CA1123774A - Catalytic conversion of heavy hydrocarbon materials - Google Patents

Abstract

Abstract A process is descried for converting heavy hydrocarbon materials, e.g. bitumen pitch, to hydrocarbon gases and liquids, carbon monoxide and hydrogen. The process com-prises spraying a preheated heavy hydrocarbon feedstock into contact with a preheated bifunctional particulate catalyst, said catalyst having (a) a pyrolysis or cracking reaction component and (b) a carbon-steam and carbon-oxygen reaction component, the spraying causing the heavy hydrocarbon material to coat the exterior surface of the catalyst particles. A pyrolysis or cracking reaction is continued whereby the heavy hydrocarbon coating is conver-ted to an adhering char and hydrocarbon vapours. The hydrocarbon vapours are separated from the char-coated catalyst particles and these particles are then contacted with steam and an oxidizing medium to convert the char to carbon monoxide, carbon dioxide and hydrogen gas. These gases are separated and the remaining catalyst is recycled.

Description

llZ3774 This invention relates to catalytic conversion of heavy hydrocarbon materials and, more particularly, catalytic conversion of such materials to hydrocarbon gases and liquids, carbon monoxide and hydrogen.
As the availability of conventional crude oil dimin-ishes, the need for alternative sources of energy will increase. Alternatives which contribute to the production of fuel oils which can be used for transportion or domestic heating will be of particular interest. One alternative would be to convert high-boiling heavy hydrocarbons, containing compounds whose normal boiling point is above 525C, into distillate products which could be used as conventional liquid fuel oils.
A typical example of the above heavy hydrocarbon material is the pitch component of heavy industrial fuel oil or bunker oil. In very simple terms heavy industrial fuel oil or bunker fuel oil may be composed of two compon-ents, hydrocarbon pitch and flux. Of the two, flux is generally considered to be the better quality component.
Usually it can be used as a feedstock ~or a conversion unit, such as a catalytic cracking unit or a hydrocracking unit. In this way it can be converted to distillate frac-tions which can be used in lower-boiling fuel oil products.
The technologies for converting materials which are equivalent to flux are well established and widely used.
In contrast, the technologies for converting hydrocarbon pitch are in a much more embryonic stage of development.
At the present time there is a considerable interest in using coal rather than bunker fuel oil in different industrial combustion units. If this trend continues to .~

23~4 develop widely, a substantial amount of hydrocarbon pitch now used in bunker fuel oil will become available for convèrsion into more desirable products.
It is also expected that a considerable amount of hydrocarbon pitch will be manufactured by processes used in refining bitumen contained in oil sand deposits. As the need for more usable liquid product intensifies, hydrocracking processes may be used instead of coking processes presently being used in commercial plants to upgrade bitumen. These hydrocracking processes produce a small yield of hydrocarbon pitch as a byproduct.
This pitch can be used in a number of different ways.
For instance, it may be blended with flux and burned as a heavy industrial fuel or bunker fuel. However, pitch by itself cannot ordinarily meet the requirements of combus-tion specifications. For example, the sulphur content is usually quite high. If large quantities of pitch are burned in one location, the amount of sulphur dioxide emitted to the atmosphere would be environmentally unaccep-table. It would, therefore, be necessary to remove thesulphur dioxide by means of stack gas scrubbing facilities and the costs of such facilities are economically prohibitive.
Alternatively, the pitch can be used as a feedstock for a gasification process. Such processes convert the pitch to carbon monoxide and hydrogen. In these processes, the sulphur is converted to hydrogen sulphide which can be removed relatively easily. These products may, if desired, be mixed with large quantities of nitrogen depending upon whether or not air or pure oxygen was used during the gas-ification process. Rowever, once again the capital cost of the gasification equipment expressed per unit of feed-stock is often substantially higher than for many types of hydrocarbon processing equipment. Accordingly, there is a considerable incentive to develop better procedures to utilize heavy hydrocarbon materials.
Summary_of the Invention The present invention relates to a process for convert-ing a heavy hydrocarbon material to hydrocarbon gases andliquids, carbon monoxide and hydrogen. The process com-prises spraying a preheated heavy hydrocarbon feedstock into contact with a preheated bifunctional particulate catalyst, said catalyst having (a) a pyrolysis or cracking reaction component and (b) a carbon-steam and carbon-oxygen reaction component, said spraying causing the heavy hydrocarbon material to coat the exterior surface of the catalyst particles, continuing a pyrolysis or cracking reaction whereby the heavy hydrocarbon coating is converted to an adhering char and hydrocarbon vapours, separating the hydro-carbon vapours from the char-coated catalyst particles, contacting the char-coated catalyst particles with steam and an oxidizing medium to convert the char to carbon monoxide, carbon dioxide and hydrogen gas, separat-ing said gases and recycling the remaining catalyst.
The process is carried out by spraying the hydrocarbon feedstock in liquid or fine-particle solid form into con-tact with the preheated catalyst, the catalyst being heated to a sufficiently high temperature that after completion ~.~ 23~74 of the endothermic pyrolysis or cracking reactions, the catalyst-char solids will be above 300C and preferably above 400C. The vapours formed from the pyrolysis or cracking may be used to provide the fluidizing gas for the catalyst in the first reaction stage.
The heavy hydrocarbon material comes into contact with the catalyst in such a way that it coats or becomes -~ attached to the exterior surface of the catalyst. As the reaction proceeds, the char forms at the physical locations o on the catalyst surface which are occupied by the heavy hydrocarbons.
The catalyst coated with the pitch and/or char pro-ceeds through the reactor and at the exit, the hydrocarbon gases and liquids (which are in the vapour phase under exit conditions) are separated from the solid catalyst and char in a separation vessel and steam stripper. The hydrocarbon vapour and liquid products can subsequently be distilled into any desired fractions.

