Plant and process for producing fatty alcohol

Abstract

A plant and a process for carrying out the continuous production of fatty alcohol from fatty acid ester by catalytic trickle-bed hydrogenation, comprising shaft reactors each containing at least one catalyst fixed bed, which are connected with each other via pipe conduits such that they can be traversed by the educt/product mixture one after the other, in freely selectable order.

Claims

1. A process for the continuous production of a fatty alcohol from a fatty acid ester by catalytic trickle-bed hydrogenation, the process comprising the steps of: a) mixing the fatty acid ester with hydrogen to produce an educt mixture, wherein the hydrogen comprises fresh hydrogen and recirculated hydrogen, wherein the educt mixture is at a pressure in the range from 50 to 250 bar; b) heating the educt mixture to a temperature in the range from 150 to 250 C.; c) passing the educt mixture through a first shaft reactor and then through a second shaft reactor, wherein each of the first shaft reactor and the second shaft reactor contain at least one catalyst fixed bed designed as trickle bed, wherein the educt mixture is converted, within a traveling reaction zone, into a liquid product mixture which contains fatty alcohol, hydrogen and, depending on the fatty acid ester used, also further alcohols wherein each catalyst fixed bed has a bed length; d) measuring a temperature profile along the bed length of each catalyst fixed bed; e) determining the location of the traveling reaction zone within the catalyst fixed beds by the measured temperature profile from step d); f) cooling the liquid product mixture; g) separating the hydrogen from the liquid product mixture to form a hydrogen stream and a liquid product stream containing fatty alcohol; h) using at least a portion of the hydrogen stream to provide the recirculated hydrogen of step a); and i) discharging the liquid product stream containing fatty alcohol from the process for the further treatment; wherein, upon a determination that the traveling reaction zone has entered the catalyst fixed bed of the second shaft reactor and has progressed to such an extent that an inactive zone, which is of sufficient length to provide a protection zone for trapping catalyst poisons, has formed upstream the traveling reaction zone in the catalyst fixed bed of the second shaft reactor, the process further comprises the steps of: i. switching the flow of the educt mixture to first flow into the second shaft reactor without first flowing through the first shaft reactor, thereby taking the first shaft reactor out of operation; ii. replacing the catalyst fixed bed of the first shaft reactor with fresh catalyst; and iii. fluidly connecting the first shaft reactor downstream of the second shaft reactor, thereby placing the first shaft reactor back in operation.

2. The process according to claim 1, wherein the fatty acid ester is a wax ester, and before process step b) the fatty acid ester is passed through a depressurizing device, thereby reducing the content of free fatty acids and other compounds of higher volatility.

3. The process according to claim 2, wherein the depressurizing device is operated at pressures between 1 and 1000 mbar.

4. The process according to claim 2, wherein the depressurizing device is operated at pressures between 10 and 700 mbar.

5. The process according to claim 1, wherein step b) is at a pressure between 75 to 100 bar.

6. The process according to claim 1, wherein the mixture is heated to a temperature in step c) between 180 to 250 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, advantages and possible applications of the invention can also be taken from the following description of exemplary embodiments and numerical examples as well as the drawing. All features described and/or illustrated form the subject-matter of the invention per se or in any combination, independent of their inclusion in the claims or their back-reference.

(2) The FIGURE shows a schematic diagram of the connection of two catalyst-filled fixed-bed reactors of a plant according to an embodiment of the invention by means of pipe conduits.

DETAILED DESCRIPTION OF THE INVENTION

(3) The interconnection according to the invention will be explained below with reference to FIG. 1.

