Production of Naphta from Waste Triacyglycerols

7/28/2019 Production of Naphta from Waste Triacyglycerols

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PRODUCTION OF DIESEL FUELS FROM WASTE TRIACYLGLYCEROLS BYHYDRODEOXYGENATION

J. Mikuleca,*, J. Cvengrob, . Jorkova, M. Bania, A. Kleinovb

aSlovnaft VRUP, Bratislava, Slovak Republicb

Faculty of Chemical and Food Technology, Slovak University of Technology,Bratislava, Slovak Republic

Abstract

The study is devoted to the issue of direct transformation of triacylglycerols (TAG) to dieselfuels applying a commercially available NiMo and NiW hydrorefining catalysts. It was

proved that TAG can be converted to the fuel biocomponent by adding 6.5 % (vol.) of TAGto atmospheric gas oil. In this way, after hydroprocessing at mild conditions (temperature320360 C, pressure 3.55.5 MPa, LHSV = 1 h-1 and ratio H2:HC = 5001000 Nm

3/m3,catalyst presence), gas oil containing 55.5 % of biocomponent was prepared, characterizedwith standard performance and emission parameters. Long-term stability test of the catalyst

was carried out and sufficient catalyst life was confirmed. Performance and emission testsdocumented that even 5 % (vol.) portion of bio-components reduces the controlled anduncontrolled emissions.

Keywords: hydrodesulphurisation, hydrodeoxygenation, decarboxylation, triacylglycerols,atmospheric gas oil, hydrorefining catalysts

1 Introduction

Natural triacylglycerols (TAG) present in vegetable oils or animal fats can act as a suitableraw material for producing high-quality engine fuels. Given their high molecular weight and

low volatility, they are not appropriate for the use in diesel engines without constructionchanges of the engines. Transesterification of natural TAG with methanol or ethanol is anindustrially applied process for fatty acids methyl and ethyl esters (FAME, FAEE) production.

The qualitative parameters of FAME are comparable with fossil diesel quality. FAME areused as an oxygenate components in diesel fuels in up to 5 % vol. The FAME drawback ismainly high price and increased requirements on feedstock quality. The use of FAME isconditioned by a certain adjustment of the equipment when blended with fossil diesel fuel(DF). The fossil fuel blended with FAME is less oxidation-resistant and its long-term storageis not recommended.

Direct conversion of TAG to liquid hydrocarbon fuels is a prospective technology ofchemical industry. Of the feasible processes such as catalytic cracking and hydrocracking the

processes occurring in the presence of hydrogen seem to be more promising.TAG present in vegetable oils and/or animal fats are transformed in the presence ofhydrogen and hydrorefining NiMo, CoMo, NiW/-Al2O3 based catalysts are converted tohydrocarbons, mainly to n-alkanes at the temperatures above 300360C and pressure at least3 MPa leaving propane and CO2 as side-products [1,2,3,5,6]. The mechanism of the reactionis complex and consists of series of consecutive steps, the fastest one being TAG transformation tofatty acids.

In the process, three parallel reactions occur: hydrogenation, hydrodeoxygenation anddecarboxylation. In hydrogenation-hydrodeoxygenation, n-paraffins with an even number ofcarbon atoms corresponding to related fatty acids in the used oils/fats, mainly n-C16 and n-C18are formed along with water and propane. In case of hydrogenation-decarboxylation, the

products comprise CO2, propane and n-paraffins with an odd number of carbon atoms inmolecules (mainly n-C15 and n-C17), usually lower by one than that in the used TAG acyls [5,6].

44th International Petroleum Conference, Bratislava, Slovak Republic, September 21-22, 2009 1


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Cyclization, aromatization and isomerization are side processes. Increasing the temperature,the decarboxylation rate prevails over that of hydrodeoxygenation [1,20,21].

It has been documented that appropriate selection of the catalytic system allowsinfluencing the main process products [1] as well as the formation of cyclic structures. Adegree of unsaturation in TAG chains has an impact on the extent of cyclization in the

product. The content of cycloalkanes and alkylbenzenes increases with a degree of

unsaturation in the original oil [1]. A higher partial pressure of hydrogen suppresses theformation of olefins, cyclanes and aromates.Since fatty acids are formed in the initial step of TAG conversion, the process was

investigated also using model fatty acids and their esters in order to clarify the reactionmechanism. As a catalyst, Pd on various supports was applied [9,10]. Catalytic conversion ofthe fatty acids has mainly a character of decarboxylation. In case of the fatty acid esters,decarbonylation was the key reaction route [12,13,14].

