over time, refiners tended to increase the level of rare earths in their catalyst.
Technical. Note. Fluid Catalytic Cracking (FCC). Catalyst Optimization to Cope.
Fluid Catalytic Cracking (FCC) Catalyst Optimization to Cope with High Rare Earth Oxide Price Environment Introduction
Technical Note
The use of rare earths in FCC catalysts was driven by the need for more active and hydrothermally stable products with better yield performance. Rare earth oxides (REO) achieved these goals by enhancing catalytic activity and preventing loss of acid sites during normal unit operation. To address the specific needs of each FCC unit, catalyst manufacturers formulate catalysts with various rare earth levels that allow for optimal unit performance. The level of REO in a specific catalyst formulation is determined by operational severity and product objectives. As the need for increased amounts of gasoline grew over time, refiners tended to increase the level of rare earths in their catalyst
formulation to meet their profitability targets. Rare earth gradually increased over the years and at the end of 2010, the average was 3%, with several refineries running in excess of the average.
Figure 1 shows 2010 historical data for E-cat samples analyzed by BASF for rare earth oxide. These reflect all the samples that were received by BASF in the fourth quarter of 2010 before the REO price spike occurred. Sample count refers to the number of E-cat samples analyzed by the BASF laboratory. The blue trend line shows the cumulative percentage of samples at or below a specific REO content. Although operational demands have not changed in the industry; current rare earth market conditions have put pressure on catalyst manufacturers as well as refiners to reassess the role of RE in the FCC industry. When looking at the catalytic options, it is critical to look at the overall value and not just the cost of RE. BASF has actively helped its customers analyze their operations and determine when a drop in RE levels is beneficial. Nineteen out of sixty BASF customers that have looked at a low REO option have switched. BASF’s products deliver the highest activity in the market and therefore are well suited for low REO operation. As will be discussed in this article, the cost benefits and possible performance deficits of this option need to be clearly understood before making a change.
REO Supply-Demand Balance The supply-demand balance of the global rare earth market became disconnected when China, which produces 95% of the world’s supply of rare earths, severely cut its export quotas in July 2010. China is not expected to change its position, despite the World Trade Organization’s warning that reluctance to share its rare earth supplies constitutes a violation of the global trade rules. Export quotas for the second half of 2011, recently released, indicate a significant increase over the 2010 numbers. On close examination, the new quotas reveal that nothing has changed as the new figures merely include ferrous alloys. These were not part of the quota in 2010. Market expectations are that price volatility will continue until new suppliers enter the market and re-establish the supplydemand balance. In a recent research note issued by Goldman Sachs1, prices are likely to rise in the short term, over the next 18 months, and then soften in the 2013 to 2015 period. This softening of rare earth prices will most likely be due to additional capacity coming online from non-Chinese sources that are expected to significantly shift the supply picture in the coming years.
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
30 25 20 15 10 5 0 0.5
1
1.5
2
2.5
3
3.5
REO wt% Figure 1: Distribution of REO in FCC catalyst samples
2
4
5
Cumulative Percent of Samples at REO wt% Level
Number of Sample Counts
45 40 35
During the interim period, until rare earth prices once again normalize, the refining industry is looking for ways to address the increase in catalyst costs within its current budgetary constraints. Instinctively, the drive is to opt for lower rare earth catalyst formulations to offset the costs of the raw material. While this action can have an immediate and successful impact on the operating budget, it may not be the best decision for the refinery. Understanding the constraints of a specific FCC unit is critical to making the optimal economic decision. BASF has proactively worked with its customers to examine low rare earth catalytic options that fit the needs of the specific users.
The decision to change catalyst or reformulate catalyst is not a trivial one. Simply reducing rare earth levels of the catalyst without a comprehensive study can result in severe yield penalties and possibly force the refinery to cut feed rates to the unit. All such consequences are economically prohibitive. Helping customers evaluate the effect of rare earth level on key catalytic variables reduces the uncertainty of the change and facilitates the decision to move to a reformulation of their FCC catalyst, when appropriate. The specifics of this change in formulation and the impact of REO level on conversion, as well as the effect of fresh catalyst surface area and addition rate, will be examined in this paper.
Technological Differences
How Rare Earth Affects FCC Catalyst Performance
While all catalyst companies can offer catalyst products with lower levels of REO, BASF is the only company that can offer its customers an option of increasing activity, and thereby maintaining conversion at constant catalyst addition, due to an increase in zeolite content as represented by active and selective total surface area. BASF employs in-situ technology, which is particularly well suited for this application. The in-situ process begins with a catalyst-sized microsphere. The ensuing step consists of growing the zeolite crystal within the microsphere. The zeolite in-situ process serves two functions; it provides the active and selective area, as well as providing the strength imparted to the microsphere. This technology is distinct from the incorporated technology practiced by all other catalyst suppliers. With incorporated technology, a single particle is formed consisting of an admixture of clay, zeolite, and binder. As this technology is already optimized, addition of substantial amounts of zeolite will require reducing either the clay or binder. The incorporated catalyst technique is inherently limited to an upper level of zeolite content and cannot increase surface area without seriously compromising the strength to withstand breakage in the FCC unit.
When considering a move to reduce REO component in the catalyst, it is critical to grasp the performance shifts and economic impact of such a change. The economic impact comprises two aspects. It is a function of total catalyst cost and the value created from a given catalyst formulation. Reducing the rare earth level will have an immediate cost saving, but this calculation alone will not give the true profit generation picture if the margin benefits from the yield slate are not included. To illustrate the impact of such change on key catalytic performance indicators, a proprietary FCC simulation model was used to study the effects of REO level, catalyst addition rate, and fresh surface area for FCC units operating with the following feedstocks. ydrotreated Vacuum Gas Oil (VGO) - Refinery A H Standard VGO - Refinery B n Moderate Resid - Refinery C n Heavy Resid - Refinery D n n
3
Our choice in selecting the above feed types is to provide an analysis that covers the whole range of feed diets (types) used in FCC operations. The base case for all cases was 3% REO in the catalyst. As seen from Figure 1, this was the average level of rare earths used in 155 FCC units. For each operation, the REO level was changed to model the following scenarios: n
n
n
Impact of REO level on conversion, at constant catalyst addition rates and unit conditions Impact of fresh catalyst addition rate, to restore base case conversion at constant unit conditions ffect of increasing fresh catalyst E surface area, at constant catalyst addition rates and unit conditions
This approach was adopted due to the fact that the first negative impact of the REO reduction effect is a decrease in activity of the catalyst. The second and third bullet points were methods to recover the loss in activity through either increased catalyst additions or through choosing catalyst with a higher intrinsic activity that is achieved through increased surface area. The base case for the feed types and E-cat properties are given in Table 1. Operating conditions of the four scenarios are provided in Table 2.
Refinery
A
B
C
D
API
26.3
22
22.1
20.1
Concarbon wt%
0.3
0.3
0.9
4.5
Sulfur wt%
0.5
0.7
0.5
0.4
Basic N2 wt%
0.03
0.05
0.04
0.04
Distillation % 650 °F -
15
20
7
4
% 1000 °F +
