catalytic cracking of vegetable oil and animal fat in...

Catalytic cracking of vegetable oil and animal

fat in presence of zeolite catalysts

Tests and documentation done in the framework of the cross border project ESPAN by

Eduard Buzetzki, Katarína Sidorová, Zuzana Cvengrošová, Ján Cvengroš

Faculty of chemical and food technology STU, Radlinského 9, 812 37 Bratislava

e-mail: [email protected]

7.10.2010

Bratislava

http://www.chtf.stuba.sk/kot/people2.php?idses=400143

mailto:[email protected]

Contens

Introduction 3

Processes and equipment 6

Materials 8

Procedures 9

Results and discussion 10

Influence of the catalyst type on the cracking process 10

Acid value 13

Influence of catalyst portion on the cracking process 14

Influence of the oil/fat type on the cracking process 15

GLC analysis of cracking condensates 18

Separated condensate removal during the cracking process 23

Utilization of condensates obtained by TAG cracking 25

Hydrodeoxygenation of treated products from cracking of TAG 26

Blends of treated condensates with fossil diesel 27

Co-cracking 29

Conclusion 31

References 32

Introduction

Present-day society is largely dependent on piston internal combustion engines powering

transport vehicles. Currently, as much as 98% of transportation fuels in Europe are of fossil

origin [1]. It is reasonable to assume that in the foreseeable future spark- and compression-

ignition engines powered by liquid fuels will continue to be dominant as driving units,

considering their high efficiency, reliability, economy of use and sophisticated design. In

view of limited oil resources and environmental pollution, fossil fuel replacement by

renewable energy sources is an urgent problem. Diminishing fossil fuel reserves quite

naturally draw attention to a reliable and accessible energy source – biomass. Materials

containing natural triacylglycerols (TAG) can be utilized, either directly or after being

subjected to a suitable transformation process, as liquid transportation fuels. Development of

transportation fossil fuels from renewable TAG containing sources at sustainable cost is

therefore fully justified. Despite various restrictions concerning their use as foodstuffs,

vegetable oils and animal fats continue to be an important commodity for liquid fuel

production, particularly when it comes to inedible or waste articles. Second-generation fuels

manufactured from lignocellulosic biomass that do not compete with food production have a

more favorable carbon balance, lower energy demand and higher production potential. But

these biofuels will be put into commercial application and able to affect the transportation

sector within the timeframe of five to ten years.

Thermal cracking of TAG in the presence of catalysts constitutes an alternative way for

liquid fuel production from renewable sources. When compared to TAG-to-FAME

transesterification, thermal cracking has a number of benefits, such as lower operating cost,

simpler technology and high tolerance to feedstock TAG quality. Comprehensive review on

possible catalysts was published in [2]. Review papers [3-6] related to pyrolysis and TAG

cracking producing fuels yield extensive information on this matter. According to cited

literature, application of zeolite catalysts is oriented mostly to the production of structures

typical for fuels designated for petrol engines.

Zeolites are crystalline aluminum silicates with three-dimensional network structure. The

main structural units are tetrahedrons [SiO4]-4

and [AlO4]-5

, where silicon and aluminum

atoms are positioned in the centre, and bigger atoms are placed in the corners of tetrahedrons.

Tetrahedrons are joined together through oxygen atoms shared by two neighbouring

tetrahedrons. Negative charge of the lattice is neutralized by positive charges of metal cations.

Localized regions with high intensity of electrostatic field in a neighbourhood of the present

cations

represent highly reactive centres. Zeolite catalysts exhibit high

porosity and size selectivity. In the course of a catalysed reaction either the molecules of

particular size are favoured, or by changing the size of pores in zeolite, specific reaction

products can be obtained. Size of pores can be changed by targeted intervention to the zeolite

structure with respect to product requirements. Basic characteristics of same types of

synthetic and natural zeolites are shown in Tab. 1.

Tab. 1 Characteristics of same types of synthetic and natural zeolites

Type Pore opening [nm]

Synthetic zeolites

Zeolite A 0,41

ZSM 5 0,51 – 0,56

Zeolite X and Y 0,74 – 0,94

Natural zeolites

Analcime 0,26

Heulandite 0,39 – 0,54

Clinoptilolite 0,47

Faujasite 0,74

Zeolites X and Y. The basic structure unit of zeolite of an A, X, Y type is truncated

cubic octahedrons formed from 24 elemental tetrahedrons [SiO4] [AlO4]. Mutual ratio of

tetrahedrons and crystallographic structure characterize the zeolite type. The way of bonding

determines the crystallographic structure and is characteristic for the zeolites of the A or X

and Y type. The zeolites of the X and Y type in sodium and calcium modification have the

effective pore diameter in the range of 8 – 12.10-10

m, and are considered as broad porosity

zeolites. Sodalite cell (β-cell) of NaX and NaY zeolite has the diameter of 6.6 Å. Bonding of

tetrahedrons of each sodalite cell with four adjacent cells is through six circles. Bigger cells of

higher order ( -cells) are formed with 10 sodalite cells. Inner diameter of -cell is 12.5 Å and

its entrance window has diameter of 7 Å. Ratio Si:Al is 2:1 in NaY, 1.2:1 in NaX. One of the

main parts by cracking with NaY are C10 compounds and nearly no aromatic products.

The zeolite ZSM-5 is alumino-silcate with high content of Si and low content of Al.

Centres in the Al surroundings are highly acidic. Replacement of Al+3

by Si+4

requires the

presence of additional positive charge. If H+ is present, acidity of the zeolite is high. ZSM-5 is

highly porous material with two-dimensional pore structure. It has two types of pores formed

by 10-unit oxygen circles. The first type is a straight pore with elliptic cross section

5.1 x 5.6 Å. The second type of pores intersect straight pores under

right angle in zigzag arrangement, and have circular cross section 5.4 x 5.6 Å. 10-unit circles

are of profound importance for the formation of products characteristic for petrol. Zeolites

with 8-unit oxygen circles cannot produce C6 molecules and higher, because the molecules of

this size do not fit to small pores of the zeolite. Large pores of the zeolites with 12-unit

oxygen circles enable production of increased amount of C11 and C12 compounds,

characteristic for petrol. During the catalytic cracking of TAG the synthetic zeolite catalysts

ZSM-5 and especially HZSM-5 are able to convert TAG to aromatic products with high

octane number [7]. HZSM-5 catalyst is shape-selective catalyst and its pores with intersecting

channels are ideal for producing aromatic compounds. Light olefins, C2-C4, readily

oligomerize, cyclize, and aromatise inside the catalyst pores and form the aromatic

compounds. The newly form aromatic compounds can then either diffuse from the catalyst or

remain inside the pores and forming coke [8].

The structure of clinoptilolite is sheet-like. Although still a true tectosilicate where every

oxygen is connected to either a silicon or an aluminum ion (at a ratio of [Al + Si]/O = 1/2),

there still is a sheet-like structural organization. The sheets are connected to each other by a

few bonds that are relatively widely separated from each other. The sheets contain open rings

of alternating eight and ten sides. These rings stack together from sheet to sheet to form

channels throughout the crystal structure. The size of these channels is 4,7 Å.