The product of hydrocracking is usually separated into three fractions by distillation:petrol, diesel fuel, and distillation residue. Due to its high cetane number (CN), the middlediesel fuel distillate is called also Supercetane [17]. Such fuel is comparable with DF, itsviscosity is similar to that of FAME. It is miscible with DF in any ratio and is well

biodegradable. The high cetane number (CN), 5590, is comparable to that of commercialadditives used to increase the CN [23]. An increased CN manifests in emissions reduction(THC, NOx, PM, CO). As its drawback, low-temperature properties caused by a high contentof n-alkanes C15C18 should be mentioned. CP (cloud point) and CFPP values range from 20to 23 C [20]. Catalytic hydroisomerization may be applied to solve the problem. In thefunction of catalyst, Pt anchored to zeolite HZSM 22 [15] was used. The process occurs at thetemperature range of 280370 C, pressure 3.58 MPa, and LHSV 14 h-1. CFPP of the

product ranges from -18 to -14 C. Catalyst is, however, sensitive and becomes easily deactivated.The fuel produced through hydrogenation conversion of TAG complies with the existing

standards, no new standards are needed. In the process, to obtain a standard-quality productalso low-quality oils/fats can be treated [16,18,19] .

From the viewpoint of technology, TAG can be processed in an individual unit or toperform its conversion in a blend with light gas oil or vacuum gas oil [19]. An advantage ofthis mode lies in a lower investment cost [18]. Hydrocracking of vacuum gas oil blended withTAG was successfully carried out, too [20].

The employment of convention refinery technologies as well as hydrorefination catalystsrepresents also a benefit of hydrogenation cracking [1,2]. In the process, no unusual side

products are formed, all of the products are processable in refinery streams. The economy ofthe process is more favourable than that of transesterification process. It is estimated that thecost of processing (except for that of incoming oil) represents 50 % of transesterificationrelated costs [23]. Investment expenditures of production unit establishment are, however,

higher by 50 %.At the time being, the processes of the company Neste Oil [25,26,28] and Ecofinning,jointly offered by UOP and Eni [27,35] are at disposal.

The present contribution is aimed at verifying the possibility to transform TAG blendedwith light gas oil in the process of hydrogenation refining. This mode would offer anadvantage of lower investment cost for implementation. Transforming TAG in an individualoperation in the absence of crude oil fractions will be studied. By the experiments, availablesources of TAG such as rapeseed, sunflower, or palm oils, lard and unconventional source ofhigher fatty acids such as tall oil will be used. Evaluating the parameters of the obtained

products applying common procedures of DF assessment, including performance andemission characteristics and comparing them with those of DF are also the targets of the study.



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2 Experimental

Catalytic conversion of TAG in a blend (6.5 % vol.) with atmospheric gas oil has beenperformed in flow apparatus, in a tubular reactor (the total volume 250 ml) with catalytic bedof 100 ml, feed range 100 1 000 ml/h, maximal operation temperature 600 C, maximaloperation pressure 100 bar. The device was equipped with the regulation of pressure,temperature, feedstock loading and reaction products discharging. Feedstock container and

pipelines were heated to decrease the viscosity and to maintain the possibility of animal fats feeding.Reaction feedstock is pumped by a piston pump and mixed with reaction gas on the head

of the reactor. Formed mixture, depending on the amount of the catalyst, passes through abed, which is, based on the reaction conditions, placed in the reactor body, where the reactionproceeds. The formed product passes subsequently through a water cooler to a separator,where reaction gas is separated from the product.

Liquid sample is withdrawn continuously, as this equipment has individual level gauge thatenables to set a sample amount. Reaction gas, after being discharged from the separator,

passes through a gas flow meter allowing both controlling and measuring its amount.Hydrogen containing gas products were released to the atmosphere by gas meter.

2.1 Feedstock

In the first test series, optimal conditions for conversion of TAG (fatty acid composition -acyl profile see Tab. 1) to hydrocarbons were searched for. In the second part, the optimalconditions were verified using various feed stocks differing in acyl profiles. In the third partof tests, a long-term test of catalyst stability and production of higher amount of sample forapplication tests were performed. Among the sources of acyls, the following feed stocks wereused: refined rapeseed oil, refined sunflower oil, lard, palm oil and crude tall oil.

