Issue 16, 2015 - The development direction of butylene dimerization and MTBE production process in China

The development direction of butylene dimerization and MTBE production process in China

Jiangxi Changning Chemical Co.
, Ltd.
Hu Youyuan Yao Yaping

Lanzhou Petrochemical Company Research Institute Su Fangyun

The octane shortage of gasoline in China is a long-standing problem, and with the cleaning process, it will continue
in the foreseeable future.
China's large petrochemical enterprises have long focused on capacity expansion, while private enterprises have the problem of simple processing processes, which is difficult to cope with the increasingly stringent requirements
for oil quality in the cleaning process.
Using the MTBE and butene dimerization combined device, the ratio of the two can be flexibly changed, relying on the dual synergistic effect of isobutylene dimerization product and isooctene to compensate for the octane number loss
caused by hydrogenation.
In 2018, China will enforce the national V gasoline standard, and the sulfur content requirement is less than 0.
001% (≯10mg/kg), which means that FCC gasoline, which accounts for 70% of gasoline production, needs to be hydrodesulfurized, which will bring about a serious loss
of olefin saturation and octane number.
To this end, the authors propose a combined process and a subsequent overall scheme of polymerization of post-ether C4 solid phosphoric acid catalysts, which enables enterprises to use their own raw materials to produce V-standard gasoline
.
China's FCC gasoline ratio is high, so the sulfur content is high, the hydrocarbon group composition is unreasonable, the olefin content is generally above 40%, and the national V standard limits the olefin content ≤ 25%, so the high proportion of FCC gasoline has always been considered the "burden"
of China's gasoline cleaning process.
However, in the process of hydrodesulfurization of gasoline, olefins are saturated into alkanes, so that the proportion of alkanes in gasoline in China even exceeds that of the United States, and the large amount of FCC gasoline has become an advantage
.

C4 oligomerization after ether can make full use of C4 olefin resources, Jiangxi Changning Chemical Co.
, Ltd.
newly developed solid phosphorus catalyst (SPAC) butene oligomerization catalyst, enhanced oligomerization life test shows that the liquid yield reaches 1500kg/g
。 The overall scheme includes the process of oligomerization of C4 after ether to produce mixed isobutylene under SPAC catalysis, which is the same as UOP LLC's "indirect alkylation" InAlkTM process, the difference is that the oligomers of this process do not need to be hydrogenated into isooctane, but oligomerized high-octane isooctene is directly used as a gasoline blending component, and its "double efficiency" effect is used to increase the octane number
of motor gasoline.

First, the method of increasing the octane number

There are three main types of methods to increase the octane number of gasoline: First, in the production process of FCC gasoline, the octane number of gasoline is increased by adjusting raw materials, catalysts and process operating parameters; The second is to use high-octane number to blend components; The third is the use of octane number additives
.

The high-octane components of gasoline are usually as follows: catalytic reforming; Alkylated oils; nC5~nC6 alkane isomerization technology; Oxygenated compounds
.
With low investment and simple operation, the production of oxygenates is an important high-octane component of
gasoline.
The main oxygenated hydrocarbons are ethers and alcohols, in addition to MTBE, there are methanol, ethanol, tert-butanol, ethyl tert-butyl ether, methyl tert-amyl ether, diisopropyl ether, etc
.

With the introduction of the ban on MTBE regulations in various states in the United States in 2005, global MTBE production has been affected
.
However, in early 2008, the European Commission confirmed that MTBE posed no health threat, allowing MTBE to still be used as a clean gasoline component, alleviating the global trend
of shrinking MTBE capacity.

The oxygen content of national standard gasoline is limited to 2.
7%, and the amount of MTBE added to gasoline is usually 8%~15%.

China's oil refining industry is in a period of development, the growth rate of oil demand ranks first in the world, coupled with the upgrading of oil quality and emission requirements, MTBE consumption will gradually increase
.
According to the annual gasoline production of nearly 100 million tons in China, every 1 percentage point increase in the proportion of MTBE will drive the demand for MTBE by nearly 1 million tons
.

Second, the development of butylene dimer-MTBE production equipment and ether post-oligomerization device

With the cleaning process of gasoline in China, and the difficulty of investing a lot of money in petroleum processing gasoline to quickly change the situation of gasoline components, the construction of butylene dimerization and MTBE combined equipment to produce high-octane olefins and MTBE is in line with the national conditions and the actual situation of the enterprise is in line with the national conditions and the actual situation of the enterprise, but can not stop here, must further develop the post-SPAC ether C4 oligomerization process to fundamentally solve China's octane "dilemma"
.

Taking an oil refinery under expansion as an example, according to the GB17930-1999 standard, the gasoline produced by the plant had an octane number gap of 1000 per thousand tons, and according to the 2010 international fuel specifications (equivalent to GB17930-2006), there was an octane number gap of 6000 per thousand tons
.
The company expanded the MTBE plant into a butene dimer-MTBE combined unit, which will gradually increase the production of butene dimer according to the cleaning process while producing MTBE, relying on its dual synergistic effect to replenish the octane number
lost due to hydrogenation.
Table 1 shows the blending effect
of mixed isooctene in conventional gasoline.