Clinoptilolite is not the most well known, but is one of the more useful natural zeolites.

Clinoptilolite is used in many applications such as a chemical sieve, a gas absorber, a feed

additive, a food additive, an odor control agent and as a water filter for municipal and

residential drinking water and aquariums. Clinoptilolite is well suited for these applications

due to its large amount of pore space, high resistance to extreme temperatures and chemically

neutral basic structure. What might strike many as odd are the food and feed additives.

Clinoptilolite has been used for several years now as an additive to feed for cows, pigs, horses

and chickens. It absorbs toxins in the feed that are created by moulds and microscopic

parasites and has enhanced food absorption by these animals. A similar use in actual people

food is being tested. Clinoptilolite can easily absorb ammonia and other toxic gases from air

and water and thus can be used in filters, both for health reasons and for odor removal [9 –

10].

The literature references, which provide information on the use of clinoptilolite catalysts

in cracking of vegetable oils for production of fuels of diesel type, are scarce.

The structure of common molecule of TAG is as follows

In the TAG molecule three acyls are present. These acyls can be saturated (for example

stearic acid C18:0) or unsaturated (in oleic acid C18:1 cis-9, in linoleic acid C18:2 cis-9, cis-

12 and in linolenic acid C18:3 cis-9, cis-12, cis-15). Usual position of cracking besides ester

bonds is located on the double bonds. This situation shows what compounds can be find in the

cracking product.

If the cracking happens on glycerol, we can consider it as reactant selectivity. In this case

the pore opening plays a very important role. Especially in the presence of unsaturated fatty

acids, since they have a 30 ° knuckle on each double bond C = C. That means, in a small but

still applicable pore opening the fatty acid can only penetrate till the knuckle (C = C double

bond) in the zeolite and will crack.

The remaining rest on glycerol, now straight, must be cracked again on the glycerol. This

also means a longer cracking time. In both cases is this reactant selectivity. This process

builds smaller hydrocarbon chains.

In the case of too small or too large pore openings, no catalytic cracking occurs, of course

the fatty acids can not penetrate in the zeolite to acid centre or simply slip through without

reaction (without cracking on acid centre). It is usually only a thermal cracking (thermal

swinging of molecules) which only at high temperatures is going on.

If the pore opening is selected so that the fatty acid partially or completely can going

through, the cracking happens on glycerol. That means the chain lengths do not change. With

such a catalyst it can be obtained longer hydrocarbon chains.

Every zeolite has characteristic pores and channels, together with the possibilities of

surface modification the zeolites become an excellent heterogeneous catalyst. Fig. 1 shows

the cracking occurs at the acidic centres in the inner part of the channels.

Fig. 1 Scheme of cracking at the acidic centres in the inner part of the channels

Processes and equipment

In our works we examined vegetable oil and fat cracking in the presence of selected

catalysts. At temperatures of 350 – 440 °C and at atmospheric pressure, the most effective

catalysts in terms of liquid fraction yield obtained during 20 – 30 minutes proved to be the

synthetic zeolite or natural zeolite. The balance is created by weighing the liquid fraction and

cracking residuum after catalyst removal. The cracking residuum is a viscous liquid or

bitumen. For the balance, the gaseous products and losses are calculated. Gaseous products

are not collected or, in selected tests, they are gathered in plastic bags and analyzed.

heat

Catalyst

Plant oil / fat

Produkt

Condensation H2O

gass

T2 °C

T1 °C

Fig. 2 left: Scheme of stainless-steel batch reactor, right: Photo cracking device

The liquid fraction represents 85 to 90 % of the weight of the input oil. It is usually a light

brown hazy liquid with sharp smell, which after short period of time spontaneously separates

into two liquid phases. Bottom polar phase represents approximately 1 to 3 % of input and

consists of water and short C1 and C2 acids. The upper less polar phase is treated by

Cracking

e.g. on a

double bond

reactant

selectivity

form

selectivity

product

selectivity

Use

as

molecular

sieve

Use

as

synthesis

catalyst

0

100

200

300

400

500

0 10 20 30 40 50 60 70

time (min)

tem

per

atu

re (

°C)

T1

T2

Fig. 3 Typical temperature regime during cracking

distillation at temperatures up to 170 - 180 C, which corresponds to

the flash point of the treated condensate above 60 C. The light (petrol) fraction represents

usually 3 to 9 wt. % of the input oil. The treated condensate as a distillation residue is usually

clear, with mild odor. In specific cases a sediment of paraffins and oxygenates soluble at

temperatures over 40 C is formed. The treated condensate is evaluated through its balance,

and its GLC, viscosity, density and acid value (AV) are determined.

According the variety of programs and raw materials a lot of cracking devices exists. In

our laboratory study we used batch arrangement. During our experiments was carried out in a

two-neck flask or steel reactor without mechanical mixing. Bubbles of formed gases and

vapours ensured mixing. A thermocouple thermometer was inserted through the side neck.

The formed volatile products were transported through the central neck to a downward

condenser cooled with water. The temperature of vapours at the entrance of the condenser was

measured by mercury thermometer. Heating of the reaction flask and reactor was either

indirect electrical, or direct with the natural gas flame from rose-shaped burner. The

equipment was thermally insulated.

During the measurement the oil was weighted, the weighted catalyst was added, the

equipment was closed and

heated with required heating

regime to desired temperature.

At the second part of our study

a stainless-steel reactor was

installed instead of glass

reactor. This arrangement was

more effective, reliable and

comfortable. This change has

practically no influence to the

cracking process and its yield. The reactor is equipped with two thermocouples with on-line

registration of temperature profiles using Testotherm four-channel device. The scheme of the

apparatus is shown in Fig. 2. In Fig. 3 the typical temperature regime during cracking is

demonstrated.

The aim of the this work is to present results from cracking of natural TAG in presence

of zeolite catalysts, the yield of liquid fraction, its composition, some selected properties, and

utilization as an alternative fuel in the blend with fossil diesel fuel.

Materials

The following oils and fats were used for the measurements of TAG catalytic cracking:

- cold-pressed and filtered non-erucic rapeseed oil (Ecofil Michalovce, SR),

- refined sunflower oil (Palma Tumys Bratislava, SR),

- food-grade lard (JAV-AKC Vlčany, SR),

- filtered jatropha oil (Africa, 2008),

- refined soybean oil (Spain) and

- filtered used frying oils UFO 1 and UFO 2 (INTA Trenčín, Slovak Republic) acquired

through collection of used frying oils from large-scale producers, UFO 3 from

collection organized in Austrian households.

Acyl profiles of used oils and fats are shown in Table 2.