Table 1 Acyl profile of materials used by hydroprocessing study, wt. %

Fatty acidRapeseed oil,

refinedSunflower oil,

refinedPalm oil,refined Lard

C14:0 0.06 0.07 1.0 1.5C14:1 0.00 0.00 0 0C16:0 4.64 6.15 35.4 31.2C16:1 0.24 0.07 0.3 0C18:0 1.96 3.80 3.8 16.5C18:1 63.47 22.09 45.1 42C18:2 20.01 66.62 13.4 6.6C18:3 6.97 0.12 0.3 0C20:0 0.60 0.25 0.3

C20:1 1.18 0.23 0C22:0 0.15 0.05 0C22:1 0.07 0.08 0C24:0 0.13 0.03 0C24:1 0.14 0.18 0The ratio in the first column of Tab. 1 indicates number of carbon atoms:number of double bonds. At the

experiments, tall oil with acid value of 139 mg KOH/g was also used. The share of fatty acids was about 41 %

wt., the share of rosin acids was about 32 % wt. and neutrals (unsaponifiables, esters and other non-acidic

components) of about 27 % wt.

Crude vegetable oils and animal fats contain 9597 % wt. of TAG. Minority componentsare mono- and diacylglycerols, phospholipides (lecithines 12 %), free fatty acids (0.30.7

%), unsaponifiable matter like tocopherols (0.10.2 %), sterols (about 0.3 %) and terpenehydrocarbons (squalene), then traces of metals (Ca, Mg, Fe, Cu). Refined oils contain morethan 99 % wt of TAG; the content of minority components is rapidly lowered (traces of



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metals Ca and Mg about 1 ppm, Fe about 0.1 ppm, Cu about 0.03 ppm). Tall oil is obtained asa by-product of the Kraft process of wood pulp manufacture. It contains free fatty acids(mainly oleic and linolic acids) 3050 %, rosin acids like pimaric and abietic acid 4060 %and unsaponifiable matter 1015 % containing sterols (24 %), fatty alcohols, phenols andhydrocarbons. Vacuum distillation in wiped film evaporator is usually used for crude tall oilfractionation to the enriched fatty acid fraction, rosin acid fraction and tall pitch.

The common hydroprocessing of atmospheric gas oil produced (see Tab. 2) by crude oildistillation, 5 % (vol.) or 6.5 % (vol.) of refined rapeseed oil was final possibility to preparerenewable diesel. Common hydrorefining and hydrodeoxygenation was carried out attemperature 320360 C, pressure 3.55.5 MPa, LHSV = 1 h -1 and ratio H2:HC = 5001000

Nm3/m3. During the tests procedure, the formed hydrogen sulphide was stripped off bynitrogen. In one series of experiment the feedstock was diluted with an inert solvent isooctane.

Table 2 Atmospheric gas oil properties

Characteristic Unit Value

Distillation range oC 193371,8

Density, 15 C kg/m3 851.9

Sulphur content mg/kg 7613

Cetane number 53.2

Flash point oC 74.5

Cloud point oC -4

CFPP oC -3

Pour point oC -10

2.2 Catalysts

As a basic benchmark catalyst, the commercial NiMo/-Al2O

3catalyst in sulphidic form

was used. The catalyst is applied to desulphurize gas oils used in production of DF containingless than 10 mg/kg of sulphur. Sulphurization was performed directly in a reactor in a streamof hydrogen at a pressure 3 MPa using 5 % solution of dimethyldisulphide in gas oil. Thecatalyst was dried at 120 C in a stream of nitrogen. The temperature gradually increased withthe gradient 100 C/h up to 350 C, it was kept for 1 h at 250 C and for 4 h at 350 C.Sulphurization was successfully carried out in an autoclave, too.

Moreover, the catalysts NiMo (6 % NiO, 25 % MoO3) and NiW (6 % NiO, 25 % WO3)were prepared. The catalysts were prepared by impregnation of a support with the solutions ofnickel (II) acetate, sodium molybdate (VI) or sodium tungstate (VI). Subsequent to drying at120 C, the prepared catalysts were calcinated for 4 h at 550 C. Supports TiO2, ZrO2, Al2O3

were purchased from the company Eurosupport Manufacturing Czechia, Litvnov, CZ, NaYwas prepared in Slovnaft VRUP, Bratislava.The oxide-based catalysts were converted to the corresponding sulphides by the above

mentioned procedure in autoclave. Tab. 3 provides basic characteristics of the catalysts usedin testing. The specific surface area was determined with an instrument ASAP2400(Micromeritics). Activation of samples before measurement: temperature 350 C, vacuum 2Pa, duration 12 h. Specific surface area SBET was calculated from linearized BET izotherm ina standard range of relative pressure p/p0 (0.050.30). The total volume of pores V0.99 wasdetermined from the adsorbed volume of nitrogen at relative pressure p/p0 = 0.98. Specificvolume of micropores Vmicro and specific surface of mesopores (+ external catalyst surface) Stwas calculated by the t-line method in the range of t (0.350.5 nm). Acidity was determined

using the method of temperature-programmed desorption of ammonia (TPDA). Samples (300mg, 0.10.3 mm) activation before measurement: in a stream of helium up to 500 C.