The catalyst-char solids from the separation vessel and steam stripper are discharged into a second reactor which ~- is a gasification reactor. Steam and combustion air or oxygen are fed to the gasification reactor along with the catalyst-char solids. Ideally the steam reacts with the carbon in the char to form hydrogen and carbon monoxide.
The oxygen in the air stream or the pure oxygen stream reacts with the carbon in the char to produce carbon dioxide or carbon monoxide. The heat from the exothermic carbon-oxygen reactions is sufficient to balance the endothermic heat for the pyrolysis or cracking , 3~74 reactions, the endothermic heat for the carbon-steam reaction and the heat loss from the reaction system.
Supplementary carbon containing material may optionally be added to influence the heat balance by providing additional carbon for the carbon-oxygen reaction or the carbon-steam reaction.
A large variety of heavy hydrocarbon materials may be used as the main feedstock in the process of the invention.
For example, residuums, solid hydrocarbons, heavy crude oil o or pitch may be used as feedstock. The pitch is typically a pitch-containing component boiling above 525C and derived from materials such as petroleum crude oil, bitu-men, shale oil, coal or biomass. If solid hydrocarbons are used as feedstock, these are typically selected from coal, coke, char and biomass.
The catalyst used is preferably a multicomponent bifunctional catalyst having a pyrolysis or cracking reaction component and a carbon-steam and carbon-oxygen reaction component. The catalyst is preferably a refrac-tory base and may include as the pyrolysis or cracking component one or more of alumina, silica, titania, natural or synthetic zeolites, magnesia and hydrogen fluoride.
The carbon-steam and carbon-oxygen reaction component is - typically a group IA element, e.g. K2CO3, or a group IIA
element, e.g. CaO. It will, of course, be appreciated that other catalyst components may be used provided they are capable of enhancing a pyrolysis or cracking reaction or a carbon-steam or carbon-oxygen reaction under the process conditions stated herein.

