Study of catalytic cracking process of fuel oil to obtain components of motor fuels using aerosol nanocatalysis technology

Abstract

The article presents the results of the investigation of catalytic cracking process of crude oil in a distillation column, under atmospheric pressure, the active component of the catalyst being type Y zeolite. The process was carried out under the conditions of a new technology, called “aerosol nanocatalysis.” A schematic diagram of the laboratory installation is described and comparison of the experimental data with thermal cracking processes is made, and the expected technical and economic indicators of the new and existing industrial technologies are compared. It is shown that the use of zeolite-containing catalyst (type Y) leads to increased yield of light oil products by 48–85% by weight compared to thermal cracking. The technology of aerosol nanocatalysis is promising as it is energy and resource-saving process.

Introduction

The oil refining industry today is of great economic and strategic importance in the world. Every year the need for motor fuels and lubricants increases. In the process of oil refining a large amount of fuel oil appears—more than 50% by weight when the atmospheric oil distillation column operates. Qualified processing of fuel oil is an important scientific and practical task.

At present, there are many secondary processes for increasing the depth of oil refining. The main process is catalytic cracking. Catalytic cracking is carried out in a lift reactor, using microsphere zeolite-containing catalysts.

The next process of in-depth processing of oil tar to produce fuel oils is the visbreaking process. This process is able to save oil gas fractions and receive boiler oil, as well as components of motor fuels (Ustanovki i pechi termokrekinga, visbrekinga mazuta).

Table 1 presents the main disadvantages of catalytic cracking and visbreaking as the main processes in the processing of fuel oil.

Table 1.

List of oil refining process deficiencies (catalytic cracking and visbreaking).

Limitations	Catalytic cracking	Visbreaking
Large coking	+	+
High temperatures and pressures are used	+	+
The use of energy to recycle the catalyst between the reactor and the regenerator	+	−
Use of a large amount of expensive catalysts	+	−
Inappropriate capacity of existing plants	+	+
High feed velocity	−	+
Low depth of processing	−	+
The large size of the main equipment	+	+

These facts indicate the relevance for the need of a scientific and technical research in this area. That is, the development of a highly efficient catalytic cracking technology for crude oil feedstocks.

Aim of the study

The aim of the study is to carry out catalytic cracking of fuel oil under the conditions of aerosol nanocatalysis, whose main active component is zeolite type Y, and to evaluate the influence of the main technological parameters of this new technology of aerosol nanocatalysis—on the reaction rate and product yield.

To achieve this goal, it is necessary to solve the following tasks:

‐ consider the effect of temperature as the main control parameter on the composition of the products of this process;

‐ investigate the effect of the intensity of mechanical activation of the catalyst as a specific control parameter on the composition of products;

‐ compare the efficiency of the developed process (aerosol nanocatalysis) for processing oil with existing production processes.

Experimental results

The starting material of the catalytic conversion was the bottom residue of the atmospheric column CDU/VDU-fuel oil. The analysis of the bottom residue showed the following composition: (1) the fraction at 180–350℃ is 54% by weight, (2) the gaseous products are 5% by weight, (3) the residue is 41% by weight, and (4) the total production of light oil products is 54% by weight.

A zeolite-containing catalyst of the type Y with an initial particle size of 0.04–0.1 mm was used in the study.

In industry zeolite type Y has got its general application. It is used in the rare earth exchange form, introduced into a synthetic amorphous aluminosilicate matrix or its mixture with kaolin clay. In some cases, zeolite type Y is used in ammonium form. Therefore, a zeolite-containing catalyst of type Y can be used as a cracking catalyst (Hadzhieva, 1982); the procedure for preparation of the catalyst for heterogeneous processes is described in Patrilyak et al. (2003).

The studies were carried out on a laboratory installation that implements the principles of aerosol nanocatalysis. The plant consists of three main parts: the supply of raw materials, the reactor, the collection of reaction products with the condensation of liquid and gaseous fractions (Leonenko et al., 2014). In the experiments, the temperature of the process and the specific parameter of aerosol nanocatalysis, i.e. the mechanochemical activation frequency of the catalytic system, were varied.

Liquid cracking products were analyzed using two types of distillation:

‐ atmospheric distillation using laboratory equipment ULAB-1-42A. Fractions with a boiling point of 35–180℃ were selected;

‐ vacuum distillation at laboratory vacuum equipment according to (The USSR State Committee for Standards, 1985) in a vacuum of 2 kPa to 350℃ for better separation of the mixture.

The gaseous products were analyzed by GC-8 LHM chromatograph. The gasoline fractions were analyzed by a Crystal 5000 chromatograph.

The results of experimental studies of catalytic cracking of fuel oil using aerosol nanocatalysis technology are presented in Table 2. For correct comparison of the parameters, thermal cracking of fuel oil was first investigated. In this case, it is shown that the yield of light oil products decreases with increasing temperature. Increasing the temperature to 500℃ or higher is not advisable, since coking processes are intensified.