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The catalyst NiW/NaY contains 45 % of micropores and the rest are mezopores frombinder. The catalysts on basis TiO2 and ZrO2 are practically pure mezopores ones. Al2O3catalyst contains only minimal share of micropores.

Table 3 Adsorption properties and acidity of investigated catalysts

Catalyst NiW/NaY NiW/TiO2 NiW/ZrO2 NiMo/TiO2 NiMo/Al2O3

Specific surface area, SBET(mg/g) 207 59 159 28 193Specific volume area ofmicropores, Vmicro (cm

3/g)0.092 0.002 0.000 0.002 0.005

Specific surface area ofmesopores, St (cm

2/g)31.3 54.0 159 24.9 181

Total volume of pores,V0,98 (cm

3/g)0.203 0.287 0.420 0.179 0.486

Pore diameter (A) 1001000 300 85 240 190

Acidity TPDA (mmol H+/g) 0.190 0.120 0.164 0.012 0.320

2.3 AnalysesReaction gas was sampled to bags and analyzed using gas chromatography according to

UOP 539-87 with a Shimadzu instrument GC 17 A fy Shimadzu. In the system comprisingthree columns and two switch valves, oxygen, nitrogen, CO2, CO, hydrogen and lighthydrocarbons (methane to n-pentane) are separated. Hydrocarbons heavier than n-pentaneelute in one peak. Types of columns: molecular sieve, precolumn: 5m x 0.53mm x 3m SE54, analytical column: 60 m x 0.53 mm SILICA PLOT.

Distribution by boiling points (simulated distillation) was determined according to standardASTM D 2887 with a AMS 94 device, column: RMX1 15m x 0.53 mm x 2.65 m, detector: FID.

GC analyses of liquid products were performed according to standard ASTM D 5134 usinga device TRACE GC 2000 INSTRUMENT. Column: WCOT FUSED SILICA 50m x 0.32mm x 1.2 m CP SIL 5CB, detector: FID.

Because the products contained mainly n-alkanes, it was advantageous to use ASTM D5442 method for evaluation.

FIA analysis was used to prove the unsaturated hydrocarbons presence. Evaluation of DFwas done using methods prescribed in standard STN EN 590.

2.4 Engine and emission tests

Measurements of the performance and emission characteristics were realized using avehicle VW Touareg R5 2.5 UI (Unit Injection System), year of production 2007. Basiccharacteristics of the engine are given in Tab. 4.

Table 4 Engine specification of VW Touareg R5 (UI)Number of cylinder 5Bore (mm) stroke (mm) 81 95.5Volume (L) 2.5Compression ratio 19.5:1Maximal load (kW/rev) 128/3500Maximal torque (N m/rev) 400/2000

Measurements of performance parameters were carried out using the chassis dynamometerMAHA LPS 2000 (MBH Haldenwang/Allgu, Germany). Emission measurements were

performed with an exhaust gases analyser MAHA MGT5 by means of the emission

determination at steady-state regime during idle running and the constant speeds of 60, 90 or120 km/h. Diesel engine opacity determination was performed by the method of freeacceleration with a dynamometer AVL DiSmoke 435. Along with measurements of regulated



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emissions, determination of unregulated emissions, namely of VOC (volatile organiccompounds) and carbonyls were performed. VOC were determined with an analyser BernathAtomic equipped with a FID detector. Aldehydes and ketones were determined as described in[36,37].

3 Results and discussion

3.1 Effect of temperature, pressure and space velocity on catalytic transformation of

rapeseed oil

The results of rapeseed oil hydrodeoxygenation (HDO) are gathered in Tab. 5 and 6. Withincreasing temperature at the constant hydrogen pressure, the content of n-alkanes with anumber of carbon atoms lower by one as that in the raw material increases, which documentsa dominance of reaction (1), i.e. fatty acid hydrodecarboxylation (HDC). A rise in temperatureleads also to a higher extent of secondary reactions yielding aromatics, mostly those with onearomatic ring. Comparing the chromatograms obtained using the phases differing in polarity itwas shown that olefins were separated and identified. With raising temperature and pressure,the content of olefins decreases. A higher partial pressure of hydrogen at the constant

temperature prefers reactions of HDO, suppresses olefin formation in favour of alkanes, theformation of aromatics is not significantly influenced. It exhibits a favourable impact on fattyacids transformation to hydrocarbons. A space velocity decrease exhibits a similar effect.