~23~774 The pyrolysis or cracking is usually conducted at temperatures above 300C and preferably at temperatures in the range of 350 to 650C, pressures in the range of 0.1 to 15 MPa and residence times of 0.01 to 500 minutes.
The reaction of the char with steam and oxidizing medium is usually conducted at temperatures above 500C.
Preferably this reaction is conducted at temperatures in the range of 600 to 1200C, pressures in the range of 0.1 to 15 MPa and residence times in the order of 0.01 to 2000 minutes.
The pyrolysis or cracking reaction is normally conduc-ted in a fluidized bed or in a train bed transport reaction zone. The heavy hydrocarbon material is normally sprayed onto and into the catalyst bed in the form of a liquid or harshly softened solid. In the fluidized mode, the vapours formed from the pyrolysis or cracking provide the fluidiz-ing gas for the catalyst in the first reaction zone.
For a better understanding of the invention, reference is made to the accompanying drawings in which:
Figure 1 represents a typical flow sheet for commercially carrying out the process of this invention;
Figure 2 is a schematic illustration of a typical reactor vessel used in the process shown in Figure l;
Figure 3 is a plot showing weight percent residue, the reaction time with and without a catalyst;
Figure 4 is a plot showing the weight of char as a function of time under isothermal conditions; and Figure 5 is a plot of weight loss rates as a function of one/T K.
As will be seen from the flow sheet of Figure 1, a heavy hydrocarbon feedstock 12 is preheated in a heat ~ - ~
llZ3774 exchanger 13 and a furnace 14 and via line 15 is sprayed into reactor 10 containing a fluidized bed of catalyst.
In this reactor 10 the incoming spray of heavy hydrocarbon feedstock coats the exterior surface of the catalyst particles and the pyrolysis and cracking reaction continues as the material moves upwardly through the reactor whereby the heavy hydrocarbon coating is converted to an adhering char and hydrocarbon vapours.
The char-coated catalyst particles are withdrawn from o an upper region of reactor 10 via withdrawal line 16 and are charged into the second reactor 11. The hydrocarbon vapours are drawn off the top of reactor 10 via line 17 and into a cyclone separator 18 with a steam stripper 19.
Hydrocarbon vapours are withdrawn via line 21 to separator 22 with vapours being withdrawn via line 23 and a liquid stream going via line 24 to a fractionator 25. Here a bottom fraction 26, a top fraction 27 and intermediate fractions 28 are obtained.
In reactor 11 a gasification reaction takes place with steam fed in via line 29 and air or oxygen via line 30.
Within reactor 11 the steam reacts with the carbon in the char to form hydrogen and carbon monoxide, while the oxygen in the air or pure oxygen stream reacts with the carbon in the char to produce carbon dioxide or carbon monoxide. The heat from the exothermic carbon-oxygen reactions must be sufficient to balance the endothermic heat for the pyrolysis or cracking reactions, the endo-thermic heat for the carbon steam reaction and the heat loss from the reaction system. Gasification products are ~.~.23774 collected via line 32, while regenerated catalyst returns ~; to reactor 10 via recycle line 31.
Looking more specifically at a typical reactor in Figure 2, there is a main body portion 41 with a lower section 42. A riser 43 extends up through the reactor and connects to an overflow well 44 in lower section 42. The feedstock enters the reactor via feedline 45 and air or oxygen is supplied via blower 46. Water, which converts to steam, is injected via pump 47 and steam is also injected via line 48.
Positioned on the top of the regenerator 40 is a cyclone stripping vessel 49, from the top of which extends a products line 50.
Certain preferred embodiments of this invention will now be further illustrated by the following non-limitative examples.

As a feedstock there was obtained a pitch which was the portion of the liquid product boiling above 525C, obtained by thermally hydrocracking Athabasca bitumen in a pilot plant reactor. The Athabasca bitumen was obtained from Great Canadian Oil Sands Ltd., Fort McMurray, Alberta.
The properties of the pitch used are shown in Table 1 below.

:

~ ~23774 Table 1 Feedstock Properties Proximate Analysis, wt. %
Moisture Nil Ash 5.2 Volatile Matter 42.4 Fixed Carbon (by diff.) 52.4 Ultimate Analysis, wt. %
Carbon 79.6 Hydrogen ` 6.8 Sulphur 5.4 Nitrogen 1.5 - Ash 5.2 Oxygen (by diff.) 1.5 * Pentane Insolubles, wt. % 70.1 * Benzene Insolubles, wt. % 27.1 * Tetrahydrofuran Insolubles, wt. %10.4 Conradson Carbon Residue, wt. %63.5 Percent aromatic carbon 67 Ash Analysis, wt. %
Si2 43.3 A123 24.7 Fe23 11.4 3 4 0.3 Ti02 6.6 P205 0.3 CaO 2.8 Mg0 1.6 53 1.2 Na20 0.2 K20 1.7 V25 3.1 NiO 0.8 ', ~ * includes ash ~ _ g _ i Z377~

