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                                                                   EXHIBIT 10.4d

                             FOURTH AMENDMENT TO THE
                            STERLING CHEMICALS, INC.
              AMENDED AND RESTATED SALARIED EMPLOYEES' PENSION PLAN

                  WHEREAS, there is reserved to the Company the right to amend
the Sterling Chemicals, Inc. Amended and Restated Salaried Employees' Pension
Plan (the "Plan"); and

                  WHEREAS, the Company deems it advisable to amend the Plan in
the manner hereafter set forth;

                  NOW, THEREFORE, the Plan is hereby amended effective as of
December 31, 1998 as follows:

                  "Notwithstanding anything in the Plan to the contrary, with
                  respect to a participant who attains age 70 1/2 after 1998
                  (other than an owner, within the meaning of IRC Section 318),
                  benefits shall not be paid or begin prior to the participant's
                  termination of employment with the Company and all members of
                  its controlled group of employers; however, in no event shall
                  the participant's accrued benefit be less than the Actuarial
                  Equivalent of the accrued benefit that would have been payable
                  as of April 1 of the year following the year the participant
                  attained age 70 1/2, had the participant terminated employment
                  on the last day of such year, adjusted for the period of
                  deferral in accordance with the applicable regulations. Except
                  to the extent required by IRC Section 401(a)(9), the Plan
                  shall not preclude such a participant from receiving benefits
                  in any of the same optional forms (except for the difference
                  in the timing of the commencement of payments) that would have
                  been available had the participant retired in the calendar
                  year in which the participant attained age 70 1/2."

                  All terms used herein that are defined in the Plan shall have
the same meanings given to such terms in the Plan, except as otherwise expressly
provided herein.

                  Except as amended and modified hereby, the Plan shall continue
in full force and effect and the Plan and this instrument shall be read, taken
and construed as one and the same instrument.

                  This instrument may be executed in several counterparts, each
of which shall be deemed an original, but all of which shall constitute but one
and the same instrument which may be evidenced by any one counterpart.

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                  IN WITNESS WHEREOF, the Company has caused this instrument to
be executed effective for all purposes as provided above.

                                    STERLING CHEMICALS, INC.

                                    By:
                                       ---------------------
                                    Name:
                                         -------------------
                                    Title:
                                          ------------------<PAGE>   1
                                                                   EXHIBIT 10.4e

                                 FIFTH AMENDMENT
                                     TO THE
                            STERLING CHEMICALS, INC.
              AMENDED AND RESTATED SALARIED EMPLOYEES' PENSION PLAN

                  WHEREAS, there is reserved to Sterling Chemicals, Inc. (the
"Company") in Section 15.1 of the Sterling Chemicals, Inc. Amended and Restated
Salaried Employees' Pension Plan (the "Plan") the right to amend the Plan;

                  NOW, THEREFORE, the Plan is hereby amended effective as of
April 1, 1999, as follows:

         1.       Section 4.3(b) is amended to read as follows:

                  Alternate Amount. The Alternate Amount shall be applicable to
                  any participant employed by the Employer on or after April 1,
                  1999 and shall be the Monthly Retirement Income equal to the
                  sum of (A) 1.2% times Average Monthly Earnings times Years of
                  Benefit Service and (B) 0.45% of Average Monthly Earnings in
                  excess of Average Covered Compensation times Years of Benefit
                  Service (not to exceed 35), times the Vested Percentage set
                  forth in Section 2.2; or

