Catalytic distillation desulfurization

The catalytic distillation desulfurization process developed by CDTech is significantly different from conventional hydrotreating.76 77 The most important portion of the CDTech desulfurization process is a set of two distillation columns loaded with desulfurization catalyst in a packed structure. In this process, the LCN, middle cut naphtha (MCN), and HCN are treated separately, under optimal conditions for each. The first column, called CDHydro, treats the lighter compounds of FCC gasoline and separates the heavier portion of the FCC gasoline for treatment in the second column. The second column, called CDHDS (catalytic distillation hydrodesulfurization), removes the sulfur from the heavier compounds of FCC gasoline. Figure 5.6... 

Podrebarac GG, Gildert GR. Catalytic distillation for desulfurization of full-range naphtha by thioetherification and hydrodesulfurization. WO 0266580, Catalytic Distillation Technologies, 2002. 

Catalytic distillation essentially eliminates catalyst fouling because the fractionation removes heavy coke precursors from the catalyst zone before coke can form and foul the catalyst bed. The estimated ISBL (inside battery limits) capital cost for 35,000bpd CDHydro/CDHDS unit with 92% desulfurization is US 25 million, and the direct operating cost including utilities, catalyst, hydrogen, and octane replace-... 

The first commercial and most well-known application of CD was in the production of MTBE. Besides etherification for the production of MTBE, CD could be applied in a number of processes such as alkylation, hydrogenation, isomerization, esterification, desulfurization, aldol condensation, oligomerization, hydration, hydrolysis, amination, and halogenation. Catalytic Distillation Technology (CDTECH), a partnership between ABB Lummus Global and Chemical Research and Licensing, is the leader in the development and commercialization of CD processes particularly related to the refining, petrochemical, and chemical industries. However, there are many more potential applications of CD that could be developed. 

Rock, K.L. Foley, R. Putman, H.M. Improvements in FCC gasoline desulfurization via catalytic distillation. 1998 Annual Meeting, National Petroleum Refiners Association, Mar 15-17, 1998. 

Other industrial processes that have taken advantage of the process intensification deriving from the introduction of reactive (catalytic) distillation are (i) production of high purity isobutene, for aromatic alkylation (ii) production of isopropyl alcohol by hydration of propylene (iii) selective production of ethylene glycol, which involves a great number of competitive reactions and (iv) selective desulfurization of fluid catalytic cracker gasoline fractions as well as various selective hydrogenations. Extraction distillation is also used for the production of anhydrous ethanol. 

A somewhat different type of distillation with reaction is catalytic distillation fPoherty et al.. 2008 Parkinson. 200S1. In this process bales of catalyst are stacked in the column. The bales serve both as the catalyst and as the column packing (see Chapter 101. This process was used commercially for production of methyl tert-butyl ether (MTBE) from the liquid-phase reaction of isobutylene and methanol. The heat generated by the exothermic reaction is used to supply much of the heat required for the distillation. Since MTBE use as a gasoline additive has been oudawed because of pollution problems from leaky storage tanks, these units are shut down. Other applications of catalytic distillation include desulfurization of gasoline, separation of 2-butene from a mixed C4 stream, esterification of fatty acids and etherification. 

Like the Prime G+ process concept, CDTech proposed the catalytic distillation process, in which olefin and sulfur-rich streams are separated. Those are called CDHydro and CDHDS. The C5+ gasoline fiaction from the FCC is fed into the CDHydro reactor, in which fractionation into light cut naphtha (LCN) and middle/heavy cut naphtha (MCN/HCN) occurs simultaneously with the combination reaction between mercaptans and diolefms. MCN/HCN from the bottom of CDHydro is fed into the CDHDS unit. The CDHDS unit is packed with two catalyst layers. The upper and lower catalyst layers desulfurize MCN and HCN, respectively. Because olefins are concentrated in the upper part of the CDHDS unit, selective HDS of rather heavy sulfur species can be performed in its lower part without saturation of olefins. 

Assuming that demand for petroleum continues to increase at a rate of 1.2% per annum to 2010,37 and that all gasoline and diesel produced by U.S. refineries will have a sulfur content of less than 30 ppm, desulfurization of gasoline and diesel to these low levels will require extensive hydrotreating of both catalytic cracker feed and product of distillate. 

