Development of a Solid Catalyst Alkylation Process Using Supercritical Fluid Regeneration

FEW4340-68

Program
This project was funded through DOE's Natural Gas and Oil Technology Partnership Program. The program establishes alliances that combine the resources and experience of the nation's petroleum industry with the capabilities of the national laboratories to expedite research, development, and demonstration of advanced technologies for improved natural gas and oil recovery.

Project Goal
The goal was to develop an economical solid catalyst alkylation process via supercritical fluid (SCF) regeneration.

Performers
Idaho National Engineering and Environmental Laboratory (INEEL)
Idaho Falls, ID

Phillips Petroleum Company (ConocoPhillips)
Houston, TX

Project Results
During experiments, alkene conversion was maintained above 90% and product quality remained relatively constant during the entire run. Catalyst activity, based on total product yield, was maintained above 90% of its initial level for 132 hours, representing a 15-fold increase in catalyst longevity. These preliminary results are highly encouraging, and it is expected that significant improvements in catalyst life and product yield and quality can be achieved as the process is improved and optimized for commercial feeds.

Benefits
This project developed an economical solid catalyst alkylation process via SCF regeneration. Experimental data were obtained to determine the maximum number of regenerations, minimum pressure and energy requirements, minimum SCF usage requirements, potential for SCF recycle and reuse, and reactor design requirements for continuous reaction and regeneration.

Background
Alkylation is used by the petroleum refining industry to produce a low-vapor-pressure, high-octane gasoline blendstock. Alkylate is an ultraclean-fuel component and the cleanest gasoline blend stream produced in a refinery. Current industrial alkylation processes catalyze the reaction with concentrated liquid mineral acids, either hydrofluoric (HF) or sulfuric (H2SO4) acids, which pose serious safety and environmental risks. These risks have led Federal and local governments to cease issuing permits for construction of new HF alkylation plants.

Production of this ultraclean fuel is thus at risk and its growth severely limited unless a replacement process can be developed. In order for alkylate to be used as a high-volume, ultraclean fuel, an alternative safe and environmentally acceptable alkylation process is required. Solid acid catalysts could replace liquid acids and eliminate many safety and environmental concerns, but they deactivate rapidly due to deposition and buildup of heavy hydrocarbons on the catalyst surface. Typical catalyst regeneration processes are oxidative and destroy significant levels of acidic alkylation catalyst activity. This results in high levels of catalyst consumption, making solid catalytic alkylation economically and environmentally unacceptable. This project is designed to develop an economical solid catalyst alkylation process via SCF regeneration. Experimental data are to be obtained to determine the maximum number of regenerations, minimum pressure and energy requirements, minimum SCF usage requirements, potential for SCF recycle and reuse, and reactor design requirements for continuous reaction and regeneration.

Project Summary
An automated bench scale reaction/regeneration system was reassembled. The system is based on the use of two reactors that are alternately switched between the reaction mix feed stream and the SCF regeneration stream. In this configuration, one reactor is always catalyzing the alkylation reaction, while the other is being regenerated by the SCF. The system can accommodate up to 10 grams (g) of catalyst per reactor. The system uses automated high-pressure pumps, switching valves, and temperature and pressure controllers. A computer-based data acquisition and control system is used to automatically switch the reactors from reaction to regeneration conditions. To date, the system has provided unattended experimental runs in excess of 200 hours.

Experimental results using a model alkene feed (2-butene) have demonstrated that a USY zeolite catalyst could be maintained at greater than 90% of initial activity for at least 210 hours. This represented a 20-fold increase in catalyst longevity. This result was obtained at an olefin weight hour space velocity (OWHSV) of 0.2 g olefin/g catalyst/hour and an isoparaffin to olefin (iP:O) ratio of 20:1. The 210 hour experiment duration does not represent a limit for the SCF regeneration technology since the experiment was prematurely terminated due to infrastructure difficulties. Under the set of conditions explored, each batch of catalyst was run and regenerated 35 times.

The SCF regeneration technology was tested using a commercial alkylation feed stream obtained from Phillips Petroleum Company (now ConocoPhillips). The feed stream had minimal pretreatment. The olefin stream had been caustic-washed and dried to remove mercaptans. The olefin stream contained a mix of propenes (28 wt %), butenes (68 wt %) and pentenes (4 wt %). Impurities known to deactivate solid acid catalysts included butadiene (2,000 ppm), acetone (140 ppm), and sulfur (16 ppm). Experiments were run at an OWHSV of 0.2 g olefin/g catalyst/hour and a molar iP:O ratio of 19:1. Without SCF regeneration, alkene conversion dropped below 90% after only 9 hours online. Product quality declined rapidly after 10 hours, with cracking (C5) and oligomerization (C9+) products becoming very significant. The SCF regeneration technology was explored using the commercial alkylation feed, without optimization of regeneration conditions. The reaction/regeneration experiment was run for about 200 hours.

Current Status (October 2005)
This project is complete.

Project Start: April 12, 2001
Project End: April 11, 2004

Anticipated DOE Contribution: $330,000
Performer Contribution: $0

Contact Information
NETL - Kathleen Stirling (kathy.stirling@netl.doe.gov or 918/ 699-2008)
INL - Daniel Ginosar (Daniel.Ginosar@inl.gov or 208-526-9049)

Schematic of the automated experimental system for continuous reaction and regeneration.

Graph of Butene Conversion

Graph of Activity Recovery

Continuous solid catalyst alkylation reaction/regeneration experiment results showing (top) butene conversion and catalyst activity recovery.