Tests were conducted with and without catalysts and in the case where no catalyst was used, the pitch sample was used in lumps and the sample sizes were in the 20 - 100 Mg range. For the catalytic experiment, the catalyst pellets (L=D=1.25 mm) were dipped in hot pitch at 150C, resulting in a thin coating of the pitch around the pellets. The catalyst/pitch weight ratio in the experiments varied from 0.5 to 4 and the catalyst used was a Y-alumina catalyst.
The samples of pitch with and without added catalyst were placed in a cylindrical quartz basket (15 x 40 mm) which was suspended from one arm of a Cahn RG electro-balance. A stream of helium or nitrogen flowed through the reactor sweeping away the products formed during the pyrolysis. The volatile products carried by the inert carrier were condensed in traps maintained at dry ice temperatures, while the non condensable gases were col-lected in sample bulbs for gas chromatographic analysis.
The reactor was surrounded by a tubular furnace which could be operated either isothermally or in a temperature programmed mode. The sample temperature was monitored using a thermocouple (Type K) positioned in close proximity to the sample basket. Both the weight of the sample and its temperature were continuously monitored and recorded as a function of time.
Several experiments were performed with heating rates of 1, 2.5, 5, 10, 20C per minute. Each experiment began at room temperature and the furnace was heated at the desired rate to a final temperature of 850C. In the majority of cases the run was terminated 10 to 15 minutes ,, after reaching the final temperature. Some experiments were also performed with non-linear heating rates. The furnace temperature was set at the desired final level and the furnace allowed to reach this temperature. The heating rate in these experiments varied from a maximum of 50C/min to essentially 0, as the final temperature was reached. In all experiments the inert carrier gas flow was maintained at 150 ml/min.
In order to obtain product samples required for all analyses, some experiments were performed with approxi-mately 5 9 of pitch. These experiments were carried out under isothermal conditions without the electrobalance attached to the sample basket.
Typical experimental data from the microbalance reactor are shown in Figure 3. The solid line was obtained without catalyst and the dotted line was obtained with a ~-A1203 catalyst and a catalyst/pitch ratio of 3.5. The furnace temperature in both of these cases increased non-linearly, reaching 500C in about 20 minutes and 850C in about 120 minutes, remaining constant thereafter. Very little reaction resulting in weight loss occurred up to approxi-mately 400C. Above 500C, the rate of weight loss was small but relatively constant. As can be seen in Figure 3, the weight-loss pattern with and without added catalyst is identical up to about 28~ solid weight loss. The catalytic effects come into force thereafter and the rate of weight loss in the presence of the catalyst is signifi-cantly higher in the case when no catalyst was present.
Values illustrating product yields and gas compositions from isothermal experiments are shown in Table 2 below.

' ,, --1 1--37~4 Product Distribution and Gas and Liquid Analysis Reaction Temperature 450C
Reaction Time 2 hours ~- Catalysed Uncatalysed catalyst =0.6 pitch Residue, wt. % 70.8 61.2 Liquid, wt. ~ 22.0 25.8 Gas, wt. %6.0 12.0 Unaccounted, wt. % 1.2 1.0 % Reacted 29.2 38.8 . _ Gas Anal~sis (Vol. %) Cl 10 12 _ _ Liquid Product Ana 1YS1S
Hydrogen, wt. % 8.84 9.18 Carbon, wt. % 84.0 84.9 % saturate carbon 62 52 % aromatic carbon 38 48 olefins trace trace ``` l~Z3774~

The yield data shown were obtained after a reaction period of two hours at a reaction temperature of 450C.
The gas and liquid yields are higher and the residue yield lower when a catalyst is present. The gas compositions with and without catalyst are fairly similar. However, analyses showed that the liquid products obtained in the catalysed experiment have a higher aromatic content than those formed in the absence of the catalyst.

Further tests were carried out using the same feed-stock as that used in Example 1. These tests were conducted to determine the advantage of using a catalyst for the carbon-steam reaction. Thus, the tests were performed both without a catalyst and with a K2CO3 catalyst. In each case the carbon-steam reaction period - was preceded by a pyrolysis or cracking reaction period.
At the conclusion of the pyrolysis or cracking reaction period, the char and catalyst were left in the reactor.
All other products were removed. Accordingly, the char was the feedstock for the carbon-steam reaction.
A semi-batch reaction system was used to study the rate of gasification. Samples of pitch mixed with powdered catalyst were placed in a cylindrical quartz basket, which was suspended from the weighing mechanism of a Cahn RG
Electrobalance. A stream of nitrogen flowed through the chamber containing the weighing mechanism and entered the " top of a hangdown tube containing the pitch sample. Nitro-- gen saturated with water vapour, the gasification reactant, flowed directly into the hangdown tube which was surrounded ~1~3774 by a tubular ~urnace. ~oth the sample weight and the temp-erature of the interior of the hangdown tube were monitored continuously.
The sample was initially heated in an atmosphere of flowing nitrogen until no further weight loss was observed.
Next, the furnace temperature was lowered to the desired value, between about 700C and 1200CC. The reaction between carbon and water vapor was then initiated by introducing a stream of nitrogen (100 ml/min) saturated with water vapor at room temperature (23 mm, 3.1 kPa). An Infrared Analyzer was used to monitor continuously the carbon monoxide level in the products of the reactiGn.
The products were also analyzed at intervals by gas chromatography. The solid char remaining after completion of the pyrolytic reactions consisted essentially of carbon with small amounts of residual hydrogen and sulphur.
The only detectable products of gasification were carbon monoxide and hydrogen. The absence of any CO2 in the product analysis suggests that the reaction of carbon with steam to form hydrogen and carbon monoxide was the major reaction occuring in the system.
Typical experimental data showing the weight of char as a function of time under isothermal conditions are given in Figure 4. The relationship between the weight of the sample and the time is linear during the initial stages of the reaction. With time, the weight slowly levels off approaching a constant value for a given temperature.
The slope of the linear segment of the curve in Figure

