Comparison of the hydrodenitrogenation of the petroleum model nitrogen compounds quinoline and indole

Applied Elsevier

Catalysis, 16 (1985) 39-47 Science Publishers B.V., Amsterdam

COMPARISON QUINOLINE

Ahmed

39

- Printed

OF THE HYDRODENITROGENATION

in The Netherlands

OF THE PETROLEUM

MODEL

NITROGEN

COMPOUNDS

AND INDOLE

Kadry ABOUL-GHEIT

Egyptian Present

Petroleum address:

& Engineering,

Research Visiting

Umm Al-Qura

Institute,

Nasr City, Cairo,

Professor,

Chemistry

University,

Makkah

Egypt.

Department,

Faculty

Al-Mukarramah,

Applied

Science

P.O. Box 3711, Saudi

Arabia.

(Received

25 April

1984, accepted

23 January

1985)

ABSTRACT The hydrodenitrogenation (HDN) of a basic petroleum model nitrogen compound 'quinoline' and a nonbasic one 'indole' is compared on a Co-Mo/A1203 catalyst under hydrotreating conditions. In the HDN of quinoline step 1 is found the fastest whereas step 2 is the slowest, while in indole HDN step 1 is the slowest and step 2 is the fastest. Hydrogen adsorption on the catalyst sites can not be associated with the rate-controlling process. Ni-Mo and Ni-W on alumina catalysts are found more active for the HDN of both quinoline and indole than CO-MO and Co-Ni-Mo on alumina catalysts. This activity is more significant toward indole on the first two catalysts.

INTRODUCTION The hydrotreating

process

removes

sulphur,

petroleum

fractions,

HDN being more difficult

compounds

are either

basic or non-basic;

the molecule employed

whereas

the basic model

little work dealing For individual Watson

nonbasics

with

compounds indole

and Michaelis-Menten

isms of heterogeneously

reactions

models

catalysed nitrogen

take place

model

vapour

and quinoline In

this work,

0166.9834/85/$03.30

A mixed

the HDN of quinoline

kinetic

the mechan-

model was applied

[17].

HDN a dual-site individually

of sulphur

was described

model reacted

by a

was more compatand the intermed-

compounds

CZO], H2S [20,21]

steps

in the HDN of pyridine

and others.

and indole

0 1985 Elsevier Science

[I61 reviewed

the HDN of pyridine

by Satterfield

have

however,

that both first and second

[22] on the rates of the intermediate

was investigated

[8-II];

[12-141.

on the catalyst

were

[19]. The effect

ring in

Langmuir-Hinshelwood-Hougen-

assuming

isotherm,

HDN intermediates

iate steps were modelled and water

HDN reactions.

for indole

a pyridine

from

nitrogen

[3,4]. Most HDN studies

used [15]. Laine

simultaneously

[18], whereas

ible [14]. Quinoline

were

include

ring

and metals Petroleum

[5-71 and quinoline

HDN reactions,

compounds,

Based on a Langmuir-adsorption single-site

the basics a pyrrole

pyridine

oxygen

than HDS [1,2].

has been reported

steps of complex

for the HDN of several order

include

nitrogen,

Publishers

as models B.V.

for basic and nonbasic

petroleum

nitrogen

compared.

Data of this study may be useful

TABLE

compounds,

respectively,

via their

intermediate

in selecting

steps,

commercial

has been

HDN catalysts.

1

Composition

of the prepared

catalysts.

Wt% of the active

metal

oxide

Catalyst Cobalt Co-MO-alumina

3

Co-Mo-Ni-alumina

1.5

Nickel

Tungsten

Molybdenum 10

1.5

10

Ni-MO-alumina

3

10

Ni-W-alumina

3

10

EXPERIMENTAL Catalysts Four catalysts comparing

the overall

iate steps,

molybdate

having

was used.

were

a BET surface

the requisite

impregnations. calcination

composition

given

and indole.