Tab. 2 Acyl profile of input oils/fats into the cracking process

C14 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20 C22

UFO 1

AV = 1.8 mg KOH/g 0.5 9.5 0.3 3.4 49.9 28.8 4.2 1.8 0.9

UFO 2

AV = 7.0 mg KOH/g - 5.6 - 3.3 60.8 27.3 2.1 0.4 0.5

UFO 3

AV = 0.7 mg KOH/g

0.6 6.7 0.3 2.7 52.6 29.2 6.1 0.8 0.3

Rapeseed oil

AV = 1.7 mg KOH/g

- 5.1 - 1.2 63.6 20.3 9.3 0.5 -

Sunflower oil

AV = 0.4 mg KOH/g

- 7.1 - 4.2 25.4 63.2 - - -

Jatropha oil

AV = 31.5 mg KOH/g

- 14.5 1.2 5.6 38.1 39,9 0.7 - -

Soybean oil

AV = 2.9 mg KOH/g

- 11.4 - 3.6 25.9 51.8 7.2 - -

Lard

AV = 1.0 mg KOH/g

1.1 37.9 0.2 4.6 40.2 14.1 0.3 0.4 0.1

The following catalysts were used: Synthetic zeolite NaY (Slovnaft VURUP, Bratislava,

Slovak Republic) with the parameters: specific surface area SBET = 506 m2/g, micro pore

volume Vmicro = 0.246 cm3/g, specific area St = 36.3 m

2/g, total pore volume Va = 0.341 cm

3/g,

acidity 0.36 mmol NH3/g was used in the form of extruded cylinders with diameter of ca 1

mm. Natural non-activated zeolite clinoptilotite (CL) (Zeocem, Bystre, Slovak Republic) with

SBET = 26.0 m2/g, Vmicro = 0.004 cm

3/g, St = 18.9 m

2/g, total pore volume Va = 0.105 cm

3/g,

acidity 0.45 mmol NH3/g was used in the form of grains with the size up to 3 mm. Activated

zeolite clinoptilotite K-025-6 with SBET = 221 m2/g was also used in the form of grains with

the size of 3 – 5 mm. Zeolites HY and NH4Y (Slovnaft VURUP, Bratislava) were used in the

form

of extruded cylinders with the diameter of ca 1 mm. Activated forms

of the zeolite ZSM5, i.e. Na-ZSM5, H-ZSM5 (Slovnaft VURUP, Bratislava) were used in the

form of extruded cylinders with the diameter of ca 0.5 mm. Bentonite P-140 (Envigeo,

Banska Bystrica, Slovak Republic) was used in powder form. Activated carbon Norit Gac

1240 (Norit Nederland B.V.) was used in powder form. Alumina γ-Al2O3 (Lachema Brno,

Czech Republic) was processed before the use by annealing at 1000 C, 5 h, while its acidity

was close to 0 mmol NH3/g.

Procedures

Analytical GLC chromatography with the apparatus Chrompack CP 9000 with packed

glass column with 10 % SE 30 on Chromatone NAW-DMCS 1.8 m x 3 mm, equipped with

FID, or on the apparatus HP 5890 Serie II with FID and a capillary column HP-1 (5 m x 0.53

mm x 2.65 μm) was used for analytical evaluation of treated liquid condensates.

GS/MS analyses were performed on the apparatus GCMS-QP 5000 by Shimadzu.

Ionization was carried out by electrons at the acceleration potential of 1.5 kV. The

temperature of the connecting block was 250 °C. A capillary column HP-1 with the length of

50 m was used. For the first four minutes the temperature regime of the column was

isothermal at 60 °C, then the temperature increased with the gradient of 10 °C.min-1

up to 240

°C. Helium with the flow rate 0.5 ml.min-1

was used as the carrier gas. 1 μl of the diluted

sample solution was injected in methanol.

In a parallel determination of the liquid condensate composition by GLS chromatography

on the filling column and by GC/MS chromatography on the capillary column with the same

stationary phase in both cases (silicon elastomer SE 30), the order of peaks is preserved; only

retention times (RT) change. This enables identification of major peaks also in the GLC

chromatogram obtained from the packed column. These peaks were additionally verified

using a supplementary chromatograph of n-alkane standards (C10 to C24). Thus the GLC

chromatograph from the filling column provides relevant information for the evaluation of

cracking products.

1H NMR spectral studies were obtained with the apparatus VARIAN VXR 600 in the

presence of deuterated chloroform as a solvent.

Other determinations of respective parameters were carried out by standardized

procedures.

Results and discussion

Influence of the catalyst type on the cracking process

Table 3 summarizes the yields of fractions from cracking of rapeseed oil by selected tests

in presence of various catalysts, together with reaction time and AV, density and viscosity of

the liquid condensate.

Tab. 3 Influence of catalyst type on rapeseed oil cracking process

Test

No.

Catalyst,

10 wt.% of oil

τ,

min

Yield, wt. % ρ (15 °C),

kg m-3

ν (40 °C),

mm2s

-1

AV,

mgKOH/g Liquid

condensate

Bitumen Gas

1. without catalyst 25 63 10 27 n.a. n.a. 123

2. actvated carbon 50 80 n.a. n.a. 874.7 6.723 129

3. γ-Al2O3 25 27 16 57 n.a. n.a. n.a.

4. γ-Al2O3 activated 25 48 11 41 n.a. n.a. n.a.

5. NaY 20 85 6 9 n.a. n.a. 98

6. NaY 21 87 4 9 n.a. n.a. 117

7. NaY 90 85 11 4 877.9 8.311 118

8. NaY 60 88 10 2 885.6 8.588 122

9. HY 30 88 n.a. n.a. 894.5 12.860 112

10. HY 23 86 8 6 n.a. n.a. 77

11. NH4Y 78 86 12 2 878.5 5.573 114

12. Na-ZSM5 40 83 5 12 n.a. n.a. 98

13. Na-ZSM5 95 64 32 4 883.9 9.074 141

14. H-ZSM5 78 77 20 3 883.5 8.587 133

15. bentonite 60 86 8 6 885.5 8.684 125

16. CL activated 37 82 3 15 n.a. n.a. 128

17. CL 25 90 4 6 n.a. n.a. 118

18. CL 21 89 4 7 n.a. n.a. 99

n.a. – not available

The basis for material balance in Table 3 is input oil and the liquid condensate without

any treatment. The amount of catalysts in these tests was 10 wt. % with respect to oil amount.

High yield of liquid condensate at low amount of gaseous and residual fractions achieved in

the shortest possible time is considered as an effective result. From this point of view,

according to data in Table 3 the effective catalysts are NaY, HY, and CL. In their presence, at

the defined temperature regime and after a relatively short time period of 20 to 30 minutes, a

condensate with high yield between 85 and 90 % was obtained. High yields of liquid

condensate were obtained also with NH4Y, H-ZSM5, and also with the catalysts of non-

zeolitic type, e.g. activated carbon and bentonite but only after significantly longer time

period.