2 corresponds to the initial rate for the corresponding temperature. These weight-loss rates are plotted as a function of l/T K in Figure 5. The uncatalyzed reaction had a measurable rate at 800C and above with an apparent activation energy of 36 kcal/mol. Addition of 7% by weight of potassium carbonate resulted in a considerable increase in the rate of gasification and a marked decrease in apparent activation energy.
The reaction rates are compared in Table 3 below.

Catalytic Effects in the Char-Water Reaction Burn off Rate Apparent Activation at 1075C Energy (RJ/mol) (mg/g/min) ~', .
no catalyst 1.2 145.0 catalyst 4.3 140.0 -The above data shows that the reaction of pitch with steam using a K2CO3 catalyst is three times faster than - the non-catalyzed reaction.
, ,~ `

Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for converting a heavy hydrocarbon material to hydrocarbon gases and liquids, carbon monoxide and hydrogen which comprises spraying a preheated heavy hydro-carbon feedstock into contact with a preheated bifunctional particulate catalyst, said catalyst having (a) a pyrolysis or cracking reaction component and (b) a carbon-steam and carbon-oxygen reaction component, said spraying causing the heavy hydrocarbon material to coat the exterior surface of the catalyst particles, continuing a pyrolysis or cracking reaction whereby the heavy hydrocarbon coating is converted to an adhering char and hydrocarbon vapors, separating the hydrocarbon vapors from the char-coated catalyst particles, contacting the char-coated catalyst particles with steam and an oxidizing medium to convert the char to carbon monoxide, carbon dioxide and hydrogen gas, separating said gases and recycling the remaining catalyst.

2. The process according to claim 1 wherein the pyrolysis or cracking is conducted at temperatures above 300°C.

3. The process according to claim 2 wherein the pyrolysis or cracking is conducted at temperatures in the range 350 to 650°C, pressures in the range 0.1 to 15 MPa and residence times of 0.01 to 500 minutes.

4. The process according to claim 2 wherein the reaction of the char with steam and oxidizing medium is conducted at temperatures above 500°C.

5. The process according to claim 4 wherein the reaction is conducted at temperatures in the range 600 to 1200°C, pressures in the range 0.1 to 15 MPa and residence times of 0.01 to 2000 minutes.

6. The process according to claim 4 wherein the heavy hydrocarbon material is selected from residuums, solid hydrocarbons, heavy crude oil and pitch.

7. The process according to claim 6 wherein the heavy hydrocarbon material is a pitch containing component boiling above 525°C and derived from at least one of petroleum crude oil, bitumen, shale oil, coal and biomass.

8. The process according to claim 6 wherein the solid hydrocarbons are selected from coal, coke, char and biomass.

9. The process according to claim 4 wherein the catalyst is a refractory base and includes as the pyrolysis or cracking component at least one of alumina, silica, titania, natural or synthetic zeolites, magnesia and hydrogen fluoride.

10. The process according to claim 9 wherein the carbon-steam and carbon-oxygen reaction component is selected from group IA and group IIA elements.

11. The process according to claim 1 wherein the heavy hydrocarbon material is sprayed in the form of a liquid or partially softened solid.

12. The process according to claim 1 wherein the pyrolysis or cracking reaction is conducted in a fluidized bed or entrained bed transport reaction zone.

13. The process according to claim 12 wherein the carbon-steam and carbon-oxygen reactions are carried out in a fluidized bed or entrained bed transport reaction zone.

14. The process according to claim 1 wherein the oxidizing medium is air or oxygen gas.