Table 5 Hydroconversion of rapeseed oil, effect of temperature

Hydroconversion conditions:

Temperature, C 330 340 350Pressure, MPa 3LHSV, h-1 1H2:TAG, Nm

3/m3h 250

Product: Composition, % wt.:

< n-C14 0.26 0.31 0.35n-C15 2.84 3.09 3.35n-C16 2.51 2.43 2.27n-C17 49.35 51.16 53.32n-C18 35.95 33.40 29.09> n-C18 1.51 1.54 1.50Isoalkanes, cycloalkanes,olefins

5.59 6.34 8.31

Aromatics 0.95 1.27 1.54Polar substances 1.06 0.45 0.26

At the temperature above 360 C, space velocity 0.81 h

-1

, pressure of hydrogen at least4.5 MPa and the ratio H2:TAG = 1000 and more, the TAG conversion is quantitative and doesnot lead to polar substances and olefins. Using other catalysts, the above conditions may be milder.

We have also tried out to apply hydrogen in high excess and to use an inert solvent isooctane. Such a change has a positive effect on the course of HDC and HDO reactions. Ascan be seen in Fig. 1, the dependence of HDC and HDO reactions on temperature and

pressure is similar but HDO reactions are more favored under the same conditions(temperature, pressure).



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Table 6 Hydroconversion of rapeseed oil, effect of pressure


Pressure, MPa 3.5 4.0 4.50Temperature, C 340LHSV, h-1 1H2:TAG, Nm

3/m3h 250

Product: Composition, % wt.:

< n-C14 0.40 0.27 0.37n-C15 3.81 2.54 2.86n-C16 3.39 2.70 3.00n-C17 49.12 49.28 46.26n-C18 34.06 37.12 38.94> n-C18 0.84 1.80 1.29Isoalkanes, cycloalkanes,olefins

7.02 5.03 5.96

Aromatics 1.15 1.09 1.17Polar substances 0.20 0.18 0.13

290 300 310 320 330 340 350 360 370 380 390

reaction temperature, oC

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

ratio

n-C17

/n-C18

ratio n-C17/n-C18, p=4,5 MPa, H2:TAG=1000,diluted with isooctane

ratio n-C17/n-C18, p=5,5 MPa, H2:TAG=1000, diluted with isooctane

ratio n-C17/n-C18, p=3 MPa, H2:TAG=250

Figure 1 Hydroconversion of rapeseed oil. Temperature dependence of n-C17/n-C18 ratio

Mechanism of TAG conversion over hydrotreating catalyst in the presence of hydrogenand elimination of oxygen from a TAG molecule is an intricate process that needs to beverified using a simpler system. Real raw materials contain also other compounds that mayhave an effect on the catalytic system. In the initial stage of our experiments we were

evaluating, in a continuous reactor with NiMO/Al2O3 as the catalyst, the effect oftemperature, hydrogen pressure and space velocity on the course of chemical reactions. Weworked intentionally also in the range below the process optimum parameters. Rapeseed oil



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was used as a model substance for TAG. It has a high content of acyls, which possessunsaturated bonds.

Basic reactions leading to required products formation can be written down as follows [1]:

Decarboxylation:

CnH2n+1COOH CnH2n+2 + CO2 (1)

Decarbonylation:

CnH2n+1COOH + H2 CnH2n+2 + H2O + CO (2)

Reduction:

CnH2n+1COOH + 3H2 Cn+1H2n+4 + 2H2O (3)

Reaction products are gaseous hydrocarbons, mixture of liquid hydrocarbons with highern-alkanes predominating (C15-C18), organic compounds (in part solid) as intermediary

products of catalytic reactions (saturated TAG, fatty acids, alcohols, fatty acid esters) andreaction water. The gaseous phase contains CO2, CO, propane, methane, ethane and

propylene. Their mutual proportion depends on reaction conditions, raw material used and

partly also on the catalyst type.Fig. 2 shows the possible reaction mechanism [1]. Hydrogenation of double bonds in acyls

occurs at temperatures lower than those of HDC and HDO processes; reaction heat is releaseddepending on the raw material composition. The gas sample composition indicates thereaction course. In the first step, water is eliminated and monocarboxylic acids are formedwithout degradation of the long alkane chain. The next step involves HDC and/or HDO of thefatty acid accompanied by the formation of hydrocarbons. It is obvious that the formerreaction runs faster since along hydrocarbons free monocarboxylic acids C16 and C18 wereidentified in the liquid phase.

Figure 2 Flow-chart of processes of TAG conversion in the presence of hydrogen and NiMo/Al2O3catalyst

The HDC reaction is favored by lower partial pressures of hydrogen and by highertemperatures. HDC involves CO2 elimination and formation of n-alkane with an odd numberof carbon atoms (C17). Increasing the hydrogen partial pressure shifts reactions towardsreduction and HDC and/or HDO with formation of n-alkanes having an even number ofcarbon atoms (C18), and propane, water and CO as byproducts. In addition, methane andethane were observed in low concentrations. Methane is formed by a side equilibrium reaction

of hydrogen and CO. Cracking of alkanes thus formed occurs at higher temperatures,exceeding 380 C, and when stronger acidic catalytic centers are present.