1.
The new concept of hydrodesulfurization technology
The traditional FCC gasoline hydrodesulfurization requires "desulfurization-olefin reduction-octane number", hoping to reduce sulfur content as much as possible, moderate olefin, and reduce octane loss, which makes the catalyst and process complex, and needs to be continuously improved to adapt to clean progress
。 This overall scheme includes two processes, conventional desulfurization of FCC gasoline and butylene aggregation, the core of which is: (1) FCC gasoline takes sulfur content as the benchmark of desulfurization depth, and gradually increases the hydrogenation depth with the progress of cleaning, and the sulfur content is reduced accordingly, so that it always meets the requirements of the national standard; (2) Under the premise of complying with the olefin content limit of gasoline, replace the "original" olefin
with a lower octane number lost due to hydrosaturation with a smaller amount of butene oligoolefins with a higher octane number.
Using the "double synergistic effect" of oligomers, clean gasoline
is produced under the premise specified in the standard.

MTBE components can effectively increase the octane number of gasoline, and it has become customary
for domestic use.
Despite the potential hazards, it is difficult to find a sufficient number of alternatives at present, so it should be recognized that the replacement of MTBE should be urgently undertaken
.
The butylene dimer-MTBE combined device proposed in this scheme is timely under the current situation
.

2.
Alkylated oil production technology
There are three ways to produce alkylated oil: isobutylation of sulfuric acid or hydrofluoric acid using homogeneous catalysts, isobutane alkylation using solid acid catalysts, and "indirect alkylation"
using butylene dimer (oligomer)-hydrogenation.
At present, there are 200 sets of dimerization or stacking plants in the world to produce high-octane motor fuel, of which the total production capacity of SPAC dimerization and stacking is 8.
4 million tons, and the production capacity of the United States as a gasoline component is 2.
8 million tons, accounting for about 2%
of its total gasoline.
In 2013~2014, a large number of sulfuric acid alkylation plants were put into production in China, most of which were georefinery enterprises
.
Due to the rough technology and the lack of serious disposal of the waste liquid, it has been closed down in less than a year, which also gives the process a direction to
be promoted.
With the advancement of gasoline standard upgrades, China's alkylated oil market space will increase from 1.
85 million tons in 2013 to 7.
5 million tons in 2018, and the proportion in gasoline will increase from 2% to 6%.

Table 2 is the impact of gasoline standard upgrading on the change of gasoline composition, and Table 3 is the pull effect
of high-grade gasoline on the demand for alkylated oils.

Lanzhou Petrochemical used SPAC technology to combine Snamprogetti reactor with high-pressure water boiling and heat extraction of reboiler, and the products isooctene and 2,4,4-trimethylpentene have high selectivity and high
octane number of gasoline.
Another feature of Lanzhou Petrochemical's plant is that it can use the same reactor to produce isopropylbenzene by benzene and propylene, which is specially used by airlines as a high-grade additive component of aviation gasoline
.
Table 4 is the main quality standards
of China's automobile gasoline in recent years.

Table 1 Blending effect of mixed isooctene (butene dimer).

Dimer Linear blending Actual blending Dimer blending
amount/V% octane number Octane number Octane number
0 81 81 —10 83.
30 85.
68 127.
80
20 85.
60 89.
88
125.
40
30 87.
90 93.
60 123.
00 100
104 104 —

Table 2 Changes in demand for alkylated oils by gasoline standard upgrades %

Components Country III Country IV Country V
MTBE 13 14 14
Reformed gasoline 8 15 19 Catalytic cracking gasoline 53 50 39

Alkylated oil 2 3 6

Table 3 Pulling effect of high-grade gasoline on alkylated oil demand %

Component 90# 95# 97#
MTBE 11 15 15
reforming gasoline 0 15 35
catalytic cracking gasoline 54 53 28

Table 4 Main quality standards of China's automobile gasoline GB17930 in recent years m%

Year 1999 2004 2006 2012 2013
Sulfur content≯ 0.
080 0.
050 0.
050 0.
005 0.
001Benzene content/v%≯ 2.
5 1.
0 1.
0 1.
0 1.
0
Aromatic content/v%≯ 40 35
35 40 40 olefin content/v%≯ 35 30
25 28 25
Oxygen content≯ 2.
7 2.
7 2.
7 2.
7 2.
7
Lead reasonable≯ 0.
005 0.
005 0.
005 0.
005
Iron content≯ - - 0.
01 0.
01 0.
01
Manganese content≯ - 0.
018 0.
016 0.
008 0.
002

III.
Conclusion

(1) Butene dimerization-MTBE combined device and subsequent SPAC gathering overall process will play an important role
in China's clean gasoline production.

(2) The SPAC oligomerization process and catalyst jointly developed by Changning Chemical and Lanzhou Petrochemical have entered the industrial application stage, and in accordance with Sinopec's "Petrochemical Plant Industrial Design Package (Complete Technical Process Package)" regulations, Changning Chemical and Lanzhou Petrochemical have completed 100,000 tons of SPAC butene/propylene oligomerization/phenylpropylene alkylene process package
.