due to the high temperatures of the process remain in liquid state are separated by decantation. Such paraffinic compounds are recovered for their storage.

Eventually it could be required an additional step of separation by distillation, crystallization or any other technique known by the industry to remove the low molecular weight paraffins and thus obtain a product of greater melting point (8).

The sequence of the steps that characterize the invention is explained in detail bellow:

• • 1. Pre-heat the oil or fat until the temperature is between 50 and 100° C., to maintain it in liquid state and ease its transport through pumping to subsequent processes.
  • 2. Mix the pre-heated oil or fat with the hydrogen inside the transport pipeline.
  • 3. Heat the mixture in a furnace to the reaction temperature, which is between 150° C. and 330° C., depending on the quality of the catalyst. The exact temperature of this step of the process is determined for a given system, increasing the temperature of the load until achieving the desired quality in the product.
  • 4. Pass the mixture from step 3 through a reactor full of a selected catalyst from a group that comprises CoMo, NiMo, NiW, CoW, which have been subjected to a sulphurization process and supported on γ-alumina. The hydrotreatment reaction is done at a temperature between 150° C. and 330° C., a pressure between 2 MPa and 11 MPa, an hourly space velocity between 0.5 h⁻¹ and 6 h⁻¹ and a ratio of hydrogen per load of oil between 300 L of H₂ per liter of oil and 500 L of H₂ per liter of oil, which allows that the reactions that transform the oil into solid paraffins, happen.
  • 5. Collect the product of the previous step in closed reservoirs and separate them by decantation in three phases: water, solid paraffins and gases. These currents are separated physically by techniques sufficiently known or used by the industry. The obtained gases can be employed as fuels in the refinery or can be separated and purified to recover the hydrogen, which is re-circulated to the process.
  • 6. If necessary the solid paraffins are taken to a separation process by distillation or crystallization where the lighter molecules are separated from the heavy ones according to the quality that is required.

The reaction operational conditions, that is, pressure, temperature, hourly space velocity, to obtain the product in a solid state are specific for each catalyst, either fresh or used, and are determined according with a pre-established protocol in which two variables are fixed and the third is established with the purpose of preventing the formation of light paraffins. Without abiding to any theory, the applicant considers that in this way the hydrotreatment reaction is interrupted before the molecules are saturated with hydrogen, with which free radicals are produced that then are combined forming high molecular weight paraffinic compounds, which are solid at room temperature.

In one preferred mode the catalyst is a fresh or used catalyst that comprises a support of porous alumina impregnated with metallic sulfides of Ni and Mo or of Ni and Co.

Preferably, the vegetable oil is selected from the following group of oils: soy oil, palm oil, canola oil, castor oil, jatropha oil, among others.

Although this invention has been presented in its preferred mode, the description can be considered enough to allow those versed in the technology to put the invention into practice.

Also, it makes part of the invention that is claimed here, the solid paraffinic compounds obtained from the process defined in the previous paragraphs, which have demonstrated a C₁₃ to C₁₈ paraffin content bellow to 25% in weight of the total of the paraffin produced.

Currently the solid paraffinic compounds that are produced through the process here described have its principal use in the elaboration of candles. Likewise, the paraffinic compounds obtained are of high refinement and purity and are safe to use as paper coatings for packing, prepare, transport, treat or store food with which it must be in contact with.

Because of its impermeability and strong structure the solid paraffins of the invention can also be employed in corrugated contents to pack vegetables, fruits, meat, fish and cheeses; as well as in paper cups. They are also used in the lid of the canned foods to prevent the food from dehydration and mold formation. In addition, they are added to chewing gum due to its plasticity.

Bellow there are exposed some examples of the best realization of the invention. This inventive process is not limited in its scope by the examples presented so these are a simple illustration and serve as base for other modifications and alterations introduced in the context of the inventive concept, which can be practiced as long as they are not deviated from the essential concept.

Example 1

With the purpose of studying the hydrotreatment of crude palm oil as an option to obtain solid paraffins, the load was subjected to hydrotreatment with high purity hydrogen in a fixed-bed reactor, in its inside loaded with three different beds of NiMo catalyst supported on previously sulphurized alumina, under the operation conditions of table 1. These tests were done in the hydrotreatment pilot plant.

TABLE 1
Severity of example 1 from HDT of ACP

	Temperature	Pressure	Residence Time	H2/load ratio
	(° C.)	(MPa)	(h − 1)	(LN/L)
	300	9	6	472

In tables 2 and 3 it can be observed the analytic results of the solid paraffin obtained in the pilot plant, which has a low content of aromatics.

TABLE 2
Physical-chemical characteristics of the solid paraffin.

			Paraffin
	TEST	Unit	Pilot plant

	Waxes Content	% p/p	21.2
	Fluidity point	° C.	33
	Cloud point	° C.	34
	Flashpoint	° C.	35
	Combustion heat	MJ/kg	44.468
	Viscosity at 40° C.	mm2/s	6.6
	Water and sediment content	% V	0.2
	Density	g/ml	0.8
	API	° API	41.7
	Water content	ppm	5203
	Acid number	mgKOH/g	6.8

TABLE 3
Chemical composition of the solid paraffin

	Cuts Table - Simulated
	Distillation	% in weight of product
	Initial boiling point-221° C.	0.9
	221° C.-344° C.	64.9
	344° C.-final boiling point	33.2
	% recovered (Off)	100
	Masses	%
	Paraffins	57.11%
	Cyclo paraffins	9.05%
	Olefins	19.65%
	Alcohol	0.34%
	Carboxylic Acid	0.19%
	Aldehydes	0.75%
	Other compounds	12.92%

In table 4 there are registered the results of the comparative analysis of the absorbance for the paraffin of the invention and the paraffin obtained from a petroleum derivative, compared with the established standards for paraffin according to the FDA.