In preparing

of Ni and Co were the precursors

and tungstate

containing

the chemical

HDN of quinoline

a Co-Mo/Al203

the nitrates

pellets

having

the precursors

In comparison

all catalysts

of the metals,

quantities

1 were used in via the intermed-

under

whereas

investigation, ammonium

of MO and W, respectively.

_. area of 228 rn' g-l were

Each impregnation

in Table

of metallic

was followed

impregnated

precursors,

by drying

at 550°C for 4 h. The total active

metals

Gamma-alumina

with solutions

in successive

at 110°C overnight

in each catalyst

then

comprised

13 wt%.

Apparatus

and procedure

The apparatus pressure periods

and HDN procedure

autoclave

up to 9 h. The total

catalyst

have been described

was used at temperatures hydrogen

pressures

Both nitrogen

oil was spec. grade with a molecular quinoline

and indole

HDN are given

adsorption

coefficient,

for 5.5 h.

were 4.6 and 2.51 wt% respectively, compounds

weight in Table

were Merck

puriss.

of 185. The reaction

in a

grade and the

products

of

2.

AND DISCUSSION

The HDN of quinoline steps;

the hydrogen

and indole feedstocks

oil diluent.

[Ill. A high

350 and 400°C with reaction -2 and the feed to was 2 x IO7 N m

of 2 x IO6 to 2 x IO7 N m-' were used at 400°C

The quinoline paraffinic

RESULTS

pressure

ratio was 10. For determining

elsewhere

between

a hydrogenation

and indole takes step followed

place principally

by two hydrocracking

via three consecutive steps,

to produce

42 ultimately

the corresponding

hydrocarbon k

\

/

as explained

in Scheme

1.

o

/ t

\

Hydrogenation

SCHEME

and ammonia

I

Hydrocracking

Hydrocracking

1

TABLE 3 Rate constants

of the overall

steps at hydrotreating

and indole

intermediate

375

350

compound

in their

temperatures.

Temperature/"C Model

HDN of quinoline

Quinoline

Indole

400

Quinoline

Indole

Quinoline

Indole

Rate constant x to4 s-' kO

0.137

0.422

0.322

0.836

0.767

kl

fast

0.736

fast

1.118

fast

1.779

k2

0.204

1.961

0.454

3.354

0.908

5.998

k,

0.623

1.462

0.894

2.399

1.475

3.599

Table indole

3 gives the specific

rate constants

(ko), the hydrogenation

step in which ammonia experimental,

evolves

step

(k3) at the operating

using the Co-MO-alumina

For quinoline

rate equation

[ll].

k, was too fast to measure.

stationary

and k3 via the approach

by the integral concentration

of the rates

of the intermediate

and

(k2), and the last given

by applying

hand, for indole

rate equation

[14]. Scheme steps

conditions

of quasi-stationary

On the other

first order approach

HDN of quinoline

step

in the

catalyst.

HDN, k, and k2 have been determined

order

estimated

for the overall

(k,), the ring-rupture

1.386

the integral

first

concentrations HDN, k. and k, are

and k2 and k3 via the quasi-

1 presents

a qualitative

in the HDN of both nitrogen

comparison

compounds.

43

The first

step for quinoline

the slowest.

On the contrary,

step 2 is the fastest. rate.

It is evident

basic components competes

with

(propyl)

ethyl

group

indicate

to adsorb

to the following: to orient

one basic

group

decreasing

HDN, which may

and adsorb

in o-propylaniline

in o-ethylaniline, the relative

have a greater

c) the larger

basicity

alkyl

surface.

sites, whereas

component,

higher

has a greater

has to compete

on the catalyst

should

is always

that o-ethylaniline

(indole)

step is

step, whereas

and react on the catalyst

a) o-propylaniline

and one nonbasic

its second

step 3 has an intermediate

2 that k3 in the HDN of indole

than o-propylaniline

may be attributed

whereas

HDN is the slowest

In the HDN of both compounds,

from Table

than k3 in quinoline opportunity

was too fast to measure, step 1 in indole

o-ethylaniline

b) the larger

steric

hinderance

alkyl than the

group also has an effect

of o-propylaniline

greater

This

with two

on

than that of o-ethyl-

aniline. The rate data given explanation

in Table

to some erroneous

2 and depicted

conclusions

with the HDN of shale and petroleum of a shale oil, the conversion of pyrrole-types.