The reason for testing of bentonite is its utilization as a bonding

component in the synthetic zeolite production. Even if it provides relatively high yield of the

liquid condensate, this requires relatively long reaction time. On the other hand, the tests with

alumina with and without active acid centers were expected to show the role of active centers

and channels in catalysis process. Based on our obtained results, the presence of active centers

at the catalysts’ surface significantly influences their effect. In the tested temperature interval,

the cracking without added catalyst results in technologically uninteresting process with low

yield of the liquid condensate. In contrary, the yield of gaseous products is high. In the case of

highly active catalyst NaY the attempt to increase the yield of liquid condensate by extension

of the reaction time was not successful. The bitumen and gaseous fractions during tests with

zeolite catalysts were relatively same without significant deviations. The group of ZSM5

catalysts exhibits, except of longer reaction time, also increased portion of cracking residuum.

AV of condensates is high, between 100 and 140 mg KOH/g, while the highest values are

observed in the ZSM5 group. The price of NaY is 2.50 €/kg, the price of CL is 0.13 €/kg.

As shown in Table 3, the values of densities and viscosities in cracking products are higher

than allowed by standard EN 590 for diesel fuel – the viscosity (40 °C) 2.9 to 4.5 mm2s

-1 and

density (15 °C) 820 to 845 kg.m-3

. This can be related to presence of oxygenates in cracking

products. During hydrogenation of analogous materials the densities at the bottom end of the

standard values were achieved. The solution for utilization of cracking products with higher

densities and higher viscosities as fuels will be most likely their blending with fossil diesel

fuel with suitable viscosity and density parameters of the blends.

Table 4 shows the composition of gaseous fractions from two selected cracking tests in

presence of NaY and HY catalysts, respectively. The gaseous mixtures recovered during

cracking contain mainly CO, CO2, along with small amounts of methane, ethane, ethylene,

and propylene. Hydrogen is not present in these mixtures.

Tab. 4 Composition of gases formed by rapeseed oil cracking during the tests

No.5 (NaY) and No. 7 (HY)

Test No. 5 No. 7 Test No. 5 No. 7

Composition vol.% vol.% Composition vol.% vol.%

etane 5.80 3.54 1-buthene 1.14 0.84

CO2 36.90 30.65 trans-2-buthene 0.26 0.80

methane 7.04 3.07 iso-buthene 0.20 0.97

ethylene 3.19 5.14 1,3-buthadiene 0.16 0.00

CO 35.82 36.59 cis-2-buthene 0.23 0.72

propane 2.77 2.91 2-metylbuthane 0.03 0.29

propylene 3.59 10.27 n-pentane 0.42 0.38

2-methylpropane 0.07 0.67 HC more than n-C5 1.04 1.85

n-buthane 1.34 1.31

Table 5 shows results obtained during the repeated use of the same catalyst (catalyst

recycling). Rapeseed oil was cracked in presence of CL with the share of 10 wt. %, while in

the next experiment the catalyst from previous experiment was used without any treatment or

rinsing. After 4 cycles, a slight decrease of the activity of CL was registered, expressed in

decreased yield of liquid condensate and increase of gaseous fraction.

Tab. 5 Influence of repeated CL use during rapeseed oil cracking

Test

No.

τ, min Yield, wt.% AV,

mg KOH/g Liquid condensate Bitumen Gas Polar fraction Light fraction

17. 25 81.7 4.2 5.7 2.1 6.3 119

19. 26 80.8 4.1 5.4 1.3 8.4 122

20. 25 76.6 4.3 11.6 0.4 7.1 118

21. 25 74.9 4.2 10.8

2.8 7.3 118

The material balance concerns the already treated liquid condensate. Identical experiment was

carried out also for NaY, and similar results were obtained. No changes in GLC

chromatograms during repeated catalyst use were recorded.

Acid value

The acid value of the cracking condensate is relatively high, ranges regularly around 100

mg KOH/g and corresponds to literature data. The acid value of bottom polar phase in

cracking condensate is lower with a value of 70 to 75 mg KOH/g than the AV of less polar

layer.

The regime of cracking with two catalysts – with primary catalyst in the liquid phase and

with secondary catalyst in vapor phase – is interesting from several points of view. In this

way additional cleavage of the product can be achieved, which could not be completed in the

primary stage in liquid phase, with further processes such as decarboxylation, deacidification,

isomeration, etc. The primary and secondary catalysts can be identical, or different. Table 6

shows the results of cracking with using a couple of catalysts, compared to results of tests in

the presence of only the primary catalyst. The adjustment of experimental arrangement during

these tests required only the inclusion of a sieve cylinder filled with the secondary catalyst in

the way of vapors coming from the space of the primary catalyst. No additional heating of the

secondary catalyst space was applied. Apart from rapeseed oil also other oils and fats

(sunflower oil, lard) were used in these tests.

A couple of identical catalysts do not lead to any significant changes in composition of

liquid condensate. Moreover, it results in decrease of the liquid condensate yield and has most

likely no practical use. This was confirmed by the results of the couple CL-CL (No. 26), but

also NaY-NaY (No. 22), where at best slight decrease of the AV was observed, more

pronounced in case of lard (No. 23) from the original value 117 mg KOH/g to 86 mg KOH/g

in the two-stage arrangement.

A couple of different catalysts have more pronounced effect. While single CL in the

standard process yields a liquid condensate with AV 99 mg KOH/g, CL with MgSiO3

produces a condensate with the AV 35 mg KOH/g, accompanied by the decrease of the yield

of treated condensate from 83 wt. % to 64 wt. % and the increase of the yield of the polar

phase to 19 wt. % from the original 3 wt. %.

The combination of NaY and HZSM-5 with sunflower oil and also CL with HZSM-5

with rapeseed oil led to slight decrease of AV in comparison with using primary catalysts

alone. However, at the same time the yield was significantly decreased from original ca. 80 %

to the level of about 50 % at simultaneous increase of polar fraction and gaseous fraction as

well. No changes in composition of treated condensates from these tests were detected on

basis of GLC chromatograms.

A decrease of AV, which is nevertheless always accompanied

by decrease of the yield of liquid condensate, is a common sign by using of a couple of

catalysts in tested systems. Lima et al. [3] also concludes that combination of pyrolytic and

catalytic cracking with the use of zeolite type catalyst HZSM-5 at 400 °C results in partial

deoxygenation of the product, but she does not quantify the results.

Tab. 6 Properties of condensates obtained by two-step cracking process

Test

No.

