1. A process for the preparation of 1,4-cyclohexanedimethanol, comprising:
(i). contacting bis(4-methylcyclohexyl)methyl)terephthalate with hydrogen in a first hydrogenation zone in the presence of a catalyst effective for hydrogenation of an aromatic ring to produce a liquid effluent comprising bis(4-methylcyclohexyl)methyl)cyclohexane-1,4-dicarboxylate;
(ii) contacting the effluent from the first hydrogenation zone with hydrogen in the presence of an ester hydrogenation catalyst in a second hydrogenation zone to produce a hydrogenation product comprising 1,4-cyclohexanedimethanol, 4,4\u2032-oxybis(methylene)bis(methylcyclohexane), and (4-methylcyclohexyl)methanol;
(iii). distilling the hydrogenation product from step (ii) to recover a distillate comprising a majority of the (4-methylcyclohexyl)methanol in the hydrogenation product and a distillation bottoms comprising a majority of the 1,4-cyclohexanedimethanol, and 4,4\u2032-oxybis(methylene)bis(methylcyclohexane) in the hydrogenation product;
(iv). allowing the distillation bottoms to form a lower layer comprising a majority of the 1,4-cyclohexanedimethanol in the distillation bottoms and a upper layer comprising a majority of the 4,4\u2032-oxybis(methylene)-bis(methylcyclohexane) in the distillation bottoms; and
(v). separating the upper and lower layers of step (iv) and recovering the 1,4-cyclohexanedimethanol from the lower layer by distillation.
2. The process according to claim 1, wherein the bis(4-methylcyclohexyl)methyl)terephthalate is produced by esterification of terephthalic acid with (4-methylcyclohexyl)methanol.
3. The process according to claim 1, wherein the bis(4-methylcyclohexyl)methyl)terephthalate in step (i) is contacted with hydrogen at a temperature of about 150 to about 350\xb0 C. and a pressure of about 50 to about 400 bars gauge and the catalyst effective for hydrogenation of an aromatic ring comprises palladium, platinum, nickel, ruthenium or combinations thereof deposited on a catalyst support material.
4. The process according to claim 1, wherein the bis(4-methylcyclohexyl)methyl)terephthalate in step (i) is contacted with hydrogen at a temperature of about 180 to about 250\xb0 C. and a pressure of about 50 to about 170 bars gauge, the catalyst comprises palladium, ruthenium, or combinations thereof, and the catalyst support material comprises alumina, silica-alumina, titania, zirconia, chromium oxides, graphite, silicon carbide, or combinations thereof.
5. The process according to claim 1, wherein the catalyst in step (i) comprises palladium on alumina.
6. The process according to claim 1, wherein the effluent from the first hydrogenation zone is contacted with hydrogen in step (ii) at a temperature of 180 to about 300\xb0 C. at a pressure of about 40 to about 400 bars gauge and the ester hydrogenation catalyst comprises at least one Group VIII metal, a copper-containing catalyst, or a combination thereof.
7. The process according to claim 1, wherein the ester hydrogenation catalyst of step (ii) comprises copper chromite, copper oxide, Raney nickel, Raney cobalt, or combinations thereof, and is optionally promoted with zinc, barium, calcium, manganese, magnesium, nickel, ruthenium, lanthanum, titanium, or a combination thereof.
8. The process according to claim 1, wherein the lower layer comprises at least 50 weight percent of 1,4-cyclohexanedimethanol, based on the total weight of the lower layer.
9. The process according to claim 1, wherein the upper layer comprises at least 70 weight percent of 4,4\u2032-oxybis(methylene)bis(methylcyclohexane) based on the total weight of the upper layer.
10. The process according to claim 1, wherein the (4-methylcyclohexyl)methanol recovered in step (iii) is passed to a process for the preparation of bis(4-methylcyclohexyl)methyl)terephthalate by esterification of terephthalic acid.
11. A process for the preparation of 1,4-cyclohexanedimethanol, comprising:
(i). feeding an esterification reaction product, comprising bis(4-methylcyclohexyl)methyl)terephthalate and (4-methylcyclohexyl)methanol, with hydrogen to a first hydrogenation zone comprising a fixed bed of a palladium on alumina catalyst at a temperature of about 180\xb0 C. to about 250\xb0 C. and a pressure of about 50 to about 170 bars gauge to produce a liquid effluent comprising bis(4-methylcyclohexyl)methyl cyclohexane-1,4-dicarboxylate;
(ii). feeding the liquid effluent from step (i) with hydrogen to a second hydrogenation zone comprising a fixed bed comprising a copper chromite catalyst at a temperature of about 180 to about 300\xb0 C. and a pressure of about 100 to about 400 bars gauge to produce a hydrogenation product comprising 1,4-cyclohexanedimethanol, 4-methylcyclohexanemethanol, and 4,4\u2032-oxybis(methylene)bis(methylcyclohexane);
(iii). distilling the hydrogenation product from step (ii) to recover a distillate comprising a majority of the (4-methylcyclohexyl)methanol in the hydrogenation product and a distillation bottoms comprising a majority of the 1,4-cyclohexanedimethanol and 4,4\u2032-oxybis(methylene)bis(methylcyclohexane) in the hydrogenation product;
(iv). allowing the distillation bottoms to form a lower layer comprising a majority of the 1,4-cyclohexanedimethanol in the distillation bottoms and an upper layer comprising a majority of the 4,4\u2032-oxybis(methylene)-bis(methylcyclohexane) in the distillation bottoms;
(v). separating the upper and lower layers of step (iv) and recovering the 1,4-cyclohexanedimethanol from the lower layer by distillation; and
(vi). passing the (4-methylcyclohexyl)methanol from the distillate in step (iii) to an esterification process to produce bis(4-methylcyclohexyl)methyl)terephthalate.