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The ratio of n-alkanes with an odd number of carbon atoms to n-alkanes with an evennumber of carbon atoms can serve as an indicator for assessing the reaction course of HDCand HDO. This ratio has a marked effect on hydrogen consumption, and hence on thereactors caloric balance as well as on CO2, CH4, and CO content in the hydrogen gas; it alsoaffects the activity of the catalyst. In addition to principal reactions of HDC and HDO,competitive reactions of isomerization and alkylation of byproducts occur, too.

3.2 Effect of the feedstock type on catalytic hydroprocessing of TAG

In Tab. 7, the results of comparison of four different feedstocks with different TAGcomposition are presented. Stemming from the results it is obvious that the feedstockcomposition has a significant effect on n-alkanes distribution in the product. The portion ofiso-alkanes was negligible when using the investigated catalyst. Aromates concentration issimilar in all studied products and it lies below 2 % wt. level.

Table 7 Hydroconversion of various feedstocks

Type of TAG Rapeseed oil Palm oil Sunflower oil Lard


Temperature, oC 340 350 350 350Pressure, MPa 4.5 4.5 4.5 4.5LHSV, h-1 0.8 0.6 0.8 0.8

H2:TAG 500 250 500 250

Product Composition, % wt.:

< n-C14 0.46 2.62 3.71 1.4< iso-C14 0.03 0.33 0.27 -n-C15 2.00 15.46 3.40 5.65iso-C15 0.02 0.09 0.01 -n-C16 2.97 20.86 3.40 16.22iso-C16 0.04 0.09 0.04 -n-C17 35.26 23.97 35.34 16.57iso-C17 1.60 0.71 1.52 4*n-C18 47.98 30.40 41.91 43.67iso-C18 2.54 1.11 0.97 -> n-C18 3.44 1.52 1.55 2.78> iso-C18 1.89 1.08 0.64 -Aromatics 1.77 1.76 1.86 n.a.Polar substances 0.00 0 5.39 9.65*sum of all isoalkanes , n.a. not analyzed

3.3 Hydroconversion of TAG with atmospheric gas oil and effect of type of the catalyst

on catalytic transformation of TAG

Interesting results were achieved by testing the NiW/NaY catalyst with RO (Tab. 8). Thecatalyst was exceptionally active even at relatively low temperatures and low pressure. In the

parameter range analyzed, HDC was predominant; at 340 C a considerable quantity ofolefins C15-C18 was formed and saturated fatty acids were present among reaction products.The gaseous phase contained substantial portions of CO and propylene. It is obvious thatcatalyst supports containing a mixture of micro- and macropores can significantly affectreactions of hydrogenation transformation of TAG into hydrocarbons.



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Table 8 Hydroconversion of rapeseed oil on NiW/NaY catalyst

Temperature, C 320 340 360Pressure, MPa 3.5LHSV, h-1 1H2:TAG, Nm

3/m3h 1000Product: Composition, % wt.:

n-C15/n-C16 3.22 3.68 298n-C17/n-C18 4.12 4.16 4.81n-C17/(n-C17+n-C18) 0.81 0.83 0.83Aromatics 1.30 5.30 1.04Polar substances 5.02 0.54 0.31

HDS of petroleum fractions is a common technological operation in an oil refinery. Wehave verified experimentally the option of common desulphurization of distillate light gas oilin the mixture using a selected TAG. We were working with relatively low TAG contents inthe mixture to have approximately 5 % of biocomponents in the product. 6.5 % (V/V) of theselected TAG was mixed with unprocessed gas oil from petroleum distillation. The process

was tested using NiMo and NiW catalysts on various catalyst supports. The results arepresented in Tab. 9. Over all catalysts tested all the reactions occurred in parallel; what variedwere only mutual proportions of the reactions depending on the respective technologicalconditions and catalyst support properties.

Table 9 Hydroconversion of the blends AGO with RO, TO and T (6.5 % vol.) over different catalysts

catalyst -NiMo/Al2O3

NiMo/Al2O3

NiMo/Al2O3

NiMo/TiO2

NiW/NaY

NiW/TiO2

NiW/ZrO2

temperature, oC - 380 380 380 360 360 360 360pressure, MPa - 5.5 5.5 5.5 3.5 3.5 3.5 3.5LHSV, h-1 - 1 1 1 1 1 1 1H2:HC+TAG - 1000 1000 1000 1000 1000 1000 1000

feed AGO AGO+RO AGO+TO AGO+T AGO+RO AGO+RO AGO+RO AGO+RO

n-C17/n-C18 - 1.64 0.70 0.84 2.32 3.80 2.40 0.94CFPP, oC -3 -4 +5 -2 +2 -3 +2 +4Cetane number 53 57 56.4 56.8 55.4 55.7 55.2 56.7PAH, % wt. 6.9 3.4 4.1 3.5 4.8 4.3 4.9 5.2aromatics, %wt.