Cracking process τ, min Yield, wt. % AV,

mgKOH/g Liquid

condensate

Bitumen Gas

5. Rapeseed oil + NaY (prim.) 20 85 5.5 9.5 98

22. Rapeseed oil + NaY (prim.) + NaY (sec.) 24 84 10.7 5.3 107

23. Lard + NaY (prim.) + NaY (sec.) 21 88 5 7 86

24. Sunflower oil + NaY (prim.) 28 90 3.5 6.5 102

14. Rapeseed oil + HZSM-5 (prim.) 78 77 20 3 133

25. Sunflower oil + NaY (prim.) + HZSM-5 (sec.) 22 50 12 38 n.a.

26. Rapeseed oil + CL (prim.) + HZSM-5 in (sec.) 39 76 7 17 89

18. Rapeseed oil + CL (prim.) 21 89 4 7 99

27. Rapeseed oil + CL (prim.) + CL (sec.) 17 87 4 9 110

33. UFO + CL (prim.) + MgSiO3 (sec.) 39 87 7 6 35

n.a. – not available, prim. – primary catalyst, sec. – secundary catalyst

Influence of catalyst portion on the cracking process

Selected test results which demonstrate the influence of catalyst portion on the process are

shown in the Tab. 7. Rapeseed oil was used with catalysts NaY, H-ZSM5 and Na-ZSM5 in

the tests. As expected, the portion of catalyst significantly influences the cracking condensate

yields in used temperature regime. At low catalyst portions the yield of liquid condensate is

naturally lower. However, also under these conditions higher yield of the liquid condensate

can be achieved after significant extension of reaction time. The GLC chromatograms from

the processes with low catalyst portion are similar to those with high catalyst portion. This

applies for all three tested catalysts. Lower yield of the liquid condensate was achieved in the

ZSM5 group. At the applied temperature and time regimes, the process without any catalyst

provides lower yield of liquid condensate and increased yields of bitumen and gases.

Tab. 7 Influence of catalyst portion on the cracking process

Test

No.

Catalyst portion τ, min Yield, wt.% AV, mg KOH/g

Liquid condensate Bitumen Gas

1. without catalyst 25 63 10 27 123

28. NaY (1%) 130 84 9 7 119

29 NaY(10%) 28 89 5 6 118

30. NaY(5%) 60 84 n.a. n.a. 110

7. NaY (10%) 90 85 11 4 n.a.

31. H-ZSM5 (5%) 105 78 n.a. n.a. 123

14. H-ZSM5 (10%) 78 77 20 3 133

32. Na-ZSM5 (5%) 105 76 n.a. n.a. 128

13. Na-ZSM5(10%) 95 64 32 4 141

n.a. – not available

Influence of the oil/fat type on the cracking process

Several types of well-defined oils/fats as well as undefined used frying oils from collection

were used for the measurements. Characterization of the oils tested including their acyl

profiles is shown in Table 1. As there are some differences in these characteristics concerning

shares of saturated and unsaturated acyls as well as shares of C16 and C18 chains, the

measurements set out to determine whether such differences would be manifested in the

cracking process in the presence of the three catalysts used, particularly as regards the liquid

fraction yield and acidity. The results obtained through standard-procedure cracking (catalyst

10 % by weight, no mixing, reaction time equivalent to the temperature range of 350 - 440

°C) are presented in Table 8. The liquid condensate yield is expressed as relative to the

untreated material while the remaining parameters (AV, viscosity, density and GLC) apply to

the treated liquid condensate with separated aqueous layer and evaporated light fraction.

In cracking carried out with the catalysts tested, the results show that the oil type affects

the liquid condensate, bitumen and gas product yields, and the AV only to a small extent. In

the case of NaY and CL catalysts, the liquid condensate yields range between 85 and 90 % for

all oils tested; a slightly lower yield was found only for lard. Likewise, no significant

difference in GLC chromatographs of treated condensates and in the yields of gaseous and

bitumen fractions were observed that could be linked to the feedstock oil type and acyl

profile. For example, rapeseed oil with a high C18:1 content (63.6%) and a lower C18:2

content (20.2%) and sunflower oil with approximately reversed percentages of the above-

mentioned acyls provide just about the same yields of outputs and nearly identical AV of their

liquid

condensates with both catalysts, NaY as well as CL, while having

identical chromatographs of the condensates.

Tab. 8 Influence of oil / fat type on cracking process

Test

No.

Catalyst τ,

min

Yield, wt.% AV,

mg KOH/g ρ (15 °C),

kg m-3

ν (40 °C),

mm2s

-1

Liquid

condensate

Bitumen Gas

Rapeseed oil, AV = 1.7 mg KOH/g 34 NaY 28 89 5 6 118 - - 35 NaY 21 87 4 9 117 - - 36 NaY 20 85 6 9 98 874 7.259 37 CL 25 90 4 6 119 - - 38 CL 21 89 4 7 99 875 7.598 39 HZSM-5 31 75 7 18 99 876 6.647

Sunflower oil, AV = 0.4 mg KOH/g 40 NaY 28 90 3 7 102 - - 41 NaY 65 85 8 7 113 - - 42 CL 30 86 6 8 94 869 6.118 43 HZSM-5 43 77 14 9 118 883 6.805

UFO 1, AV = 1.8 mg KOH/g 44 NaY 23 87 6 7 109 880 7.705

45 NaY 23 91 4 5 115 882 8.982

46 NaY 23 93 3 4 115 881 8.802

47 NaY 23 87 6 7 75 877 6.627

48 CL 25 88 5 7 116 882 9.202

49 CL 24 87 6 7 88 875 6.706

50 CL 24 87 7 6 74 866 4.451

51 CL 24 88 7 6 89 873 5.968

52 CL 24 88 7 6 83 867 5.090

53 CL 39 87 4 9 95 872 6.786

54 CL 27 90 3 7 92 879 8.184

55 HZSM-5 24 85 7 8 113 880 9.281

UFO 2, AV = 7 mg KOH/g 56 CL 20 89 5 6 110 878 7.465

UFO 3, AV = 0.7 mg KOH/g 57 CL 25 90 5 5 78 867 4.860

Jatropha, AV = 31.5 mg KOH/g 58 NaY 31 90 5 5 110 871 6.168 59 CL 31 88 6 6 85 868 5.555

Soybean oil, AV = 2.9 mg KOH/g 60 NaY 31 88 6 6 98 872 5.522 61 CL 19 89 6 5 110 871 6.357

Lard, AV = 1.0 mg KOH/g 62 NaY 44 82 7 11 117 semisolid -

Except for two instances, the AV of treated condensates is in the range of 85 – 118 mg

KOH/g for all oils tested. No correlation between a high AV of feedstock oil and the AV of

treated condensate was found. While the acidic jatropha oil yielded a liquid condensate with a

low AV of 85 mg KOH/g, the non-acidic sunflower oil (AV 0.4 mg KOH/g), on the other

hand, provided a condensate with an AV of 94 mg KOH/g with the same catalyst CL. A

certain trend can be observed here: raised viscosity values and especially raised densities of

treated condensates give rise to increased AV.

Similar results were found with the catalyst HZSM-5, only the liquid condensate yield was

lower – 75 to 85 % wt. When compared to densities of other condensates, densities of

condensates obtained via HZSM-5 are usually higher irrespective of the feedstock oil type.

Such condensates have a higher AV too. Viscosities of condensates prepared with the three

catalysts above are not significantly influenced by the oil type.

Extended cracking time for sunflower oil (test No. 41) brought about no change in

parameters and yields.

GLC analysis of cracking condensates

Fig. 4 shows the chromatogram of treated condensate from the test No. 39 (rapeseed oil,

NaY, 10 %), compared to a chromatogram of fossil diesel fuel. The profiles of both

chromatograms are similar, majority of components is present in both materials but with

different contents. In principle, the present components do not have to be identical with

respect to oxygenates in the treated condensate, but they have similar boiling points.