the pyridine-types (cf. indole). contrast

nitrogen-type

common

nitrogen

in blends

rate constants 3) indicates

with the overall

the catalyst

since

indole

besides,

the hydrogenation

hydrogen

adsorption

(hydrogenation

to play a significant

hydrogen

pressures,

Langmuir-Hinshelwood (3).

whereas

400°C

3), there

nitrogen

[24] stated

compounds

The relative

magnitude

of the

and indole

(Table

in the HDN of the two compounds. in nature,

the relative

sites and on the cracking role in the mechanism adsorption

is the slowest

The values

in a set of runs carried

of quino-

may be are basic,

step.

Hence,

for the overall step

sites of

the

HDN of

(hydrogenation

of k. and k, in the HDN of out at a wide range of total

rate constants

for a reaction

is a

+ nonbasic)

all its HDN intermediates

for 5.5 h. These

is no

that there

(basic

as well as for its first

kinetics.

isotherm

that the HDN of

that

KH, has been determined

+ hydrocracking)

have been determined

the data of

of a

HDN, hydrogen

step in this reaction

only) via Langmuir-Hinshelwood

with

step in the HDN sequence

are all basic

in case of indole

coefficient,

that in the HDN

the conversion

in the HDN of quinoline

step is not common

is nonbasic

(Table since

and total

distillates.

steps

on the hydrogenation

may not appear

critical

indole

and Kiovsky

and its HDN intermediates

line HDN. On the contrary,

reveals

HDN rates of model

of coker and thermal

of hydrogen

work

the first

step in the HDN of basic

that the slowest

adsorptivities

compounds

dealing

than the conversion

contrast

of both teams of workers,

of the intermediate

Since quinoline

indole

nitrogen

by Flinn et al [4]. Rosenheimer rate controlling

is more rapid

[23,24]

is less rapid than the HDN of the pyrrole-types

in oils will only represent

could not be compared studied

Koros et al. [23] stated

to the data of the present

the findings

1 may give a correct

by some authors

that their findings

study on model

(cf. quinoline)

According

between

oils.

of pyridine-types

They also stated

Flinn et al [4] whose

in Scheme

reported

controlled

can be related system

through

to a

equation

44

3 2 1 C 5 4 3 g 2 ;

2 1

’ ? 0‘ PRESSURE

H YDROGEiV

Nni’ x Single-sitev

1

indole

HDN and its first

k. or k, = k'KA/(l

where:

indole, always

large,

equation

it may be assumed

k. or k, = k'KA/(l

site model

+ KHpHjn

may indicate

and hydrogen,

coefficient,

respectively.

Since

p

KHpH >> KApA + KspB + KCpC + KDpD, then

.

.

.

.

compatible

.

.

with

Figure

H

.

1 shows

step. The dual-site

adsorption

preferentially

.

the data obtained

step are, respectively,

that hydrogen

.

term in (4) would

model.

of l/k' vs. pH. The calculated

does not take place

adsorption

A, B, C, D and H designate

that:

n on the adsorption

as more

its hydrogenation

during

is

to (4):

and its hydrogenation

relationship

adsorption

(3)

K is a dynamic

and subscripts ammonia

and 2 for a dual-site

is accepted reaction

rate constant,

pressure,

o-ethylaniline,

(3) reduced

The coefficient

of hydrogen

+ KA p A + KBpB + KCPC + KDPD + KHpHjn

partial

indoline,

models

step.

k' is a hypothetical

p is a component

l

vs. dual-site

FIGURE

/is

4) be equal

to 1 for a sing e-

that the dual-site for both the overall

model

gives a straight

KH for the overall

mode HDN line

HDN of indole

and

3.04 x IO2 and 3.02 x IO2 N m-'. This

during

on either

either

hydrogenation

sites on the surface

or hydrocracking of the Co-Mo-

45

\

\

\

\

\ ‘1

f-------___---_____ c

\

.