Table 2.

Fractional composition of the cracking products (38 cm³ reactor volume, raw material consumption 0.4 ml/min, vibration amplitude 10 mm, volume of dispersing material 20 cm³).

No.	Temperature (℃)	Frequency (Hz)	Fraction from Tboiling up to 180℃, % by weight	Fraction 180–350℃, % by weight	Gaseous products, % by weight	Fraction higher than 350℃, % by weight	Output of light oil products, % by weight	Selectivity, % by weight	The reactor capacity (kg/m3 h)
1	2	3	4	5	6	7	8	9	10
Thermal cracking in laboratory conditions
1	200	–	–	49	4	47	49	53	848
2	300		–	51	2	47	51	53	883
3	400		–	48	10	42	48	52	831
Aerosol nanocatalysis on a zeolite-containing catalyst (type Y)
4	400	3	–	62	–	38	62	63	1004
5	450		3	78	2	17	81	85	1316
6	500		–	61	4	35	61	67	987
7	550		–	57	8	35	57	66	918
8	400	4	11	73	1	15	84	85	1342
9	450		7	69	2	22	76	78	1215
10	500		10	66	1	23	76	78	1229
11	550		9	72	4	16	81	86	1311
12	400	5	8	68	1	23	76	78	1201
13	450		6	71	1	22	77	79	1264
14	500		9	76	2	13	85	88	1324
15	550		8	61	5	26	69	76	1084
16	400	6	8	66	–	24	74	75	1229
17	450		4	55	1	40	59	62	990
18	500		6	60	2	32	66	70	1089
19	550		5	50	9	36	55	65	905

The selectivity was determined as the fraction of the feed that was converted between T_boiling to 350℃. The capacity of the reactor was determined by the mass of the converted raw material per unit volume per unit time.

Comparison of own results and expected technical and economic indicators of the new technology was carried out with the existing technology of catalytic cracking of fuel oil obtained at the Cracking Fuel Installation Unit (CFIU-600) (Tekhnicheskiye kharakteristiki ustanovki UKM-600 pri pererabotke mazuta ili nefti). In this installation, the following product composition are obtained: (1) the fraction boiling from the start of T_boiling to 180℃ is 9% by weight, (2) the fraction 180–350℃ is 35% by weight, (3) gaseous products is 6% by weight, (4) the residue 50% by weight, (5) the total production of light oil products is 44% by weight, (6) selectivity of 50% by weight, and (7) the reactor capacity is 1200 kg/m³h.

The results presented in Table 2 show the advantage of the proposed technology over the existing CFIU-600 (Tekhnicheskiye kharakteristiki ustanovki UKM-600 pri pererabotke mazuta ili nefti) in that the yield of light oil products on the catalyst at a vibration frequency of 3 Hz and a temperature of 450℃ is 81% by weight. This line shows the lowest temperature of the process with the maximum yield of light oil products, but at a frequency of 4 Hz and a temperature of 400℃ it was possible to achieve 11% by weight, gasoline fraction (column 4 of Table 2) and 73% by weight of the diesel fraction (column 5 of Table 2).

A change in temperature in the range of 450–550℃ and a frequency of 3–6 Hz influences the yield of light oil products from 75 to 85% by weight, which is correspondingly higher than the yield of the experimental CFIU-600.

Figure 1 shows the output of light products as a function of temperature when the vibration frequency varies from 3 to 6 Hz. It should be noted that the vibration frequency influences the yield of light oil products. The dependence obtained can be explained from traditional technology standpoint. The reaction results in the formation of hydrocarbons of gasoline and diesel fractions, which are intermediates in the series of cracking reactions of the initial hydrocarbons. It is possible to reach the maximum yields of intermediate products in the result of optimization of the process and the hydrogen balance of the cracking reactions. Then one can observe the further depth in cracking reactions, which leads to gaseous hydrocarbons and coke. Thus, the recommended parameters for the maximum yield of the gasoline fraction are vibration frequency of 4 Hz and temperature of 400℃. The influence of vibration frequency is a specific characteristic of aerosol nanocatalysis technology.

Figure 1.

Dependence of the yield of light products on temperature with variation in the mechanochemical activation frequency.

Conclusions

It has been proved that catalytic cracking of fuel oil on a zeolite-containing catalyst (type Y) using aerosol nanocatalysis technology is promising as an energy and resource-saving process.

It has been found that the use of a zeolite-containing catalyst (type Y) leads to an increase in the yield of light oil products from 48 to 85% by weight. These results differ significantly from those obtained with thermal cracking.

The yield of light petroleum products on the existing CFIU-600 is 44% by weight, which is lower than the proposed installation using the aerosol nanocatalysis technology, which is 85% by weight.