Fig. 4 Chromatograms of treated condensate from

rapeseed oil cracking with NaY and fossil diesel

Figs. 5a-c shows the chromatograms of condensates obtained by cracking rapeseed oil in

the presence of various zeolite catalysts. The records show the presence of similar

components, small share difference is observed only in case of Na-ZSM5. The condensates

from rapeseed oil cracking in the presence of CL and NaY, respectively, are identical. The

peak corresponding to retention time around 30 min is regularly repeated in all records and

corresponds to hydrocarbon C30, or its respective oxygenates. The substance is not the

product of distillation treatment and is formed during the primary cracking process.

Fig. 5 GLC of treated condensate from rapeseed oil cracking in presence

ZSM5-Na+(a), in the presence NaY (b) and in the presence CL (c)

There are two marked peaks on the chromatograms of condensates shown in Figs. 5b, and

5c. The peak in the area with retention time of ca 20 min belongs to C18 acids in all three

forms. The peak with the retention time of ca 17 min belongs to palmitic acid. The peaks with

retention times around 10 min belong to paraffins and olefins with the number of carbons

equal to 14. Also decanoic acid (capric acid) elutes together with these hydrocarbons. Its

content is higher in comparison with acids with smaller carbon number and is comparable

with the content of palmitic acid. The second most dominant peak with the retention time

around 14 min corresponds to C17 paraffins and olefins. The condensate obtained by rapeseed

oil cracking in presence of Na-ZSM5 contains significant amount of paraffins and olefins

with the number of carbon in the backbone equal to 17 (the area with the retention time ca 14,

Fig. 5a), and a significant amount of decanoic acid (the area with the retention time ca 10,

Fig. 5a). The condensate contains much less C18 acids (the area with the retention time ca 20,

Fig.

5a) than the condensates prepared by rapeseed oil cracking in

presence of NaY or CL. The change of the catalyst does not lead to significant changes in

composition of treated condensate as the final product of cracking. Virtually no aromates are

present in the condensates. The presence of aromates in the 1H NMR spectrum is manifested

by chemical shift in the range of 6.6 to 8.3 ppm. In our experimental case, this region has no

signals whatsoever. Aromates were not identified even in condensates obtained with the

HZSM-5 catalyst. In the literature dealing with TAG cracking, this catalyst is referred to as

being clearly conducive to aromatization [11-14].

Short chain products are also formed during cracking. If the distillation treatment is

carried out in the batch, the amount of the light fraction is relatively low, around 3 to 9 wt. %.

However, if it is carried out in a film evaporator to the same flash point of the treated

condensate, the amount of light fraction represents 10 to 16 wt. %. The reactive components

present in condensate and related especially to propenal from glycerol decomposition react

together or with other reactants yielding heavier products, which remain in the condensate and

increase its yield. In film evaporator under milder conditions and shorter residence time this

process does not take place to such an extent, and the amount of the light fraction is

significantly lower. Fig. 6a and 6b show the GLC chromatograms of light fractions from one

selected test after both mentioned treatment processes.

Fig. 6a GLC of light fraction obtained by batch

distillation Fig. 6b GLC of light fraction obtained from film

evaporator

Figure 7 shows GLC chromatographs of treated condensates

obtained by cracking of rapeseed and soybean oil (Table 8, test No. 36, and 60, respectively),

jatropha oil (test No. 58) and UFO 1 (test No. 44) in the presence of NaY. The

chromatographs of the condensates show presence of the same substances albeit with slightly

different shares. The chromatographs reveal that cracking of oils produces relatively large

amounts of C10 acid

(retention time RT of about 10 min) and C18 acids in all three forms - C18:1, C18:2 and

C18:3 (RT of about 20 min). Cracking of UFO, soybean oil and jatropha oil in the presence of

NaY generates higher yields of palmitic acid C16:0 with an RT of ca 17 min. than rapeseed

oil cracking. Treated condensates further contain paraffins and olefins C6 – C30, with

paraffins and olefins C10 – C22 being the main components here. The most pronounced

peaks are those of pentadecane and heptadecane, or pentadecene and heptadecene,

respectively, with RT between 10 and 15 min.

Fig. 7 GLC of treated condensates from rapeseed, jatropha, soybean oil

and UFO cracking in the presence of NaY

Similar tendencies as those shown by GLC chromatograms of condensates obtained by

NaY-facilitated cracking are found in GLC chromatograms of treated condensates from

cracking of rapeseed oil (test No. 38), sunflower oil (test No. 42), soybean oil (test No. 61)

and UFO 1 (test No. 48) in the presence of CL (Fig. 8). Just as in the case of cracking these

oils in

the presence of NaY, here, too, the same components are present but

with a slightly altered shares. The most pronounced peaks are those of C10:0, C16:0, C18:1,

C18:2 and C18:3 acids; while among paraffin and olefin substances it is C15 and C17

hydrocarbons that have the most marked peaks. A mutual comparison of chromatograms for

condensates obtained from NaY- or CL-facilitated cracking of individual oils (Fig. 7 and 8),

too, indicates a high degree of product similarity. Our previous tests conducted with NaY and

CL catalysts have shown that it is particularly these catalysts that are suitable for TAG

cracking, generating similar yields and compositions of treated condensates irrespective of the

oil type used [15].

Fig. 8 GLC of treated condensates from rapeseed, sunflower, jatropha,

soybean oil and UFO cracking in the presence of CL

Particular attention was paid to cracking of used frying oils (UFO). This interesting

commodity is a prospective resource, being unsuitable for human diet and for making animal

feeds as well as posing problems in FAME production particularly due to the presence of

oligomers [16]. However, its use in cracking technologies entails no such limitations. UFO

may also contain animal fats (lard) with a higher percentage of saturated acyls.

Fig. 9 GLC of treated condensates from UFO 1, UFO 2

and UFO 3 cracking in the presence of CL

Fig. 9 shows GLC chromatograms of treated condensates obtained by cracking of three

UFO samples in the presence of CL (UFO 1 – test No. 48, UFO 2 – test No. 56 and UFO 3 –

test No. 57). The figure includes identification of peaks. Here again, there are identical

components with slightly differing shares. The highest peak with an RT of ca 20 min,

corresponding to C18 acids, is that of the treated condensate with the highest AV (110 mg

KOH/g) while the lowest peak corresponds to the condensate having the lowest AV (78 mg

KOH/g). In this case, the AV of feedstock UFO correlates with the AV of treated condensates

– the most acidic feedstock UFO produces the most acidic condensates and vice versa.

According to Table 8, a higher AV of condensates is related to their higher densities and

viscosities. In comparison with other oils tested, it is possible to infer a certain tendency of

UFO towards a lower AV of treated condensates.

The results show that in cracking technologies, UFO, particularly when used along with

the CL catalyst, is on a par as a material with fresh oil irrespective of the feedstock UFO

parameters.

