Technical Advantage
——Innovative DYC Catalyst Technology Platform
The main reaction of RFCC is cracking reaction of high-molecular-weight hydrocarbons through carbenium ion intermediate on solid acid site. For FCC catalyst, pore architecture is as important as acidity. We believe that FCC catalyst design of today should transform from “Formula Design” to “Structure-Oriented Design”, achieving effective synergy between pore architecture and acidity to meet requirements from FCC processing and feedstock. The pore architecture of FCC catalysts includes pore distributions and pore structure (open type, close type), active sites species (acid sites and other functional centers) and its structure (uniform distribution, core-shell structure); The acidity matching of catalyst includes B acidity and L acidity matching, strong acidity and weak acidity matching, acid site number matching)
The Researcher of Duo You Technology developed rich mesoporous Y molecular sieve with low coke selectivity and fibrous high activity alumina preparative technique, and both technologies have applied for the national invention patents. The SEM photos of low coke Y molecular sieve, TEM photos and XRD patterns of the fibrous high activity alumina are shown below.
Figure 1 SEM Photo of Low Coke Y Molecular Sieve
Figure 2 TEM Photo of Fibrous High Activity Alumina
At the same time, starting from catalytic cracking mechanism, following the "structure - oriented" idea and on the basis of low coke Y molecular sieve and fibrous high activity alumina, the company's technical staff adopted high solid content of catalyst technology to develop innovative Duo You catalyst – “DYC series FCC catalyst” technology platform. The catalyst prepared by technology platform not only improves accessibility of catalyst active sites, and solves the difficult problem of high coke yield during catalytic cracking process from the reaction mechanism, but also has excellent resistance to heavy metals. The SEM Morphology and pore size distributions of DYC catalyst are listed below.
From Figure 3 we can see that catalysts prepared on DYC Technology Platform showed very good sphericity and open pore architecture (left photo)，compared to the SEM photo of common cracking catalyst, clear difference can be found.. With the same amplification factor, zeolite particles locating on microsphere and porous wall with multilevel pore-size distribution (middle photo) can be clearly seen on surface of catalyst prepared by DYC Technology Platform. However, the surface of catalyst prepared by traditional technology is platy due to binding agent. Neither zeolite nor pore structure is obvious.
SEM photo of DYC particles（50X） SEM photo of DYC single particle(8000X) particle (15000X)
Figure 3 SEM Photos of DYC Catalyst and Common Cracking Catalyst
As zeolites in catalyst prepared by DYC Technology Platform cover directly on surface of porous wall (middle photo), macromolecule of heavy oil can diffuse readily to acid sites of zeolites, so that the accessibility of active sites is enhanced. Meanwhile, diffusive separation of cracking product has been improved, activity and selectivity of catalyst are also significantly increased.
Figure 4 pore size distributions of fibrous activity alumina
Figure 4b pore size distributions of DYC catalyst
In Figure 4, we can see that the pores of fibrous activity alumina are mainly concentrated in the range of 10-20 nm, and the fibrous activity alumina is a large aperture alumina material. When the alumina was added into the catalyst, both of the proportion of 10 ~ 60 nm mesopore and the proportion of large pore and super pore of catalyst were improved significantly, and the structure of pore was open distribution. So we can say that DYC catalysts resolved the problem of accessibility of catalyst active sites in structural design.
Therefore, FCC catalysts produced on DYC technology platform have such characteristics:
（1） Open and Graded distribution of pore structure
The open pores shorten the raw oil and product molecular diffusion path in catalyst, reduce the ratio of thermal pyrolysis of raw oil, limit the deep cracking of product, improve the selectivity of products and coke was improved, make contribution to the stripper steam treatment agent of molecular adsorption stripping effect, and reduce the catalyst-to-oil coke.
(2) Crystal molecular sieve with special distribution
The content of molecular sieve in DYC catalyst is high, and the exposure proportion of molecular sieve on surface and in pore passage of catalyst microspheres is higher than that of conventional FCC catalyst. The high catalytic activity and electivity of surface acid site of molecular sieve are suitable for promoting catalytic cracking of heavy oil macromolecule including some convertible carbon residues and green coke precursors in raw materials, to reduce the proportion of nonselective reactions, thus conducive both to improving heavy oil conversion ability and to decreasing production of catalytic coke and additional carbon.
(3) Strong basic nitrogen and heavy metal pollution resistance
The content of Y molecular sieve is increased relatively in the formula of DYC catalyst, which raises the quantity of acid sites of the catalyst, greatly strengthening its resistance to basic nitrogen; meanwhile, fibrous high-activity aluminium oxide is also included in the formula of DYC catalyst, and the aluminium oxide is of comparatively strong heavy metal trapping and containing capacity, which reduces nonselective reactions caused by heavy metal, and significantly enhances catalyst’s resistance to heavy metal pollution.
(4) High light oil yield
DYC catalyst has large pore and ultra-large pore at certain quantity, to facilitate the entry of heavy oil macromolecule to the pore passage of catalyst for catalytic reaction, thus reducing the yield of slurry oil and promoting that of light oil. Meanwhile, the matrix material of fibrous high-activity aluminium oxide is matched with various modified molecular sieves, which modulates the proportion of different reactions during catalytic cracking to adapt to cracking of different kinds of raw oils, thus decreasing green coke greatly and increasing the yield of light oil; particularly, the high-content Y molecular sieve prompts conversion of diesel oil molecules to gasoline molecules to promote the yield of gasoline.
Catalyst of Duo You Technology is tailor-made to satisfy operating requirements of users based on device features of each refiner, feedstock properties, product distribution and target products.