TABLE 4
Comparative analysis of the absorbance of different paraffins.

				Petroleum
		FDA	Paraffin from	derived
	UV	Standards	the invention	Paraffin
	Absorbance	(max.	(max.	(max.
	(nm)	absorbance)	absorbance)	absorbance)
	280-289	0.15	0.17	0.198
	290-299	0.12	0.12	0.238
	300-359	0.06	0.10	0.167
	360-400	0.02	0.02	0.129

Example 2

Runs were made, modifying the reaction temperatures and the hourly space velocity of example 1, which are presented in table 5.

TABLE 5
Severity of example 2 of HDT of ACP

	Temperature	Pressure	Hourly Space	H2/load ratio
	(° C.)	(MPa)	velocity (h − 1)	(LN/L)
	310	9	2	472
	300	9	2	472
	280	9	2	472
	260	9	2	472

In tables 6, 7 and 8 there are presented the analysis of the paraffins obtained with the invention process at the temperatures indicated in table 5. In table 8 they are reported the maximum absorbance values obtained in the ranges of wavelength defined by the standard FDA 21CFR 172.886 for petroleum waxes and the obtained in this invention.

Specifically in table 6 it can be observed how as the reaction temperature lowers the water formation decreases, while in table 7 it can be observed that as the temperature is reduced the quantity of obtained product in the cut of 334° C. —FBP increases and the quantity obtained in the cut 221° C.-334° C. decreases; by mass analysis the presence of aromatics is not found, main characteristic for the application of these paraffins as nutritional grade.

TABLE 6
Physical-chemical characteristics of the produced
paraffins at different temperatures

		Paraffin -	Paraffin -	Paraffin -	Paraffin -
Test	Unit	310° C.	300° C.	280° C.	260° C.

Volumetric	%	96.2%	105.6%	98.7%	96.2%
yield
Water	%	2.7%	2.1%	0.8%	0%
Density	g/mL	0.821	0.848	0.874	0.8915
Penetration	mm/10	64.5	50.7	28.6	23.5
in waxes
at 25° C.
API Gravity	° API	41	35	30	27.1

TABLE 7
Chemical composition of the paraffins
produced at different temperatures

	Paraffin -	Paraffin -	Paraffin -	Paraffin -
	310° C.	300° C.	280° C.	260° C.

Cuts Table -
Simulated
Distillation
IBP-221° C.	% weight	1	1	1	0
221° C.-	% weight	50	30	13	6
344° C.
344° C.-FBP	% weight	49	69	86	94
% recovered	% weight	100	100	100	100
(Off)
Masses
Paraffins		39.6%	22.8%	11.2%	7.8%
Cyclo-		9.5%	6.1%	6.4%	8.7%
paraffins
Olefins		15.9%	11.2%	10.2%	13.3%
Esthers		3.3%	4.3%	14.3%	1.9%
Carboxylic		0.2%	4.0%	4.4%	2.9%
Acid
Aldehydes		0.2%	0.6%	0.2%	0%
Aromatics		0%	0%	0%	0%
Total		68.8%	49.1%	46.8%	34.7%

TABLE 8
Analysis of the absorbance of the paraffins
produced at different temperatures

UV	FDS	Paraffin -	Paraffin -	Paraffin -	Paraffin -
Absorbance	Standards	310° C.	300° C.	280° C.	260° C.

Nm	Maximum absorbance

280-289	0.15	0.10	0.02	0.01	0.02
290-299	0.12	0.09	0.02	0.01	0.02
300-359	0.06	0.09	0.02	0.01	0.01
360-400	0.02	0.06	0.01	0.005	0.01

Example 3

In this example, there are reported the results of a solid paraffin obtaining process at a temperature of 230° C., pressure of 9 MPa, hourly space velocity of 2 h⁻¹ and a H₂/load ratio of 472 LN of H₂/L of load, with a fresh high activity catalyst. These paraffins posses a solid content above 90% at a temperature of 20° C. and above 80% at a temperature of 40° C.

In table 10 there are presented the results of the physical-chemical properties of the paraffin. These paraffins posses excellent hardness characteristics, as well as a melting point above 45° C.

TABLE 10
Physical-chemical characteristics of the
solid paraffins obtained at 230° C.

	Unit	Paraffin - 230° C.

Analysis
Acid Number	mg KOH/g	10.6
Flashpoint	° C.	148.0
Kinematic Viscosity at 100GR	mm2/s	7.0
Density at 15 GR C	g/mL	0.9
Solid fat content at 20° C.	% weight	97.6
Solid fat content at 40° C.	% weight	81.1
API gravity	° API	27.2
Fluidity point	° C.	47.2
Melting point	° C.	53.5
Water content	g/Kg	4.4
Penetration in wax at 25° C.	mm/10	12.0
Combustion heat	MJ/kg	40.0
Masses
Paraffins	% weight	16.13%
Cycloparaffins		5.61%
Olefins		3.82%
Esthers		27.51%
Carboxylic acids		0.47%
Aldehydes		0.05%
Aromatics		0.01%
Others		0.28%
Total		53.6%

In table 11 there are presented the results of the maximum absorbance of the paraffin at 230° C., likewise it is observed that at these low temperatures the paraffins comply with the FDA established standard.

TABLE 11
Analysis of the maximum absorbance
of the solid paraffin at 230° C.

UV Absorbance

FDA Standard

Paraffin - 230° C.

(nm)	Maximum absorbance

280-289	0.15	0.01
290-299	0.12	0.01
300-359	0.06	0.01
360-400	0.02	0.00