Separated condensate removal during the cracking process

With a view to obtaining further information on the batch-mode cracking process of

natural triacylglycerols, separated removal of the liquid condensate was carried out during the

cracking process by means of gradual collection of three separate samples, one third of the

total volume each. Sunflower oil was used for the cracking; the measurement was conducted

as part of the test No. 42. The overall mass balance for the process is presented in Table 8

while material balances for individual samples collected are shown in Table 9. Each of the

samples was treated separately by standard evaporation of the light

fraction at temperatures up to 185 °C. GLC chromatograms of the treated samples are

provided in Figure 4, including the description of individual components present in the

samples.

Tab. 9 Separated removal of the condensate during the sunflower oil cracking in the presence of CL

Removal Up to

temperature

t, °C

Share from

batch, %

Share of

fraction

up to 185 °C

ρ (15 °C),

kgm-3

ν (40 °C),

mm2s

-1

AV,

mg KOH/g

1. 400 31.3 6.0 871 6.527 118

2. 440 31.3 4.4 877 7.309 140

3. 450 37.4 4.6 861 4.780 35

Shares of light fractions and structures present in GLC chromatograms in Fig 9 indicate

that batch-mode cracking is more or less a continuous process with gradual generation of

similar products. This finding is in line with the notion that the process requires contact of the

TAG molecule, or its acyl with the catalyst as well as a proper alignment of the molecule/acyl

at the catalyst’s active centers. According to the GLC shown in Figure 9, the same

components are present in all three fractions, albeit in slightly differing shares. Only the final

phase of the process is an exception, manifesting a significantly lower share of acids and an

altered shape of the chromatogram, particularly in the region of less volatile compounds,

which are present in substantially higher yields. The AV of treated products obtained from the

first two removals is high with the AV being higher for the second removal, while the AV for

the product from the third removal is significantly lower. The re-calculated AV for blended

condensates reaches a value in the usual range 94 mg KOH/g. The density and viscosity of the

first two removals is higher than those of the last removal. The re-calculated density for

blended condensates is 869 kg/m3 and viscosity 6.118 mm

2/s, which are usual values. The

higher density is related to the higher viscosity and higher acidity.

Fig. 9 GLC chromatograms for separated removal of condensates from sunflower

oil cracking conducted in the presence of CL

An analogous experiment of sunflower oil cracking in the presence of NaY (test No. 41)

was carried out, producing similar results. In this case, the treated condensate from the first

removal had a high AV of 136 mg KOH/g while the AV from the second removal was higher,

reaching 156 mg KOH/g. The third removal AV was lower (46 mg KOH/g) and the blended

condensate had a mixed AV of 113 mg KOH/g. The GLC chromatograms show the same

pattern as those of condensates prepared by way of CL.

Utilization of condensates obtained by TAG cracking

Treated products from catalytic cracking of TAG regularly exhibit increased AV, density

and viscosity in comparison with fossil diesel. Their acid value varies from 85 to 120 mg

KOH/g, density at 15 °C from 875 to 885 kg/m3 and kinematic viscosity at 40 °C from 6.5 to

9 mm2/s. The possibilities of decreasing these parameters are connected with

hydrodeoxygenation of treated cracking products or with blending of treated condensates with

fossil diesel as potential fuels for diesel engines.

Hydrodeoxygenation of treated products from cracking of TAG.

Generally, during hydrodeoxygenation of TAG the following reactions take place:

decarboxylation, decarbonylation and reduction (hydrogenation) [17]. In addition to these,

also concurrent reactions of isomerisation and alkylation of intermediate products can occur.

Decarboxylation is favored at lower hydrogen partial pressures, and higher temperatures. CO2

and CO is removed during decarboxylation and decarbonylation reactions and n-alkanes with

odd numbers of carbons (C17, C15) are formed [18]. If hydrogen partial pressure is increased,

then the reduction prevails. Such procedure yields n-alkanes with even number of carbons

(C18, C16), and with propane, water, and CO as by-products. Low concentrations of methane

and ethane were also observed. The ratio of n-alkanes with odd carbon numbers to alkanes

with even carbon numbers can be used for evaluation of the ratio of decarboxylation to

hydrodeoxygenation [18]. The situation during hydrodeoxygenation of the cracking products

is adequately influenced by the presence of fragments after cracking of TAG. Chemical

reactions will be apparently the same as above.

Fig. 10 GLC of hydrogenate from treated liquid condensate H1, of input mixture

for hydrogenation and of fossil diesel fuel

The blend of treated liquid condensates was formed by blending products of vegetable oil

cracking in the presence of CL catalysts followed by distillation treatment. The AV of the

blend was 120 mg KOH/g. The hydrodeoxygenation of this mixture was carried out at the

temperature 320 – 360 °C, pressure 3.5 – 5.5. MPa, LHSV = 1 h-1

(LHSV – liquid hourly

space velocity), H2:HC ratio = 500 – 1000 Nm3/m

3 and with commercial catalyst NiMo or

NiW. Nearly complete conversion of organic acids to paraffins was

observed. Fig. 10 shows the GLC of the input mixture, of the hydrogenate H1 and of the fossil

diesel for comparison.

After hydrogenation the AV of the liquid condensate decreased from 120 to 0.22 mg

KOH/g. The cetane index of the hydrogenate H1 exhibited a markedly higher value of 77.8

(test method according to EN ISO 4264); lubricity wear scar diameter (wsd 1.4) at 60°C was

293 μm (test method according to EN ISO 12156-1) and CFPP + 18 °C (test method

according to EN 116). The CFPP value is high; some isomerisation process would be

welcome.

0

100

200

300

400

500

0 10 20 30 40 50 60 70 80 90 100

portion of distillation/ vol. %

tem

pera

ture

/ °C

fossil diesel

hydrogenate H1

Fig. 11 The distillation curves of cracking product

after hydrodeoxygenation H1 and of fossil diesel

The pattern of the distillation curves, which are presented in Fig. 11, reflects different

characteristics of the materials used for the testing in accordance with their GLC

chromatograms (Fig. 10).

Blends of treated condensates with fossil diesel

Treated liquid condensates from the tests No. 4, No.14, No. 34, No. 40, No. 48 and the

hydrogenate H1 were mixed with non-additized winter diesel fuel (Slovnaft Bratislava,

Slovak Republic), which was modified by addition of the respective depressant (0.04 wt. %)

and detergent (0.03 wt. %) in order to improve its low temperature properties. For fossil diesel

blends with 6 – 7% of the treated condensates, or hydrogenate H1 some selected diesel fuel

parameters according to EN 590 were determined. The test results are provided in Table

10a,b. The column DF shows the parameters of the fossil diesel fuel used.