400

375

350

425

REUC7Z/O/V ~ENP~RHT&?E, FIGURE

2

Ratio of the overall

reaction

HDN rate constants

“C.

for indole

to quinoline

vs.

temperature.

n :. . :::

.. :.

Catalysts -7

/:I .I.

..

I

t

CO-MO

Co-Nab

‘.

1.2

.. . .

Ni - MO

+a ,’ . .. -. *.

j-0

O-8

Ni- W

I’. : . :. : : . . 9..

006 0.4

. . :. :

*

1.. :. :.

0.2 0

-

IV FIGURE

3

Relative

HDN activities

of the catalysts

for the HDN of quinoline

and

indole.

alumina

catalyst.

controlling

:

Moreover,

process.

hydrogen

adsorption

cannot

be associated

with

the rate

Data in Table hydrocracking requires

3 may indicate

function

a catalyst

since its slowest

with an active

is ring saturation.

Various

(in the form of oxides) support in order

to evaluate compounds.

Co-MO-alumina reaction

catalyst

temperature

genated

at 415°C

compounds,

activities

Figure

of about

of 430°C

of the catalysts

studied.

of CO-MO and Co-Ni-Mo est step in indole

followed

ammonia,

using

catalytic quinoline,

by increasing has also

slowest

bonds

is much more

which

fragment.

four catalysts.

than a Co-MO-alumina catalysts

if their

are different,

catalyst.

e.g. commercial

composition

catalysts

of relative why

also accelerates 3). This finding distillates

for the fission

It is to be noticed

chemical

and

This may explain

(Figure

bond-

and coworkers

to benzene

of petroleum

was much more active

based on their

The author

The same order

of the catalysts

1) are the

step involves

HDN is hydrocracking,

in the hydrodesulphurization

Ni-W catalyst

(Scheme

principally

3 has been obtained.

function

in the presence

for hydrogenation

A hydrocracking

passes

step in the overall

the difference than

is accelerated.

in the HDN sequence

of the ruptured

[26],

of carbon-

that comparisons

will be erroneous

[27].

REFERENCES 1 2 3 4 5 6 7 8

3

to the fact that the slow-

and Ni is more active

HDN of indole

involved

in the Figure

on all of the

pronounced

This may be attributed

in Figure

of hydrotreating sources

than that of quinoline

of Ni-Mo and Ni-W catalysts,

of the catalysts.

the hydrogenation

been observed

an unsupported

sulphur

is faster

the above-mentioned

whose

to industrial

compositions.

the HDN of aniline

given

respect

metallic

by saturation

activities

have been hydrodenitrothe HDN rates of both

due to their different

steps

rupture

high with

HDN on the

= 1) at a

to differences

the overall

of dual-functionality

1251 have studied

is relatively

and indole

quinoline

between

and quinoline

product

on the HDN of the

that quinoline

compounds

alumina steps)

confined

catalysts.

The two hydrocracking

in successive

function

HDN

step

combinations

the same gamma

(impregnation

(k. indole/ko

indole

its slowest

the metal

using

the difference

HDN is hydrogenation

than Co; consequently

having

the two model

would

In the presence

the HDN of indole

rates

whereas

since

with a high

be largely

shows that the HDN of indole catalysts

catalysts

of hydrogenation

43O"C,

and the difference

function

1 are prepared

2 indicates

such as to diminish

a catalyst

step is ring rupture,

of preparation

may have equal

(a temperature

hydrotreating)

where

in Table

the influence Since

HDN requires

hydrogenation

hydrotreating

given

and the same procedure

two model

between

that quinoline

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