Many processes in a refinery use steam as a stripping medium in distillation and as a diluent to reduce the hydrocarbon partial pressure in catalytic or thermal cracking [37]. The steam is eventually condensed as a liquid effluent commonly referred to as sour or foul water. The two most prevalent pollutants found in sour water are H2S and NH3 resulting from the destmction of organic sulfur and nitrogen compounds during desulfurization, denitrification, and hydrotreating. Phenols and cyanides also may be present in sour water. 

Gas oils Utilized as straight-run distillate after desulfurization. Lighter atmospheric and vacuum gas oils are often hydrocracked or catalytically cracked to produce gasoline, jet, and diesel fuel fractions heavy vacuum gas oils can be used to produce lubestocks or as fluid catalytic cracking (FCC) feedstock... 

The high-boiling distillates, such as the atmospheric and vacuum gas oils, are not usually produced as a refinery product but merely serve as feedstocks to other processes for conversion to lower-boiling materials. For example, gas oils can be desulfurized to remove more than 80% of the sulfur originally in the gas oil with some conversion of the gas oil to lower-boiling materials (Table 6-11). The treated gas oil (which has a reduced carbon residue as well as lower sulfur and nitrogen contents relative to the untreated material) can then be converted to lower-boiling products in, say, a catalytic cracker where an improved catalyst life and volumetric yield may be noted. 

Cracking, desulfurization, and demetallization reactions take place via thermal and catalytic reactions. In the upper section of the reactor, vapor is disengaged from the slurry, and hydrogen and other gases are removed in a high-pressure separator. The liquid condensed from the overhead vapor is distilled and then flows out to the secondary treatment facilities. 

Gulf HDS process a fixed-bed process for the catalytic hydrocracking of heavy stocks to lower-boiling distillates with accompanying desulfurization. 

Ultralining a fixed-bed catalytic hydrogenation process to desulfurize naphthas and upgrade distillates by essentially removing sulfur, nitrogen, and other materials. 

Unifining a fixed-bed catalytic process to desulfurize and hydrogenate refinery distillates. 

The H-Coal process is a development of Hydrocarbon Research Inc. (HRI). It converts coal by catalytic hydrogenation to substitutes for petroleum ranging from a low sulfur fuel oil to an all distillate synthetic crude, the latter representing a potential source of raw material for the petrochemical industry. The process is a related application to HRI s H-Oil process which is used commercially for the desulfurization of residual oils from crude oil refining. 

Catalytic reforming Naphtha hydrotreating Distillate hydrotreating Gas oil desulfurization Resid desulfurization Resid hydrocracking... 

Hydrotreating A catalytic reaction of distillate fractions with hydrogen at elevated pressures that is primarily used to desulfurize the feed. The products/are hydrogen sulfide and hydrocarbon organic nitrogen compounds react to form ammonia and hydrocarbon, while some hydrogen cyanide may be made from heavier fractions. 

Description Gas feedstock is compressed (if required), desulfurized (1) and sent to the optional saturator (2) where some process steam is generated. The saturator is used where maximum water recovery is important. Further process steam is added, and the mixture is preheated and sent to the pre-reformer (3), using the Catalytic-Rich-Gas process. Steam raised in the methanol converter is added, along with available C02, and the partially reformed mixture is preheated and sent to the reformer (4). High-grade heat in the reformed gas is recovered as high-pressure steam (5), boiler feedwater preheat, and for reboil heat in the distillation system (6). The high-pressure steam is used to drive the main compressors in the plant. 

OATS [Olefinic Alkylation of Thiophenic Sulfur] A gasoline desulfurization process. Thiophenes and mercaptans are catalytically reacted with olefins to produce higher-boiling compounds that can more easily be removed by distillation prior to hydrodesulfurization. This minimizes hydrogen usage. The process uses a solid acid catalyst in a liquid-phase, fixed bed reactor. Developed by BPAmoco in 2000 and tested in Bavaria and Texas. First used commercially at the Bayernoil refinery, Neustadt, in 2001. The process won a European Environment Award in 2002. 

---