27.7

23.9 26.3 23.8 26.2 25.8 26.5 24.9

AGO- atmospheric gas oil, RO- rapeseed oil, TO crude tall oil, T- tallow

It was proved that TAG conversion in the presence of unprocessed gas oil has certaincharacteristic features:

- TAG conversion to hydrocarbons (reactions 1 and 2) consumes a large amount ofhydrogen, which in turn generates heat,- HDO reactions are fast, competing with sulfur elimination reactions from sulfur-containing

compounds,- the process must take place with hydrogen in high excess to eliminate the formation of

insoluble waxes, coke and polymeric deposits on the catalyst,- increasing temperature promotes the HDC reaction, giving rise to CO2; an important side

reaction is a reversible reaction of hydrogen with carbon dioxide giving rise to carbonmonoxide: CO2 + H2 CO + H2O,

- gas products also include methane formed by methanization from CO and hydrogen on themetallic component of the catalyst,

- CO2 and CO being formed have an inhibition effect on the HDS process,- gases formed in the reaction reduce the partial pressure of hydrogen, which is a limiting

factor especially when hydrogen pressure is low.



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The blend of AGO+TO shows low value of the ratio C17/C18 (0.70). That means thedecarboxylation occurs here in lower extent compared to that of RO. This can be caused bylower portion of unsaturated acyls of fatty acids in TO. Such conclusion is confirmed also bysimilar low ratio C17/C18 in the case of AGO+T (0.80). Rosin acids present in TO can showdifferent behavior from linear fatty acids during the hydroconversion.

HDO/HDC at temperatures higher than 360 C, LHSV 0,81 h -1, hydrogen pressure at

least 4.5 MPa and the ratio H2:TAG = 1000 and more was fully completed over all catalysts.Catalyst acidity had no significant effect on isomerization of n-alkanes being formed.Differences in CP and CFPP values were small. As the reaction gave rise to higher n-alkaneswith a higher melting point, it was helpful that gas oil worked as a solvent. Ni W-containingcatalysts exhibit an extraordinary hydrogenation activity and at lower reaction temperature(320340 C) wax like insoluble product were formed. In cases of catalyst supports with lowspecific surface (ZrO2), the level of desulphurization was much lower when compared to thecommercial catalyst. At temperatures 360380 C and with high hydrogen excess, a greaterquantity of reaction water was formed, pointing out to a more significant proportion of theHDO reaction.

3.4 The quality of products, performance and emission tests of diesel fuel withrenewable components from hydroprocessing

Hydroconversion of the blend AGO and TAG was proved by long-term experiment.Catalytic activity did not significantly change after two weeks of test duration. HDS and HDCreaction are competitive and so the desired desulphurization was not achieved. All other

parameters met the standard EN 590. Because of hydrogen excess in the reaction thehydrodearomatization of aromates and polyaromates occured. The result product showedincreased cetane number, which has positive effect on emissions, aromate content anddensity. This fact is very important for the refinery due to possibility to blend low-valuestream to diesel. Biocomponent content has no negative influence on de-emulsification properties

of DF and its corrosiveness. Oxidation stability was slightly lowered but the sample did not containantioxidants.Performance characteristics of blended fuel DF and 5 % HDO from RO were comparable

to those of neat DF. This is the result of presence similar components in both compared fuels.The results of emission characteristics of the DF containing 5 % HDO from RO in

comparison to DF are presented in Tab. 10. An addition of the second generation biocomponent toDF exhibits a significantly positive effect on all monitored emissions, those unregulated in

particular.

Table 10 Emission characteristics of tested fuels

FuelTesting

conditions

VOC

mg/kg

Corg.

mg.m

-3

NOx

mg/kg

Carbonyls

g/lidling 4.5 7.2 44.0 0.960 km.h-1 6.0 9.7 87.6 2.890 km.h-1 4.0 6.4 294.6 4.8

DF

120 km.h-1 14.0 22.5 476.2 0.2

idling 2.4 3.9 28.2 0.260 km.h-1 2.5 4.0 85.6 0.890 km.h-1 1.9 3.1 288.0 0.8

95 % DF+ 5 % HDOfrom RO

120 km.h-1 2.0 3.2 474.6 0.8DF diesel fuel, HDO from RO hydrodeoxygenate from rapeseed oil



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Hydrogen

Oil/fat

Solids

Hydrogen

ULSD

Atmospheric gas oil

- pretreatment, cleaning

- hydrotreatment- hydrodeoxygenation and decarboxylation- hydrodesulphurization- hydrodewaxing

- hydrodesulphurization of gas oil

4 Proposal of new technology for production diesel fuel with renewable components

A new concept of co-processing AGO and TAG will allow producing the diesel fuel withrenewable diesel share. Technology allows using non edible feedstock in the productiondiesel fuel that can meet EN 590 specification. Another advantage of this process isfulfillment of the governmental mandate on using bio-components in diesel pool.