         2.       Section 4.5 is amended to read as follows:

                  Early Retirement - Early Payment. In lieu of the Monthly
                  Retirement Income payable under Section 4.4 commencing on his
                  Normal Retirement Date, a participant who retires on an Early
                  Retirement Date and does not elect to defer his Monthly
                  Retirement Income in accordance with Section 4.4 will be
                  entitled to a Monthly Retirement Income commencing on his
                  Early Retirement Date or, if he so elects, on the first day of
                  any month thereafter before his Normal Retirement Date. The
                  Monthly Retirement Income which is payable to a participant in
                  accordance with the preceding sentence will be computed by
                  determining the amount of Monthly Retirement Income which the
                  participant would have been entitled to receive under Section
                  4.4 commencing at his Normal Retirement Date and, except as
                  provided below, reducing such amount by one-fourth of one
                  percent for each complete calendar month by which the date his
                  Monthly Retirement Income payments commence precedes his
                  Normal Retirement Date. If the sum of the participant's age
                  and years of Vesting Service as of his Early Retirement Date
                  equals or exceeds 80, the reduction provided for above shall
                  apply only to the portion of such benefit calculated under
                  part (B) of the Alternate Amount formula in Section 4.3(b).

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         3.       A new 17.25 is added to Section 17 to read as follows:

                  Average Covered Compensation. Average Covered Compensation is
                  the average (without indexing) of the Social Security taxable
                  wage bases in effect for each calendar year during the 35-year
                  period ending with the last day of the calendar year in which
                  the participant attains (or will attain) Social Security
                  retirement age. In determining a participant's Average Covered
                  Compensation for a Plan Year, the Social Security taxable wage
                  base for all calendar years beginning after the first day of
                  the Plan Year is assumed to be the same as the Social Security
                  taxable wage base in effect as of the beginning of the Plan
                  Year for which the determination is being made. Average
                  Covered Compensation will be determined based on the Plan
                  Year.

                  A participant's Average Covered Compensation for a Plan Year
                  before the 35-year period ending with the last day of the
                  calendar year in which the participant attains Social Security
                  retirement age is the taxable wage base in effect as of the
                  beginning of the Plan Year. A participant's Average Covered
                  Compensation for a Plan Year after such 35-year period is the
                  participant's Average Covered Compensation for the Plan Year
                  during which the 35-year period ends.

                  All terms used herein that are defined in the Plan shall have
the same meanings given to such terms in the Plan, except as otherwise expressly
provided herein.

                  Except as amended and modified hereby, the Plan shall continue
in full force and effect and the Plan and this amendment shall be read, taken
and construed as one and the same instrument.

                  This amendment may be executed in several counterparts, each
of which shall be deemed an original, but all of which shall constitute but one
and the same instrument which may be evidenced by any one counterpart.

                  IN WITNESS WHEREOF, the Company has executed this instrument
this _______________, 1999, effective for all purposes as provided above.

                                    STERLING CHEMICALS, INC.

                                    By:
                                       ---------------------
                                    Name:
                                         -------------------
                                    Title:
                                          ------------------<PAGE>   1

                                                                   EXHIBIT 10.4f

                                 SIXTH AMENDMENT
                                     TO THE
                            STERLING CHEMICALS, INC.
              AMENDED AND RESTATED SALARIED EMPLOYEES' PENSION PLAN

                  WHEREAS, there is reserved to Sterling Chemicals, Inc. (the
"Company") in Section 15.1 of the Sterling Chemicals, Inc. Amended and Restated
Salaried Employees' Pension Plan (the "Plan") the right to amend the Plan;

                  NOW, THEREFORE, Section 2.1 of the Plan is hereby amended by
adding thereto the following:

                  For all purposes of this Plan, an employee of an Employer who
                  is a member of a collective bargaining unit shall not be an
                  eligible employee unless the bargaining agreement with the
                  Employer provides for his coverage.

                  All terms used herein that are defined in the Plan shall have
the same meanings given to such terms in the Plan, except as otherwise expressly
provided herein.

                  Except as amended and modified hereby, the Plan shall continue
in full force and effect and the Plan and this amendment shall be read, taken
and construed as one and the same instrument.

                  This amendment may be executed in several counterparts, each
of which shall be deemed an original, but all of which shall constitute but one
and the same instrument which may be evidenced by any one counterpart.

                  IN WITNESS WHEREOF, the Company has executed this instrument
this _______________, 1999.

                                    STERLING CHEMICALS, INC.

                                    By:
                                       ---------------------
                                    Name:
                                         -------------------
                                    Title:
                                          ------------------

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