Tab. 10a Some properties of blended fossil diesel fuel (DF) with treated

condensates

DF

DF+6 % No.34 DF+6 % No.40 DF+7 % No.48

Density, 15 °C, kg m-3

831.6 834.3 835.1 833.5

Total contamination, mg kg-1

2.0 24.0 7.2 21

Kinemat. viscosity, 40 °C, mm2 s

-1 2.378 2.55 2.56 2.715

CCT, 10 %, % wt. 0.009 0.086 0.099 0.20

Flash point, PM, °C 67.9 66.9 66.9 62.8

CFPP, °C -23 -19.5 -17.5 - 15.0

Copper strip corrosion, (3h at 50 °C) 1a 1a 1a 1a

Tab. 10b The properties of the fossil diesel fuel (DF) blends with treated condensates and with hydrogenated

cracking product (H1)

DF+3 % No. 4 DF+6 % No. 4 DF+7 % No. 14 DF+7 % H1

Density, 15 °C, kg m-3

832.6 834.3 835.1 830.1

Total contamination, mg kg-1

23.2 24.0 19 2

Viscosity, 40 °C, mm2 s

-1 2.476 2.550 2.61 2.43

Carbon residue, 10 % res., wt.% 0.042 0.086 0.15 0.01

Flash point, °C 66.9 66.9 62.5 65

CFPP, °C - 19.5 - 19.5 - 20.5 - 16

Corrosion, Cu/3 h/50°C 1a 1a 1a 1a

Oxid. stability, g m-3

8.9 4.3 n.a. n.a.

The results of the tests in Tab. 10a,b show that the condensates from cracking of rapeseed

oil in the blend with fossil diesel meet in tested parameters the requirements prescribed by the

norm EN 590 for diesel fuels. Blending the treated condensate with diesel at a certain ratio

does not exceed density or viscosity of the blend as defined by the standard EN 590. The

presence of oxygenates in the fuel does not pose a significant problem. Oxygenates can even

be welcome in the fuel to a certain extent. On one hand, they entail a lower calorific value and

lower performance; but on other hand they may provide for a better quality of the combustion

process and more favorable composition of emissions. High CFPP value of the hydrogenate

H1 alone (+ 18 °C) did not significantly influence the CFPP of the blended fuel NM +7 % H1

(-16 °C).

Co-cracking

The invention concerns the method for catalytic cracking of vegetable oils and/or

animal fats as natural triacylglycerols and biomass as lignocellulose with the aim to

obtain liquid condensates usable after some treatment as the transportation fuel or

transportation fuel components based on renewable resources.

A 70-mm-diameter stainless steel batch reactor with the volume of ca 400 ml and

mechanical mixing was used for sawdust catalytic and noncatalytic cracking tests wih UFO

adding (for better heat transfer). The reactor was linked to a system of coolers with sufficient

capacity. The reactor was heated by direct fire from natural-gas rose-shaped burner. The

temperature inside the reactor was measured using two thermocouples.

After being filled with sawdust, UFO and catalyst clinoptilolit CL, the reactor was sealed

tight and heated. Usually after 10 minutes the temperature of 350 °C was reached and the

cracking process became fully developed. The cracking time ranged between 30 and 35

minutes, by which the temperature rose to 440 °C and the heating process was terminated.

The water phase constituting of the liquid condensate was separated by sedimentation from

the condensate which is brownish turbid liquid. The liquid product were analysed by

GLC chromatography and by other methods to determine their mass balance and acid value

(AV).

Tab. 11 Material balance of co-cracking

sawdust ratio of

input material

input material yield, wt.% AV,

mg KOH/g liquid

product

carbon gas water

30 wt. % 36g sawdust+84g UFO 61 17 12 10 77

50 wt. % 35g sawdust+35gUFO+7g CL 55 17 7 21 112

80 wt. % 40g sawdust+10g UFO 43 20 16 21 107

80 wt. % 40g sawdust+10gUFO+5g CL 41 20 10 29 93

100 wt. % 50g sawdust - 20 44 36 69

The table 11 shows the material balance of sawdust co-cracking. The basis for material

balance is input material (sawdust and UFO). At low sawdust portions and high UFO portion

the yield of liquid condensate is higher. Yield of carbon (rest from co-cracking) is higher than

one of

TAG cracking. Water and carbon yield depend to sawdust portion,

which was using in co-cracking process. Liquid condensate is practically not present from co-

cracking of sawdust without UFO. Acid value was measured for water-polar layer (36 wt. %).

This layer content was water (25 wt.% of input material), methanol (1.5 % of input material),

acetic acid (7 % of input material) and hydrocarbons (2.5 % wt of input material).

Fig. 12 GLC of liquid condensate from co-cracking sawdust and UFO

GLC chromatogram of liquid condensate from sawdust co-cracking is similar to GLC of

fossil diesel fuel. The components do not have to be identical, but they have similar boiling

points.The portion of sawdust significantly influences the cracking condensate yields in used

temperature regime. The chromatographs of the condensates show presence of the same

substances albeit with different shares. The GLC chromatograms from co-cracking with 30

wt.% sawdust of input material is similar to 9 wt.% sawdust of input material.

Conclusion

Liquid condensates with an 85-90% yield relative to the feedstock amount were obtained

by cracking of vegetable oils and animal fats at temperatures of 350 to 440 °C applied for the

period of 20 to 30 minutes in the presence of zeolite catalysts. The evaluation of products

involved mass balance analysis, GLC chromatography, and AV, density and viscosity

determination. From among the tested cracking catalysts high activity is exhibited by the

synthetic zeolite NaY and the natural zeolite clinoptilolite. After repeated use of the same

catalyst NaY and CL in 4 cycles a slight decrease of catalyst activity was observed. Decreased

yield of liquid condensate at decreased content of catalyst can be compensated by the

extension of the reaction time without significant changes in GLC profile. Rapeseed,

sunflower, soybean and jatropha oil as well as used frying oils were used in the tests.

Parameters and yields of treated condensates were affected by the feedstock oil type and

catalysts used (NaY and clinoptilolite) only insignificantly. UFO as a feed material matches,

in this respect, other types of fresh oils and fats. The working regime utilizing two identical

catalysts – primary one in liquid phase and a secondary one in vapor phase – has no practical

significance. However, using two different catalysts can be utilized for e.g. deacidification of

the condensate, but at expense of lower yield of treated product. The treated liquid condensate

contains especially paraffins, olefins and fatty acids, which represent the main oxygenate

component of the mixture. AV is high, between 100 and 130 mg KOH/g. Despite of this the

corrosiveness meets the requirements of the standard. The treated condensate contains no

aromatic compounds. Its GLC chromatogram is similar to GLC of fossil diesel fuel. The

components do not have to be identical, but they have similar boiling points. Viscosity and

density of treated condensates is higher than allowed by standard EN 590, what is the result of

the presence of oxygenates. Blended fuels, fossil diesel fuel with the liquid condensate in a

ratio of 3 to 7 vol. %, meet the requirements of standard EN 590. Hydrodeoxygenation of

condensates produces a mixture of alkanic hydrocarbons identical to components found in

fossil diesel. Catalytic cracking of triacylglycerols, when compared to methanol

transesterification of TAG to FAME, is simpler in terms of technology and imposes no

special requirements on the quality of feedstock oils and fats.

The first steps in direction co cracking looks very good and promising. Further tests and

analyses are needed to get satisfactory replies.

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