(4) The reactors A and B are connected with each other via the illustrated pipe conduit system. Pipe fittings, such as for example valves, are not shown. Through supply conduit 1, the educt mixture consisting of a liquid fatty acid ester and hydrogen is introduced into the system and into one of the reactors with a pressure in the range from 75 to 100 bar and a temperature of e.g. 180 C. The reactors each contain two catalyst fixed beds, K1 to K4. On trickling through the catalyst fixed beds, the educt mixture is converted into a product mixture consisting of fatty alcohol and hydrogen. The hydrogenation proceeds exothermally and leads to a temperature rise in the mixture and in the reaction zone of the catalyst bed. Temperature measuring devices, TI, installed in the reactors reveal the course of the temperature along the length of the fixed bed and hence the traveling of the reaction zone through the fixed bed. In the production mode of the plant the mixture is passed on through the transfer conduit 2 into the respective downstream reactor. The product mixture leaves the system for the further treatment in the plant via conduit 4. In the case of the catalyst exchange in one of the reactors, the conduit system also allows to guide the flow of the mixture such that it only flows through one of the reactors and thereafter is guided directly to the further treatment.

(5) Via conduits 5, 6 and 7 quench hydrogen can be introduced into the educt/product mixture.

(6) The following Example 1 shows how the quantity of circulated hydrogen can be reduced by using the quench hydrogen:

Example 1

(7) In the hydrogenation of a C.sub.16/C.sub.18 wax ester fraction a reactor inlet temperature of 180 C. and a maximum heating of 30 C. must be maintained. For this purpose, the fatty acid ester (1a) is mixed with fresh hydrogen (1b) and cycle hydrogen (1c) and introduced into the hydrogenation reactor with four catalyst beds. The product (4) chiefly consists of fatty alcohol and hydrogen. The results were determined by means of process simulation.

(8) Without quench gas cooling, a cycle hydrogen quantity of 6834 kg per 25000 kg/h of wax ester is supplied to the reactor, whereas with quench gas cooling the cycle hydrogen quantity (H.sub.2,cycle+sum H.sub.2,quench) can be reduced to 3621 kg/h per 25000 kg/h of wax ester.

(9) TABLE-US-00001 Without quench gas With quench gas cooling cooling Mass Mass flow Temperature flow Temperature Stream Name kg/h C. kg/h C. 1a Fatty acid 25000 232 25000 232 ester 1b H.sub.2, fresh 225 60 225 60 1c H.sub.2, cycle 6834 151 2676 105 4 Product 32059 210 28846 210 5 H.sub.2, quench 1 718 75 6 H.sub.2, quench 2 189 75 7 H.sub.2, quench 3 38 75 Sum H.sub.2 6834 3621 (Streams 2 + 3 + 5 + 6 + 7) TI1 Bed 1 head 180 180 TI2 Bed 1 bottom 200 210 TI3 Bed 2 head 200 199 TI4 Bed 2 bottom 208 210 TI5 Bed 3 head 208 207 TI6 Bed 3 bottom 208 210 TI7 Bed 4 head 210 209 TI8 Bed 4 bottom 210 210

(10) Example 2 shows the dependence of the content of hydrocarbons in the product on the reaction temperature at which the hydrogenation proceeds:

Example 2

(11) In the hydrogenation of a wax ester the content of hydrocarbons in dependence on the reaction temperature was determined experimentally (Table 1). Up to a reactor temperature of 200 C. the hydrocarbon content lies below 0.05 wt-%. Above a temperature of 200 C. the hydrocarbon content rises distinctly.

(12) TABLE-US-00002 TABLE 1 Reaction temperature Hydrocarbon content in the product [ C.] [wt-%] 170 0 180 0.01 190 0.02 200 0.03 210 0.16 215 0.26 220 0.54

INDUSTRIAL APPLICABILITY

(13) The invention provides a plant which can continue to produce without interruption also during the exchange of the catalyst, and which provides for optimizing the utilization of the catalyst. The invention therefore is industrially applicable.

(14) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(15) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(16) Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

(17) Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

(18) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(19) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(20) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

LIST OF REFERENCE NUMERALS

(21) 1a supply conduit for fatty acid ester 1b inlet for fresh hydrogen 1c inlet for recirculated hydrogen 2 transfer conduit 3 vacant 4 discharge conduit for product mixture 5 quench hydrogen supply 6 quench hydrogen supply 7 quench hydrogen supply A reactor B reactor K1 catalyst fixed bed K2 catalyst fixed bed K3 catalyst fixed bed K4 catalyst fixed bed TI1 to TI8 temperature measuring device