The standard refinery distillate hydrotreating units do not appear to be suitable for

renewable diesel production in a co-processing scheme, but co-processing of biomass such asvegetable oils and/or animal fats may be processed in a revamp refinery distillatehydrotreating unit. Flow scheme is in Fig. 3, the proposal of common HDS of the AGO andTAG is in Fig. 4. The advantage of the technology is the opportunity to use cheaper feedstocklike TAG wastes. Another advantage of this process is fulfillment of the governmentalmandate on using bio-components in diesel pool. But technology must be carefully designedand the problems accompanied with materials, catalysts and heat of reaction must be solved.Vegetable oils/animal fats contain free fatty acids and the impact of their acidity to the reactorand pipes corrosion should be taken into account. Moreover, they contain traces of metals and

phosphorus acting as catalytic poisons cutting down the catalyst activity and lifetime.The water formed during HDO poses a further problem to the catalyst. Therefore, it is

advantageous to perform the reaction in a separate reactor connected in line with the mainhydrorefining reactor. The issue of the catalyst choking up with metals and phosphorus can besolved using a catalytic bed filled with a cheaper catalyst trapping the mentioned adversesubstances prior to the main catalyst.

The concept as designed will enable the use of the refinerys infrastructure. A key factor tosuccess is selecting an appropriate combination of catalysts to ensure gas oil HDS at therequested sulphur level below 10 mg/kg. The catalyst must be powerful enough to allowtransforming TAG to hydrocarbons. Because of a need for high hydrogen excess and greatformation of heat, it is necessary to resolve heat transfer in the process. Also important isremoval of CO2, CO, and CH4 from the hydrogen recycle. CO2 can be removed by amine

washing or by using the PSA system, if installed in the refinery. CO can be eliminated in thePSA system separately, or following catalytic methanization. The optimum solution will bebased on the specific situation prevailing in the refinery.

The technology represents green technology which is able to produce diesel fuel of secondgeneration from non-edible sources.

Figure 3 Renewable diesel production co-processing of biofeed in hydrodesulphurization unit



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Figure 4 Flow scheme proposal for co-processing hydrodesulphurization of atmospheric gas oil withhydrodeoxygetion and hydrodecaroxylation of renewable biocomponent

5 Conclusions

TAG can be converted to the second generation biocomponents in mixtures withatmospheric gas oil from crude oil distillation using a hydrorefining catalyst. Adding 6.5 %(vol.) of vegetable oil, gas oil containing 55.5 % of biocomponent was prepared,characterized with performance and emission parameters similar to fossil diesel. The

philosophy of introduction of a second reactor into the existing structure of hydrorefining unitallows reducing investment cost of biocomponent processing. The desulphurization of

atmospheric gas oil is slower than n-alkane production from TAG over typicalhydrodesulphurization catalyst. Key factor of successful hydrodesulphurization andhydrodeoxygenation/hydrodecarboxylation is in appropriate selection of the catalyst andtechnological condition. The selectivity to hydrodeoxygenation/hydrodecarboxylation

products increases with increasing temperature.

Acknowledgement

The authors thank Pavol Kuna (Slovnaft VRUP, Bratislava) for performing catalytictests, assoc. prof. Pavol Hudec, PhD. (STU, Bratislava) for performing catalyst parameters.

This work was supported by the Slovak Research and Development Agency under thecontract No. APVV-20-037105.

Nomenclature:

AGO atmospheric gas oil, CFPP cold filter plugging point, CP cloud point, DF dieselfuel, HDC hydrodecarboxylation, HDO hydrodeoxygenation, HDS hydrodesuplhurization, LHSV liquid hourly space velocity, PAH polyaromatichydrocarbons, PSA pressure swing adsoprtion, RO rapeseed oil, T tallow, TAG triacylglycerols, TO tall oil, ULSD ultra low sulphur diesel, VOC volatile organiccompounds

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AGO

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COPSA

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RENEWABLE DIESELHYDROGEN MAKE-UP

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AMINEABSORBER



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