12. The process according to claim 11, wherein the lower layer comprises at least 50 weight percent of 1,4-cyclohexanedimethanol, based on the total weight of the lower layer.
13. The process according to claim 11, wherein the lower layer comprises 5 weight percent or less of 1,4-cyclohexanedimethanol, based on the total weight of the lower layer.
14. The process according to claim 11, wherein the upper layer comprises at least 70 weight percent of 4,4\u2032-oxybis(methylene)bis(methylcyclohexane) based on the total weight of the upper layer.
15. The process according to claim 11, wherein the upper layer comprises at least 80 weight percent of 4,4\u2032-oxybis(methylene)bis(methylcyclohexane) based on the total weight of the upper layer.
16. The process according to claim 11, wherein the (4-methylcyclohexyl)methanol recovered in step (iii) is passed to a process for the preparation of bis(4-methylcyclohexyl)methyl)terephthalate by esterification of terephthalic acid.
17. The process according to claim 16, wherein the amount of (4-methylcyclohexyl-methy)methanol recovered in step (iii) is sufficient to prepare the entire esterification reaction product of step (i).
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Apparatus for inspecting a substrate, the apparatus comprising:
an X-Y stage that supports a substrate to be inspected and is operable to move a substrate supported thereby in X and Y directions; and
an imaging system including a plurality of beam columns operable to irradiate regions of a substrate supported by the X-Y stage with beams of energy, respectively, discrete from one another,
wherein respective ones of the beam columns are movable relative to others of the electron beam columns.
2. Apparatus as claimed in claim 1, wherein each of the beam columns includes a source of electrons, and a deflector operative to deflect a beam of the electrons in a scanning direction
3. Apparatus as claimed in claim 1, wherein the imaging system comprises a plurality of supports independently movable relative to each other in at least one of the X and Y directions, and at least one of the beam columns is mounted to each of the supports so as to be movable therewith.
4. Apparatus as claimed in claim 3, wherein the supports are a plurality of rails, respectively, the rails are supported so as to be movable independently of one another in at least one of the X and Y directions, and a plurality of the beam columns are mounted to each of the rails so as to move therewith.
5. Apparatus as claimed in claim 4, wherein each of the beam columns includes a source of electrons, and a deflector operative to deflect a beam of the electrons in a scanning direction parallel to said one of the directions.
6. Apparatus as claimed in claim 3, wherein the supports include stages each supported so as to be movable independently of one another in the X and Y directions, and at least one of the beam columns is mounted to each of the stages so as to move therewith.
7. Apparatus as claimed in claim 6, wherein only one of the beam columns is mounted to each of the stages.
8. Apparatus as claimed in claim 6, wherein each of the beam columns includes a source of electrons, and a deflector operative to deflect a beam of the electrons in a scanning direction parallel to one of the X and Y directions.
9. Apparatus as claimed in claim 1, wherein the imaging system further comprises:
detectors that detect emissions from the regions of a substrate irradiated with the beams and produces from the detected emissions data representative of images of the regions of the substrate; and
a processor operatively connected to each of the detectors so as to receive from the detectors the data representative of images of the regions of the substrate,
wherein the processor has a memory configured to store the data representative of images of (n+1) of the regions of the substrate, wherein n is an integer equal to at least 2, whereby data representative of the captured images of at least three of the regions of the substrate are stored, and
the processor is configured to average (m\u22121) of the captured images to create an average image of all but one of the captured images,
subtract the average image from the said one of the captured images to produce data representative of a difference image, and
analyze pixels of the difference image.
10. A method of inspecting a substrate, the method comprising:
capturing images of (m+1) regions of the substrate, wherein n is an integer equal to at least 2, whereby the images of at least three of the regions of the substrate are captured;
averaging (m\u22121) of the captured images to create an average image of all but one of the captured images;
subtracting the average image from said one image to produce a difference image; and
analyzing pixels of the difference image.